SpaceX Falcon rocket explodes on landing after delivering satellite to space
bbc.comSpaceX actually got very close to sticking this landing. Sea conditions were reasonably rough, with 3-meter waves. It's also the first time SpaceX launches in fog, IIRC. Everything about the landing except the stuck leg seemed to be perfect.
So IMHO, the fact that the rocket exploded is not the most pertinent fact about this experiment. The main piece of news is that SpaceX is exceedingly likely to be able to recover rocket boosters intact from sea, even in non-perfect weather conditions.
As a former gymnast, I like the sticking the landing analogy but a human (even on an unstable mat) has far more control over their balance point (we do much of our balancing by bending at the waist - if only the rocket had one).
In any case, I agree that this was very close. I've also spent a reasonable amount of time on "big water" and was specifically watching the attitude of the landing deck with respect to the horizon. I didn't see much movement of the barge (but that doesn't mean there wasn't some instantaneous movement that together with the force of landing exceeded the leg's load rating).
The other thing that's struck me is that the SSTO advocates could end up becoming irrelevant. Who's going to argue we need SSTO at all if we can recover and reuse all the stages anyway? Multiple stages will remain dramatically more efficient (Yes - I know we don't get space planes with two hour flight times from New York to Tokyo quite as easily).
Finally ... I just have to say "I LOVE THIS". I remember as a child watching the Apollo missions and, as an engineer, I haven't been this excited about a project for a long time. Isn't this exactly the type of thing we can rally humanity around? Who's going to argue that it's not a great accomplishment?
The Falcon 9 isn't totally reusable not does it plan to be. It still has a non-recoverable second stage so it's not quite to the point of a SSTO.
Are you sure that there's not a plan to recover the second stage once they've consistently been recovering the first stage? (I'm assuming that would be part of the road-map).
From Wikipedia:
https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...The project's long-term objectives include returning a launch vehicle first stage to the launch site in minutes and to return a second stage to the launch pad following orbital realignment with the launch site and atmospheric reentry in up to 24 hours.However, from other sources:
http://space.stackexchange.com/questions/7814/what-happens-t...SpaceX would love to recover the second stage, which they had planned. But it sounds like they have given up on that.What they are referring to there is a transcript I have been unable to access. It's here:
http://shitelonsays.com/transcript/elon-musk-at-mits-aeroast...
More discussion about it all here:
https://www.quora.com/Could-SpaceX-feasibly-recover-the-seco...
https://www.reddit.com/r/spacex/comments/1zg7zm/how_soon_can...
https://www.google.co.uk/search?q=space-X+recovering+second+...
Seems way harder for way lower returns to recover the second stage. Only 1 engine instead of 9, and you're recovering from orbital velocity which opens up several new cans of worms. Would they need heat shielding? The extra weight there might blow away any cost savings from recovering the engine.
Heat shielding is needed, as well as extra landing engines that work outside of vacuum, since the second stage engine would destroy itself under atmospheric pressure. It's easy to see how quickly you start to get dimishing returns, but it would be cool if they could pull it off.
Some experiments were done in early 2000 with inflatable aerobrake. The concept was shown to work, but experiments weren't a complete success. However this technology I'm sure can be applied to the task of returning the second stage.
https://en.wikipedia.org/wiki/Atmospheric_entry#Inflatable_h...
Or even more futuristic, plasma parachute/heat shield: http://www.nasa.gov/offices/oct/early_stage_innovation/niac/...
It certainly was at the start. https://youtube.com/watch?v=sSF81yjVbJE
Apparently they are no longer pursuing stage 2 reuse on the Falcon 9. The next gen superheavy lift rocket, the BFR, is intended to be fully reusable though.
A reusable SSTO would be a very difficult project, given that noone's even built an expendable SSTO yet.
If you're going to build an expendable rocket designing it as a SSTO doesn't really make sense. With a single stage you can't shed the extra weight of the engines and rocket that got you out of the atmosphere and have to have engines that work both in atmosphere and in vacuum.
I agree. I'm just saying it's easier to make an expendable than a reusable one, because you don't have to allocate mass to return systems.
What I was trying to say is that there are other reasons to not build a single stage to orbit expendable rocket, mostly cost and payload capacity. I agree it'd be easier than a reusable version but if you're not returning the stage it makes way more sense to use the 2+ stage designs that are common today. Being able to shed the weight of the atmospheric stage and switch to a vacuum optimized engine is a big benefit.
Interesting that modern alt-space community often employs the concept "test a little, fly a little", and consider making reuseable systems easier.
I read somewhere, that the new first stage can do SSTO unloaded.
>It's also the first time SpaceX launches in fog
Musk said the "root cause may have been ice buildup due to condensation from heavy fog at liftoff."
Ice buildup on cryogenic components has been a problem with earlier private launch attempts from VAFB. See [1]for a frozen main LOX valve that didn't fully open due to ice frozen out of humid air.
3-meter waves?! For context, once those hit the surf zone they stand up a bit more. Here's what that looks like when it's breaking
http://www.surfline.com/forecasters/blog/12_foot1.gif
(source: http://www.surfline.com/surf-science/wave-heights---forecast...)
There's a pragmatic difference between recovering the booster over some period of time, vs literally parking the booster right where it took off & ready to re-launch within hours/minutes.
I can't see re-launching withing hours any time in the foreseeable future. Even once they're proven reusable each booster will need significant inspection and likely maintenance before being ready to re-launch.
> I can't see re-launching withing hours any time in the foreseeable future. Even once they're proven reusable each booster will need significant inspection and likely maintenance before being ready to re-launch.
Initially, yes of course. But if they manage to launch a stage 100 times and it always passes inspection and etc, etc etc it's not impossible that eventually you'll get to the point where you only inspect every 2 launches, every 3 launches, every 5 or 10 launches.
Once the ride to orbit costs: $100million/X + $Ymillion + $Zthousand
where X is the number of reuses
Y is the second stage cost
Z is the fuel, launch fees, refurb, etc
There's an experience curve (https://en.wikipedia.org/wiki/Experience_curve_effects) that shows you how much you'll save as you build more and more units and it's entirely possible that the (expendable) second stage could eventually get very cheap to the point where you don't want to spend $1 million (or whatever) going over the rocket for every launch.
If you're launching priceless (or very, very expensive) fancy space telescopes that cost tens of billions then the cost of a failed launch is very, very high. But if you're launching a bunch of food and you can lob another shot next week if it fails, and everything else is cheap enough, it might someday make sense.
Before you ask me if I'm crazy, please understand that airplanes do exactly this; you have to get your engines overhauled every few thousand hours and I'm sure there are inspections, but they don't tear the plane down and rebuild it after every flight. Once systems get reliable enough, that's a thing.
This is all correct, to expand a bit on it here's a spreadsheet someone posted in /r/spacex analyzing the cost benefits of reusability:
https://docs.google.com/spreadsheets/d/144Y_OVmFFYTh_zTiV-FH...
"Reusing the first stage three times halves the overall cost of launch. Reusing 9 times cuts the cost to 1/3. However, there is little benefit to first stage reuse beyond that… Reusing both stages just once halves the total cost of launch. In addition, reusing both stages four times reduces the cost to 1/4, and reusing eight times reduces to 1/8."
As you touched upon a lot of things in space are expensive because launch vehicles aren't reusable, once they are it makes sense to create cheaper and expandable payloads rather than multi-billion dollar payloads strapped to rockets that can't be allowed to fail.
The same stage probably won't be ready to relaunch but imagine an assembly line of reusable stages that land at the same facility where they take off and then head right into a service center. With enough stages in rotation you can have a near continuous stream of launches.
> Everything about the landing except the stuck leg seemed to be perfect.
And there's the issue: it only takes a tiny bit of imperfect to ruin a landing.
I do think that SpaceX is going to get to the point where they are recovering enough of their rockets to make it pay off. But there will probably always be a significant chance that some little thing will go wrong. Don't be fooled later by "we've landed 5 in a row" about that.
I guess it depends on what you mean by significant. It's true that, inherently, space flight is risky business.[0] This is new technology, so of course they are going to continue to uncover weaknesses even much further down the line once they start hitting a higher success rate.
But for the tiny bit of imperfect: the same could have been said for the space shuttle, and that had people in it. And its fragility was a fundamental to its design (it rode exposed on the fuel tank with its critically important heat-absorbing tiles). And the shuttle still had a decent success rate!
I would argue that these failures are less fundamental to the design of the rocket. And the difference is that if, in the future, you have that 1/100 failure on landing, it's only a loss from a cost perspective, not a human one.
This is very, very, early days. I'm sure you could have side the same about 'normal' flight, loads and loads of failures, then getting it to the '5 in the row', then a bunch of screwups.
Now jet flight across the oceans in often horrendous conditions is 99.999% safe (ish).
The number of things that could go wrong is limited. The will learn all of them.
The same happened with airplanes. Just something so simple as breaking sound barrier control inversion meant hundreds of pilots dying until someone figured it out..
Thanks to automation and telemetry, SpaceX is learning fast without killing anyone. In the past it was hard to analyze what went wrong when the pilot did not survive.
> explodes on landing
This is a pretty unfair characterization. It actually made the landing for most purposes, then a specific failure occurred - a leg failed to lock and it fell over. And yes, when a rocket falls over it will often explode.
As someone mentioned on Reddit
Succeeded to land. Failed to stand.Haha... Made me think the Olympics. What if they had a rocket landing event.
It landed, just didn't stick the landing :-)
"Explodes after landing" would be more accurate, I think.
and the "explosion" is borderline, it's very close to just "burns really fast", especially when you see what's left after the fire goes out: https://pbs.twimg.com/media/CY8-PdyU0AABqaa.jpg:large (there's quite a lot of rocket left)
That's a trick of perspective and scale, you are not seeing a rocket but one landing leg intact attached to the engine block. The tube exploded as you'd expect when it fell over and disintegrated.
Not really important though, they got the hard part right.
I'd work on engineering that, if possible. I mean if 10% of rockets fall over, but you could get them to not explode then you'd still be up.
I think people have a hard time grasping the scale of this stuff, and therefore the fragility involved.
Getting the rocket to survive falling over is extremely difficult. It can't even survive normal flight loads without the propellant tanks being pressurized, because it needs the extra rigidity to avoid collapse.
The margins involved are extremely slim. For a more familiar point of comparison, consider that a 747-400 (which is about as long as a Falcon 9 is tall, not that this means a whole lot) weighs about 180 tons empty, and can carry about 170 tons of fuel. The Falcon 9 first stage weighs around 25 tons empty, and carries about 400 tons of fuel and oxidizer. (Note that numbers are approximate, since official numbers are hard to come by.) That means that, sitting on the pad and ready to go, a Falcon 9 first stage is about 95% fuel, and 5% everything else. That 5% has to account not only for fuel tanks, but engines, hydraulics, support structure to hold up the ~100 ton second stage and payload, landing legs, and everything else that makes it a rocket and not just a pair of tanks.
Now you bring it back, let it fall over, and catch it in a way that doesn't break it. This is something about as tall as a decent-sized office building, with a roughly zero tolerance for sideways force of any kind. Imagine tipping over the Statue of Liberty and catching it without bending anything.
It's orders of magnitude easier to make sure the rocket doesn't fall over in the first place. You want to concentrate your efforts where they'll have the best return, and in this case there's no contest, it's not even close.
The video pretty clearly shows/sounds like an explosion. Not a huge one, but one none the less.
"Burns really fast" is literally the definition of a chemical explosion.
Suboptimal occurrence after a near-perfect landing forces SpaceX to reconsider strategies for next launch.
As a (student) pilot, I agree. You aren't landed until stationary and stable.
"Explodes after landing" would also make for a great ship name from Iain M. Banks' Culture series too, as Musk likes :)
> And yes, when a rocket falls over it will often explode.
Why? Why would a small hit make it explode, when the stress of going from orbit does not?
Because like all rockets it was designed to handle any expected aerodynamic loads with a certain margin with minimal mass.
Essentially the right parts just popped like a balloon. Falling on your side involves much different loads than being propelled into orbit. There's little value to designing a rocket to withstand such a fall.
I assume it's due to the liquid oxygen remaining in the booster; essentially its a towering pressurised container falling on its side causing a breach.
Different stresses.
To elaborate, the rocket can take only about 1 atmosphere of pressure in the radial direction, but much more force in the longitudinal direction. It's designed to withstand the stresses of going in a straight line, but as soon as it bends it'll crumple, like a toilet paper cardboard tube.
So when the thing topples over, it bends. And when it bends, it ruptures because it's far in excess of the loads under standard conditions.
It's not an unfair headline. It did explode when it landed. This is not good, no way how you twist it.
It's actually quite good. It's not as good as if the rocket was recovered intact, certainly, but for the fourth landing attempt ever of a highly experimental test program, this is a very good result.
It did not explode when it landed. It exploded after it landed. This is an important distinction, because the latter is a thousand times harder to accomplish.
Let's say they permanently remove one leg and it now always tips over on landing and has no stable landing configuration. Could they bill that as a self-landing rocket?
The point is that the ability to land is much harder to develop than the ability to stand up after landing. Improving the leg locking mechanisms is relatively trivial compared to developing the ability to turn a booster around in space, fly it back to earth and land on a floating platform.
If I was involved in SpaceX then I would be proud to have helped solve such a tricky problem, and optimistic about fixing the far less difficult leg locking problem
I agree it is a big achievement. I just wouldn't call it a successful landing. If the moon landing had involved immediate tipover and explosion with a leg that didn't deploy, I think a subsequent landing would have been considered the real first successful landing.
Eh probably. What a strange question.
Speaks volumes for Mr. Musk's character that they're being completely open and honest about this problem. Turns the conversation from "What happened? What are they hiding?" to "Interesting Engineering problem. How can it be addressed?"
They don't have much in the way of competition to keep 'trade secrets' from
They have lots of trade secrets. They famously don't file patents, because their primary competitors are overseas and won't respect them anyway. Musk discusses it a bit in this interview:
http://www.wired.com/2012/10/ff-elon-musk-qa/all/
The reason they're cavalier about landing videos is that there's not much you can really take from them that would be useful to building your own version of this system. It sounds like much of their "secret sauce" is in manufacturing techniques, materials, and internal design.
If that isn't tongue in cheek, you're insane. There's a laundry list of companies that are competition to them, including two of the largest defense contractors in the world.
https://en.wikipedia.org/wiki/List_of_private_spaceflight_co...
Not sure it was meant literally. I took it as more of a jibe at the quality of existing space companies (and Blue Origin).
That's because Musk created a company without peer.
This is progress. They got a good landing, then the landing gear collapsed, and not because of a hard landing. Next time they'll have a design that forces the landing gear down and locked, ice or no ice. Somewhere down in Hawthorne, someone is probably freezing one of those mechanisms in a cold chamber right now.
This is way better than back in July, when the booster blew up because of a strut failure. That was a major quality control failure.
This just in: Elon Musk has reportedly terminated all employees who uttered the phrase "Break a leg!" before launch.
In all seriousness though, this was by and large a successful landing, not to mention that they successfully put their payload into orbit without a hitch. The number of things that have to go right to even get that rocket to touch down on the barge is mind boggling. Truly impressive, and bodes well for the future of SpaceX.
I like to think that with these videos SpaceX is also making a very worthy contribution to more realistic movie special effects.
Not enough lens-flare.
Easy enough to add in post.
That was pretty much exactly what I expected to see from the video given the description of a broken landing leg yesterday.
Elon's twitter comment about the ice is interesting because it adds some interesting twists. If the stage is icing up as it descends it would change the mass calculation, however it does not seem to shed ice when it lands in the video. He suggested that ice at launch may have interfered with leg locking, which would mean that ice survived travelling supersonically through the atmosphere. But hard to figure how that could be.
In an earlier re-entry video, the camera lens ices up during the re-entry burn, presumably due to water from the engine exhaust. So I don't think that re-entry is necessarily enough to heat up the stage enough to melt all the ice on it.
In this case the ice would have been protected by being enclosed or mostly enclosed by the leg mechanisms.
The rocket exploded because it fell over, not the other way around. Had one of the landing gears not malfunctioned, it would have been fine.
yeah, it feels the title this time should be rocket explodes AFTER landing, to give a better feeling of how close this was
especially since it seems to have hit the bullseye on the center of the barge (maybe missed dead center by a few inches).
You can tell it missed by a few inches from the video?
4 feet
It's not really a landing if the whole thing collapses and explodes right after touching the platform.
If a pilot successfully takes an airplane out of the air and onto the ground such that all the weight of the airplane is on the wheels, and that weight transfer causes one of the tires to pop, and that causes the plane to skid, and then roll over, and then blow up, what kind of failure was that?
Was it the pilot failing to land the airplane properly?
Or was is the airplane failing to behave as expected after landing?
How exactly do you define the act of landing? Do you have to come to a full and complete stop? If that's true then few airplanes have ever "landed" until they've pulled up to the gate to disgorge their passengers.
Reminds me of an old saying in aviation: "A good landing is one you can walk away from. A great landing is one where you can use the plane again."
I think it depends on whose perspective you are looking from.
If I assume I am SpaceX, I think I assume that my goal is to land my rockets such that they do not explode, so that I may reuse them. In this sense, I think I can say that the landing failed.
This is the second time something like this happened. Why not put 4 tall posts up - equidistant from each other - a square.
Then a wire net between the posts.
When it tips over, it can just fall into the wire net.... they could even have motors to unwind a little while it leans over on them to allow "soft catching" the rocket. Foam over the wires would help here.
Actually... why not skip the barge & the dramatic landing and just catch it with a big underwater net? I suppose getting the rocket wet with salt water is not good? (the inside is covered with liquid spill indicators which void the warranty?)
2 reasons:
1) As you say, salt water is bad. Do never go in salt water if you want metallic, electronic things to keep working.
2) The rocket can't withstand much, if any, load in longitudinal bending mode. It'll buckle like a toilet paper cardboard tube. This almost certainly includes under its own weight, if you were to 'catch' it at the top of the rocket and hold it on an angle. To design against that, you'd be adding way too much weight to the structure to make it worthwhile.
Rockets are more fragile than one might think, but even assuming that would work, it's significantly more useful to be able to land just about anywhere that's flat.
Also, we don't have giant posts and nets waiting for us on Mars.
I guess if you optimised for a net 'landing' you'd also be losing the ability to realistically land anywhere you want, since you'd have to have a net there. learning this way would potentially open up any flat surface
My initially reaction were similar ideas, but thinking about it some more i am not sure if the empty tank could tolerate the stresses from getting caught in a net. And with a landing strut failure like today, you would probably lose the engines even with the tank not completely tipping over.
But SpaceX seem to be exceptionally good at control systems, fast and precise automated planning. Maybe they will just skip the level of passive rocket catcher structures and intend to move directly to a three-axis actuated landing table? A system like that that could take responsibility for a tiny little amount of deceleration (think extra suspension) and a fair bit of balancing completely outside of the mass budget of the rocket.
3 axis table? Do you mean that the platform would be able to shift either way to keep it from wobbling over? That seems hard given that a rocket is tall & skinny.
How about a massive electromagnet underneath?
Tall and skinny is exactly what you would want for dynamic balancing. Unfortunately, an empty booster would have a very low center of gravity compared to the external shape.
Anything other than a perfect vertical landing is likely to result in damage to the structure and components. Thus negating most of the value in landing the 1st stage.
Sea water is also highly corrosive to many materials.
Perhaps landing into a tank of non-corrosive liquid would prevent such collapses? Or on some kind of "glue"/alloy that quickly freezes.
You can also have spearguns firing cords from the top of the rocket to the ground after landing, to hold it.
One of the main stated goals of vertical landings is so they can do it on other planets/bodies. There are other proven methods of reuse when you have a benefit of an atmosphere and/or infrastructure.
A working vertical landing mode that can also be used on Mars, Moon and other objects in the solar system is one of the major mission at SpaceX. Shipping a giant vat of non-corrosive/conductive liquid to another planet does not appear viable.
I was thinking that same thing. Maybe not water but some kind of non-conductive gel?
I want to know what exploded - I wouldn't have expected it to have very much leftover fuel at that point...
(From http://spaceflight101.com/spacerockets/falcon-9-v1-1-f9r/ )... the first stage of Falcon 9 v1.1 is capable of holding 119,100 Kilograms of Rocket Propellant 1 and 276,600 kg of Liquid Oxygen.So even if it's 99.9% empty, it still can have 120 kgs of rocket fuel. That'll go with a bang.
And it's unlikely to land with only 0.1% of its fuel left - that margin is too small to be attempting a soft landing, so I'd expect it to be a lot more. Then compare with just 5 gallons (probably US gallons, about 19 liters, close to 17 or 19 kgs) of ordinary gasoline:
Here's a couple of examples of what it looks like when a rocket explodes when it's still full of fuel:
https://youtu.be/NCWunnJXdm0?t=180
https://youtu.be/Zl12dXYcUTo?t=32
Then compare to this dinky little explosion.
This is the an explosion of 5 gallons of petrol: https://www.youtube.com/watch?v=C72bv2YhZ6A
Doesn't take that much to make an impressive bang.
The rocket runs out of usable fuel, but that doesn't mean that it is empty. If for no other reason the turbo pumps would probably get damaged beyond repair if you run the tank bone dry. Also it's not just fuel, but oxygen too in the right ratio.
If you put a spark inside a full gas/petrol can, not much happens. Not enough oxygen. Half full? Still not such a big deal.
But empty the can, leaving behind just the fumes and the oxygen, and you have yourself a bomb.
My understanding is that the rocket here is a similar problem. It's a giant tube of explosive material. I wouldn't want to tap it with a hammer. And they've got it falling to earth at supersonic speeds, then calmly setting itself down on a barge at sea in 3m waves.
It fills with helium as it empties out the fuel.
In that case, I have no idea why it exploded. :)
Rocket fuel/oxidiser together are pretty explosive (by their very nature) - even if it was just leftover vapour in an otherwise empty tank.
Is there a reason not to design the rocket with more legs, say 6 legs instead of 4?
Weight. Every pound you use up on things like legs is a whole bunch of pounds you can't take to orbit.
Weight...
An exact bulls-eye, absolutely amazing.
Congrats to the guys at Space-X! Love to see me some hardware blowing up.
Seriously, I'm not being facetious. We make aeronautical hardware safe by flying the crap out of it. That means lots of flights. Lots of accidents. The more you fly it, the more problems you have, the safer it is.
Congrats guys. Every time gets closer and closer. A few more and you'll have this thing nailed. That's good for all of us.
They are getting really close to sticking a landing on a barge. I would be surprised if we don't see a successful barge landing this year.
Am I the only one who was surprised by how violently the rocket exploded when it fell to its side?
Put yourself in the liquid oxygen's shoes.
One second, you're chilling out at -207 C with your bros and some kerosenes, maybe even stopping off in near space--then, out of nowhere your containment vessel is compromised and you're evicted.. expected to just phase change and mix with all those common atmospherics.
I think I'd react the same way.
Thin metal tube containing gaseous oxygen and kerosene, pressurised to 50psi.
I suspect there is also a termination system that deliberately detonates so as to control the mode of failure (i.e.: combust the dangerous stuff before it has an opportunity to mix with the other stuff and make things worse)
They keep getting better so quickly! I'm in no way qualified to say this but I would have to guess the tip over after landing is a very trivial problem to overcome compared to atmospheric entry with 180 degree flip and burn to slow for landing. Go SpaceX!
I wonder if they've considered side curtain airbags to catch the rocket once it's really close like that, sort of like Amazon traps your item in 3 or 4 of those big bags, instead of lots of bubblewrap.
Could someone explain to me why they attempt this? Wouldn't inflating a set of floating devices when it goes down the ocean an easier way of retrieving it? Or something other than this REALLY HARD TO PULL OFF maneuver? Genuinely interested.
The key thing to remember about rockets is that they are incredibly fragile. The rocket is about 15 stories tall and is designed for force to only be applied at the end either via the rocket engines or the landing gear.
Any type of lateral forces will irreversibly damage the rocket. As an illustration, extreme care is taken when the rocket needs to be transported on its side. Some rockets, not the Falcon 9, can't even be transported on their side without being pressurized.
So pretty much anything other than a perfect soft touch landing would leave the rocket unable to fly again. Anything touching the 3/16" thick skin of the Falcon 9, would cause the very least extensive refurbishment at the least, but more likely irreversibly damage the frame of the 15 stories tall 1st stage. So this rules out every alternative that has been suggested in this thread.
While that's true, the metal tube is not the part that's expensive to build.
You'd be surprised: https://en.wikipedia.org/wiki/Isogrid
SpaceX mostly uses friction stir welding to avoid the costs of isogrid
Two main reasons I can think of: 1) Sea water is extremely corrosive. If your booster takes a dunk in the drink, it's going to be very hard to refurbish for another launch. Lots of components (electronics, valves, etc) would need to be replaced and the structural integrity of the tanks themselves may be compromised by rust.
2) Flotation devices attached to the booster = extra payload. It would be the canvas/dinghys AND compressed gas canisters for inflating them. This is arguably (a lot?) more weight than just landing struts + fins. Any extra payload on a rocket represents a massive cost and means less stuff you can haul for paying customers.
In addition to that the vehicle is extremely weak when lying on its side. I should think there's a good chance the tanks could be damaged by waves bending the vehicle.
Correct. Also the terminal velocity even with a parachute can be high, and if you hit a rising wave, even more.
Actually parachuting and fishing the stage from the sea was their first idea, but they never recovered a single stage that way, and moved to active controlled recovery, which is much much much better in my opinion.
Flotation devices attached to the booster = extra payload
Yes, but how much extra fuel does the rocket have to carry to land? That's a ton of extra payload as well.
Estimates I've heard say 15% loss of payload mass for a barge landing, 30% for land.
What do you mean by "loss of payload mass"? If the rocket lands on a barge it has to reduce it's payload by 15%?
Any ideas why it's higher on land? Seems like it wouldn't differ that much.
Ascent trajectory is much different. Orbit is mostly about horizontal velocity, the altitude is just to get above the atmosphere and is the easy part. For the first stage to return to its launch site for landing, it has to cancel out all of the horizontal velocity it builds up while lifting the second stage and payload, then turn around and come back. A barge landing can use a more optimal ascent trajectory and have the first stage land several hundred kilometers away from the launch site.
You have to accelerate the rocket back to the launchpad if you want to land on solid ground -- there's no convenient landmasses at the right distance. That takes fuel.
I assume the rocket is in geosynchronous orbit? Otherwise it would just be a timing issue (i.e. fire the rockets when you're over land).
The booster never reaches orbit as it is on a ballistic trajectory
They want to use this tech to eventually land rockets on other planets so the rocket needs to be able to land upright. Short term it might be easier to land on inflatables but they're looking at the bigger picture.
The utility here is not really landing on other planets, but instead the order of magnitude decrease in launch costs if they don't have to build a new first stage for every launch.
This could theoretically be achieved by either means. The question was specifically why a vertical landing is favoured over a cushioned inflatable landing.
Musk has stated in the past that they're looking to eventually use this tech to create rockets which can be used on Mars, hence why parachutes and inflatables are out of the question.
Parachutes also have the problem that you can't as easily control the landing point.
No, its just not possible to maintain the integrity of the rocket if you're going to somehow lay it down on an inflatable. How could an inflatable withstand the temperature of the firing engines?
For weight, the sides of a rocket are very thin. Think tin can. Vertical is OK but horizontal can't work.
Which makes sense. It's designed specifically to withstand a huge amount of vertical stress.
They want to be able to relatively quickly send it back into space. If they have to pull it out of the ocean and dry it out/fix it, I assume this makes their turnaround time less than ideal. Think what you do with a 747, it lands, a technician checks it out, it gets refueled, it takes off again. We'd be able to build things in space so much faster with that sort of round-trip lifting capability. I assume there are also implications for exploring other planets. This is my guess as someone who has not studied the issue closely.
You don't want to carry heavy landing-maneuver gear to space and back. Thus the skeletal landing struts that were not-quite-strong-enough for rough seas.
Further, the ocean platform it was landing on was built to sustain heavy seas and stay relatively flat. Recovering a rocket bobbing in the waves could be much harder than this. Also a challenge: quenching a very hot engine in cold ocean water.
No, this platform-landing is probably one of the simplest, safest ways to recover/reuse a stage.
Rockets have always been able to land in the ocean more or less intact (i.e. without disintegrating). However, if the rocket is dipped in salt water, the restoration would be enormously expensive, so it needs to stay dry to be re-used.
Of course, you could just try to land it vertically on the water on some cushion and have more cushions deploy to make it tip over horizontally and float (all the time staying above the surface of the ocean). Such a solution isn't as compatible with recovery on dry land. If you want to do e.g. space tourism missions and land on dry land, the vertical landing seems better.
Rockets have always been able to land in the ocean more or less intact (i.e. without disintegrating).
No they haven't. SpaceX started doing that in 2013 before the barge landings. I don't think anyone had ever even tried to land(sea?) a liquid fuel booster before that.
You may be thinking of the STS solid boosters, but solid boosters are really a different game. They can be built sturdy enough to hit the ocean at 60mph, but they couldn't possibly be simply refueled and reflown.
How do you expect it to be able to land on an inflatable raft? The point of landing the rocket is to reuse it, which is not possible if it falls over or gets wet.
Landing in the ocean is only done for certain types of missions, where its not possible to carry enough fuel to turn the first stand around a fly it all the way back to the launch site. Instead, they can carry just enough fuel to land wherever they are finished boosting the 2nd stage, to put it simply.
Keeping it out of the sea water is a key part of reusability.
Or even a different kind of barge. A floating 'jar' rather than a flat surface, the thing could tip and not fall all the way.
Salt water isn't good for rockets. Once you solve this really hard problem of landing a rocket on a barge on a dynamic ocean you have a real competitive advantage.
Is that the reason they've been using the barges for landing? I'd always assumed they were just being extra cautious since it could endanger civilians or crew if the reusable stage was supposed to land on solid earth.
I'd imagine that the barge landings introduce a lot of uncertainty and complicating factors that are impossible to completely nullify. High waves and (comparatively) strong open-ocean winds seem (to me at least) to make consistently successful lands much harder.
There was definitely a safety issue that lead to earlier landings taking place on a barge, but it also requires a lot less fuel to land somewhere downrange (which is always over the ocean) rather than boost all the way back to the launch site.
Some flights wouldn't have enough fuel to make it back to the launch site. That's the reason I've seen. There is also a large amount of water, so that increases the places you can land.
The corrosion from the salt water would completely ruin the engines, obviating any benefits from returning the first stage.
Yeah, I don't understand why they won't keep landing them on the ground like everyone else does. It's not like there's not enough space on Earth.
Depending on the mission it may not be possible to get back to the landing spot and sometimes the most efficient place to land is in the middle of the ocean. Musk answers that question here[1] in a tweet regarding the launch. You would have to have launch sites all around the earth and get approval to land or carry a lot of extra fuel to get back to where you started from which would be prohibitively expensive and heavy.
> like everyone else does
Nobody else does this. I have absolutely no idea what you could possibly be referring to. SpaceX lands on land preferably when it is an option.
> I don't understand why they won't keep landing them on the ground ... It's not like there's not enough space on Earth
As a general rule, you not understanding the reason for something does not mean there is not a good reason. For reference, see the Dunning-Kruger effect. Furthermore, I honestly do not understand how you could even contemplate "SpaceX does not think there is enough space on land" as a serious argument and treat its dismissal as legitimate support for your beliefs. This is some of the most egregiously lazy reasoning I have ever seen on the internet.
SpaceX launches rockets in the direction of water so that an accident won't threaten property or people on land. To return to land after staging the first stage of the Falcon 9 must perform a burn—the "boost back"—to point its lateral velocity back to land; this is the first of three burns required for landing and the most expensive in fuel by a considerable margin. If the first stage is travelling too quickly (greater than approximately 1.6 km/s lateral velocity) it does not physically have enough fuel to return to the launch site and perform the landing. In this case, a far more mild burn can put the booster on a re-entry trajectory and it can land on an autonomous barge in the ocean. As the rocket trajectory is chosen to put the ground path well away from land, the choice is between either returning to the launch site or landing in the ocean. If a return to the launch site is prohibited by the rocket's capabilites and physics then an ocean landing is the only option.
In the case of Jason-3 a barge landing was the only option as SpaceX does not yet have permission to use their landing facility at Vandenberg Air Force Base. In the future, the central core of the Falcon Heavy will almost certainly have to land in the ocean due to its velocity at separation.
>Nobody else does this. I have absolutely no idea what you could possibly be referring to.
Believe it or not, we've been landing spacecraft for decades. Does "space shuttle" ring a bell?
The Space Shuttle was a space craft, not a rocket. The SpaceX equivalent to the Space Shuttle is the Dragon spacecraft. Dragon V2 does land exclusively on the ground.
In addition to all that (spacecraft, srbrs, atmosphere), a space shuttle launch literally cost more than a billion.
The shuttle throws its lower stages into the ocean.
Which were recovered and refurbished to keep cost down.
OK, that's one orbital rocket that's recovered on land. You said "everybody else" which implies at least several, so what other examples are there? (Hint: none.)
Buran. It only flew once, but it did work!
Apollo Lunar Module, if Moon counts.
Buran, fair.
Lunar module doesn't count, the reduced gravity makes everything a hundred times simpler.
The space shuttle couldn't land and take off on a planet whose atmosphere doesn't support it, hence why SpaceX is trying to do the same via rocket propulsion.
> Yeah, I don't understand why they won't keep landing them on the ground like everyone else does.
No one else lands first stages. SpaceX is the first to do it.
It has to do with the payload mass. If it's too massive, it won't have enough fuel to return to the launch site, so they do a landing at sea.
So if you launch out of Cali going west and separate stage 2 300 miles out.... What is under you to land on?
Not to change your overall point, but you almost never launch west. When possible, you want to launch east, to gain the benefit of the Earth's rotational speed. Sometimes you launch north or south so you can go into a polar orbit which allows viewing more of the Earth. But there's pretty much no reason to launch west. One exception to this is if your launch site is located in a place where that's the only option, which is why Israel does it like this.
For American launch sites, you have KSC for launching east, and Vandenberg for launching south. (North and south are equivalent in terms of which orbits they can reach, so you don't need both.) Vandenberg can be used for launching west, but pretty much never is, unless you count ICBM tests and the like.
Well the launch Space-X launch was South-West, clearly not over any land.
Southeast, not southwest. But yes, as I said in the original comment, it doesn't change your overall point.
I assume the parent poster meant that the launch should take place from somewhere on earth where there is earth 2300 miles out. It's likely not convenient to do so, at least not for all launch directions.
It would be convenient enough but the FAA isn't too happy with the idea of a 12-story missile full of explosive fuel and oxidiser flying over populated areas.
Yes, part of the inconvenience of course is that it's unlikely to be anywhere near the continental US.
If you just needed to find two bits of ground with room for rocket pads and one 2300 miles east of the other it really wouldn't be that hard to have both in the continental US. It's the fact that the whole flight path has to be safe that makes it virtually impossible.
The entire world = California.
Hacker News has officially become a parody of itself.
I don't even live in Cali.
But some rocket launches come form the west coast, not all are Florida.
The landing could be made safer by something like cushioned walls that deploy towards the rocket after touchdown, to avoid such explosions. Think of a giant Christmas Tree stand like this: http://www.christmastreeland.co.uk/product_images/v/428/761_.... but with cushioned hooks on the barge. You can't always hope for all 4 legs to be in perfect condition, or that there aren't high waves in the ocean. That rocket is huge and seems to fall too easily, while a stand with hooks can't be too expensive, unlike a complete new rocket...
Here's a side-by-side comparison of their three barge landing attempts: https://www.youtube.com/watch?v=IA7RzJckvQ4
I don't think big, over-engineered solutions really look necessary with the amount of progress they're making. Plus, there aren't any cushioned walls on Mars, which is SpaceX's eventual goal - use this sort of tech to touch down there.
Also, if you deployed mitigation methods prematurely, then it stops the drive for improvement and tuning of the core landing functionality.
Quick deploy cushions or other "Oops" enhancements might feature into the final version of the barge, but for now I think they're still trying to maximize the landing success rate. Better not to split engineering resources when the most important problem can still benefit from optimization.
They are landing on Mars. That's the ultimate point. Mars does not have airbags.
I get the Mars part but they could have the walls to be fail safe at least on Earth. It's not like they will improve the design only if the rocket falls over and explodes. They would still have to land it up straight, while having some sort of "no wall touched" target (or award). Not to mention the money they save if not every fail is also a complete loss of the rocket. p.s. Money left is also good for future Mars missions.
SpaceX eventually wants to land vehicles on Mars, where such landing infrastructure won't exist (at first).
(The Dragon cargo capsule has windows, despite cargo not needing to be able to look outside into space -- the windows are there because the capsule is designed to eventually carry humans some day.)
Seems like it would save money in the interim though, and they'd still have the data of whether it fell or not.
Bear in mind how large the rocket is, and that anything you put on the barge has to withstand being scorched by rocket exhaust.
Why is the barge landing part so important to them? Seems unnecessarily difficult.
Big world out there...surely some suitable location can be found that is less wobbly for a start.
They have a limited number of launch sites available to them, and the landing site is based on trajectory and fuel. Depending on the mass being launched, there will often not be enough fuel to turn around, and if you keep going, there's not much but ocean for a long way. Also, not any land will do. You need a pretty big, purpose-built space to land a rocket. With a barge, they can put that space where they need it.
Launches which send the payload beyond low earth orbit require too much velocity for the first stage to then turn around and make it all the way back to the launch site.
They put the barge downrange so less fuel will be needed to turn around and land, enabling first stage landings on beyond-low-earth-orbit launches.
This has got to be a large part of why they were looking to launch from south Texas. that gives them a few hundred miles of gulf, and then they can land in FL.
At least the barge looks like it should be reusable.
Didn't it land, then fall over and explode?
Also, didn't this portion of the rocket land before the satellite was deployed?
Amazing! If they want to use this tech for landing people on Mars (or anywhere) they still have some way to go though!
Can't wait to fiddle with the landing source code after they release it in 10 to 20 years time :D
Would it be possible to have locking mechanisms directly in the dock itself?
ie. maybe the rocket descends several feet INTO the dock into a hole which then locks around the body of the rocket?
||
||
==||== dock (which opens wide for decent and then closes)
||
^^To be clear it's a barge, not a dock.
It might be possible, but we're talking about a rocket descending from hypersonic spaceflight; the accuracy is always going to be +/- a few metres. And the rocket would still have to have some kind of "hardpoints" that were strong enough to absorb the landing impact (you don't want to land smack on the delicate engine nozzles). A (relatively) big flat landing field and legs on the rocket itself seem like the smart approach (and Musk wants whatever technology they use to be usable for landing on Mars too).
Yeah but if a rocket can so easily explode just by falling over, I'm not sure there are any legs I trust it to land on.
I mean what if the legs were damaged during launch somehow, how exactly would it get back down safely other than just dropping it in the ocean completely?
>I mean what if the legs were damaged during launch somehow, how exactly would it get back down safely other than just dropping it in the ocean completely?
Then it blows up and you fix the extremely serious problem that threatened the primary mission by damaging the rocket during launch.
It's much better to focus on having the legs work than to come up with wacky workarounds. The legs are proven, don't forget. They need debugging, but they work.
Also remember that recovery is not a requirement. This rocket started out as a pure expendable launcher. It's profitable right now even throwing everything away. If you lose half the first stages while landing, you're still way ahead. And there's no reason to think the success rate will be nearly that low once they get some more experience with it.
> I mean what if the legs were damaged during launch somehow, how exactly would it get back down safely other than just dropping it in the ocean completely?
That's exactly the plan. The first stage will never carry humans, so in the event of a major technical fault it'd just drop into the sea.
> Yeah but if a rocket can so easily explode just by falling over, I'm not sure there are any legs I trust it to land on.
Your proposal is a giant landing pad that snaps shut to hold the stage in place. I'd trust a leg over that...
There are any number of critical systems on a rocket - what if the fuel tanks were damaged during launch somehow? Or the grid fins? Or the hydraulic tanks? Or the engines?
That's asking for landing precision on the order of centimeters. While this landing was a bullseye (it's completely inside the inner yellow circle! wow!), they're probably not ready for that precision just yet.
You also need to land completely vertically, and it looks like the stage comes in at an angle on its suicide burn.
Part of the problem is that the rocket walls are very thin and only suitable for vertical loads. You'd practically have to surround it with giant airbags to make that work.
They'll fix the landing leg problem somehow.
I'd imagine that'd be even more complex and prone to failure.
is there a reason they can't like come to a stop over the water and then land in it and just expand some floats?
1. Salt water is very corrosive, and would require extensive rebuild of the engines. 2. They want the tech to land on Mars before too long.
I figured salt would be the reason. Also the thermal stress of quenching it.
Forgot about the mars aspect.
they just need airbags installed on the barge so the moment rocket lands the airbags inflate and hug the rocket.
a) isn't this from last year? IIRC they had two failed barge landings. This looks like the first one.
b) The headline makes this sound like a miserable failure - still beats "fell into the ocean never to be found again", as all other current first stages do.
new launch. they need the barge for heavier payloads, because it costs much more fuel to go all the way back, so they'll keep testing.
Musk posted an early statement blaming icing due to bad weather conditions. https://www.instagram.com/p/BAqirNbwEc0/
...and of course press is overly sensationalistic. nothing new there to report.
In this case, they had enough fuel to return to the launch site but they used the barge because they couldn't get permission to return to Vandenburg. http://observer.com/2016/01/breaking-spacex-fails-a-third-ti...
a) No this has just happened yesterday. tweet confirming: https://twitter.com/elonmusk/status/688837706005131264
b) true :)
Its a failure because it didn't do what it is supposed to do.
Current first stages do exactly what they are supposed to do extremely well.
It did exactly what it was supposed to do: deliver the second stage to the right place and velocity, and attempt a landing.
The landing failed, but it's part of a test program, failures are supposed to happen.
They got paid ~$90 million for this flight, and the customer is happy because they got exactly what they paid for.
Technically, it exploded well before it delivered the satellite.
edit to add some facts since this seems to be getting downvoted pretty quickly: Stage 1 landed and exploded at around T+10min, the satellite was deployed at T+56min. This was just two minutes after it was delivered on its final orbit. Both of those could be considered "delivered to space", neither of which happened before the failed landing.
You're being downvoted because it's a stupid assertion and it's "technically" not even the same craft at that point.
The title presented it as if it were a single craft at all times. Of course "delivering 2nd stage to space" would sound silly, but I'm sure the title could be worded factually correct and still be simple and informative (as titles should be).
"SpaceX booster explodes during recovery, payload delivery unhindered"
I think this is an interesting point. While I don't think we ought to rush out and change our terminology, I had not heard this anywhere else.
The satellite was comfortably above the Kármán line by the time of the failed landing.
Comfortably for ~2 hours before it would fall back to Earth. I think that "delivered" implies that something is done, in this case a final position for the satellite.