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The booster is destroyed when it tips over after "landing" vertically on the water. It's like a 20 story building falling over. If you're asking why they don't
by modeless 2y ago
The booster is destroyed when it tips over after "landing" vertically on the water. It's like a 20 story building falling over.
If you're asking why they don't land it on a floating barge like Falcon 9, there are two reasons. One is that landing back on the launchpad lets them refuel and relaunch immediately. The other is that landing legs are big and heavy and significantly reduce the payload capacity. If you're already landing on the launchpad you might as well add arms to catch it. The mass of the arms is free because they're on the tower instead of the rocket, and the rocket only needs tiny nubs to catch on the arms instead of giant legs. Also the arms double as a crane to lift and stack the rocket on the launchpad.
- jojobas 2y ago>immediately So far this hasn't been shown even on much simpler Falcons. The barge gives quite some energy advantage for not having to boost back. Ideally they'd build a capesize kinda barge with chopsticks to catch it in the ocean, then perhaps service what they have to while it's steaming back.
- literalAardvark 2y agoHasn't been shown because they're not meant to be immediately reusable. Spaceship and/or super heavy are (I don't remember the details).
- jojobas 2y agoI'll believe it when I see it.
- avmich 2y agoIt would be good because there are many people who, roughly, refuse to believe their own eyes and keep moving goalposts, misrepresenting what they said or meant earlier, inventing additional conditions, changing their mind etc. If you would honestly believe that Starship can fly frequently when you see it flying frequently, you're already ahead of some.
- jiggawatts 2y agoI remember when people doubted that the full-flow staged combustion methalox engines could work... until SpaceX showed over a hundred of them working now. Then the ULA CEO Tory Bruno claiming that the SpaceX photos of the first Raptor 3 were “partially assembled”, to which Gwynne Shotwell replied with this: https://x.com/Gwynne_Shotwell/status/1821674726885924923?t=vT35PMKOMiUfWg6hun2f_A https://x.com/Gwynne_Shotwell/status/1821674726885924923?t=v...
- avmich 2y agoI'd consider that cheating on the Gwynne side. It could be argued if chamber tilting mechanism is part of the engine - after all, it was added separately to NK-33 - but surely for Raptors it's considered an integral part, the fire test was then a test of chamber, not the engine :) . Though Gwynne had to answer positively, having little good choice.
- timschmidt 2y agoThe outer ring of engines on Superheavy do not tilt. They're rigidly mounted and exclude even the engine start hardware which is contained in the launch mount, further reducing weight. And they're only used during liftoff, not for boostback or landing.
- avmich 2y agoRaptor is non-functional without tilting. That is, it's possible to build rocket where all Raptors are fixed, but that defeats some ideas of Raptors. And I haven't seen tilt mechanisms considered parts of the rocket. So, while engines without tilting have been used - e.g. NK-15 - Raptors aren't from that category.
- modeless 2y agoRaptor is used in a non-tilting configuration on both the booster and ship. You could certainly design a rocket to get to space with only non-tilting raptors, if you wanted. It would be silly to consider it incomplete without tilt, even if Starship does have some tilting ones too. Consider it two variants if you like, both complete on their own.
- modeless 2y agoFalcon 9 wasn't designed for immediate reuse. Immediate reuse is just a theory right now, but SpaceX has an excellent track record of turning their theories into reality. SpaceX did purchase some oil rigs with the intention to turn them into launch platforms, but later abandoned the idea. It's probably something they will return to later once Starship is flying regularly. You're right that avoiding the boostback burn is a big advantage. But maybe they don't need to bring the booster back after it lands on a platform, it can just launch again from there. Maybe they could have a bucket brigade of launch platforms ringing the Earth!
- ethbr1 2y agoThe oil rig idea is brilliant, especially for cargo flights. I.e. the bulk of near / intermediate term launches Far fewer people care if you "oops" an unmanned rig in the ocean.
- CableNinja 2y agoThe issue is logistics, and in this case isnt an easy solve. You have to get fuel, and the rocket, out to a pad in the ocean, and have to deal with a rocket lift on varying conditions. If you dont want to do most of that, then the only option is putting your manufacturing on the rig too, which negates lifting a rocket, but instead makes the rig huge, and requires having a train of ships in and out 24/7 to keep it supplied. There was even a company in the late 90s that tried oil rig launch platforms and ultimately abandoned it.
- ethbr1 2y agoMost heavy lift is transported by barge over water anyway. Since the 2 stages of Starship aren't intended to be road mobile, due to size, there's no transportation benefit to being land-accessible. So really the main concern is piping propellant... but afaik some rigs off the shallow coast of Texas are directly piped to land? The main benefit you get is terrifying the FAA et al. less, as the consequences of a missed catch are now out in the ocean.
- 2y ago
- double0jimb0 2y agoAlso, a rocket that hangs doesn’t need near the structural beef as one that is designed to withstand landing on its feet.
- askvictor 2y agoNot convinced about this argument; wouldn't the forces during the slow-down burn be applied much the same as the from the feet?
- ars 2y agoActually no - the forces travel inside the "tank" of the rocket, and push against the top of it. The force doesn't push against the nozzle of the engine.
- slow_typist 2y agoSame pressure in the tank as in the nozzle? That doesn’t sound right. It would burst.
- ben_w 2y agoSame force, not same pressure. The nozzles are relatively small. I wouldn't want to try to intuit what the force distribution would be and how much is carried through each component of the structure, though — that's what simulations are for.
- krisoft 2y ago> The force doesn't push against the nozzle of the engine. I’m not sure what you are saying here. The force pushes against the nozzle, (and of course the walls of the combustion chamber.) That is the purpose of the rocket engine, to push the rocket forward. They are not just there to provide mood-lights.
- ars 2y agoI said "nozzle", as in the side walls of the engine. The force doesn't transfer via those walls, rather it goes through the full tank of the rocket and pushes against the top.
- redmajor12 2y agoSo is it cheaper to dump the booster in the ocean then land it back at the tower and then have to dispose of it?
- modeless 2y agoThe booster always follows a trajectory for an ocean landing until it passes a bunch of safety checks, and then it diverts to the launchpad. This way a failure early on can't cause it to crash on land. What probably happened is it failed a safety check (e.g. a sensor read out of range) and so it didn't divert to the launchpad. It's cheaper to dump the booster in the ocean than to build a new launch tower if it's destroyed in a failed landing. They have an assembly line for boosters, but only one fully complete launch tower at the moment.
- sneak 2y agoThe launch tower takes multiple months to build. The orbital launch mount and launch tower and quick disconnect hardware is all custom and expensive and huge. They call it “Stage 0”. Losing that is an order of magnitude more of a setback than losing a Stage 1.
- avmich 2y agoI guess they didn't optimize the towers to be fast-buildable :) because there are several obvious ideas.
- Davidzheng 2y agohave they tried a giant net? lol
- Titan2189 2y agoYes: https://youtu.be/oTH3mq7SsK4?t=14 https://youtu.be/oTH3mq7SsK4?t=14
- bmitc 2y ago> One is that landing back on the launchpad lets them refuel and relaunch immediately. How do they structurally, electrically, etc. checkout the rocket after landing?
- mewc 2y agoAn ops problem for later. At least now its possible!
- bmitc 2y agoIt seems like a pretty expensive assumption that landing the rocket is enough. Relaunching the rocket, which requires inspection and validation procedures and technology, is just as important as landing it.
- modeless 2y agoThey haven't done it yet and nobody outside of SpaceX knows their specific plans. Of course we can speculate that they will design sensors and cameras to replace any previously required manual inspections.
- raldi 2y agoLike a falling chimney (google it), it breaks because the top can't fall fast enough.
- chrisco255 2y agoAre they going to need legs when they land the Starship on the moon or Mars?
- jmercouris 2y agothe booster does not need legs, only starship does
- modeless 2y agoYes, also the lunar variant won't need a heat shield so that will compensate for the extra leg mass. Not sure what their plans are for a heat shield for Mars.
- cwillu 2y agoThey're planning on catching starship as well however, as the in-orbit refueling will require a lot of starship launches that aren't going anywhere except orbit and back.
- murkt 2y agoYes, Starship needs legs to land on the Moon or Mars. They will be lighter than legs for Earth landings, as Moon/Mars have lower gravity. Not sure about the amount of fuel needed to land, as there is much less atmosphere on Mars, and none on the Moon. I would still guess that it needs less fuel there as well.
- __m 2y agoDon't they also need fuel to lift off again?
- perryizgr8 2y agoI think Elon has said that it's going to be a one way trip to Mars.
- lutorm 2y agoThat will have to happen through in-situ resource utilization. aka making the fuel on Mars.
- panick21_ 2y agoAlso, a ship big enough to carry Starship booster would be huge. And then what port infrastructure do you use to bring it to land and transport it to your launch pad? You would basically need your own port right next to the launch site.