totm dec 2023 Artemis Discussion Thread

[sevenperforce]

You actually end up with better performance, not worse performance, if you eschew propellant transfer altogether for expendable, replaceable tanks for the crew capsule. Instead of carrying 1.1 tonnes of propellant in its tanks to transfer into the capsule, the lander module would carry a couple of pressurized tanks on its sides that would be detached via Canadarm and mated to structural umbilicals on the sides of the capsule. It only saves a little mass -- the weight of what would otherwise be empty tankage on the lander module -- but it's something. It also gives some additional options. For example, you could have a "stretched" version of the tank on hand with enough props to give the space taxi dV to LLO and back -- enough to rescue a stranded capsule.

On the other hand, if you just love microgravity propellant transfer and want to go all in, you can make the monolithic crew vehicle/landing module/ascender fully reusable. Send it up on a Falcon 9 or an Atlas V 521 and let it go to the Gateway under its own power. Then all you have to do is find a way to get 9 tonnes of propellant to the Gateway (plus your transfer vehicle) whenever you want to do a lunar mission.

One reason to prefer the reusable crew capsule approach, whether with onboard propellant or replaceable tanks, is that it offers a commonality element for unmanned lunar deliveries. Cut back to a single engine and load it up with cargo atop a Falcon Heavy, and it can drop serious tonnage on a one-way trip to anywhere on the lunar surface. Using the same lander for cargo descent and crew ascent would be tough to pull off under any other circumstances, but it really works here.

[sevenperforce]

Thinking about the crew ascent vehicle also being an independent cargo descent vehicle reminds me of the Blue Moon lander. Braked into LLO by the residuals of a New Glenn upper stage, it can deliver up to 4.5 tonnes to the lunar surface. Accordingly, it is almost exactly the right size to act as a lander/ascent module for a crew capsule. Dual-expander hydrolox is not ideal in comparison to pressure-fed hypergolics but it would be much lighter.

[tater]

25 minutes ago, sevenperforce said:

Thinking about the crew ascent vehicle also being an independent cargo descent vehicle reminds me of the Blue Moon lander. Braked into LLO by the residuals of a New Glenn upper stage, it can deliver up to 4.5 tonnes to the lunar surface. Accordingly, it is almost exactly the right size to act as a lander/ascent module for a crew capsule. Dual-expander hydrolox is not ideal in comparison to pressure-fed hypergolics but it would be much lighter.

I honestly default to Blue Moon as the lander until I see someone else bend metal.

 

Bezos will build it anyway, after all.

 

[sevenperforce]

47 minutes ago, tater said:

I honestly default to Blue Moon as the lander until I see someone else bend metal.

Bezos will build it anyway, after all.

I feel like the presumed reliability of pressure-fed hypergolics will be a strong argument in their favor, at least for the ascent vehicle. But proven flight heritage can change that. If Bezos has delivered dozens of payloads to the lunar surface without a hitch on turbopumped hydrolox, the possibility of using the exact same platform as a landing-and-ascent module underneath a reusable crew capsule becomes much more attractive.

[tater]

11 minutes ago, sevenperforce said:

I feel like the presumed reliability of pressure-fed hypergolics will be a strong argument in their favor, at least for the ascent vehicle. But proven flight heritage can change that. If Bezos has delivered dozens of payloads to the lunar surface without a hitch on turbopumped hydrolox, the possibility of using the exact same platform as a landing-and-ascent module underneath a reusable crew capsule becomes much more attractive.

Yeah, I think that an Artemis crew landing in 2024 is far less likely than Starship landing there in 2024 (and I don't see that as terribly likely, either, lol). Hypergolics make the most sense because distributed launch to Gateway means that any system would be smart to be designed with long dwell times at Gateway built in.

[jinnantonix]

4 hours ago, tater said:

Yeah, I think that an Artemis crew landing in 2024 is far less likely than Starship landing there in 2024 (and I don't see that as terribly likely, either, lol). Hypergolics make the most sense because distributed launch to Gateway means that any system would be smart to be designed with long dwell times at Gateway built in.

SpaceX and Blue Origin are a long way from getting their respective large launch vehicles to orbit, let alone getting fully approved human rating.  Honestly, Starship just looks like a silly PR stunt, who is going to pay for a human rated launch on this craft?  Cargo versions of BFR and New Glenn will make SLS obsolete, and the sooner that happens the better.  It won't be for at least 5-10 years, so at best will engage at Artemis 4.

While the Artemis Program lunar lander construction is contracted, NASA is still be under-writing the human rating. I think this issue not given the weight it deserves, and remains the main reason why I believe NASA and SLS will be the most likely to get humans to the moon first. 

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It's not gonna have an RTG.

Then the crew will freeze and suffocate on the floor of Shackleton Crater.

Edited October 12, 2019 by jinnantonix

[tater]

29 minutes ago, jinnantonix said:

SpaceX and Blue Origin are a long way from getting their respective large launch vehicles to orbit, let alone getting fully approved human rating. 

They're about as far away from reaching orbit as SLS, actually, maybe 6 months behind or so (if SLS hits late 2020).

Human rating? SLS isn't flying anyone til over a year after Artemis 1, and Orion is not a lunar lander. So either something to land gets human rated in record speed (and 2024 pretty much requires that the first time it ever exists as a spacecraft it flies with people aboard), or it's not happening. You apparently missed my point---that 2024 is not a thing (point was not not that "Starship pwns SLS").

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Honestly, Starship just looks like a silly PR stunt, who is going to pay for a human rated launch on this craft?  Cargo versions of BFR and New Glenn will make SLS obsolete, and the sooner that happens the better.  It won't be for at least 5-10 years, so at best will engage at Artemis 4.

"Human rated" is arbitrary. NASA is more risk averse than ever (look at the Bridenstine comments from Hawthorne, he basically said any chance of a loss of life was not acceptable). Space will be "test pilot" dangerous for a while, NASA needs to mitigate risk, but embrace the fact that being an astronaut is extremely dangerous. The first bunch of Shuttle flights were 1:9-1:20 chances of LOC (retroactive risk assessment). I have said in the SpaceX thread that I don't see crew flights as happening any time soon on SS/SH, but that they will likely just fly it uncrewed, and develop safety assessments based on actually flying vehicles. Note that unlike even Shuttle, they have the potential (once they get SS reuse to be a thing) to actually do airworthiness testing, since the exact same vehicle will be reflying. "Man rating" is only a thing because every single rocket is a new vehicle, never flown again. (NASA trusts Soyuz entirely based on a flight record which is basically the same as Shuttle, BTW).

SLS being made obsolete in 5-10 years? The first all-up SLS/Orion mission is 2022-2023 (Artemis 2). That's 3-4 years from now as a reality check. NG will certainly be flying, and I'd bet money SS is as well as a semi-reusable (operational reuse of SS... yeah, dunno about that yet, I'll wait and see, but S1 is not hard for SpaceX, and it kills SLS even as a "traditional" giant F9).

 

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While the Artemis Program lunar lander construction is contracted, NASA is still under-writing the human rating. I think it is that after that is most not given the weight it deserves, and the reason why NASA and SLS will be the most likely to get humans to the moon first. 

Depends on what you mean by "getting to the Moon." SLS/Orion likely gets people to a distant lunar orbit first, for sure. The lunar surface? I find it unlikely that SLS plays any role in that aspect at all, I think the lander can get to the Moon entirely by "not SLS" or it's not happening. I think any lander needs to be tested. In the Apollo era, that meant crew messing around with the LM short of landing, and on missions that current NASA would consider suicidally risky, honestly. I would assume that any lander proposed for humans would be landed uncrewed as a test as a minimum requirement. That means commercial launches or it never happens (certainly not in the 2024 timeframe).

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Then the crew will freeze and suffocate on the floor of Shackleton Crater.

They're not supposed to land on the floor of the crater, the proposal is to land on the almost perpetually sunlit rim. First landing of brand new, untested lander. Great idea to land in a pitch black crater, where you cannot visualize the surface.

They'll use APUs, and maybe solar as well.

Edited October 12, 2019 by tater

[jinnantonix]

19 minutes ago, tater said:

They're not supposed to land on the floor of the crater, the proposal is to land on the almost perpetually sunlit rim.

Wrong.

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First landing of brand new, untested lander. Great idea to land in a pitch black crater, where you cannot visualize the surface.

That's why NASA is contracting out to get low cost, light weight science payloads there first.  The surface will be accurately mapped and modeled, and landing sites will be picked out.  The landing of anything in Shackleton Crater will be automated and will not rely on visuals.

Edited October 12, 2019 by jinnantonix

[tater]

21 minutes ago, jinnantonix said:

Wrong.

Link, please.

 

21 minutes ago, jinnantonix said:

That's why NASA is contracting out to get low cost, light weight science payloads there first.  The surface will be accurately mapped and modeled, and landing sites will be picked out.  The landing of anything in Shackleton Crater will be automated and will not rely on visuals.

The maps I have seen for already chosen CLPS lander sites are not even polar. One Draper vehicle was looking at a polar site, but they specifically mention the site requiring sunlight (solar power).

BTW, if a human is not ever flying the lander (sensible, I agree) then they will certainly need an all-up test of the lander all the way to the surface.

[jinnantonix]

1 minute ago, tater said:

Link, please.

Posted 27 minutes ago (edited)

  46 minutes ago, tater said:

They're not supposed to land on the floor of the crater, the proposal is to land on the almost perpetually sunlit rim.

Link please.

LOP-G in NRHO is to ensure access to the south pole.  Landing at the south pole is to investigate the availability of water ice for manufacturing fuel.  This ice is ONLY located in quantity in the permanent darkness of the crater floor.  Landing on the rim does not meet the mission objectives.  Obviously.

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The maps I have seen for already chosen CLPS lander sites are not even polar. One Draper vehicle was looking at a polar site, but they specifically mention the site requiring sunlight (solar power).

BTW, if a human is not ever flying the lander (sensible, I agree) then they will certainly need an all-up test of the lander all the way to the surface.

Correct, but that is just the first phase.  Of course humans are not going to be landed in Shackleton Crater without an accurate robotic survey and robotic testing of a full scale craft.  I am agreeing with comments that state that 2024 for first crewed landing is not possible, a successful uncrewed landing must be completed first.

[Ultimate Steve]

21 minutes ago, jinnantonix said:

LOP-G in NRHO is to ensure access to the south pole.  Landing at the south pole is to investigate the availability of water ice for manufacturing fuel.  This ice is ONLY located in quantity in the permanent darkness of the crater floor.  Landing on the rim does not meet the mission objectives.  Obviously.

Don't have a link right now but I thought the idea was to land in a light area that is very close by to a dark area so you have the benefit of having light but also ice nearby. By the time that they will seriously be considering isru they will almost certainly have a rover there to take them the distance from the landing area to the ice.

[jinnantonix]

Here is a model of the two stage lander,  This was simulated successfully and has just enough dV to launch from the LOP-G, land on the lunar surface and return to the LOP-G. 

The ascent vehicle comprises of a 3.5t Orion pressure vessel with RTG (yes, it needs RTG), ladder, and is assumed to have a mass of 4.0t.  It uses 4 x AJ10-190 engines at ISP = 316 (vac), assumes 2+2 redundancy, which tests really well.  The craft weighs just under 16t fully fueled so theoretically can be launched to TLI by a Falcon Heavy.  The expendable transit vehicle is just a big hypergolic fuel tank with a tight cluster of 3 x SuperDRAC engines.  It has a mass of 28t fully fueled, but could be launched partially fueled on a Falcon Heavy.  I have assumed both craft expend dV ~ 800m/s for rendezvous with LOP-G. 

The problem is that it actually takes two launches of a partially fueled transit vehicle on a Falcon Heavy along with docking and fuel transfer at the LOP-G to ready the craft for transit from LOP-G to lunar surface and return to LOP-G.  So to complete just one crewed lunar surface mission requires 4 x launches of the Falcon Heavy, plus crewed launch of the SLS/Orion.  Ouch.

At this point, I am thinking that using a 3.5t Orion pressure vessel is not going to work and that a purpose built and much smaller 2-man lunar lander is needed if the proposed two stage lander is going to succeed as part of the Artemis program.  

 

 

 

30 minutes ago, Ultimate Steve said:

Don't have a link right now but I thought the idea was to land in a light area that is very close by to a dark area so you have the benefit of having light but also ice nearby. By the time that they will seriously be considering isru they will almost certainly have a rover there to take them the distance from the landing area to the ice.

Have you seen the sides of Shackleton Crater?  Way too steep for a rover.

I read somewhere that there was a proposal to power ISRU in the crater by positioning automated mirror reflectors on the crater rim.  Feasible I suppose, but the setup would be costly and expensive, and prone to reliability issues that could spell disaster.  

OTOH, use a RTG.

[tater]

1 hour ago, jinnantonix said:

LOP-G in NRHO is to ensure access to the south pole.  Landing at the south pole is to investigate the availability of water ice for manufacturing fuel.  This ice is ONLY located in quantity in the permanent darkness of the crater floor.  Landing on the rim does not meet the mission objectives.  Obviously.

Landing IN the crater has never been discussed as far as I know.

The whole point of that crater is that it has rims that are in near constant sunlight. Investigating the floor would be best done by robots. The chances of a landing in the bottom in early missions? Zero, I'd say.

Also, and this is pretty critical: Artemis III (whichever the first crew landing would be) is a photo op. They're not taking a pic of the first woman on the moon in the dark, with naught but LED lights illuminating a little patch of ground.

[Ultimate Steve]

Plus, the moon landing deniers would have a field day if it landed in absolute darkness due to how easy it would be to fake. Not that that's a planning concern, but it is a side effect.

[jinnantonix]

59 minutes ago, tater said:

The whole point of that crater is that it has rims that are in near constant sunlight.

No, the whole point of the crater is that it is thought to contain millions of tons of recoverable raw materials for fuel manufacture.

It may be unpopular, but nuclear power is needed to research and establish the manufacturing of those fuels.

 

 

[tater]

13 minutes ago, jinnantonix said:

No, the whole point of the crater is that it is thought to contain millions of tons of recoverable raw materials for fuel manufacture.

Artemis III will not use ISRU. That's way down the line.

The hunt for water is certainly behind the choice of the polar REGION, but they have not talked about landing IN the crater with people. If I am wrong, it should be trivial to link a NASA doc with contrary information.

 

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It may be unpopular, but nuclear power is needed to research and establish the manufacturing of those fuels.

Nuclear is certainly not unpopular with ME. They're not putting an RTG on Artemis III, however. That has nothing to do with what I think about nukes (love 'em, actually). Any robot rover down in the crater will necessarily have an RTG (it's dark. It might have to have a few (recent RTGs have been 300W each).

ISRU down there... RTG won't cut it, probably, need an actual reactor.

Edited October 13, 2019 by tater

[jinnantonix]

1 hour ago, Ultimate Steve said:

Plus, the moon landing deniers would have a field day if it landed in absolute darkness due to how easy it would be to fake. Not that that's a planning concern, but it is a side effect.

I am thinking that is the least of problems.  I also think the LED and camera technology has improved enough to overcome the issue.

[tater]

They could fly propulsive lander drones into the crater for sample return to the crew lander. Way safer than landing people down there.

3 hours ago, jinnantonix said:

LOP-G in NRHO is to ensure access to the south pole. 

Gateway in in NRHO because that is where Orion can go, not to ensure access to South Pole (though that is nice).

A frozen LLO (polar) would be better (there are 4, I'm thinking the 86° one) for polar surface access. Orion can't do that, however.

[jinnantonix]

Scott Manley's take on the Artemis moon lander.  Even his 3 stage lander is huge. 

I like the idea that the transit stage is merely a fuel tank that attaches to the top of the ascent vehicle allowing refuelling in LLO before the Ascent stage returns to the LOP-G.  Thrusters could be used to de-orbit the third stage for disposal.

This is leading me to believe the most efficient design will be a small, lightweight, 2-man ascent stage, utilising  2 x 2 AJ10-190 engines and 16x hypergolic thrusters on each stage.

 

Edited October 15, 2019 by jinnantonix

[Guest]

Just to add onto some of the above comments. It’s also a shaky justification indeed when they talk about one of Gateway’s roles being a comm relay to the far side of the Moon, when it couldn’t really serve that function well compared to a few Starlink type sats that can probably provide better coverage for a tiny fraction of the cost. 

[sevenperforce]

3 hours ago, jinnantonix said:

Scott Manley's take on the Artemis moon lander.  Even his 3 stage lander is huge. 

I like the idea that the transit stage is merely a fuel tank that attaches to the top of the ascent vehicle allowing refuelling in LLO before the Ascent stage returns to the LOP-G.  Thrusters could be used to de-orbit the third stage for disposal.

This is leading me to believe the most efficient design will be a small, lightweight, 2-man ascent stage, utilising  2 x 2 AJ10-190 engines and 16x hypergolic thrusters on each stage.

Scott also makes the mistake of thinking the transfer vehicle is intended to stay in LLO as a tug following the mission.

Replacing the "transit stage" with a fuel tank is a great idea; it just requires mature, large-scale propellant transfer tech, which is something we simply don't have developed well enough yet. If you have full propellant transfer then you have access to a lot of different architectures. 

[sevenperforce]

2 hours ago, sevenperforce said:

Scott also makes the mistake of thinking the transfer vehicle is intended to stay in LLO as a tug following the mission.

To be fair, it is confusing. The older mission specs have the transfer vehicle returning independently to LOP-G to be refueled by a logistics launch, while the newer mission specs have it smash itself into the moon. But it certainly will not stay in LLO. As he points out in the video, it would need to do a hella plane change, which it won't have the dV for.

Reusing the tug just doesn't make sense to me. Why send a refueling mission with tanks and an engine when you could just send a new tug?

[tater]

3 minutes ago, sevenperforce said:

Reusing the tug just doesn't make sense to me. Why send a refueling mission with tanks and an engine when you could just send a new tug?

This is the problem with refilling (I actually prefer the SpaceX usage here, because fuel+oxidizer) around the Moon, period.

 

[sevenperforce]

18 minutes ago, tater said:

This is the problem with refilling (I actually prefer the SpaceX usage here, because fuel+oxidizer) around the Moon, period.

Ditto on refuel/refill. I suppose I could say "repropellantize" if I wanted to be annoying.

Most of what you need for repeated lunar mission activity is engines and propellant. So shipping new engines and propellant just to refill existing engines and propellant is a waste.

Reusing the transfer vehicle makes no sense whatsoever. Reusing an ascent vehicle doesn't make much sense because you can have a reusable cabin and simply mate a new booster module to it each time. The only way it makes sense is if you are reusing a dedicated lander and want to avoid shipping new ground structure/landing legs. But there are no plans to reuse the lander, and you wouldn't want to anyway because it represents the highest amount of unnecessary dry mass and the highest risk factor for damage (due to debris impingement, etc.) and it's where you want to attach new ground support supplies anyway.

Debris impingement is the one flaw I foresee with my transfer-ascender-cabin plan.

Edited October 15, 2019 by sevenperforce

[tater]

46 minutes ago, sevenperforce said:

Most of what you need for repeated lunar mission activity is engines and propellant. So shipping new engines and propellant just to refill existing engines and propellant is a waste.

Yeah, it really is tricky as what you are refilling looks exactly like what you need to bring the props (because the tanker must function as a complete spacecraft).

Refilling a 100% reusable (returned to the point where the props are) vehicle makes a lot of sense, however. So Starship makes sense (or anything similar), and refilling in LLO (frozen orbit, presumably) makes sense as long as the props are coming from lunar ISRU.

The only reason for refilling operations WRT Artemis is because there are not LVs capable of lifting what is needed by themselves, but as you say, the LVs that can throw refilling props to the Moon are the same LVs that threw the lander parts in the first place, and can just send a new set of parts (Ascent, Descent, transfer stage).

Stage disposal is also an issue.

Edited October 15, 2019 by tater