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42 votes
Accepted

Can a spaceship land on an icy body using retropropulsion? wouldn't the ice melt?

Sorry for the length of this, but it brings up some interesting facts and possibilities. The moons you mention, Titan, Europa, and Enceladus, are three very different places. Titan has a relatively ...
Tom Spilker's user avatar
  • 18.3k
28 votes
Accepted

More efficient SpaceX landings?

One problem is that towing speed of the ASDS is pretty slow. Around 5-8 mph. This means that to get 500 miles off shore, you need almost 100 hours of towing to get there, and 100 hours to get back. ...
geoffc's user avatar
  • 79.9k
24 votes

More efficient SpaceX landings?

The falcon 9 has 3 return modes, depending on the launch profile. The first involves barges and has 2 burns. The reentry burn to prevent burn up in the atmosphere and the landing burn, there is no ...
OrangePeel52's user avatar
  • 2,571
19 votes

Can a spaceship land on an icy body using retropropulsion? wouldn't the ice melt?

It's probably going to be less of a concern than you'd guess. The icy worlds of our solar system have essentially no atmosphere, so the surface materials will sublimate directly to vapor and be ...
Russell Borogove's user avatar
13 votes
Accepted

Falcon-9/Starship landing on an uneven surface

There are two possible answers to this, although you probably won't like either of them. Answer 1: They don't. Falcon 9 only lands on prepared landing sites and Starship doesn't exist yet. Answer 2: ...
Jörg W Mittag's user avatar
9 votes

Flying saucer shape rocket vs cylindrical shape rocket

Cylinder shaped large rocket is not suitable for vertical landing due to its high center of mass and bulky weight. SpaceX seems to have determined that a long cylindrical stage is perfectly suitable ...
Russell Borogove's user avatar
8 votes

Why was the water-landed Falcon 9 B5-B1050 towed backwards for retrieval?

I suspect this is due to the bottom having easier mounting and attachment solutions. Additionally the interstage section (top of the booster) was damaged when it fell over which might prevent crew ...
Dragongeek's user avatar
  • 19.2k
7 votes

What is the difference between a "Suicide burn" and a "Hoverslam"?

I would say there's one substantial difference: Suicide burns are normally a matter of choice, you light your rocket as late as possible to save fuel. The Falcon 9, however, has no choice in this ...
Loren Pechtel's user avatar
7 votes
Accepted

Could the SSMEs of the SLS do retro burns?

They cannot, because SSMEs cannot be restarted in flight. See this answer for the details as to why.
Organic Marble's user avatar
6 votes

What is the advantage of the "Mechazilla arms" over fitting the Super Heavy booster with landing struts?

This seems (to me) a more complicated procedure requiring more advanced hardware. Not necessarily. Instead of thinking about "catching the booster with the arms", think about "the ...
Jörg W Mittag's user avatar
5 votes
Accepted

How would vertical landing scale with size - does bigger = "easier" (actually)?

The mass of a pendulum doesn't affect its period, but the length does; the longer your rocket, the slower it will tip (in degrees-per-second) while off-balance, and the more time you have to ...
Russell Borogove's user avatar
5 votes

Falcon-9/Starship landing on an uneven surface

Falcon 9 likely could land on a somewhat uneven surface because its leg-base is rather wide and the legs contain one-time-use crush-able aluminum honeycomb impact absorbers. Still, this surface would ...
Dragongeek's user avatar
  • 19.2k
5 votes

Why SpaceX decided to forgo the opportunity of a mock soft-landing (on water) for Super Heavy?

Edit: Incorrectly answered with information about the Starship vehicle. ErinAnne's answer here correctly answers the question which is about the Super Heavy first stage. Please upvote that one and if ...
GremlinWranger's user avatar
5 votes
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Why SpaceX decided to forgo the opportunity of a mock soft-landing (on water) for Super Heavy?

Just to back up Christopher James Huff's comment, the timeline and graphics on SpaceX's Starship Flight Test page both indicate a soft-landing attempt for Super Heavy. From the flight infographic on ...
Erin Anne's user avatar
  • 11.8k
4 votes

Falcon 9 vs Apollo Landing: Key Differences?

But this leaves me wondering: in what ways were the Apollo landings different from a Falcon 9 stage 1 landing? I'm interested in the controls perspective more than the physics of the problem (e.g., ...
Russell Borogove's user avatar
4 votes
Accepted

How is New Shepard the first suborbital booster to successfully perform a powered vertical soft landing?

Why do they say that New Shepard is the first one to do so? Because December (first successful landing of a Falcon 9 booster) is after November (first successful landing of New Shepard).
Jörg W Mittag's user avatar
4 votes
Accepted

Can VTVL rockets use dampers like high rise buildings to provide stability?

If you have a large weight above the center of gravity, and the stage gets off-vertical a little, that large weight now exerts a torque that pulls the rocket off-vertical some more. A weight at the ...
Hobbes's user avatar
  • 128k
4 votes

Controlling suicide burn landing location in a python simulation?

Why is acceleration of the engines should not be defined as the current acceleration? alt_burn is not an acceleration. It is, I think, the altitude to start the ...
Russell Borogove's user avatar
3 votes

Hover Slam Landing: How is it Done?

There is nothing official from SpaceX so any algorithm will be based on assumptions. Unlike your question SpaceX will be very interested indeed in exactly where their rocket lands and they will also ...
Slarty's user avatar
  • 9,720
3 votes

Alternative to GPS navigation for vertical landing, especially on other planets

...for the purpose of vertical landing especially on other planets, what is the alternative to GPS navigation? Terrain recognition and imaging, and if there's a landing pad, some radio and optical ...
uhoh's user avatar
  • 149k
3 votes

Alternative to GPS navigation for vertical landing, especially on other planets

There are a couple of questions here, I will try to answer them all. Q1: Is GPS only valid below GEO orbits? A1: For the most part yes, because GPS satellites transmission are pointed at earth. (Minor ...
Knudsen Number's user avatar
3 votes

What is the difference between a "Suicide burn" and a "Hoverslam"?

Hoverslam is the same thing as Suicide Burn. Just sounds less suicidal. The engine does not run full throttle during Hoverslam/Suicide Burn. The engine power is adjusted constantly to account for the ...
William Ce Liu's user avatar
3 votes
Accepted

What guidance algorithm does Falcon 9 use during powered descent and landing?

This paper surmises autonomous precision vertical landing for rockets, both on Earth and other planets and written by a SpaceX lead for Falcon 9 landing, though in a private capacity. It describes the ...
GremlinWranger's user avatar
3 votes

Terminal velocity on reentry?

You're correct that terminal velocity varies. For a given vehicle in a given attitude relative to the airstream (i.e. a particular angle of attack), though, it varies only with the air density and ...
Russell Borogove's user avatar
2 votes

Falcon 9 vs Apollo Landing: Key Differences?

The Apollo landings and the Falcon 9 landings are superficially similar in that landed vehicles on a large spheroidal object. The differences are huge. Apollo: No atmosphere. Falcon 9: A significant ...
David Hammen's user avatar
2 votes

State vector update on reentry

For shuttle, the ground uplinked a state vector about two hours before the deorbit burn. See the Deorbit Prep Checklist, page 1-13. Action is listed as SV UPLINK. The vector was updated during entry ...
Organic Marble's user avatar
2 votes

SpaceX Dragon: why no powered landing?

Elon Musk can explain. “The reason we decided not to pursue (powered landings) heavily is it would have taken a tremendous amount of effort to qualify that for safety, particularly for crew transport,...
Organic Marble's user avatar
1 vote

How is New Shepard the first suborbital booster to successfully perform a powered vertical soft landing?

Even though New Shepard did not achieve orbit nor put anything in orbit (because it was not designed to do so) it did land after achieving a 100.5 km apogee suborbital trajectory which it makes it in ...
Gabriel Rodrigues's user avatar
1 vote
Accepted

Falcon 9: How many engines on first burn in two-burn reentry?

According to simulations by Declan Murphy, the creator and developer of Flight Club, the profile is as follows: Light center engine at 80% thrust. ~3.3s later, light additional two engines at 80% ...
Jörg W Mittag's user avatar
1 vote

Alternative to GPS navigation for vertical landing, especially on other planets

So, you have basically 2 questions: 1.) vertical landing ... 2.) Navigation outside of earths shere of influence Let us start with 1.) : Typical extra-terrestial landers are equipt with radar ...
CallMeTom's user avatar
  • 3,298

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