Petrova Task Force 2026

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Twitter read-along
Due to the length of this post, we are doing a read-along of shorter segments on my Twitter page. If you are just here to read the whole post, read on! If you want to follow the read-along, we are on Pt. 6: Extras, Rejections, and Plot Implications.
Pt. 0: The Premise of Petrova ‘26
Pt. 1: Discovery of Astrophage
Pt. 2: Design of the Hail Mary — Habitation Section
Pt. 3: Design of the Hail Mary — Power, Propulsion, Centrifuge
Pt. 4: Design of the Hail Mary — Beetles and Other Systems
Pt. 5: Assembly of the Hail Mary
Pt. 6: Extras, Rejections, and Plot Implications

The Premise of Petrova ‘26

Petrova Task Force 2026 is one part Project Hail Mary fan-fiction, one part alternate history, and one part spacecraft architecture design, born out of love for the Andy Weir novel and subsequent movie adaptation. The book takes place on an undefined timeline likely starting approximately around the time of its writing and release, possibly 2019 or thereabouts. The movie is also ambiguous in its timeline, but follows many of the cues of the book.

Petrova ‘26 was born out of the simple thought experiment: “What if Project Hail Mary happened now, in 2026?”

This is not a reimagining of the plot of Project Hail Mary, but a reimagining of the in-universe titular project itself. If the Hail Mary was designed in 2026, what would it look like? Who would manufacture it? What would the assembly process be?

The design of the Petrova ‘26 Hail Mary was born from first principles and grounded in the capabilities of the real world aerospace industry in 2026. For parts of the design where we had creative freedom, the book and movie designs served as inspiration. My collaborator on this project, Chance Wen (@wenchance), designed and modelled the Hail Mary, while I focused on research, technical solutions, and this write-up. Many fantastic renders of the Petrova ‘26 Hail Mary are available on Chance’s Twitter and ko-fi.

Timeline of Petrova Line and Astrophage Discovery

August 2024: Petrova publicizes her discovery of the Petrova line visible between the Sun and Venus.
September 2024: Ground based observatories confirm the existence of the Petrova line exclusively around the 25.984 micron mid-infrared(A lower frequency of light below visible light) wavelength.
October 2024: Astronomers are stumped by the Petrova line. Space telescopes, including Hubble, are tasked with observations, and continue to find no sign of the Petrova line in any other wavelengths.
November 6, 2024: Parker Solar Probe performs its final Venus gravity assist. Lacking an infrared imager, it makes no detection of the Petrova line with any instruments. This non-detection reduces the likelihood of charged particles or electric fields contributing to the phenomena.
November 2024: BepiColombo passes underneath the Petrova line en route to Mercury. The MERTIS instrument is able to resolve Petrova frequency light.
November 2024: NASA issues a request for information regarding possible missions to the Petrova line.
December 31, 2024: A Joint US/EU press conference is held announcing the apparent dimming of the sun, and corresponding brightening of the Petrova line. Understanding the Petrova line is now the top scientific priority of NASA and ESA(European Space Agency).
January 6, 2025: The new president of the United States nominates a NASA administrator, and urges the Senate to confirm the nomination within days. An executive order is signed, directing the NASA administrator to reconfigure the Planetary Defense Coordination Office and tasking NASA with developing a mission in conjunction with the Department of State Office of Space Affairs.
January 10, 2025: The new NASA administrator is confirmed by the Senate. The administrator learns of an in-development concept for a rapid Venus flyby mission, and greenlights it on the spot, ordering work to begin immediately, even before international agreements are signed.
January 2025: NASA, ESA, and JAXA(Japanese Aerospace Exploration Agency) enter into a partnership to send a mission to the Petrova line. The mission is called ArcLight(Joint NASA/ESA/JAXA Petrova line sampler probe, assembled from SLS, ESM, and MMX.). Having just missed a Venus launch window, the focus becomes on how to get to Venus and back without waiting a year and a half for the next planetary alignment.

ArcLight Probe

Given the urgency with which national leadership pushes for an understanding of the Petrova line and its correlation with the Sun’s brightness, NASA quickly settles on the need for a rapid sample retrieval mission. Without a convenient planetary alignment, the mission needs an unprecedented amount of delta-v(Change in velocity. A measure of the cumulative accelleration needed for in-space maneuvers.), and without time for a blank slate development, the mission needs to use existing hardware, modified for the purpose. Three components stand out as best suited for the task.

A spacecraft bus and return sample container are non-negotiable mission features, and only one spacecraft in the world is fit for the purpose: JAXA(Japanese Aerospace Exploration Agency)’s Martian Moons eXploration mission (MMX(Martian Moons eXploration, a JAXA mission to return a sample of Phobos)), in final assembly ahead of a planned 2026 launch to Mars to land on, sample, and return a piece of Phobos. MMX is an interplanetary spacecraft with a lot of delta-v and a sample return capsule. JAXA and the Japanese government are quick to agree to convert MMX into a Petrova line sampler, as they had already been considering possible missions to Venus to study the Petrova line.

Even with all of MMX’s performance, the planned timing of ArcLight—launching in the summer of 2025—means an additional and substantial transfer stage is needed for the trip to Venus. NASA engineers recognize only one already-manufactured vehicle suited for the task, the European Service Module (ESM(European Service Module, the power and propulsion portion of the Orion spacecraft.)) that powers the Orion spacecraft. ESM has substantial storable propellant and power-generation, and is a proven deep space vehicle having flown in lunar orbit on Artemis I. Major modifications are needed to make it suitable for a Venus mission, but ESA(European Space Agency) is eager to convert an ESM for the job, and the Artemis III ESM is rapidly shipped from KSC back to Airbus’s factory in Bremen, Germany for major modifications.

The last major component is a rocket. Falcon Heavy is the first consideration, but its fairing is too small to fit an ESM, and the performance restricts ArcLight to much later launch windows in 2026. NASA instead decides to work out a way to launch ArcLight on the Space Launch System (SLS(Space Launch System, NASA’s super heavy rocket for Artemis)), since it is already designed to launch the ESM (normally carrying Orion) and it is the most performant operational rocket in the world. An SLS is already being prepared for an April 2026 launch of Artemis II, but ArcLight is planned to launch over half a year before then. The NASA administrator pushes for SLS to be fully stacked, excluding ESM and MMX, before the middle of summer, for a rollout and fueling test at KSC’s LC-39B.

MMX modifications include the removal of the landing legs, landing propulsion, and several scientific instruments, as well as the rapid completion of all core systems before JAXA ships it to NASA JPL(Jet Propulsion Laboratory, NASA center focused on planetary exploration spacecraft) for further modifications. JPL meanwhile is tasked with rapidly developing a sample system based on the Stardust spacecraft NASA flew in the 1990’s. APL(Johns Hopkins University Applied Physics Laboratory, developer/operator of several NASA missions) develops a key component of the sample system, the Rapid Analysis Suite (RAS(Rapid Analysis Suite, onboard sample observations on ArcLight)), which is effectively a microscope that can observe the collected sample prior to encapsulation in MMX’s return capsule. MMX is also modified to allow communication between the ESM and MMX, to allow primary command and control of ArcLight through MMX.

Airbus and ESA perform a quick gutting of the Artemis III ESM, which is renamed the European Transfer Module (ETM(European Transfer Module, modified ESM used for ArcLight)). Life support systems, including water and oxygen tanks, are removed, along with two of the solar array wings. The thermal management system is modified, since it no longer needs to manage Orion, but it does need to manage the higher solar intensity at Venus.

While NASA teams work to rapidly assemble and test SLS, new components need to be created to support replacing Orion with MMX. Contractors begin work on a payload adapter to take the place of the Orion cradle. Most crucially, MMX needs to be placed inside a fairing of some kind. The Orion Launch Abort System (LAS) serves as a complete fairing, but it isn’t tall enough to fit MMX inside it, so an in-production LAS is modified to extend the fairing envelope.

Continued Timeline

June 2025: SLS(Space Launch System, NASA’s super heavy rocket for Artemis) conducts multiple WDR(Wet Dress Rehearsal, a flight-like fuelling and countdown test of a rocket)s without the ETM(European Transfer Module, modified ESM used for ArcLight) or ArcLight(Joint NASA/ESA/JAXA Petrova line sampler probe, assembled from SLS, ESM, and MMX.) integrated.
July 2025: ArcLight arrives at KSC for integration on SLS.
July 17, 2025: ArcLight launches.
October 2025: The sun’s rate of dimming is modelled as exponential, according to a peer reviewed study released by an international team of researchers. If unchecked, this will cause a civilization ending ice age within half a century.
December 02, 2025: ArcLight flies past Venus through the Petrova line. Low quality IR(infrared: A lower frequency of light below visible light) detections confirm the shape of the line, despite major IR interference from the warm spacecraft itself. The sampler is brought to the RAS(Rapid Analysis Suite, onboard sample observations on ArcLight) ahead of encapsulation. Transmitted images depict what appear to be black dots behaving like microscopic life, shocking the world.
December 2025: The United Nations convenes a secret vote, and establishes the Petrova Task Force. The task force is granted sweeping powers and near blanket immunity by nearly every member nation, with the sole goal of finding a solution to the Petrova problem.
January 2026: The US rescinds the Wolf Amendment under the recommendation of the Petrova Task Force, enabling full data sharing and collaboration with China on aerospace matters. The ArcLight team shares data and plans with a Chinese team also developing a Petrova line sampler mission.
April 2026: Russia and Ukraine agree to a temporary ceasefire on the grounds of global emergency.
May 2026: A detailed analysis of luminosity records from amateur and professional telescopes indicates that several other nearby stars are apparently infected by the Petrova dots. Data on Tau Ceti is inconclusive, but it appears unaffected. All major ground and space telescopes that are fit for the purpose are tasked with observing Tau Ceti and its neighbours.
June 2026: Tau Ceti is confirmed to be the only nearby star not actively dimming. There are many competing theories on why Tau Ceti doesn’t have a Petrova dot problem. One theory is that the Tau Ceti system has no planets with CO2(Carbon Dioxide) atmospheres, an unsettling possibility.
June 2026: The prospect of a potential interstellar mission becomes evident to the Petrova Task Force, although how to perform one is unknown. Space agencies are asked for all possible proposals. Since several proposals involve on-orbit assembly, it is decided to begin planning for that possibility. NASA and Roscosmos(Russian state aerospace corporation (space agency)) begin working on ideas for using the ISS(International Space Station) as a construction yard.
July 2026: The Large Hadron Collider at CERN postpones planned upgrades as it concludes Run 3. The collider is kept in an operational state for potential experiments on Petrova dots.
July 23, 2026: China launches Hongxianwen-1(Chinese Petrova line sampler probe. Roughly translates to ‘asking the red thread of fate’), their own Petrova sample retrieval mission.
August 2026: Ahead of the launch of Crew 13, NASA approaches SpaceX to increase the cadence of Dragon missions to the ISS to one every two months, alternating between crew and cargo, with two month overlap between all crew missions. This would bring the average USOS(United States Orbital Segment, portion of the ISS built by the USA, Europe, Japan, and Canada) crew complement up from just over 4 to a little under 7. Crew 14 is brought forward to December 2026 as the beginning of the new cadence. ISS crews begin to decommission experiment racks.
September 2026: The Nancy Grace Roman Space Telescope launches.
September 2026: The ArcLight probe flies by Earth, and the return capsule lands in the Australian Outback. It is immediately brought to a waiting sample analysis lab, where it is determined that the Petrova dots are alive, can be killed, are opaque to all light until killed, move by emitting Petrova light, and maintain exactly 94.6°C body temperature. Further experimentation reveals the newly named Astrophage to be breedable and incredibly energy dense, perfect rocket fuel. Project Hail Mary is born.

“Well my friends, it sure has been a wild and interesting week of news and discoveries! It’s only been a couple weeks since ArcLight’s reentry capsule landed in the Australian Outback with the space dot samples from Venus. Scientists from all around the world got straight to work and my-oh-my, were we surprised by what they found! Alien life is confirmed, and it’s weirder than anyone ever imagined. But that’s somehow not all that we have for you this week. We are about to see a complete transformation of the ISS for a project that no one expected, constructing a crewed interstellar spaceship?!”

Marcus House — October 2026

November 25, 2026: Hongxianwen-1(Chinese Petrova line sampler probe. Roughly translates to ‘asking the red thread of fate’) enters an elliptical orbit of Venus.
December, 2026: First light imagery from Roman(RST: Nancy Grace Roman Space Telescope, NASA visible light telescope launched in mid-2026)’s coronagraph indicates a potential CO2 atmosphere around an exoplanet orbiting Tau Ceti, which should therefore support Astrophage breeding, but seemingly isn’t. The Hail Mary design is baselined for a one-way trip to the Tau Ceti system.
January 4, 2027: Hongxianwen-1 departs Venus.
January 2027: The Petrova Task Force tasks the IAEA(International Atomic Energy Agency, UN agency overseeing international nuclear energy, including safety) and industry in developing large scale facilities and standards for Astrophage production.
February 2027: LHC(Large Hadron Collidor, powerful particle accelerator in Europe.) experiments on Astrophage begin, starting with bombardments by high energy protons, and continuing with heavier ions, including lead ions. Experiments show Astrophage to be remarkably resilient to high energy particles, making it a perfect radiation shield for space travel.
May 2027: Initial construction begins on prototype large scale Astrophage breeders in the Gobi desert.
November 11, 2027: The Hongxianwen-1 Astrophage sample lands in the Gobi desert with several grams of Astrophage.

The Hail Mary

“Okay, what do you have for us?”

“Well, we talked with the tether teams about the pivoting mechanism for the hab section. We just don’t think it is technically feasible given the design requirements, at least to a point where we would have a meaningful margin of confidence.”

“That just leaves the drop-hab design, no? Any further developments on it?”

“Yes, revision 3 is the most workable and we’ve refined our models to better match mission criteria. Here are the current renders if you want a look.”

“It says we’re on rev. 3.5, is that what we are going with?”

“Yes, the official position of the General Program Architecture Committee—and I agree with them on this—is that the best option moving forward will be revision 3.5 of the ship. We should be able to meet all design requirements, unless anyone else has any showstoppers.”

Preliminary Design Update Meeting — December 2026

The Design

The Hail Mary is a first of its kind crewed interstellar spaceship, powered to relativistic speed using Astrophage fueled engines. The architecture reflects several competing requirements. The journey is long, so the habitation volume needs to be large enough to accommodate a crew and all their supplies, with plenty of floor space for lab equipment and basic living. Significant portions of the mission will be under thrust—including transits around the Tau Ceti system—so the habitation space needs to have a ‘down’, and ideally be horizontally oriented for easy traversal. To use the lab equipment while not under thrust, the habitation section needs to be able to be spun to provide centripetal gravity, which introduces another possible ‘down’. Relativistic travel through the interstellar medium results in loose gas particles becoming high energy radiation, so the ship needs forward shielding capable of protecting the ship and crew from both high energy particles and interstellar dust. Given that the size, and thus the mass, of the forward shield depends on the cross-sectional area of the ship, a long skinny ship is the easiest to protect.

The preferred horizontal hab orientation seems at odds with the preferred skinniness of the ship for relativistic travel. The force of thrust compared to the force of the habitation centrifuge creates geometry problems when trying to keep ‘down’ the same. The compromised design of the Hail Mary is a tri-wing underslung habitation section nestled between three fuel and engine stacks, with a relativistic shield at the front. The underslung hab can be ‘lowered’ out of the bottom of the ship on tethers for centripetal gravity, keeping the force vector aligned with the floor of the hab and eliminating any need for a complex hab rotation mechanism.

Specifications

Length:

With IS(Interstellar Shield): 86.3m

Without IS: 81.8m

Width:

IS Max Width: 45.6m

IS Min Width: 39.4m

Fuel Tanks:

Diameter: 3.8m

Length: 9.6m

Hab Modules:

Diameter: 4.5m

Length: 5m (short), 10m (long)

Mass:

Dry Mass: 556t

Astrophage Mass: 11,820t

Wet Mass: 12,376t

Mass Ratio: 21:1

Acceleration:

Standard 1g

Tau Ceti Travel:

Earth Time: 14 years 120 days

Ship Time: 7 years 65 days

Distance: 11.91 light years

Coast Distance: 77%

Coast Duration: 4.17 years

Acceleration Duration: 3.01 years

Peak Lorentz Factor: 2.4

Peak Velocity: 91% light speed

Components and Subsystems

Habitation Modules

ESA(European Space Agency)/JAXA(Japanese Aerospace Exploration Agency)/Thales Alenia Space/MHI(Mitsubishi Heavy Industries)/Northrop Grumman

The pressurized modules of the Hail Mary are heavily based on the US Orbital Segment (USOS(United States Orbital Segment, portion of the ISS built by the USA, Europe, Japan, and Canada)) of the ISS(International Space Station), and have the same diameter and general construction. However, the Hail Mary is designed for extended periods of artificial gravity primarily across the diameter of the modules, so the entire habitation section is rigidized with external bracing to reduce the loads on the pressure hulls and berthing ports.

The pressurized volume is made up of eight modules connected with common berthing mechanisms (CBM(Common berthing mechanism, a module attachment standard used on the ISS)), the same type of port used on the USOS and on Cygnus and HTV-X cargo vehicles. The Hail Mary’s CBMs are built by MHI and Northrop Grumman.

The habitation modules are arranged with two modules stacked vertically in the center, the Core Node and Airlock modules, and three horizontal wings made up of two modules each. ESA and JAXA, with prime contractors Thales Alenia Space and MHI, lead the development of all pressurized modules except the Airlock.

Airlock

NASA/Boeing/Voyager

The bottom of the habitation section is the airlock module. Derived from the Quest airlock on the ISS, the lower tunnel serves as the only means of accessing the exterior of the ship for an EVA(Extravehicular Activity, a spacewalk), and can hold two suited crewmembers while pressurizing or depressurizing. The airlock also serves as the docking location during assembly, and features a detachable docking tunnel that is removed prior to the start of the interstellar voyage.

The larger upper portion of the airlock module serves as the suit up area, and is part of the main pressurized volume of the Hail Mary. EVA suits, tethers, and tools are stored there.

Additionally, the airlock features a removable trash chute that can be stored in the suit up area. Mechanical linkages allow the operation of the exterior airlock hatch from the suit-up area, after which point the trash chute can be activated, which jettisons a standardized trash bag out the airlock based on Voyager’s experience with the Nanoracks Bishop airlock on the ISS. The airlock and trash disposal can be operated while the Hail Mary is under thrust.

Core Node Module

ESA(European Space Agency)/Thales Alenia Space

The core node, sitting in the center of the habitation section, serves as the intersection of all other modules. A long module oriented on end, the core node has four CBM’s connected to the rest of the ship, three symmetrically placed around its midsection connecting to the three wings, and one on its bottom connecting to the airlock.

The core node is split into three levels with a ladder running up along the full height of the module. The lowest level is primarily used for extra stowage, with the hatch into the airlock module in the center of the floor. A removable access ladder reaches down through the CBM into the suit up area, sloping so as to not block access to the airlock, which is itself accessed through a hatch in the center of the floor of the suit up area.

The central level serves primarily as a hub for moving around the Hail Mary, with the three hatches into the primary habitation wings and a ladder on one wall connecting to the lower and upper levels of the core node. This level is kept mostly clear except for equipment along the walls. Most of the Hail Mary’s primary computers are housed in racks on this level.

The upper level of the core node is the ship’s cockpit, the central hub of control for all ship systems. Two flight chairs sit amongst a sea of displays and interfaces. The commander’s station provides primary ship controls, including manual piloting, navigation, and ship status. The engineer’s station manages the robotic arm, EVA(Extravehicular Activity, a spacewalk) support, various sensors, telescopes, and external science equipment including the Astrophage sampler and Petrovascope.

Lab Modules and Science Airlock - Science Wing

JAXA(Japanese Aerospace Exploration Agency)/MHI(Mitsubishi Heavy Industries)

Heavily derived from the Kibo module on the ISS, the lab fills two short modules, the entire pressurized area of the science wing. Aside from a small airlock on the end of the outer module, every part of the lab is dedicated to scientific instruments, including a microscope, mass spectrometer, centrifuge, fume hood, oven, and much more.

The airlock interfaces with an exposed pallet area, and is primarily intended for passing sample collection devices and other equipment between the lab and the exterior of the ship, where the ship’s robotic arm can move equipment around.

Exposed Pallet - Science Wing

JAXA(Japanese Aerospace Exploration Agency)/MHI(Mitsubishi Heavy Industries)

The exposed pallet is attached to the end of the science wing, and serves as the primary location for mounting a variety of science instruments, including telescopes and sample collectors. The pallet interfaces directly with the lab’s airlock for passing samples into the lab, or even for passing smaller instruments inside for repair. Grapple fixtures and a dedicated robotic arm mount enable full use of the pallet and access to the rest of the exterior of the ship without crew EVA(Extravehicular Activity, a spacewalk)s.

Multi-Purpose Recreation Module - Crew Wing

ESA(European Space Agency)/Thales Alenia Space

The inner module of the crew wing is primarily dedicated to off-duty activities. It contains the bathroom, food prep equipment, a table for meals and crew discussion, exercise equipment, and a workstation with the third flight seat.

Dormitory Module - Crew Wing

ESA(European Space Agency)/Thales Alenia Space

The outer module of the crew wing is a short module, and serves as the crew dormitory and medical center. Three small bedrooms give the crew the only real privacy on the whole ship (aside from the bathroom). The medical center is a fully stocked clinic and includes a robotic system capable of performing many ordinary procedures, as well as a state-of-the-art medical AI diagnostic system.

Support Module - Engineering Wing

ESA(European Space Agency)/Thales Alenia Space

The support module on the inside of the engineering wing houses a lot of equipment, material, and spare parts. Most major life support equipment are located in the support module, including the water recycler, CO2(Carbon Dioxide) scrubber, and primary cooling and heating loops, along with extra water and oxygen tanks. Spare parts are also primarily stored here, along with various materials and supplies. Stock material for the workshop, including metals, plastics, adhesives, epoxies, and much else are also stored in the support module. Some lab supplies, including chemicals, are stored here instead of in the lab where there is limited storage space.

Workshop Module - Engineering Wing

JAXA(Japanese Aerospace Exploration Agency)/MHI(Mitsubishi Heavy Industries)

The small module on the end of the engineering wing is a dedicated workshop complete with a 5-axis CNC(Computer Numerical Control, automated control of manufacturing equipment) mill, multiple industrial 3D printers, and a wide collection of tools for performing repairs and modifications. Because of the possibility of debris and airborne contaminants, as well as for noise mitigation, the workshop module has a special door and a self-contained air filtration system.

Hazardous Material Closet - Engineering Wing

Voyager

Based on the Bishop airlock, this small module is attached to the end of the workshop module and serves as a sealed storage closet for potentially hazardous materials, especially those that can become airborne or are flammable. By being in a normally sealed module, fumes can be vented and fires can be mitigated without endangering the main habitable volume. In the worst case the module can be removed to allow spills to evaporate, to be cleaned on EVA(Extravehicular Activity, a spacewalk), or even to be totally jettisoned.

Habitation Section External Shielding

The Hail Mary must exist in many hazardous environments, including unknown environments in the Tau Ceti system. The pressurized crew habitat is especially vulnerable. To protect against micrometeoroids and orbital debris (MMOD), the outer skin of all pressurized modules is protected by whipple shields, MMOD blankets, or a combination of the two. The goal is to reduce and distribute the energy of particles before they hit the actual pressure hull.

More critical for the Hail Mary is the need for intense radiation shielding. Outside of the protective magnetosphere of the Earth, high energy solar radiation is a serious concern, and the Hail Mary could encounter many additional radiation environments, including energetic outbursts from Tau Ceti, high energy particles trapped in a planetary magnetic field similar to at Jupiter, and galactic cosmic rays, all of which could damage electronics and affect the crew’s health.

Luckily, Astrophage is a perfect radiation shield, as they absorb or block all forms of radiation (EM(electromagnetic, especially the spectrum of light) and particle). To protect the hab modules, millimetre thin cavities wrap around the pressure hulls underneath the MMOD shielding. The cavities are filled with Astrophage by astronauts on spacewalks, and the fill ports are crimped shut. To prevent the Astrophage from heating up the pressure hulls, the radiation shielding is sandwiched between two layers of insulation.

Astrophage shielding covers almost the entire exterior of the pressurized modules. Protrusions for structural supports and electrical and fluid connections use geometries that minimize projected gaps. The only large gap in radiation shielding is the single window in the whole ship, a small porthole in the airlock door. An Astrophage lined window shade allows even that gap to be protected.

Life Support

NASA/Lockheed Martin

Environmental control and life support systems (ECLSS) are partially derived from those onboard the ISS, which have been further developed to increase reliability and recovery efficiency, as well as to enable 1g operation. Redundant water recyclers and CO2 scrubbers with user serviceable components form the core of the nearly closed loop life support system. Ship-wide air ducts ensure proper circulation to avoid the formation of potentially deadly CO2 pockets.

For environmental control, the stable temperature of Astrophage is utilized both as a heat source and a heat sink. Heating uses a simple heat exchanger filled with Astrophage. Cooling with Astrophage is more challenging, as the coolant needs to be hotter than Astrophage, and Astrophage stays 96.4 degrees Celsius.

Three semi-redundant cooling systems are implemented on the Hail Mary. The most effective is the gravity dependent multi-stage heat pump. Staged compressors and heat exchangers result in a refrigerant temperature delta of over 100˚C. The hot side is passed through and cooled by an Astrophage heat exchanger, while the cold side is used to cool the cabin. This system is the most effective and uses state of the art compressors, but the compressors only work when there is a consistent ‘down’. During microgravity and for several hours after engaging thrust or spin gravity this primary system is unavailable.

A second, lower capacity Astrophage heat pump is available for microgravity, but the technology is far less mature given the unusual requirement of getting refrigerants to 100+ degrees with microgravity compatible compressors. The lack of prior heritage is an unacceptable risk, so a traditional cooling loop serves as final backup.

The Auxiliary Radiator System (ARS(Auxiliary Radiator System, backup thermal management for the Hail Mary)), with its traditional external radiators, is used as backup to the primary Astrophage cooling systems, as well as to bridge the transition to gravity when the primary systems are unavailable. The capacity of the exterior ammonia loop is far less than the mission requirement, and the Hail Mary can only operate minimal internal systems if the ARS is the only cooling system available for an extended period of time.

Water loops are pumped through heat exchangers or bypass channels for all three cooling systems and the heating system. Loops are independently pumped per module, with additional loops for the computer server racks, allowing for easy handling of various thermal loads across the vehicle as well as enabling per-module temperature control.

Astrophage Thermoelectric Generators

Roscosmos(Russian state aerospace corporation (space agency))/RKK Energia

Although Astrophage can be incorporated into many methods of electricity generation, the Hail Mary’s power grid prioritizes simplicity over efficiency. The basic design of the generators is built upon decades of experience with radioisotope thermal-electric generators, the foolproof solid state generators used in many deep space missions. In place of a radioactive heat source, Astrophage are modulated with CO2(Carbon Dioxide) spectrum IR(infrared: A lower frequency of light below visible light) to generate heat on demand. Astrophage thermoelectric generators (ATG) are small unassuming cylinders with no moving parts that can generate modest electrical power for decades.

The very center of an ATG is an IR emitting filament surrounded by an IR transparent casing. Outside the casing is a small cavity with a few grams of Astrophage to serve as the power source. When the filament is lit, the Astrophage are drawn to it, and they emit Petrova frequency IR light toward the outside of the cylinder. The outer skin of the cavity is a thin layer of tungsten which absorbs the emitted infrared(A lower frequency of light below visible light), heating it up.

The outer surface of the tungsten is covered in high temperature thermocouples embedded in a high temperature insulator. The heat in the tungsten conducts through the thermocouples to an external heatsink, which itself is surrounded in another layer of Astrophage which serves as the final heatsink. In order to absorb the heat fast enough the whole outside of the ATG needs to be coated in several kilograms of Astrophage to ensure a sufficient thermal transfer rate. Another layer of metal serves to contain the Astrophage, followed by MMOD(Micrometeoroids and orbital debris) shielding.

As the heat flows from the hot tungsten to the (relatively) cool Astrophage, voltage is generated in the thermocouples, which is harnessed for electrical power.

Electronics, voltage controllers, and the filament driver are all located in the end caps of the ATG cylinder. Because the heat output of the Astrophage can be modulated based on the central filament intensity, ATG’s can moderate their power output to meet electrical demand.

Due to a concern that an electronics failure could leave an ATG in a runaway temperature scenario if the IR filament was stuck at a high output state, temperature sensors in the tungsten heatsink are designed to automatically trigger the jettison of an ATG on an overtemperature event, using small solid fueled ejection motors. The tungsten itself serves as a buffer, absorbing significant heat before it melts and fails. Given the possibility of failure and jettison, ATG’s are designed for modest individual power output, and are used in aggregate for redundancy.

Separate ATG’s power the habitation and propulsion sections, eliminating the need for a power connection across the spin gravity tethers.

Astrophage Fuel Tanks

China/SAST(Shanghai Academy of Spaceflight Technology)

Even with near perfect mass-energy conversion of Astrophage, getting to Tau Ceti still takes a lot of fuel. The Hail Mary has 63 fuel tanks in three stacks spaced between the wings of the habitation modules. Each stack of tanks consists of bundles of three cylindrical tanks stacked seven tanks high.

The Astrophage tanks serve as the primary structure of the Hail Mary, as most of the mass of the ship will be within the tanks at the beginning of the trip. The tanks are standard cylindrical pressure tanks with hemispherical ends. Structural intertank segments extend past the domes on each end, and the outside of the tanks are wrapped in non-structural MMOD(Micrometeoroids and orbital debris) shielding. Tanks are manually bolted together on orbit, and all fluid and power connections are on the exterior of the tanks for connection to common plumbing and electrical raceways.

China’s deep industrial base enables Astrophage breeding at scale, resulting in world leading Astrophage management expertise residing in China. China’s national space enterprises extend that expertise into Astrophage management systems for the Hail Mary, particularly in the fuel storage and delivery systems.

Spin Drives

Spin Drive Working Group

“Hullo, it’s Scott Manley here. Some of you may still remember a Kerbal Space Program series I made a long time ago called Interstellar Quest, where we explored the Kerbol system while developing more and more exotic power and propulsion systems until Kerbals could, well, go interstellar. There were nuclear thermal fission rockets, magnetically confined fusion rockets, anti-matter induced fusion reactors, reactionless quantum vacuum engines, and finally the exotic matter powered Alcubierre warp drive for actually going interstellar.

Humanity is now about to conduct its own interstellar quest in real life, and unlike all the previously theorized interstellar engines—many of which might even violate the laws of physics—our interstellar spaceship is powered by practically mundane engines called spin drives, which amount to little more than a few electric motors and some infrared lights.

Except, that isn’t exactly true. Spin drives might be simple, but the engines are anything but. The real engines are the microscopic Astrophage cells which the spin drives use as fuel. All a spin drive does is move Astrophage to the right place and then activate it. And since most of the mass of the ship is Astrophage fuel, this means the Hail Mary is actually mostly an organic bio-ship. Just like the bio-ships in say, Mass Effect or Warhammer 40k, most of the Hail Mary will be grown rather than built, but instead of a single massive creature serving as a spaceship, we are strapping together quintillions of space micro-organisms so that we can ride them to the stars.”

Scott Manley, “Spin Drives Are The Best Interstellar Rocket Engine Ever”

Spin drives are novel, high power propulsion devices that trick Astrophage into expending their entire energy store by emitting Petrova frequency light in a specific direction. Since light has momentum, the emitted light imparts an opposite force on the spin drive, aka thrust.

Spin Drive Primary Mechanism

Project Hail Mary

Due to the critical need for a form of Astrophage propulsion, Project Hail Mary assembled a group of experts and facilities from all around the world to figure out a reliable and safe Astrophage engine design. After deciding on the spin drive concept, the engine project remained directly within Project Hail Mary through development and manufacturing.

Spin drives are needed for propulsion and attitude control on both the Hail Mary and the Beetles. By utilizing dozens, hundreds, or even thousands of individual spin drives depending on the needed thrust, a single type of spin drive can serve all purposes. To that end, an individual spin drive is fairly small and provides under 1kN of thrust.

Spin drives are made up of a few main components. The heart of the drive is an IR(infrared: A lower frequency of light below visible light) transparent triangular prism mounted to a motor. An Astrophage feed line leads to one face of the prism, within which a weak IR emitter briefly pulses to attract Astrophage to the prism’s surface. A strong IR emitter excites the Astrophage after a ⅓ rotation to produce directed thrust. A wiper removes depleted Astrophage after an additional ⅓ rotation. Integrated sensors check for proper rotation, operating temperature, fuel clogs, and wiper failure.

Spin Drive Banks

Project Hail Mary

Individual spin drives are installed into banks. Three different sizes of banks are used. The largest bank is clustered for the Hail Mary’s primary engines. A smaller bank is used for attitude control on the Hail Mary’s reaction control system (RCS). The smallest and most unique bank is for the Beetles, as it performs both primary propulsion and attitude control by mounting several spin drives off axis.

Main Propulsion and RCS Housings

NASA/MSFC(NASA Marshall Space Flight Center)/SAST(Shanghai Academy of Spaceflight Technology)

The spin drive banks need considerable ancillary equipment in order to function, which is the job of the main propulsion housings located at the bottom of each of the three fuel stacks. Each housing has twelve banks of spin drives. Each housing needs to transfer up to 40 MN of force into the fuel stacks. They also perform a lot of Astrophage flow management from the tanks to the spin drives. Dedicated ATGs provide electrical power to each housing and fuel tower, powering IR(infrared: A lower frequency of light below visible light) emitters, motors, pumps, and avionics(electrical and data systems for controlling a spacecraft, especially computers and sensors.). Force sensors under each bank feed into avionics alongside inertial measurement units and accelerometers. Avionics in each housing feed into central control systems that ensure the force from each housing is balanced, even as the centre of mass moves around (such as crew moving around the cabin). As spin drives fail they are taken out of service without disrupting acceleration, as the failure rate is predicted to be lower than the fuel burn rate. As the ship gets lighter, the spin drives spend more time idle, maintaining consistent acceleration rather than force.

Attached to each main propulsion housing is a spin drive RCS(Reaction Control System, gyroscopes and thrusters for controlling a spacecraft’s spin) pod. Each RCS pod has 5 banks of spin drives, oriented to allow for full 6 degrees of freedom for rotation and translation. Even as the mass distribution changes, the RCS pods can modulate thrust levels to maintain fully decoupled control authority. Three additional RCS units are mounted to the top of each fuel tower, for a total of six pods on the Hail Mary.

Interstellar Shield

Interstellar Shield Working Group

Despite the MMOD(Micrometeoroids and orbital debris) and Astrophage radiation shielding around the habitation modules and the MMOD shielding around the fuel tanks, the Hail Mary would be fatally exposed during an interstellar transit without dedicated forward shielding. Empty space is not actually empty, and despite our solar system being in a relatively sparse part of the Milky Way galaxy, there is still enough interstellar medium to be worried about. Most of what is encountered is interstellar gas: primarily hydrogen, some helium, and trace heavier elements. At relativistic speeds, these will act like cosmic rays, with the same radiation risk, and with the ability to infiltrate and weaken materials and damage electronics. Far more infrequent are microscopic dust grains, which at relativistic speeds will erode or puncture the front face of the ship.

In recognition of the extreme hazards of relativistic travel, Project Hail Mary set up the Interstellar Shield Working Group (ISWG) to assess, characterize, and mitigate interstellar gas and dust. The resulting design is a multi-layer forward shield made possible by the incredible super cross-sectionality of Astrophage. The shield is mounted to the top of the fuel tanks and shadows the entire ship in the direction of travel. The shield serves as protection during the acceleration and coast phases, but for the deceleration phase, the spin drive exhaust itself serves to shield the Hail Mary, since the interstellar shield will be on the trailing end of the ship relative to the interstellar medium. The sheer intensity of the spin drive exhaust vapourizes dust grains and inertially accelerates particles, redirecting or slowing them down.

Astrophage Rad Shield Layer

CNSA(Chinese National Space Agency)/Project Hail Mary

The base of the interstellar shield is a flat layer of Astrophage. The layer is made of triangular panels that interlock with tongue and groove style interfaces, eliminating any gaps in Astrophage protection across the entire shield.

Thanks to the super cross-sectionality of Astrophage, this layer is able to block and absorb even relativistic particles. The alternative at the 0.91c of the Hail Mary would be several metres of solid shielding. This layer of Astrophage is also the final defence against incoming dust.

At high relativistic velocities, not only does the forward shield block interstellar gas, but it also stops almost all galactic cosmic rays, as the velocity compresses the distribution of incoming cosmic rays to be increasingly forward as the ship’s velocity approaches the speed of light.

Whipple Shield Layers

NASA/Northrop Grumman

Even with the Astrophage shield, dust grains will punch holes in the top of the Astrophage containment panels, potentially transferring enough momentum into the Astrophage to damage the underside of the containment panels as well. Although not effective at stopping dust grains at the coast velocity of the Hail Mary, the multi-layer whipple shield serves two purposes.

Firstly, the layers of additional shielding cause dust grains to expend energy and break apart, preventing blow-through of the Astrophage panels. Secondly, the layers serve to block the view of any exposed Astrophage, minimizing the chance of newly freed Astrophage seeing starlight and choosing to escape.

Similar to the Astrophage layer, the whipple shield is assembled from interlocking triangular panels, stacked in two layers. The panels are made of a thin aluminum frame with ceramic reinforced Kevlar fabric stretched across them. The layers of the shield are 2m apart.

“I don’t see how we can protect the ship at 0.7c, let alone 0.9c. We need to slow down the transit. At these speeds we need several metres of solid shielding just to block the radiation, it simply doesn’t work.”

“Wasn’t there a plan to send little credit card sized spacecraft to Alpha Centauri at something like 0.3c? We’re only going three times as fast, how can we need so much shielding?”

“Even Newtonian energies increase with the square of velocity, but high fractional light speeds are a whole different level, our velocities are barely even comparable to the breakthrough starshot concept, the energy levels are so much higher.”

“The testing coming out of CERN is showing Astrophage to be a near perfect absorber of high energy particles. The habitation group is already looking at using a layer of Astrophage as radiation shielding around the crew areas, why can’t we do the same?”

“I thought they were looking to block solar radiation and cosmic rays, whereas we need to block the interstellar medium?”

“At our velocities, there isn’t much difference between interstellar gas and galactic cosmic rays, Astrophage could work, we should follow up with CERN and the hab groups. I’m more concerned about dust. Astrophage may absorb individual nuclei, but what about dust grains that are nearly as large as themselves? I worry the momentum will eviscerate them, they aren’t invincible after-all.”

“Wait a minute, aren’t we thinking about this all wrong? We already assume the spin drives will be sufficient during deceleration, so why can’t we have active spin-drive shielding? Vapourize the dust, deflect the particles. The total energy we’re needing to block is high but nothing compared to how much we’ll have stored in our Astrophage tanks.”

“The energy a shield needs to absorb is one thing, but active spin drive exhaust would be almost entirely wasted, only a tiny fraction would actually do any work deflecting the interstellar medium. I don’t think that is a very viable strategy.”

“Don’t be so hasty, if the dust turns out to be an Astrophage killer, maybe an active shield would be more mass efficient than a super thick slab of metal or water. We need to look into ways of testing high c dust grains against Astrophage.”

“We may also be able to use a whipple shield to break apart dust grains into smaller chunks that Astrophage may more easily block. It’d be far lighter than a solid shield if it works.”

Preliminary Interstellar Shield Working Group Design Meeting — March 2027

Distributed Truss Structure and Jettison Mechanism

ISRO(Indian Space Research Organization (space agency))/Roscosmos(Russian state aerospace corporation (space agency))

In order to support and rigidize the layers of the shield for the acceleration of the Hail Mary, a simple truss is assembled onto pre-fabricated mount points on the seams between panels.

With extensive expected damage to the shield, including holes in the Astrophage panels, the interstellar shield is jettisoned upon arrival to the Tau Ceti system, while the shield still faces away from Tau Ceti itself. This prevents unintentional Astrophage migration out of the shield, and removes the shield from obstructing the forward view of the Hail Mary.

Spin Gravity Tether

Early in the Hail Mary design planning, it was determined that gravity would be greatly beneficial for provisioning and using a science lab. It also enables a more capable workshop. Although discussed, simply flying in circles while under thrust was deemed impractical. Instead, a tether based centrifuge serves to provide 1g of acceleration to the habitation module when needed.

When centrifuge mode is activated, the ship uses its RCS(Reaction Control System, gyroscopes and thrusters for controlling a spacecraft’s spin) to begin spinning end over end. As it does so, mechanical docking mechanisms disconnect the habitation section from the propulsion section, and winches slowly reel out tethers. The habitation section drops 150m out the bottom of the ship, providing an apparent gravity of 1g at spin rates of 2.44-2.54 RPM, depending on fuel load.

By dropping the habitation section out the bottom of the propulsion section, the direction of spin gravity and thrust gravity are the same relative to the habitation modules, and the load points for the hab are shared between modes.

Tether Cable, Winch, Docking System

NASA/JPL(Jet Propulsion Laboratory, NASA center focused on planetary exploration spacecraft)

Due to the horizontal spread of the habitable modules, a central tether would cause the cantilevered habitation wings to experience significant torque. Instead, tethers are distributed between the central node module and further out on the wings of the habitation section. A truss helps further distribute the load of the habitation wings. Each tether point contains several redundant tethers, two sets of four tethers on each of the wings and three sets of four around the central hub module. At every tether point half the tethers or winches can fail without impacting centrifuge performance.

With 36 individual tethers and winches as part of the system, JPL’s sensitive tension matching winches ensure load balancing. In the case of a winch failure, the tether can be cut, although this is only advisable in certain system configurations. The centrifuge integrates the tether tension data into the flight software to precisely and safely extend and retract the habitation section.

Tether Assembly and Housing

Blue Origin

The winch housings, located on the propulsion section truss structure, also serve as the structural load points for the habitation section when retracted. To this end, the tethers are directly integrated into probe and drogue docking ports, with the tether being mounted to the tip of the probe on the habitation section, and feeding through the middle of the drogue on the winch housing. The tethers mechanically ensure alignment. When the tethers are fully retracted, wedges are extended from the winch housings into recesses on the probes, creating a strong mechanical connection.

Full scale tether testing took place in Blue Origin facilities at KSC, including docking, undocking, and full length extension and retraction, prior to launch and integration with the Hail Mary.

Canadarm3

CSA(Canadian Space Agency)/MDA(Canadian aerospace company)

Officially named the Hail Mary Remote Manipulator System (HMRMS), the external robotic system has the unique distinction of being the only major subsystem already in development prior to the start of the project. Modified only slightly from the planned robotic arm for NASA’s Gateway lunar space station, Canadarm3 is not only a useful tool for the crew while at Tau Ceti, it is a crucial element of ship assembly alongside Canadarm2 onboard the ISS.

Using grapple fixtures spread all across the Hail Mary, Canadarm3 can ‘walk’ by moving hand over hand from fixture to fixture. It can also move exposed cargo and science equipment from storage racks to the exposed pallet on the science wing, into the science airlock, or to other parts of the ship.

A separate multipurpose ‘hand’ can be attached to either end of Canadarm3. The hand has a full-size grapple on its end, plus a smaller utility arm and three swappable tools mounted radially around its wrist. An adapter to a full-size grapple also exists for the small arm, allowing Canadarm3 to walk around the ship while carrying payloads with either full-size or small grapple fixtures. The tools include a bolt driver and torque driver, various scanners and imagers, and lights.

As part of the modifications to serve the Hail Mary, the Canadian Space Agency (CSA) extended the development of autonomous control software already planned for Gateway to allow the arm to perform many tasks without crew supervision, falling back to manual control only if the arm finds itself in an unexpected situation.

Central Spine

Airbus/Boeing

Running directly up the center of the ship is a truss structure connecting directly from the core hub module’s tether ports up to the interstellar shield, as well as to the sets of horizontal connecting trusses at both ends of the ship. The spine is far more than just a structural truss—its structural job could be accomplished by other means—as it also houses several temporary and permanent subsystems.

A significant amount of secondary compute is housed inside the spine, along with ATGs for power. High pressure helium tanks for fuel tank pressurization are also stored on the spine, along with high pressure tanks of several other gases for use by the crew. The spine also houses triplicate communications systems for use in the Sol system whose dishes also allow for limited scientific radio observations at Tau Ceti. Flat-panel phased array radar points out from the center of the spine, blocked only by the fuel stacks. Several storage pallets house miscellaneous equipment, including but not limited to spare parts, repair materials, and extra scientific and fabrication equipment, which can be brought inside via the airlock.

Primary Structural Trusswork

ISRO(Indian Space Research Organization (space agency))/JAXA(Japanese Aerospace Exploration Agency)

Due to the unusual layout of the habitation section and fuel stacks, considerable trusswork is required to rigidly attach the fuel stacks together, as well as to support the habitation section. The trusswork is made primarily out of hollow tubes with tapered ends, increasing rigidity for the same mass as compared to solid struts. Trusswork also wraps around the habitation modules, supporting them during the frequent 1g accelerations and limiting torque on the CBM(Common berthing mechanism, a module attachment standard used on the ISS)s, as well as around the fuel tanks, providing additional load paths for the especially high loads the tanks need to support for years at a time.

Several portions of truss are pre-assembled on the ground, while other parts (like the truss wrapped around fuel or habitation modules) are entirely assembled on orbit by spacewalkers.

Hail Mary AI

OpenAI/Anthropic/Deepseek

Due to the scale and complexity of the ship—operated by a small crew without any communications back to Earth—AI models are trained to be experts in all the Hail Mary systems as a replacement for mission control. Three bespoke competing models from OpenAI, Anthropic, and Deepseek are trained on a full dataset about the Hail Mary and its mission, including schematics and details for every subsystem, dozens of simulated flight days with a mock crew and mission control, and every recorded detail from the design to manufacturing to assembly of every part of the ship. On the Hail Mary, these models are run in parallel, and a fourth system assesses the responses. If all three models agree, as judged by the adjudication system, a final response is synthesized from the three outputs and relayed to the crew.

This system, colloquially just called “Mary”, is capable of interfacing with lower level ship systems, but requires explicit crew permission to perform any actions upon those ship systems. Lower level autonomous systems as part of ECLSS(Environmental control and life support systems), avionics(electrical and data systems for controlling a spacecraft, especially computers and sensors.), and navigation run independently and can perform autonomous operations within explicit bounds, similar to any other modern spacecraft.

Significant compute power is provided onboard the Hail Mary for this crew-interactable AI system, but the models are still optimized for efficiency and accuracy over total capability. At any point a crew member can view the individual model responses, the assessment, and what—if any—Hail Mary systems the AI was suggesting to modify.

Hardened Compute

Nvidia/AMD/TSMC/Micron

Although much of the critical compute hardware is housed in the radiation protected habitation modules, off the shelf silicon is insufficient for the Hail Mary’s computing needs. Customized processors and memory chips designed for high levels of fault tolerance, long lifetimes, and power efficiency are used for the major computing infrastructure inside the habitation section, supporting the Hail Mary AI, centralized computers for the crew to access, and critical flight control systems. Several server racks are built into the core module with integrated liquid cooling loops tied into the environment control systems. These servers also store all critical mission information, including large libraries of scientific software, astronomical and biological information, all known information about Astrophage, and the complete dataset about the Hail Mary itself.

Radiation hardened processors are also needed for many of the additional subsystems outside of the pressurized volume, including key avionics(electrical and data systems for controlling a spacecraft, especially computers and sensors.) computers across the propulsion system, and ancillary compute nodes located in the spine.

Human Knowledge Project

Google/Internet Archive/Academia/Kioxia/Samsung

The Hail Mary is loaded with all mission relevant information in the onboard server racks. Despite this generous data store, mission designers foresaw a lack of available reference material as a potential mission failure scenario. Given that the Hail Mary would be completely isolated from Earth, and that the crew were being sent to discover something literally unknown, it was deemed prudent to send along as many collected resources as possible.

The Human Knowledge Project (HKP) is the culmination of that idea. Over a hundred exabytes of data are stored in dozens of cabinets along the ship’s spine. The individual solid state drives are arranged in thousands of small pools with limited fault tolerance. The loss of a storage pool is deemed unlikely to affect the mission, since the crew are expected to only access a miniscule percentage of the stored data. A Google-developed search and storage system enables rapid discovery of contents. A high bandwidth laser link ensures crew access to the HKP even when the ship is in centrifuge mode.

The collected data is a wide assortment from many sources. Dozens of participating universities ensure not only the inclusion of every published scientific paper, but also the broad inclusion of reference material from every professional field. Digitized versions of almost every book ever published, along with many audiobooks, magazines, recorded lectures, newspapers, TV shows, movies, and more fill out a comprehensive collection of published media. With the help of human tended automation selecting relevant material, a significant portion of the public internet is also archived, including forums, blogs, software documentation, and a sizable chunk of YouTube. Especially included is a collection of nearly all software ever written and emulators for nearly every computer architecture ever made.

The accumulation of the dataset for the Human Knowledge Project is the result of a half decade of effort, and the physical server cabinets launch near the end of Hail Mary assembly, where spacewalkers install them in pre-planned locations along the central spine.

Petrovascopes

DLR(German space agency)/CNES(French space agency)

The most important external science instrument is the Petrovascope. Important enough to send three. These are mid-IR(infrared: A lower frequency of light below visible light) telescopes that allow the Hail Mary to detect Astrophage flying through the Tau Ceti system, especially if there is a Petrova line.

The scopes are fairly compact with a limited focal length. They attach to grapple fixtures and can be moved to any powered grapple fixture across the ship, although the primary attachment point is at the top of the central spine following interstellar shield jettison. The head of the Petrovascopes can swivel in two directions, granting an approximately 120 degree accessible area of the sky from a fixed Petrovascope.

Astrophage Sampler

NASA/Goddard

A dedicated Astrophage sampler, developed based on the experience of the ArcLight(Joint NASA/ESA/JAXA Petrova line sampler probe, assembled from SLS, ESM, and MMX.) and Hongxianwen-1(Chinese Petrova line sampler probe. Roughly translates to ‘asking the red thread of fate’) sample return missions, allows for the easy collection of Astrophage at Tau Ceti. The sampler has two slides for bi-directional sampling, and can be passed through the science airlock, where the slides can be removed and replaced by crew members in the lab. Collection is performed by extending the sampler away from the ship on the end of the robotic arm.

Beetles

Rocketlab/Project Hail Mary

The Hail Mary carries four ‘beetles’—purpose built interstellar probes designed to return data and small physical samples from Tau Ceti to Earth. The spacecraft are skinny to minimize cross-sectional area, and are made of three distinct segments.

The rear segment is an Astrophage fuel tank with a spin drive bank. The spin drive bank contains several off-axis spin drives allowing for 3-axis rotational control. A small ATG is embedded in the fuel tank without a dedicated Astrophage heat sink, to avoid wasting any available fuel.

The central segment contains the avionics(electrical and data systems for controlling a spacecraft, especially computers and sensors.), communications equipment, navigational sensors, and a small payload bay. A pair of fold out low gain antennas complement a pair of directional high gain antennas for use once the beetles near Earth. The payload bay accepts a payload module that the crew can prepare inside the lab before passing the module through the science airlock to the robotic arm, which in turn slots the payload into the beetle.

The forward segment is the interstellar shield, with a few layers of stuffed whipple shielding in front of a multi-celled Astrophage tank. The Astrophage in the shield is also connected to the fuel system, and is used during the deceleration phase when the shielding is provided by the spin drive exhaust.

Although the beetles only have partial redundancy in their systems, having four of them provides mission redundancy.

Size:

Length: 2.3 m

Width: 0.5 m

Mass:

Dry Mass: 43.5 kg

Astrophage Mass: 913 kg

Wet Mass: 956.2 kg

Payload Mass: 5 kg

Mass Ratio: 21:1

Acceleration:

5g

Sol Travel:

Earth Time: 13 years 120 days

Ship Time: 5 years 294 days

Distance: 11.91 light years

Coast Distance: 95.5%

Coast Duration: 5.21 years

Acceleration Duration: 218 days

Peak Lorentz Factor: 2.4

Peak Velocity: 91% Light Speed

“So Sir Beck, you have been tasked with a very important element of the Hail Mary mission, the return probes. This seems like a pretty big deal for Rocket Lab, how has development been going?”

“Of course it is an absolute honour to be a part of this project. I mean, what is a bigger deal than helping save humanity, right? We’ve obviously worked on interplanetary spacecraft before, but let me tell you, interstellar is a whole different beast, it really is. The universe really doesn’t want you to send a spacecraft between stars, especially at nearly the speed of light. But we’re going to do it. It has been excellent working with the Hail Mary project, they really know how to get things done. We’ve got experts from the interstellar shield group, experts in Astrophage management from the Chinese space agency, and members of the spin drive group all contributing in major ways. It’s really challenging, but we are used to doing challenging things, and we’re on schedule right now, so it’s actually going quite well.”

“Okay, wow, so these probes aren’t just a Rocket Lab project? Sounds like all sorts of groups are working on different parts. What exactly is Rocket Lab’s role?”

“Yeah, of course, it’s totally a team effort. I don’t think any part of the Hail Mary is a singular endeavour. It all has to work together, and there is so much new technology being developed that it makes a lot of sense to utilize expertise from around the world. For the probes, Rocket Lab is making the actual spacecraft bus, so we’ll be doing final integration of the beetles, but the whole propulsion and interstellar shield sections are being provided from other parts of the Hail Mary project.”

“You just called the probes ‘beetles’, did I hear that right?”

“Oh, yeah. We’ve been calling the probes ‘beetles’ internally because the design sort of resembles a beetle. It has three body sections, just like a beetle, and six deployable antennas. One of the engineers thought the antennas looked like insect legs, and the name sort of stuck. The antennas are in trade right now though, so I don’t know if they’ll make it to the final design.”

“That’s really interesting, I’ll definitely keep an eye out for the antennas on the final design. Now, Rocket Lab always has fun names for its missions, and you’ve got a launch coming up with an early prototype spin drive. If you don’t mind me asking, is a fun name for that spacecraft?”

“The upcoming mission is a very important test, not only to demonstrate the spin drive technology, but also to test a bunch of subsystems for the beetles. We’re very excited to be building the spacecraft but also to provide launch on Electron as well. As for the name, I’m not ready to announce anything yet, but I’ll just say that the name will reflect that despite not being an actual beetle, this spacecraft is closely related to them.”

Sir Peter Beck during an online interview with Tim Dodd — May 2028

The Assembly

The Hail Mary is the culmination of an orbital assembly project that dwarfs even the ISS(International Space Station), performed on compressed timescales with significant infrastructure requirements both on the ground and in orbit. The ISS itself is prepared as an orbital shipyard, where modules and components are staged for assembly. Thousands of spacewalk hours are needed to assemble the components into a functional interstellar spaceship. Even while the Hail Mary is being designed, preparations for its assembly are urgently planned and executed.

Modifying the ISS

Modifications to the ISS begin well before the Hail Mary is even a guaranteed project, beginning with an acceleration of the install of the final two iROSA(A version of a Roll Out Solar Array used on the ISS) solar arrays, followed by a start on modifying the interior of the ISS to support more crew. Very quickly the requirements for the Hail Mary’s assembly eclipse the ISS’s capabilities, and the string of modifications strain the station nearly to its breaking point.

Hail Mary

The Hail Mary is assembled off of PMA(Pressurized Mating Adapter, a docking adapter from CBM to the older APAS-95 docking standard)-2/IDA(International Docking Adapter, an adapter between the APAS-95 docking standard and the International Docking System Standard (IDSS))-2, the forward docking port on the Harmony module. Once the first module launches, this port becomes unavailable for visiting vehicles, particularly Dragon. As the Hail Mary grows, the structural strain on PMA-2 becomes a challenge for station attitude control. To mitigate the attitude control problems, three Station Attitude Control Augmentation Systems (SACAS) are attached to the Hail Mary, one on each of the fuel stacks, with integrated gyroscopes and reaction control thrusters.

Chinese Orbital Segment

With China participating in Project Hail Mary, and with the ISS in need of more habitable volume, modules for the planned expansion of Tiangong—the Chinese space station—are instead launched to the ISS. To accommodate this, PMA(Pressurized Mating Adapter, a docking adapter from CBM to the older APAS-95 docking standard)-3 and IDA(International Docking Adapter, an adapter between the APAS-95 docking standard and the International Docking System Standard (IDSS))-3 are moved from the zenith(up, away from Earth) port on Harmony to the nadir(down, towards the Earth) port on Unity. The central Chinese module, with an IDSS(International Docking System Standard) compliant docking port, docks to IDA-3 on the end of PMA-3. Two additional modules dock to the node on the end of the first Chinese module, forming in a T-shape hanging off the bottom of the ISS. The modules add additional crew accommodations, two docking ports for Chinese visiting vehicles, and an EVA(Extravehicular Activity, a spacewalk) airlock.

Assembly Logistics Facility

To reduce schedule pressure between the launch and integration of components, and because many parts require spacewalks to assemble on the Hail Mary, the ISS is expanded with a storage yard. The Assembly Logistics Facility (ALF) is a simple truss structure attached to the top of the Z1 truss, utilizing the existing mounting equipment. The ALF has attachment points on all sides to allow for the storage of materials and deliveries.

The ALF interrupts the communications facilities on the Z1 truss, so Starlink laser terminals are integrated onto the ISS in lieu of TDRSS(Tracking and Data Relay Satellite System, NASA communications satellites.) for primary connectivity.

Visiting Vehicle Ports

With PMA(Pressurized Mating Adapter, a docking adapter from CBM to the older APAS-95 docking standard)-2/IDA(International Docking Adapter, an adapter between the APAS-95 docking standard and the International Docking System Standard (IDSS))-2 used for the Hail Mary, and PMA-3/IDA-3 used for the Chinese station modules, and with the Chinese segment and the Hail Mary itself taking up more and more space around other docking and berthing ports, ensuring sufficient ports for visiting vehicles becomes more challenging throughout the Hail Mary’s assembly.

After the relocation of PMA-3, both the nadir(down, towards the Earth) and zenith(up, away from Earth) CBM(Common berthing mechanism, a module attachment standard used on the ISS) ports of Harmony are available for Cygnus and HTV-X. The zenith port receives a replacement IDSS(International Docking System Standard) adapter, coinciding with a switch to IDSS docking ports on HTV-X and Tianzhou, which also begins using the Harmony zenith port. The zenith port is available until the final propulsion housing is integrated on the Hail Mary, which blocks access.

The Chinese Orbital Segment core module has a node with five docking ports. The port and starboard ports are used for the additional Chinese modules, and the aft port faces towards Rassvet and Nauka and is never usable. The forward port is available only until the Hail Mary’s habitation saddle is assembled, after which only the nadir port is available, which serves as the primary Shenzhou port for the project. The forward port also conflicts with the nadir CBM on Harmony, such that any visiting vehicle on that CBM must be detached and held out of the way by Canadarm2 when a vehicle docks or undocks to the Chinese forward port. Early Shenzhou and Tianzhou missions use the forward port until accommodations on the Russian segment are made available. Because the core module is launched on an accelerated schedule, the Chinese module’s ports keep the APAS(Series of docking mechanism standards)-89 derived Chinese docking mechanism. Shenzhou vehicles therefore retain the same docking mechanism for compatibility. Tianzhou vehicles are eventually switched to use an IDSS compliant docking system.

This leaves the Russian Orbital Segment, which takes the bear’s share of the visiting vehicle load. Rassvet is undesirable for any docking activity due to its proximity to the new Chinese modules, but following the installation of shielding on the Chinese modules, Rassvet is used for Progress cargo vehicles. Zvezda’s aft port is closed prior to ISS modifications due to increased leaks in PrK, and is only used to trasnfer propellant into Zvezda from Progress spacecraft. Adapters with IDSS docking ports are added to the Poisk module and to the nadir of Prichal, for use by Dragon, Tianzhou, and HTV-X. Prichal’s aft port gains an adapter to the Chinese docking mechanism for use by Shenzhou. The port and starboard ports of Prichal are kept as-is for Soyuz. The forward port of Prichal remains unusable due to facing Rassvet and the Chinese segment.

In total, up to 11 ports are available for visiting vehicles, which is reduced down to only 8 by the end of the project.

Astrophage Tankers

The Hail Mary requires a lot of Astrophage. In fact, it is almost entirely Astrophage by mass at the beginning of the journey. Simply getting all that Astrophage into the ship represents a monumental task. Launching the Astrophage tanks pre-filled is not an option for several reasons. First, the tanks would be far too heavy for any launch vehicle. Second, the tanks need to be launched early enough to continue assembly, but the Astrophage fuel needs to be saved for continued breeding until much later. Finally, the Hail Mary centrifuge test needs to be performed with an almost empty Astrophage load for representative mass balance.

The solution is Astrophage tankers, many hundreds of them. Effectively mini Astrophage tanks bolted to an orbital tug, the tankers are designed to be able to loiter in orbit for several years before rendezvousing with the ISS where they are attached to the refueling ports on the Hail Mary for Astrophage transfer. The tankers are designed and built by the same Chinese organizations that build the Hail Mary fuel tanks and fuel transfer interfaces, led by SAST(Shanghai Academy of Spaceflight Technology).

Due to the enormous potential energy of even a single Astrophage tanker, only a single rocket is certified to launch them. Although remote launch sites would be preferable, the only rocket with sufficient flight rate, payload capacity, and reliability is the Falcon 9. Once the tankers are ready to start being launched, Falcon 9 begins launching almost exclusively Astrophage tanker missions from both LC-39A and SLC-40 at the Cape. An additional Falcon 9 launch site is constructed at LC-37 in place of a Starship pad, and the booster landing droneship Of Course I Still Love You is relocated to Port Canaveral to support the higher flight rate. This enables SpaceX to launch all of the Hail Mary’s fuel across nearly 800 flights in just over three years. The tankers, being designed specifically for the Falcon 9, weigh just over 17t after being loaded with 15t of fully enriched Astrophage.

Once in orbit, the tankers arrange themselves slightly above the orbit of the ISS in the same orbital plane, awaiting readiness of the Hail Mary for refueling. The entire fuel transfer into the Hail Mary takes around eight months, accounting for deconfliction with spacewalks and other ISS deliveries.

Launch Vehicles

Rocket Report: All Space Station, All The Time
“We’ve had more visiting vehicles at the ISS just this week than we’ve had some entire years.”

Ars Technica — October 2032

The Falcon 9 launches the majority of the mass of the Hail Mary in the form of Astrophage tankers, but there are plenty of other components to launch. The rockets that launch the new ISS components are to be expected, including the Long March 5B for the Chinese segment modules, and Vulcan with its extended fairing for the ALF(Assembly Logistics Facility, storehouse for Hail Mary components on the ISS). Falcon 9 and eventually Antares 330 launch Cygnus, with the other visiting vehicles launching on their usual rockets.

For the Hail Mary itself, the habitation modules are launched on Ariane 64, Vulcan Centaur, and a couple shorter modules on H3. The Astrophage fuel tanks, being a little skinnier and a lot lighter than the hab modules, launch on Ariane 6, Vulcan, Long March 12B, Falcon 9 (before it starts launching Astrophage tankers), Zhuque-3, Tianlong-3, and a handful of other medium lift Chinese rockets.

Smaller components and unassembled trusswork launch on LVM3, Soyuz, Angara, and a wide array of Chinese launchers, including the LM(Long March, also Chang Zheng, a series of Chinese launch vehicles)-7 and LM-8. Larger pre-assembled truss segments, especially the spine and horizontal trusses, are launched on Vulcan, Ariane 6, Long March 5B, and New Glenn, utilizing their large payload volumes. The interstellar shield is launched in stacks of triangular panels primarily on the LM-7, LM-8, and LM-6A.

A handful of elements are too large for standard 5m fairings and launch exclusivley on New Glenn. In particular the pre-assembled central spine segments, including the core hub tether system and the interstellar shield jettison system, and the spin drive housings.

The spindrive test satellite Yoko, as well as the beetle prototype Pete are each launched on Electron with only small loads of Astrophage. The four production beetles are launched on Falcon 9 due to their significant Astrophage load, extra size, and extra mass.

Orbital Transfer Vehicles

With the Hail Mary being heavily derived from the US side of the ISS, but without the Space Shuttle available for delivery, a different means of propelling modules and components en route to the ISS is needed. Three main transfer vehicles are designed for the Hail Mary project. The largest is an ATV(Autonomous Transfer Vehicle, a retired European cargo spacecraft)/ESM(European Service Module, the power and propulsion portion of the Orion spacecraft.) derived vehicle built by ESA(European Space Agency) and Airbus, which is used for all the habitation modules and some of the other major components including the spine. A smaller, fully launcher agnostic transfer vehicle is mass produced by Impulse Space in the US, primarily for the smaller component deliveries, especially on launchers with sub-4 metre diameter payload fairings. There is also a Chinese transfer vehicle, whose design shares much in common with the Astrophage tanker service module, which is primarily used for the fuel tanks.

Spacewalks and Crew Scheduling

The design of the Hail Mary requires thousands of spacewalk work-hours, which was deemed an acceptable design trade. Up to six active spacewalkers can be outside at once, two each from the US, Russian, and Chinese airlocks with their respective suits. Each crewmember completes around 3 spacewalks every two weeks. The crew is split into two shifts, a spacewalk shift and a logistics shift, and the shifts swap every week to give crewmembers breaks from the spacewalks. The spacewalk shift includes both spacewalkers and support crew who help with suit donning/doffing, robotic arm operation, and other tasks. The logistics shift prepares the suits and equipment, loads and unloads visiting vehicles, performs station maintenance, and works on internal Hail Mary configuration. Additionally, during the logistic shift, remotely operated robotic arm operations pre-place material for the next day’s spacewalks. With a full complement of 20 crew, each segment performs 4-5 spacewalks per week.

Roscosmos(Russian state aerospace corporation (space agency)) and CNSA(Chinese National Space Agency) build additional Orlan and Feitian EVA(Extravehicular Activity, a spacewalk) suits, respectively, to handle the greatly increased load. NASA modifies its xEMU contract with Axiom to turn the AxEMU suits into microgravity suits instead of lunar suits, which augment and eventually replace the aging NASA EMU(Extra-vehicular Mobility Unit, NASA spacesuit) suits.

Bolts

Since much of the assembly of the Hail Mary involves bolting together truss structures and fuel tanks, special attention is paid to the bolts themselves. As much as possible, a single bolt design is used (in varying lengths), featuring a special captive head that locks into a custom socket for bolt drivers. The bolt head retains compatibility with standard hex sockets and wrenches. The bolts also have captive lock washers designed to prevent the bolts from backing off, while the ship components feature either captive nuts or built in threads. Canadarm3 includes a dedicated bolt carrier and driver tool for its hand, and can autonomously perform assembly and disassembly tasks, including bolting fuel tanks together. Bolt carriers are also provided for astronauts, who can keep the bolts captive in threaded receivers in the carriers.

Timeline of Hail Mary Assembly

June 2026: The leak in the PrK module in Zvezda worsens suddenly and significantly, permanently disabling the aft docking tunnel of the ROS(Russion Orbital Segment, portion of the ISS built by Russia). Progress operations at Zvezda are restricted to automated commodity transfer and station boost burns.
H2 2026: NASA completes the installation of the iROSA(A version of a Roll Out Solar Array used on the ISS) solar arrays on the ISS(International Space Station).
Q4 2026: SpaceX begins launching Dragon on an increased schedule, bringing the average ISS crew complement to nearly 10.
Q1 2027: Internal ISS renovations near initial completion. Science and equipment racks are gutted and several new crew bunks are installed.
Q3 2027: Roscosmos(Russian state aerospace corporation (space agency)) returns to a 3 month launch cadence on Soyuz, bringing the average ISS crew complement up to nearly 13.
Q3 2027: The zenith(up, away from Earth) docking adapter PMA(Pressurized Mating Adapter, a docking adapter from CBM to the older APAS-95 docking standard)-3/IDA(International Docking Adapter, an adapter between the APAS-95 docking standard and the International Docking System Standard (IDSS))-3 is moved to the nadir(down, towards the Earth) port on Unity to prepare for the upcoming arrival of the Chinese segment core module.
Q3 2027: The first Chinese module docks to the ISS. Shenzhou crews augment the ISS crew complement, but Dragon flights are reduced with the lost docking port, keeping the crew complement at 13.
Q4 2027: The ISS Assembly Logistic Facility is launched and attached to the Z1 truss.
H2 2027: Ground based spin drive endurance testing begins. Dozens of spin drives are operated without Astrophage to test for failure modes in the moving parts and electronics. One spin drive is operated with Astrophage at full thrust. To limit wasted Astrophage, the spin drive exhaust is directed at a special Astrophage breeder and enricher.
Q1 2028: IBDA(International Berthing to Docking Adapter, adapter from CBM to IDSS ports)-1 is installed on Harmony’s zenith CBM(Common berthing mechanism, a module attachment standard used on the ISS).
H1 2028: Two additional Chinese module launches complete assembly of the Chinese segment of the ISS, adding additional crew quarters.
H1 2028: Docking adapters are installed on the Prichal and Poisk modules. Additional Shenzhou and Crew Dragon missions using the adapters bring the average ISS crew complement to 20.
Q2 2028: The spin drive and beetle prototype, Yoko, is launched on Electron for spin drive trials. The launch is called “Blueprint for a Sunrise”
H2 2028: The first module of the Hail Mary, the airlock and docking tunnel, is launched and docked to the ISS.
H1 2029: The Core Node module is launched.
H1 2029: Canadarm3 is launched to aid in the assembly of the Hail Mary.
H1 2029: Multiple launches of the central spine. Spacewalks begin assembling the trusswork out towards the future fuel tank stacks.
H1 2029: The interstellar Beetle prototype, Pete, is launched on Electron mission “Best of Five”. It accelerates to 0.3c and deploys a foil sail to characterize the dust in the Oort cloud.
H2 2029: Ten fuel tanks are launched and integrated.
H1 2030: SpaceX begins launching Astrophage fuel tankers, which begin collecting in an orbit a little higher than the ISS.
2030: Two thirds of the fuel tanks are launched and integrated.
2030: The wing centrifuge tethers are launched and integrated.
2030: The inner lab module is launched and integrated.
2031: The living wing, engineering wing, and remaining science wing modules are launched and integrated.
2031: The remaining fuel tanks are launched and integrated.
2031: The propulsion housings are launched and integrated.
Early 2032: The Hail Mary performs two test flights. The first tests the centrifuge in medium Earth orbit. The second performs a full shakedown of the life support and propulsion system on a Venus flyby, both with a minimal Astrophage load.
Mid 2032: The hundreds of Astrophage fuel tankers begin rendezvousing with the ISS to fill the Hail Mary’s tanks.
Late 2032: The habitation section is fully outfitted with lab equipment, engineering materials, food, and additional equipment.
Late 2032: Launches and spacewalks focus on assembling the interstellar shield.
Early 2033: The data storage facilities for the Human Knowledge Project are launched and integrated into the central spine.
Early 2033: Primary assembly of the Hail Mary is completed. Crews focus on additional full system tests while final cabin configuration is performed.
April 2033: The Hail Mary crew launches to the ISS aboard a Crew Dragon. A separate Tianzhou spacecraft launches their personal effects and last minute cargo.
April 2033: After final tests, the crew boards the Hail Mary and close the airlock hatch. ISS crewmembers prepare to detach the docking tunnel from the Hail Mary.
April 2033: The SACAS(Station Attitude Control Augmentation System, attached to the Hail Mary to aid in the attitude control of the ISS during assembly) are detached from the Hail Mary and stored on the ALF(Assembly Logistics Facility, storehouse for Hail Mary components on the ISS). Held by Canadarm2, the Hail Mary undocks. Awaiting spacewalkers install the final piece of the Hail Mary, a cover with integrated grab bars over the docking seal on the Hail Mary’s airlock.

Launch of the Hail Mary

A little under seven years after the start of the project, the Hail Mary begins its interstellar voyage. The crew performs final systems checks in LEO before ground crews give the go for launch. Crew Dragon C213 Grace flies in formation with the Hail Mary during the checkout period.

“The crew of the Hail Mary confirming they are now strapped into their seats for initial departure. The three only moments away from the start of their long, long journey to Tau Ceti.”
—
“You just heard Canadian Space Agency astronaut Jenni Gibbons confirm to Mission Control Houston that Canadarm2 is latched onto the Hail Mary. The astronauts out on EVA are now waiting to start the disassembly procedure for the docking tunnel between the Hail Mary and the station.”
—
“Houston now giving the go-ahead to Koch, Parmitano, and Li to start unscrewing the bolts on the docking tunnel that has been holding humanity’s first interstellar spacecraft to the ISS.”
—
“Koch and Li are reporting that the Hail Mary is now separated from the forward docking port of the station. Parmitano is keeping watch on the robotic arm’s hold on the ship. Gibbons will now very slowly separate the Hail Mary from the station in what will be the most taxing operation ever performed by a robotic arm in space. It is better to think about the operation as moving the entire ISS away from the Hail Mary, rather than the other way around, because the Hail Mary with its tanks full of Astrophage is by far the heaviest object we’ve ever put into space.”
—
“Mission controllers around the globe are now polling for release. The crew is reporting that all systems on board the Hail Mary are healthy and nominal, and now the mission commander is giving his go. With the docking tunnel now detached from the ship, the crew of the Hail Mary are set for their heroic one-way journey to Tau Ceti, carrying the hope of billions on a critical mission of research and discovery.”
—
“Houston is in agreement, and the flight director has given Gibbons the go-ahead to release the Hail Mary. A project of true global significance, years in the making, the Hail Mary is now finally free to begin its journey to the stars.”

Rob Navias, NASA Webcast — April 2033

Fully loaded for the first time, the spin drives all come up to full power together, and the ship settles in at 1g acceleration. Within an hour the Hail Mary passes the GEO belt. Within three hours it passes the Moon. After five hours, the ship has left the Earth’s hill sphere. In two days the Hail Mary passes the orbit of Mars. Within a week, it passes the orbit of Saturn. After just over two weeks, the Hail Mary is through the Kuiper Belt.

In less than a month the Hail Mary passes the Sun’s heliopause and enters interstellar space, quickly passing the Voyager spacecraft. As it does so the Hail Mary exceeds 0.08c with measurable relativistic effects. The Hail Mary is travelling 0.25% slower than Newtonian mechanics would predict based on the cumulative acceleration, a difference of 58km/s. Communications with Earth slow to a trickle, then down to a simple beacon, before fading out entirely. Everything now lies on the shoulders of the brave crew of the Hail Mary.

Additional Considerations

Twitter read-along — Pt. 6: Extras, Rejections, and Plot Implications
If you are following the Twitter read-along, you are in the right place. If you need to catch up or are just here to read the whole post, start at the top.

National Flags and Other Symbols

As construction of the Hail Mary progressed, several stakeholders in the program began pushing for the inclusion of their national flags. Initially, no consideration was made to the incorporation of flags and other nation-state symbols, due to the political nature of the process and the certainty of pointless international bickering distracting from the real work.

“Fine, I’ll put your flags on the ship.”

“That’s good to hear, we will start a subcommittee to—”

“But I’m deciding where and in what order the flags are going to be. Does that work for you?”

“That’s a bit—”

“Does that work for you or not? Otherwise there will be no flags. And if I hear any more complaints about flags from anyone, there will be no flags.”

“Yes, that will work.”

“Good.”

Excerpt from an online Petrova Task Force plenary meeting with member state dignitaries and Task Force leadership.

Concessions on the flag request were eventually made and the national banners from the prominent participants were placed on the ship in English alphabetical order. This also included the placement of space agency insignias and logos along the central spine of the ship. Due to the limited space, these were kept to the largest participants in the program and were also arranged in English alphabetical order.

“So I heard you were chatting with the talking heads about flags?”

“Ugh, even at the end of the world, the governments want their prestige.”

“And you’re gonna give it to them?”

“It’ll be more of a headache to have them keep asking. I’m picking which flags and in what order they go in though. No more committees.”

“Oh, I’m sure they won’t particularly like that.”

“And I literally don’t care, I just needed them to stop bickering.”

“How will you pick the order?”

“Maybe I’ll roll some dice or something.”

Private discussion between PHM team leads.

Manufacturer and corporate identifiers were largely kept off the Hail Mary, as this would have further distracted from the project. Any inclusions that could be found on the vessel were all coincidental and not intentional as part of the Hail Mary’s construction and design.

One of these, interestingly, was the Canada wordmark on the Canadarm3 robotic arm, which slipped through the cracks of checks and reviews, and was not noticed until the Hail Mary’s departure. Whether it was intentional or not, the Canadian government was particularly boastful of this fact to the consternation of the other participating nations.

Rejected Hail Mary Concepts

Many ideas were explored by the teams working on Project Hail Mary. Good ideas, bad ideas, wild ideas, and even crazy ideas. A few of the rejected project ideas have been recorded here.

Design Revisions

Revision 0 — (Triple Core Stack - Book)

Simple, achievable, but the 180° rotation of the hab for centrifuge mode and the vertical alignment of the modules is undesirable. The limited volume and lack of external cargo are serious problems as well, severely limiting capacity for Astrophage science at Tau Ceti.

Revision 1 — (Movie)

While this design improved on the need for more internal volume, the 90˚ rotation mechanism was deemed even more complex than revision 0’s 180˚ system. Moreover, the right-angle orientation of the ship’s design would necessitate internal systems that could operate at perpendicular orientations. This would have negative effects on crew productivity and livability, as well as introduce needless complexity into the internal design.

Revision 2 — The “Flying T”

Solves the space and orientation problem of Rev 0, but still requires a 180° pivot mechanism, which would seriously cantilever the hab modules.

Revision 3 — Drop Hab “Ring”

Central vertical fuel and propulsion section surrounded by a habitation ring. First design with a drop hab, removing the pivot, but the hab section proved hard to structurally support.

Revision 3.2 — Drop Hab “Quad-lobe*

A further refinement of the drop hab design, nestling the hab inside of multiple fuel and propulsion stacks. Habitation modules are now regular cylinders.

Revision 3.5 — Drop Hab “Tri-lobe”

The near-final configuration that became the official design of the Hail Mary.

Interstellar Communications

The Hail Mary very rapidly exits communications range on its trip to Tau Ceti. However, a concept was floated that could allow one-way interstellar communications. Nothing could be sent from Earth that would be receivable by the Hail Mary, but theoretically the light output of the Hail Mary’s spin drives could be powerful enough to be detectable from Earth over 11 light years away. The spin drives would need to operate at full power on a nearly empty ship, so half the spin drive banks would need to be relocated to the front of the ship so that the thrust could be cancelled out. Otherwise the thrust would crush the crew and ship at 10-20g.

Detecting the light at Earth would also require a specialized space telescope with a starshade to fully block out the light of Tau Ceti while imaging the rest of the Tau Ceti system in mid-infrared(A lower frequency of light below visible light), looking for the Petrova frequency. The Hail Mary would carefully point towards Earth, and encode data by modulating the thrust of the spin drives.

Several problems kept this idea on the drawing board. The added complexity for the ship structure and the relocatable spin drives made the concept difficult. Requiring a bespoke and complicated space telescope that could take a decade to develop while the world fell into an ice-age certainly didn’t help either. Even if the signals could be sent and received, by the time communications arrived from Tau Ceti, the beetles would be only a couple years behind, limiting the utility of any communications at all. Regardless, unmodified spin drive exhaust would not actually be detectable, despite the power output being sufficient. The exhaust would not be sufficiently co-linear—nor would it be coherent—to be detectable. Fixing those problems would necessitate another blank slate Astrophage engine design with much more difficult requirements.

Proposal to Relocate the Chinese Space Station

While the additions and modifications to the ISS make it far more capable of hosting a sizable assembly crew, the limited space and aging modules pose operational risks to the Hail Mary program. Launching additional modules beyond those of the Chinese Orbital Segment was considered, likely built by American industry based on designs for NASA’s Commercial LEO Destinations program, but the timelines for development were not deemed worth the utility.

There is, however, another fully functional space station in Earth orbit, Tiangong - the Chinese Space Station (CSS), which is a near mirror of the Chinese Orbital Segment on the ISS and the original destination for those modules. If it could be repositioned to the ISS it could double the size of the Chinese segment, and add a fourth airlock for spacewalks. The issue is that Tiangong is in an orbit from which it is prohibitively expensive to match the ISS’s orbit. However, Astrophage is so energy dense that a spin drive powered tug could easily move Tiangong to the ISS, which could be achievable mid-way through the Hail Mary’s construction.

“Okay, well how about we move some of the work to Tiangong. Build out some of the Hail Mary there? We then build some spin drive powered tugs and haul the finished parts to ISS for final assembly.”

“That’d mean duplicating our shipyard facilities at CSS. It was already a lot of work getting the first set to the ISS. It’d solve our logistics bottleneck, sure, but we’re introducing more stuff we have to build and send up.”

“One step forward, two back… we’re getting nowhere with this.”

“At this rate, we should just send that spin drive tug to Tiangong and bring the whole damn thing to the ISS.”

Silence in the meeting room

“Can we do that?”

“Uh… while it’s certainly possible and it’d resolve a lot of our logistic pain points…there other things we’d need to look into—”

“Then go look into it. I want every feasible option available to us. If it gets us to launch faster and speeds things up, do it.”

Petrova Task Force Leadership during a conference call with the PHM(Project Hail Mary) Construction and Logistics Committee

In the end the concept was passed over, as ISS(International Space Station) logistics were proving sufficient, and China did not want to expend the resources necessary to keep Tiangong operational in the meantime while also supporting far more activity on the ISS than Tiangong had previously required.

Beyond the Hail Mary

The Petrova Task Force’s mandate did not end with the launch of the Hail Mary. With an imminent ice age, the Task Force—and the rest of the world—had no shortage of work to do to protect the human endeavour.

Energy and Astrophage Production

Due to the extreme energy density and its potential for abuse by bad actors, Astrophage and its production is kept under tight control and oversight by the Petrova Task Force and the International Atomic Energy Agency.

After initial experiments determine Astrophage breeding and enrichment procedures, full scale electric breeders are built in the Gobi desert, using solar powered electric resistive heat for enrichment. Astrophage management techniques mature rapidly, but the scale and productivity of the breeders lags significantly behind the project requirements.

Flame based breeders are the next development, with natural gas and oil burning variants dotted across the Middle East, especially Saudi Arabia. Wood burning breeders are set up in the Amazon rainforest, where large scale clear-cutting accelerates to provide the fuel.

Eventually, mass produced solar electric and solar absorbing black panel based breeders cover much of the Sahara, Gobi and Arabian deserts, which combined with the burner breeders are sufficient to fuel the Hail Mary in under six years.

In terms of human and industrial effort and capital, the production of the Astrophage fuel represents the vast majority of the entire Project Hail Mary. The development and manufacturing of breeders is predominantly undertaken in China, while operation of the breeders is primarily local to the installations, and transportation of the produced Astrophage is managed by various militaries, especially the United States Navy, as most Astrophage is eventually delivered to the port in Cape Canaveral Space Force Station, Florida.

The total energy captured into Astrophage for the Hail Mary is approximately 1 yottajoule, with production needing to reach around 12 PW for the final three years of the project, nearly 700x pre-Astrophage energy production levels.

Author’s Note: I… I’m sorry. This can’t be hand waved away. The required scale of Astrophage production simply is not feasible. We are talking about achieving 5% the capacity of a Kardashev type I civilization within 3-4 years. Breeding would need to utilize around 5% of the total solar energy hitting the Earth, just to make fuel for the Hail Mary. Even with the simplicity of black panels (from the book), even scaling down to the ship in the book (⅙ the fuel mass), there simply isn’t a way to produce the amount of Astrophage needed on a short timescale. The enormity of the task is severely underplayed in the source material, which does in fact make a big deal about it. Over a long timescale, breeding on Earth and in orbit can make sense. Over a long timescale, harvesting enriched Astrophage from the Petrova line can make sense. However, nothing makes sense for the timelines of the book, movie, or Petrova ‘26. We are talking about a scale of Astrophage production that would actively cool the planet faster than the dimming of the sun (during the years of peak Astrophage production). I was going to write about how the breeders could be kept online to build up energy reserves for future use. I was going to write about Astrophage power plants that could achieve nearly 100% efficiency by using waste heat to breed and enrich more Astrophage. I don’t really see the point anymore, so uh, lets all pretend this just works out like in source material, eh?

Climate Control

After over a century of unintentional anthropogenic climate change, the impending ice age is need enough for intentional anthropogenic climate change. All greenhouse gas reduction treaties and legislation are rescinded and replaced with measures designed to accelerate the release of greenhouse gases to partially counteract the expected cooling of Astrophage induced solar dimming.

The long term effects of GHG(Greenhouse gas, contributors to the greenhouse effect that causes global warming)s are not trivial, and high atmospheric CO2(Carbon Dioxide) levels have serious implications, but the short term danger of Astrophage is more urgent than the potential long term effects of high CO2 concentrations in the event that the Astrophage problem is solved. To that end, the release of CO2 is fully encouraged, but short lived higher potency GHGs are preferred. Methane is particularly desirable due to its abundance both as natural gas and dissolved into polar ice sheets. Capped gas wells are opened to release residual methane, flare stacks are swapped for direct exhaust where safe to do so, and new gas wells are set up to intentionally release methane directly into the atmosphere.

Even more useful for direct climate control are artificial GHGs including hydrofluorocarbons (HFCs) used in refrigeration systems. With a short atmospheric lifetime of less than two decades and a GHG potency of thousands to tens of thousands that of CO2, intentional release of HFCs can have an outsized but temporally limited effect. End of life refrigeration systems are now intentionally drained into the atmosphere, and HFC production is increased to be stored for release when global cooling is worse.

Solar Flux and Orbital Mirrors

The ever increasing Astrophage population around the sun absorbs an ever increasing percentage of the sun’s output, reducing the total solar flux hitting the Earth by a commensurate amount. With no way to increase the irradiance of the sun, the only other option to increase Earth’s total solar flux is to increase the effective area of the Earth, such as by using orbital mirrors.

Despite its global dominance in aerospace, SpaceX’s only direct role in Project Hail Mary is the continued use of its operational Falcon and Dragon capabilities. Instead, under the direction of the Petrova Task Force, SpaceX focuses R&D effort on the continued development of Starship for the primary purpose of launching a constellation of mirror satellites. The Starlink production line is adapted into a mirror satellite production line, with the goal of deploying millions of mirror-sats over a period of 15-20 years, increasing the effective solar insolation on Earth by 1-2% above baseline.

The Starshine constellation lives in Sun-synchronous orbit, primarily reflecting sunlight over the terminator, extending pre-dawn and post-sunset twilight. Per-satellite mirror pointing allows for greater reflected light on cities, farms, solar farms, greenhouses, and anywhere else that the extra sunlight is advantageous. Where useful, low albedo terrain is targeted in place of high albedo terrain to maximize captured energy.

Arctic and Antarctic researchers pinpoint weak points in the ice sheets. Because locations in higher latitudes receive more reflected light from the constellation, these locations can be targeted with higher than normal solar radiation, ideally leading to large chunks of the ice sheets breaking off to melt in the ocean, releasing trapped methane, and reducing the planet’s average albedo.

“And we have liftoff. Go Starship, go Starshine group 10-47. Another batch of 80 mirror-sats to Sun-synchronous orbit.”

NASASpaceflight livestream — mid-2035

Following the launch of the Hail Mary, China begins its own orbital mirror program, focusing on high altitude eccentric Sun-synchronous orbits for longer nighttime passes, with greater visibility over China during the night. Much to the chagrin of other nations, China’s constellation prioritizes reflecting light on China itself, especially cities and farms. When not over China, the mirrors orient primarily for best station keeping.

Mass Produced Urban Farms and Greenhouses

With the spectre of total global crop failure looming greater with each passing year, the Petrova Task Force and partners begin work on a complete reconfiguration of the world’s agricultural industry.

As with the development of humanity’s first interstellar spacecraft, vast resources are directed into work on efficient and scalable urban greenhouses and vertical farms. Biotech companies start work on developing genetically optimized staple crops that would be suitable for urban agriculture. Agtech firms, once at the fringes of farming technology and innovation, are thrust into the spotlight and given unprecedented funding and industrial capacity to manufacture and construct urban agricultural centers all over the world.

These urban agricultural centers are centralized within major populations, and are climate controlled to allow for the genetically optimized crops to grow in relative safety, irrespective of the declining climate outside. Their proximity to major urban centers allows for improved logistics and distribution.

Many of these “agri-centers” utilize solar collectors to maximize sunlight capture, as well as enabling integration into the Starshine megaconstellation, allowing for increased productivity. In situations where the form factor of the agri-centers can’t make use of solar collection, photovoltaic solar arrays and other power generation is utilized to allow for the growth of food with artificial lighting. Even in these cases, the implementation of Starshine allows for additional solar power generation where feasible, enabling more urban farming capacity in non-optimal climates.

Lab Grown Meat Initiative for Protein Replacement

Along with transforming the plant sectors of the agricultural industry, funds and resources are directed towards animal-based protein replacements.

The forthcoming collapse of the global food supply chain would not only mean lost calories for humans, but also catastrophic loss in the global animal feed supply, and thus a substantial reduction in the production of animal-based protein that a substantial portion of the world population relies on.

As a result, efforts in developing novel forms of lab-grown meats receive fresh support to try and supplant the need for livestock, ensuring whatever remains of the global food supply can be directed towards people.

Implications for the Plot of Project Hail Mary

The purpose of Petrova ‘26 is not to create a ‘fixed’ Hail Mary, but rather to imagine how a ship could be built by today’s aerospace industry if the setting of the Hail Mary were to occur. This has resulted in some design decisions that interfere with the pre-existing plot of Project Hail Mary. Where appropriate, we have justified alternative design decisions to enable major plot points to still occur with some variation. Each of these next sub-sections looks at a particular change in isolation, whereas the anticipated storyline of the Petrova ‘26 Hail Mary would presumably be significantly different to the Project Hail Mary book and movie.

To Coma or Not To Coma

No known means of safe long duration human stasis is currently available, so the comas used in the Hail Mary book and movie were not something we sought to enable or enforce. If such coma technology were available, the Hail Mary could of course support crew stasis by reorganizing the dormitory module, but the ship is designed to allow for over seven years of active crew time en route to Tau Ceti. This is accomplished by packing supplies throughout the entire science wing as well as under many of the floors, and by disposing of generated waste through the airlock, clearing out the space before arrival at Tau Ceti.

Of course, no coma means the entire plot of Project Hail Mary would change, Ryland Grace wouldn’t get amnesia, the other crew wouldn’t die mysteriously in their comas, and Grace wouldn’t be on the crew at all since the coma resistance trait wouldn’t be a crew requirement.

Docking to Blip A

Since the airlock hatch is inline with the direction of spin gravity, it would be impossible to spin up the centrifuge while docked via the airlock hatch to the Blip A as is done in the movie.

However, it could also be possible to modify the hazardous material closet to serve as a docking location, especially since it includes the necessary valves to operate as an airlock. The major downside is that the closet is a single hatch airlock, meaning there would be no vestibule within which to switch air, which would necessarily require changes either to Rocky’s docking tunnel or to the initial narrative of Grace exploring the tunnel (he would need to pressurize it with air from the Hail Mary). Since the closet is designed to be removed in flight, it could also serve as the actual berthing mechanism between the two ships, disconnecting for the trip to Adrian, and reconnecting once they are back using the HMRMS(Hail Mary Remote Manipulator System, Canadarm3 and attachments and fixtures) and grapple fixture on the closet module.

Regardless, spinning the Blip A to match the Hail Mary while docked is ludicrous.

Fishing

The abundance of materials and external mounting points on the Hail Mary enable other possible designs and concepts of operations for the Adrian sampler. Consider the following possibility.

The exposed pallet can serve as the “fishing dock”, using the grapple fixtures as mounting points. A complete self-contained system can be installed, with spools of chain mounted to the sides or top of the pallet and the main mechanism and winch mounted off the end of the pallet. With the winch pre-installed and a catchment for the sample container, there would be no need for a spacewalk during sample collection, only for a later spacewalk to retrieve the sample container to bring it inside.

The flying configuration of the Hail Mary could be a sort of horizontal slide in the upper atmosphere. The Hail Mary would lower its orbit, then it would brake as it approaches periapsis, slowing down while tilting vertically to counteract gravity. Once slowed to a suitable velocity, perhaps 0.5km/s horizontally, the Hail Mary would be effectively hover-sliding with a purely vertical thrust vector. Lowering the sampler while under thrust will ordinarily put the sampler and chain directly into the spin drive exhaust, as the ship feels acceleration directly along the thrust vector, so the thrust vector needs to be misaligned from the direction of spin drive exhaust. This can be accomplished by activating the outward facing RCS(Reaction Control System, gyroscopes and thrusters for controlling a spacecraft’s spin) spin drive banks at high power on the same side as the exposed pallet, which tilts the thrust vector by 10-15˚ degrees. To counteract the induced rotation, the three main spin drive housings adjust their output, such that the far housing—across from the exposed pallet—is firing at a higher thrust level to perfectly counteract the torque of the RCS. To avoid cooking any specimens before sampling them, the ship is tilted so that the main exhaust is firing back along the path of travel, behind the lowered sampler.

The uneven thrust will put unexpected strain on the Hail Mary’s superstructure, even aside from the risks of flying through the sparse upper atmosphere and alongside the ionized trail of plasma from the exhaust interacting with the atmosphere.

Accident over Adrian

The Hail Mary lacks jettisonable fuel tanks, both due to the ship’s geometry and also because it seems like a system that costs mass and adds minimal risk reduction. That being the case, the uncontrolled spin due to a fuel migration after leaving Adrian’s atmosphere can’t be solved by jettisoning the fuel tanks on the Petrova’ 26 ship, as is done in the book and movie. The same problem and solution path can instead be achieved via a punctured ATG. The several kilograms of heatsink Astrophage have plenty of energy to spin up the Hail Mary, and the jettison mechanism for the ATGs is reasonably justified given the potential for a self-reinforcing overload in an ATG, something which should be impossible inside an intact fuel tank.

Taumoeba Contamination

The Hail Mary is more resilient to Taumoeba contamination than in the source material. All fuel and power generation Astrophage is physically disconnected from the habitation modules. This separation makes the power loss and fuel tank contamination in the source material very unlikely, if not impossible. The only Astrophage likely to be directly exposed to the cabin atmosphere would be samples stored for experimentation. Much like in the original, the crew could discover the dead experiment Astrophage by the smell of decay.

It might be possible, despite being fully sealed away, for Taumoeba to reach the Astrophage used for climate control. This would result in a nearly complete loss of temperature control in the cabin, as only the ARS(Auxiliary Radiator System, backup thermal management for the Hail Mary), which is intentionally undersized, would be available to cool off the hab section. This would require limiting power use in the whole cabin, including lab equipment and computers, likely including the Hail Mary AI.

“Is it just me or is it getting hot in here?”

“What do you mean, question. My air is normal temperature, statement.”

Onboard Audio Recording in Hail Mary Crew Support Wing

Reusing the Interstellar Shield

The interstellar shield is absolutely critical for any interstellar travel, so for the Hail Mary to return to Earth or travel to Erid, the shield would need to be re-attached to the front of the ship. The shield is jettisoned upon arrival at Tau Ceti, and likely at a significant distance. In the situation where Rocky repairs the Hail Mary and refuels it for a return journey, both ships would need to navigate to the shield where Rocky could determine a method of reattaching it, perhaps with some repairs if any parts of the Astrophage layer are in particularly bad shape. The Hail Mary should maintain enough trajectory information to determine the approximate location of the shield, and a combination of visual surveys and radar (perhaps boosted in power and range with the communications dishes) could allow the shield to be found.

So Long and Still No Fish

I hope you have enjoyed this deep dive into the Petrova ‘26 project. Chance and I have had a blast putting this all together. There is so much more that could be explored, but that will have to wait for another day.

We do have some further reading for those interested. There is a notional ISS schedule spreadsheet. It isn’t perfect, and we haven’t kept it totally up to date with the timelines in this post, but it gives an idea of what the launch and assembly schedule might look. You can also take a peek at my calculations spreadsheet, where I ran a bunch of the numbers on mass, transit times, centrifuge tether length and spin-rate, and more.

All the fantastic imagery in this post would not be possible without my collaborator Chance Wen and his excellent work designing and modelling the Petrova ‘26 Hail Mary. Many more renders are available on his Twitter and ko-fi, primarily following the journey of the Hail Mary on a book-like plot.

As always, please share your feedback, either in the comments below, or by tweeting at me (@immabed) and Chance (@wenchance). Tell us what you liked, what you’d have done differently, and what we got wrong. Keep your eyes on our Twitter’s as well, as there may still be some related content coming.

Disclaimers: Although many of the people and organizations mentioned in this post are real, their depictions in this post are entirely ficticious.
The only AI used for Petrova ‘26 was occasional AI search engine summaries to sanity check my research, and generative fill tools for photo manipulation. Petrova ‘26 is a human-made project.

And this concludes the Twitter read-along! Thank you for following along all the way to the end. Let me know if you enjoyed the read-along format.