totm dec 2023 Artemis Discussion Thread

[AckSed]

Axiom's lunar EVA suits being put through their paces: https://www.nasa.gov/image-article/axiom-space-tests-lunar-spacesuit-at-nasas-johnson-space-center/

[DAL59]

There's been a lot of discussion on this thread of shrinking Orion and/or adding a small lunar lander to SLS, but isn't there another option to get around the "too weak to go to LLO and back" problem? 

Why not have Falcon Heavy or an equivalent launch vehicle launch a kicker stage into LEO, Orion docks with it, gets boosted into a moon transfer, then uses its own fuel to capture into LLO and return.  This would enable smaller lunar landers to be used for Artemis.

[StrandedonEarth]

1 hour ago, DAL59 said:

There's been a lot of discussion on this thread of shrinking Orion and/or adding a small lunar lander to SLS, but isn't there another option to get around the "too weak to go to LLO and back" problem? 

Why not have Falcon Heavy or an equivalent launch vehicle launch a kicker stage into LEO, Orion docks with it, gets boosted into a moon transfer, then uses its own fuel to capture into LLO and return.  This would enable smaller lunar landers to be used for Artemis.

Because at that point SLS is pointless. Three FH launches can put way more payload mass on orbit than a single SLS launch (two would do more, but most of the mass would be residual props), and for a lot cheaper. But, politics/jobs...

[Ultimate Steve]

1 hour ago, DAL59 said:

There's been a lot of discussion on this thread of shrinking Orion and/or adding a small lunar lander to SLS, but isn't there another option to get around the "too weak to go to LLO and back" problem? 

Why not have Falcon Heavy or an equivalent launch vehicle launch a kicker stage into LEO, Orion docks with it, gets boosted into a moon transfer, then uses its own fuel to capture into LLO and return.  This would enable smaller lunar landers to be used for Artemis.

I might be misunderstanding, but doesn't ICPS already do what this tug would do?

[RCgothic]

I think the idea is that ICPS is only 32 tons and FH has at least 63t of nominal payload, so looking at just those numbers would end up with a stage that's twice as powerful.

Unfortunately the largest monolithic payload a Falcon mission has ever carried is 17.5t, with the rest being propellant residuals in the FUS. With a modified adaptor it might be possible to put up ICPS itself with Orion going up separately, but even ICPS doesn't actually have enough DV to send Orion to TLI from LEO (on SLS the core stage helps, but for a simple rendezvous in LEO there'd be no help).

Only SpaceX knows whether they could actually fly a full 63.5t on FH as a monolithic payload.

Another problem is that Orion/ESM can't capture into LLO and return by itself. The "kick stage" would also have to do LLO insertion.

One option is to put up a full falcon upper stage with 63.5t of residual propellant and dock that to Orion in LEO. That would have enough power to send Orion to TLI, but not to also do the full insertion to LLO as would be needed even if the stage were to demonstrate a 3+ day endurance.

EUS has way more DV than needed to do TLI and LLO insertion with just Orion (if it has the endurance), but it weighs about 140t at launch (although it has to do a partial burn to reach LEO with SLS) which takes us back to needing SLS (or starship).

Edited March 1 by RCgothic

[Exoscientist]

On 1/20/2024 at 9:10 AM, Exoscientist said:

 Congress becoming concerned with the frequent delays of the Artemis program, that China may beat us back to the Moon:

US must beat China back to the moon, Congress tells NASA.
By Mike Wall published 3 days ago
'It's no secret that China has a goal to surpass the United States by 2045 as global leaders in space. We can't allow this to happen.'
https://www.space.com/us-win-moon-race-china-congress-artemis-hearing

  

 

China will launch giant, reusable rockets next year to prep for human missions to the moon.
News
By Jennifer Nalewicki( livescience.com ) published 2 days ago
China's new jumbo-size, reusable rockets are part of the country's plans to send humans to the moon by 2030.
https://www.space.com/china-reusable-rockets-human-moon-missions

 This rocket the Long March 10 can get 70 tons to LEO, or 27 tons to TLI. The article only mentions this rocket doing a circumlunar flight but it might actually be able to launch a manned lander mission

 Robert Zubrin with his Moon Direct plan noted a manned lunar mission could be launched by the Falcon Heavy:

Op-ed | Moon Direct: How to build a moonbase in four years
Robert ZubrinMarch 30, 2018
https://spacenews.com/op-ed-moon-direct-how-to-build-a-moonbase-in-four-years/

 Key for his plan is using a “lunar exclusion vehicle” (LEV) of ca. 12 ton gross mass that is hydrolox powered as a lunar ascent vehicle. This would require near zero-boiloff tech, but Zubrin thinks this is doable with current tech.

  Zubrin would also use a larger hydrolox stage for the lander descent stage at ca. 40 ton size, a bit smaller than Centaur V, that could deliver either the 12 ton manned LEV that could return to Earth orbit, or 12 tons of cargo one-way to the lunar surface.

 Quite notable about his plan is the manned flights it would require a single Falcon Heavy stage as the launcher to get the hydrolox in-space stages to LEO. The FH has a payload capacity of 63 tons to LEO. So an only 63 ton launcher could get the required in-space stages to LEO, which could then do a manned round trip flight to the lunar surface. This small size for the launcher is coming from the fact the in-space stages are so much lighter being powered by hydrolox.

 The Falcon Heavy is not man-rated so you would need an extra man-rated launcher like the Falcon 9 to get the astronauts to LEO. But the Long March 10 would be man-rated so could carry the astronauts to orbit. So it could do a manned landing mission in a single launch if hydrolox lander stages like in the Zubrin plan were included.

  Bob Clark

[SunlitZelkova]

3 hours ago, Exoscientist said:

China will launch giant, reusable rockets next year to prep for human missions to the moon.

Not exactly. The only thing launching next year is the LEO version of the Long March 10, which is a single stick/core.

We don’t even know when recovery will begin, construction has not begun on a recovery ship. We would know if this was happening probably, believe me, there are A LOT of people watching what happens at Chinese shipyards.

I do not believe a Falcon 9 Heavy based plan will allow any cheaper or regular access to the Moon than a Starship one. Now, that’s not to say it could be improved.

Instead of trying to rework the lander (which hopefully IFT-3 will prove is coming along just fine tomorrow), the crew launch vehicle needs to be reworked. To do this all we need to do is throw out SLS. Have crew launch to LEO on F9 and Crew Dragon, dock with Starship and then go to the Moon.

This removes the dangerous flight in a tiny capsule, something Apollo dealt with by having a separate lunar module (lifeboat). It also uses an existing vehicle, not requiring any new dev which could take years. Even with SLS the chances are still pretty high we’ll be on the Moon at least a couple years before China. But if we try to build a new lander vehicle? Kiss that goodbye.

Not that there’s anything wrong with that, and China doesn’t seem to care whether they beat us or not, but apparently a lot of Artemis supporters do. I for one couldn’t care less.

[darthgently]

Um.  Ok.  So Musk's push to Mars isn't crazy after all?  Such confusing times

Wasn't sure where to put this, so here I put it

Edited March 19 by darthgently

[Cuky]

Great, more competition = more pushing for developing needed technologies = faster progress.

But on the other side, Boeing can't reliably get astronauts into LEO, yet they think of being first to Mars

[tater]

Musk's reply to that tweet was "Do it"

[SunlitZelkova]

I feel like that was just a ploy for media attention.

”Beating Elon to Mars” is so vague it could mean anything.

*FH launches probe to Mars* “Um, actually we meant humans.”

*Starship launches humans to Mars* “Um, actually we meant building a base or colony.”

*SpaceX builds small outpost on Mars* “Um, actually we were talking about how we already beat them to Mars by holding shares in ULA which launched Perseverance before Starship even flew lolololo.”

[tater]

1 hour ago, SunlitZelkova said:

I feel like that was just a ploy for media attention.

”Beating Elon to Mars” is so vague it could mean anything.

Musk had been giving the talks with BFR updates in September, so this was following that update, video of subscale Raptor testing, large tank testing, etc. All this before Commercial Crew when it was largely assumed Boeing would fly first.

 

 

Edited March 19 by tater

[sevenperforce]

On 2/29/2024 at 8:33 PM, DAL59 said:

There's been a lot of discussion on this thread of shrinking Orion and/or adding a small lunar lander to SLS, but isn't there another option to get around the "too weak to go to LLO and back" problem? 

Why not have Falcon Heavy or an equivalent launch vehicle launch a kicker stage into LEO, Orion docks with it, gets boosted into a moon transfer, then uses its own fuel to capture into LLO and return.  This would enable smaller lunar landers to be used for Artemis.

Orion can't use its own props to capture into LLO and return. It doesn't have enough. Getting into NRHO and back is already tough for it.

Remember that Orion was designed around the Constellation mission architecture. In Constellation, Orion would have docked to the lander launch stack in LEO for the TLI burn, and then the LLO capture burn would have been performed by the hydrolox engine on the Altair lander. So Orion only needed enough props to get back from LLO.

[sevenperforce]

Just a funny for today:

There are so many different possible mission configurations. I think I attempted to make a comprehensive list once, probably upthread in this same thread.

• Double Direct Ascent. One rocket flies from the surface of Earth to LEO to lunar orbit to the surface of the moon, then back to lunar orbit and thence to the surface of Earth. Nova C-8 and Tintin designs.
• Earth Orbit Rendezvous with Lunar Direct Ascent. Multiple rockets fly from the surface of Earth to LEO, assemble into one big rocket in LEO, fly to lunar orbit and to the surface of the moon, then back to lunar orbit and thence to the surface of Earth. This was the "C-1s or Bust" design and is also similar to some Lunar Starship concepts (though not HLS).
• Single-Launch Lunar Orbit Rendezvous. One rocket flies from the surface of Earth to LEO to lunar orbit, then part of it stays in lunar orbit while another part completes the lunar landing and ascent back to lunar orbit and rendezvous, then the first part comes back to the surface of Earth. Apollo design.
• Synchronous Double Orbital Rendezvous. Multiple rockets fly from the surface of Earth to LEO, assemble into one big rocket in LEO, fly to lunar orbit, then part of it stays in lunar orbit while another part completes the lunar landing and ascent back to lunar orbit and rendezvous, then the first part comes back to the surface of Earth. Constellation design.
• Asynchronous Lunar Orbit Rendezvous. Multiple rockets fly from the surface of Earth to LEO to lunar orbit, then assemble into one big rocket in lunar orbit, then part of it stays in lunar orbit while another part completes the lunar landing and ascent back to lunar orbit and rendezvous, then the first part comes back to the surface of Earth. Artemis design with Blue Origin HLS.
• Asynchronous Double Orbital Rendezvous. Multiple rockets fly from the surface of Earth to LEO which may or may not assemble into big rockets in LEO, fly independently to lunar orbit, then assemble together in lunar orbit, then part of it stays in lunar orbit while another part completes the lunar landing and ascent back to lunar orbit and rendezvous, then the first part comes back to the surface of Earth. Artemis design with Starship HLS.
• Asynchronous Lunar Direct Ascent. Multiple rockets fly from the surface of Earth to LEO to lunar orbit, then assemble into one big rocket in lunar orbit, then lands on the surface of the moon, then comes back to lunar orbit and thence to the surface of Earth. Nobody has seriously proposed this but it is kinda like some Lunar Starship concepts with cislunar refueling.

Did I miss anything?

I will note that the graphic is incorrect in one regard: the Earth Orbit Rendezvous would have required multiple Saturn 1Bs per landing, not multiple Saturn Vs:

The "C-1" was the Saturn 1B.

[StrandedonEarth]

2 hours ago, sevenperforce said:

Tintin designs.

Needs an extra +1 for referencing Professor Calculus’ nuclear hybrid rocket. Hopefully Starship-HLS can land the tank-style rover!

[DAL59]

I know this would be impractical, but could you do a Direct Ascent profile with a fully expended V3 Starship, a third stage with landing legs as its payload, with an Orion capsule on top?

On a more practical note, why are they waiting to Artemis V or later before bringing a pressurized rover? Starship has more than enough capacity and they've been testing this thing for over a decade.

Actually, its far worse than that! They're not even bringing an UNpressurized rover until Artemis V in 2029, with the pressurized rover scheduled for after that!? Even though we had a successful moon rover 55 years ago, NASA decided to have their astronauts walk around everywhere severely limiting their EVA time for the first two missions?  Isn't an unpressurized rover a minor expense compared to the cost of SLS and 10 Starships?  Isn't this limitation enough to counteract being able to stay for 7 days instead of 5, finally turning Artemis into a strictly worse Apollo? 

 

The one upside over Apollo I see repeated is that unlike Apollo the Artemis architecture is a sustainable program. But how? Neither the lunar Starship and Orion are reusable, and any plans for a surface base or ISRU are nebulous and in the far future. Its Apollo for the same cost, but with 1/4 the mission cadence,  10x the amount of launches required, and no rover.

Edited March 21 by DAL59

[SunlitZelkova]

29 minutes ago, DAL59 said:

Starship has more than enough capacity and they've been testing this thing for over a decade.

That thing was cancelled. Japan will be developing a new pressurized rover with Toyota.

[Ultimate Steve]

Speaking of, what's the plan if the rover dies? And how did Apollo manage this? For contingency you would have to remain within walking distance on one tank of oxygen (or whatever else the limiting factor is on those suits) anyway. Seems like you would want two self driving rovers or a simple backup apollo style rover strapped to the main rover.

[DAL59]

50 minutes ago, Ultimate Steve said:

Speaking of, what's the plan if the rover dies? And how did Apollo manage this? For contingency you would have to remain within walking distance on one tank of oxygen (or whatever else the limiting factor is on those suits) anyway. Seems like you would want two self driving rovers or a simple backup apollo style rover strapped to the main rover.

You have to remain within walking distance, but it still lets you have more useful EVA time as it reduces the outbound time.

Edited March 21 by DAL59

[tater]

Reusable in space is still reusable.

[magnemoe]

9 hours ago, DAL59 said:

You have to remain within walking distance, but it still lets you have more useful EVA time as it reduces the outbound time.

Yes, they had to stay within walking distance but it let you explore inside this circle around the lander, walking back is also one way. 

[sevenperforce]

11 hours ago, DAL59 said:

I know this would be impractical, but could you do a Direct Ascent profile with a fully expended V3 Starship, a third stage with landing legs as its payload, with an Orion capsule on top?

Over on the SpaceX thread, @tater estimated that a fully-expended V3 Starship could throw 145 tonnes to TLI. We already know that Orion can make it back from LLO on its own (that's how Constellation was designed). So we need a third stage to get us from TLI to the surface of the moon and back up to LLO.

Going from TLI to LLO costs 900 m/s; going from LLO to the lunar surface costs 1,870 m/s each way. So you need 4,640 m/s on that third stage. Orion has a loaded mass of 26.5 tonnes and a single vacuum Raptor comes in at around 1.8 tonnes. Let's round up to 2 tonnes to account for the gimbal system and so forth. At a notional 375 s of specific impulse,  you'll need at least 72.5 tonnes of methalox to achieve 4.64 km/s, not counting tanks and so forth. That brings the total TLI throw to 101 tonnes, not counting tank weight and landing leg weight and egress system weight and other payloads, or the added props to get all of that along for the ride.

Absolutely doable. 

[SunlitZelkova]

14 hours ago, Ultimate Steve said:

Speaking of, what's the plan if the rover dies? And how did Apollo manage this? For contingency you would have to remain within walking distance on one tank of oxygen (or whatever else the limiting factor is on those suits) anyway. Seems like you would want two self driving rovers or a simple backup apollo style rover strapped to the main rover.

13 hours ago, DAL59 said:

You have to remain within walking distance, but it still lets you have more useful EVA time as it reduces the outbound time.

Not necessarily. Back in the 80s planners were considering 400 mile expeditions using pressurized rovers.

I think they will treat the rover as a spacecraft- just like in space, if your spacecraft fails you’re done, if the rover fails you’re done. But you don’t do pseudo-suborbital flights just for safety reasons instead of going to full orbit, and you don’t limit a rover’s travel range because of safety reasons either.

The only reason Apollo had to remain with walking distance with their rover was because it wasn’t pressurized. Thus the endurance of the suit was the main limiting factor.

The whole point of a pressurized rover is to basically have a spacecraft or base on wheels, so you can go as far as you want.

Maybe in the early missions they would stay within walking distance for tests, but eventually they would expand to multi-day 100+ mile expeditions.

[magnemoe]

26 minutes ago, SunlitZelkova said:

Not necessarily. Back in the 80s planners were considering 400 mile expeditions using pressurized rovers.

I think they will treat the rover as a spacecraft- just like in space, if your spacecraft fails you’re done, if the rover fails you’re done. But you don’t do pseudo-suborbital flights just for safety reasons instead of going to full orbit, and you don’t limit a rover’s travel range because of safety reasons either.

The only reason Apollo had to remain with walking distance with their rover was because it wasn’t pressurized. Thus the endurance of the suit was the main limiting factor.

The whole point of a pressurized rover is to basically have a spacecraft or base on wheels, so you can go as far as you want.

Maybe in the early missions they would stay within walking distance for tests, but eventually they would expand to multi-day 100+ mile expeditions.

We have an bit more experience with electrical cars now, pretty easy to have front and rear drive as two independent systems with an interconnect. Or have 6 wheels and 6 batteries and controls. pressure in compartment is more likely to fail but you have space suits and extra oxygen on rover. 

[Exoscientist]

On 3/21/2024 at 3:12 PM, sevenperforce said:

Over on the SpaceX thread, @tater estimated that a fully-expended V3 Starship could throw 145 tonnes to TLI. We already know that Orion can make it back from LLO on its own (that's how Constellation was designed). So we need a third stage to get us from TLI to the surface of the moon and back up to LLO.

Going from TLI to LLO costs 900 m/s; going from LLO to the lunar surface costs 1,870 m/s each way. So you need 4,640 m/s on that third stage. Orion has a loaded mass of 26.5 tonnes and a single vacuum Raptor comes in at around 1.8 tonnes. Let's round up to 2 tonnes to account for the gimbal system and so forth. At a notional 375 s of specific impulse,  you'll need at least 72.5 tonnes of methalox to achieve 4.64 km/s, not counting tanks and so forth. That brings the total TLI throw to 101 tonnes, not counting tank weight and landing leg weight and egress system weight and other payloads, or the added props to get all of that along for the ride.

Absolutely doable. 

  Thanks for that. I was irritated by the approach SpaceX was taking towards the Starship in that SpaceX was ignoring basic principles in spaceflight. The main point was that for high delta-v missions such as lander missions to the Moon or Mars, these are done most efficiently by adding additional stages. But instead SpaceX wants to keep the SuperHeavy/Starship  as two-stages and instead do multiple refuelings. Another irritation was that SpaceX was ignoring the basic principle that you want to minimize upper stage dry mass as much as you can. This is because every extra kilo added to the upper stage dry mass subtracts directly from your payload. However, in making the Starship reusable, a whopping 80 tons, and with that much being subtracted from LEO payload, was added to the Starship being made reusable, going from a possible 40 ton expendable dry mass to a 120 ton reusable dry mass.

 Why is this approach taken? Because SpaceX has this fixation that the Starship must be the be-all-end-all for ALL of spaceflight. Then to get the cost per kilo they want, they need the Starship to be reusable. Then any extra mass added to dry mass is acceptable, no matter how much it is.

 But a simple cost analysis shows this is a fallacious approach. A SpaceX exec estimated “10ish” refueling missions for the Artemis lander missions using the Starship HLS. But Elon estimated an aspirational $10 million launch cost for a reusable SH/SS. But this would be $100 million for 10 reusable launches. But a single expendable launch would only be $90 million by which because of the higher payload SH/SS could do single launch missions both to the Moon and Mars. No refueling missions required, and not even the SLS being required. 

 Another interesting calculation is to see how much mass SH/SS could get to Mars as an expendable in a single launch. 

  Bob Clark

Edited March 23 by Exoscientist
Added a link to an Elon estimate that an expendable Starship might have a dry mass of only 40 tons.