Human Exploration of Mars Design Reference Architecture 5.0

[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.