Released yesterday: NASA Moon to Mars Architecture.We have a potential for dueling threads here, in that this is also tucked in under Moon to Mars Objectives as well. Mods should make an executive decision ASAP and cauterize one of these soon.
First impression of the Mars segment: They're sticking with the TransHab to Mars, and they're sticking with the assumption that it needs to propulsively capture into Mars orbit, with enough prop to return via an opposition-class orbit. That's the bad news.The good news is that, unlike DRA 5.0, which assumed nothing but Ares V-launched cargo pre-positioning missions, they've adopted a wide range of CLV-launched cargo options, and they've left open the possibility that the lander could be either a "flat bed" lander, with crew and payload close to the ground, or a "vertical lander", which is obviously supposed to be a Starship.The other thing of note is that they're looking even more seriously at short-stay architectures for the first mission. Short-stay missions overall have shorter total mission time, which is nice from a hardware reliability standpoint, but they have considerably longer transit times, which is bad from a crew microgravity and radiation exposure standpoint.The conops that goes something like this:1) Send a whole bunch of surface assets in the synod before, including your surface-to-LMO ascent vehicle.2) Assemble the DST, whatever it turns out to be, at the Gateway.3) Push the DST into what they're calling a lunar distance high earth orbit (LDHEO). Note that this is basically the Artemis NRHO fast return to TEI, but the TEI results in the spacecraft going into something like a 500km x 380,000km HEEO.4) Crew, via SLS/Orion, does RPOD with the DST in LDHEO.5) DST, with one of a number of propulsion options (NEP+chemical, SEP+chemical, NTP, or all-chemical), does a conjunction-class TMI, taking the Orion with them.6) DST propulsively enters a 5-sol eccentric Mars orbit (HEMO?) and does RPOD with the lander.7) Lander goes to surface for a ~30day crew stay.8 ) Crew returns on pre-positioned Mars ascent vehicle, does RPOD with the DST.9) DST returns on an opposition-class TEI, which may or may not require a Venus flyby to make the Earth arrival speed viable.10) Presumably, the crew would then use an Orion to reenter.One thing I don't understand is why they wouldn't be adopting a long-stay mission (i.e., wait 500days for a conjunction-class return), but have a short-stay oppo-class return as an abort option. If I ran the circus, and I had a lot of delta-v available (wonder what could provide that?), I'd do the following:a) Depart in the DST on a conjunction-class orbit with enough energy to do a 2:1 resonance heliocentric orbit with Earth, allowing a free-return to Earth if something went bad in transit.b) After a go/no-go commit to Mars orbit insertion, insert. I suspect that with the 2:1 orbit, aerocapture becomes a requirement. (Direct EDL is not a requirement.) If no-go, just keep going. It's a long trip home, but it doesn't require any major propulsion.c) Do RPOD with the lander (which I really want to call HLS-M).d) A second go/no-go decision here: land, or not? If not, the DST departs within 30days to an oppo-class abort to Earth. Otherwise...e) Descend to the surface and its pre-positioned equipment.f) Do a stay/no-stay decision within the first couple of weeks. If no-stay, use the Mars ascent vehicle back to the DST and do the oppo-class abort.g) If staying, you commit to the full 500day stay.h) 500days later, use the MAV to return to the DST, which then does a conjunction-class TEI.i) Do direct EDL, using Orion (or something else!).The caveat to all of this is the "lots of delta-v" requirement. But we now know how to send (or make) as much prop as necessary to provide copious amounts of delta-v for the mission--as long as Starship works.Note that, as with the Artemis architecture, all the human stuff is nominally under NASA's control, and nominally finds a way to use at least one SLS/Orion flight to ferry the crew from Earth to LDHEO, where the Orion goes along for the ride and acts as the Earth EDL vehicle. But also note, just like with Artemis, it's easy to substitute a Starship for a lot of the pieces-parts in here.Procedural question for the thread: I'm sure there's a planetary protection food fight in the offing. I propose the following truce:A) We all agree that there are huge modifications to Category IV, which will occur, and we don't talk about them here.B) There are more substantive issues with Category V (protecting Earth from the returning vehicles and crew). We could spin those off into a separate thread or deal with them here. IMO: the core requirement is that the vehicle that does EDL breaks the chain of contact by never having touched the surface of Mars. Note that Orion is ideal for this, but you could do the same with a Starship that stayed in LMO.
Quote from: TheRadicalModerate on 04/19/2023 09:10 pmFirst impression of the Mars segment: They're sticking with the TransHab to Mars, and they're sticking with the assumption that it needs to propulsively capture into Mars orbit, with enough prop to return via an opposition-class orbit. That's the bad news.The good news is that, unlike DRA 5.0, which assumed nothing but Ares V-launched cargo pre-positioning missions, they've adopted a wide range of CLV-launched cargo options, and they've left open the possibility that the lander could be either a "flat bed" lander, with crew and payload close to the ground, or a "vertical lander", which is obviously supposed to be a Starship.The other thing of note is that they're looking even more seriously at short-stay architectures for the first mission. Short-stay missions overall have shorter total mission time, which is nice from a hardware reliability standpoint, but they have considerably longer transit times, which is bad from a crew microgravity and radiation exposure standpoint.The conops that goes something like this:1) Send a whole bunch of surface assets in the synod before, including your surface-to-LMO ascent vehicle.2) Assemble the DST, whatever it turns out to be, at the Gateway.3) Push the DST into what they're calling a lunar distance high earth orbit (LDHEO). Note that this is basically the Artemis NRHO fast return to TEI, but the TEI results in the spacecraft going into something like a 500km x 380,000km HEEO.4) Crew, via SLS/Orion, does RPOD with the DST in LDHEO.5) DST, with one of a number of propulsion options (NEP+chemical, SEP+chemical, NTP, or all-chemical), does a conjunction-class TMI, taking the Orion with them.6) DST propulsively enters a 5-sol eccentric Mars orbit (HEMO?) and does RPOD with the lander.7) Lander goes to surface for a ~30day crew stay.8 ) Crew returns on pre-positioned Mars ascent vehicle, does RPOD with the DST.9) DST returns on an opposition-class TEI, which may or may not require a Venus flyby to make the Earth arrival speed viable.10) Presumably, the crew would then use an Orion to reenter.One thing I don't understand is why they wouldn't be adopting a long-stay mission (i.e., wait 500days for a conjunction-class return), but have a short-stay oppo-class return as an abort option. If I ran the circus, and I had a lot of delta-v available (wonder what could provide that?), I'd do the following:a) Depart in the DST on a conjunction-class orbit with enough energy to do a 2:1 resonance heliocentric orbit with Earth, allowing a free-return to Earth if something went bad in transit.b) After a go/no-go commit to Mars orbit insertion, insert. I suspect that with the 2:1 orbit, aerocapture becomes a requirement. (Direct EDL is not a requirement.) If no-go, just keep going. It's a long trip home, but it doesn't require any major propulsion.c) Do RPOD with the lander (which I really want to call HLS-M).d) A second go/no-go decision here: land, or not? If not, the DST departs within 30days to an oppo-class abort to Earth. Otherwise...e) Descend to the surface and its pre-positioned equipment.f) Do a stay/no-stay decision within the first couple of weeks. If no-stay, use the Mars ascent vehicle back to the DST and do the oppo-class abort.g) If staying, you commit to the full 500day stay.h) 500days later, use the MAV to return to the DST, which then does a conjunction-class TEI.i) Do direct EDL, using Orion (or something else!).The caveat to all of this is the "lots of delta-v" requirement. But we now know how to send (or make) as much prop as necessary to provide copious amounts of delta-v for the mission--as long as Starship works.Note that, as with the Artemis architecture, all the human stuff is nominally under NASA's control, and nominally finds a way to use at least one SLS/Orion flight to ferry the crew from Earth to LDHEO, where the Orion goes along for the ride and acts as the Earth EDL vehicle. But also note, just like with Artemis, it's easy to substitute a Starship for a lot of the pieces-parts in here.Procedural question for the thread: I'm sure there's a planetary protection food fight in the offing. I propose the following truce:A) We all agree that there are huge modifications to Category IV, which will occur, and we don't talk about them here.B) There are more substantive issues with Category V (protecting Earth from the returning vehicles and crew). We could spin those off into a separate thread or deal with them here. IMO: the core requirement is that the vehicle that does EDL breaks the chain of contact by never having touched the surface of Mars. Note that Orion is ideal for this, but you could do the same with a Starship that stayed in LMO.It should be mentioned that Pam Melroy mentioned during her presentation (at 27 minutes) linked below that the objective for Mars is also a continued presence just like the Moon but they didn't want to plan that out just yet as what they will learn on the Moon will have an impact on longer Mars missions. https://forum.nasaspaceflight.com/index.php?topic=57221.msg2476805#msg2476805
Darn. And here I was hoping "Moon to Mars" described only the R&D pathway (which does make sense) and not the delta-v pathway. Is there any reason to favor a detour into lunar orbit over purely LEO+HEEO architectures? Are they chasing after the lunar propellant mirage again? Or is it just reverse-justification of Gateway? It all seems like a lot of work just to reduce the thrust on your TMI stage a bit. "Just" add more thrust (now cheap thanks to Raptor 2) and burn straight from LEO. Or since the lunar plan already accepts three Van Allen crossings, you can achieve the same thrust reduction* using a two-burn TMI with an intermediate HEEO parking orbit.Am I missing anything here?* Actually better thrust reduction, because you don't waste delta-v and time.
.Procedural question for the thread: I'm sure there's a planetary protection food fight in the offing. I propose the following truce:…B) … the core requirement is that the vehicle that does EDL breaks the chain of contact by never having touched the surface of Mars. …
It also seems wise that we concentrate more on early Mars missions here than turning it into yet another "Mars Colony" thread.
Quote from: TheRadicalModerate on 04/19/2023 09:10 pm.Procedural question for the thread: I'm sure there's a planetary protection food fight in the offing. I propose the following truce:…B) … the core requirement is that the vehicle that does EDL breaks the chain of contact by never having touched the surface of Mars. …ABSOLUTELY NOT and quit trying to shift the narrative by using that common demand of yours as terms of a “truce.” An attempt to rule out the standard SpaceX Mars architecture by fiat, locking us into an impossibly expensive Mars transport scheme that would make mass Mars settlement infeasible. So again, no.
Quote from: TheRadicalModerate on 04/19/2023 10:28 pmIt also seems wise that we concentrate more on early Mars missions here than turning it into yet another "Mars Colony" thread.I'd go further. There's already a bunch of threads on the different aspects of generic discussion on Mars missions, Mars bases, Mars science, ISRU, etc: So I suggest that this thread be limited to NASA's Moon To Mars strategy and information. Ie, treat this thread as close to an "update" thread as is possible while allowing discussion of the specifics of those updates.And yes, I realise that's going to result in the thread going dead for long periods. That's not a bad thing, it's just the nature of the topic.Consider that my suggestion for a "truce". If you want to debate a specific topic, like ISRU or planetary protection or SEP+orbital-assembly vs Earth-launch, etc etc, beyond anything said by NASA's M2M office, take it to the other threads or create a new thread for that. Keep this thread for just discussing the stuff coming out of the M2M office that is Mars related.
Quote from: Twark_Main on 04/20/2023 02:57 amDarn. And here I was hoping "Moon to Mars" described only the R&D pathway (which does make sense) and not the delta-v pathway. Is there any reason to favor a detour into lunar orbit over purely LEO+HEEO architectures? Are they chasing after the lunar propellant mirage again? Or is it just reverse-justification of Gateway? It all seems like a lot of work just to reduce the thrust on your TMI stage a bit. "Just" add more thrust (now cheap thanks to Raptor 2) and burn straight from LEO. Or since the lunar plan already accepts three Van Allen crossings, you can achieve the same thrust reduction* using a two-burn TMI with an intermediate HEEO parking orbit.Am I missing anything here?* Actually better thrust reduction, because you don't waste delta-v and time.To be fair, this is also a two-burn TMI.
1) You need to do a lot of live testing in an exo-magnetospheric environment, and the Gateway's the obvious place to do that.
2) If you're really serious about hybrid SEP-chemical, you'll need to have the solar panels deployed before departure (because if they fail to deploy after TMI, the crew is in some deep prune yoghurt). That would limit your maximum acceleration to something quite low during the perigee burn. Diving down from LDHEO would give a low-acceleration system more time to burn with lower non-impulsive losses.
I think you'll find that the opposite is true. You want a slower perigee velocity, but falling all the way from the Moon will result in a very fast velocity, and a short time spent down low in Earth's gravity well (ie happy Oberth ).
Quote from: TheRadicalModerate on 04/20/2023 04:35 amTo be fair, this is also a two-burn TMI.That's exactly my point. Since they're both two-burn TMIs, there's no advantage over a simple LEO+HEEO mission architecture.
To be fair, this is also a two-burn TMI.
If there is a planned crew landing on Mars by whomever. Planetary protection will very likely go out the window to ensure highest chance of the crew surviving the Mars EDL phase and maximizing overall mission success with the safe return of the crew back to Earth.
Quote from: Zed_Noir on 04/20/2023 10:33 amIf there is a planned crew landing on Mars by whomever. Planetary protection will very likely go out the window to ensure highest chance of the crew surviving the Mars EDL phase and maximizing overall mission success with the safe return of the crew back to Earth.There is need for planetary protection to go out of the window, it's objectives will just be reframed. This is already in process.
Quote from: Zed_Noir on 04/20/2023 10:33 amIf there is a planned crew landing on Mars by whomever. Planetary protection will very likely go out the window to ensure highest chance of the crew surviving the Mars EDL phase and maximizing overall mission success with the safe return of the crew back to Earth.There is [no] need for planetary protection to go out of the window, it's objectives will just be reframed. This is already in process.
2) Chemical + SEP: Severely thrust-limited around perigee
The easy answer to all of this is always going to be, "Just use a friggin' Starship and have done with it."
Quote from: Twark_Main on 04/29/2023 04:02 amQuote from: TheRadicalModerate on 04/20/2023 04:35 amTo be fair, this is also a two-burn TMI.That's exactly my point. Since they're both two-burn TMIs, there's no advantage over a simple LEO+HEEO mission architecture.We've had this argument before. There are some pretty good reasons why an L2 or L1 halo has advantages over a simple LDHEO/HEEO:1) If you're doing lots of crewed assembly and checkout (which seems to be an assumption in the doc), diving through the VA belts every ten days or so isn't great.
2) I'm still not convinced that RPOD isn't a fairly major pain in HEEO, while it's a near-linear problem in a lot of halo orbits.
3) A true HEEO, which has to be carefully engineered to avoid lunar influence,
can't be used so that crews can do double duty doing assembly/checkout of the Mars vehicle while staging down to the lunar surface or doing teleoperation of assets on the surface.
Starship could be used to build a giant nuclear powered reusable mother ship that could take a lot of cargo and people to Mars. [...] You still need a large reusable lander to set up a base and supply it. [...] Or [...] send 100's or 1,000's of [Starship variants] to Mars [...] to avoid long delays [and costs] for nuclear powered spaceships
<snip>Using Starship to travel to Mars is not just avoiding cost/delays with developing a nuclear powered ship, it's the fact that the vehicle you need to use to build that nuclear ship in Earth orbit, the vehicle you need to use to ferry people and cargo to the nuclear ship, and the vehicle you need to use to land on Mars surface from that nuclear ship is also capable of doing the same job as the nuclear ship anyway.You need a ship capable of transporting people, cargo and Mars-needed equipment from Earth surface to Mars surface in order to build a vehicle capable of only transporting the same people/cargo/equipment between Earth orbit and Mars orbit.So what does the nuclear ship actual add that Starship isn't already going to do? <snip>
