SpaceX landed a rocket on a boat five years ago:
Five years ago today, SpaceX successfully landed a Falcon 9 rocket first stage on a boat.
[...] After nearly a dozen failed attempts, subsequent landings soon filled a SpaceX hangar full of used rockets. This caught some SpaceX engineers off guard. "It even surprised us that we suddenly had ten first stages or something like that," Hans Koenigsmann, one of SpaceX's earliest hires, said a few years afterward. "And we were like, well, we didn't really account for that."
[...] Yet the economics pretty much require landing downrange of a launch site. That's because over the course of a launch, a rocket gradually leans from a vertical to horizontal orientation as it prepares to release its second stage on an orbital trajectory. At this point it requires tons of propellant to arrest this horizontal velocity and reverse course back to the launch site. It is much more fuel-efficient to have the rocket follow a parabolic arc and land hundreds of kilometers from the launch site.
This is borne out in the performance data. A Falcon 9 rocket that lands on a drone ship can lift about 5.5 tons to geostationary transfer orbit, compared to 3.5 tons for a rocket that lands back at the launch site. Had SpaceX not figured out how to land the Falcon 9 first stage on a drone ship, it would have eliminated about 40 percent of the rocket's lift capability, a huge penalty that would have negated the benefit of reusing rockets.
[...] In the 2000s, SpaceX very nearly died on multiple occasions as a fledgling company with its Falcon 1 rocket. In the 2010s, SpaceX iterated on the Falcon 9, first winning contracts for NASA launches and commercial satellites. These missions, in turn, gave SpaceX engineers the breathing room to experiment with recovering and refurbishing used rockets. Today, thanks to this, they're able to fly first stages rapidly and at significantly reduced costs.
Now, with Starship, SpaceX is seeking to reuse a much larger orbital vehicle and bring back not just the first stage—in this, the Super Heavy booster is a lot like the Falcon 9 first stage—but the Starship vehicle as well. This represents a whole other challenge, as Starship will be coming back to Earth at orbital velocities, about Mach 23. And after this, SpaceX engineers will need to figure out how to refuel Starships in low Earth orbit, and then how to keep a crew alive en route to Mars, on the surface, and on the way back home. Each of these represents a huge engineering difficulty.
This story would not be complete without SpaceX's How Not to Land an Orbital Rocket Booster.
(Score: 0) by Anonymous Coward on Friday April 09 2021, @06:05AM (5 children)
This whole "action/reaction" thing is so primitive and wasteful. We have to learn how to use gravity to pull us to the destination. You can't get lost that way, and it's more stable. Rockets are like balancing on a pinhead.
(Score: 3, Touché) by khallow on Friday April 09 2021, @08:09AM
Currently, gravity pulls down and we don't want rockets to go that way. Nobody has any way to change that in the near future.
Getting lost has never been a problem with rockets. And rockets are surprisingly stable. Balancing on a pinhead is greatly exaggerating the instability of the problem. It's more like balancing a large broom on end. It doesn't take that much effort to keep the broom balanced. Sure, the RUD (rapid unscheduled disassembly) still happens due to control system goofs, fuel sloshing, engine failures, plumbing failures, etc but the basic control problem is solved. And they've come up with many clever solutions for failure recovery and payload survivability (particularly, passenger survivability).
(Score: 2) by DannyB on Friday April 09 2021, @04:04PM
It's better to balance on a smart person than on a pinhead.
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(Score: 2) by takyon on Friday April 09 2021, @05:02PM (2 children)
The only new propulsion you're going to see in the next 40 years is maybe nuclear. NIMBY.
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(Score: 1) by khallow on Saturday April 10 2021, @04:00AM (1 child)
FTFY. I know you're aware of those space-side propulsion systems, takyon.
(Score: 2) by deimtee on Saturday April 10 2021, @04:33AM
If any of those orbital propulsion techniques end up scaling well I could see Musk building a rotating tether by then with them at the center point. We have materials now that are plenty strong enough and Spacex has the controls engineers to make pop-up-and-grab-on work.
(Of course it would probably whip all of those internet constellation satellites out of orbit too, so maybe not.)
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(Score: 3, Funny) by Anonymous Coward on Friday April 09 2021, @12:41PM
Story queue is way too slow... I read about this on another site literally five years ago.
(Score: 0) by Anonymous Coward on Friday April 09 2021, @01:37PM (5 children)
so i was wondering if there is some special case on some alien planet (with aliens) where the kids go out in their garden, fill up a bottle and screw on their "made with dad in the garage" exhaust nozzle, light the fuse and manually tose (accelerate) in up ... and the whole thing works. no valves, motors, pumps or such ... basically the fuel pushes into the nozzle, ignites, accelerates the system up (thus adding "g" s to fuel) which "prefers to drop into the nozzle" only to ignite and push "up more" but now with less weight ... etc.
so basically, maybe ... hmmm ... a alien planet with 100g's and some exotic atmosphere?
so this "crazy idea" came from ... hmmm... errr... could a human rockets efficiency be improved if we were not constraint by having to limit acceleration and keeping a passenger or cargo from turning into mush? say ... 20g to Ggooooooo!? from the start at launch pad ...
(note: nozzle pushes everything up but the fuel liquid is actively pumped down ... with more "g's" the liquid would flow/drain down faster (and the pump would also move more, like walking in a moving train))
(Score: 2) by sjames on Friday April 09 2021, @02:48PM
Water rockets do that. Basically fins, a nozzle, and a 2 liter soda bottle. Fill bottle with water and compressed air and let it fly. Not much of a payload, limited altitude. Reliability is not something you would risk a life on, but it could never lift a person anyway.
(Score: 1) by khallow on Friday April 09 2021, @06:15PM (3 children)
But it wouldn't change the fundamental problem. You still need a huge amount of velocity (7.5 km/s to reach LEO and 11 km/s to reach escape velocity) just to get anywhere.
And a planet with high gravity is going to be much harder to leave than one with low gravity.
(Score: 0) by Anonymous Coward on Friday April 09 2021, @10:04PM (2 children)
well thanks for reply.
my original post was excessively "elaborate".
in a nut shell the question was just: are we limited by human physical limitations (max 10g's?) to improve rocket efficiency?
methinks " improving human limits (technologically or even genetically) should be second place. the first order if business should be improving rockets to the extreme.
afterall space is huge, the distances enormous and putting limitations like "can a human survive it" from the start seems like tying mount everest to your ankle and asking you to do 100m sprint in 12 seconds ...
(Score: 1) by khallow on Saturday April 10 2021, @03:56AM (1 child)
The catch is that a good enough rocket that launches frequently trounces an extreme rocket that launches infrequently. The economics of space flight, most particularly the economy of scale from higher launch frequency dominates the technology considerations. Further, a lot of technology improvements, like reusable vehicles and components or launch abort systems (to recover payloads from launch accidents), only make sense with a high launch frequency too, because otherwise you're amortizing the costs over a small number of launches.
(Score: 0) by Anonymous Coward on Saturday April 10 2021, @06:48PM
i agree, high acceleration is a problem. in human history "extreme acceleration" was mostly involved with death (arrows, sword and helabard swings, cannon balls, other balls, sudden car stops -aka- crashes etc.)
i just want to reiterate, that space is enormous. we need to get over "the fear of acceleration" if we realistically want to travel in outer space.
for the time being, assuming a greater acceleration would improve rocket efficiency, that is, accepting that it is NOT human rated (for the time being), it would firstly be used for cargo transport, like pizzas and sardines to saturn or jupiter ^_^ (one would assume that fragile cargo, like a telescope, would by that time be packaged into smaller pieces that are high G proof-ed and then assembled at the intended location?)
as for reliability, i am not convinced that a high G rocket inherently can be used less frequent and aprori needs a longer "refurbishment time".
(Score: 0) by Anonymous Coward on Friday April 09 2021, @01:58PM
Snore... wake me up when they land a boat on a motherfucking rocket. Noobs.