totm dec 2023 Artemis Discussion Thread

[sevenperforce]

4 minutes ago, tater said:

I just used the actual Apollo numbers I found for the 2 burns, and slopped it up.

Apollo 11 LOI burn was 889.2 m/s. They circularized with another 46.7 m/s.

TEI for Apollo 11 was around 1000 m/s.

But yeah, Orion is too heavy, and the SM is too small (Apollo's SM had to also be much larger because it was doing LOI for the CSM/LM stack, not just the CSM).

Odd. The typically-reliable figures on wiki give 1.31 km/s for both LOI and TEI. 

**digging**

Looks like NASA's GR&As for cislunar ops assume going to LLO will involve a burn into HLO first, for an HLO LOI of 508 m/s and another 520 m/s to get down to a 100x100km orbit. So that's where the ~1.3 km/s figure comes from. 

[RCgothic]

Where's this 100kN Starship RCS figure come from? Because the Apollo SPS was only 70kN and they aren't using engines remotely that big for thrusters.

The Artemis ESM was built to specification. Being underpowered is a problem with the specification, not the manufacturer. It would have sucked just as much built to the same spec in the US. Let's not be unduly unfair to ESA.

[sevenperforce]

23 minutes ago, RCgothic said:

Where's this 100kN Starship RCS figure come from? Because the Apollo SPS was only 70kN and they aren't using engines remotely that big for thrusters.

The Artemis ESM was built to specification. Being underpowered is a problem with the specification, not the manufacturer. It would have sucked just as much built to the same spec in the US. Let's not be unduly unfair to ESA.

Elon says has said the methane-gox hot-gas thrusters for Starship will be ten-tonne-class.

[Wjolcz]

How do you even make a non-hypergolic hot gas RCS thrusters? Are those Raptor igniters even able to operate quickly and reliably enough to be used for RCS on the Starship?

Edit: I know hydrogen peroxide can be used but I remember Elon saying something about mini-Raptors used for RCS.

Edited October 8, 2019 by Wjolcz

[sevenperforce]

49 minutes ago, Wjolcz said:

How do you even make a non-hypergolic hot gas RCS thrusters? Are those Raptor igniters even able to operate quickly and reliably enough to be used for RCS on the Starship?

Edit: I know hydrogen peroxide can be used but I remember Elon saying something about mini-Raptors used for RCS.

Gas-gas spark ignition is very reliable. Same principle as a gas stove.

[kerbiloid]

11 hours ago, Wjolcz said:

How do you even make a non-hypergolic hot gas RCS thrusters?

Buran did it.
(In Russian) http://www.buran.ru/htm/odu.htm

A gas generator produces gaseous oxygen from liquid oxygen by burning a little amount of kerosene to heat.
The RCS thrusters have electric ignition, gaseous oxygen cooling, gaseous oxygen oxidizer, and excess of oxygen in propellant ratio to avoid sooting.

[jinnantonix]

Having completed a simulation of the Artemis program I have a qualitative impression of the capability of Orion for the requirements of the program.  The capsule itself is relatively heavy, but that is to be expected because the craft is big and roomy (compared to Apollo) and it needs to be robust enough for re-usability, and have features that support a crew of 4-6 for periods of 21 days (or more).  The outcome of a heavy capsule, is that the SM has a lot of mass to push around, and that is going to limit Orions range. 

The SM also has some constraints:  Firstly it has a lot of redundancy  to satisfy human rating requirements, it needs facilities to provide for safely carrying resources for a long mission, and it needs to be cost effective (since it is fully expendable).  To meet these constraints, it is not surprising the SM does not have a huge delta-V capability, it is enough to get to NRHO or lunar DRO and return, that is what it is designed for and it does that well, and with a reasonable design factor built in.  Get humans to high lunar orbit, and bring them back safely.  Tick.

It has always been assumed that a large part of the heavy lifting would be done on non-human rated, commercial carriers.  Hence the idea that there be a staging post in HLO where crew would transfer from Orion to very carefully built and fully tested facilities for lunar landing (2 crew) and return to HLO.  The challenge being presented now to contractors  is substantial - to build a human rated craft capable of 2 weeks on the lunar surface, to travel from HLO to surface and return, and to be powered and heated at least partially by RTG (yes, this will be a requirement).  This is a much bigger design problem than faced by Grumman Aircraft in building Apollo's LEM.  NASA's SLS will work (it's just a variant of the Space Shuttle technology), and commercial carriers like SpaceX with Falcon 9 and Falcon Heavy, and ULM Vulcan can lift the cargo reliably and cost effectively.  In my opinion the whole plan for a 2024 landing rests on successfully proving the design of a human rated lunar lander that can reach HLO unmanned, and then complete a manned landing and return to HLO.  If it is re-usable in any way will be a bonus.  If it is cost effective enough to meet the requirements of the Artemis program, I will be amazed.

[tater]

6 hours ago, jinnantonix said:

Having completed a simulation of the Artemis program I have a qualitative impression of the capability of Orion for the requirements of the program.  The capsule itself is relatively heavy, but that is to be expected because the craft is big and roomy (compared to Apollo) and it needs to be robust enough for re-usability, and have features that support a crew of 4-6 for periods of 21 days (or more).  The outcome of a heavy capsule, is that the SM has a lot of mass to push around, and that is going to limit Orions range. 

It's not really being reused in that way. I think the goal is only for the internal pressure vessel to be reused. The difference in cost between a new Orion, $900,000,000, and a later, partially reused Orion $633,000,000 is "only" $267,000,000, so the reuse only saves 30%. If the cost could be reduced by more than 30% then, and dump resuse, we'd be better off.

 

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The SM also has some constraints:  Firstly it has a lot of redundancy  to satisfy human rating requirements, it needs facilities to provide for safely carrying resources for a long mission, and it needs to be cost effective (since it is fully expendable).  To meet these constraints, it is not surprising the SM does not have a huge delta-V capability, it is enough to get to NRHO or lunar DRO and return, that is what it is designed for and it does that well, and with a reasonable design factor built in.  Get humans to high lunar orbit, and bring them back safely.  Tick.

It was not designed for NRHO/DRO. They picked those orbits because that was what it can do.

This is the fundamental problem with the entire SLS/Orion program, it was not designed with any mission in mind at all, they are retrofitting missions for it based on what is possible.

 

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It has always been assumed that a large part of the heavy lifting would be done on non-human rated, commercial carriers.  Hence the idea that there be a staging post in HLO where crew would transfer from Orion to very carefully built and fully tested facilities for lunar landing (2 crew) and return to HLO. 

This is simply untrue. There were no heavy lift commercial carriers, and no SLS/Orion mission was ever conceived early in the program involving commercial launches. This was also bolted on later---to cover for the fact that SLS was never designed with any mission in mind at all, and is unlikely to have the launch cadence required to achieve anything using distributed SLS launches alone.

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The challenge being presented now to contractors  is substantial - to build a human rated craft capable of 2 weeks on the lunar surface, to travel from HLO to surface and return, and to be powered and heated at least partially by RTG (yes, this will be a requirement).

Do you have a link for this? The BO lander has no RTG, for example.

(EDIT: I looked here, and found no such requirement: https://www.fbo.gov/index?s=opportunity&mode=form&tab=core&id=d5460a204ab23cc0035c088dcc580d17)

 

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NASA's SLS will work (it's just a variant of the Space Shuttle technology),

No, actually it's not. It was meant to be, that was the initial sales pitch. The core stage is no longer a Shuttle tank at all. The SSMEs have been altered, and therefore had to be retested/refurbished at a cost that is a multiple of what each engine cost new---reusing each of the SSMEs is costing us 127 million dollars. They were ~40M$ new. The upper stage? Not Shuttle tech. The worst part of Shuttle, the SRBs? Yeah, they keep those.

 

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and commercial carriers like SpaceX with Falcon 9 and Falcon Heavy, and ULM Vulcan can lift the cargo reliably and cost effectively.  In my opinion the whole plan for a 2024 landing rests on successfully proving the design of a human rated lunar lander that can reach HLO unmanned, and then complete a manned landing and return to HLO.  If it is re-usable in any way will be a bonus.  If it is cost effective enough to meet the requirements of the Artemis program, I will be amazed.

This I agree with. I think they need to test it, uncrewed, first as well. All up, to the lunar surface and back.

Edited October 9, 2019 by tater

[Barzon]

5 hours ago, tater said:

the fact that SLS was never designed with any mission in mind at all

yes, and that is truly a shame. but the fact that a feasible, relatively sustainable return to the Moon is possible at all is a miracle.

[sevenperforce]

I want to see a man-rated lander "truck" with dual engines and a central cylindrical tank that can be vented and used as a wet workshop/airlock. Could be used to deliver either crew or cargo.

[kerbiloid]

11 hours ago, sevenperforce said:

I want to see a man-rated lander "truck" with dual engines and a central cylindrical tank that can be vented and used as a wet workshop/airlock. Could be used to deliver either crew or cargo.

Spoiler

 

[jinnantonix]

 

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This is the fundamental problem with the entire SLS/Orion program, it was not designed with any mission in mind at all, they are retrofitting missions for it based on what is possible.

You make that sound like a bad thing.  Had you considered that the more the SLS/Orion and LOP-G is suited to a specific mission, the less suitable it is for others.  My understanding is that NRHO was chosen because the location could be a staging post for non-lunar missions, such as deep space probes to asteroids or repairing space probes located in heliocentric orbit, or Mars.  Why would you want to burn all the way to LLO if not going to the moon?  If there really is an ability to manufacture fuel on the moon, surely it is more cost effective to position the refuelling station in HLO or at a Lagrange point.

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Do you have a link for this? The BO lander has no RTG, for example.

I have no link, I believe an RTG is required because in my simulation it is not possible to land in Shackleton Crater and do anything there without RTG.  In fact by my reckoning the entire mission to the lunar south pole can and should be done with RTG only and no solar panels.

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There were no heavy lift commercial carriers, and no SLS/Orion mission was ever conceived early in the program involving commercial launches.

I am talking about the Artemis Program, the subject of this thread.

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NASA's SLS will work (it's just a variant of the Space Shuttle technology),

No, actually it's not. 

Yes, actually it is.  Look up the meaning of the word "variant". 

And what have you got against the SRBs?  Seems to me to be a simple and cost effective solution to a difficult problem.  Sure there are alternatives, but how long would NASA need to prove the technology, and how much would it cost?

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I think they need to test it, uncrewed, first as well. All up, to the lunar surface and back.

I suspect this is why the option of an in-transit rendezvous at LOP-G ( and maybe also a RTG) is excluded from the initial spec for the lunar lander.  They may wish to just get an uncrewed test craft to the surface at an equatorial location, in order to test more challenging aspects of the craft and mission, e.g. docking with the transit vehicle, multiple firing of the ascent and transit vehicle engines, and docking the ascent craft at LOP-G.

I maintain however that the successful completion of the Artemis program, which specifies landing at the lunar south pole, will require the lunar lander to meet the Orion at LOP-G for crew transfer, and it will require a RTG.

 

[sevenperforce]

What's a notional wet mass for an ascent stage (reusable or otherwise) that goes from the lunar surface to the Gateway?

EDIT: It's also annoying that we literally have zero steps toward a manned capsule for lunar surface ops.

Edited October 10, 2019 by sevenperforce
add

[jinnantonix]

@sevenperforce the model of the Ascent Vehicle in my simulation had a wet mass of 3.64t, excluding payload and LS resources.  It is capable of launching from the surface to the LOP-G.  It uses a pair of AJ10-190 hypergolic fuelled engines.
 

Spoiler

 

 

[sevenperforce]

2 minutes ago, jinnantonix said:

@sevenperforce the model of the Ascent Vehicle in my simulation had a wet mass of 3.64t, excluding payload and LS resources.  It is capable of launching from the surface to the LOP-G.  It uses a pair of AJ10-190 hypergolic fuelled engines.

That's gotta be bare-bones. The Apollo ascent module was 4.7 tonnes wet and had less dV.

The LockMart lunar lander concept uses an Orion pressure vessel but I wonder whether that's ideal. Certainly simplifies some things. The real issue is that you just don't know exactly what the purpose of lunar exploration is, which tends to complicate discussion of what your lander should look like.

[jinnantonix]

From what I can tell, the intention is for the crew to survey the lunar surface for minerals, water and organic compounds suitable for manufacturing fuel, and to test the surface to allow the design of an ISRU facility.  They would need to take a lot of instruments for in situ collection of data, of course the instruments will all be left behind.   

Regarding the Lockheed Martin design, I think the Orion pressure vessel is unnecessarily large.  Lunar missions really only need two crew, and basic facilities for a two week stay.  On the other hand, the pressure vessel I am using in my model is tiny, only 1.8m diameter and 2.3 m in length, weighing 1.1t. , not a realistic size for two crew, it would need to be at least double the volume and mass.

[tater]

4 hours ago, jinnantonix said:

You make that sound like a bad thing.  Had you considered that the more the SLS/Orion and LOP-G is suited to a specific mission, the less suitable it is for others.  My understanding is that NRHO was chosen because the location could be a staging post for non-lunar missions, such as deep space probes to asteroids or repairing space probes located in heliocentric orbit, or Mars.  Why would you want to burn all the way to LLO if not going to the moon?  If there really is an ability to manufacture fuel on the moon, surely it is more cost effective to position the refuelling station in HLO or at a Lagrange point.

Because SLS/Orion has cost a vast sum of money, and we have no idea what ISRU will take. The notion that NRHO is useful for Mars, etc, presupposes that SLS can be used for this mission as well, and it plainly cannot. There is no alternate future where SLS is launching at a rate where a Mars mission is possible with SLS. It would take years to build each Mars craft, and most of that mass would be propellants---cryos props that would boil off waiting for years for the mission to fly.

 

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I have no link, I believe an RTG is required because in my simulation it is not possible to land in Shackleton Crater and do anything there without RTG.  In fact by my reckoning the entire mission to the lunar south pole can and should be done with RTG only and no solar panels.

Then why state it as if it's true? The point in fact of that particular crater is exactly that there are areas in sunlight most all of the time for solar. Probes to the crater probably use RTGs, but human landers won't be.

 

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I am talking about the Artemis Program, the subject of this thread.

You can't have it both ways. Gateway existed before Artemis as an idea (LOP-G). Gateway evolved from ARM, which was similarly make-work for SLS/Orion someplace it could go. Because it needed to go someplace. For reasons. Early assumptions were in fact that everything was brought with Orion. Then they decided to fly block 1 more than once (why even once is a mystery, they should have built only EUS from the start).

You said, "It has always been assumed that a large part of the heavy lifting would be done on non-human rated, commercial carriers.  Hence the idea that there be a staging post in HLO where crew would transfer from Orion to very carefully built and fully tested facilities for lunar landing (2 crew) and return to HLO."

The staging post in HLO was not because that makes sense, it was because it's the only place Orion can go. They have since added commercial to it, since SLS can't get the job done (and even if it could, NASA doesn't have the money to spend literally 10X the cost of commercial on every flight).

 

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Yes, actually it is.  Look up the meaning of the word "variant". 

So the Space Shuttle was a "variant" of the Wright Flyer?

It started out with the goal of reuse of Shuttle tech to save time and money. It has abjectly failed at both of those. The core stage bears no relation to the shuttle tank at all aside from diameter at this point. Not a variant (not using the Shuttle tooling). The engines? Variants, to be sure, but for some reason they cost 3X the new cost of SSMEs as used engines that we already paid for. The upper stage? Nothing Shuttle at all, entirely untested in this role for ICPS, and never tested for EUS.

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And what have you got against the SRBs?  Seems to me to be a simple and cost effective solution to a difficult problem.  Sure there are alternatives, but how long would NASA need to prove the technology, and how much would it cost?

It's complicated, and it is only required because of the stupid sustainer architecture for the core stage (because they can't start the Shuttle engines off the pad).

 

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I suspect this is why the option of an in-transit rendezvous at LOP-G ( and maybe also a RTG) is excluded from the initial spec for the lunar lander.  They may wish to just get an uncrewed test craft to the surface at an equatorial location, in order to test more challenging aspects of the craft and mission, e.g. docking with the transit vehicle, multiple firing of the ascent and transit vehicle engines, and docking the ascent craft at LOP-G.

I maintain however that the successful completion of the Artemis program, which specifies landing at the lunar south pole, will require the lunar lander to meet the Orion at LOP-G for crew transfer, and it will require a RTG.

It's not gonna have an RTG.

The current Artemis timeline has the lander as the all-up first flight of the lander. They keep messing with commercial crew for safety reasons, then they plan to possibly strand people on the Moon because the most complex and dangerous part of Artemis apparently doesn't need testing. Bizarre.

If BO was faster, maybe they'd fly the lander ahead of time.

 

Edited October 10, 2019 by tater

[sevenperforce]

I know the titanium heat shield carrier structure alone masses over 1300 kg on Orion. I cannot find mass estimates for the thermal backshell or the heat shield itself, anywhere. Nor for the parachutes.

If we make the gross estimate that Orion's landing weight of 7337 kg would be cut in half by the removal of the chutes, the thermal backshell, the heat shield, and the heat shield carrier structure, then that gives us roughly 3700 kg. If you attached that to the "stock" Orion service module, it would have 2054 m/s of dV. Unfortunately the OMS engine stuck underneath is not powerful enough to get off the moon. And that leaves you with no budget for airlock, etc.

Edited October 10, 2019 by sevenperforce

[RCgothic]

I struggle to see how an SLS suited to recreate an Apollo style mission would be less suited to any task than the SLS we have.

The ability to comanifest substantial payloads and reach lower lunar orbits is a significant advantage to any job Orion and SLS could perform.

[tater]

2 minutes ago, RCgothic said:

I struggle to see how an SLS suited to recreate an Apollo style mission would be less suited to any task than the SLS we have.

The ability to comanifest substantial payloads and reach lower lunar orbits is a significant advantage to any job Orion and SLS could perform.

Maybe they can add IVF to EUS, and actually fill the tanks. That reduces the comanifested payload, however, though they could possibly do TLI and LOI in LLO in that case. They'd still need to send the lander ahead to LLO though.

[kerbiloid]

1 hour ago, sevenperforce said:

Nor for the parachutes.

Main parachutes are probably 136 kg each.
http://spaceflight101.com/spacecraft/orion/

[tater]

 

[sevenperforce]

1 hour ago, kerbiloid said:

Main parachutes are probably 136 kg each.
http://spaceflight101.com/spacecraft/orion/

There's really a TON of stuff on there that's useless in cislunar space. I wonder how low it could go.

Still doesn't solve the airlock problem.

[tater]

12 minutes ago, sevenperforce said:

There's really a TON of stuff on there that's useless in cislunar space. I wonder how low it could go.

Still doesn't solve the airlock problem.

I'd expect that LockMart would use a stripped down version of that Mars lander they were talking about (for single stage reusable). Haven't seen any real specs on that, though.

[kerbiloid]

17 minutes ago, sevenperforce said:

Still doesn't solve the airlock problem.

Spoiler

To the right from the sphere, a cylinder with hemisphere.

Presumably the same but as a separate chamber, also used as an in-flight wardrobe for the lunar suits. To the left.
(Usually captioned as antenna what is probably wrong.)

Spoiler

So, a d=2m / l = 0.5 m cylinder with two spherical segments.
Can be made jettisonnable.

 

Edited October 10, 2019 by kerbiloid