I meant instead of doing their normal reverse landings, but someone else answered, apparently its better for the engines, and a lighter payload overall.
Landing legs are heavy and any mass you lift up lowers payload. You also prevent damage from the engines (which are much more powerful than the Falcon 9 Merlin engine) blasting the surface and reflecting heat/shockwaves back to the ship.
He [Elon Musk] was not enamored with the landing legs being planned for Starship’s booster. They added weight, thus cutting the size of the payloads the booster could lift.
“Why don’t we try to use the tower to catch it?” he asked. He was referring to the tower that holds the rocket on the launchpad. Musk had already come up with the idea of using that tower to stack the rocket; it had a set of arms that could pick up the first-stage booster, place it on the launch mount, then pick up the second-stage spacecraft, and place it atop the booster. Now he was suggesting that these arms could also be used to catch the booster when it returned to Earth. It was a wild idea, and there was a lot of consternation in the room. “If the booster comes back down to the tower and crashes into it, you can’t launch the next rocket for a long time,” Bill Riley says. “But we agreed to study different ways to do it.”
A few weeks later, just after Christmas 2020, the team gathered to brainstorm. Most engineers argued against trying to use the tower to catch the booster. The stacking arms were already dangerously complex. After more than an hour of argument, a consensus was forming to stick with the old idea of putting landing legs on the booster. But Stephen Harlow, the vehicle engineering director, kept arguing for the more audacious approach. “We have this tower, so why not try to use it?” After another hour of debate, Musk stepped in. “Harlow, you’re on board with this plan,” he said. “So why don’t you be in charge of it?”
Landing legs are heavy and any mass you lift up lowers payload
Notably, the relationship is exponential, so lowers it more than you would expect.
The laziest possible search gives me 550,000kg for the rocket, 8,000 kg for payload, and 2,000kg for the landing legs, so 0.33% of total but an astonishing 25% of payload. Given the exponential relationship, even the 0.33% could have real impact, so 25% is somewhere between "holy shit" and "did lagrangian mess up the math and/or use poor data"?
Hard to find good data while they're still revising and testing. 550mT is probably high since a previous version was under 400mT for both stages put together, but they've beefed up both heat shield and booster a bit since and I dunno how much. Payload is probably around 40mT reusable right now but no telling for sure until they start doing real orbits. Landing legs on both stages would probably be 8% or so of dry mass, 32mT, but only mass on the upper stage trades off 1:1 with payload, so I'd guess they'd lose 40% of payload with v1 Starship, and maybe bring that down to 10 or 15% by v3.
Huh. That's actually not as bad as I'd have guessed. Either they're so good at guidance now that they consider the catch to be "easy", or they were afraid of losing even more mass budget during development (that 40mT is down from a 100mT goal), or they're really not kidding about their real goal for the catches being cadence.
Musk claims he wants to just set a booster back on the launch mount after a catch (as they just practiced late yesterday) and stack the next ship on to launch again an hour later (as they probably won't practice for years). Sounds crazy to me, but I though catching the giant rocket in more-giant robot arms was crazier, so what the hell do I know?
Musk claims he wants to just set a booster back on the launch mount after a catch (as they just practiced late yesterday) and stack the next ship on to launch again an hour later (as they probably won't practice for years). Sounds crazy to me, but I though catching the giant rocket in more-giant robot arms was crazier, so what the hell do I know?
I suspect that's one fight he'll lose on regulatory grounds. Space travel isn't quite regulated like the FAA, but aircraft maintenance requirements are no joke and no small part of why airline scandals become such a big thing, even as those same maintenance standards are why airline safety is so exception. The federal government is willing to accept some form of risk by SpaceX in the name of R&D, but if/when flights fail because of the complications of one flight compromise the next, maintenance delays can be enforced.
This is especially true if the inevitable accidents knock out a tower. One of the logistical issues of the catch-strategy is that it makes the towers a far more 'brittle' chokepoint. Previously, towers needed to just be able to set up the rocket in the first place, but the rocket could land more or less wherever that was a suitable pad. Now the rockets can only land in one place, and if a tower is damaged then no flights what-so-ever can land or launch from there until it is re-established. Which is to say, a single landing accident could take out a launch site for days / weeks / even months.
What that means for Musk is that the boosters will likely need to be re-inspected / re-certified. That would likely entail lowering them to the ground, driving them over to a maintenance facility, and otherwise doing more than an hour of work. The exception would be if a government was willing to provide a waiver for this requirement, say in time of conflict... but in such a conflict, an adversary who could justify a need to launch more payloads into orbit would also have the capacity to target the towers by various means, meaning, again, safety and reliability issues. And this, in turn, would bring the comparison of how governments regulate military aviation, which in some respects is more intense than civil regulations (because the government actually owns the expensive thing).
Now, don't get me wrong- it's all still very impressive- but this is one of those areas where the salesmanship and technical capacity starts to run against other actor interests.
A typical (so typical they did another two this morning and nobody paid attention) Starlink launch has the booster fire its engines, then shut them down, then fire them again for a reentry burn, then shut them down, then fire them again for the landing burn. For a return-to-launch-site mission like their two last month there's also a fourth startup and shutdown for the boostback burn.
There may be someone at the FAA who thinks four ignitions in a row (where the second ignition aims the rocket back at the coast of Florida!) without inspection is fine, but six ignitions in a row with only a brief inspection after the third is crazy, but I doubt it. The feds are pretty good about making distinctions between airline safety (where we're down to something like 1 fatal incident per million commercial flights and rightly proud of it) or astronaut safety (where NASA wants 1-in-250 or better) vs unmanned flight safety. In the most extremely opposite case, unmanned test flight safety, FAA rules have been as lenient as "yup, both halves of that Starship sure screwed up and exploded right where you warned us they might screw up and explode; carry on" after the 3rd test.
The FAA has rightfully cracked down on a bunch of Falcon 9 issues recently, and Starship shouldn't be any better, but it shouldn't be any worse. Not doing a return-to-landing-site or return-to-tower didn't save SpaceX from those crackdowns. Booster fails its 24th landing, on an unmanned ship, in the middle of nowhere, in a NOTMAR zone behind a "Beware of the Leopard" sign? Falcon 9 grounded for days. Second stage deorbit burn is 0.5 seconds too long and it burns up slightly short of where it was expected to burn up? Falcon 9 grounded for weeks. It doesn't matter whether there's a ship or a tower that might get damaged on a failed landing; they'd get grounded for an investigation of what led to any landing they didn't expect to fail, to find any root cause that might affect other phases of flight too.
The FAA hasn't been obviously right about how they license SpaceX flight plan changes lately (though it was nice that they finished the IFT-5 license as quickly as they did in the end), but that's a separate issue from incident investigations. And I did notice that they've been obviously wrong about not requiring an investigation for that last ULA Vulcan flight, where the rocket lost the nozzle of a solid rocket booster (an antiquated design in part because it can have no "off" switch, only a "kaboom" switch) mid-ascent. Considering that case makes me worry a little more about political adversaries than military ones. The contrast between "I want to build cities in space" Bezos speeches versus "you can't launch that often!" Bezos protests is particularly sad.
You're welcome. It is an argument, though, to be fair, not a proof. I have to admit I felt better about seeing them attempt the tower catch after they finished stacking the second Texas launch tower, and I would have felt better still if they had the second tower operational already.
Man, say whatever you want about Elon. The guy comes up with crazy ideas that break with some convention, and is willing to stick with them until they either fail or miraculously work out. Cybertruck is having some birthing pains but I will timidly predict that it has achieved a decent level of acceptance and we'll see imitators soon. AND he's good at picking the right people to implement these ideas.
Like there's still probably some irreducible risk from this approach, but to pluck it out of the space of possible solutions when it wasn't even on anybody else's radar? Damn.
"Willing to stick with it" does not sound as impressive when you're just funding the work, not personally putting your nose to the grinder 12 hours a day. And maybe Musk does put his nose to the grinder, but I don't see him doing that. I see him posting midwit takes on twitter.
He needs a PR team to tell him what to do to look more like the modern Tony Stark and less like, well, Trump.
Assuming this is your real sentiment and not just trolling, have you ever been in a team attempting something truly difficult? Not just something that needs lots of structured man-hours and money, but something you don't even know if possible, and other people shy away from?
Leadership really REALLY matters then. It is not the only thing that matters, but you can have every other ingredient aplenty and it will never work without someone truly exceptional leading it.
A modern day Tony Stark is 'impossible' because no one person can achieve the total amount of expertise and do the actual intellectual and physical labor needed to build anything really cool and effective, esp. at scale. You can't really build a magical reactor and suit of powered armor in a cave, with scraps.
If you're only willing to give a guy credit if he personally designs, builds, tests, and produces the end product without delegation, then literally nobody gets credit for cool stuff happening.
Maybe when Elon is fully Neuralinked up and has a squadron of those Optimus robots responding to his very thoughts he could go it 'alone.'
But the dude who can identify, acquire, and direct the necessary experts and keep them motivated and funded long enough to build some cool shit is like 1/3 of the way to being Tony Stark.
My point about Elon has long been that YES, he constantly overpromises and underdelivers. But he still delivers more than his closest competitor so he wins anyway. Overhyping a product matters much less if you're the only one who can deliver anything close to the hype.
At least part of that has to do with him putting in absurd hours and, as we see above, actually adding his technical input to the process rather than just sitting back and funding other workers. Indeed, the Principal-Agent problem would suggest that if you just sit back and fund people, they will optimize for getting paid rather than delivering results, so I think he throws himself in there mainly to make sure everyone else is, too.
There is a reason SpaceX has developed and deployed this capability, and none of the national space organizations and none of the private space organizations succeeded or even tried.
When I was younger, I vaguely recall sci-fi where ships landing like that was how spaceports worked. I thought it was distinct rather than cool since it seemed so unrealistic, but here I am decades later suitably impressed.
Watched it live with my daughter this morning. She wasn't alive before SpaceX was landing rockets. She was very excited about how cool the rocket looked taking off and the engines firing. The significance of the tower catching the rocket was lost on her. She's seen so few rocket launches, it's just immediately taken for granted, like they all do that and always have. In a way it makes me optimistic about the new space age she will live in. She wants to visit space one day in that childish way kids who see a rocket take off always do. But that might actually be a thing normal-ish people get to do in her lifetime, unlike mine.
It's funny when you see the SpaceX progress in this direction taken for granted even by critics of SpaceX. When they lost that booster on landing recently instead of being able to refly it for the 25th time, people started talking about how wasteful that was. Does nobody know what happens to every single rocket booster actively being flown by everyone other than SpaceX? Rocket Lab reflew one engine once, and they're hoping to refly a whole booster in the near future, but other than that? Vulcan? Splash. Long March? A cloud of toxic smoke next to a Chinese village. Artemis I? A multibillion dollar fish habitat.
I watched it live, but didn't see this until just now.
Mad props to SpaceX for sticking the landing on the first attempt. Its downright uncanny to see something that size moving that fast and that precisely.
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Notes -
Link to landing: https://youtube.com/watch?v=nVNIoQUcFI4&t=48
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Could someone explain why they are doing this?
To catch the rocket booster for reuse I believe.
I meant instead of doing their normal reverse landings, but someone else answered, apparently its better for the engines, and a lighter payload overall.
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@aqouta
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Landing legs are heavy and any mass you lift up lowers payload. You also prevent damage from the engines (which are much more powerful than the Falcon 9 Merlin engine) blasting the surface and reflecting heat/shockwaves back to the ship.
https://x.com/WalterIsaacson/status/1844870018351169942
Notably, the relationship is exponential, so lowers it more than you would expect.
The laziest possible search gives me 550,000kg for the rocket, 8,000 kg for payload, and 2,000kg for the landing legs, so 0.33% of total but an astonishing 25% of payload. Given the exponential relationship, even the 0.33% could have real impact, so 25% is somewhere between "holy shit" and "did lagrangian mess up the math and/or use poor data"?
Hard to find good data while they're still revising and testing. 550mT is probably high since a previous version was under 400mT for both stages put together, but they've beefed up both heat shield and booster a bit since and I dunno how much. Payload is probably around 40mT reusable right now but no telling for sure until they start doing real orbits. Landing legs on both stages would probably be 8% or so of dry mass, 32mT, but only mass on the upper stage trades off 1:1 with payload, so I'd guess they'd lose 40% of payload with v1 Starship, and maybe bring that down to 10 or 15% by v3.
Huh. That's actually not as bad as I'd have guessed. Either they're so good at guidance now that they consider the catch to be "easy", or they were afraid of losing even more mass budget during development (that 40mT is down from a 100mT goal), or they're really not kidding about their real goal for the catches being cadence.
Musk claims he wants to just set a booster back on the launch mount after a catch (as they just practiced late yesterday) and stack the next ship on to launch again an hour later (as they probably won't practice for years). Sounds crazy to me, but I though catching the giant rocket in more-giant robot arms was crazier, so what the hell do I know?
I suspect that's one fight he'll lose on regulatory grounds. Space travel isn't quite regulated like the FAA, but aircraft maintenance requirements are no joke and no small part of why airline scandals become such a big thing, even as those same maintenance standards are why airline safety is so exception. The federal government is willing to accept some form of risk by SpaceX in the name of R&D, but if/when flights fail because of the complications of one flight compromise the next, maintenance delays can be enforced.
This is especially true if the inevitable accidents knock out a tower. One of the logistical issues of the catch-strategy is that it makes the towers a far more 'brittle' chokepoint. Previously, towers needed to just be able to set up the rocket in the first place, but the rocket could land more or less wherever that was a suitable pad. Now the rockets can only land in one place, and if a tower is damaged then no flights what-so-ever can land or launch from there until it is re-established. Which is to say, a single landing accident could take out a launch site for days / weeks / even months.
What that means for Musk is that the boosters will likely need to be re-inspected / re-certified. That would likely entail lowering them to the ground, driving them over to a maintenance facility, and otherwise doing more than an hour of work. The exception would be if a government was willing to provide a waiver for this requirement, say in time of conflict... but in such a conflict, an adversary who could justify a need to launch more payloads into orbit would also have the capacity to target the towers by various means, meaning, again, safety and reliability issues. And this, in turn, would bring the comparison of how governments regulate military aviation, which in some respects is more intense than civil regulations (because the government actually owns the expensive thing).
Now, don't get me wrong- it's all still very impressive- but this is one of those areas where the salesmanship and technical capacity starts to run against other actor interests.
A typical (so typical they did another two this morning and nobody paid attention) Starlink launch has the booster fire its engines, then shut them down, then fire them again for a reentry burn, then shut them down, then fire them again for the landing burn. For a return-to-launch-site mission like their two last month there's also a fourth startup and shutdown for the boostback burn.
There may be someone at the FAA who thinks four ignitions in a row (where the second ignition aims the rocket back at the coast of Florida!) without inspection is fine, but six ignitions in a row with only a brief inspection after the third is crazy, but I doubt it. The feds are pretty good about making distinctions between airline safety (where we're down to something like 1 fatal incident per million commercial flights and rightly proud of it) or astronaut safety (where NASA wants 1-in-250 or better) vs unmanned flight safety. In the most extremely opposite case, unmanned test flight safety, FAA rules have been as lenient as "yup, both halves of that Starship sure screwed up and exploded right where you warned us they might screw up and explode; carry on" after the 3rd test.
The FAA has rightfully cracked down on a bunch of Falcon 9 issues recently, and Starship shouldn't be any better, but it shouldn't be any worse. Not doing a return-to-landing-site or return-to-tower didn't save SpaceX from those crackdowns. Booster fails its 24th landing, on an unmanned ship, in the middle of nowhere, in a NOTMAR zone behind a "Beware of the Leopard" sign? Falcon 9 grounded for days. Second stage deorbit burn is 0.5 seconds too long and it burns up slightly short of where it was expected to burn up? Falcon 9 grounded for weeks. It doesn't matter whether there's a ship or a tower that might get damaged on a failed landing; they'd get grounded for an investigation of what led to any landing they didn't expect to fail, to find any root cause that might affect other phases of flight too.
The FAA hasn't been obviously right about how they license SpaceX flight plan changes lately (though it was nice that they finished the IFT-5 license as quickly as they did in the end), but that's a separate issue from incident investigations. And I did notice that they've been obviously wrong about not requiring an investigation for that last ULA Vulcan flight, where the rocket lost the nozzle of a solid rocket booster (an antiquated design in part because it can have no "off" switch, only a "kaboom" switch) mid-ascent. Considering that case makes me worry a little more about political adversaries than military ones. The contrast between "I want to build cities in space" Bezos speeches versus "you can't launch that often!" Bezos protests is particularly sad.
This is a fair argument, and I appreciate you taking the time to make it.
You're welcome. It is an argument, though, to be fair, not a proof. I have to admit I felt better about seeing them attempt the tower catch after they finished stacking the second Texas launch tower, and I would have felt better still if they had the second tower operational already.
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Man, say whatever you want about Elon. The guy comes up with crazy ideas that break with some convention, and is willing to stick with them until they either fail or miraculously work out. Cybertruck is having some birthing pains but I will timidly predict that it has achieved a decent level of acceptance and we'll see imitators soon. AND he's good at picking the right people to implement these ideas.
Like there's still probably some irreducible risk from this approach, but to pluck it out of the space of possible solutions when it wasn't even on anybody else's radar? Damn.
"Willing to stick with it" does not sound as impressive when you're just funding the work, not personally putting your nose to the grinder 12 hours a day. And maybe Musk does put his nose to the grinder, but I don't see him doing that. I see him posting midwit takes on twitter.
He needs a PR team to tell him what to do to look more like the modern Tony Stark and less like, well, Trump.
Assuming this is your real sentiment and not just trolling, have you ever been in a team attempting something truly difficult? Not just something that needs lots of structured man-hours and money, but something you don't even know if possible, and other people shy away from?
Leadership really REALLY matters then. It is not the only thing that matters, but you can have every other ingredient aplenty and it will never work without someone truly exceptional leading it.
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A modern day Tony Stark is 'impossible' because no one person can achieve the total amount of expertise and do the actual intellectual and physical labor needed to build anything really cool and effective, esp. at scale. You can't really build a magical reactor and suit of powered armor in a cave, with scraps.
If you're only willing to give a guy credit if he personally designs, builds, tests, and produces the end product without delegation, then literally nobody gets credit for cool stuff happening.
Maybe when Elon is fully Neuralinked up and has a squadron of those Optimus robots responding to his very thoughts he could go it 'alone.'
But the dude who can identify, acquire, and direct the necessary experts and keep them motivated and funded long enough to build some cool shit is like 1/3 of the way to being Tony Stark.
My point about Elon has long been that YES, he constantly overpromises and underdelivers. But he still delivers more than his closest competitor so he wins anyway. Overhyping a product matters much less if you're the only one who can deliver anything close to the hype.
At least part of that has to do with him putting in absurd hours and, as we see above, actually adding his technical input to the process rather than just sitting back and funding other workers. Indeed, the Principal-Agent problem would suggest that if you just sit back and fund people, they will optimize for getting paid rather than delivering results, so I think he throws himself in there mainly to make sure everyone else is, too.
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Organization and management is also labor.
There is a reason SpaceX has developed and deployed this capability, and none of the national space organizations and none of the private space organizations succeeded or even tried.
Boeing having to get rescued from their latest boondoggle, despite that company having more funding than GOD, should be an illustrative point.
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Not a substantive comment but SpaceX is just so cool
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Nostalgic, in a way.
When I was younger, I vaguely recall sci-fi where ships landing like that was how spaceports worked. I thought it was distinct rather than cool since it seemed so unrealistic, but here I am decades later suitably impressed.
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Absurd. Insane. Spectacular.
I didn't expect them to catch the booster at all on this attempt, but I'm so glad to be wrong.
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Watched it live with my daughter this morning. She wasn't alive before SpaceX was landing rockets. She was very excited about how cool the rocket looked taking off and the engines firing. The significance of the tower catching the rocket was lost on her. She's seen so few rocket launches, it's just immediately taken for granted, like they all do that and always have. In a way it makes me optimistic about the new space age she will live in. She wants to visit space one day in that childish way kids who see a rocket take off always do. But that might actually be a thing normal-ish people get to do in her lifetime, unlike mine.
It's funny when you see the SpaceX progress in this direction taken for granted even by critics of SpaceX. When they lost that booster on landing recently instead of being able to refly it for the 25th time, people started talking about how wasteful that was. Does nobody know what happens to every single rocket booster actively being flown by everyone other than SpaceX? Rocket Lab reflew one engine once, and they're hoping to refly a whole booster in the near future, but other than that? Vulcan? Splash. Long March? A cloud of toxic smoke next to a Chinese village. Artemis I? A multibillion dollar fish habitat.
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I watched it live, but didn't see this until just now.
Mad props to SpaceX for sticking the landing on the first attempt. Its downright uncanny to see something that size moving that fast and that precisely.
Right? Our normal intuitions about momentum just give up in the face of that much power.
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