Webb flies Ariane 5: watch the launch live on 25 December
esa.intI do have a question about JWST that I wasn't able to find a fine answer in other forums.
A lot of people and engineers are saying that the JWST is a marvel of engineering, with truly inovative technical solutions and a giant step up compared to Hubble Telescope. And it does seems like so!
However, I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if even one of them fails the whole mission could fail.
I know that each step has probably been throughoutly tested, and that the acceptable probability of failure of each one of those steps has been deemed acceptable. But I'm still surprised that people are proudly conflating excellent engineering with a design that has a large number of spofs.
In my domain this would be considered as a terrible design (aka "hope is not a strategy"), even given the constraints of mass and volume that such project incur: 200 hundred low probability events, chained, can get in the realm of possible.
I can't imagine JSWT team doing "bad engineering", so I'm sure I'm missing a piece. Is it only PR that underline this aspect? Is JWST as brittle as the news want to make us think? Or are there technical reasons or acceptable failure modes that gives confidence that those steps are not as critical as the news let us people know?
I suggest the book "Failure is not an option" by Gene Kranz, an Apollo flight director (played by Ed Harris in Apollo 13). He describes how the primary work of flight controllers in all missions is risk management. You are constantly balancing mission needs, fuel needs, mass needs, temperature needs, and etc etc.
I don't think that a raw metric of the number of SPOF is the right way to measure the risk of this spacecraft. It's a fun term for PR purposes (and emphasizing the risk here) but the actual risk posture is more complex.
I imagine that in the course of developing this, they worked out a possible strategy without all of those SPOF - but doing so doesn't eliminate the risk, and the impact to mission is likely massive.
What I don't understand is for $11 billion - can't we do 3 $3B space telescopes that work reasonably well? Spread risk? More science?
Let's say a Falcon 9 launch is $90M. Falcon heavy let's say $200M.
So you take your 3x $3B. Put $200M/instrument into launch, have $2.8B per telescope leftover.
There just seems to be something wrong that it costs THIS much to build a telescope.
That said, the Thirty Meter Telescope is also a sort of "forever" job, the delays have stretched on and on.
I wonder if you did something like bid out and paid just on performance instead of this forever cost reimbursement thing. Right now if you can get onto one of these mega projects, and can stretch it out with delays, it basically can cover your career (ie, 20 year projects).
There are many people in NASA and around that have made similar arguments.
I think the real reason that they never have a lot of traction, sadly, is that if you propose 3, Congress will give you 2. And then when 2 are over budget, it will get trimmed to one. Better to propose one big mission and get it to the point where it can’t be cut easily.
Yeah when you have a fickle funding source often the only way to get any long-term project done is to make it too big to fail, but then you see all the other terrible waste, corruption, etc. that accompanies that.
I'd bet that the vast majority of that cost isn't going to be materials -- it'll be staff time to design and optimise the telescope and make something that can work, including where necessary how to make new materials or processes to make that telescope. I'm not saying the actual hardware is cheap by any stretch of the imagination, but making three different telescopes isn't a linear function of that budget. They're literally pushing the envelope of what's possible here. If something terrible happens to the rocket, lots of forms will be written and people will be sad but fundamentally I think they'll build something a bit better on a few years and nail it. A bit like New Horizons (awesome Mars rover) vs Beagle 2 (awesome Mars rover that died on arrival to Mars).
The seemingly costly part of JWST - The Gold Mirrors are cheaper than one might guess, for eg. it’s a 0.1 micron coating that only used 45g of gold.
The material cost for a lot of "high technology" things can be very small, but the process is expensive. For example fancy chips are only some x grams of silicon, and expensive inverted mesa quartz crystals might cost a good bit while only being x microns thick piece of quartz..
JWST is driven by the size of the mirror, the need for an IR instrument and the temperature you need to keep the instrument at to do the observations. Spamming a bunch of hubble-sized instruments up into orbit won't accomplish the same thing. And I don't think you can do space VLBI in the optical/IR or it would have been done already (but I don't know why?).
It is kind of like asking why 5 Ford Rangers can't replace one Lamborghini or something.
The reason why we are barely getting started into VLBI in the IR on the ground (and nothing that I have heard of yet in space) is that the different apertures need to be stable relative to each other with a precision better than a small fraction of a wavelength. (One tenth, one twelves and one twenties are often used, depending basically on which performance drop relative to the theoretical optimum you are willing to live with.)
For radio astronomy, where we do VLBI everyday, we have to handle waves of wavelength 1 cm and position antennas to a precision better than a millimeter. Not easy when the antennas are scattered across the country, but something we can pull off.
For IR astronomy we are talking wavelength in the range of 1000 nanometers to 30 microns. So at the easiest end of the spectrum you would have to position satellites to a precision better than 3 microns relative to each other, while flying on orbit and being pulled and pushed by tidal forces, gradients in the graviational fields and solar wind pressure (which contains turbulent fluctuations). For it to actually work in near IR you would have to get the positioning right to within 100nm.
For comparison: The mirrors of JWST itself are flat to within about 25nm. And in some sense we ARE doing IR VLBI with JWST since we have separate mirror segments that we all position correctly relatively to each other. But doing so we separate freeflying satellites is something we just aren't capable of yet.
PS: Yes, LISA Pathfinder has demonstrated measurements of spacecraft separation down to a few picometer, so we are slowly getting there.
That's kinda what I guessed. So on the ground you can measure the distance between two observatories that are a few hundred meters apart with incredibly high precision and track that over time as the ground under them slowly deforms and moves.
Geodesy is indeed one of the side products of VLBI observations on Earth.
Spamming a bunch of hubble-sized instruments up into orbit won't accomplish the same thing.
It will, and then some, once we get optical interferometry nailed down. JWST is great, and needed to be done, and I'm glad it's finally getting deployed. But if I had an argument to make against it, it would be, "Let's wait until we know how to do this properly. We're not there yet."
That's a weak argument and should almost never be heeded, but it's also not wrong.
> That's a weak argument and should almost never be heeded
Well that's an incredibly strong opinion with almost nothing to back it up.
Maybe it all goes boom tomorrow on launch or the deployment is ultimately completely FUBAR'd and you can feel satisfied with yourself, but I don't buy that your principle is what we should always follow.
Hopefully we start getting data from JWST in a few months and then I invite the scientific community to figure out how to spamcraft optical and IR instruments into LEO and achieve VLBI with them in the future, but we won't have to keep holding our breath for the technical breakthroughs there.
And even as a jobs program and Keynesian stimulus the JWST beats digging holes and filling them up again, even if it all goes boom. Better than building yet another weapons program as well. And the Senate just tacked on an extra $23B to the 2022 Defense Appropriations Act for one year of spending. The $10B that JWST cost over 25 years of the program doesn't really matter at all.
True, I don't disagree with any of that, but:
Maybe it all goes boom tomorrow on launch or the deployment is ultimately completely FUBAR'd and you can feel satisfied with yourself
A more charitable interpretation of my post would read something like this: "If it does go boom, we can either start building a new one now and try again in 20 years, or we can wait 15 years and build multiple better, cheaper ones in 5 more. Meanwhile, maybe a few hundred other researchers can get funded with the same money."
The reason we can't achieve the same resolution as JWST with interferometry has been mentioned in a recent startalk podcast. The distance between the telescopes would have to be coordinated to a precision somewhere on the order of nanometers.
The distance between the telescopes would have to be coordinated to a precision somewhere on the order of nanometers.
That'll happen. It's fundamentally a timing problem, and we can already build clocks that will tell you what floor of the building they're on.
Less hand-wavingly, it's fundamentally a data-acquisition and correlation problem of the sort that was solved long ago for microwave VLBI. Back in the day, the individual stations had their own maser clocks, but now I imagine they're all GNSS-based. It is by no means trivial to go from RF interferometry to optical, or to move the antenna elements from earth to space, but that's the basic approach that will ultimately be used.
I think this is because of how the various constraints work against each other. We need the telescope to be as large as possible to work as well as possible. But the rockets can only be so big (i.e. we're constrained by the largest available booster). The only thing here under our control is how hard we work on fitting the biggest possible instrument in the available payload envelope, and that is exactly what happened.
With a machine this complex I think it's also not easy to crank out multiple copies since I'm imagining most of it is made by hand without the benefit of a production line.
JWST was (re)launched in 2005, the very idea of cheap spaceflight didn't exist back then, so you'd have ended up with three expensive flights. Also consider that the expected cost back then was $4.5 billion.
To make an infrared telescope significantly better they need it in an orbit not facing the sun always. But other types of lower cost projects might be feasible.
Perhaps that is what will happen from now on. But when JWST was initiated, the options looked different.
> Is JWST as brittle as the news want to make us think? Or are there technical reasons or acceptable failure modes that gives confidence that those steps are not as critical as the news let us people know?
There is no room for redundancy in many aspects of the design, unlike, say a Boeing 777 or Airbus A350.
How can you have a redundant heat shield, or primary mirror (two parts of which swing)? I'm sure some computer systems have redundancy and perhaps comms.
But like with a helicopter: how can you have redundancy in the tail rotor?
So with the JWST: there's no way around many SPOFs.
Regarding that helicopter example:
https://verticalmag.com/news/bell-electrically-distributed-a...
Better helicopter example is the Jesus Nut.
"Because it it comes off that’s who you’re seeing next"
The answer to your redundancy question is: Assembly line.
Instead of ramping up a project, and building 1 of something, you would plan to do more than one, and you could iterate over time as you learn. SpaceX is doing a good job of this.
If 1 Webb telescope is valuable then wouldn't 3 or 5 also be valuable?
We have a number of proven space designs at this point: Soyuz, Spirit/Opportunity rovers.
It's really not - just by having more hardware available (at higher total expenses) doesn't make the pool of money available (public research funding) to book time on these things more. These things are one-off, you build a new one if you expect 10x improvement over the old one.
We don't need a fleet of X1 to break the sound barrier for the first time. We do need many Airbus/Boeings to fly people and stuff from A to B.
Note that that is the case with the unique research hardware you cite as well - we're not sending another Spirit/Opportunity, but have graduated to something else.
Soyuz is a different use case, as there is an economic demand to be filled - that's why a private company like SpaceX is in that sector with its Dragon. On the other hand, you don't see SpaceX cranking out Spirits or JWSTs or Washington Monuments.
They calculated that. Building a second JWST would have added 10% to the budget, but the budget committee nixed that.
YOLO (you only launch once).
The JWST only has a planned mission duration of 10 years. If it’s as epic as everyone claims it could be, there must be a follow up mission planned. So even if it fails, we’ll still see a successor at some point.
There are quite a few more telescopes planned, I think the next major one is the Nancy Grace Roman telescope, which is another infrared scope, made from an old NRO telescope. The decade survey called for another massive space telescope to look at the optical and UV spectrums, so Id expect that to be the next truly big flagship telescope.
>there must be a follow up mission planned
https://www.universetoday.com/139461/what-comes-after-james-...
The write up goes into detail on how missions are planned, and what is in line to follow JWST.
Since JWST was delayed ten years the successor will probably be delayed 20 years and launch in 2050.
> They calculated that. Building a second JWST would have added 10% to the budget, but the budget committee nixed that.
Do you have a citation for that?
Intermeshing rotors are interesting as an alternative to having a tail rotor. They are pretty slow & stable, should feather relatively safely as a failure mode.
Does this have a heat shield? It won't re-enter right? It's far too far away for that.
Not the kind of heat shield you would use to re-enter.
The telescope is designed to image very faint sources of infrared light. The problem is that everything (including the telescope itself) glows in infrared. The hotter things are the more infrared they emit. Because of this you want to keep the instrument as cold as possible. (You do this because you don’t want to drown the faint sources by the glow of the telescope itself.)
Now of course there are parts which has to be “hot”. At least relatively to the very cold instruments. The solar panels are heated by the sun, the transmission electronics and the processing turns electricity into heat. The positioning thrusters burn chemicals which makes them hot.
Because of this they designed the spacecraft with two sides, a cold one for the instrument and a hot one for everything else. They even choose the orbit cleverly so they can keep the sun and the earth and the moon always on the hot side of the vehicle.
And then you have this problem that you have to make sure that the hot side won’t warm up your cold side. This is where the heat shield comes into play. Sometimes it is also called a sun shield since the sun is the main source of heat for it to shield against of course, but it also shields the instrument from the heat of the hot side equipments.
Structurally it is a 5 layer lassagne. They just replaced the pasta with metalized kapton tape and the sauce with the vacuum of space. It is about the size of a tennis court, launches folded up and will un-fold in space. Hopefully. :)
Thanks for the detailed answer! I forgot it was mainly for infrared but I didn't think of this implication anyway. Very interesting! I hope we'll see this in the coming days.
It's actually a sunshield [1]
[1] https://webb.nasa.gov/content/observatory/sunshield.html
I think all the SPOF talk is expectation management in case it fails. It's part space telescope mission, part engineering challenge. Even if the space telescope part fails, the engineering effort that's gone into it means something.
They must've calculated that the overall chance of success, and they have a target, and they met their target. Unfortunately, tests and theoretical modelling have a tendency to not exactly replicate a space environment (or any true production environment), nobody's perfect at anticipating everything, and management has ways of manipulating engineering estimates.
The Space Review [1] quotes NASA as saying there are 344 SPOF. They talk mainly about the sun shield, so that's probably the biggest risk, but consider all of them as about equal...
If each SPOF has a 0.1% chance of failure, net success rate is only 71%. Presumably most of the estimated failure probabilities are less than that, and the sun shield—which probably comprises many of the SPOFs—averages (far?) more than 0.1% per SPOF, because everyone seems to be particularly worried about that working.
I wonder what that figure is. Has it been published anywhere? Dear NASA and ESA, what do your engineers say about overall chance of failure?
I hope it's just badly thought through marketing. There is currently a AWS spot during nfl games, that shows a spectacular catch and then proclaims that the catch probability is only 3.6% or something. You are meant to be somehow impressed by the unlikelihood I believe, but that their model thought the catch is unlikely and the guy caught it implies a rejection of their model with p=3.6% < 5%.
The JWST marketing seems to work under a similar premise, they proudly proclaim that they couldn't mitigate hundreds of single points of failure, and you're supposed the be impressed by how difficult their task is. Hopefully the engineering did a reasonable job and the marketing is just playing up the wrong thing.
I don't think you are supposed to be impressed by the number of things that could go wrong. At least, that's not how I see it. They talk about the deployment phase with all these complex things that have to go exactly right as "the 30 days of terror." And that's a pretty accurate description of what many people with a stake in the JWST will be feeling. Not awe, but terror. This is a big part of space missions at the bleeding edge of science and technology, and I think it's great that many people are hearing about it!
It has to fit in the fareing, survive launch stress and vibration, fly further than the moon and it has to weigh 6000 kgs +including fuel. If it works it will be one of the greatest engineering feats of history.
I'm guessing it's a case where all the various extreme requirements simply do not allow for redundancy in the places the engineers would prefer to have it. The options are likely (1) okay performance with a lower chance of failure or (2) extreme performance with a higher chance of failure.
> However, I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if even one of them fails the whole mission could fail.
I'm not sure I've seen anyone who is _proud_ of it, lots of people are just setting expectations. Probably due to the similarities with Hubble (although JWST can self-align it's mirrors!).
It also might be posturing to show how well the thing is built. Space is hard, like really hard, and these agencies keep knocking it out of the park.
Every kilo launched costs a proverbial and probably nearly literal tonne of fuel so things are not as simple as that.
It's also has to fit on the rocket hence the once off folding mechanism. And after deploying it has to be perfectly aligned (remember the Hubble with its slightly off mirror)
I think having redundancy for everything would just not make for a launchable spacecraft.
Unlike say, the Apollo program, which had a guaranteed successful outcome?
The thing to realize is that these are some of the hardest things humanity has tried their hand on and if it all works that's a great thing for all of us, if it fails we will learn something and we'll go back to the drawing board (but we won't have a JWST and that's a significant loss, besides the obvious future calls of 'look at what happened to JWST' which will no doubt have negative impact on finding funding for future space missions).
Also, I think you're mistaken about people being 'proud about the 200 SPOFs', if they could have made it one less they certainly would have because everybody involved wants this to succeed. Think of these as the ones that they simply could not get rid of no matter how hard they tried.
Perhaps it's a case of "we're proud that we got it all the way down to only 200 SPOFs in the final design, the earlier designs were way worse".
There is a fair chance of that, actually. If you start enumerating the ones that are obvious even to lay people (one rocket, one satellite, one set of mirrors and so on) then this is probably an extremely impressive low number.
I've been binging JWST content and definitely recall John Mayer saying in at least one interview that 344 single points of failure was as low as they could get it. And I can believe it. If you watch some of the more detailed interviews, he always stresses how every design choice was heavily labored over and reviewed.
It's an absolutely amazing effort, from the design through all of the problems they had to deal with along the way to seeing it sit there on top of that booster. A few months from now we could be in a completely new era of astronomy.
> Unlike say, the Apollo program, which had a guaranteed successful outcome?
Apollo was wildly dangerous. Apollo 1 killed the whole crew. The contemporary calculated failure odds for a Saturn V launch were 1/8. Compare that to the current Dragon 2 projected LOC risk of 1/276 [1].
[1] https://en.wikipedia.org/wiki/Crew_Dragon_Demo-2#:~:text=NAS....
I think GP was being sarcastic.
Absolutely. Those guys were laying their lives on the line with every launch.
I think this is your earnest attempt at it but its a good place to apply the story from yesterday 'be curious, not judgemental'.
That's literally what he is doing, isn't it? He thought something was off, and instead of spewing his opinion all over the place he requested information from folks more versed in the domain than him. He is literally being curious, not judgemental.
> I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if even one of them fails the whole mission could fail
I see this as judgmental, am I wrong in that?
It expresses an opinion, but I don’t think that has to be judgmental. The OP has to explain their position in order to ask for additional information.
I'd like to apologize if this sounded judgmental. English is not my main language, and perhaps my phrasing sounded like I assumed my domain specific opinion is better than the actual people working on the the project.
Reading the other comments, and maybe to contextualize to my question better, I'm more surprised by how the project is presented as marvelous to the public, rather than thinking that any technical part were overlooked.
While I'm sure that engineering teams at NASA and ESA have countless contingency plans, procedures and failure models. Medias around the project seem to focus on how fragile the deployment procedure is. Great engineering is an act of finding the best balance between opposing constrains, by building technically sound systems but also more importantly designing robust human or automated procedures.
In this story, in my opinion, the media presents a skewed explanation of why the project is incredible by highlighting that it would be incredible that such a brittle deployment procedure would even work.
While a farm tractor might have a factor of safety of 10, spacecraft are usually closer to 1.3, due to mass and efficiency constraints.
Space is hard.
> However, I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if even one of them fails the whole mission could fail.
Genuinely curious: how would you have achieved the mission goals with fewer SPOF?
We're told that since JWT will travel very far away before it unfolds and activates all its systems, there is no practical way to service it if something would go wrong.
Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?
It's a problem of energy and orbits.
To get from low-earth orbit to the sun-earth Lagrange point 2 (where the JWT is headed) takes around 7 km/s of delta-v[0]. That's a lot of speed.
You could try to do this gently enough that the unfurled JWT won't be damaged by the acceleration. This isn't totally impossible, but you'd need a good Hall thruster (ion engine) with a huge amount of reaction mass, since the JWT is so big itself. It would need to run for longer than any other such thruster has. It would need massive solar panels to power it.[1]
Or you could have the original rocket just be bigger, and throw it all the way to the right orbit while everything is packed tight.
[0] https://en.wikipedia.org/wiki/Delta-v_budget [1] I'm guessing at this, but that's my intuition. I encourage anyone to correct me because space is too cool to be upset that I was wrong.
I suspect the deployed structure cannot handle the acceleration required for escape velocity. That also may require much more propellant. Then on top of that, we don’t have the capability for humans to service satellites other than the ISS. So this is all a moot point.
Interesting though.
Does that really matter without air resistance?
Depending on how high you actually bring it. Like 500km away from earth is still an orbit (I think that's Hubble's orbit) but how much force do you need or will happen?
Rockets can easily accelerate with enough force to kill a human (cargo flights and unmanned flights use different launch profiles for this reason).
The less Gs you need to design a component for, the lighter/simpler it can be, so why unfurl early and add that extra mass and complexity to the design?
When rockets are firing lots of acceleration is applied that the delicate structures are only designed to handle when stowed. Think long arms on hinges. They can take acceleration in one axis, but not at 90 degrees to it.
I guess the acceleration needed to leave orbit might need so much more fuel if you need to do it slowly than doing it fast?
Otherwise it would just take longer.
Rocket engines could only be throttled down to certain power and manoeuvring thrusters would run out of propellant way before it reaches any orbit. Maybe something like electric propulsion can do it but it will take very long time to make it practical imho.
The parts of a ship that thrusters are directly attached to experience acceleration first, the other parts that are further out from the thrusters won't accelerate immediately and if the acceleration is too sudden or extreme could be damaged or break off entirely.
And to answer your question in the other response, many thrusters have a minimum thrust, and even that minimum may be too much for the parts when deployed.
By definition, as long as thrusters are firing, you are accelerating.
Acceleration is defined as the change in velocity, and velocity is defined as the change in position (w.r.t. some inertial reference frame). There will always be some bending when thrust is applied at one part of a body; nothing is perfectly rigid.
As an extreme example, imagine a stick one lightyear in length: if we ignite a rocket on one end, firing perpendicular to the stick's length, then the other end cannot start moving for at least a year.
We had the capability in 1993, and could of course develop it again.
A broken JWT could wait a few years in orbit.
That may be true, but designing a mission based off that hypothetical is a bad idea. The reality is we currently don’t have the capability for humans to service satellites, and developing that capability would probably take years and cost >$100 million. And NASA can’t just decide to take on that endeavor, it would require congress and months of political bickering. JWST was designed for what is currently feasible and practical.
> developing that capability would probably take years and cost >$100 million. And NASA can’t just decide to take on that endeavor
So what you're saying is, this could easily be funded by some billionaire, e.g. Jeff Bezos who already sells billions of dollars in Amazon stock per year to fund Blue Origin?
Not saying this should be done privately, but if funding is the problem, that problem can be solved.
Space travel is less expensive than most people think, it just isn't very high up on our list of priorities.
“Maybe Jeff Bezos could fund this” is not a good parameter to design a mission around.
$100M is 1% of what JWST cost.
Looks like a reasonable repair cost (and only if) it turns out to be broken.
It’s still not that simple, unfortunately. Ironically, there are too many single pint failures. Maybe JWST broke in a way that can’t be repaired. Maybe congress doesn’t approve the repair mission. Maybe the repair mission would actually cost $1 billion. Maybe the repair mission fails. Now imagine you’re the mission designer. You could trade increased complexity for some small chance of a repair mission maybe being possible. Or you you could decrease complexity and just accept that repair won’t be possible. The answer becomes pretty clear.
Referring to hubble? The JWT is designed to observe from the Lagrange point in permanent shadow of the earth. It won’t work from earth orbit. First parking it in orbit, and then restarting the engine after unfolding comes with a whole new set of risks and tradeoffs.
What about an unmanned mission to fix it? And maybe to refuel it.
Incredibly unlikely. First, it would have to fail in a way that’s possible to fix. We don’t have robots that can replace screws, solder joints, and polish mirrors in space. Then we’d have to design a brand new spacecraft and mission. That would take years, lots of money, and political will. NASA would likely cut its losses, document the lessons learned, and try again.
I was watching a documentary about James Webb and they claimed that NASA has plans of using unmanned robots to potentially refuel it but no mention of fixing.
But who repairs the repairers?
We probably wouldn’t have a way to service it in earth orbit either. We needed a space shuttle to operate on Hubble. And using some other commenter’s estimate a 2nd JWST would cost 10% of the 10 billion USD price of the first one. A billion dollars is ballpark what it costed to launch a space shuttle. So even if we had the shuttle, would we fix the first one or just build & launch a second one?
Can we crowdfund 3 more this way, I wonder?
Absent all of the other practical considerations, even in LEO, a repair mission would probably be so expensive that it would be cheaper to build and launch a new one instead.
> Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?
Another comment mentioned that it's not designed to accelerate while it's fully deployed, and that's true enough. You'd wreck it.
The other essential thing is that there's no way to give it and its instruments anything like their designed operating parameters (pretty hot on one side of the sunshade, something like 40 kelvin on the other side) in Earth orbit.
Orbiting around earth would require it to constantly course correct / rotate in order to avoid the device from getting to hot from the sun’s radiation - there isn’t enough fuel to “play it safe” around earth for this long since it will be needed at L2.
Let alone the current lack of in orbit service capabilities like we had when the space shuttle was still around.
It doesn't have enough fuel onboard to go from LEO to the Lagrange point itself.
It wouldn't need to, you could park it there a secondary liquid fuel booster attached, and then after the origami shenanigans if it unfolds correctly the second booster could send it away to its final position
I saw some interviews of engineers of the jwst and few of them had similar ideas, or at least to assemble them in leo then slingshot them to their final positions/orbits
What booster would you use?
Another booster up in the fairing? That would need to be quite heavy. It would be a totally custom thing for this specific mission. You would need a suitable storable propellant.
Leave the booster from the Ariane attached? The lh2 and lox would boil off after a few days.
What do you do if the deployment fails? SpaceX's dragon can't do space-walks on its own, it doesn't have an airlock. There would be no way to fix it short of developing a whole new space craft for that task.
For space walk accessibility maybe they should have docked it to the ISS for initial setup before then boosting it to its final point?
ISS is in a very low and eccentric orbit. I think boosting from ISS to a geo transfer orbit, let alone escape, is more expensive than just going straight to escape velocity.
How feasible is a repair mission without the shuttle?
L2 is very far from earth, well beyond the Moon. The Shuttle could never leave Low Earth Orbit, so it's a non-factor in repair missions once JWST is on station.
I believe what was GP was getting at is that even in a "convenience orbit", a repair mission would be very unlikely.
The scenario we're talking about is having JWT unfold in Low Earth Orbit, so it can be repaired there, if need be.
in Armageddon the Shuttles flew over the moon
The shuttle-like craft were explicitly special, more capable craft (visually hinted at by the extra set of boosters and other design differences.)
Not that Armageddon was particularly focussed on reality.
It's humanity's self-unwrapping Christmas present.
Hopefully.
Love it :D
For people in North America 12:20 GMT is...
4:20 am PST
7:20 am EST
1750 IST in India
All the best to everyone working on this tomorrow. Hope you get some suitably generous TOIL in January.
Countdown with links to livestream and blog here: https://www.jwst.nasa.gov/content/webbLaunch/countdown.html
And here I am, feeling nervous about a production web deployment.
Update: the rocket launch went better than my deploy.
Are there alternative streams that anyone here would recommend? The more technical, the better.
A fantastic Christmas treat, best of luck to all the teams involved :)
Will this be visually tracked? Like can we watch it to it's journey?
How much did NASA, ESA and CSA each contribute to this project?
From the JWST wikipedia page:
"In the 2005 re-plan, the life-cycle cost of the project was estimated at US$4.5 billion. This comprised approximately US$3.5 billion for design, development, launch and commissioning, and approximately US$1.0 billion for ten years of operations.[18] ESA is contributing about €300 million, including the launch.[84] The Canadian Space Agency pledged $39 million Canadian in 2007[85] and in 2012 delivered its contributions in equipment to point the telescope and detect atmospheric conditions on distant planets."
Those numbers are completely obsolete; the final price tag was over $10B.
The CSA is contributing staff to operations as well, afaik.
A more recent source says this (found through wikipedia). Values all appear to be up to launch, and do not include operations.
(No epoch given to dollars; presumably they are 2021 USD)NASA: 8,800m ESA : 850m CSA : 200m ------------ All : 9,850m"Günther Hasinger, ESA director of science, estimated that Europe’s contributions to JWST, in the form of instruments and the Ariane 5 launch, to be about 700 million euros ($850 million), roughly the same as an ESA “M-class” science mission.
Gilles Leclerc, director general for space exploration at the Canadian Space Agency, said Canada’s contribution of an instrument and fine guidance sensors cost the agency about $200 million Canadian ($165 million) over 20 years. “This is an investment in discoveries of the universe,” he said.
NASA now estimates it will spend $8.8 billion on JWST through the spacecraft’s launch."[1][2]
Those numbers line up with a summary the Planetary Society put out.[3] That source includes info on the operations cost, at least for the US:
"The James Webb Space Telescope (JWST) is expected to cost NASA $9.7 billion over 24 years. Of that amount, $8.8 billion was spent on spacecraft development between 2003 and 2021; $861 million is planned to support five years of operations. Adjusted for inflation to 2020 dollars, the lifetime cost to NASA will be approximately $10.8 billion.
That is only NASA’s portion. The European Space Agency provided the Ariane 5 launch vehicle and two of the four science instruments for an estimated cost of €700 million. The Canadian Space Agency contributed sensors and scientific instrumentation, which cost approximately CA$200 million."
All three agencies will supply staff to support operations, which I guess makes sense since they've all contributed different instruments.[4]
[1] https://spacenews.com/jwst-launch-slips-to-november/
[2] https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cos...
[3] https://www.planetary.org/articles/cost-of-the-jwst
[4] https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Par...
Then maybe you should update that wikipedia page.
If you want to skip the Super Bowl pre-game, the actual launch window starts at 7:20 am EST (12:20 UTC) and lasts for 31 minutes.
It can launch anytime during that window.
I can't watch this. So many years and so many man-hours riding on top of a rocket is to much for me.
Similar. But more because I can't believe they didn't build two - for redundancy.
I wonder what time and cost a rebuild would have. Maybe half the original development costs?
The original title “Webb flies Ariane 5: watch the launch live” has a nice ring to it. Here goes!
Personally I hate launching anything around the Christmas period.
LaunchHN: JWST on Christmas
Decades of meticulous planning and they couldn't give their teams a day off on Christmas? Of course it could be that consensus was this beats any other kind of activity that day in which case fair enough. :-)
Well, according to the original planning it should have launched before Christmas. It was only the weather delaying it by one day. I guess once they were ready for the launch, they want to avoid to delay it any longer than needed. Not sure, how long the rocket can be "stored" in launch-ready state before it has to be serviced again.
Newton's birthday sounds like the perfect day for a rocket launch to me
He was born January 4th, using modern calendars.
Oh cool, I get to celebrate his birthday twice per year now. That said, strangely enough, if the calendar changed after my death and people were still celebrating my birthday, I'd expect people to celebrate the day on the calendar I used rather than the accurate day.
Since Isaac Newton was actually born extremely prematurely, at less than 30 weeks of pregnancy, maybe he was the one rushing to match the date of the JWST launch. :P
I think spending Christmas wringing your hands unsure if your $10B decades-in-development baby is going to make it to orbit sounds incredibly stressful...
It's going to be awesome for us to watch but I feel for all the folks that worked on this.
FWIW: given the extraordinarily complicated mechanical design, merely reaching orbit is the "easy part". The real imagined disasters won't happen until the mirrors assemble.
True, though it’s also worth considering that Webb is going far beyond “orbit“ as we generally think of it. I don’t know how much has been launched all the way out to L2 before, but it’s probably an order of magnitude less than what’s in Earth orbit.
> I don’t know how much has been launched all the way out to L2 before...
There is a handy list on wikipedia: https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_po...
Your intuition is quite right, there is way less satellites parked around L2 than in low earth orbit for example.
But that doesn't really pose too big of a challenges in itself. It is of course far, both distance wise and energetically.
The main complication often mentioned is if something is wrong with the telescope it makes it very unlikely that a crew can visit it to fix it. The way for example how they repaired Hubble is unlikely to happen with Webb.
Meh, but there's nothing to hit in space. The energy required to reach a routine geosynchronous orbit is already ~85% of escape velocity. The added boost is minimally more dangerous and the trip is just empty hours. "Time" does kill spacecraft, but not often.
The Webb self-assembly is absolutely where the scary bits lurk.
Yeah valid. Though the whole "hurtling upwards on top of a bomb" part is still definitely scary in it's own right.
Particularly given the launch record of the Ariane 5 platform. I did some quick research, and no modern launch platform has as high a mission failure rate (4.5%.) The Delta family comes close at 4.4%, but that's a 50yr launch history. The Delta 4 iteration has had no failures.
As I wrote elsewhere, the bulk of those failures were in the first 15 launches, after that it was a very long string of one success after another with one partial failure in 2018.
The Ariane 5 is batting 106 for 111 which is pretty good odds and perfectly respectable for a heavy lift vehicle... but not so much so that I don't wish it was launching on an Atlas 5 instead.
Ariane 5 had some early problems, the first failure even became a case study in critical software development. But it had only had one partial failure after the 17th launch: the payload was launched to the wrong orbit because the wrong coordinates were put in the computer. A huge QA problem but not the fault of the launcher which did exactly as told.
Now, both Ariane 5 and Atlas 5 are extremely reliable, mature rockets.
Four of those were in the first 15, the last recent one was in 2018, and was a partial failure.
Lots of European countries celebrate Christmas Evening (Dec 24) more than Christmas Day (Dec 25).
Yeah, 25th is the day to nurse the hangover
I wish for our Canadian friends that the telescope unfurls on Boxing Day.
If you start planning your rocket launches around religious holidays then that is going to be a bit of a problem, there are just too many of them:
How about planning around the single most celebrated holiday in the US, religious or not: https://en.m.wikipedia.org/wiki/Public_holidays_in_the_Unite...
Ariane 5 is a European effort, not a US effort, it will launch from French Guyana, not from the US.
Cool.
Webb will be monitored and operated by NASA in Maryland.
https://en.m.wikipedia.org/wiki/James_Webb_Space_Telescope#T...
https://en.m.wikipedia.org/wiki/Space_Telescope_Science_Inst...
I really don't get your fixation about this: the people involved are all most likely extremely happy to see their creation fly and to have Christmas take a backseat to that.
Let's just hope it all goes well, this is one of the most complex space endeavors we've ever tried, and if it fails it will have many negative long term implications.
I did not get your real or feigned ignorance that Christmas is a much more significant holiday to the vast majority of the people involved than the Feast of the Ass.
I also hope all goes well. Cheers.
I couldn't care less about Christmas, but I do care about the JWST, and I can't wait for first light.
If you worked on something since 1996, do you think you would give two flying figs what day it launches on?
my personal preference is irrelevant. my comment was regarding whether it is tractable to plan around Christmas, or unreasonable because there are too many holidays of comparable significance.
Too many holidays might be a factor but I really doubt it's a large one. The bigger reason is you just don't delay a 20 year $10billion project for any holiday.
Some of the grunts might be disappointed but having worked on way less important things that were launched on holidays, I can guarantee anyone significantly involved in the project is just happy to see it get off the ground no matter what day. You have a good window for launch, you take it
It was scheduled for Wednesday and then postponed for bad weather.
Why isn't SpaceX doing this?
The launch partner/platform wasn't chosen recently and it's part of what ESA is providing as a partner in the program.
"In exchange for full partnership, representation and access to the observatory for its astronomers, ESA is providing the NIRSpec instrument, the Optical Bench Assembly of the MIRI instrument, an Ariane 5 ECA launcher, and manpower to support operations. The CSA will provide the Fine Guidance Sensor and the Near-Infrared Imager Slitless Spectrograph plus manpower to support operations."
https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Par...
"not recently" is underselling it a bit. ESA agreed to launch it before Falcon 9 (let alone the Heavy version) had ever flown.
It looks like it was even before Falcon 1’s first success.
Ariana 5 can transport a larger/heavier payload than Space X rockets. And even then the telescope has to be folded up in this really complicated way.
A fair comparison would be to Falcon Heavy (Ariane 5 uses boosters as well) which has about twice the payload capacity. Just doesn't yet have the launch history required for such an important payload.
The project and the choice of contractors predates SpaceX.
SpaceX wasn't a thing when the project constraints were defined.
Contracts or momentum? Haven't looked at actual dates, but my guess is that this project was established long before SpaceX was a viable option.
ariane 5 has had 111 launches. Falcon heavy has had 3.
the falcon heavy probably didn't even exist when they were drawing up the contracts
I think Falcon heavy is not needed. Webb's weight is ~6200 kg. Falcon 9 is 8300 kg to GTO (Geostationary transfer orbit). This leaves about ~2000 kg fuel equivalent to spare which should be more than enough for the special location Webb is aiming for.
But yes, the contract for the webb launch was probably locked a very long time ago.
(Though it's also possible that Falcon 9's fairing wont be able to accommodate Webb)
Because the contracts were made before SpaceX was deemed reliable.
> Why isn't SpaceX doing this?
Reliability (as in: established track record).
Although, if Ariane decides to explode tomorrow, this comment will look ... odd.
This has to be launched by Ariane - it's constraints are tightly bound to what that platform can do, and it's fairing size. Ariane is optimized for GEO insertion, while Falcon is optimized for LEO orbits. You could have used a Falcon, but a payload like this was actually built around the rocket's capability, and this was designed prior to Falcon being a thing.
All that said it's worth nothing that SpaceX's flight success rate is 98.5 (135/137), while Ariane V's is 95.5 percent (106/111).
The really gobsmaking thing about that is that this is that SpaceX's rate is over 11 years, while Ariane's is over 25 years.
It's time to stop thinking of SpaceX as the plucky, untrustworthy startup.
In the future space telescopes like this really need to be built in LEO, and then boosted to Lagrange points. The number of failure modes beyond the typical rocket / stage / fairing, secondary burns that the folding mechanism and the lack of a ability to test a ton of new technology in zero-g orbit makes this far more likely to fail then anyone is comfortable with, given the overall cost to this.
Does anyone really think of SpaceX as a scrappy startup? You seem to recognize that this mission was designed and set in stone well before SpaceX was established.
I don't know if JWST needed vertical assembly, but I recall that some spy satellites in the past have had to be launched on Atlas/Delta because they need to be assembled on the rocket vertically (vs. being rolled out to the launchpad horizontally).
Important to note that the agreement was made in 2007, so reliability as a factor would be reliability as assessed in 2007, not 2021.
I think that in 2021, Falcon 9 ‘s track record arguably suggests it is more reliable than Ariane 5, but it doesn’t matter because the Falcon fairing is too small for JWST.
Falcon 9 has a better track record than Ariane 5 at this point, but SpaceX wasn't really a thing at the time these contracts were signed.
also falcon heavy would be required which only has had 3 launches (all success though)
Interesting they found a way to add a hidden risk variable to the launch, by sending it up on a day people are having to choose to not be with their families. Have a bad feeling about this :/
“They” didn’t find anything. It wasn’t originally planned for tomorrow. The weather found a way. There’s only so much wiggle room and launch windows.
I didn’t imply they did it on purpose. The they here is in the spirit of Murphy’s Law. Seriously: launching on Christmas seems like a bad and unnecessary source of entropy.
> It wasn’t originally planned for tomorrow
Right, it was originally planned for 2007.
It is sorta funny that after 14 years of delays they picked the week of Christmas.
They didn’t pick that either, it was supposed to launch earlier but a clamp broke down when attaching the telescope to the rocket sending vibrations all over it and and as a result they had to inspect for damages, further delaying the launch. Then the weather wasn’t good and delayed once more.
They did though. It was delayed, they chose to delay it from October to December 18 to December 22 to Christmas instead of like the first week of January or whatever.
It’s not like this thing is launching to Mars and they’d have to wait a couple years if they miss this week - it could launch on 210 days of each year.
https://jwst.nasa.gov/content/about/faqs/faq.html#launchWind...
I don’t mind at all, I just think it’s a bit funny.
So they should have delayed to next year after the clamp issue? Hundreds of people that were on site from Europe and the US, now go back home. You move the JWST back in a safe storage place, moving it is always risky, as the clamp issue showed.
You now plan a new date in January, knowing Omicron is spreading and countries are starting to close their borders once again, and knowing Kourou had to be closed for like 6 months already once because of COVID, preventing any launch.
Do you want to take the risk of your 11B$ payload maybe getting stuck in a hangar for 6 months? Any issue with the ventilation, de-humidifiers or hundreds of other things could potentially damage it.
Then you bring everyone back on site, and now you have to reinspect everything, rocket and payload and restart the whole process, move JWST back again into the assembly tower, again a risky manoeuver, and as always, many things including weather can make the launch window slides for days. Being stuck in Kourou for weeks is not as fun as it may seems.
So no, it makes 0 sense to move the date around for something non-critical, and I'm pretty sure everyone already on site would rather just get it done now and celebrate christmas with their family a few days late, than add unnecessary stress on JWST and themselves for potentially months.
lol
thanks for the treatise on the consequences of a few more days delay, but all I’ve said is that I find it amusing that the launch has ended up on Christmas day. They could have conceivably tried to avoid the holidays, but obviously they are not, and this is fine.
what's funny about it? You think there's anyone working on this project who isn't super excited to see it go up on Christmas?
No better gift than a successful launch. The folks working on preparations overnight surely see themselves as Santa's Elves in some fashion.
Exactly - you highlight the problem. Launching on Christmas introduces unique situational entropy. They should do it later.