Readying the rocket for return

louis · 2021-04-08 15:14:18

I've been wondering what will need to be done to ready a Starship for the return journey to Earth as part of Mission One. Here's my checklist of definites and possibilities (welcome your comments and suggestions):

1. A choice has to be made between two human rated Starships as to which will be the return craft. What factors will be taken into account in making that decision. I guess there will be a major visual inspection of both the exterior of the rocket body and the engine area. Will Space X provide a mobile gantry/crane? Would that be possible? Alternatively a Mars drone might be used for visual inspection.

2. As a safety feature, does any residual fuel/propellant have to be removed (ie pumped out) after landing?

3. How does Space X prepare a rocket for reuse? Is there a need to flush tanks, or decoke engines or anything like that?

4. All life support equipment to checked and double checked. Similarly, coms.

5. What pre-launch tests and procedures are possible on Mars. Are any sort of pressure tests of tanks possible? Obviously static firing is out of the question, I presume.

6. Presumably the landing zone will be examined again and all surface objects - rocks, stones, boulders or anything that someone's accidentally left lying around - will be removed.

7. I guess there will be some testing of the launch software.

8. Presumably an onboard countdown will be begun a day or two before the launch.

louis · 2021-04-08 17:24:42

9. You obviously will have to load the returning Starship with scientific samples from Mars. That might take some time - getting everything in position and securing it for launch.

GW Johnson · 2021-04-10 09:24:34

There are a whole series of potentially-fatal risks that must be addressed and reduced before this Starship/Superheavy design can even be an orbital transport, much less go to the moon or Mars. Or return from either place. Check out these checklists:

Immediate in far-suborbital flight test:
1. stop the propellant leaks (which may prove impossible in an absolute sense
2. assuming there will always be risk for a methane-air fire in the engine bay, armor all wiring and control plumbing against fire exposure
3. quit screwing around and get the concrete pad landing leg design "right"
4. quit screwing around and get to work on a rough-field landing leg design, which you will need before you reach orbit for an off-site abort (obstructions, bearing surface, surface overall slope, and surface localized variation all of concern)

By the time flight test reaches high suborbital speed (entry heating potentially fatal):
1. make sure your tiles will stay on as the shell flexes under high windblast loads
2. make sure the localized heating won't be too high for your planned windows (a very fatal risk for shuttle)
3. implement rough field landing legs by the time you reach these flight conditions: an off-site abort landing becomes certain; and don't fail to design for fully-refueled weight: you may have no choice but to fly it out of there
4. you will have to solve the zero-gee ullage problem for restarts, as well as anti-slosh baffle problems when tanks are nearly empty (something analogous to open-cell foam is a possible candidate)

By the time you reach orbital flights:
1. update rough-field landing leg design to hold up fully-fueled Starship on very soft sand for Mars regolith conditions
2. get good at on-orbit refueling (you may have to revise concept if you don't like thruster propellant consumption); this requires hundreds of refueling operations to demonstrate reliability, before lives ever depend upon it
3. make sure you have a good radiation shelter design ready for crewed Starships; you will need to penetrate deeply into the Van Allen belts to make lunar landing missions feasible
4. you need to demonstrate hundreds of rough field landings from orbit, before attempting such on the moon or Mars
5. you will need to develop and demonstrate an ablative alternate heat shield for entry speeds above 10 km/s, beyond which radiative heating from the plasma dominates, and radiant plasma opaqueness limits re-radiative cooling of ceramic refractory tiles

NOW you are ready to begin to worry about how to refill a Starship sitting on a planetary surface! Before you ever send one anywhere!

GW

Last edited by GW Johnson (2021-04-10 09:25:30)

louis · 2021-04-10 19:30:45

Lol! Well I don't think I was unaware of those challenges.

My question related to how the hell we get a Starship back to Earth orbit which I suspect is the biggest challenge of all - because you really don't have much help on the surface of Mars. There's just your crew of whatever - 6 to 20 (doesn't make much difference - pretty small number of people) and the equipment you will have is going to be v limited. Will they be able to have a gantry crane so they can examine the exterior all the way to the top? I've no idea.

I think all the other stuff you mention is much more doable.

I suppose a starting point would be to ask what do they actually do to their reusable F9s when they land? What do they do to make them ready for relaunch?

GW Johnson wrote:

There are a whole series of potentially-fatal risks that must be addressed and reduced before this Starship/Superheavy design can even be an orbital transport, much less go to the moon or Mars. Or return from either place. Check out these checklists:
Immediate in far-suborbital flight test:
1. stop the propellant leaks (which may prove impossible in an absolute sense
2. assuming there will always be risk for a methane-air fire in the engine bay, armor all wiring and control plumbing against fire exposure
3. quit screwing around and get the concrete pad landing leg design "right"
4. quit screwing around and get to work on a rough-field landing leg design, which you will need before you reach orbit for an off-site abort (obstructions, bearing surface, surface overall slope, and surface localized variation all of concern)
By the time flight test reaches high suborbital speed (entry heating potentially fatal):
1. make sure your tiles will stay on as the shell flexes under high windblast loads
2. make sure the localized heating won't be too high for your planned windows (a very fatal risk for shuttle)
3. implement rough field landing legs by the time you reach these flight conditions: an off-site abort landing becomes certain; and don't fail to design for fully-refueled weight: you may have no choice but to fly it out of there
4. you will have to solve the zero-gee ullage problem for restarts, as well as anti-slosh baffle problems when tanks are nearly empty (something analogous to open-cell foam is a possible candidate)
By the time you reach orbital flights:
1. update rough-field landing leg design to hold up fully-fueled Starship on very soft sand for Mars regolith conditions
2. get good at on-orbit refueling (you may have to revise concept if you don't like thruster propellant consumption); this requires hundreds of refueling operations to demonstrate reliability, before lives ever depend upon it
3. make sure you have a good radiation shelter design ready for crewed Starships; you will need to penetrate deeply into the Van Allen belts to make lunar landing missions feasible
4. you need to demonstrate hundreds of rough field landings from orbit, before attempting such on the moon or Mars
5. you will need to develop and demonstrate an ablative alternate heat shield for entry speeds above 10 km/s, beyond which radiative heating from the plasma dominates, and radiant plasma opaqueness limits re-radiative cooling of ceramic refractory tiles
NOW you are ready to begin to worry about how to refill a Starship sitting on a planetary surface! Before you ever send one anywhere!
GW

SpaceNut · 2021-04-10 19:59:15

The lands are not the same for a falcon 9 versus the starship in that the fuels are different, the return entry speeds are nowhere near each other, and temperature at time of landing let along uncontrolled on Mars would test stress all expose to extreme cold that a falcon 9 never will see.

tahanson43206 · 2021-04-11 05:35:13

Here's another angle on Louis' initiative here ...

Earlier forum members have posted about the business opportunity for an organization (probably a Nation sized organization) to build a landing pad on Mars and accept landing fees from Elon and others for using the facility.

A logical extension of that basic idea is to follow the lead that Louis has provided ... A landing pad is a basic requirement for Starship landing with passengers, so why stop there? The landing pad needs (or at least, ** should have **) a wide variety of support services to attend a landed vehicle.

I read a report recently (yesterday) about the Russian Space Program being in disarray, due to neglect since the glory days of the Soviet era.

The article I read included quotes from current astronauts complaining that the technology they're using is unchanged since the 60's, although I suppose there might have been some small improvements here or there.

Building a landing pad on Mars would be a sufficient challenge to get the Nation's juices flowing again, if Putin is willing to take that on, in addition to his other less noble activities.

(th)

GW Johnson · 2021-04-11 10:01:36

As planned currently, the Spacex Starship does NOT return from Mars to Earth orbit, it makes a direct entry from interplanetary speeds above escape, then lands directly on the surface of the Earth. It does NOT have the mass ratio to make an orbit entry burn into Earth orbit. It does not stop in Mars orbit after its surface launch from Mars, although it could. The advantage of doing so would be to divorce the timing of the launch from the timing required to enter the correct interplanetary trajectory home.

If Spacex will buckle down and solve the rough-field landing problem by the time this craft is first reaching Earth orbit, they will have mostly solved the rough-field landing problems for the moon and Mars, where gravity is lower. The topple-over and obstruction/surface roughness problems apply to landing. The surface bearing strength problem applies more to takeoff, where the mass (and weight) is about 6 times larger. That would eliminate the landing pad construction problem for the first several such craft sent to Mars.

Having that rough-field landing capability enhances reliability in two ways, after landing pads have been constructed on Mars. (1) what if the pad gets damaged for whatever reason right before a ship lands? (2) what if a ship misses the landing pad for whatever reason and makes a rough-field landing instead? Those possibilities are why deleting rough-field capability from future Starships would be a really stupid thing to do.

Just like it was stupid to send the Titanic into service with half or less the lifeboats it needed.

Stupid is as stupid does.

GW

Last edited by GW Johnson (2021-04-11 10:07:15)

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#1 2021-04-08 15:14:18

Readying the rocket for return

#2 2021-04-08 17:24:42

Re: Readying the rocket for return

#3 2021-04-10 09:24:34

Re: Readying the rocket for return

#4 2021-04-10 19:30:45

Re: Readying the rocket for return

#5 2021-04-10 19:59:15

Re: Readying the rocket for return

#6 2021-04-11 05:35:13

Re: Readying the rocket for return

#7 2021-04-11 10:01:36

Re: Readying the rocket for return

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