totm dec 2023 Artemis Discussion Thread

[tater]

 

[sevenperforce]

On 9/15/2021 at 11:26 PM, tater said:

On 9/15/2021 at 11:17 PM, jinnantonix said:

If it doesn't fit a specific need, then NASA won't select it.  But I suspect NASA is seeking a lower cost lander for crew transfer to/from Gateway only.  I see LSS as a direct freight system, and SpaceX has costed it as such.

If lower cost and just a taxi is not part of the requirements, it's the same requirements, except for the "sustainable" part.

Meaning sustainable and 4 crew being mandatory.

The alternative requirement/need might be something like "low-mass space taxi and lifeboat independent of SpaceX". As powerful as the SpaceX system is, it does depend on a large Earth/LEO infrastructure, and so if we are going to have a sustained crew presence on the lunar surface then it would be a good idea to have an independent contingency system in place.

[tater]

11 minutes ago, sevenperforce said:

The alternative requirement/need might be something like "low-mass space taxi and lifeboat independent of SpaceX". As powerful as the SpaceX system is, it does depend on a large Earth/LEO infrastructure, and so if we are going to have a sustained crew presence on the lunar surface then it would be a good idea to have an independent contingency system in place.

I'm all for multiple systems, but it's bizarre to me that they can't come up with something that is less expensive per unit capability.

Indeed, I think a small, reusable sortie lander for crew transfer to the surface makes a lot of sense. I could see as a stand alone system it might be more expensive to get it there, but if it also used methalox, then it could be refilled with SS tankers (or a prop depot), such that 1 load of props delivered with a SS could result in many round trip sorties.

RT from NRHO<—>lunar surface is ~5.5 km/s.

A 35t gross mass lander that is 7.5t dry (vehicle plus crew) can do the RT with some margin. So 27.5t of props per trip. A SS could bring ~400t to NRHO and still head home—that's enough propellant for that small lander to make 14 trips to the surface and back.

[tater]

L: 52 m vs 20m

H: 73m vs 43m

W: 109m vs 19m

(converted from potato units to metric and rounded)

[AtomicTech]

You can really see the similarities in the design!

Saving this for later, for building!

[tater]

 

[RCgothic]

I still don't see the point in EUS.

Block 1 launches Orion and commercial space handle cargo/lander.

Blocks 1B and Block 2 launch Orion and not a lander and commercial space still handle cargo/lander.

SLS is too expensive and too rare to ever launch probes.

EUS is pointless.

 

 

[Beccab]

2 minutes ago, RCgothic said:

I still don't see the point in EUS.

Block 1 launches Orion and commercial space handle cargo/lander.

Blocks 1B and Block 2 launch Orion and not a lander and commercial space still handle cargo/lander.

SLS is too expensive and too rare to ever launch probes.

EUS is pointless.

 

 

I am very, very doubtful of co-manifested SLS missions. How would that even work, send a module up with Orion for something close to 2 billions in 2028 (4 people), then dock, spend at least week in gateway putting it back to work (not continuously inhabited), then at the very best a month and many EVAs installing the module, then send 2 or 3 of the people on a lunar module that can easily handle two dozens and get to the surface after something like a couple months since the launch. How is that an architecture that makes any sense, especially with FH expendable sending up two of the heaviest modules, together, for 1/8th of that?

[tater]

57 minutes ago, RCgothic said:

EUS is pointless.

ICPS requires I think 3 Oberth burns, then Orion separates, and Orion does a 4th burn to put Orion into TLI. (unless it's 2, then a third burn with Orion, I forget).

Regardless, this is needlessly complex, and puts the vehicle through the van Allen belts multiple times. EUS really is the bare minimal upper stage for SLS not to be dangerously stupid, IMO.

Remember, ICPS was never supposed to launch a spacecraft with crew in it for this very reason.

[SpaceFace545]

8 hours ago, Beccab said:

I am very, very doubtful of co-manifested SLS missions. How would that even work, send a module up with Orion for something close to 2 billions in 2028 (4 people), then dock, spend at least week in gateway putting it back to work (not continuously inhabited), then at the very best a month and many EVAs installing the module, then send 2 or 3 of the people on a lunar module that can easily handle two dozens and get to the surface after something like a couple months since the launch. How is that an architecture that makes any sense, especially with FH expendable sending up two of the heaviest modules, together, for 1/8th of that?

It works by filling the extra space. It has room to spare so it’s taking the modules with it. Like how passenger planes also co-manifest cargo. Sure you can always fly cargo in a dedicated freighter but why not use up the extra space on existing flights.

[tater]

There is a space above the EUS and below Orion for comanifesting items to TLI. The trouble is the mass limits. It's enough form a module for Gateway, maybe a docking port, or airlock. That's it.

 

[RCgothic]

You mean the volume?

[tater]

4 hours ago, RCgothic said:

You mean the volume?

I mean Block 1B is mass limited to TLI—10-11t of comanifested cargo is not enough mass to do anything useful.

I never bothered to see if the volume  was a problem—because there wasn't enough throw anyway. If it could take 30t, then it would be worth looking to see if you could fit a 30t lander in there.

[Beccab]

Since we're talking about block 1b, whenever they want to start launching that they need to build another mobile launcher because the block 1 one, which costed 1 billion and took a decade, can only ever fit SLS block 1

[SpaceFace545]

8 hours ago, tater said:

There is a space above the EUS and below Orion for comanifesting items to TLI. The trouble is the mass limits. It's enough form a module for Gateway, maybe a docking port, or airlock. That's it.

 

A small turboprop can’t carry much but they still fit packages on them. Even though the mass limitations are their the ability to take extra cargo is something that should be taken advantage of. Other than that your just wasting fuel.

[tater]

4 minutes ago, SpaceFace545 said:

A small turboprop can’t carry much but they still fit packages on them. Even though the mass limitations are their the ability to take extra cargo is something that should be taken advantage of. Other than that your just wasting fuel.

Block 1 B has 2 purposes.

Most importantly, it allows a single TLI burn. That's the reason it exists—the Block 1 ICPS was never supposed to be used with people because it is so weak and requires multiple burns.

That it can haul some light module is fine, but given the program, any such module likely costs some insane amount of money. As to taking extra cargo... it sort of depends. Adding modules every single trip increases Gateway's size, which might not actually be desirable, more modules, more radiators, more solar, more ECLSS, etc.

[tater]

Note that even if they could comanifest more than 11t to TLI—Orion could not deal with that. The dv of the SM is small enough that with an 11t module, it can take it to NRHO, and still come home, but some amount above 11t, and it lacks the dv to return since while the 450 m/s burn from TLI to NRHO is tiny, it will use more props to do that with cargo.

If they used the extra TLI throw to make a decent SM (using the same engine, they'd likely want 2 though), it looks like Orion could fly to and from LLO directly (just).

[Barzon]

On 9/21/2021 at 4:27 PM, tater said:

 

all the NASA peeps I know are very happy with this news, Plus afaik this was how it was for years until it was changed at some point after CxP got cancelled.

 

also yeaaa I'm back kinda  hope yall been doing ok

Edited September 22, 2021 by Barzon

[tater]

3 minutes ago, Barzon said:

all the NASA peeps I know are very happy with this news, Plus afaik this was how it was for years until it was changed at some point after CxP got cancelled.

 

also yeaaa I'm back kinda  hope yall been doing ok

There was supposed to be a exploration director added (basically what this is), I think it's less about the actual change, and more about the way it looks externally. That may be the point.

Minus the whole BO lawsuit, etc, I think it's less of a thing, but it was not done in the best possible way—if that makes any sense.

 

[Barzon]

 

1 minute ago, tater said:

I think it's less of a thing, but it was not done in the best possible way—if that makes any sense.

 yea that makes sense and I agree

Edited September 22, 2021 by Barzon

[Motokid600]

What is the point of the rectilinear halo orbit that Gateway will be on? Is it to tackle the issue of Lunar mass-cons disturbing orbits? Or is it because Orion needs the extra kick from the oberth effect to return home?

[tater]

18 minutes ago, Motokid600 said:

What is the point of the rectilinear halo orbit that Gateway will be on? Is it to tackle the issue of Lunar mass-cons disturbing orbits? Or is it because Orion needs the extra kick from the oberth effect to return home?

It's that the LOI burn is only 450 m/s.

Orion's target orbit is dictated by the low dv of the SM.

[StrandedonEarth]

Sorry, I can’t resist sharing this here…

 

[cubinator]

1 hour ago, Motokid600 said:

What is the point of the rectilinear halo orbit that Gateway will be on? Is it to tackle the issue of Lunar mass-cons disturbing orbits? Or is it because Orion needs the extra kick from the oberth effect to return home?

It's because that's as far as Orion is capable of going, and it allows for visits to the poles of the Moon.

[tater]