Human Exploration of Mars Design Reference Architecture 5.0

[rdale]

    This document reviews the Design Reference Architecture (DRA) for human exploration of Mars. The DRA represents the current best strategy for human missions. The DRA is not a formal plan, but provides a vision and context to tie current systems and technology developments to potential missions to Mars, and it also serves as a benchmark against which alternative architectures can be measured. The document also reviews the objectives and products of the 2007 study that was to update NASA's human Mars mission reference architecture, assess strategic linkages between lunar and Mars strategies, develop an understanding of methods for reducing cost/risk of human missions through investment in research, technology development and synergy with other exploration plans. There is also a review of the process by which the DRA will continue to be refined. The unique capacities of human exploration is reviewed. The possible goals and objectives of the first three human missions are presented, along with the recommendation that the mission involve a long stay visiting multiple sites.The deployment strategy is outlined and diagrammed including the pre-deployment of the many of the material requirements, and a six crew travel to Mars on a six month trajectory. The predeployment and the Orion crew vehicle are shown. The ground operations requirements are also explained. Also the use of resources found on the surface of Mars is postulated. The Mars surface exploration strategy is reviewed, including the planetary protection processes that are planned. Finally a listing of the key decisions and tenets is posed.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090012109_2009010520.pdf

[Kaputnik]

Thanks for that, very interesting indeed.
A few points though:
- aerocapture for the DAV- why not direct entry?
- DAV seems rather heavy- this may be because it only uses partial ISRU- is CH4 generation seen as too risky?
- I've never been a huge fan of NTR. The benefit over conventional cryo propulsion isn't anything astonishing, when you factor in much lower thrust/weight ratio of the stages. The political barriers remain significant too.
- Drop tank TMI stage seems a bit crude. I wouldn't be surprised if it worked out better to just keep the tank in place, which saves you a rather heavy-looking semi-cylindrical truss structure.

[kfsorensen]

JSC can't seem to give up on NTR.  Too bad.  That alone will sink any hope of this mission ever happening.

[kraisee]

If you can deploy Low Boiloff technology and Cryogenic Propellant Transfer technologies, you don't need any form of nuclear propulsion.

Which is cheaper?   Which is more realistic?   And which would offer benefits beyond just a human mission to Mars?

That isn't to say that I don't ever want to see a nuclear space engine.   I most definitely do.    But I think it would be crazy to include it on the critical path for any human exploration missions.

Ross.

[mike robel]

I still wonder about what my friend Guenter Wendt says about Mars Missions, which is that the crew will be dead within 7 days due to radiation....

[A_M_Swallow]

{snip}
- I've never been a huge fan of NTR. The benefit over conventional cryo propulsion isn't anything astonishing, when you factor in much lower thrust/weight ratio of the stages. The political barriers remain significant too.

Mars is still within the area that STR (Solar Thermal) motors work.  Solar Thermal Propulsion can also be used to the Moon, Asteroids, GEO and inner planets.  The high temperature chamber technology can probably be transferred.

[Jorge]

I still wonder about what my friend Guenter Wendt says about Mars Missions, which is that the crew will be dead within 7 days due to radiation....

Hate to say it, but he was speaking out his ass.

A crew traveling to Mars would get less radiation exposure during their first 7 days than the Apollo crews got during their entire missions. This is because the Mars crew would only get one exposure to the Van Allen belts while the Apollo crews got two.

If Wendt was right, none of the Apollo crews should have survived their missions.

[mike robel]

I still wonder about what my friend Guenter Wendt says about Mars Missions, which is that the crew will be dead within 7 days due to radiation....

Hate to say it, but he was speaking out his ass.

A crew traveling to Mars would get less radiation exposure during their first 7 days than the Apollo crews got during their entire missions. This is because the Mars crew would only get one exposure to the Van Allen belts while the Apollo crews got two.

If Wendt was right, none of the Apollo crews should have survived their missions.

Well, what bugs me is I can't find any hard data about radiation exposure from probes we have sent to Mars.  Zubrin says , FWIW, that the radiation exposure would only add a slight increase in probability of developing cancer.

So I am have anecdotal data on two extremes and no hard data...

[Jorge]

I still wonder about what my friend Guenter Wendt says about Mars Missions, which is that the crew will be dead within 7 days due to radiation....

Hate to say it, but he was speaking out his ass.

A crew traveling to Mars would get less radiation exposure during their first 7 days than the Apollo crews got during their entire missions. This is because the Mars crew would only get one exposure to the Van Allen belts while the Apollo crews got two.

If Wendt was right, none of the Apollo crews should have survived their missions.

Well, what bugs me is I can't find any hard data about radiation exposure from probes we have sent to Mars.  Zubrin says , FWIW, that the radiation exposure would only add a slight increase in probability of developing cancer.

So I am have anecdotal data on two extremes and no hard data...

"Anecdotal data" is an oxymoron, I'm afraid.

What you have are two anecdotes and no data, and one of the anecdotes (Wendt's) is trivially false. I could excuse him for saying it if he said it before Apollo 8, but it would beg the question of how he could bring himself to strap in the 8 crew if he believed it to be true.

Once you get outside the Van Allen belts, the radiation environment doesn't change much until you get to Mars. Time of exposure then becomes the biggest factor, if the amount of shielding is assumed to be constant.

[kfsorensen]

{snip}
- I've never been a huge fan of NTR. The benefit over conventional cryo propulsion isn't anything astonishing, when you factor in much lower thrust/weight ratio of the stages. The political barriers remain significant too.

Mars is still within the area that STR (Solar Thermal) motors work.  Solar Thermal Propulsion can also be used to the Moon, Asteroids, GEO and inner planets.  The high temperature chamber technology can probably be transferred.

Solar thermal can't provide the high thrust needed to take advantage of the DV reduction that comes about from doing the trans-Mars injection burn deep in the gravity well.  That loss means that whatever Isp advantage of solar thermal is trashed by the nearly doubling of the DV required for trans-mars injection.

[A_M_Swallow]

{snip}
- I've never been a huge fan of NTR. The benefit over conventional cryo propulsion isn't anything astonishing, when you factor in much lower thrust/weight ratio of the stages. The political barriers remain significant too.

Mars is still within the area that STR (Solar Thermal) motors work.  Solar Thermal Propulsion can also be used to the Moon, Asteroids, GEO and inner planets.  The high temperature chamber technology can probably be transferred.

Solar thermal can't provide the high thrust needed to take advantage of the DV reduction that comes about from doing the trans-Mars injection burn deep in the gravity well.  That loss means that whatever Isp advantage of solar thermal is trashed by the nearly doubling of the DV required for trans-mars injection.

Is that low thrust intrinsic to the technology or just that people have only been making small Solar thermal engines?

[yinzer]

{snip}
- I've never been a huge fan of NTR. The benefit over conventional cryo propulsion isn't anything astonishing, when you factor in much lower thrust/weight ratio of the stages. The political barriers remain significant too.

Mars is still within the area that STR (Solar Thermal) motors work.  Solar Thermal Propulsion can also be used to the Moon, Asteroids, GEO and inner planets.  The high temperature chamber technology can probably be transferred.

Solar thermal can't provide the high thrust needed to take advantage of the DV reduction that comes about from doing the trans-Mars injection burn deep in the gravity well.  That loss means that whatever Isp advantage of solar thermal is trashed by the nearly doubling of the DV required for trans-mars injection.

Is that low thrust intrinsic to the technology or just that people have only been making small Solar thermal engines?

Intrinsic to the technology.  A NTR might have 4500 MW thermal power.  Solar flux at the earth's orbit is roughly 1 kW/m^2, so you'd need solar concentrator over 2 km in diameter to capture that much power.  The upper stages in the attached PDF have 3 such engines...

[iamlucky13]

- aerocapture for the DAV- why not direct entry?

First of all, remember this is an early baseline, not a final proposal. I tend to agree with the implications of your other questions.

Regarding the quoted question, for payloads much larger than the MSL, the thin Martian atmosphere makes the required size of heat shield for direct entry generally prohibitive.

[Seer]

Interesting new report.  First thoughts are that they've gone in the other direction to DRM 3.0, which scubbed mass. This plan is DRM 1.0 on steriods.  The aeroshell is massive at 43 tonnes, that's about 40% of aerobraked mass. The Transhab is also huge: it's 40 tonnes, nearly twice as big as the previous one. The orion EERV is more realistic at 10 tonnes, rather than 5 tonnes

Seven Ares V plus nuclear is going to be costly. The mobility options are pretty bold. That Commuter hab looks like something out of Star Wars! 

[Kaputnik]

Maybe it's about justifying the enormous payload capability of Ares-V?
As a side note, if you swallowed the inevitable development costs, could Ares-V be optimised for LEO launches, i.e. cut 40% of the EDS tankage? By my crude calculations you'd get another 10t or more payload.

[PurduesUSAFguy]

I think this is a step backwards from DRM III, too many rendezvous events, too much mass to launch.

[kfsorensen]

I think this is a step backwards from DRM III, too many rendezvous events, too much mass to launch.

I think it's a step backward from the NEP-AG studies that almost became a DRM IV...

For one thing, a 20 MWt NEP reactor is going to be a whole lot easier to develop than a 500 MWt nuclear thermal reactor.  More sustainable too.

Isn't it kind of silly to have a 500 MW nuclear reactor send you to Mars and then fly there on diddly little solar panels?

[yinzer]

I think this is a step backwards from DRM III, too many rendezvous events, too much mass to launch.

I think it's a step backward from the NEP-AG studies that almost became a DRM IV...

For one thing, a 20 MWt NEP reactor is going to be a whole lot easier to develop than a 500 MWt nuclear thermal reactor.  More sustainable too.

Isn't it kind of silly to have a 500 MW nuclear reactor send you to Mars and then fly there on diddly little solar panels?

Maybe.

A NTR needs turbomachinery to pump the hydrogen through the reactor.  I think that 25 klb thrust, 900 second Isp, and 1000 psi pump exit pressure work out to 1MW of mechanical power.  This can be extracted under comparatively benign conditions via an expander cycle - the heat required gets transfered across a huge surface area (tiny metal tubes) between two liquids at a huge temperature differential.  It has to run a few times during the mission, for a few minutes at a time.

A 20 MWe nuclear reactor needs to handle at least 20 MW of mechanical power (using a Rankine cycle) and possibly much more (Brayton).  It has to reject many MW of waste heat via radiation into vacuum.  It has to work continuously for years with no maintenance.

Not clear which is easier, without doing the math.

ISRU using solar panels does get a bit tricky, for sure.

[kraisee]

Maybe it's about justifying the enormous payload capability of Ares-V?

That would be my bet too.

Ross.

[Kaputnik]

It seems to be a case of throwing mass at any problem. Even those that don't really exist. For example, a more comprehensive ISRU plant generating CH4 as well as O2 would allow a significantly lower DAV mass.
The multi-purpose aerodynamic shroud and entry shell could be problematic- it is really heavy, and the TPS is exposed for something like a whole year through launch to entry. The development effort associated with such a design would be immense.
I tend to favour much smaller entry vehicles, even if that means four rather than two to accomplish the mission, because it is less of a scale-up from existing systems and would be much easier to test out.

[William Barton]

Am I correct in reading that the "surface habitat" lander (transfers crew from orbit to ground) lacks a landing abort capability?

[William Barton]

It seems to me that manned exploratory missions to the Moon and Mars come in two natural "flavors," excursions (single lander, up to 2wks Moon, 30da Mars) and expeditions (multiple lander/rover, 30da+ Moon, typically 18mo Mars). This seems like an attempt to create a hybrid between the two that may not be such a good idea. It's tied to a single landing site, like an excursion, but requires a large at-Mars infrastructure, like an expedition.

Mars Direct originally took advantage of the excursion requirements to Mars to tie excursion together into an expedition-equivalent, but could be used in a purely excursionary format, if necessary. That's probably a better idea.

If I were going to plan an expeditionary exploration of Mars, I'd want an orbital manned infrastructure (my personal favorite uses the martian moons, but that's largely due to my science-fictional antecedents), supporting reusable landers to acquire multiple landing sites. In other words, I'd put an expedition in orbit, and run excursion-like missions to the surface. I know reusable Mars manned landers would be difficult to design (I imagine expendable entry shells, possibly inflatable) delivering crews to prepped ISRU/Hab landers, allowing open-ended exploratory landings whose length would depend on the nature of the landing site, and maybe even on what turned up post landing. The "expedition" would keep on receiving new hardware and crew-rotation at each flight opportunity. It's possible that surface exploration crew members would stay at Mars (some time on the ground, some time in orbit) for a very long time. If 18months is feasible, so might 20 years be. Of course, the political commitment to really explore Mars is fantasy at this point in history.

[William Barton]

One comment about interplanetary radiation. My understanding is, for interplanetary flight, the risks come from solar and cosmic radiation. If the expected Maunder Minimum really shows up  (unknown, because the last one happened before the invention of scientific instruments), there will be less solar radiation, and more cosmic. I expect, either way, interplanetary travel is going to require both shielding and sophisticated medical intervention.

[kfsorensen]

I think this is a step backwards from DRM III, too many rendezvous events, too much mass to launch.

I think it's a step backward from the NEP-AG studies that almost became a DRM IV...

For one thing, a 20 MWt NEP reactor is going to be a whole lot easier to develop than a 500 MWt nuclear thermal reactor.  More sustainable too.

Isn't it kind of silly to have a 500 MW nuclear reactor send you to Mars and then fly there on diddly little solar panels?

Maybe.

A NTR needs turbomachinery to pump the hydrogen through the reactor.  I think that 25 klb thrust, 900 second Isp, and 1000 psi pump exit pressure work out to 1MW of mechanical power.  This can be extracted under comparatively benign conditions via an expander cycle - the heat required gets transfered across a huge surface area (tiny metal tubes) between two liquids at a huge temperature differential.  It has to run a few times during the mission, for a few minutes at a time.

A 20 MWe nuclear reactor needs to handle at least 20 MW of mechanical power (using a Rankine cycle) and possibly much more (Brayton).  It has to reject many MW of waste heat via radiation into vacuum.  It has to work continuously for years with no maintenance.

Not clear which is easier, without doing the math.

ISRU using solar panels does get a bit tricky, for sure.

The turbomachinery is the least of your problems in developing a nuclear thermal engine.

[kfsorensen]

Maybe it's about justifying the enormous payload capability of Ares-V?

That would be my bet too.

Ross.

The NEP-AG study was done to show how to do Mars without heavy-lift.  It's no wonder that in an attempt to justify the Ares V they would move towards a superheavy architecture.

[libs0n]

The political barriers remain significant too.

I have a concept in relation to this: a joint Russian-American Mars expedition where the Russians construct and launch the nuclear components to bypass said domestic political opposition to things nuclear.  I think the Soviets built in space nuclear components, but I would not know what capability they have retained in this area.  They do have an extensive nuclear industry from which to draw on in the future.  Would NASA or would some American nuclear laboratory design such nuclear components?  Perhaps if need be the design portion could remain in America, while the construction and launch take place elsewhere.

[libs0n]

Something I've been wondering.  What happens when you couple an Earth orbiting momentum exchange tether for Trans Martian Injection with one of these high ISP technologies, like NEP SEP or Vasimr to reduce transit times?  I understand from a comment here once that at least for VASIMR that much of the time is spent circling out of Earth's gravity well, or something.  I also have in mind a tether orbiting Mars for the return trip.  I apologize for my lack of actual understanding of space mechanics.

I haven't done much thinking about a NASA Mars mission, but I have also thought that beginning with the moons and exploiting their resources and location for infrastructure was a good strategy.

Random thoughts I might as well include:
-VASIMR, maybe EP, apparently needs lots of energy: what of "beaming" power to the transit vehicle from a stationary power array?
-Getting the long transit times to Mars down would seem to be a priority for manned missions, or at least a priority I favour.  What are all the various "short transit times" options? edit: This may be asking too much so feel free to disregard the question.  On the other hand, I wouldn't be too disinclined to missions of longer duration transit, although as mentioned I would probably favour some 90 days to Mars or less option depending upon what's entailed.

[Kaputnik]

Am I correct in reading that the "surface habitat" lander (transfers crew from orbit to ground) lacks a landing abort capability?

It's designed to make a one-way trip to the surface. So, any 'abort' would just be reinforcing this capability. Unless you mean some sort of crew capsule that could be jettisoned separately? But it might well prove better to have a single reliable system- KISS.

[Kaputnik]

Something I've been wondering.  What happens when you couple an Earth orbiting momentum exchange tether for Trans Martian Injection with one of these high ISP technologies, like NEP SEP or Vasimr to reduce transit times?  I understand from a comment here once that at least for VASIMR that much of the time is spent circling out of Earth's gravity well, or something.  I also have in mind a tether orbiting Mars for the return trip.  I apologize for my lack of actual understanding of space mechanics.

I haven't done much thinking about a NASA Mars mission, but I have also thought that beginning with the moons and exploiting their resources and location for infrastructure was a good strategy.

Random thoughts I might as well include:
-VASIMR, maybe EP, apparently needs lots of energy: what of "beaming" power to the transit vehicle from a stationary power array?
-Getting the long transit times to Mars down would seem to be a priority for manned missions, or at least a priority I favour.  What are all the various "short transit times" options? edit: This may be asking too much so feel free to disregard the question.  On the other hand, I wouldn't be too disinclined to missions of longer duration transit, although as mentioned I would probably favour some 90 days to Mars or less option depending upon what's entailed.

A long transit from LEO to escape velocity is not all that bad, since the crew can join the craft just before it leaves Earth orbit altogether, using a small 'taxi' flight- e.g. an Orion coupled to a DHCSS or similar.

[kfsorensen]

like NEP SEP or Vasimr

It's not NEP, SEP, or Vasimr.

Vasimr is a thruster.  It might solar powered or nuclear powered.  It's like saying "should we drive there in a car, truck, or tire?"

[William Barton]

Am I correct in reading that the "surface habitat" lander (transfers crew from orbit to ground) lacks a landing abort capability?

It's designed to make a one-way trip to the surface. So, any 'abort' would just be reinforcing this capability. Unless you mean some sort of crew capsule that could be jettisoned separately? But it might well prove better to have a single reliable system- KISS.

Wasn't that the theory behind not have LAS for Shuttle? The crew riding down in a one-way vehicle sounds like an invitation to not survive a hard landing. There's a point where KISS = Keep It Simply Stupid. I can't be the only one who thinks having your ride home waiting for you to land successfully is not a good idea. Although, if you crash next to it, I guess you won't be needing it...

[libs0n]

like NEP SEP or Vasimr

It's not NEP, SEP, or Vasimr.

Vasimr is a thruster.  It might solar powered or nuclear powered.  It's like saying "should we drive there in a car, truck, or tire?"

I apologize for my callous use of acronyms.  My question should be refined to what does MX tether boosting offer to the various propulsion options in a Martian architecture and to an overall architecture that includes it.  Although, put that way, the answer would likely be less mission mass of some degree, and less time undertaken for low thrust vehicles to get up to the speed the tether offers.

Crewing through rendezvous of a low thrust vessel already underway is an interesting solution to the time problem, Kaputnik.

[kfsorensen]

My question should be refined to what does MX tether boosting offer to the various propulsion options in a Martian architecture and to an overall architecture that includes it.  Although, put that way, the answer would likely be less mission mass of some degree, and less time undertaken for low thrust vehicles to get up to the speed the tether offers.

If you broke the vehicle into pieces and assembled it at some high-energy location like EML2, the tether could be quite advantageous.  If you want to do it all in one throw, the tether will be super-sized for that payload and will not be advantageous.

[jongoff]

The turbomachinery is the least of your problems in developing a nuclear thermal engine.

Fair enough.  But with an NEP system, now you have to build the biggest electric propulsion system ever flown (by at least a few orders of magnitude), the biggest radiator ever flown (by at least two orders of magnitude), the biggest space nuclear reactor ever even ground tested (by what something like an order of magnitude at least?), etc.

At least NTRs in moderate sizes have been built and groundtested in the distant past.  In fact, the highest power reactor even run was the size of a desktop, and was an NTR...

That said, I think that using propellant depots, and just throwing some extra mass at it might actually yield a lower cost overall than trying to build some fancy nuclear propulsion system (NTR or NEP) that's only going to get used a few times over the course of many years.

Most of the cost of a chemical propulsion mars mission (as an aside, I agree that going aggressively on the ISRU on the Mars end does make a lot of sense) is the launch costs.  But with the kind of mass you're talking about, you have high potential for being able to provide flight rates capable of dropping prices substantially...

Of course talking about manned mars missions right now is utterly premature, when our country is no closer to having a sustainable lunar transportation network than it was when I was born.  By the time we're ready as a civilization to even start the engineering on a mars program, enough things will have changed that speculation at this point is probably futile.

~Jon

[JPK]

Re the 3.0 architecture
Could an aries V put both the NTR stage an space craft
up in a single launch ie 3 launchers per mission?

[kfsorensen]

when our country is no closer to having a sustainable lunar transportation network than it was when I was born.

Considering the quality of lunar mission analysis being done around the time you were born, I would say we are quite a bit FURTHER away from a sustainable lunar transportation network than we were when you were born.

Thanks, Mike.

[kfsorensen]

At least NTRs in moderate sizes have been built and groundtested in the distant past.  In fact, the highest power reactor even run was the size of a desktop, and was an NTR...

Correct, but you will never get to replicate the testing setup they used in the 60s.  Forget about it.

The NEP reactor is at least intended for closed-cycle operation, unlike the NTR.  Don't get me wrong, it's challenging, but I'd pick building NEP over trying to build an NTR or launching gigatons of LH2/LOX propellant on HLVs.

[jongoff]

Don't get me wrong, it's challenging, but I'd pick building NEP over trying to build an NTR or launching gigatons of LH2/LOX propellant on HLVs.

Ah come on, aren't we being a *wee* bit hyperbolic here (not that I ever do that myself...)?  Gigatons?  Isn't that like...6 orders of magnitude high?  :-)  The thing I like about doing a propellant depot based architecture is that it allows you to split the mission up into much smaller pieces.  And if for instance ISRU on Mars on on its moons turns out to work, you get a lot more leverage...

But once again, this discussion seems to be really premature.  "Predictions are tough--especially about the future."

~Jon

[Kaputnik]

Am I correct in reading that the "surface habitat" lander (transfers crew from orbit to ground) lacks a landing abort capability?

It's designed to make a one-way trip to the surface. So, any 'abort' would just be reinforcing this capability. Unless you mean some sort of crew capsule that could be jettisoned separately? But it might well prove better to have a single reliable system- KISS.

Wasn't that the theory behind not have LAS for Shuttle? The crew riding down in a one-way vehicle sounds like an invitation to not survive a hard landing. There's a point where KISS = Keep It Simply Stupid. I can't be the only one who thinks having your ride home waiting for you to land successfully is not a good idea. Although, if you crash next to it, I guess you won't be needing it...

Well what would your suggestion be?
Abort to anywhere other than the surface is virtually impossible. If it were otherwise, people wouldn't be swallowing up the cost/risk of ISRU in an attempt to get the ascent vehicle down to a reasonable mass.
The only feasible thing that I can think of is that the nominal cargo+crew landing is done under a combination of propulsion and parachutes, but the abort mode would jettison the cargo element leaving the smaller crew capsule to make a landing using its own descent system.
This would have two issues- firstly, mass on any Mars entry vehicle is going to be a very precious thing indeed. Such an abort system may simply not be possible within the mass limits. Secondly, it is almost certainly better to have a single highly capable landing system rather than two mass-squeezed ones- analogous to Apollo's three parachutes instead of two plus a reserve.

[kfsorensen]

Ah come on, aren't we being a *wee* bit hyperbolic here (not that I ever do that myself...)?  Gigatons?  Isn't that like...6 orders of magnitude high?  :-)

You're right...gigagrams of LH2/LOX propellant.

[bobthemonkey]

Am I correct in reading that the "surface habitat" lander (transfers crew from orbit to ground) lacks a landing abort capability?

It's designed to make a one-way trip to the surface. So, any 'abort' would just be reinforcing this capability. Unless you mean some sort of crew capsule that could be jettisoned separately? But it might well prove better to have a single reliable system- KISS.

Wasn't that the theory behind not have LAS for Shuttle? The crew riding down in a one-way vehicle sounds like an invitation to not survive a hard landing. There's a point where KISS = Keep It Simply Stupid. I can't be the only one who thinks having your ride home waiting for you to land successfully is not a good idea. Although, if you crash next to it, I guess you won't be needing it...

Well what would your suggestion be?
Abort to anywhere other than the surface is virtually impossible. If it were otherwise, people wouldn't be swallowing up the cost/risk of ISRU in an attempt to get the ascent vehicle down to a reasonable mass.
The only feasible thing that I can think of is that the nominal cargo+crew landing is done under a combination of propulsion and parachutes, but the abort mode would jettison the cargo element leaving the smaller crew capsule to make a landing using its own descent system.
This would have two issues- firstly, mass on any Mars entry vehicle is going to be a very precious thing indeed. Such an abort system may simply not be possible within the mass limits. Secondly, it is almost certainly better to have a single highly capable landing system rather than two mass-squeezed ones- analogous to Apollo's three parachutes instead of two plus a reserve.

The real alternative, although this brings a mass penalty, is to use a combined, pre-fuelled descent/ascent vehicle. It would be used in combination with a prelanded hab/cargo vehicle.

While this setup does provide anytime abort to orbit or surface during EDL it also decreases mass to surface by some margin. Primarily, you have to bring all your fuel along with you, precluding the use (to a vast extent) of ISRU.It also requires the crew, presumably in a weakened state after the outbound trip to EVA to their hab shortly after landing.

[kfsorensen]

If you're worried about abort during the descent to the Mars surface, you picked the wrong mission to go on in the first place...

[bobthemonkey]

Well said. I wasn't actually advocating a combined descent/ascent stage, unless it was flown as some kind of lifeboat once a permanent/semi-permanent presence has been established. 

[Kaputnik]

An abort-to-orbit option is Apollo paradigm. It is inappropripate for Mars. The mass penalty is horrendous, and the size of entry shell needed for such a massive vehicle would be enormous, requiring bucketloads of new technologies which would bring their own safety risks.
In any case, the surface of Mars is the best place to be, not Mars orbit. You can support a crew down there much more easily and safely, thanks to abundant CO2 for oxygen generation, some gravity, and the ability to dig in for protection against radiation. Providing these things in Mars orbit for eighteen months whilst you wait for the return window would be much harder.

[William Barton]

These things are all "well said," and I'm sure you all feel fully justified, but it is 100% engineering-based rationalization. If you can't think of a way to land on Mars without a credible abort scenario, then I guarantee you are never going to go. This makes "no crew with cargo" pale by comparison. Think about it in something other than rocketship terms. No abort to orbit at Mars? Fine. How are you going to accomplish abort to ground? You are going to have to provide abort to somewhere. Or else, one day, you (as hypothetical program manager) are going to be sweating in front of TV cameras explaining how your decisions that led to 6 astronauts winding up a fresh new crater on Mars were "the right decisions at the time."

[kfsorensen]

If you can't think of a way to land on Mars without a credible abort scenario, then I guarantee you are never going to go.

You might be able to guarantee that NASA will never go, but I don't think NASA will ever go beyond LEO anyway.  Some group of humanity with real balls will land on Mars someday, and they'll do it by accepting risks that you think are unacceptable.

[William Barton]

If you can't think of a way to land on Mars without a credible abort scenario, then I guarantee you are never going to go.

You might be able to guarantee that NASA will never go, but I don't think NASA will ever go beyond LEO anyway.  Some group of humanity with real balls will land on Mars someday, and they'll do it by accepting risks that you think are unacceptable.

What I see are enthusiasts who think antagonistic phrases like "real balls" constitute actual reasoning. It doesn't take "balls" to go to Mars, it takes money, so if you think you have the necessary "balls," get out your wallet and go. Oh, what? Don't have that much money? Require taxpayer help? Gee, that's too bad. Now put your "balls" away and start thinking in more realistic terms. No one is going to Mars or anywhere else through the application of "balls." And just to get you started, this has nothing to do with risks I personally think are or are not acceptable. It has to do with what happens in the real world, where budgets, engineering, and politics have to co-exist.

[William Barton]

Let me try to make this a little more clear, to see if we can get away from people chirping "well said" and making posts about "balls," neither of which accomplish anything.

My criticism of this architecture is because it's an excurisonary architecture masquerading as an expeditionary architecture. I feel excursionary architectures are bad at least in part because they invite "cancellation on impulse." Any excursionary Mars architecture invites becoming an Apollo-style dead end. Expeditionary architectures, while marginally more expensive, have two advantages. One is, they support a much larger range of abort modes without incurring special expense for them, as with excursionary architectures. The other is, once under way, they are much harder to cancel, politically speaking. STS and ISS offer examples of how this happens, and is, I believe, at the root of NASA's desire to have a moonbase. Note the various discussions about whether ISS will or will not be dumped in the sea come 2016.

The first advantage is, in some ways, much more important, because the requirements of an expeditionary architecture embrace all the necessary abort modes. Unless you live in some sci-fi fantasy where brave heroes head off to certain death as an investment in humanity's space-going future, there aren't going to be any Mars missions intentionally loaded with single-point LOC events. Those may happen a la STS, by budget driven (bad!) engineering decisions, but that's a separate issue.

So what abort events have to be supported? Post-TMI failures of various kinds. MOI failure. The Mars vessel has to be able to support the crew long enough for a complete round trip to Mars and then some. That means if you abort to orbit from a failed landing, you're aborting to a mother ship (or Phobos base or whatever) that can support you for the necessary time. Same with abort to surface. The lander/hab/whatever has got to be able to support you long enough for a rescue mission to have some chance of success. An expeditionary architecture with multiple (hopefully reuable) landers probably already has immediate rescue capability built in. Abort to surface for an excursionary architecture requires rescue to be sent from Earth.

And if you plan on the basis of "balls" or on the basis of perfect reliablility (fat chance), you're basically counting on losing a crew sooner or later. Probably sooner, if TMI, MOI, landing, ascent, TEI failures all result on LOC. Unless you think there's more than a remote chance of a commerical, for-profit Mars expedition any time in the coming century or two, what will happen after such a LOC is cancellation. On the other hand, partial-LOC during a Mars expedition is more like somebody getting killed in an EVA accident. To the budget process (and voters watching on TV), it will be more like a typcial indsutrial accident, than some great tragedy. When a high iron worker forgets his harness and falls to his death, it barely makes the news. When a building falls down because the architect didn't plan on some contingency, it's a big deal.

[bobthemonkey]

An abort-to-orbit option is Apollo paradigm. It is inappropripate for Mars. The mass penalty is horrendous, and the size of entry shell needed for such a massive vehicle would be enormous, requiring bucketloads of new technologies which would bring their own safety risks.
In any case, the surface of Mars is the best place to be, not Mars orbit. You can support a crew down there much more easily and safely, thanks to abundant CO2 for oxygen generation, some gravity, and the ability to dig in for protection against radiation. Providing these things in Mars orbit for eighteen months whilst you wait for the return window would be much harder.

Very true, but from at least DRM3 onwards, there has been provision on the MTV (Mars Transfer Vehicle) for ~500 days contingency supplies to support an anytime abort to orbit, which of course requires the ascent vehcile to be fully fuelled and checked out prior to crew EDL.

[DfwRevolution]

If you can't think of a way to land on Mars without a credible abort scenario, then I guarantee you are never going to go. This makes "no crew with cargo" pale by comparison.

You cannot compare the safety rationalizations of an LEO missions with those for a Mars mission. Any way you slice it, the Mars mission will have significantly more risk. NASA is rightfully risk-adverse about placing a crew in LEO because after 40 years of experience, we should be able to manage better than a 98% success rate. Nevertheless, lunar and Mars missions are going to be significantly more risky than an LEO mission and NASA is still going to fly them, budgets willing.

Since you mentioned the Shuttle crew/cargo paradigm, where NASA slipped-up was choosing an architecture with limited abort options when alternatives like a capsule could get the same crew into orbit with much lower risk. There is no practical way to give a Mars crew full "black zone" protection, so those risks will be accepted like they are today.

No abort to orbit at Mars? Fine. How are you going to accomplish abort to ground? You are going to have to provide abort to somewhere. Or else, one day, you (as hypothetical program manager) are going to be sweating in front of TV cameras explaining how your decisions that led to 6 astronauts winding up a fresh new crater on Mars were "the right decisions at the time."

Abort-to-ground would mean the same thing that Abort-to-orbit means for the Shuttle. It means you have the redundancy to survive a significant fault and still press-on toward your landing site.

The engineering implication is that you focus more on building the most resilient landing vehicle possible rather one which must have the delta-V to come all the way down to the surface and back to orbit again.

[Kaputnik]

These things are all "well said," and I'm sure you all feel fully justified, but it is 100% engineering-based rationalization.

It is engineering-based because abort-to-orbit is just not going to be possible with conceivable technology and mass limitations. If you think that makes it politically untenable, then fine.

If you can't think of a way to land on Mars without a credible abort scenario, then I guarantee you are never going to go. This makes "no crew with cargo" pale by comparison. Think about it in something other than rocketship terms. No abort to orbit at Mars? Fine. How are you going to accomplish abort to ground? You are going to have to provide abort to somewhere.

Abort to surface will be catered for. My guess would be that the primary descent system will have enough margin and capability to withstand multiple failures.
What was Apollo's abort-to-surface option? It was a third main parachute, not a separate reserve. What will Orion's abort-to-surface option be? These are analogous situations.

[Kaputnik]

An abort-to-orbit option is Apollo paradigm. It is inappropripate for Mars. The mass penalty is horrendous, and the size of entry shell needed for such a massive vehicle would be enormous, requiring bucketloads of new technologies which would bring their own safety risks.
In any case, the surface of Mars is the best place to be, not Mars orbit. You can support a crew down there much more easily and safely, thanks to abundant CO2 for oxygen generation, some gravity, and the ability to dig in for protection against radiation. Providing these things in Mars orbit for eighteen months whilst you wait for the return window would be much harder.

Very true, but from at least DRM3 onwards, there has been provision on the MTV (Mars Transfer Vehicle) for ~500 days contingency supplies to support an anytime abort to orbit, which of course requires the ascent vehcile to be fully fuelled and checked out prior to crew EDL.

It's good to have two abort options. What if the crew are unable to even attempt descent? However I would think that the surface is the better option- gravity, O2, and the potential for reuse of previous mission assets. Further, supporting the crew for eighteen months on the surface is the primary function of the surface hardware, not its secondary or abort function.

[kfsorensen]

What I see are enthusiasts who think antagonistic phrases like "real balls" constitute actual reasoning. It doesn't take "balls" to go to Mars, it takes money, so if you think you have the necessary "balls," get out your wallet and go.

The two will trade against each other.  More "balls" (risk), less $.  More $, less risk.  NASA's gotten to the point where their risk threshold is set so low that I don't think they'll ever make the trip.

But there are ways to go to Mars that could be significantly less expensive than any of these DRMs.  All of them entail very high risk. 

For instance, launch one person in a direct-entry Mars lander with just enough propellant to land (~500 m/s DV) and the built-in ISRU capability to make more propellant for the return leg (~5000 m/s DV).  Don't predeploy anything like Mars Direct--make the propellant during the 18 months or so you'll be on the surface waiting for the other leg of your conjunction-class trajectory.  Total mission time, roughly 3 years, all by yourself.

That would get the IMLEO of the mission WAY DOWN, maybe even to the point where you could launch the whole mission on a Zenit topped by two hydrogen stages.  The risk would be exceptionally high.  Too high for a government.  But perhaps within the range of a Richard Branson or a Bill Gates.

[Patchouli]

Kinda wasteful mass wise to be using Orion as the MAV.
But they seem to believe it would be safe to reuse the vehicle for a direct earth reentry even though it would have nearly 900days of storage time on it.

I'd still prefer to see the first Mars crew quarantined on a moon base or a space station for a few weeks before letting them back on Earth.

The very high risk part here though is the 500 day mars surface stay.
 I think it would be biting off far more then they can chew for their first attempt at a living on Mars.
This is going to be like learning to ride a bicycle you don't go enter the Tour de France right after loosing the training wheels.
The 20 day surface stay fast mission would be a safer bet for the first missions with longer stays happening after a few vehicles are on Mars and a base has started to take shape.
They'd have a big enough place to live and spare parts if anything breaks which will happen.
The rest of the architecture is surprisingly very conservative stuff just simple NTR engines no bimodal systems, high ISP cruise engines or anything.
Though I think one can be too conservative as bimodal system would give you more electrical power to play with and in space electrical power is life.
Though the ship appears to be spun for AG which is a nice and probably necessary feature to have if it's not a hotrod like VASIMR.

One thing though this may never fly as by the time someone gets around to going to Mars some other engine,launch system or other piece of technology will have come along and changed the game.

VASIMR for example and an engine invented by Pratt and Whitney the Triton a trimodal Engine may have already made solid core reactor NTR only missions obsolete.

It also would be good to have the mission able to abort a landing on Mars and swing back to Earth if needed.
Pure NTR can't do this but VASIMR with it's high ISP can catch back up to Earth during such an abort.

Well an NTR craft might be able to abort back to Earth if there was a few hundred tons of propellant for it already waiting to be used in Mars orbit.
Such as if a robotic factory was sent a head of time to Phobos to mine water for use as propellant.

[A_M_Swallow]

Use a robot instead of a person for deploying the ISRU fuel making equipment and a government may accept the risk.  The people do not have to leave LEO until sufficient ISRU exists for the return trip.

[kfsorensen]

Use a robot instead of a person for deploying the ISRU fuel making equipment and a government may accept the risk.  The people do not have to leave LEO until sufficient ISRU exists for the return trip.

This risks a surface rendezvous, which depending on entry conditions could be difficult.

[kfsorensen]

Though the ship appears to be spun for AG which is a nice and probably necessary feature to have if it's not a hotrod like VASIMR.

The only way VASIMR can be a hotrod is if it's coupled to a reactor that would make any thruster a hotrod.

VASIMR is to NEP as tire is to car.

[bobthemonkey]

An abort-to-orbit option is Apollo paradigm. It is inappropripate for Mars. The mass penalty is horrendous, and the size of entry shell needed for such a massive vehicle would be enormous, requiring bucketloads of new technologies which would bring their own safety risks.
In any case, the surface of Mars is the best place to be, not Mars orbit. You can support a crew down there much more easily and safely, thanks to abundant CO2 for oxygen generation, some gravity, and the ability to dig in for protection against radiation. Providing these things in Mars orbit for eighteen months whilst you wait for the return window would be much harder.

Very true, but from at least DRM3 onwards, there has been provision on the MTV (Mars Transfer Vehicle) for ~500 days contingency supplies to support an anytime abort to orbit, which of course requires the ascent vehcile to be fully fuelled and checked out prior to crew EDL.

It's good to have two abort options. What if the crew are unable to even attempt descent? However I would think that the surface is the better option- gravity, O2, and the potential for reuse of previous mission assets. Further, supporting the crew for eighteen months on the surface is the primary function of the surface hardware, not its secondary or abort function.

If they use the same hab for both the outbound and inbound trips, then they either use the ~500 day contingenct supply to stay in mars orbit until the next window, or head straight back to earth, in the same way as a short stay mission would.

ETA: And yes, abort to surface would be the preferred option.

[Kaputnik]

The very high risk part here though is the 500 day mars surface stay.
 I think it would be biting off far more then they can chew for their first attempt at a living on Mars....
The 20 day surface stay fast mission would be a safer bet for the first missions with longer stays happening after a few vehicles are on Mars and a base has started to take shape.

If you opt for a 20-day surface mission, your total mission length doesn't become 480 days shorter.
There is no such thing as a 'short' Mars mission. You can do one in two years, or in three years.
For a two year mission, with 20-60 days spent on the surface, you must spend the remaining c.700 days flying through space in a spacecraft which must survive completely unsupported, with no natural resources to draw on, and swinging as close to the Sun as Venus, giving a much harsher thermal and radiation environment.
For a three-year mission, with c.500 days spent on the surface, the crew only have to survive the interplanetary phase for a total of about 365 days. For the rest of the time they can 'dig in' at Mars, taking advantage of CO2, H2O, gravity, and soil for radiation shielding.

IMHO, the short-stay mission is the riskier of the two.

[kfsorensen]

IMHO, the short-stay mission is the riskier of the two.

Not only riskier, but much more propulsively intensive.

Orbital mechanics dictates the length of a Mars mission.  If that's considered too risky, then you're not ready to go yet.

[Patchouli]

The very high risk part here though is the 500 day mars surface stay.
 I think it would be biting off far more then they can chew for their first attempt at a living on Mars....
The 20 day surface stay fast mission would be a safer bet for the first missions with longer stays happening after a few vehicles are on Mars and a base has started to take shape.

If you opt for a 20-day surface mission, your total mission length doesn't become 480 days shorter.
There is no such thing as a 'short' Mars mission. You can do one in two years, or in three years.
For a two year mission, with 20-60 days spent on the surface, you must spend the remaining c.700 days flying through space in a spacecraft which must survive completely unsupported, with no natural resources to draw on, and swinging as close to the Sun as Venus, giving a much harsher thermal and radiation environment.
For a three-year mission, with c.500 days spent on the surface, the crew only have to survive the interplanetary phase for a total of about 365 days. For the rest of the time they can 'dig in' at Mars, taking advantage of CO2, H2O, gravity, and soil for radiation shielding.

IMHO, the short-stay mission is the riskier of the two.

Actually a fast mission is possible but you do waste about 30 days getting out of earth's gravity well.
http://dma.ing.uniroma1.it/users/bruno/Petro.prn.pdf
http://biography.jrank.org/pages/3309/Chang-D-az-Franklin-R-1950-Astronaut-Physicist-Travel-Mars.html

One nice thing about nuclear electric with VASIMR is you are no longer forced to wait for perfect alignments.
Your out bound time can be cut down to just 93 days.
With that much delta V you can do stuff like fly inside the orbit of Earth to catch it vs waiting for it.
Plus perform plane changes etc.

I pretty much agree with it's inventor this is the engine that is probably going to take us to Mars.

I'd only go with the 900 day mission if three things can be demonstrated first one you can land payloads so accurately on Mars you could almost stack them if you wanted.
Two assemble and deploy things roboticaly before the crew ever gets there.
Three make sure you have two or three of everything needed on hand because Murphy is not going to take a vacation because you want him to.
Get these three things done you probably could even do the mission using just clunky chemical propulsion if you wished.
But you are right Mars does make getting water and O2 non issues if you have a surface  reactor,some ISRU and mining equipment on hand.
I wouldn't go with solar as you can't put the crew to sleep like you can the MER rovers.
That base is going to need 20 to 50KW no matter what the weather is outside.
But with a 900 day long mission one of the crew should be a trained surgeon and a second trained as a EMT and Nurse.
The time delay makes tele robotic surgery impossible.
 
Also bring one of these along it just might save the crew's lives.
http://www.eos.info/en/products/metal-laser-sintering.html
A mrfixit guy would be nice to have as well but you probably could get away with up loading instructions to them and making sure every crew member knows how to repair things.

As for the Hab why not use a BA330 it's bigger then Skylab yet only weighs 55,000lbs?
A large hab is going to be needed to keep the crew from going crazy as you need to provide each one with personal space.
 I think 330 cubic meters may be just enough for this but it might be best see what happens with the ESA's Mars 500 simulation before deciding on anything.
Use their complaints as input for hab design.
One very easy near no mass thing that can really help moral would be to up link the latest movies and games to the crew as well as random stuff found on the net.
A couple of terabytes of storage weighs so little now it's a non issue and not including it would be silly.

[kfsorensen]

The performance that is called "VASIMR" (since the hype has gone way beyond VASIMR as a thruster) is a chimera.  It was based around the use of an extremely hypothetical nuclear reactor pushed by a Iranian-born, Florida-based professor who has been indicted for fraud by NASA.  This "VASIMR" system that you're talking about simply doesn't and won't ever exist.

[Kaputnik]

I'd only go with the 900 day mission if three things can be demonstrated first one you can land payloads so accurately on Mars you could almost stack them if you wanted.
Two assemble and deploy things roboticaly before the crew ever gets there.
Three make sure you have two or three of everything needed on hand because Murphy is not going to take a vacation because you want him to.
Get these three things done you probably could even do the mission using just clunky chemical propulsion if you wished.

I do wish you'd use some punctuation in your posts, Patch, they can be very hard to follow.

Landing accuracy on Mars is already at just a few kilometres. So long as a relatively flat and hazard-free landing area is chosen, a powerful rover could drag payloads on skids or wheels for surface rendezvous. Obtaining higher levels of landing precision will be mostly a matter of lifting entry, to be attempted on MSL, plus a greater delta-v budget on the descent propulsion stage. Better modelling and observation of the atmosphere will help too.
I don't think we would want to land payloads any closer than a few hundred metres from one another for of damage by dust kick-up.

On your second point, IMHO it will be a requirement that the crew do not attempt to land unless there is an ascent vehicle all ready to go on the surface. Since ISRU is all but essential for any realistic mission plan, that means a robust self-deploying system. It is for this reason that I prefer nuclear power over solar for surface operations.

Thirdly, duplicating systems is not always the best option. It might be best to use the same mass and budget to provide one extremely rugged system, with appropriate contingency and abort options. Certainly, though, every piece of hardware that leaves Earth orbit should be designed in such a way that spare parts, components, and tools can be interchanged as much as possible, and all vital systems should be repairable by the crew.

But you are right Mars does make getting water and O2 non issues if you have a surface  reactor,some ISRU and mining equipment on hand.

I wouldn't say 'non issue'. It just means you can tolerate some leakage or wastage in the system much more easily than if you are up in space.

As for the Hab why not use a BA330 it's bigger then Skylab yet only weighs 55,000lbs?
A large hab is going to be needed to keep the crew from going crazy as you need to provide each one with personal space.
 I think 330 cubic meters may be just enough for this but it might be best see what happens with the ESA's Mars 500 simulation before deciding on anything.
Use their complaints as input for hab design.
One very easy near no mass thing that can really help moral would be to up link the latest movies and games to the crew as well as random stuff found on the net.
A couple of terabytes of storage weighs so little now it's a non issue and not including it would be silly.

Which Hab are you referring to- surface or transit?
Talk of the size for either is premature until you choose a crew size.

[Patchouli]

The performance that is called "VASIMR" (since the hype has gone way beyond VASIMR as a thruster) is a chimera.  It was based around the use of an extremely hypothetical nuclear reactor pushed by a Iranian-born, Florida-based professor who has been indicted for fraud by NASA.  This "VASIMR" system that you're talking about simply doesn't and won't ever exist.

The reactor Diaz planned to use is not that reactor but instead a 100KW unit by general electric and the US navy.
The crazy fast 30 day vs 98 day transit was a what if study if you had megawatts of power to play with.
Cooling three 100 KW reactors is very possible on a vessel of that size with existing technology esp considering ISS has to reject nearly 80KW of heat with radiators that are a fraction of the area and in a worse thermo environment .
http://www.lockheedmartin.com/products/HeatRejectionRadiators/index.html
Each reactor would need at most 6987sqft of radiator if the system ran at the same temp as ISS's cooling system
Since the system would likely run around 450C or higher the thremo heat rejection for a given area is going to be higher so that likely can be reduced.
As for fraud in a  program what about the huge amounts of fraud and outright lies surrounding the two Ares vehicles and this is not just one crook but entire companies?

Other questionable claims we can bring up would be some of the performance claims of fully closed loop life support systems which I believe may not be demonstrable until long after in space nuclear power and high level Mars ISRU have been in use.

The partly failed biosphere 2 experiment comes to mind about claims you'll be able to grow 90% of your food on a Mars mission.
There was the Soviet BIOS-3 experiments but these were shorter and mostly concentrated on O2 and water recycling but it was successful.
http://en.wikipedia.org/wiki/BIOS-3
This also gives an idea of the kinda of power needed for true closed loop it's comparable to a NEP ship's propulsion needs.

Which Hab are you referring to- surface or transit?
Talk of the size for either is premature until you choose a crew size.

Mostly the surface hab a non AG craft probably can probably get away with a smaller hab since you can make use of space better in microgravity.
Also the transit time is going to be around half the surface stay if you choose the 500 day stay.
Though from an engineering stand point in interest of keeping commonality it probably would be best to just stick with the same module for both the MTV and hab if you can afford it in your mass budget.
Though with chemical and basic NTR the mass budget can get pretty tight.
I know it's not due to physics you can always send up another EDS but due to cost because you may not always be able to afford to send up another EDS.
Some of Bono's and Traux's Mars missions were truly massive despite being all cryogenic. They just had a big 400T payload LV to brute force things along.

[A_M_Swallow]

On your second point, IMHO it will be a requirement that the crew do not attempt to land unless there is an ascent vehicle all ready to go on the surface. Since ISRU is all but essential for any realistic mission plan, that means a robust self-deploying system. It is for this reason that I prefer nuclear power over solar for surface operations.

You can go for both nuclear and solar power.  Nuclear may has to be made on Earth, too many chemicals and processes are involved.  Mechanical solar thermal equipment like Stirling engines can probably be made using ISRU techniques on the Moon and Mars.

[Jim]

As for fraud in a  program what about the huge amounts of fraud and outright lies surrounding the two Ares vehicles and this is not just one crook but entire companies?

That doesn't change the fact that your idea is non viable

[kfsorensen]

The reactor Diaz planned to use is not that reactor but instead a 100KW unit by general electric and the US navy.

No way.  You're off by at least three orders of magnitude.  You couldn't even budge a manned Mars ship out of orbit much less send it to Mars in 90 days with 2-3 100kWe units.  Do the math.  There's simply not enough watts per kilogram.

"VASIMR" as a total propulsion system (thrusters, fuel, tankage, reactors, etc) was on the order of 200 MWe if memory serves from FCD's papers.

[Patchouli]

The reactor Diaz planned to use is not that reactor but instead a 100KW unit by general electric and the US navy.

No way.  You're off by at least three orders of magnitude.  You couldn't even budge a manned Mars ship out of orbit much less send it to Mars in 90 days with 2-3 100kWe units.  Do the math.  There's simply not enough watts per kilogram.

"VASIMR" as a total propulsion system (thrusters, fuel, tankage, reactors, etc) was on the order of 200 MWe if memory serves from FCD's papers.

I decided to crunch the numbers it was way off but it was not three orders but instead ended up being a little less then two orders of magnitude off assuming a 270ton vehicle.
The answer humorously seems to be 42 if you take in account it loosing mass due to propellant expenditure.
300KW only produces 4.5N in the 5000sec ISP mode.
For a 3000M/sec burn in 30 days it would need 312.5 newtons of force per second well actually closer to 190N thrust as the vehicle would be loosing mass fairly quickly since the engines would be in a low ISP mode.

The writers at popsci must have dropped a digit or that reference mission was a BNTR and used an NTR mode for the trans Mars injection burn.
I doubt Diaz would make a mistake like that as here is his company's OTV data and it's all good.
http://www.adastrarocket.com/ISGLP_JPSquire2008.pdf
That OTV looks like it can save the plans for a moon base which are kinda screwed right now.


This does show one thing we need to spend some serious money on advance propulsion research and ways of improving in space heat rejection.
That or use Zurbin's NSWR engine and tell the anti nuke people to stuff it.
http://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

Though standard NTR can deliver 900sec ISP timberwind could manage 1000sec.
But you'll still be wedded to those damn orbital conjunctions and have no good abort options ie you better land on Mars or else.

Another option since solid core NTR can probably be designed to be like a goat and use anything that catches neutrons as propellant might be see if ISRU can be used with them.
If you can refuel it "really the wrong term since all your taking on is propellant not fuel" you can really do some interesting missions and it starts being like a VASIMR ship with a 16 megawatt reactor.
In some ways even better as there is no spiraling out of the gravity well it's a high thrust propulsion system.

But NASA does seem to be on the right track choosing nuclear propulsion as the numbers just get horrid for pure cryogenic chemical missions.
By horrid I mean the payload mass fractions which means the mission is forced to be very light ie dangerous or you're forced to lift some very insane masses into LEO which would be costly.

[kfsorensen]

Though standard NTR can deliver 900sec ISP timberwind could manage 1000sec.

Doubtful that "standard" NTR could manage 900 s.  Maybe 800.

Timberwind was dynamically unstable and the the fuel particles would weld together in operation, blocking hydrogen coolant flow and causing the engine to explode in a split second.  Timberwind was an idea that never would have worked.

[kfsorensen]

I decided to crunch the numbers it was way off but it was not three orders but instead ended up being a little less then two orders of magnitude off assuming a 270ton vehicle.

Yeah, I'm remembering now that the 200 MWe case was for a one-year-round-trip Mars mission, not for the more "reference" cases FCD looked at.  They were in the 10-50 MWe range.

Either way, the performance of any NEP in that power range has as much to do with the reactor technology as with the thruster technology.  You can't consider one in isolation of the other.

[Kaputnik]

On your second point, IMHO it will be a requirement that the crew do not attempt to land unless there is an ascent vehicle all ready to go on the surface. Since ISRU is all but essential for any realistic mission plan, that means a robust self-deploying system. It is for this reason that I prefer nuclear power over solar for surface operations.

You can go for both nuclear and solar power.  Nuclear may has to be made on Earth, too many chemicals and processes are involved.  Mechanical solar thermal equipment like Stirling engines can probably be made using ISRU techniques on the Moon and Mars.

We're thinking in different timescales here. If you have the infrastructre to actually build your power generation on Mars, then robotic deployment of the panels is the least of your worries. You will likely have a sizeable permanent population to oversee deployment.
I was talking in the context of the first mission, where there will nobody around to unfold solar panels across a rocky and undulating surface. Nuclear seems the most practical choice if you want ISRU operations to be completed in a reasonable timeframe.

[A_M_Swallow]

Trips to Mars take several years, so if you make your designs simple then ISRU manufacturing can be up and running before the first people arrive.  This is the advantage of rovers with robotic arms.

Using nuclear power means round the clock operation, very useful on the moon.  An automated outpost can increase its power supply by using the nuclear powered equipment to make solar power generators.  This may for instance allow more than one machine to operate at a time.

[Jim]

Trips to Mars take several years, so if you make your designs simple then ISRU manufacturing can be up and running before the first people arrive. 

That is ludicrous.  We can't even do that on earth.  Initial ISRU for propellants is hard enough.  Manufacturing is decades away from the first landing

[Kaputnik]

Trips to Mars take several years, so if you make your designs simple then ISRU manufacturing can be up and running before the first people arrive.  This is the advantage of rovers with robotic arms.

Using nuclear power means round the clock operation, very useful on the moon.  An automated outpost can increase its power supply by using the nuclear powered equipment to make solar power generators.  This may for instance allow more than one machine to operate at a time.

I wish people would think more realistically about the technologies and timescales involved in Mars exploration.
This thread is about the FIRST manned missions. ISRU involving anything other than globally available (i.e. atmospheric) Martian resources is off the table.
Maybe, one day, there will be factories on Mars building the pressure vessels, pumps, and power sources for an ISRU plant. But it is hardly a safer or lower mass way of going about it.

[A_M_Swallow]

Details about Mars.

Current Mars Technology

The Mars Exploration Rovers (Spirit and Opportunity) are solar powered machines with 6 wheels that can drive/rove around Mars.  They each have cameras, an arm with scoop and various scientific/chemical analysis instruments.   The future Mars Science Laboratory is expected to be powered by small radioisotope thermoelectric generators (RTG).

No existing examples of large landers, large nuclear power supplies or humans so these must be assumed to be at a low technological readiness.  Manned missions are at least 20 years away.


Atmosphere of Mars

surface_pressure = 0.7–0.9 Pascal (unit) |kPa

atmosphere_composition =
 95.72% Carbon dioxide
 2.7% Nitrogen
 1.6% Argon
 0.2% Oxygen
 0.07% Carbon monoxide
 0.03% Water vapour
 0.01% Nitric oxide
 
 2.5 Parts per million (ppm) Neon
 300 ppb Krypton
 130 ppb Formaldehyde
 80 ppb Xenon
 30 ppb Ozone
 10 ppb Methane

[A_M_Swallow]

If water is easily obtainable then carbon dioxide can be converted into fuels such as methane.

CO₂ can be split into oxygen and carbon.  Carbon is a good material in the form of carbon fibre and graphite.

Carbon dioxide, nitrogen, water (H₂O) and energy can be combined to form plastics.  There are lots of things that can be made out of plastic using 3D printers.

[MKremer]

If water is easily obtainable then carbon dioxide can be converted into fuels such as methane.

CO₂ can be split into oxygen and carbon.  Carbon is a good material in the form of carbon fibre and graphite.

Carbon dioxide, nitrogen, water (H₂O) and energy can be combined to form plastics.  There are lots of things that can be made out of plastic using 3D printers.

You first must create monomers (ethene, propene, benzine, etc) as a base to then synthesize polymers for the plastics. The monomer molecules could also require nitrogen or chlorine, depending on the type of plastic needed.  The polymer process also requires high heat and very high pressures.
Monomer production in very large volumes would be needed for usable equivalent masses of plastic (molecular mass ratios I could find ranged from about 1.5:1 to 2:1).

[Kaputnik]

Nobody is suggesting that Mars lacks the raw materials to support a human presence.

However the equipment needed to locate, mine, process and refine, then manufacture solar cells, pressure vessels, pumps, refrigeration units, etc etc, will not weigh less than an ISRU plant that has been built on Earth.

Thus, for the initial missions at least, the only Martian resources that will be used will be those known to be abundantly available and easily processed- atmopsheric gasses. It is unlikely that even water ice would be used until later missions. The CO2 from the atmosphere would be processed into propellant and oxygen for breathing. To think that actual hardware would be produced robotically is just unrealistic.

[Jim]

Details about Mars.

Why was this post necessary?

[A_M_Swallow]

Details about Mars.

Why was this post necessary?

This website does not have a FAQ on Mars.
Any information not publicly available is not available to the public.
We have been requested to avoid "ISRU involving anything other than globally available (i.e. atmospheric) Martian resources is off the table."
The posting gives a common starting point for what ISRU facilities are available for Mars.

For instance nitrogen is available as a feed stock because it is the second most abundant gas on Mars.  Since it has been done Mars rovers are relatively easy.

Edit: nitrogen is the third most abundant element in Mars's atmosphere but second most abundant gas.

[Kaputnik]

This website does not have a FAQ on Mars.

http://forum.nasaspaceflight.com/index.php?topic=12196.0

[Jim]

Any information not publicly available is not available to the public.

We have been requested to avoid "ISRU involving anything other than globally available (i.e. atmospheric) Martian resources is off the table."
The posting gives a common starting point for what ISRU facilities are available for Mars.

The makeup of Mars atmosphere is publicly available

In the context of "Mars Design Reference Architecture 5.0", anything but propellant production with CO2 is off the table. 

That is the issue with your posts, you keep bringing up items that are decades away from the discussion timeframe.

[kkattula]

Getting back to the descent abort scenarios:

A lander with independant descent & ascent stages, and crew riding in the ascent stage (ala LEM), could have both Abort-to-Orbit and Abort-to-Surface options at different stage in the descent, without prohibitive mass penalties.

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.  This option might add 10% to the mass of the ascent stage, and still make use of ISRU for most of the ascent propellant.

The above assumes you're packing enough cargo/equipment on the descent stage, that it significantly out masses the ascent stage. Otherwise you might just be better off with multiple redundant engines and avionics on the one combined stage.

Also, pre-position one unmanned lander and re-fuel via ISRU. The crew arrive in a second lander, which is also re-fuled by ISRU and becomes the 'pre-postioned' for the next crew, while they ascend in the first. This way the crew always have two ascent vehicles available.

[kkattula]

In regards to the overall architecture, I also think it is too 'excursionary'. Each mission includes everything. Nothing is re-used.

I prefer a depot based architecture progressively expanded from LEO to EML-2 to Mars orbit (Phobos Base?) to Mars surface. Using ISRU when/if it becomes practical.

A typical Mars mission would then be:

1)  Crew capsule to LEO.
2)  Fast ferry to EML-2
3)  Fast AG transhab to Mars orbit
4)  Lander to Mars surface

Then the same in reverse to return.

Fuel and cargo would be sent on slower, more fuel-efficient trajectories.

[simonbp]

Well, what bugs me is I can't find any hard data about radiation exposure from probes we have sent to Mars.

That's 'cause JSC took the site offline.

The only high-quality radiation sensor flown to Mars thus far was the MARIE instrument on Mars Odyssey, run by JSC. Odyssey is still working (oldest operational spacecraft at Mars), but MARIE got fired by coronal mass ejection in 2003 (the height of the last Solar Max). For some reason, JSC didn't maintain the site, so you have to go to the internet archive:

http://web.archive.org/web/20060929140457/marie.jsc.nasa.gov/Index.html

http://en.wikipedia.org/wiki/Mars_Radiation_Environment_Experiment

MSL will have a radiation sensor on it (the first actually on the surface), though they'll have to remove the background from the MMRTG...

http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2297.pdf

Simon

[Patchouli]

In regards to the overall architecture, I also think it is too 'excursionary'. Each mission includes everything. Nothing is re-used.

I prefer a depot based architecture progressively expanded from LEO to EML-2 to Mars orbit (Phobos Base?) to Mars surface. Using ISRU when/if it becomes practical.

A typical Mars mission would then be:

1)  Crew capsule to LEO.
2)  Fast ferry to EML-2
3)  Fast AG transhab to Mars orbit
4)  Lander to Mars surface

Then the same in reverse to return.

Fuel and cargo would be sent on slower, more fuel-efficient trajectories.

A lot of people don't realize being too excursionary was partly what killed Apollo.

If Apollo had placed a long term base on the moon it's would have been a lot harder to ax politically as you would be throwing away useful assets.

I feel all Mars surface habs should be able to be moved and integrated into a base and the MTV vehicle be made reusable.

Don't want to fly a use MTV to Mars a second time then reuse the drive section for a lunar cargo shuttle or use it as a booster for an unmanned probe or Mars cargo flight.

[Jorge]

Getting back to the descent abort scenarios:

A lander with independant descent & ascent stages, and crew riding in the ascent stage (ala LEM), could have both Abort-to-Orbit and Abort-to-Surface options at different stage in the descent, without prohibitive mass penalties.

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.

And if the cause of the abort is descent propulsion, the mode changes to "die".

It is appropriate to compare the size of abort "black zones" for lunar descent architectures. Apollo had, and Altair will have, a small "dead-man zone" near the surface where the ascent stage will not be able to establish a positive h-dot prior to lunar surface impact. The alternatives being discussed here would have much larger black zones.

[madscientist197]

The solution is to have a backup propulsion system like L3 did. The lander used a single chamber 11D411 main engine (throttleable) and a backup two chamber 11D412 engine. A two chamber single engine backup means that you only need two engines rather than four, improving LOC.

[kkattula]

Getting back to the descent abort scenarios:

A lander with independant descent & ascent stages, and crew riding in the ascent stage (ala LEM), could have both Abort-to-Orbit and Abort-to-Surface options at different stage in the descent, without prohibitive mass penalties.

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.

And if the cause of the abort is descent propulsion, the mode changes to "die".

It is appropriate to compare the size of abort "black zones" for lunar descent architectures. Apollo had, and Altair will have, a small "dead-man zone" near the surface where the ascent stage will not be able to establish a positive h-dot prior to lunar surface impact. The alternatives being discussed here would have much larger black zones.

Not necessarily. If descent propulsion fails too far into descent for the ascent stage to reach orbit, the ascent stage separates and completes the descent. Probably to a rough landing, hopefully somewhere near the habitat.

It's not a great abort option. just gives the crew a chance

[Jorge]

Getting back to the descent abort scenarios:

A lander with independant descent & ascent stages, and crew riding in the ascent stage (ala LEM), could have both Abort-to-Orbit and Abort-to-Surface options at different stage in the descent, without prohibitive mass penalties.

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.

And if the cause of the abort is descent propulsion, the mode changes to "die".

It is appropriate to compare the size of abort "black zones" for lunar descent architectures. Apollo had, and Altair will have, a small "dead-man zone" near the surface where the ascent stage will not be able to establish a positive h-dot prior to lunar surface impact. The alternatives being discussed here would have much larger black zones.

Not necessarily. If descent propulsion fails too far into descent for the ascent stage to reach orbit, the ascent stage separates and completes the descent. Probably to a rough landing, hopefully somewhere near the habitat.

It's not a great abort option. just gives the crew a chance

So you're proposing to put landing legs, and descent sensors, on the ascent stage? Otherwise you're exaggerating; the crew has no chance without those.

[Patchouli]

Getting back to the descent abort scenarios:

A lander with independant descent & ascent stages, and crew riding in the ascent stage (ala LEM), could have both Abort-to-Orbit and Abort-to-Surface options at different stage in the descent, without prohibitive mass penalties.

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.

And if the cause of the abort is descent propulsion, the mode changes to "die".

It is appropriate to compare the size of abort "black zones" for lunar descent architectures. Apollo had, and Altair will have, a small "dead-man zone" near the surface where the ascent stage will not be able to establish a positive h-dot prior to lunar surface impact. The alternatives being discussed here would have much larger black zones.

Not necessarily. If descent propulsion fails too far into descent for the ascent stage to reach orbit, the ascent stage separates and completes the descent. Probably to a rough landing, hopefully somewhere near the habitat.

It's not a great abort option. just gives the crew a chance

So you're proposing to put landing legs, and descent sensors, on the ascent stage? Otherwise you're exaggerating; the crew has no chance without those.

Might be best to take the airliner approach to safety give the lander engine out capability and make the hardware redundant enough that it can handle multiple failures.

Redundancy saved the day many times during the space program.

[Kaputnik]

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.  This option might add 10% to the mass of the ascent stage, and still make use of ISRU for most of the ascent propellant.

Based on what? A Mars entry and landing sequence is nothing like a lunar one. This has major implications for an abort-to-orbit. A LEM-type ATO is only possible in the very last stages of descent when the parachutes and aershell have been jettisoned and the craft is under subsonic powered descent. Of course, at this stage, you essentially need a fully fuelled ascent stage to get back to orbit.
If you try to use the ATO option earlier than this, you need to cast off the heatshield whilst the craft is still subject to significant heat and dynamic pressure- not a good idea! A hypothetical secondary problem is that, assuming the lander somehow avoided being burnt/torn apart, there is very little knowledge today about how to fire rockets into a hypersonic airstream. It will do very weird things to the plume and could finish off the job of burning up the lander quite nicely. Understanding such interactions would require a massive R&D effort which makes it a very, very expensive option.

The only way that you could realistically include some sort of partial-ATO would be if it was available between de-orbit and entry- i.e. you have a rocket that you cna fire during the half-orbit coast towards entry. IMHO this is such a short timeframe that we should be able to trust the vehicle to operate correctly. There is ample time to check out critical systems before the de-orbit burn commits you to a landing.

Also, pre-position one unmanned lander and re-fuel via ISRU. The crew arrive in a second lander, which is also re-fuled by ISRU and becomes the 'pre-postioned' for the next crew, while they ascend in the first. This way the crew always have two ascent vehicles available.

Something similar to this might become SOP. IMHO it will be a mission rule that no crews attempt entry (or even TMI) without a fully functional and fuelled-up ascent vehicle awaiting them on the surface. Since each crew will arrive in the same launch window as another ascent vehicle, the new one becomes a backup in case of any failures.
Mission plans don't necessarily have the crews landing in the ascent vehicle, by the way. Zubrin suggested the crew should ride down in the hab, which I agree with. The MAV isn't any use to them until it's completed ISRU operations and is ready to launch, which will take months, and it won't be able to support the crew for that time.

(And if you are wondering why I assume ISRU, go read up about Mars EDLS and mass limits).


One general point:
This abort-to-orbit talk is out of place. Do not compare landing on Mars with landing on the moon. Compare it with landing on Earth. How many Earth landing vehicles have had abort-to-orbit capability? None, of course. I doubt any have even had the capability to wave off entry after the de-orbit burn, which, as I explained above, is about the only possible place you could have such an ATO option.

[kkattula]

A partly fueled ascent stage would allow Abort-to-Orbit during the initial stages of the descent. When orbit is beyond reach, the mode changes to Abort-to-Surface.  This option might add 10% to the mass of the ascent stage, and still make use of ISRU for most of the ascent propellant.

Based on what? A Mars entry and landing sequence is nothing like a lunar one. This has major implications for an abort-to-orbit. A LEM-type ATO is only possible in the very last stages of descent when the parachutes and aershell have been jettisoned and the craft is under subsonic powered descent. Of course, at this stage, you essentially need a fully fuelled ascent stage to get back to orbit.
If you try to use the ATO option earlier than this, you need to cast off the heatshield whilst the craft is still subject to significant heat and dynamic pressure- not a good idea! A hypothetical secondary problem is that, assuming the lander somehow avoided being burnt/torn apart, there is very little knowledge today about how to fire rockets into a hypersonic airstream. It will do very weird things to the plume and could finish off the job of burning up the lander quite nicely. Understanding such interactions would require a massive R&D effort which makes it a very, very expensive option.

The only way that you could realistically include some sort of partial-ATO would be if it was available between de-orbit and entry- i.e. you have a rocket that you cna fire during the half-orbit coast towards entry. IMHO this is such a short timeframe that we should be able to trust the vehicle to operate correctly. There is ample time to check out critical systems before the de-orbit burn commits you to a landing.

...

One general point:
This abort-to-orbit talk is out of place. Do not compare landing on Mars with landing on the moon. Compare it with landing on Earth. How many Earth landing vehicles have had abort-to-orbit capability? None, of course. I doubt any have even had the capability to wave off entry after the de-orbit burn, which, as I explained above, is about the only possible place you could have such an ATO option.

Good points. 

I did suggest that more redundancy might be a better option.

I misread the section on propulsive capture vs aero-capture, and thought it refered to EDL. Clearly heating & aero loads would require a prohibitive mass penalty to make a separation survivable between entry interface and parachute deployment.

I would point out, however, that there would be no requirement to fire rockets INTO a hypersonic airstream. For abort to orbit you want to increase speed not decrease it.   And by the time there is a significant airstream, it's too late for abort to orbit anyway. You pretty much have to stay with the descent stage until the heatshield is discarded or it breaks up.

The only situation I can think of where an abort to orbit would be practical, is where the descent stage suffers a major power or control failure, during or after the de-orbit burn, and you don't want to enter in a dead bird. In that case, any sort of manual control of the RCS should be enough to re-establich orbit. So again, more redundancy would work as well or better.

[Kaputnik]

I only presumed that you'd fire into the airstream because people have been suggesting a LEM-type 'anytime abort' option, and it just isn't feasible.
You probably wouldn't need to fire directly into the airstream, but you would be obliquely towards it- otherwise you're just accelerating your impact with Mars!

In any case, it is all hypothetical, because the spacecraft would burn up or be torn apart if you jettisoned the heatshield/aeroshell too early in descent.

[mmeijeri]

I see that the plan is to use NTR. Might one hidden reason for NASA's insistence on building its own EDS be that this would give them the in-house expertise to build a large stage as a precursor to building an NTR stage? Would there be much synergy?

[Kaputnik]

I see that the plan is to use NTR. Might one hidden reason for NASA's insistence on building its own EDS be that this would give them the in-house expertise to build a large stage as a precursor to building an NTR stage? Would there be much synergy?

I don't think an in-house EDS is anything unusual given how NASA are going about the rest of the program. IMHO it's not a front for a covert NTR project.

However, an NTR stage of a similar size and mass to the EDS could conceivably share some production details such as tanking, avionics, and RCS.

FWIW, I'm no fan of NTR. By the time you factor in shielding and engine mass you lose much of the advantage of higher isp. The development costs will certainly be a nightmare, and would pay for a large number of conventional EDSs to be launched to do the same job. In fact, even once operational, I'm not sure that an NTR stage will cost less than the two EDSs and launchers that it would replace.

[Patchouli]

I see that the plan is to use NTR. Might one hidden reason for NASA's insistence on building its own EDS be that this would give them the in-house expertise to build a large stage as a precursor to building an NTR stage? Would there be much synergy?

Not just NTR likely bimodal NTR and when you are not operating in high thrust mode and engines can operate as a power reactor.

Bimodal NTR solves issue with tracking the sun while the ship is spun for artificial G and you no longer have to design solar arrays that can support themselves under a large fraction of G.

[kfsorensen]

I see that the plan is to use NTR. Might one hidden reason for NASA's insistence on building its own EDS be that this would give them the in-house expertise to build a large stage as a precursor to building an NTR stage? Would there be much synergy?

Not just NTR likely bimodal NTR and when you are not operating in high thrust mode and engines can operate as a power reactor.

Bimodal NTR solves issue with tracking the sun while the ship is spun for artificial G and you no longer have to design solar arrays that can support themselves under a large fraction of G.

Bimodal NTR is nonsensical.  You can say you want it but that doesn't mean you can.  I've never seen a core design for BNTR that wouldn't be a complete joke to a nuclear engineer.  You might as well put 100% efficient solar arrays on the vehicle--it's about as real.

[DLR]

Why shouldn't a BNTR work?

You basically use the reactor to heat a working fluid, only that the working fluid isn't propellant but a gas which you run through a turbine to produce power.


A couple of points on the DRM 5.0:

- 9 Ares V, are they kidding?

- Why only Oxygen production?

- Why Orion for the MAV? It's heavier than it needs to be.

From DRM 3.0 which used 6 Magnums (equivalent to 3 Ares V) to 9 Ares V, that's insane!

For me DRM 5.0 is nothing but a desperate attempt to create an artifical commonality between the Lunar and a Mars programme.

[mmeijeri]

Ammonia and even hydrazine are apparently plausible propellants for an NTR, though with only half the Isp of hydrogen, which would still be impressive. I sense another opportunity for noncryogenic depots. SEL-2 staging and an earth swingby can help you avoid using NTR, but even if you do want it, you don't need an HLV or cryogenic fluid transfer.

[Archibald]

NTR ammonia = 600s
NTR LH2 = 800 s

 

[A_M_Swallow]

NTR ammonia = 600s
NTR LH2 = 800 s

 

What is the Isp of NTR carbon dioxide?

CO₂ is 95.72% of Mars's atmosphere and with a boiling point of -57 °C, 216.6 K, -70 °F ((at 5.185 bar)) is easy extract using ISRU techniques.

[A_M_Swallow]

Ammonia and even hydrazine are apparently plausible propellants for an NTR, though with only half the Isp of hydrogen, which would still be impressive. I sense another opportunity for noncryogenic depots. SEL-2 staging and an earth swingby can help you avoid using NTR, but even if you do want it, you don't need an HLV or cryogenic fluid transfer.

If you are in orbit STR could be used.  Mars transfer vehicles simply need bigger mirrors.

Other possible propellants include CO₂, nitrogen, oxygen and argon.

[Kaputnik]

Out of depth here but AFAIK a good rocket propellant contains lots of hydrogen or something else that's very light. Ammonia is OK because it contains some H. Hydrocarbons are obviously alright. But C and O are both much heavier than H, hence I presume a lower exhaust velocity, lower isp.
I may be completely wrong, but that's how I understand these things work.

[mmeijeri]

Out of depth here but AFAIK a good rocket propellant contains lots of hydrogen or something else that's very light. Ammonia is OK because it contains some H. Hydrocarbons are obviously alright. But C and O are both much heavier than H, hence I presume a lower exhaust velocity, lower isp.
I may be completely wrong, but that's how I understand these things work.

I vaguely remember the idea was that since delta-v isn't too high you can make do with lousy Isp as long as you have ISRU fuel. And CO2 is plentiful on Mars.

[Archibald]

Ammonia and even hydrazine are apparently plausible propellants for an NTR, though with only half the Isp of hydrogen, which would still be impressive. I sense another opportunity for noncryogenic depots. SEL-2 staging and an earth swingby can help you avoid using NTR, but even if you do want it, you don't need an HLV or cryogenic fluid transfer.

If you are in orbit STR could be used.  Mars transfer vehicles simply need bigger mirrors.

The more I look at them, the more I like thermal arcjet thrusters.

Arcjet little tricks is that, amid the varied electric propulsion systems (hall, Ion, resistojets) it is the most similar to chemical -  higher thrust / lower ISP.

http://ntrs.nasa.gov/search.jsp?N=0&Ntk=all&Ntx=mode%20matchall&Ntt=SP-100%2Barcjet

Interestingly you can obtain a 1000s ISP from an ammonia arcjet.
 
A solar-electric / ammonia arcjet looks like a decent compromise between chemical (heavy) , NTR (nuclear), and electric (slow) propulsion systems.

From chemical it keeps the "usual" propellant, ammonia.

From NTR it keeps the 800-1000s ISP

Being an electric propulsion system it has a reduced fuel consumption.

And, icing on the cake, ammonia is easy to store... and you have this haber process for Mars ISRU (I have submitted this latter idea to criticism here http://www.newmars.com/forums/viewtopic.php?f=4&t=7902)

[Cbased]

With the recent changes surely we need some (serious?) updates in the architecture in the area of the LVs.
Has anyone heard anything?

[Ben the Space Brit]

With the recent changes surely we need some (serious?) updates in the architecture in the area of the LVs.
Has anyone heard anything?

I wouldn't be surprised if the recent ULA-designed parallel cluster that stages out of EML-2 becomes DRA 6.0.

[JulesVerneATV]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

[Eric Hedman]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

[Robotbeat]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

[Eric Hedman]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

I'll start with what I think is a big issue, ECLSS systems for Mars.  I will start with a paper from 2017 that lays out why reliable ECLSS systems for mars will be much more difficult for Mars by Harry W. Jones of NASA Ames titled "Developing Reliable Life Support for Mars".  There is also a huge difference between designing these systems on Earth and testing them in an attempted closed loop on the Moon or Mars to find out if it really works well in field conditions.  The paper can be found here:  https://ntrs.nasa.gov/api/citations/20170010347/downloads/20170010347.pdf

The next issue is finding out how well a large pressurized rover will work on Mars if you want to go beyond safe walking distance from a habitat.  All rovers previously sent to Mars have been much smaller extremely slow moving vehicles.  That's not hardly a good test for the durability and reliability needed for Mars in a cold dusty environment.  Both a rover and a habitat need a hatch that will be exposed to dust and maintain a seal through repeated operations in the very cold dusty environment.  The Toyota Lunar Cruiser will most likely work out on the Moon most, but not all issues a rover will face on Mars.  We would find out what kind of maintenance would be needed to keep a large heavily used rover running before it is sent on a nine month voyage.  All I know is the first time you do anything in engineering you get surprises you never expected when you put things into operation.

Nobody is well into the design phase of a Mars habitat.  Considering the pace of development of things this complicated, I see it taking in the order of 8 to 10 years to have anything ready to launch if the go ahead was given today.  We know even SpaceX misses project schedules by years so we're looking at mid to late 2030s for launching habitats unless someone has been building and testing hardware in secret to fit what is needed.

A habitat on Mars needs to be designed with anticipating the needs for followup expansion.  Nobody has done this kind of work at the level of detail required.  What kind of power grid is going to connect the habitat to solar or nuclear sources.  Should it be plowed in underground?  Has anyone started designing the equipment to do it?  Is there going to be a standard for plumbing, water and sewers, to connect facilities together?  Unless the first habitat modules are going to be disposable while the standards get worked out, this will take time.

We know how to start and build cities on Earth to be functional and efficient because we have learned what works over thousands of years.  We have no such experience with the Moon or Mars.  It we be a whole lot easier to get the experience on the Moon before committing to designs for Mars that may go down a bad path.

While I'd like to see humans headed to Mars sooner rather than later.  I highly doubt that humans will be going before the middle of the next decade at the earliest unless NASA, SpaceX and the crew want to take Apollo level risks.  WHile lots of the technology needed should be an extension of things that have already been done, you will be practically guaranteed that some big things will pop up that you don't expect.  Taking things forward in more manageable steps usually gives you a higher chance of success.

[lamontagne]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

I'll start with what I think is a big issue, ECLSS systems for Mars.  I will start with a paper from 2017 that lays out why reliable ECLSS systems for mars will be much more difficult for Mars by Harry W. Jones of NASA Ames titled "Developing Reliable Life Support for Mars".  There is also a huge difference between designing these systems on Earth and testing them in an attempted closed loop on the Moon or Mars to find out if it really works well in field conditions.  The paper can be found here:  https://ntrs.nasa.gov/api/citations/20170010347/downloads/20170010347.pdf

The next issue is finding out how well a large pressurized rover will work on Mars if you want to go beyond safe walking distance from a habitat.  All rovers previously sent to Mars have been much smaller extremely slow moving vehicles.  That's not hardly a good test for the durability and reliability needed for Mars in a cold dusty environment.  Both a rover and a habitat need a hatch that will be exposed to dust and maintain a seal through repeated operations in the very cold dusty environment.  The Toyota Lunar Cruiser will most likely work out on the Moon most, but not all issues a rover will face on Mars.  We would find out what kind of maintenance would be needed to keep a large heavily used rover running before it is sent on a nine month voyage.  All I know is the first time you do anything in engineering you get surprises you never expected when you put things into operation.

Nobody is well into the design phase of a Mars habitat.  Considering the pace of development of things this complicated, I see it taking in the order of 8 to 10 years to have anything ready to launch if the go ahead was given today.  We know even SpaceX misses project schedules by years so we're looking at mid to late 2030s for launching habitats unless someone has been building and testing hardware in secret to fit what is needed.

A habitat on Mars needs to be designed with anticipating the needs for followup expansion.  Nobody has done this kind of work at the level of detail required.  What kind of power grid is going to connect the habitat to solar or nuclear sources.  Should it be plowed in underground?  Has anyone started designing the equipment to do it?  Is there going to be a standard for plumbing, water and sewers, to connect facilities together?  Unless the first habitat modules are going to be disposable while the standards get worked out, this will take time.

We know how to start and build cities on Earth to be functional and efficient because we have learned what works over thousands of years.  We have no such experience with the Moon or Mars.  It we be a whole lot easier to get the experience on the Moon before committing to designs for Mars that may go down a bad path.

While I'd like to see humans headed to Mars sooner rather than later.  I highly doubt that humans will be going before the middle of the next decade at the earliest unless NASA, SpaceX and the crew want to take Apollo level risks.  WHile lots of the technology needed should be an extension of things that have already been done, you will be practically guaranteed that some big things will pop up that you don't expect.  Taking things forward in more manageable steps usually gives you a higher chance of success.

Although a lot of discussion has taken place in these very pages, no actual work for Mars life support has taken place (as far as we know) because there will be none needed, unless SpaceX completes Starship.  No Starship, no Mars base and no Mars expansion.  So Spacex is focussing on Starship.
Otherwise we can indeed take a few decades to study all this, and in good time, when there is enough interest and financing about, detail design work and experimentation will be done.  Life support can be tested on Earth more easily than on Mars or the Moon, after all.  And with significant robotic presence and energetic equipements with sufficient power (MW rather than watts) Mars can be explored and most important items tested with no risk to humans.

[Coastal Ron]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

...
Both a rover and a habitat need a hatch that will be exposed to dust and maintain a seal through repeated operations in the very cold dusty environment.

I think dust management and seal maintenance will be HUGE issues for both the Moon and Mars, and since the dust is different in significant ways on the Moon vs Mars, what we learn on the Moon won't translate well to Mars.

Also, the scale of what Musk wants to do on Mars vs what NASA is likely to be funded to do on the Moon means that Mars issues need to be addressed as quickly as possible, since the supply lines for Mars will be so much longer and harder to support if the right parts are not there when a seal goes bad.

[lamontagne]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

...
Both a rover and a habitat need a hatch that will be exposed to dust and maintain a seal through repeated operations in the very cold dusty environment.

I think dust management and seal maintenance will be HUGE issues for both the Moon and Mars, and since the dust is different in significant ways on the Moon vs Mars, what we learn on the Moon won't translate well to Mars.

Also, the scale of what Musk wants to do on Mars vs what NASA is likely to be funded to do on the Moon means that Mars issues need to be addressed as quickly as possible, since the supply lines for Mars will be so much longer and harder to support if the right parts are not there when a seal goes bad.

Sealing should be testable with robots and experimental set-ups?  Just sealing the robots themselves is something of a catch 22! (hum, my cultural references are geting old...)
We really need significant power sources on both the Moon and Mars to get things tested quickly and effectively.
So before humans, robots.  I don't think this was possible when the reference architecture 5 was written in 2009.

[Robotbeat]

Apollo managed to do this just fine, with no prior experience, for Apollo 11, and then multiple times later for multi-day missions. And the MER and MSL and Perseverance rovers (as well as various landers) have some instruments amount them that require a seal and have decades of surface exposure among them.

Starship also is fairly removed from dust compared to the rovers due to its height. It has an elevator and a garage that can be used for dust mitigations as well as two airlocks (Apollo had none).

So no, sealing is not a showstopper for early missions. We know at least as much as Apollo, and if there is a problem, EVAs can be limited.

Life support is a similar story, but we also have decades of experience on ISS plus the MOXIE demonstration making oxygen from the atmosphere and just the sheer mass of Starship enabling simpler (Apollo-like) life support solutions.

So life support is also not a showstopper.

These are engineering challenges, and doing proper engineering even for things well understood is still a challenge, but for an initial mission, none of these are showstoppers at all.

[Ariane7]

NASA emphasizes role of the moon as testbed for future human Mars missions
https://spacenews.com/nasa-emphasizes-role-of-the-moon-as-testbed-for-future-human-mars-missions/

This article touches on issues being totally ignored by people who want to go to Mars right away.  Nobody has developed all the technology needed to survive on the surface once you get there.  Developing this technology will not happen overnight.

Like what, for example? Be specific.

...
Both a rover and a habitat need a hatch that will be exposed to dust and maintain a seal through repeated operations in the very cold dusty environment.

I think dust management and seal maintenance will be HUGE issues for both the Moon and Mars, and since the dust is different in significant ways on the Moon vs Mars, what we learn on the Moon won't translate well to Mars.

Also, the scale of what Musk wants to do on Mars vs what NASA is likely to be funded to do on the Moon means that Mars issues need to be addressed as quickly as possible, since the supply lines for Mars will be so much longer and harder to support if the right parts are not there when a seal goes bad.

https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/The_toxic_side_of_the_Moon

Harrison Schmitt said lunar dust was like hay fever.

[zubenelgenubi]

https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/The_toxic_side_of_the_Moon

Harrison Schmitt said lunar dust was like hay fever.

I highly recommend nasal rinses. 👃

[Coastal Ron]

Apollo managed to do this just fine, with no prior experience, for Apollo 11, and then multiple times later for multi-day missions.

Apollo 17 made the most excursions to the lunar surface, and that was a grand total of three. So probably six total opening and closing events for the Lunar Module. Hardly a test of the long term effects of lunar dust on seals.

If people are going to be living on the Moon or Mars, then expect the main hatch to be used multiple times day, for weeks and months. And that is just the hatch seals. What about dust removal for human health needs?

Mars regolith is toxic, due to relatively high concentrations of perchlorate compounds containing chlorine. So there will need to be a decontamination process, or systems that provide for a separation of humans from Mars material. That could be a suit design that allows an exit from a covered hatch on the rear, not unlike the Russian Orlan spacesuit, but that suit was not design for "docking" so it would have to be more elaborate. Is that being worked on?

And the MER and MSL and Perseverance rovers (as well as various landers) have some instruments amount them that require a seal and have decades of surface exposure among them.

We are talking human needs, so I have no idea how robotic rovers need intersect with human needs. Yes, we have learned quite a bit, but that is about how to keep robotic systems going on Mars, not humans.

Starship also is fairly removed from dust compared to the rovers due to its height. It has an elevator and a garage that can be used for dust mitigations as well as two airlocks (Apollo had none).

Fair point, but:

1. Climbing up and down a Starship is a short-term situation, until permanent housing is constructed at or below ground level. I'm really thinking about the more permanent housing needs.

2. Maybe you are assuming that being above ground means less dust blowing in? Not sure that was the issue, since dust clinging to suits is the bigger problem. However Mars dust does blow around, so even being above ground won't reduce the chance of dust blowing into an open hatch. That would not happen on the Moon...

So no, sealing is not a showstopper for early missions. We know at least as much as Apollo, and if there is a problem, EVAs can be limited.

Again, for Apollo the most they went outside was three times on a mission. For Mars missions the crew will be on the surface for what, a year or more, right? BIG difference.

Life support is a similar story, but we also have decades of experience on ISS plus the MOXIE demonstration making oxygen from the atmosphere and just the sheer mass of Starship enabling simpler (Apollo-like) life support solutions.

I thought we would be further along on having better environmental control and life-support system (ECLSS) technology by now, but our experience on the ISS shows that we don't have reliable ECLSS that could be used for Mars today, for the trip to/from Mars, and then being on the surface. More work needs to be done on that...

These are engineering challenges, and doing proper engineering even for things well understood is still a challenge, but for an initial mission, none of these are showstoppers at all.

For the Moon, which is days away, no. No showstoppers. But for Mars, which is 6-9 Months away, but only in certain launch windows, meaning a trip of about 2 years, I don't think we are close to being there yet. Not with any level of confidence.

[sdsds]

Regarding dust mitigation for airlock seals, what about tear-off protective film layers? Automobile race teams do this for windshields.
https://protintshop.com/collections/frontpage

[Robotbeat]

1) perchlorate hazard is vastly overstated.
2) space is absolutely not the only place that has needed to have airtight seals in the presence of dust or other debris.
3) it is actually okay to clean stuff off before going through an airlock. You don’t HAVE to expose the airlock itself to massive amounts of dust. A mud room to brush off dust is already part of the design of Starship HLS.

I’m a little disappointed in some of the seeming inability to think of fairly practical solutions to dust and airtight seals. This is something that has been solved to various degrees by makers of wooden barrels since ancient times and watertight ships’ doors since the 1800s (and pressurized aviation, etc, yeah, even in deserts where dust might exist).

[lamontagne]

1) perchlorate hazard is vastly overstated.
2) space is absolutely not the only place that has needed to have airtight seals in the presence of dust or other debris.
3) it is actually okay to clean stuff off before going through an airlock. You don’t HAVE to expose the airlock itself to massive amounts of dust. A mud room to brush off dust is already part of the design of Starship HLS.

I’m a little disappointed in some of the seeming inability to think of fairly practical solutions to dust and airtight seals. This is something that has been solved to various degrees by makers of wooden barrels since ancient times and watertight ships’ doors since the 1800s (and pressurized aviation, etc, yeah, even in deserts where dust might exist).

Absolutely.  Almost all NASA airlck designs I've seen just use the Mud room paradigm, or the two stage airlock, to control dust.  I like the aircraft example as well.  It's not an airlock just because there are not two doors in sequence and no pump down sequence, but it's a great start for one.

[Eric Hedman]

Has anyone considered the possibility of disposable coveralls over space suits to keep them clean from dust in the first space.  3M makes protective Tyvek bunny suits to cover workers going into messy environments.  If you had a spacesuit partially or fully covered and you just tear that covering off before you go in, couldn't that mitigate the majority of the dist and dirt?

[BN]

Has anyone considered the possibility of disposable coveralls over space suits to keep them clean from dust in the first space.  3M makes protective Tyvek bunny suits to cover workers going into messy environments.  If you had a spacesuit partially or fully covered and you just tear that covering off before you go in, couldn't that mitigate the majority of the dist and dirt?

this could help if done in the mud room, and those can likely be easier to clean than a fully dusty suit.

is tyvek the best material for this? it does seem to be light, tear-resistant and slippery..


if this becomes a thing, expect some very wrinkly looking astronauts

[Twark_Main]

Has anyone considered the possibility of disposable coveralls over space suits to keep them clean from dust in the first space.  3M makes protective Tyvek bunny suits to cover workers going into messy environments.  If you had a spacesuit partially or fully covered and you just tear that covering off before you go in, couldn't that mitigate the majority of the dist and dirt?

this could help if done in the mud room, and those can likely be easier to clean than a fully dusty suit.

is tyvek the best material for this? it does seem to be light, tear-resistant and slippery..


if this becomes a thing, expect some very wrinkly looking astronauts

"Toughness and flexibility are retained down to the glass transition temperature of HDPE (-100 °F [-73 °C])."

https://www.dupont.com/content/dam/dupont/amer/us/en/microsites/tyvek-design/images/documents/EN-NA-Tyvek(r)-Graphics-Printing&Technical-Guide-2018.pdf


" Tyvek® is not considered UV resistant and we do not recommend Tyvek® for applications where constant sun exposure is expected."

https://www.dupont.com/tyvekdesign/design-with-tyvek/dupont-tyvek-faq.html


When I've talked about "Tyvek" anti-dust suits in the past I just use the name as a stand-in for some suitable analogous space-rated material.

Is flashspun Kapton a thing?? 

[Robotbeat]

Nomex would work.

[lamontagne]

Nomex would work.

Can we make tires out of Nomex?  Or flexible membranes for the airlocks? Or as a fibre and we would need a filer anyway, and that would break  down in the cold?
Did the Lunar rover need steel wheel due to the cold on the Moon, or the cold transportation temperatures?  How much heating would allow a tire to remain flexible, therfore allowing flexible tires on the Moon and Mars, rather than the rather akward steel mesh designs?

[Eric Hedman]

Tyvek breaks down under typical UV light for outdoor applications on Earth if coated properly in 4 to 6 months of continuous exposure.  Does anyone know how UV intensity on the surface of Mars compares with Earth?  It would be interesting to see what its life would be given how often astronauts would be going out on the surface.  Tyvek is also extremely light in the range of 1 to 3 ounces per square meter depending upon thickness.  So even if disposable, it might not be too big a deal if astronauts could get 20 r 30 uses out of each one.

[BN]

Tyvek breaks down under typical UV light for outdoor applications on Earth if coated properly in 4 to 6 months of continuous exposure.  Does anyone know how UV intensity on the surface of Mars compares with Earth?  It would be interesting to see what its life would be given how often astronauts would be going out on the surface.  Tyvek is also extremely light in the range of 1 to 3 ounces per square meter depending upon thickness.  So even if disposable, it might not be too big a deal if astronauts could get 20 r 30 uses out of each one.

uv exposure is much higher on mars. it's likely to be an issue over time for a range of equipment. don't expect any snazzy paint jobs to hold up on mars.

Nomex would work.

Can we make tires out of Nomex?  Or flexible membranes for the airlocks? Or as a fibre and we would need a filer anyway, and that would break  down in the cold?
Did the Lunar rover need steel wheel due to the cold on the Moon, or the cold transportation temperatures?  How much heating would allow a tire to remain flexible, therfore allowing flexible tires on the Moon and Mars, rather than the rather akward steel mesh designs?

UV would be an issue for rubber tires and for nomex. nomex is more of a fabric than a structural material anyway. stainless steel mesh is probably the best option, although even those would require somewhat frequent replacement. (carry a spare) no need to reinvent the wheel again.

[DanClemmensen]

UV would be an issue for rubber tires and for nomex. nomex is more of a fabric than a structural material anyway. stainless steel mesh is probably the best option, although even those would require somewhat frequent replacement. (carry a spare) no need to reinvent the wheel again.

Nomex and Kevlar are in the same chemical family (aramids) and synthesizing them on Mars will be approximately the same difficulty. They are both sensitive to UV and need to be protected, usually by coating. Nomex and Kevlar are also sensitive to abrasion. Kevlar is stronger and more flexible than steel, which is why it replaced steel in radial tires.

[Robotbeat]

Yeah, UV coatings are feasible.