totm dec 2023 Artemis Discussion Thread

[tater]

7 hours ago, RCgothic said:

If we're dropping SLS/Orion, is there a better lunar rendezvous point than NRHO?

 

Both vehicles are capable of flying a round trip (no aerobraking required) from LEO with refilling in lunar orbit. That lunar orbit could be at Gateway (NRHO) if it already exists, or could be some other orbit (a low, frozen orbit has been proposed before).

Edited May 30, 2023 by tater

[tater]

To be fair, NRHO is not awful, the thermal environment is decent, I read that boiloff in higher lunar orbits is ~10X lower than LEO, presumably reflection from the lunar surface during daylight orbital passes in lower orbits is a thermal issue as well.

Edited May 30, 2023 by tater

[Barzon]

10 hours ago, tater said:

To be fair, NRHO is not awful, the thermal environment is decent, I read that boiloff in higher lunar orbits is ~10X lower than LEO, presumably reflection from the lunar surface during daylight orbital passes in lower orbits is a thermal issue as well.

You also get constant communications, and it's a pretty decent departure point for Mars & beyond, iirc there are trajectories that can send a spacecraft from NRHO to Mars with double or even single digits of Δv.

[tater]

42 minutes ago, Barzon said:

You also get constant communications, and it's a pretty decent departure point for Mars & beyond, iirc there are trajectories that can send a spacecraft from NRHO to Mars with double or even single digits of Δv.

Constant comms is simply putting a constellation near the Moon, it's not enough of a plus to matter. The departure point for Mars is not a thing unless somehow ISRU is providing the props, since everything leaving NRHO has to get there first. A full tanker gets ~25% of it's LEO prop load to NRHO, and the same tanker needs about half of that to return to LEO, so we're talking getting ~15% of props moved to LEO into a vehicle at NRHO. Not really seeing any benefit.

[Barzon]

10 hours ago, tater said:

Constant comms is simply putting a constellation near the Moon, it's not enough of a plus to matter. The departure point for Mars is not a thing unless somehow ISRU is providing the props, since everything leaving NRHO has to get there first. A full tanker gets ~25% of it's LEO prop load to NRHO, and the same tanker needs about half of that to return to LEO, so we're talking getting ~15% of props moved to LEO into a vehicle at NRHO. Not really seeing any benefit.

Most of the architectures NASA are studying rn involve a checkout in NRHO of the MTV habitat, with MTV assembly in orbits ranging from MEOs to LDHEOs, which is advantageous as it means you can test it in a deep space environment with or without crew before sending it to Mars, using Gateway as a safe-haven, and taking over station keeping for that module when needed. If you want I can post the some of the recent studies they've published.

[tater]

42 minutes ago, Barzon said:

Most of the architectures NASA are studying rn involve a checkout in NRHO of the MTV habitat, with MTV assembly in orbits ranging from MEOs to LDHEOs, which is advantageous as it means you can test it in a deep space environment with or without crew before sending it to Mars, using Gateway as a safe-haven, and taking over station keeping for that module when needed. If you want I can post the some of the recent studies they've published.

Not sure what benefit there is from a "deep space environment" except exposing the crew to more radiation.

Regardless, NASA is not sending anyone to Mars with their DRM/DRA architectures (which I have read). It's whatever architecture SpaceX comes up with or it's not happening. The NRHO as a staging area to Mars is 100% because SLS is awful.

(interestingly, it's also why it will never happen, because SLS could not possibly build such a mission, it can never have a cadence that would support that).

[darthgently]

27 minutes ago, tater said:

Not sure what benefit there is from a "deep space environment" except exposing the crew to more radiation.

All I can think of, after reading your reply, is reality testing radiation shielding.  But that doesn't require building an entire ship in deep space, just sending one there with radiation monitors in an uncrewed crew compartment

[Exoscientist]

On 5/29/2023 at 7:54 PM, mikegarrison said:

There are only so many pixels available to any camera. It can use them for wider shots where it gets more field of view and less resolution, or it can use them for more focused shots where it gets more resolution and less field of view. The same is also true for your eye looking through a telescope, or anything similar to that.

Thanks for that. I looked up the specs for the HIRISE camera on MRO:

Red color images are at 20,048 pixels wide (6 km in a 300 km orbit), and blue-green and NIR are at 4,048 pixels wide (1.2 km). These are gathered by 14 CCD sensors, 2048 × 128 pixels. HiRISE's onboard computer reads out these lines in time with the orbiter's ground speed, meaning the images are potentially unlimited in height. Practically this is limited by the onboard computer's 28 Gbit (3.5 GB) memory capacity. The nominal maximum size of red images (compressed to 8 bits per pixel) is about 20,000 × 126,000 pixels, or 2520 megapixels and 4,000 × 126,000 pixels (504 megapixels) for the narrower images of the B-G and NIR bands. A single uncompressed image uses up to 28 Gbit. However, these images are transmitted compressed, with a typical maximum size of 11.2 gigabits. These images are released to the general public on the HiRISE website via a new format called JPEG 2000.[22][23] https://en.m.wikipedia.org/wiki/HiRISE#Design

  

 So the main issue is memory size. There are commercial multi-terabyte hard drives and flash drives, thumb drives, available now. So the storage memory can be ramped up tens of thousands of times now. That should be enough to image entire swaths of Mars surface at high resolution at once.

  Bob Clark

  

Edited May 31, 2023 by Exoscientist

[tater]

1 hour ago, Exoscientist said:

 So the main issue is memory size. There are commercial multi-terabyte hard drives and flash drives, thumb drives, available now. So the storage memory can be ramped up tens of thousands of times now. That should be enough to image entire swaths of Mars surface at high resolution at once.

The problem with most spacecraft is cost/mass. Better off the shelf storage hardware certainly exists, but the other concern is radiation. Given the expense and rarity of a spot on such a spacecraft they tend to try and pick the most reliable possible hardware. So if the best rad-hard chips have less capacity... that's what you pick. There's also lead time. Moore's law is plugging along, but the time from funding secured to critical design review could be sorta short, say a couple years—but launch might not be for several years after that. The chipset is obsolete long before launch.

When mass is less of a constraint, just chuck multiple redundant systems on it, use off the shelf—but shield them (more mass).

[Barzon]

  

9 hours ago, tater said:

Not sure what benefit there is from a "deep space environment" except exposing the crew to more radiation.

 

would you argue A1 would have achieved the same goals if Orion was sent to LEO instead of DRO?

9 hours ago, tater said:

(interestingly, it's also why it will never happen, because SLS could not possibly build such a mission, it can never have a cadence that would support that).

The most recently released studies allow construction of a vehicle with a 1 or 2 per year flight rate.

Anyways ML-2 hardware is arriving at KSC soon:

 

Edited May 31, 2023 by Barzon

[tater]

39 minutes ago, Barzon said:

would you argue A1 would have achieved the same goals if Orion was sent to LEO instead of DRO?

No, the point was testing the capsule TPO.

39 minutes ago, Barzon said:

The most recently released studies allow construction of a vehicle with a 1 or 2 per year flight rate.

The latest DRA is 5.0. It predates SLS.

The mission is 2 parts, the cargo component has 7 launches of ARES V to LEO in the span of 170 days. Ares V was estimated at ~188t to LEO. The crew transfer vehicle is 5 launches (1 might be Ares I with Orion) in a period of 120 days 2 years later. So 3.5 to 7 times as many launches in half a year... oh, wait, but at almost twice the mass to LEO. So 7-15 SLS launches in 6 months. Only one every 2 weeks! Easy! And to LEO. So multiply that by 4 for NRHO for the solid bits, but it needs a lower prop mass for the TMI stage is all. I don't feel like doing the math.

SLS is incapable of Mars missions.

Edited May 31, 2023 by tater

[Barzon]

5 minutes ago, tater said:

No, the point was testing the capsule TPO.

The latest DRA is 5.0. It predates SLS.

The mission is 2 parts, the cargo component has 7 launches of ARES V to LEO in the span of 170 days. Ares V was estimated at ~188t to LEO. The crew transfer vehicle is 5 launches (1 might be Ares I with Orion) in a period of 120 days 2 years later. So 3.5 to 7 times as many launches in half a year... oh, wait, but at almost twice the mass to LEO. So 7-15 SLS launches in 6 months. Only one every 2 weeks! Easy! And to LEO. So multiply that by 4 for NRHO for the solid bits, but it needs a lower prop mass for the TMI stage is all. I don't feel like doing the math.

SLS is incapable of Mars missions.

Thats... not the latest study. There were studies on reference architectures released as recently as last year.

Here's an overview of the NTP architecture study that the MTAS Team released last year, and a final report from '21 on the 4th iteration of the GRC's Compass team's CHEMNEP architecture that they've been studying for a fair while now.

https://ntrs.nasa.gov/api/citations/20220006985/downloads/Edwards.Gerrish.Houts.PresbyMTASpanelSlides.pptx.pdf

 

https://ntrs.nasa.gov/api/citations/20210017131/downloads/TM-20210017131_errata.pdf

[tater]

3 minutes ago, Barzon said:

Thats... not the latest study. There were studies on reference architectures released as recently as last year.

DRA 5 is the last complete one. If you have a reference, by all means post it.

[SunlitZelkova]

1 hour ago, tater said:

DRA 5 is the last complete one. If you have a reference, by all means post it.

Click on his first link (top one). The architecture seems pretty complete, it even incorporates Starship and New Glenn.

It requires 3 SLS launches and 23 launches from either SS or NG. One thing I dislike about it is not taking Orion along, because that forces the use of another SLS just to pick the crew up.

Also, as an Orion fan I would love to see it go to Mars. Note that I hold this position not from an economical or logical POV, just a simple space person one.

I am on the fence about it at the same time. On the one hand, I think people should give it a break because even if SLS goes, there needs to be some pork, but on the other hand, with LSS and the new BO lander, there is no reason not to just launch crew into LEO on Crew Dragon and have them transfer to the lander.

But anyways.

SLS launches the propulsion module with 2x NTRs, and a core module that presumably carries fuel. The MTV has a whopping 17 drop tanks.

It seems like a pretty robust architecture. The obvious elephant in the room is why use SLS when Starship exists, but it isn't too bad if one assumes pork needs to exist. The only changes I think that could be made would be relying on SLS solely for crew transport, and using Starship to launch the main tank and propulsion stage. That way it would align with Artemis- SLS does crew launch, Starship and BO do the transport to the place. Heck, this design does not have a lander so Starship itself could serve as one.

Another thing I am on the fence about is MTV design. On the one hand, it would be good to have a big ship so you have redundancy in the event of an Apollo 13 type situation, but on the other hand, if Orion already takes crew to the Moon by itself, why not use Starship by itself to take crew to the Moon... or Mars? I guess the time and scale of the mission is one factor, but still.

[tater]

43 minutes ago, SunlitZelkova said:

Click on his first link (top one). The architecture seems pretty complete, it even incorporates Starship and New Glenn.

Not a DRA, and NTP is at what TRL? DOn't get me wrong, I like NTP a lot (and I know Mike).

Why does it use SLS at all? If SS is a thing, any SLS launch is wasted. If Orion is not going along, even launching Orion is wasted, load crew with a CCV. Even expended, SS and NG completely obviate any use of SLS here—unless the important goal is to make it "cost more."

 

43 minutes ago, SunlitZelkova said:

It requires 3 SLS launches and 23 launches from either SS or NG. One thing I dislike about it is not taking Orion along, because that forces the use of another SLS just to pick the crew up.

23 SS launches? LOL. the 3 SLS launches will cost more than all the other launches combined.

NRHO... for reasons?

Is the "Lander Orbital Ops from previous cargo launches × 3" included in the 3 SLS and 23 commercial launches? What are the masses? Again, why SLS at all—is it solely to increase the cost by an order of magnitude?

 

43 minutes ago, SunlitZelkova said:

Also, as an Orion fan I would love to see it go to Mars. Note that I hold this position not from an economical or logical POV, just a simple space person one.

The only reason to bring Orion is to use it for direct entry on return to Earth. Other than that, it's a lousy vehicle—what's the claimed max duration of Orion right now, anyway? They'd presumably want to test one on orbit for a few years sitting there doing nothing first.

 

43 minutes ago, SunlitZelkova said:

I am on the fence about it at the same time. On the one hand, I think people should give it a break because even if SLS goes, there needs to be some pork, but on the other hand, with LSS and the new BO lander, there is no reason not to just launch crew into LEO on Crew Dragon and have them transfer to the lander.

But anyways.

SLS launches the propulsion module with 2x NTRs, and a core module that presumably carries fuel. The MTV has a whopping 17 drop tanks.

Whatever it launches it's grossly less than expended SS could deliver—and 1-2 orders of magnitude more expensive. I'd add that since the bulk of the SLS mass to LEO is residual props, the NTP stage either has to do the burn itself AS stage 2, or it will be volume, not mass limited (propellant is LH2)—as they say.

43 minutes ago, SunlitZelkova said:

It seems like a pretty robust architecture. The obvious elephant in the room is why use SLS when Starship exists, but it isn't too bad if one assumes pork needs to exist. The only changes I think that could be made would be relying on SLS solely for crew transport, and using Starship to launch the main tank and propulsion stage. That way it would align with Artemis- SLS does crew launch, Starship and BO do the transport to the place. Heck, this design does not have a lander so Starship itself could serve as one.

LOL, yeah, the pork must flow. No need for Orion, no need for Starship. Luckily since any "Moon to Mars" stuff is a long way out, the existence of either lander at all will kill SLS entirely, and Orion has always been useless.

43 minutes ago, SunlitZelkova said:

Another thing I am on the fence about is MTV design. On the one hand, it would be good to have a big ship so you have redundancy in the event of an Apollo 13 type situation, but on the other hand, if Orion already takes crew to the Moon by itself, why not use Starship by itself to take crew to the Moon... or Mars? I guess the time and scale of the mission is one factor, but still.

Yeah. Course this is the sales pitch by Houts, et al, and I am cool with NASA pushing NTP, but it's not the reference mission yet.

 

[tater]

The most comical thing about the NEP link is that they're talking about 2039, 2040—and it mentions Orion. LOL.

They think they'll get NEP going, with the critical constraints being the power density of reactors coming way, way down—and they think Orion would still be a thing?

[tater]

15 hours ago, tater said:

23 SS launches? LOL. the 3 SLS launches will cost more than all the other launches combined.

odd to quote myself, lol.

23 NG launches will cost half as much as a single SLS launch assuming they are F9/Vulcan competitive at $80M each.

Starship is similar. Expendable SS launches would have to cost $182M each for 23 of them to equal a single SLS/Orion launch.

[SunlitZelkova]

18 hours ago, tater said:

The only reason to bring Orion is to use it for direct entry on return to Earth. Other than that, it's a lousy vehicle—what's the claimed max duration of Orion right now, anyway? They'd presumably want to test one on orbit for a few years sitting there doing nothing first.

Yeah. The Apollo Manned Venus Flyby had them testing the entire spacecraft in a yearlong flight in GEO before attempting an interplanetary mission.

[lajoswinkler]

Some eyecandy.

 

Edited June 17, 2023 by lajoswinkler

[Exoscientist]

NASA suggests Artemis lander flight likely pushed back to 2026 due to Starship delay. The NASA official quoted suggests needed launches for qualifying Starship plus the needed launches for the refueling flights will likely delay the Artemis landing flight:

NASA predicts delay: Starship grounded pending investigation

By Steve Clark - June 28, 2023

https://myrgv.com/local-news/2023/06/28/nasa-predicts-delay-starship-grounded-pending-investigation/

 Robert Clark

[tater]

They also don't have spacesuits.

Also, Artemis II is NET Nov 2024, and Q4 always ends up at least Q1 the next year. So there's no way Artemis III flies until 2026 anyway. But it's the fault of Starship.

[tater]

 

Somehow we're to believe SLS has a 2+ year cadence, except for Artemis II  to III. I to II is gonna be >2 years, and assuming III is in 2025, IV is a 3 year gap you'd expect cadence to improve, not get worse).

xEVA suits have had no schedule margin for a few years now, so literally every delay is a delay they can't make up.

[tater]

I should be clear that I think Starship is also clearly running behind schedule, but claiming it is the sole cause of any delay is untrue.

[SunlitZelkova]

The more it gets pushed back the more interesting it becomes. If it takes until 2027 for Artemis III to launch due to SLS delays, it will have taken the same amount of time from Apollo’s announcement to their landing (Artemis began in 2019).

[Barzon]

 

 

 

http://www.nasa.gov/press-release/nasa-expands-options-for-spacewalking-moonwalking-suits-services 

Quote

The latest Exploration Extravehicular Activity Services task orders, each with a value of $5 million, are intended to have Axiom Space begin work on a spacesuit for use in  low Earth orbit, and Collins Aerospace to begin work on a spacesuit for use on the lunar surface.