Moon Starship

[lykos]

Dosn't this look like the "payload dispender" we have seen at BC/Starship?

[Ionmars]

In the photos of a possible HLS elevator, there appears to be vertical guide rail on the side of HLS to keep the elevator in alignment as it rides up and down.. It appears to be centered in front of the hatch door opening (lower left photo), where it impedes access to the elevator. If they want to unload packages as wide as the elevator they will likely replace this with two rails, one on each side of the opening. Alternatively, they could just place wheels on each side of the elevator, which would allow it to ride up and down with the wheels in light contact with the hull.

[DistantTemple]

In the photos of a possible HLS elevator, there appears to be vertical guide rail on the side of HLS to keep the elevator in alignment as it rides up and down.. It appears to be centered in front of the hatch door opening (lower left photo), where it impedes access to the elevator. If they want to unload packages as wide as the elevator they will likely replace this with two rails, one on each side of the opening. Alternatively, they could just place wheels on each side of the elevator, which would allow it to ride up and down with the wheels in light contact with the hull.

I suspect they are currently using an off the shelf construction elevator system at the moment. As you say split rails to edges when they build their own.
Wheels would allow tipping, and require load balancing, and anchoring. Rails will hold it horizontal. Wheels might do for an emergency system, but IMO the main elevator will definitely be rails.

[Ionmars]

Another feature SpX will probably use on the elevator is to curve the bottom front edges of the elevator cage to match the curvature of the HLS hull. This way the cage will be in close proximity with the hull during loading and unloading. Also with safety latches to firmly hold the cage in place during loading.

Added: Latches could be located on HLS hatch opening rather than on the elevator.

[StarshipTrooper]

In the photos of a possible HLS elevator, there appears to be vertical guide rail on the side of HLS to keep the elevator in alignment as it rides up and down.. It appears to be centered in front of the hatch door opening (lower left photo), where it impedes access to the elevator. If they want to unload packages as wide as the elevator they will likely replace this with two rails, one on each side of the opening. Alternatively, they could just place wheels on each side of the elevator, which would allow it to ride up and down with the wheels in light contact with the hull.

I suspect they are currently using an off the shelf construction elevator system at the moment. As you say split rails to edges when they build their own.
Wheels would allow tipping, and require load balancing, and anchoring. Rails will hold it horizontal. Wheels might do for an emergency system, but IMO the main elevator will definitely be rails.

At first glance the system appears similar to the elevator used on the High Bay at Boca Chica.

[Ionmars]

The distance between the elevator cage and the hull can be controlled by extending and contracting the boom arm. So the cage could be moved closer to contact the hull during loading and move slightly away for descent.

Swaying of the cage during descent may be minimal as I understand that wind speed on the moon is minimal. 

[tbellman]

This is in response to a discussion that started in the HLS Option B and the Sustaining Lunar Development Phase (Appendix P) thread in the "Missions To The Moon (HSF)" board, but it is vearing off-topic for that thread.

Irrespective of how they're accounted for, it's pretty clear that the HDL solicitations are for Artemis crew-critical pieces of hardware:  habs, rovers, power systems, etc.  Nobody's going to be taking any risks with those.

NASA seems to consider putting those things on landers that have performed at most a single earlier lunar landing.  Heck, they even plan on putting humans on landers with just a single prior landing!  Do you think that is less risky than doing a second rendez-vous and refilling of tanks?

I agree that the odds of a catastrophic failure are fairly low, but the odds of a failed RPOD or a failed additional engine restart are high enough to make the payload people squirrelly.

Have you asked any actual payload people what they think?  You appear to be deadly afraid of it, but what about NASA and others?  The only reference I have seen to someone being "squirrelly" about it, is in the source selection statement for HLS Option A, where Kathy Lueders wrote that "operational risks in Earth orbit [...] can be overcome more easily than in lunar orbit, where an unexpected event would create a much higher risk to loss of mission".  I believe that is specifically for HLS; it will take longer to arrange a replacement tanker for a failed tanking mission to NRHO than to LEO, and that can cut into the NRHO loiter time.

Would SpaceX be interested enough in developing this to spend an extra six tanker launches per attempt?  Only if they think that there are tens to hundreds of heavy lunar missions in the future, and that most of them aren't going to an established base with some kind of ISRU propellant capability.  Those two things aren't necessarily mutually exclusive but it would be kind of an odd future.  If you have high scale, there are better investments for providing return prop.

If SpaceX believe there is a single customer who wants a return mission to the Moon, and who requires a demonstration of that return capability before their real mission, then it makes sense to do that demonstration on a mission where someone else picks up half the tab.  (Assuming SpaceX has enough cash on hand to pay for their own half; cash flow and liquidity can of course put limits on when they are able to do such tests.)  For that matter, I suspect some customers may even be happy and excited to be part of such a demonstration, if it paves the way to future return missions.  And the sooner they can do such a demonstration, the sooner they can get customers paying for real return missions (including crewed missions).

And sure, I don't think it is a slam-dunk that they should try to return every Starship going on lunar missions, but I do think it is in their interrest to prove out return missions quite early, and preferably on missions where others are paying for part of it.

[TheRadicalModerate]

Have you asked any actual payload people what they think?  You appear to be deadly afraid of it, but what about NASA and others?  The only reference I have seen to someone being "squirrelly" about it, is in the source selection statement for HLS Option A, where Kathy Lueders wrote that "operational risks in Earth orbit [...] can be overcome more easily than in lunar orbit, where an unexpected event would create a much higher risk to loss of mission".  I believe that is specifically for HLS; it will take longer to arrange a replacement tanker for a failed tanking mission to NRHO than to LEO, and that can cut into the NRHO loiter time.

It doesn't require fear to want to minimize risk, especially for expensive crew-rated pieces of hardware.  RPODs carry some amount of risk.  Engine restarts also carry some risk.  If you can minimize those, you're increasing the chances for mission success.  That's just good project management.

FWIW, I get the impression that, for whatever reason, NASA views an RPOD as a fairly risky operation.  I don't know why that is exactly, and how that risk compares to other common mission events, but an argument to minimize their use seems to crop up a lot.  (NB:  Some of that is political, since if there's one thing that SLS/Orion is good at, it's minimizing RPODs.)

However, note that neither the Option A nor B conops requires a fueling operation with crew anywhere but on the ground.  Cargo payloads are obviously different, but if you can get away with a single depot refueling in LEO, that does seem to be the irreducible minimum of complexity for using either an LSS or vanilla Starship on a cargo mission.

If SpaceX believe there is a single customer who wants a return mission to the Moon, and who requires a demonstration of that return capability before their real mission, then it makes sense to do that demonstration on a mission where someone else picks up half the tab...

If that's the case, then doing a post-lunar-ascent refueling in LLO seems to be the way to go.  Then the only extra risk being incurred by the guinea-pig mission is the risk of the lunar ascent.  And the cislunar refueling technology will mostly have been proven out via Option B pre-mission refueling in NRHO.

[edzieba]

It's a reasonable assumption that any crew lander will be capable of return without any external resupply. That means that whilst risk in supplementary landers (equipment and supplies) are mission risks, they are not crew risks. If all of your logistics landers only produce craters, any crew mission in flight is not at direct risk to crew survival, but only now limited to a short duration mission with limited activities.
Propellant transfer with crew on board is however a direct risk to crew survival (unlike propellant transfer prior to crew launch as with the proposed HLS CONOPs).

[TheRadicalModerate]

It's a reasonable assumption that any crew lander will be capable of return without any external resupply. That means that whilst risk in supplementary landers (equipment and supplies) are mission risks, they are not crew risks. If all of your logistics landers only produce craters, any crew mission in flight is not at direct risk to crew survival, but only now limited to a short duration mission with limited activities.
Propellant transfer with crew on board is however a direct risk to crew survival (unlike propellant transfer prior to crew launch as with the proposed HLS CONOPs).

If all of your logistics landers produce craters, I think it's fair to say that the crew mission that needed them will be postponed until they're replaced.  But habs, fixed or roving, aren't going to be cheap pieces of equipment.  I'd guess that they'll each be more than $1B to develop and manufacture, which puts them into a fairly paranoid mission assurance class.

In true SpaceX fashion, they can do anything they want once a payload is delivered, as long as what they do doesn't add risk to the payload.  That puts two constraints on any attempt to recover:

1) Ascent debris can't risk the deployed payload.
2) An extra pre-descent refueling and burn can't be allowed.

So if you can top off in LEO (one RPOD with a depot tanker) and manage to do LEO-LS-LLO with no refueling, and you can avoid putting a pebble-size piece of regolith through your brand new hab on ascent, then recovering an HDL- or CLPS-certified Starship is feasible.

Of course, this is really a vehicle that's not quite a vanilla Starship, and not quite an LSS.  It has:

a) Landing legs.

b) Probably landing thrusters.

c) TPS and elonerons for EDL.  (Note:  It's pointless just to bring it back to LEO, because there's no easy way to put cargo on it.)

Is that worth developing?  Eventually, sure.  Early on, probably not.  Just put your cargo on an LSS, land it, and forget about it.

[Negan]

Note:  It's pointless just to bring it back to LEO, because there's no easy way to put cargo on it.

I wouldn't be surprised if two Starships docked, that the cargo doors would face directly across from each other based on the latest rendering of Starship docking with the Depot. I could see that being helpful since transferring one large pallet of equipment from one static opening directly across to another static opening doesn't seem to be much of a challenge even if it was a automated robotic process.

[TheRadicalModerate]

Note:  It's pointless just to bring it back to LEO, because there's no easy way to put cargo on it.

I wouldn't be surprised if two Starships docked, that the cargo doors would face directly across from each other based on the latest rendering of Starship docking with the Depot. I could see that being helpful since transferring one large pallet of equipment from one static opening directly across to another static opening doesn't seem to be much of a challenge even if it was a automated robotic process.

Hatch, payload bay doors, or chomper on the launcher?  Note that the LSS lander will probably be something else.

I assume that by "pallet", you really mean "payload attachment capable of surviving the launch environment, but then capable of being released while grappled by a robotic arm, rather than deployed into space like everything else that a vanilla Starship will support".

Who's providing this robotic arm?

Have you worked out the spatial requirements of rotating a payload 180º so it goes into the LSS payload bay rightside-up, or are you going to require it to be launched upside-down?

What sorts of payload attachments are needed in the LSS ensure that the payload can survive 3 or 4 separate burns and a landing, then reliably release?

This stuff is all doable.  But I wouldn't describe it as not seeming to be a challenge.  And I imagine that, given that the expendable LSS is cheaper until prop launches are really cheap, the R&D costs of developing it would be hard to justify.

[Negan]

Have you worked out the spatial requirements of rotating a payload 180º so it goes into the LSS payload bay rightside-up, or are you going to require it to be launched upside-down?

I don't know what you mean here. The latest render shows the Starship and Depot docking side to side with both ships noses pointing the same way. The payload will already be rightside-up.

[TheRadicalModerate]

Have you worked out the spatial requirements of rotating a payload 180º so it goes into the LSS payload bay rightside-up, or are you going to require it to be launched upside-down?

I don't know what you mean here. The latest render shows the Starship and Depot docking side to side with both ships noses pointing the same way. The payload will already be rightside-up.

Fair point.  I was thinking about the old tail-to-tail orientation.  Although you still need to rotate it 180º about the z-axis, unless the arm is OK reaching across the payload into the target bay.

[Negan]

Have you worked out the spatial requirements of rotating a payload 180º so it goes into the LSS payload bay rightside-up, or are you going to require it to be launched upside-down?

I don't know what you mean here. The latest render shows the Starship and Depot docking side to side with both ships noses pointing the same way. The payload will already be rightside-up.

Fair point.  I was thinking about the old tail-to-tail orientation.  Although you still need to rotate it 180º about the z-axis, unless the arm is OK reaching across the payload into the target bay.

I don't think you understand what a pallet is.

Edit: Actually I think you're envisioning the arm pulling the payload pallet out of the bay, and I'm envisioning the arm pushing the payload pallet from one bay to the other.

Edit: Also SpaceX has or will have reliable electronic mechanisms that can hold a pallet. For example what will end up securing the Starship clam shell or the payload door through launch and landing might be a good place to start.