Moon AND Mars?

[Negan]

Everything but the heat shield, the few aerodynamic controls and certain software segments would be tested by landing on the moon. Most of those would be at least partially tested by the return to earth from the moon.

Simulations are always deficient tests in a variety of ways, especially for a system the scale of ITS. A moon landing would test out the integrated system in a way no simulation on earth could. The only reason to not do such a test would be cost, and the cost would not be all that large relative to the project scale and they could almost certainly find a space agency willing to pick up part of the tab in exchange for delivering a science payload. I will be very surprised if they do not do one at some point before the first Mars mission (or at least before the first human to Mars mission)

I guess I need to spell it out more. What specific tests can't be done in orbit? What specific tests can't be done landing on earth from orbit or from cis-lunar?

So let's say they do decide to test the landing system on the moon. What if it fails on landing or takeoff? All that hardware is now on the moon.  Maybe it's wreckage (which can still be very useful to find out what went wrong) or the whole ship, but it's still on the moon so how do you get to it? You can't! Not without risking another valuable prototype and probably a crew. You could say the same for Mars, but at least Mars is where SpaceX actually wants to go.

[meberbs]

I guess I need to spell it out more. What specific tests can't be done in orbit? What specific tests can't be done landing on earth from orbit or from cis-lunar?

You previously said "simulated on earth" in this context that would mean something like hardware in the loop testing on the ground, not orbital testing. Also, landing on the moon would provide tests for landing in a low gravity environment, in vacuum (Mars is effectively vacuum on final approach), on an unprepared surface, with no GPS support. They would likely always use GPS support landing on earth, to make sure they don't land in a populated area. For various reasons, they would also probably only land on prepared infrastructure as well.

So let's say they do decide to test the landing system on the moon. What if it fails on landing or takeoff? All that hardware is now on the moon.  Maybe it's wreckage (which can still be very useful to find out what went wrong) or the whole ship, but it's still on the moon so how do you get to it? You can't! Not without risking another valuable prototype and probably a crew. You could say the same for Mars, but at least Mars is where SpaceX actually wants to go.

In that case it almost certainly would have failed on Mars as well, but the test cost less, and doesn't delay you by a whole synod. While having access to the failed hardware is nice, it is not necessary, as diagnostic data would be being broadcast back to earth, which could be done on Mars as well, but the data rate might be restricted.

I can't answer "specific tests" in more detail than what I just presented, because that requires knowledge of the ITS subsystem details possibly in more depth than has even been designed yet. It is possible SpaceX will decide that they can test all the relevant parts sufficiently integrated, and in sufficient detail without a moon landing. Considering:
-The marginal cost of a moon landing is low, especially compared to orbital testing
-The unique lunar environment that is closer to parts of a Mars landing than an Earth landing is
-The possibility to do iterative testing if needed without a 2 year delay
-Their plan to send people on the 2nd ITS launched to Mars (desiring proving high reliability, which cooperating space agencies may force on them by this point)
-Their stated willingness to do whatever helps them pay for development (even suborbital transport, which is much more of a tangent)

A moon landing looks like a very probable test.

Edit: I just saw the "MCT tests on the moon" thread in this section, it would probably be best if we continue this discussion to do it there, since we are drifting from the main point of this thread (Does ITS/general low cost access to space allow humanity to pursue the moon and Mars in parallel?)

[Negan]

Also, landing on the moon would provide tests for landing in a low gravity environment, in vacuum (Mars is effectively vacuum on final approach), on an unprepared surface, with no GPS support.

As far as no GPS support goes, they will already need to have tested this with Red Dragon missions since they've said these will have a hand in landing site selection for ITS. Also considering anyplace on earth is better than the moon, I'm sure they could find somewhere to do this.

Landing on unprepared surfaces can certainly be done on earth with the bigger benefit of having easy access to the testing vehicle afterward. Again anyplace on earth is better than the moon.

Not sure why landing on the moon's gravity environment is useful considering it was done successfully almost 50 years ago. Supersonic retro-propulsion is the real difficult part and that can't be tested with a moon landing.

NASA doesn't seem to feel the need to involve moon landing tests with it's Mars systems.

Edit: Also any talk of outside parties dictating testing at this point is just pure speculation. NASA is the only one that has come close with the Red Dragon mission.

[DOCinCT]

To me there is a big difference between designing a spaceship to land on Mars and build an outpost  and then saying let's test this out in cis-lunar space and with a lunar landing
VS
Let's build stuff to go to and stay in cis-lunar space then land on the moon and build a small habitat before we build something to land on Mars and then return.

[Negan]

To me there is a big difference between designing a spaceship to land on Mars and build an outpost  and then saying let's test this out in cis-lunar space and with a lunar landing

The big question for me is has there been any Mars Mission architectures that have proposed a lunar landing test when going the direction above?

[meberbs]

As far as no GPS support goes, they will already need to have tested this with Red Dragon missions since they've said these will have a hand in landing site selection for ITS. Also considering anyplace on earth is better than the moon, I'm sure they could find somewhere to do this.

I don't know why you think "anyplace on earth is better than the moon" logistics of the landing site would be a significant issue. Also, while Red Dragon is a test that will provide useful data for developing ITS, it is not a test of ITS, and that is a huge difference.

Landing on unprepared surfaces can certainly be done on earth with the bigger benefit of having easy access to the testing vehicle afterward. Again anyplace on earth is better than the moon.

Again logistics is an issue, and it still wouldn't be as good of a test without the vacuum conditions etc. They would have access to the moon landed one after it returns to earth at a nice, convenient location. This reminds me that I didn't mention the relaunching from lunar surface which will also be a useful part of the test.

Not sure why landing on the moon's gravity environment is useful considering it was done successfully almost 50 years ago. Supersonic retro-propulsion is the real difficult part and that can't be tested with a moon landing.

Apollo has effectively zero commonality with ITS. It seems like you don't understand the purpose of testing. If you want/need, I can write a short essay in my next post providing a systems engineering 101 for system verification.

NASA doesn't seem to feel the need to involve moon landing tests with it's Mars systems.

It would have been absurdly expensive for NASA to do it for any of the missions they have done, whereas due to its architecture, and doing orbital testing anyway, it is a small marginal cost for ITS.

Edit: Also any talk of outside parties dictating testing at this point is just pure speculation. NASA is the only one that has come close with the Red Dragon mission.

Almost everything on this topic is speculation, you will note that in my last post I stated that it is possible that they skip a lunar landing test, I just don't find that likely given the apparent cost/benefit value.

[Negan]

They would have access to the moon landed one after it returns to earth at a nice, convenient location. This reminds me that I didn't mention the relaunching from lunar surface which will also be a useful part of the test.

So the assumption is ITS will never have any major issues taking off or landing on the moon even in the testing phase of vehicle development, but if it does, such a failure would be inconsequential cost wise and would still benefit the program. Pretty rosy assumptions, but everybody has a right to their opinion.

[meberbs]

They would have access to the moon landed one after it returns to earth at a nice, convenient location. This reminds me that I didn't mention the relaunching from lunar surface which will also be a useful part of the test.

So the assumption is ITS will never have any major issues taking off or landing on the moon even in the testing phase of vehicle development, but if it does, such a failure would be inconsequential cost wise and would benefit the program. Pretty rosy assumptions, but everybody has a right to their opinion.

"No issues" is the exact opposite of the assumption, or there wouldn't be any reason to test. Should I make that intro to systems verification post I mentioned? I won't have time to write it until tomorrow at the earliest.

The cost of a failure (assuming catastrophic failure, which should be relatively low probability) would be less than finding out about that failure on Mars, because finding out about the failure on Mars would have larger delays in the program due to launch window restrictions.

[whitelancer64]

The problem is that while landing on and then launching from the Moon may be a good test run for the ITS rocket engine systems, doing so doesn't really prepare them for landing on Mars. The landing sequences will be very different due to the different environments, particularly Mars' atmosphere, which is about 1/100th that of earth's atmosphere - not "effectively a vaccuum," by any means. Gliding through the air to bleed off speed after atmospheric entry will be a major part of their landing sequence. Testing that would be much easier and cheaper to do here on Earth, for example, they could do a suborbital test flight where they reenter and then glide through the Mars-relevant section of the upper atmosphere.

[guckyfan]

Gliding through the air to bleed off speed after atmospheric entry will be a major part of their landing sequence. Testing that would be much easier and cheaper to do here on Earth, for example, they could do a suborbital test flight where they reenter and then glide through the Mars-relevant section of the upper atmosphere.

It could be very well tested here on earth, I fully agree. But coming in from an orbitals speed to make it more realistic. Probably even looping around the moon for better emulating the Mars entry speed.

But the final descent under engine thrust could be tested slightly more realistic on the moon because the powered phase on earth landing is much shorter. Emphasis on slightly.

[Negan]

The cost of a failure (assuming catastrophic failure, which should be relatively low probability) would be less than finding out about that failure on Mars, because finding out about the failure on Mars would have larger delays in the program due to launch window restrictions.

Are you assuming that successful Moon tests will take the place or lessen Mars ITS testing?

[meberbs]

Gliding through the air to bleed off speed after atmospheric entry will be a major part of their landing sequence. Testing that would be much easier and cheaper to do here on Earth, for example, they could do a suborbital test flight where they reenter and then glide through the Mars-relevant section of the upper atmosphere.

It could be very well tested here on earth, I fully agree. But coming in from an orbitals speed to make it more realistic. Probably even looping around the moon for better emulating the Mars entry speed.

But the final descent under engine thrust could be tested slightly more realistic on the moon because the powered phase on earth landing is much shorter. Emphasis on slightly.

I'd say a bit more than slightly, there are multiple ways that the lunar landing (and relaunch) is a more similar environment to Mars than a similar test on Earth. Of course the aerodynamic aspects have to be tested during the earth return portion.

Since there is definitely some benefit (none of us are in a position to actually quantify this) I think SpaceX is likely to do it. They actually seem to have a tendency to want to test things thoroughly, though the speed they move through iterations makes people think otherwise. For example, they imposed the max drag launch abort test for Dragon on themselves, CST-100's lack of a similar test shows that this was optional.

The cost of a failure (assuming catastrophic failure, which should be relatively low probability) would be less than finding out about that failure on Mars, because finding out about the failure on Mars would have larger delays in the program due to launch window restrictions.

Are you assuming that successful Moon tests will take the place or lessen Mars ITS testing?

What Mars ITS testing? SpaceX's plan for the "Heart of Gold," the first ITS to go to Mars, is for it to be an operational mission delivering the first round of fuel generation equipment for the base. While they will certainly plan for the chance of a loss of mission, it doesn't seem right to consider that part of the test phase of the program.

[guckyfan]

What Mars ITS testing? SpaceX's plan for the "Heart of Gold," the first ITS to go to Mars, is for it to be an operational mission delivering the first round of fuel generation equipment for the base. While they will certainly plan for the chance of a loss of mission, it doesn't seem right to consider that part of the test phase of the program.

It is testing as well as operational. I assume they will fly the first mission fast like they do the crew mission to have similar EDL to test it for the manned flight. If it were purely operational they could do a slow transfer with much higher payload. This ship is not coming back anytime soon, so that reason for a fast trajectory is not relevant.

I want to note that it has been expressed by some, that it is irresponsible of SpaceX if they don't do an earth return unmanned first, before they send crew. Nobody would expect the same from NASA.

[Negan]

While they will certainly plan for the chance of a loss of mission, it doesn't seem right to consider that part of the test phase of the program.

It will be a test the landing system for the first time on Mars, and the next step, sending crew, doesn't happen without it being successful. No amount of Moon landing tests changes this.

[Negan]

If ITS did not have the capability for Lunar landing, I would not suggest this. As it is, lunar landing is quite within the robust capabilities of ITS and this would be a prudent test.

Actually thanks to Steven Pietrobon, we now know Lunar direct is not within ITS capabilities.

[guckyfan]

If ITS did not have the capability for Lunar landing, I would not suggest this. As it is, lunar landing is quite within the robust capabilities of ITS and this would be a prudent test.

Actually thanks to Steven Pietrobon, we now know Lunar direct is not within ITS capabilities.

I am not sure I agree. Steven Pietroban sensibly calculated with the weight of ITS. The tanker version is much lighter and probably can do it without payload. It is of little use for a lunar service but would do quite well for a test.

[Negan]

If ITS did not have the capability for Lunar landing, I would not suggest this. As it is, lunar landing is quite within the robust capabilities of ITS and this would be a prudent test.

Actually thanks to Steven Pietrobon, we now know Lunar direct is not within ITS capabilities.

I am not sure I agree. Steven Pietroban sensibly calculated with the weight of ITS. The tanker version is much lighter and probably can do it without payload. It is of little use for a lunar service but would do quite well for a test.

The tanker is an LEO spacecraft not meant for long duration spaceflight. If the test would only be "slightly" better than what could be done on earth, what's the point of the modifications?

Edit: This also makes the test even more irrelevant due to the fact you're not even testing an accurate copy of the hardware going to Mars.

[meberbs]

While they will certainly plan for the chance of a loss of mission, it doesn't seem right to consider that part of the test phase of the program.

It will be a test the landing system for the first time on Mars, and the next step, sending crew, doesn't happen without it being successful. No amount of Moon landing tests changes this.

It may change whether it lands on Mars successfully the first time, or everything gets delayed an extra synod. I honestly expect they will not send people on the second synod anyway to get more pre-placed hardware and system confidence, but sending people on the 2nd synod is more plausible if they have done moon landing and relaunch tests that give them more confidence in the system.

If ITS did not have the capability for Lunar landing, I would not suggest this. As it is, lunar landing is quite within the robust capabilities of ITS and this would be a prudent test.

Actually thanks to Steven Pietrobon, we now know Lunar direct is not within ITS capabilities.

I am not sure I agree. Steven Pietroban sensibly calculated with the weight of ITS. The tanker version is much lighter and probably can do it without payload. It is of little use for a lunar service but would do quite well for a test.

The tanker is an LEO spacecraft not meant for long duration spaceflight. If the test would only be "slightly" better than what could be done on earth, what's the point of the modifications?

Edit: This also makes the test even more irrelevant due to the fact you're not even testing an accurate copy of the hardware going to Mars.

Actually, as I understand what he did, he just showed doing it requires coordinating 2 ITS, maybe using a tanker as the second one. Also, the tanker should have enough commonality with the ship that a week or 2 going around the moon shouldn't be much of an issue, though it may need large batteries or some added solar panels.

If you went with the use a tanker for landing option, it wouldn't make the test any less valuable. None of the differences are relevant to the test except in a structural sense, and landing on the moon doesn't really add to the structural testing, since it is lower stress than Earth return.

[Negan]

Adding a second spacecraft in a moon test increases more ways that the mission can fail including some that have nothing to do with the Mars mission. It adds more complexity, risk, and cost that can't be hand waved away. Risking one ITS for a test with minimal utility doesn't make sense. Risking two spacecraft makes even less. I totally understand why Musk didn't include it when he presented the development plans.

[Rocket Science]

I guess the could launch a simulated mission with a 9 month deep space and land on the Tibetan Plateau (approx 15,000' Alt.) with optimized TPS and engines for Earth. Stay for a period to test surface ops and lift off from there for return to the launch site.
https://en.wikipedia.org/wiki/Tibetan_Plateau