NASA Moon to Mars Architecture: The Mars Segment

[TheRadicalModerate]

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.

Update:  Per yg1968's suggestion, let's use this to discuss the Mars segment of the architecture, and the other thread can then continue with the lunar segments.

[yg1968]

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.

My own view is that it's OK to have 2 threads: one for Mars (this one) and the other one for the Moon (the Moon to Mars objectives thread).

[yg1968]

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.

It should be mentioned that Pam Melroy mentioned during her presentation (at 27 minutes) linked below that the objective for Mars is also a sustained 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

[TheRadicalModerate]

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.

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

That seems wise of her.

It also seems wise that we concentrate more on early Mars missions here than turning it into yet another "Mars Colony" thread.  This short-stay vs. long-stay issue is a big fat hairy deal.  It's ironic that short-stay is profoundly enabled by Starship's ability to fling propellant at the problem, but that Starship also greatly increases the ability to have a bulletproofed long-stay architecture.

[Twark_Main]

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.}

[TheRadicalModerate]

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.}

To be fair, this is also a two-burn TMI.  It's just that the first burn is the lunar flyby burn.  (I assume that NRHO-to-flyby is a thruster burn, because it's tiny.)

That said, reverse Gateway justification seems likely.  The best two justifications I can come up with that aren't reverse Gateway are:

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.

But giving the Gateway a reason to exist seems to make the most sense--unless somebody's planning on pulling a lunar water rabbit out of a hat.  That would be... kinda cool, but economically dumb.

[Robotbeat]

.

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.

[Paul451]

It 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.

[Zed_Noir]

.

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.

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.

Also there will be very likely no blank cheque budget for any crewed Mars surface mission.

[TheRadicalModerate]

It 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.

I'd like this to be at least discussion of the actual Mars segment architecture as described in the documents, and critiques of that architecture.

[Twark_Main]

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.}

To 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.

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.

That's what I mean by an R&D pathway, as compared to a delta-v pathway.

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 ).

[TheRadicalModerate]

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 ).

Let's break this down into the categories described in the document:

1) Chemical + NEP:  Has the advantage that you can bring your nuke online before the injection burn, and therefore you can have a near-impulsive escape burn.  Then you fire up the NEP for however much of the budget you've decided should be non-chemical.

2) Chemical + SEP:  Severely thrust-limited around perigee, which means hefty non-impulsive losses for the chemical burn.  However, from LDHEO, that's not necessarily fatal, because you presumably have a lot more power than NEP, and therefore all you need in terms of chemical delta-v is enough to get to escape, plus a smidge.

3) NTP:  More than enough thrust to get a near-impulsive injection burn all the way to a keplerian MTO.

4) All Chemical:  The same.  Just a lot more prop.  If prop isn't a major cost driver, this is clearly the way to go.

The easy answer to all of this is always going to be, "Just use a friggin' Starship and have done with it."  For obvious political reasons, NASA isn't going to tailor the entire architecture around that.  However, there are several not-so-subtle hints in the doc that you should read "all chemical" as "the Starship option".

My question is whether the SEP version can be made to work at all.  I think it can, but it requires picking a max acceleration that won't snap off your solar array masts and then figuring out how bad the non-impulsive losses are.

One of the biggest weirdnesses in the current doc (and also in DRA v5.0 back in 2008) is a strong aversion to using aerocapture for arrival into LMO.  I suspect that there are two main reasons for this:

1) It's a bit of an unknown, and NASA doesn't like predicating multi-billion-dollar architectures on things they're not sure are going to work.

2) It's a non-starter for the TransHab, which appears to be somebody's pet project (or  likely to be built by somebody's pet campaign contributor).

I expect Starship to be able to bulletproof aerocapture long before the final architectural decisions would have to be made.  It's a no-brainer in terms of pre-positioning all the supplies needed prior to a crewed mission.  But we may easily wind up in an Artemis-like situation where we all have to roll our eyes about how dumb and expensive the crew transport architecture is, while expecting Starship to eat that portion of the architecture once it's been proven to be as safe as the dumb architecture, at a fraction of the cost.

To 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.

[Dalhousie]

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.

There is need for planetary protection to go out of the window, it's objectives will just be reframed.  This is already in process.

[Zed_Noir]

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.

There is need for planetary protection to go out of the window, it's objectives will just be reframed.  This is already in process.

Think you are missing a "no" as in "There is no need for planetary protection to go out of the window,...".

And doesn't matter how they reframed the Mars planetary protection protocols. The survival and the safe return of the crew will likely override the protocols. For US crewed Mars surface missions. No POTUS will place the protection protocols over the survival of the crew. As the POTUS is the final arbitrator for this issue.

[TheRadicalModerate]

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.

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.

I'd like to stay away from planetary protection as much as possible, because it's always a turd in the punchbowl on any thread where it's discussed.  That said, if you're a NASA planner and you think that the Category IV modifications needed for human missions will be as restrictive as possible, then propulsive capture is less likely to result in a crash that could spread bits of dead humans and their bacterial hangers-on over a big ellipse on the martian surface.

Same argument for a Category V return to Earth.

I bring this up only as a possible explanation for why the architecture is the way it is, not as an invitation to a food fight.  Yes, everybody has an opinion on this.  Not here, unless it's relevant to the Moon to Mars Architecture, OK?

[Twark_Main]

2) Chemical + SEP:  Severely thrust-limited around perigee

This assumes solar panel deployment prior to TMI.

The easy answer to all of this is always going to be, "Just use a friggin' Starship and have done with it."

Fully agreed, along with the rest of your comments.

To 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.

Doctor, it hurts when I do this! 

As a wise man once said, "Just use a friggin' Starship and have done with it."

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.

The orbital mechanics, you mean? Trivial. This isn't 1600.

3) A true HEEO, which has to be carefully engineered to avoid lunar influence,

That's weird. How are you defining "true" HEEO? If it's too high, this is just another example of DIHWIDT.

Of course if you're very clever, you design your HEEO to exploit those lunar influences for better performance. 

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.

Lunar teleoperation is far easier from Earth. The three second delay isn't worth doing it from space.

[spacenut]

Starship could be used to build a giant nuclear powered reusable mother ship that could take a lot of cargo and people to Mars.  Maybe even have a rotating section for artificial gravity.  You still need a large reusable lander to set up a base and supply it.  Flags and footprints don't really get it. 

Or, like SpaceX want's to do send 100's or 1,000's of ships to Mars using only Starship variants.  Musk opted this route to avoid long delays for nuclear powered spaceships and development, and to keep things simple with a one size fits all approach due to cost. 

[Paul451]

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

[Summarised your comment to focus on what I'm responding to. I don't think I changed your intended meaning. Feel free to yell at me if I did.]

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?

Other than "holding everything in one place during the trip to Mars" which doesn't seem especially necessary or useful to me. (For eg, you don't even get an advantage of being able to transport larger cargo/equipment pieces to Mars on the nuclear ship, since they have to be ferried between Earth and orbit, and orbit and Mars, in Starship sized chunks anyway.)

[Zed_Noir]

<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>

You are forgetting that the US Congressional critters could use a large in space nuclear thermal transport development program in the same way as the SLS. As a pork trough for many Congressional districts. Which the few Starship production sites at CA, FL & TX will not provided. 

[spacenut]

Building a large nuke powered in Space transporter with a rotating gravity ring attached could in the distant future allow travel to Ceres or the moons of Jupiter and Saturn.  It could start out by transporting tons of equipment to Mars and use Martian Starships to ferry this to Mars surface.  The Starships could refuel on Mars for ferry duties.  Same as on earth. 

I'm talking about very large that could be built in LEO using Starship earth to LEO ferries. 

Something this large would require, like someone said, and SLS type multi-year development that would keep congress happy with pork built in their districts. 

Starships would only be just the beginning, they would be relegated to truck duties in the long run. 

However, what NASA is proposing is just a flags and footprints type mission, even with nuclear propulsion. 

[Todd Martin]

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.

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

That seems wise of her.

It also seems wise that we concentrate more on early Mars missions here than turning it into yet another "Mars Colony" thread.  This short-stay vs. long-stay issue is a big fat hairy deal.  It's ironic that short-stay is profoundly enabled by Starship's ability to fling propellant at the problem, but that Starship also greatly increases the ability to have a bulletproofed long-stay architecture.

Looking at the Conops presented, I noticed that Orion with its service module is proposed to be taken along with the crew to Mars.  To me, that seems like roughly 5 metric tons of unneeded mass for that portion of the crew trip which slows down the transit time.  I would suggest that one Orion deliver the crew to the Mars Transfer Vehicle and is autonomously returned to Gateway.  A second Orion would be pre-delivered to Mars orbit.  Ideally, that pre-positioned Orion would dock to an orbiting station that could serve as an emergency habitat or staging area, like Gateway.

[Paul451]

Todd, TheRadicalModerate, and yg1968,

Edit your quotes to just the part you are replying to. It's annoying for others to have to scroll unnecessary pages of text.

A second Orion would be pre-delivered to Mars orbit.  Ideally, that pre-positioned Orion would dock to an orbiting station that could serve as an emergency habitat or staging area, like Gateway.

Orion isn't used at Mars. It can't land people on Mars, because there's no way to launch them back to orbit. The normal Mars architecture requires a whole extra Mars lander.

If you aren't taking Orion with you, you don't need to send one to Mars.

[Paul451]

[Starship] is also capable of doing the same job as the nuclear ship anyway.
So what does the nuclear ship actual add that Starship isn't already going to do?

You are forgetting that the US Congressional critters could use a large in space nuclear thermal transport development program in the same way as the SLS. As a pork trough for many Congressional districts. Which the few Starship production sites at CA, FL & TX will not provided.

Forgive me for not seeing "it will make stupid, corrupt people happy" as a good reason.

[Todd Martin]

Paul, the Conops proposed by NASA which we are discussing has Orion first taking crew to the Mars transfer vehicle, then this combined stack goes to Mars.  A separate part of that stack is a Mars lander.  After the Mars surface mission is concluded, the MTV and Orion journey back to earth and the crew uses Orion to land on earth without needing to first enter Earth orbit for rendevous with an EDL craft (Earth Descent and Landing).  What I was proposing is having an Orion pre-positioned in Mars orbit to reduce crew trip time (you can select a faster trajectory with less mass).

A second Orion would be pre-delivered to Mars orbit.  Ideally, that pre-positioned Orion would dock to an orbiting station that could serve as an emergency habitat or staging area, like Gateway.

Orion isn't used at Mars. It can't land people on Mars, because there's no way to launch them back to orbit. The normal Mars architecture requires a whole extra Mars lander.

If you aren't taking Orion with you, you don't need to send one to Mars.
[/quote]

[Paul451]

Paul, the Conops proposed by NASA which we are discussing has Orion first taking crew to the Mars transfer vehicle, then this combined stack goes to Mars.  A separate part of that stack is a Mars lander.  After the Mars surface mission is concluded, the MTV and Orion journey back to earth and the crew uses Orion to land on earth without needing to first enter Earth orbit for rendevous with an EDL craft (Earth Descent and Landing).  What I was proposing is having an Orion pre-positioned in Mars orbit to reduce crew trip time (you can select a faster trajectory with less mass).

Apologies. I assumed you'd misunderstood the reason for taking Orion with the MTV.

However, your alternative still won't provide the advantage you believe:

In order for the Orion to serve its role upon Earth-return, it needs to be able docked with the MTV during the return. Therefore the MTV has to be able to propel its mass along with Orion, from Mars to Earth.

You are only suggesting, therefore, to send Orion separately on the Earth-to-Mars leg. But that requires having another dedicated vehicle for just that leg (SLS isn't good enough to put Orion into MTI, the Orion service module isn't good enough to capture into Mars orbit). Inevitably, IMO, the added cost/propellant/engine-sizing to allow the MTV+Orion to travel to Mars together will be the same or less than the cost/etc of the MTV + other vehicle separately. The MTV has to already be able to do the job in order to allow the Earth-return leg, so you aren't saving anything by splitting the task for the Earth-to-Mars leg.

[Paul451]

Building a large nuke powered in Space transporter with a rotating gravity ring attached could in the distant future allow travel to Ceres or the moons of Jupiter and Saturn.  It could start out by transporting tons of equipment to Mars and use Martian Starships to ferry this to Mars surface.  The Starships could refuel on Mars for ferry duties.  Same as on earth. 
I'm talking about very large that could be built in LEO using Starship earth to LEO ferries.

It seems you are picturing "very large" and thinking it offers some added benefit simply due to its scale.

However:
- A large NTR-propelled ship doesn't enable anything more than its individual components enable.
- Moving those components around the solar system as a single mass is not inherently more enabling than moving them separately.
- The components have to be Starship-launch sized.
- Starship is capable of moving the components around the solar system separately for a lower price than a large NTR-propelled ship.

Therefore:
Anything a large NTR-propelled ship could do (whether it's ferrying supplies to a major Mars base, or exploring Ceres) can be done cheaper and easier with a bunch of Starships.

If you want to go bigger than Starship, for eg, because the components need to be bigger, then you'll also need a bigger launcher to get those bigger components off Earth (and possibly also down to their destination). But now you've developed a bigger, better super-Starship, and the same reasoning applies to moving those bigger components around the solar system: A bunch of super-Starships is able to do anything that a super-NTR is capable of. The super-NTR remains unnecessary.

This only changes when you are no longer supplying most things from Earth. Where the bulk of transport around the solar system is people/material/equipment that originated off-Earth. At that point, large nuclear ships (not capable of atmospheric entry) might start to make sense for some uses, but that's a long way off and not part of the discussion of the "Moon-to-Mars-Architecture".

Similarly, beyond Jupiter, nuclear makes sense (although only as NEP, not NTR.)

But even then, the non-atmospheric ships might still not tend to be bigger than the individual size of the components. "Big" still might not make sense.

I think the "bigger is more efficient" assumption comes from living in an environment with constant drag (road/rail/air/oceans). Orbital mechanics doesn't follow the same rules, so you have to be very careful that you aren't applying assumptions that don't apply in space.


Forgetting "size" for a moment:

The only advantage of NTRs in general is a slightly high Isp than chemical. Which should be enough of a justification on its own. But when you drill into the real-world details, NTRs have such low thrust/weight and add such increased mission complexity, that in practice they don't really offer any benefits over chemical rockets.

...Unless launch is very expensive.

And the whole point of saying "Use Starship to build a big NTR ship" is assuming that Starship is cheap.

The user deltaV gave a perfect example in the Artemis Program Updates thread:

NASA's Mars DRM 5 has nuclear thermal taking 9 Ares Vs vs. chemical taking 12 Ares Vs: https://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf tables 4.1 and 4.2. If you replace expendable Ares V with reusable Starship or New Glenn those 3 extra launches cost a negligible amount compared to the cost of a nuclear thermal program.

[TheRadicalModerate]

Paul, the Conops proposed by NASA which we are discussing has Orion first taking crew to the Mars transfer vehicle, then this combined stack goes to Mars.  A separate part of that stack is a Mars lander.  After the Mars surface mission is concluded, the MTV and Orion journey back to earth and the crew uses Orion to land on earth without needing to first enter Earth orbit for rendevous with an EDL craft (Earth Descent and Landing).  What I was proposing is having an Orion pre-positioned in Mars orbit to reduce crew trip time (you can select a faster trajectory with less mass).

A second Orion would be pre-delivered to Mars orbit.  Ideally, that pre-positioned Orion would dock to an orbiting station that could serve as an emergency habitat or staging area, like Gateway.

Orion isn't used at Mars. It can't land people on Mars, because there's no way to launch them back to orbit. The normal Mars architecture requires a whole extra Mars lander.

If you aren't taking Orion with you, you don't need to send one to Mars.

Stupid, two-part question:

1) Can the Orion CM manage without the ESM if it's hooked up to external power and thermal?

2) How long can the CM support a crew once it's jettisoned the ESM?

All you need the Orion for is to do EDL for the crew in a way that doesn't cost even more capture delta-v, and breaks the chain of contact so that the general public doesn't freak out about Category V Germs From Mars.  As long as you can keep your DST's probability of hitting Earth sufficiently low to satisfy Cat V, you can get really close before cutting the CM loose.

Then the Orion adds less than 11t to the whole DST.

[TheRadicalModerate]

Therefore:
Anything a large NTR-propelled ship could do (whether it's ferrying supplies to a major Mars base, or exploring Ceres) can be done cheaper and easier with a bunch of Starships.

There is a case for NTP other than "move a lot of stuff".  If you have a conops that requires a large amount of delta-v with no ability to refuel, then NTP helps substantially.

NTP doesn't change the fact that things go to hell in a handbasket when mass ratios get much above 6.  But if you're multiplying ln(6) by an Isp that's twice as big as anything chemical, you still get double the delta-v.

This is where short-stay + aerocapture phobia + no refueling starts to make NTP look like a pretty good deal.

That said:

1) I believe that short-stay is an important abort option, but a silly nominal option.

2) The aerocaptophobes need to get over themselves.

3) Even if you don't like the idea of robots mining water, give a robot a tank of LH2 in the synod before you go, and it'll happily turn it into as much methalox as you want.

So it's not that NTP itself is stupid, but the requirements that lead to needing NTP in the first place are stupid.

[Paul451]

This is where short-stay + aerocapture phobia + no refueling starts to make NTP look like a pretty good deal.
[...]
So it's not that NTP itself is stupid, but the requirements that lead to needing NTP in the first place are stupid.

As noted above, even the short stay, non-aerocapture, non-ISRU mission, the chemical-only version required just three more launches than the NTR version. It's still not worth the cost of developing an NTR.

I suspect the same holds true anywhere inside of Jupiter's orbit, at which point NEP so completely outperforms NTR than the latter remains not worth developing.

[TheRadicalModerate]

This is where short-stay + aerocapture phobia + no refueling starts to make NTP look like a pretty good deal.
[...]
So it's not that NTP itself is stupid, but the requirements that lead to needing NTP in the first place are stupid.

As noted above, even the short stay, non-aerocapture, non-ISRU mission, the chemical-only version required just three more launches than the NTR version. It's still not worth the cost of developing an NTR.

I suspect the same holds true anywhere inside of Jupiter's orbit, at which point NEP so completely outperforms NTR than the latter remains not worth developing.

The chemical version in Table 4.2 assumes Mars aerocapture.  If it didn't, it'd be horrific.

[TheRadicalModerate]

A hybrid chemical/NTP option is interesting.  If the NTP can inject the chemical stack into a 2:1 resonant orbit, then cut itself free, it'll wind up back at Earth in two years, with only its own dry mass to capture propulsively back into Earth orbit, where it could be used for the next synod's mission.

The remainder of the stack would have to do some chemical deceleration to be able to do a non-insane aerocapture, but it'd be less than it would have had to provide to do the TMI in the first place.  From there, the conops would be almost the same as the all-chemical conops in the DRM.

This also has the nice property of a short-ish outbound transit time (~130days).  Not only is that easier on the crew, it gives a wider window in which to decide whether to do a full-synod long stay or do the short stay.  And of course the 2:1 orbit allows the crew to do a free return.

[Robotbeat]

It’s a logistics issue. And therefore a cost issue. No mention of NTR for Mars missions should be divorced from a cost analysis using commercial launch capacity like is being used for Artemis.

The benefit of NTR is in reducing launch costs for a given mission delta-v. And commercial launch for Artemis should be calculated as low as $1000/kg IMLEO and possibly lower by the time the mission would occur. From multiple providers, like with Artemis.

A reduction of IMLEO from 2000t to 1500t saves you $500 million. Can the bunch of NTR stages buy their way on at those prices?

Any mission you imagine for NTR can be done with chemical (including a 130 day transfer). The exponential rocket equation may make the chemical one absurdly high mass, but you still need to calculate whether that’s actually making it more expensive or not.

[JohnFornaro]

Well, there is a planetary protection food fight in the offing.  At some point, we have to say it is a dead planet.

Or not.

[Paul451]

At some point, we have to say it is a dead planet.

First we'd have to look.

[Mars scientists frustrate me. They know there's a ticking clock, but they refuse to act like it. They're still acting like they have unlimited time and giving greater priority to things that won't be affected by (or be helped by) a human presence.]

[Slarty1080]

Well, there is a planetary protection food fight in the offing.  At some point, we have to say it is a dead planet.

Or not.

Or perhaps there will be a planetary protection fudge factor: the surface is dead, but maybe there's life deeper underground and it would be easier to send a crew to look for that.

[Mr. Scott]

Well, there is a planetary protection food fight in the offing.  At some point, we have to say it is a dead planet.

Or not.

Or perhaps there will be a planetary protection fudge factor: the surface is dead, but maybe there's life deeper underground and it would be easier to send a crew to look for that.

No it’s not dead…. it’s just pining.

[Slarty1080]

Well, there is a planetary protection food fight in the offing.  At some point, we have to say it is a dead planet.

Or not.

Or perhaps there will be a planetary protection fudge factor: the surface is dead, but maybe there's life deeper underground and it would be easier to send a crew to look for that.

No it’s not dead…. it’s just pining.

No! It's shed it's mortal coil and gone to join the choir invisible...

[Zed_Noir]

At some point, we have to say it is a dead planet.

First we'd have to look.

[Mars scientists frustrate me. They know there's a ticking clock, but they refuse to act like it. They're still acting like they have unlimited time and giving greater priority to things that won't be affected by (or be helped by) a human presence.]

When the clock runs out. The scientists' plans and exclusive access to Mars will be push aside to enhanced the survival and return of crew on Mars. When the first wave of Mars bound Starships with crew leaves Earth orbit.

[Robotbeat]

At some point, we have to say it is a dead planet.

First we'd have to look.

[Mars scientists frustrate me. They know there's a ticking clock, but they refuse to act like it. They're still acting like they have unlimited time and giving greater priority to things that won't be affected by (or be helped by) a human presence.]

When the clock runs out. The scientists' plans and exclusive access to Mars will be push aside to enhanced the survival and return of crew on Mars. When the first wave of Mars bound Starships with crew leaves Earth orbit.

Yeah, there's gonna need to be more compromise, and the most extreme viewpoint on it will not prevail, but it is, of course, in NASA's and SpaceX's interest that good science gets done on Mars.

Even when you get to a city or whatever, etc, they're going to have an interest in making sure good science gets done as that is one of the most important revenue streams for a nascent Mars city.

[Todd Martin]

A quick look at UV (ultraviolet) radiation on Mars per Ames Research Center:  "On present day Mars, the total integrated UV flux over 200-400 nm, is comparable to the Earth’s. However, on Mars the shorter wavelengths contribute a much greater proportion of this UV flux. These wavelength ranges, such as UVC (200-280 nm) and UVB (280-315nm) are particularly biologically damaging.
Dust, if present, contributes substantially to attenuating the UV flux reaching the surface."  In other words, Mars surface as far as I can tell is largely self-sterilizing.  The idea that Earth bacteria are going to propagate across a planet from one (or a few) outposts over a larger land mass than Earth and destroy or contaminate all possible underground reservoirs of Martian bacteria within several human lifetimes is NOT plausible. 

[Paul451]

A quick look at UV (ultraviolet) radiation on Mars per Ames Research Center:  "On present day Mars, the total integrated UV flux over 200-400 nm, is comparable to the Earth’s. However, on Mars the shorter wavelengths contribute a much greater proportion of this UV flux. These wavelength ranges, such as UVC (200-280 nm) and UVB (280-315nm) are particularly biologically damaging.
Dust, if present, contributes substantially to attenuating the UV flux reaching the surface."  In other words, Mars surface as far as I can tell is largely self-sterilizing.  The idea that Earth bacteria are going to propagate across a planet from one (or a few) outposts over a larger land mass than Earth and destroy or contaminate all possible underground reservoirs of Martian bacteria within several human lifetimes is NOT plausible.

OTOH: If it were that easy to truly, deeply sterilise a random surface against Earth life (just a bit of far-UV), it wouldn't be so expensive and difficult to sterilise Mars landers/rovers to the highest planetary-protection levels, and it would be done on every Mars mission (allowing them to target any location.) Instead, they struggle to reach adequate levels of sterilisation affordably (on multi-billion dollar programs), such that they typically stick to lower levels of PP and limit which sites they are allowed to visit.

[CuddlyRocket]

The idea that Earth bacteria are going to propagate across a planet from one (or a few) outposts over a larger land mass than Earth and destroy or contaminate all possible underground reservoirs of Martian bacteria within several human lifetimes is NOT plausible. 

No, that would take millions of years at a minimum.

I would be astonished if we found Martian 'bacteria', as bacteria are a specific kind of unicellular organism found on Earth readily distinguishable from other unicellular organisms such as archaea, protozoa, algae and others. If we find a bacteria on Mars it would likely (discounting panspermia) be contamination from humans or their equipment, which we could probably identify from its DNA.

[Paul451]

bacteria are a specific kind of unicellular organism ...

When most non-biologists say "bacteria", they just mean "simple, probably single celled, organsims" and aren't being specific about the details; as distinct from complex, multicellular life, like jellyfish and squirrels.

Don't read any more into it than that.

[Saying "virus" otoh, for alien life, you can ridicule mercilessly.]

[Paul451]

The idea that Earth bacteria are going to propagate across a planet from one (or a few) outposts over a larger land mass than Earth and destroy or contaminate all possible underground reservoirs of Martian bacteria within several human lifetimes is NOT plausible.

For me, it's not about Earth-life instantly contaminating the entire planet, it's having it expanding fast enough ahead of human exploration that any site we sample might have been contaminated by the time we sample it. It's the added ambiguity about a unique, revolutionary discovery. Extraordinary claims require extraordinary evidence, and "alien life" is the extraordinary claim. If we prevent ourselves from being able to establish extraordinary levels of proof, we make the discovery harder or even impossible.

And we don't know. That's the problem. We haven't discovered alien life before. If we had prior examples (say from asteroids and/or comets) it would narrow down the required evidence for life-on-Mars.

For example, whenever we discover Earth-life in novel places on Earth (deep underground), or try to prove isolation over time (lakes-under-ice), it is always difficult for the discoverers to genuinely rule out contemporary contamination to a level required for the novelty of the claim. With "alien life", given the uniquely extraordinary nature of the claim, the standard of evidence required, and the controversy of the discovery, is going to be insane.

In theory, you could insist that every human base and work-site operates at the highest PP levels. Realistically, however, that's just not going to happen. It would make establishing even a single flags'n'footprints mission impossible in practice. So, pragmatically, once there's a human presence on Mars, contamination becomes the highest probability explanation for any novel discovery.

Reasoning: We know Earth-life exists (duh), we know it can survive in weird environments, we know we've (by then) put Earth-life on Mars, the conditions on Mars will filter out the bulk of Earth life leaving just the weirdest types, we don't know if alien life exists at all, if it does exist we don't know how similar/different it will be to the weirdest Earth-life, therefore "weird-Earth-life" is a vastly higher probable explanation for any "weird-life" discovery on Mars.

Even today, with a purely robotic mission to a site that's never been visited before, the possibility of cross-contamination from Earth, brought in on the robot itself, is still going to be the highest probability explanation. It's already hard. Human presence will make it vastly harder.

That's what's frustrating about the lack of "life discovery" missions since Viking. Every synod is two years we lose from being able to make a clear discovery. That doesn't apply to geology, aquifers, magnetism, the history of Mars, etc, the evidence for those will still be there a century after humans arrive. Only life-discovery has a ticking clock.

Hence, IMO, every mission to Mars, every synod, should be trying to eliminate (or confirm) the possibility of existing Mars life. Not past life, not "follow the water". Existing life. Starting with the lowest hanging fruit, that Mars life is similar to Earth life (for eg, via some panspermia mechanism). The more "alien" Mars life is, the harder it will be to discover, but the easier it will be to prove it is alien; so it is better to start with the easiest to discover and hardest to prove possibility: Earth-like-life.

Eventually you reach to point where, if Martian life exists, it's so different from Earth-life (so alien) that it doesn't matter as much if we contaminate a site with Earth-life; if a discovery looks like Earth-life, it's not alien.

This is true of every unique place in the solar system. Such as Europa. Whereas for things like comets, they're so common that if you get a novel discovery of life and can't rule out contamination from Earth, you can treat that whole comet as contaminated and merely go find another one that isn't and design the mission to look for that one specific life-signature while maintaining higher standards of PP. (Easier to confirm or refute a known result than to look for "anything new".)

[CuddlyRocket]

bacteria are a specific kind of unicellular organism ...

When most non-biologists say "bacteria", they just mean "simple, probably single celled, organsims" and aren't being specific about the details; as distinct from complex, multicellular life, like jellyfish and squirrels.

Don't read any more into it than that. ...

They do. And generally that's fine. But, if you're going to be discussing the search for Martian life and whether or not you can establish an 'independent genesis' etc then people need to be more precise with their terms. Because it matters. There'll be an entirely different reaction to announcements of the discovery on Mars of a unicellular organism that resembles one of the types that exists on Earth or a unicellular organism that's different to them.

But, in either case I think it will impossible to prove or disprove a second genesis. You could discover a novel lifeform on Mars. If so, you can scientifically examine a novel life form whether or not it's a second genesis. You can make panspermia more unlikely, but not entirely so (and if you really want to make it unlikely, try Enceladus). I worry (occasionally) that people will want to place onerous restrictions and conditions on Martian exploration in an almost certainly vain attempt to prove or disprove a second genesis.

[Paul451]

people need to be more precise with their terms.

There's a difference between asking people to be precise, and replying as if they'd used the narrow meaning, deliberately misinterpreting what they are saying. One is mere pedantry, the other is strawmanning.

[Todd Martin]

The idea that Earth bacteria are going to propagate across a planet from one (or a few) outposts over a larger land mass than Earth and destroy or contaminate all possible underground reservoirs of Martian bacteria within several human lifetimes is NOT plausible.

For me, it's not about Earth-life instantly contaminating the entire planet, it's having it expanding fast enough ahead of human exploration that any site we sample might have been contaminated by the time we sample it. It's the added ambiguity about a unique, revolutionary discovery. Extraordinary claims require extraordinary evidence, and "alien life" is the extraordinary claim. If we prevent ourselves from being able to establish extraordinary levels of proof, we make the discovery harder or even impossible.

-snip-

Thanks Paul for elaborating, and I can see why you feel that way.  It is kind of like archeology where the context of the find may be considered as important the item itself.  That is basic research.  The fear of contamination has been, IMHO, obstructing the search for life on Mars.  Just look at how Curiosity & Perserverence were placed deliberately where no life is expected to be.  I do not see a path forward for planetary scientists to prove Martian originated life while following extreme planetary protection protocols.  Such missions are not being conducted or funded.  Instead, we get geology science. 

On the other hand, weird organisms can have applied science potential regardless of their origination.  When considering mission planning, there is ROI on returning biological specimens even if there was contamination. 

NASA's Moon to Mars architecture will depend on putting down pre-positioned assets on the ground.    There will be a desire to avoid possible areas of Martian life, which mostly means places with water.  There will also be a desire to conduct ISRU which mostly means placing these assets adjacent to water.  This conflict can be disruptive to planning, funding, and schedule.  I suggest collaboration where planetary scientists embrace collecting specimens with reduced planetary protection guidelines alongside ISRU would be a positive and synergistic step that can accelerate planning, funding, and schedule.

[yg1968]

See below:

NASA Shares Newest Results of Moon to Mars Architecture Concept Review:
https://www.nasa.gov/news-release/nasa-shares-newest-results-of-moon-to-mars-architecture-concept-review/

https://www.nasa.gov/wp-content/uploads/2024/01/rev-a-acr23-esdmd-001-m2madd.pdf?emrc=65b03e56936bf

[deltaV]

https://www.nasa.gov/wp-content/uploads/2024/01/rev-a-acr23-esdmd-001-m2madd.pdf?emrc=65b03e56936bf

1. Page 216 mentions that NASA's current Mars plans don't use ISRU.

2. Figure 3-20 on page 217 mentions 30 sols on Mars surface for both opposition class (i.e. short stay) and conjunction class (i.e. long stay) missions. For conjunction class missions the plan seems to be to spend up to a year in Mars orbit waiting for the planets to align. NASA seems to be treating time on Mars surface as something to be avoided because it increases landed mass requirements rather than as something desirable since it's hard to accomplish anything without it.

3. I fear that NASA may choose requirements for future NASA Mars missions that force their contractors to use NASA's preferred architecture. A 30 day surface stay is incompatible with SpaceX's Mars colonization plans so this would force SpaceX to develop two different Mars systems, one for their plans and one for NASA. Not being able to share costs as effectively with SpaceX's Mars plans could easily raise the cost to NASA beyond NASA's human spaceflight budget.

4. To get the best chance of affording Mars missions NASA needs to give contractors maximum flexibility to choose architectures. This flexibility should include opposition or conjunction class, ISRU or not, NTP, NEP, SEP, and/or chemical propulsion, and whether people are left in Mars orbit. It's good that NASA is studying possible architectures, they just need to avoid choosing an architecture until evaluating contractor bids.

5. I would actually include yet another piece of flexibility: let contractors submit up to 2 proposals, one for missions to the Martian moons and the other for missions to Mars surface. SpaceX may provide a better bid for Mars surface since that's where they want to go but others such as Blue Origin would likely offer lower prices for Martian Moons missions since it eliminates the need for lander, ascent vehicle, surface hardware, and (some) planetary protection.

[sdsds]

From page 225: "When we go" column crossing all reference missions:

2039 crew departure to meet "by 2040" boots on Mars

[Lampyridae]

From page 225: "When we go" column crossing all reference missions:

2039 crew departure to meet "by 2040" boots on Mars

I remember in the 90s when Mars was "by 2020 2030", ie 24 years in the future. Now Mars is 16 years away. At this rate, we will have NASA boots on Mars by 2084. Actually, since the proposal has shrunk from 6 people to 2, that means there will be 2/9 of a person on Mars, so that person may or may not have even a single boot.

https://www.nasa.gov/wp-content/uploads/2024/01/rev-a-acr23-esdmd-001-m2madd.pdf?emrc=65b03e56936bf

1. Page 216 mentions that NASA's current Mars plans don't use ISRU.

True, but it's also there as a placeholder to "bound the trade space":

To bound the trade space, recent analysis has focused on a minimal two-crew MAV
concept that relies on Earth-delivered ascent propellant, but more complex options capable of
ferrying larger crew complements using ISRU propellants have been studied and will be revisited
for later sustained exploration missions as the Mars Architecture evolves. Details of these
concepts are provided in subsequent sections of this document.

Seems like they're building up the Mars architecture from a position of minimal technological risk, because ISRU is mentioned extensively elsewhere in the lunar objectives.

[Twark_Main]

"To bound the trade space" = "to not freak out Congress just yet"   

[Yggdrasill]

3. I fear that NASA may choose requirements for future NASA Mars missions that force their contractors to use NASA's preferred architecture. A 30 day surface stay is incompatible with SpaceX's Mars colonization plans so this would force SpaceX to develop two different Mars systems, one for their plans and one for NASA. Not being able to share costs as effectively with SpaceX's Mars plans could easily raise the cost to NASA beyond NASA's human spaceflight budget.

I'm pretty sure SpaceX would offer Starship for whatever element it would be suitable for, and if Starship doesn't get them the contract, that's okay. I don't see them spending the time and effort to make a system they don't need themselves.

This is the same thing as HLS Starship. They offered Starship and if that hadn't been good enough for NASA, they'd just have focused on their own projects and other customers.

[DanClemmensen]

3. I fear that NASA may choose requirements for future NASA Mars missions that force their contractors to use NASA's preferred architecture. A 30 day surface stay is incompatible with SpaceX's Mars colonization plans so this would force SpaceX to develop two different Mars systems, one for their plans and one for NASA. Not being able to share costs as effectively with SpaceX's Mars plans could easily raise the cost to NASA beyond NASA's human spaceflight budget.

I'm pretty sure SpaceX would offer Starship for whatever element it would be suitable for, and if Starship doesn't get them the contract, that's okay. I don't see them spending the time and effort to make a system they don't need themselves.

This is the same thing as HLS Starship. They offered Starship and if that hadn't been good enough for NASA, they'd just have focused on their own projects and other customers.

We cannot know for sure, but it appears that their HLS bid was high enough to cover the incremental costs of the HLS development plus a nice little profit, without attempting to load it with any of the generic non-HLS Starship development.  I think we can expect them to do the same for any strange Mars requirements that are not congruent with SpaceX' Mars architecture.

As with HLS the incremental cost of a NASA-Mars Starship variant will almost certainly be much cheaper and much more capable than any competing approach that requires development of a whole new architecture.

With HLS, NASA discovered that writing requirements based on a reference architecture does not necessarily result in proposals based on that architecture. The BO/"national team" HLS was a fairly faithful implementation of the NASA reference architecture, for $6B. It met but did not much exceed the requirements. SpaceX bid $3B with Starship HLS and massively exceeded the requirements.

[sdsds]

[...]For conjunction class missions the plan seems to be to spend up to a year in Mars orbit waiting for the planets to align. NASA seems to be treating time on Mars surface as something to be avoided because it increases landed mass requirements [...]

3. I fear that NASA may choose requirements for future NASA Mars missions that force their contractors to use NASA's preferred architecture. [...]

Hopefully either through the NextSTEP-2 process or some similar mechanism NASA will seek broadly for industry solutions to the "landed mass" requirement. Once a commercial provider can credibly offer literally tons of pre-positioned supplies on the surface of Mars, full duration conjunction class stays on the surface will become the preferred plan.

(And when the settlers can offer accommodation to the NASA guests, perhaps including hot tub soaking baths and cozy king-sized beds, the preferred plan will again be different.  )

[Zed_Noir]

<snip>
(And when the settlers can offer accommodation to the NASA guests, perhaps including hot tub soaking baths and cozy king-sized beds, the preferred plan will again be different.  )

Only after the NASA guests pass through some sort of passport ticket control to get their passport stamped tickets validated.