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Maybe this is a stupid question, but why is it better to land the rocket on a ship instead of having it plop into the ocean and float for a few hours or days un
by username223 11y ago
Maybe this is a stupid question, but why is it better to land the rocket on a ship instead of having it plop into the ocean and float for a few hours or days until a nearby ship can scoop it up?
- Klathmon 11y agoThe sea is filled with all kinds of stuff that pretty much ruins anything it gets into. The cost of cleaning, refitting, and fixing issues from a splash landing is more expensive than doing it this way. At least that's what SpaceX's whole model is pretty much based on.
- Retric 11y agoThey could add a water tight cap to both ends. But this gets into weight / stress issues. PS: Being literal rocket scientists I a going to assume landing is a much more workable design.
- vrfcodf 11y agoWhat both ends? :-) This is a rocket, not a plastic tube. And who plugs them, and where. In space, before landing?
- partisan 11y agoThis made me laugh out loud. I think that one of the great things that comes out of this is that we start using our imaginations and trying to understand the whys and hows of space travel. It's really exciting to see.
- deleted 11y ago[deleted]
- username223 11y agoThanks. I'm just surprised that the cost of damage from seawater to a dumb rocket with a parachute and floats is more than the cost of a smart rocket making a much more error-prone landing on a tiny ship.
- lallysingh 11y agoAfter R&D you're just paying for the additional fuel to land safely. The control systems are already there for the other parts of the trip. Also, I assume it's a lot easier to be sure that the rocket's in good shape if you don't have to check the interior for leaks, and whatever chemicals seeped in with the water?
- madlag 11y agoThere is no such thing as a dumb rocket : to get down, they are using almost exactly the same stuff they use to get up, weight wise: they use the gimbaled engines, and the nitrogen attitude thrusters. The only additional devices are the grid fins, to control aerodynamically the descent, and the legs. Then you have to write the right software, and it does not weight much more ;-)
- samstave 11y agoIs this the first rocket with legs? Seems like every thing else in history has really been a missile. This thing can land, so seems like it's literally the first rocket. Do we have a definition of missile vs rocket?
- ygra 11y agoA missile historically has been anything that was thrown or launched. Nowadays it usually means a self-propelled weapon. A rocket is just something with a rocket engine. Note that missiles do not need to use rocket engines and rockets don't need to carry warheads.
- Retric 11y agoThat and a little extra fuel. But, as you say probably less weight than you might think. Also, getting dunked in water probably adds quite a bit of new stresses so you would need a stronger rocket shell which is more wight.
- will_hughes 11y agoAside from what Klathmon says, the rocket is actually quite fragile. Falling into the ocean would cause it to break up. Even the one they 'soft landed' (a practice run before landing on the barge) broke up.
- peeters 11y agoYes, think of the stage as a Coke can. It takes orders of magnitude more force to crumple it by pushing on the top of the can than by pushing on the side. The first stage is the same way; it is designed to withstand forces along the longitudinal axis (thrust and drag) but not really from the sides. The sides just have to withstand the pressure of the Coke/fuel.
- neverminder 11y agoThe short answer - sea water is highly corrosive and rockets are not exactly built water-tight.
- deleted 11y ago[deleted]
- js2 11y agoThat's what was done with the Space Shuttle SRB's, but those were basically completely remanufactured. https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Boo... Also, an SRB is relatively simple compared to a liquid-fuel rocket.
- vermontdevil 11y agoElon has said that the engines are the biggest cost of the rocket. Having these engines exposed to salt water would drive the costs up. See the SRB from Space Shuttle launches. NASA thought the ocean splash and recovery would keep the costs down. It didn't. Ended up the cost to refurb and launch is almost equal to building a new one. Elon wants to avoid this hence these barge or land returns.
- AmitShipEasy 11y agoTell me again which engines get corroded by sea water but not by combustion and re-entry
- CydeWeys 11y agoYou really don't see how being dunked in water is different than going through the atmosphere? You could pretty easily put a heatshield on a car and have it survive high atmospheric speeds, but dunk it in water and you'll fry out the electronics and destroy the engine. You're arguing against decades of actual experience in rocket technology. Just read up on what happened with the space shuttle SRBs.
- stcredzero 11y agoAnd those were really just sections of stout metal tube. They didn't have things like high precision turbopumps in them.
- CydeWeys 11y agoGood point. Solid fuel rockets are quite different in construction than liquid fuel rockets. They are less worth reusing because what is left isn't as valuable as a liquid fuel rocket, but they are also easier to reuse post-dunking because they aren't as complex. It's still a wash for them. Still, it says something that no actor has ever even bothered attempting to reuse a liquid fueled rocket that is landed in water. The only successful track record of reuse of liquid fuel rockets is the space shuttle, and those landed on a runway. And that isn't preserving the fuel tanks for reuse, mind you, just the engines.
- mikeash 11y agoBecause of https://en.wikipedia.org/wiki/Square-cube_law https://en.wikipedia.org/wiki/Square-cube_law In short, big stuff is fragile. You can't tip over something the size of a large office building an expect it to survive.
- reportingsjr 11y agoThis has been asked many, many times. Im surprised no one has mentioned pretty much the biggest reason. They are figuring out vertical landings so that when they go to other planets they can land, possibly refuel, and take back off without having to get the rocket back upright. There also aren't seas on Mars to gently splash the rocket down on. :)
- netman21 11y agoPrototype, prototype, prototype. Break the whole system of launch vehicles down into parts. Perfect each part. One of those parts, a soft landing, is very dangerous to surrounding environs. So perfect the process out at sea. Once you gain confidence, land the rockets back at the processing facility.
- ufmace 11y agoSeawater is corrosive and freshly-run rocket engines are hot, with heat speeding up chemical reactions. Dunking the engine in seawater would basically instantly destroy it. The engines are most of what they want to save, so that's a no-go. It would also have to slow to a near-stop by itself to not be destroyed by the force of hitting the water. Considering that you can do all that with the stuff already on the rocket, seems easier to add some legs and land it than to figure out a way to make it float, survive the seas for a day or 2, and get a ship with a crane tall enough to pick it up and load it.