totm dec 2023 Artemis Discussion Thread

[tater]

1 hour ago, Exoscientist said:

 Not exploding is an important requirement for a rocket, especially for one intended to carry crew.

Indeed. Powerpoint presentations never explode, so clearly Powerpoint is the best crew vehicle.

 

 

[RCgothic]

On 1/27/2024 at 7:38 AM, Exoscientist said:

 

Your estimated extra propellant of 6.5 tons required might not be including the required propellant to also get the Orion back to Earth. I estimated 10 tons extra propellant required.

 But anyway, this latest blog  post was to keep the current size service module, still stage from NRHO not low lunar orbit, but use a hydrolox lander to deal with the larger delta-v needed for staging from NRHO. The proposal would still be heavier to TLI than before though. The Orion/service module weighs 26.5 tons. A 15 ton lander would bring the TLI mass to 41.5 tons. I made two suggestions to deal with this added mass to TLI: adding a Centaur V at 50-ton size as a 3rd stage or going back to the J-2X engine  for the Boeing EUS upper stage that had been planned. A preliminary calculation suggest they should be able to do > 42 tons to TLI.

A ca. 2 ton mass lunar crew module should be able to do over a week stay on the Moon based on the Cygnus module. 

 As to why this approach, the Starship HLS is still uncertain for an Artemis III or Artemis IV timeline. 

There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion.

I already think the Apollo LM is far less capable than we need, a 2t Cygnus derived lander ludicrously, even dangerously so. A lander with an ascent stage that light could only be done by cutting margins beyond the bone. Hydrolox is also absolutely not a propellant you consider in the same breath as breath as reliability and endurance.

And as for timelines, regardless of the challenges facing Starship and *Blue Origin* HLS, a clean slate design is starting five years behind Starship and 3 years behind BO. If Starship or BO HLS can't meet Artemis III and IV timelines at this point, then it simply can't be done. The timeline needs to change, not the lander.

Spaceflight timelines are *never* improved by starting from scratch mid programme. *Never*.

I have a lot of sympathy for blowing up the timeline to acquire greater mission scope and craft capability. We should do this to rework the mission architecture to get rid of SLS and Orion. But a skeletal lander proposal does the opposite - it trashes the timeline to make everything worse.

Edited January 28 by RCgothic

[tater]

6 minutes ago, RCgothic said:

There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion.

Yeah, in this thread, the SLS/Orion thread, and the PREVIOUS SLS thread (which OP, who is a total SLS fanboy asked to be closed), it has been stated literally for years here (10 now?) That the absolute min TLI throw was something on the order of 60t for a useful SLS lunar mission that includes Orion. Different people do the math—we all get the similar answers, even with slightly different assumptions (which lends credence to our math I would say).

9 minutes ago, RCgothic said:

I have a lot of sympathy for blowing up the timeline to acquire greater mission scope and craft capability. We should do this to rework the mission architecture to get rid of SLS and Orion. But a skeletal lander proposal does the opposite - it trashes the timeline to make everything worse.

Yeah, a single launch architecture is a dead end.

There is an alternative, which is to pre-place infrastructure on the lunar surface, then use small landers as a taxi system from lunar orbit to the base on the surface. Such landers don't have to be designed for crew comfort for 6-14 day flights, including surface EVAs (dust!), they only need to be comfortable for the round trip to and from NRHO if that is a requirement (LLO, otherwise). If NRHO is a thing, the lander still needs to be able to support the crew for about a week in case of an abort that requires phasing, though. So any minimalist lander that has to use NRHO must have the ability to support the crew for a week. Still, with prepositioned assets, it might be a plausible architecture.

Ie: fuel a SpaceX HLS for a 1-way trip—which is just 1 refill using an expended SS (maybe 2 with boiloff, depending on specific mass to LEO and timing). Land HLS as a habitat. Follow up with a single stack lander that lands nearby, and first EVA is from lander to their HLS home.

[SunlitZelkova]

4 hours ago, Exoscientist said:

 Not exploding is an important requirement for a rocket, especially for one intended to carry crew.

 For the alternative proposal using a hydrolox stage for the propulsion of a lunar  lander, this propulsive stage already exists and been flown multiple times for the upper stage of the Ariane 4 rocket.

 For the Cygnus capsule, it has been flown multiple times as a unmanned cargo craft and is planned to be a manned component of a space station. As I mentioned though I’m not certain it has it’s own independent life support systems. The Cygnus itself weighs 2, 000 kg. I don’t think adding life-support would add too much more to that mass.

  Robert Clark     

But you only know if a rocket is not going to explode if it goes through testing.

Your proposed vehicle is nowhere near close to testing. Starship and HLS are, and thus will "not explode" much faster than your proposed lander.

The creation of any vehicle is a "from the ground up" process. Things change during the detailed design process as issues that weren't realized during the concept phase become known. Variants of your proposed spacecraft might exist, but the actual spacecraft do not.

What you are saying is like saying that SLS was "already here" in 2015 because all it is is RS-25s from the Shuttle, a redesigned external tank, SRBs with an extra segment, and a Centaur upper stage. History has clearly shown that utilizing existing components to create a new rocket "fast" is not fast.

[Codraroll]

5 hours ago, Exoscientist said:

Not exploding is an important requirement for a rocket, especially for one intended to carry crew.

Starship didn't explode in the PowerPoints either.

[Exoscientist]

16 hours ago, RCgothic said:

There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion.

 The fueled Orion/service module weighed about 26.5 tons:

Specifications
Spacecraft type	Crewed
Launch mass	CM: 22,900 lb (10,400 kg) ESM: 34,085 lb (15,461 kg) Combined mass: 58,467 lb (26,520 kg) Total with LAS: 73,735 lb (33,446 kg)
Dry mass	CM: 20,500 lb (9,300 kg) landing weight ESM: 13,635 lb (6,185 kg)

https://en.m.wikipedia.org/wiki/Orion_(spacecraft)

 Then with 10.7 tons extra propellant and tankage and a 15 ton lunar lander the total mass needing to get to TLI is:

26.5 + 10.7 + 15 = 52.2 tons .

 Perhaps the higher 60 ton you’re getting comes from including the Launch Abort System(LAS)? But that is jettisoned well before reaching orbit .

  Robert Clark

 

[sevenperforce]

On 1/27/2024 at 2:38 AM, Exoscientist said:

On 1/26/2024 at 9:30 AM, RCgothic said:

I do agree a larger service module on Orion would be better, given where we've ended up. It would actually improve SLS Block 2's co-manifest payload to NRHO as well, as SLS B2 can throw more combined mass of Orion/ESM and payload to NRHO than Orion can actually brake into that orbit and still return.

SLS might *possibly* be able to do a single stack Apollo style mission with an Apollo LM *if* the ESM is upgraded with an additional 6.5t of propellant and 0.6t dry mass. The total mass to TLI would then be ~ 55t including the payload adaptor and intermediate fairing. Block 2's stated capabilities are 49t to TLI, so on paper it's a no-go although they might be sandbagging a bit.

Your estimated extra propellant of 6.5 tons required might not be including the required propellant to also get the Orion back to Earth. I estimated 10 tons extra propellant required.

With an added 0.6 tonnes ESM dry mass as proposed by @RCgothic, Orion needs ~6 tonnes of remaining props to develop the 900 m/s of dV needed to return from LLO to Earth entry interface post-mission. The launch mass of the entire Apollo LM (initial pre-extension configuration, Apollo 11-14) was 15.2 tonnes. Unfortunately, Orion can't brake that much weight from TLI into low lunar orbit, not even with @RCgothic's upgrade. It would need to be carrying a minimum of 13.4 tonnes of propellant plus the 6 tonnes it needs for the return.

On 1/27/2024 at 2:38 AM, Exoscientist said:

The Orion/service module weighs 26.5 tons. A 15 ton lander would bring the TLI mass to 41.5 tons. I made two suggestions to deal with this added mass to TLI: adding a Centaur V at 50-ton size as a 3rd stage or going back to the J-2X engine  for the Boeing EUS upper stage that had been planned. A preliminary calculation suggest they should be able to do > 42 tons to TLI.

SLS Block 2 is already expected to be capable of delivering this much to TLI. If you're proposing a single-launch architecture for SLS Block 2, that's one thing; if you're proposing a different version of SLS Block 2, that's a different thing.

On 1/27/2024 at 2:38 AM, Exoscientist said:

A ca. 2 ton mass lunar crew module should be able to do over a week stay on the Moon based on the Cygnus module.

I explained to you four months ago that the minimum mass of a Standard-Cygnus-derived crew module would be over 2.6 tonnes, not 2 tonnes -- before adding life support or astronauts -- and would be end up taking up double the maximum amount of vertical space available for co-manifested cargo.

On 1/27/2024 at 2:38 AM, Exoscientist said:

The uncertainty is in whether the usage described in the article below includes independent life-support on the Cygnus or if it is taking life-support from the Orion:

Orbital’s proposal, outlined in this PDF, involves docking a Cygnus spacecraft with Orion to serve as a habitation and logistics module on longer flights. For these missions, the re-purposed Cygnus would be called the Exploration Augmentation Module (EAM). With its current life support systems used to transport pressurized cargo and experiments to the ISS, Cygnus is stated as being already suitable for the long term support of a crew. While berthed to Orion, Cygnus could support a crew of four for up to 60 days.

Spoiler

 

There is no uncertainty here at all. The proposed Exploration Augmentation Module (which is based on the proposed four-segment "Super" version of the Enhanced Cygnus in your post, not the much lighter Standard Cygnus) could support a crew of four for up to 60 days while berthed to Orion. It cannot do so independently, and there was no suggestion or implication by anyone that it could do so independently.

On 1/28/2024 at 8:50 AM, Exoscientist said:

On 1/28/2024 at 4:15 AM, SunlitZelkova said:

Starship HLS already has a prototype flying in the form of the current ships, and has already appeared in metal in the form of mockups. Even the tanker variants have been manufactured in some form, IIRC. How is this new lander going to get ahead of something that already exists?

 Not exploding is an important requirement for a rocket, especially for one intended to carry crew.

Agreed. Important requirements for a rocket include:

• Not exploding (AS-203, A-003)
• Engines not failing (AS-101, Apollo 6)
• Helium staying out of the combustion chamber (AS-201)
• Maintaining steering control during reentry (AS-201)
• Avoidance of re-contact between stages (A-001)
• Recovery parachutes remaining intact (A-001)

All of those important requirements failed during the Apollo test program. Fortunately, the Apollo test program was a test program and not an operational mission program. Also fortunate, the Starship test program is a test program and not an operational mission program.

On 1/28/2024 at 8:50 AM, Exoscientist said:

 For the alternative proposal using a hydrolox stage for the propulsion of a lunar  lander, this propulsive stage already exists and been flown multiple times for the upper stage of the Ariane 4 rocket.

As noted, I explained to you four months ago why neither the H10-3 nor the H10+ would be acceptable for this due to having the wrong engine and too much vertical height and not enough mass budget for landing legs and a low-boiloff system.

On 1/28/2024 at 8:50 AM, Exoscientist said:

 For the Cygnus capsule, it has been flown multiple times as a unmanned cargo craft and is planned to be a manned component of a space station. As I mentioned though I’m not certain it has it’s own independent life support systems.

You can be certain that it does not.

On 1/28/2024 at 8:50 AM, Exoscientist said:

The Cygnus itself weighs 2, 000 kg. I don’t think adding life-support would add too much more to that mass.

The Cygnus itself has a mass of 3,300 kg, which could maybe be reduced to 2,630 kg if you do a complete redesign and strip away everything that makes it useful.

[sevenperforce]

23 hours ago, RCgothic said:

There seems to be a discrepancy in some of the DV maps I've been using. Depending on whether it's 680m/s or ~820m/s - if the latter I get about 10.7t additional mass required to get to LLO with a 15t payload and return with ~100m/s margin for free-flight and rendezvous. So that's 60t to TLI required, as near as matters, to land an Apollo LM on the moon using SLS and Orion.

I wrote the Wikipedia sub-entry for cislunar delta-v budget, based on the 2015 NASA manuscript detailing options for staging orbits in cislunar space and other NASA resources. That latter paper is probably the most instructive here (see page 6, labeled page 232, in particular). For three-day direct-transfer trajectories between LEO and LLO, TLI will cost you 3.152 km/s and LOI will cost you 893 m/s. The LOI burn is reversed to return to Earth entry interface. The absolute lowest-LOI-cost direct transfer, at 4.5 days transit, is 813 m/s.

If you want to get under 700 m/s then you need a long-duration low-energy transfer. Page 10 (labeled page 236) shows a transfer to LLO which costs only 670 m/s but takes 84 days. If you can handle a 129-day transit then you can get this as low as 651 m/s, per Table 4-4 on page 14(240).

23 hours ago, RCgothic said:

I already think the Apollo LM is far less capable than we need, a 2t Cygnus derived lander ludicrously, even dangerously so.

Absurdly so.

7 hours ago, Exoscientist said:

Perhaps the higher 60 ton you’re getting comes from including the Launch Abort System(LAS)?

No, he's talking about the amount of propellant needed for Orion to go through LLO rather than through NRHO.

[Exoscientist]

11 hours ago, sevenperforce said:

There is no uncertainty here at all. The proposed Exploration Augmentation Module (which is based on the proposed four-segment "Super" version of the Enhanced Cygnus in your post, not the much lighter Standard Cygnus) could support a crew of four for up to 60 days while berthed to Orion. It cannot do so independently, and there was no suggestion or implication by anyone that it could do so independently.

On 1/28/2024 at 8:50 AM, Exoscientist said:

 

The uncertainty stems from the phrasing in this passage in this article, which after all, is not a technical paper:

 

ORBITAL PROPOSES FUTURE DEEP SPACE APPLICATIONS FOR CYGNUS.
SPACEFLIGHT INSIDER
MAY 1ST, 2014
Orbital’s proposal, outlined in this PDF, involves docking a Cygnus spacecraft with Orion to serve as a habitation and logistics module on longer flights. For these missions, the re-purposed Cygnus would be called the Exploration Augmentation Module (EAM). With its current life support systems used to transport pressurized cargo and experiments to the ISS, Cygnus is stated as being already suitable for the long term support of a crew. While berthed to Orion, Cygnus could support a crew of four for up to 60 days. Cygnus also has the capability of storing food, water, oxygen, and waste and features its own power and propulsion systems. The EAM would utilize the enhanced configuration Cygnus, which will begin flying larger cargoes to the ISS beginning with CRS-4 in 2015. An even larger version is also being proposed, featuring a 4-segment pressurized cargo module.

https://web.archive.org/web/20160512141500/https://www.spaceflightinsider.com/missions/commercial/orbital-proposes-future-deep-space-applications-cygnus/ (I couldn’t get that Spaceflightinsider.com link to open, so I’m giving the Archive.org link here.)

 The first part of the passage suggests the Cygnus already has life support systems in its role as a cargo supply craft for the ISS. But then the second part of the passage suggests it would need to be connected to the Orion to support a crew of 4 for 60 days.   

 IF the Cygnus already has life support it’s possible this alone would support a crew of, say, two, for a period of, say, a week.

  Robert Clark

 

 

 

 

 

Edited January 30 by Exoscientist
Removed incompatible formatting.

[sevenperforce]

7 minutes ago, Exoscientist said:

The first part of the passage suggests the Cygnus already has life support systems in its role as a cargo supply craft for the ISS. But then the second part of the passage suggests it would need to be connected to the Orion to support a crew of 4 for 60 days.   

 IF the Cygnus already has life support it’s possible this alone would support a crew of, say, two, for a period of, say, a week.

The article describes the extent of the current "life support systems": it has everything necessary to "transport pressurized cargo and experiments" to ISS. In other words, it has the ability to maintain pressure and temperature. This makes it suitable for supporting crew while berthed to Orion, because it can independently maintain pressure and temperature. It does not have what we would consider to be a life support system for crew.

[RCgothic]

Your copied text is interfering with dark mode again, @Exoscientist btw.

When I rounded up to 60t, it was on the basis that SLS Block 2 Cargo can do 46t to TLI but B2 Crew can only do 43t. There's a 3t penalty associated with the LAS and the intermediate payload fairing (which does get carried through TLI).

I inadvertently used 6t, (because apparently 46-43 is difficult math) but with sevenperforce's DV correction it comes out roughly the same anyway:

A lander from scratch, stretched ESM, and an SLS Block 3 upgrade would not be better/faster/cheaper than the current approach.

[tater]

Before Constellation, during the Shuttle era, there was talk about cislunar architectures using Shuttle, and later using Shuttle-derived vehicles like Shuttle-C. One was the Early Lunar Access concept:

That (ELA) was a pathfinder for the later First Lunar Outpost:

 

Projects like this, but with a modern take could certainly work, but the dev time would be substantial.

Edited January 30 by tater

[darthgently]

Strange thought. 

I'm picturing something like the Apollo SM for between earth and moon and back, but with a Crew Dragon instead of the Apollo capsule.  No LEM.

Would Crew Dragon with super dracos have the fuel capacity to make a lunar powered landing from LLO followed by launch to rendezvous in LLO?  Given the TWR of the super dracos more fuel and life support could be carried; maybe just enough to get boots on the ground first at the poles, maybe go give SLIM a manual push into correct orientation.  A plethora of lunar romp possibilities.   Probably need better shielding.  SM could have reserves for fuel, oxygen, etc, so maybe multiple landings in a mission?

[SunlitZelkova]

1 hour ago, darthgently said:

Strange thought. 

I'm picturing something like the Apollo SM for between earth and moon and back, but with a Crew Dragon instead of the Apollo capsule.  No LEM.

Would Crew Dragon with super dracos have the fuel capacity to make a lunar powered landing from LLO followed by launch to rendezvous in LLO?  Given the TWR of the super dracos more fuel and life support could be carried; maybe just enough to get boots on the ground first at the poles, maybe go give SLIM a manual push into correct orientation.  A plethora of lunar romp possibilities.   Probably need better shielding.  SM could have reserves for fuel, oxygen, etc, so maybe multiple landings in a mission?

It better, even without stopping in LLO, because for my world where the Constellation program succeeds and Musk dies in a car crash in 2012 or so, I was planning to have  Red Dragon derived craft be the primary lunar base resupply vehicle (the LSAM with a cargo module would not be able to fly often enough) in the late 2020s.

[Exoscientist]

11 hours ago, sevenperforce said:

The Cygnus itself has a mass of 3,300 kg, which could maybe be reduced to 2,630 kg if you do a complete redesign and strip away everything that makes it useful.

 The original size Cygnus has volume 18 cu. meters, nearly the size of the Orion capsule itself, and only weighed 2,000 kg. Since it would only be needed for a two crew for a week, you would not need the larger size versions.

12 hours ago, sevenperforce said:

With an added 0.6 tonnes ESM dry mass as proposed by @RCgothic, Orion needs ~6 tonnes of remaining props to develop the 900 m/s of dV needed to return from LLO to Earth entry interface post-mission. The launch mass of the entire Apollo LM (initial pre-extension configuration, Apollo 11-14) was 15.2 tonnes. Unfortunately, Orion can't brake that much weight from TLI into low lunar orbit, not even with @RCgothic's upgrade. It would need to be carrying a minimum of 13.4 tonnes of propellant plus the 6 tonnes it needs for the return.

 The Orion service module already has 9 tons propellant, plus adding on an 10 additional tons  brings the propellant load to 19 tons.

 

Robert Clark

[tater]

Cygnus is the Pressurized Cargo Module (PCM) plus the Service Module (SM), where the original 5.1 meter version PCM was 1500 kg empty, and the SM is another 1800 kg of which 800 kg is propellant. So 3300 kg gross (no cargo), or 2500 kg with no propellant.

[Ultimate Steve]

Are you sure that number in the figure is the mass and not the maximum mass of payload you can stick into it?

[tater]

7 hours ago, Ultimate Steve said:

Are you sure that number in the figure is the mass and not the maximum mass of payload you can stick into it?

The standard size vehicle holds 2000kg of cargo, so the number in the pic is the cargo, not vehicle mass.

[Exoscientist]

8 hours ago, Ultimate Steve said:

Are you sure that number in the figure is the mass and not the maximum mass of payload you can stick into it?

  Right. That is cargo mass. But other references put the dry mass of the Cygnus  cargo spacecraft even in the "Enhanced" version as under 2,000 kg:

	Standard	Enhanced
Length	5.14m	6.39m
Diameter	3.07m	3.07m
Dry Mass	1,500kg	1,800kg
Pressurized Volume	18.9m³	27m³
Cargo Mass	2,000kg	3,500kg
Disposal Payload	1,200kg	3,500kg
Endurance	2 Months	66 Days
Solar Arrays	Dutch Space	ATK Ultra Flex
RNDZ Nav	TriDAR	TriDAR

Cygnus consists of a Pressurized Cargo Module that is built by Thales Alenia Space of Italy and a Service Module built by Orbital, based on Orbital’s GEOStar Satellite Bus and Dawn spacecraft elements to reduce cost and risk.

Cygnus is booked for a single COTS Demo mission to ISS and a total of eight CRS flights. For its first four flights, Cygnus flies in its standard configuration. When the Antares is upgraded with the Castor 30 XL second stage, Cygnus will transition to its enhanced version to carry more cargo to ISS. Cygnus standard carries 2,000kg of cargo to ISS while the enhanced version has a cargo capability of 3,500kg, limited by launch vehicle performance.
https://spaceflight101.com/spacecraft/cygnus/

 (Note: to maintain the format of the table, this copies directly from the web page so the numbers might not be visible in "dark mode".)

 For the use as a lunar crew module, the Cygnus' service module that provides its propulsion won't be used since the propulsion will be provided by a separate, existing rocket stage.

  Bob Clark

 

[tater]

36 minutes ago, Exoscientist said:

  Right. That is cargo mass. But other references put the dry mass of the Cygnus  cargo spacecraft even in the "Enhanced" version as under 2,000 kg:

 

9 hours ago, tater said:

Cygnus is the Pressurized Cargo Module (PCM) plus the Service Module (SM), where the original 5.1 meter version PCM was 1500 kg empty, and the SM is another 1800 kg of which 800 kg is propellant. So 3300 kg gross (no cargo), or 2500 kg with no propellant.

 

[Exoscientist]

15 hours ago, tater said:

 

...

 

 

Projects like this, but with a modern take could certainly work, but the dev time would be substantial.

 

 HA! You think that puny 30 foot distance for astronauts to climb down looks scary?

Check out the 75 foot distance SpaceX offers:

 

 Now, THAT's what I call an impressive distance to the surface!

 

   Robert Clark 

[tater]

I'd rather spend a week or two on the Moon way up on top of Starship with my own sleeping quarters, and the bathroom downstairs, than with 3 other people, doffing their dusty EVA suits, eating, and using the toilet in a single room the size of my SUV.

[tater]

oops

Edited January 30 by tater

[PakledHostage]

1 hour ago, Exoscientist said:

 Now, THAT's what I call an impressive distance to the surface!

Reminds me of my first Kerbaled mission to Duna... Just jump, Bill!

[StrandedonEarth]

4 hours ago, PakledHostage said:

Reminds me of my first Kerbaled mission to Duna... Just jump, Bill!

And to get back in he had to jump with RCS blasting, RCS was too weak otherwise…. So, MMUs for emergency ingress?

Edited January 30 by StrandedonEarth