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This is too expensive to be another space race. That way lies flag-and-footprints nonsense, not the start of a base or colony.
GW
If rubber cracks, try leather. I never heard of leather cracking in the cold. Oops, you need MCP done as vacuum-protective underwear to use leather boots.
The visor problem is more intractable. Sounds like layers to me. The inner one is warm enough to provide a seal even if the outer layer cracks in the cold. At least you get to go back inside. Some of the snow goggle materials used at South Pole Station might be worthy of consideration. The latest record cold there is -136 F (-93 C).
GW
Quaoar:
You just made my point.
Of course the sabatier reaction is well known science. Of course it has been used Earthside for a long time. None of that is machinery we can use on Mars. It was designed for Earthly conditions.
My point is that the actual machinery necessary to make it work on Mars has never been designed at all, much less prototyped and tested. That includes the power supply and whatever gas compression machinery they finally select (not at all a trivial problem with an inlet density 0.6% of that here). All those missing support items are part of my point.
I'm not saying at all that it cannot be done, because it so very clearly can. And I hope it is, and soon.
But, I am saying that the necessary things to make it work reliably on Mars are not underway at all. It has to work very reliably at Martian conditions before you ask astronauts to bet their lives on it. Proving that your specific design actually works reliably takes time, effort, and money. It's called "engineering development" work.
There is a vast difference between a lab device that demonstrates feasibility, and an engineering prototype that verifies this thing will really work reliably. It's called engineering development, and not many scientists understand its nature, or how big an effort it really is. They were not trained in it. That's what engineers are trained to do, which is why there are two distinct titles: scientist and engineer.
Typical development, properly done, is at least one order of magnitude more effort, time, and expense, as any scientific feasibility demo imaginable. Sometimes 2 or 3 orders of magnitude. But really talented engineering teams can do it for about 1 order of magnitude.
You don't really find talented, efficient teams like that employed by the "big space" firms. Those guys usually cost you the 2 or 3 orders of magnitude.
GW
I would have put a 300-series stainless steel tire on that aluminum rim.
300-series stainless is what they use for cryo-propellant storage tanks here on Earth, because it will handle the cold better than any other known material, bar none.
It is tough in the sense of a huge elongation to failure (as steels go). It is unaffected by corrosive chemistry to a great extent. And any steel alloy beats the crap out of aluminum for resistance to rock impact.
But then, I am an engineer, not a scientist. Must have been some reason they did what they did. Just nothing I can comprehend.
GW
My point isn't either-or, it's how-much.
We have lots of experience with rocket engines and manned rocket vehicles, dating back to at least the ME-163 in WW2, and a whole lot more with the X-planes at Edwards AFB in the late 1940's through the late 1960's.
We have a lot of experience with capsules and heat shields, dating back to the original Mercury and Vostok flights in the early 1960's, and the warhead entry vehicles before them in the 1950's.
We have lots of experiences with landers and rovers (and landing legs) dating back to Surveyor 3 in 1963, and all the Apollo landings, plus all the Mars landers since.
The combinations of these things that will work at Mars for a manned landing is unique, but at least all the tinkertoys from which the Mars landers will be made have long histories behind them. It's that history that gives you some confidence for betting lives.
That unique combination for the Mars lander is something for which I do not see any ongoing development. That disturbs me, but there is still time to get that done. I do not see any of the space agencies anywhere addressing this, though.
The transit vehicle will have to be designed around keeping a crew healthy and sane for a roughly 2.5 year round trip. I see only some of those things being addressed by any of the space agencies. That disturbs me very greatly. There is so much to do, and not so very much time.
In both cases, the strategic decision-making is lacking, that function being usurped by politics-of-money.
The one item we have been discussing here with little-to-no history behind it (so far) is propellant manufacture on Mars. That is why it is risky: no history behind it. Zubrin's bench-top lab device is not a proper prototype for something we could test, nor are the other similar devices. We need to build and test those prototypes. Now. Yet, no space agency anywhere is doing more than academic lab stuff. That kind of thing just doesn't qualify as an engineering prototype test.
So far, based on the activities underway, I see no space agency anywhere that really intends to send men to Mars. None of the things that must happen are happening.
On the commercial side, there are a very few visionaries willing to take part. Spacex is one, but they have some tinkertoys to offer, not a whole picture, at least not yet.
The other private initiative is that Tito fly-by with a married couple. That's 500 days in zero-gee without radiation protection to shame the government agencies into actually doing something. Almost, but not quite certainly, it's a suicide mission. If the radiation doesn't kill them, the free-entry gee loads will, after 500 days of the effects of zero-gee disease accumulates.
Personally, I like the idea of ISPP. But, it needs some real engineering prototyping and test history before we bet lives on it. If we don't have that history, then you take it along and test it for sure, but you don't bet lives on it, you send the return propellant. If you have an engineering prototype test history behind it, then you can bet lives on it. Basic ethics.
GW
That aerospike effect is what the retro-plume stability thing is about. Doing an aerospike in reverse, the plume has to reverse somewhere, but to which side does it bend? That bend induces side loads the attitude controls must be able to handle. If that plume bending flip-flops around from one side to another, unsteadily, you can tumble the vehicle. It drives you to a much more powerful, authoritative attitude control.
The idea behind cant outward is to start that retro-plume reverse bend in a particular direction. That way it doesn't flip-flop around, and your attitude control is an easier design. The only real question is how much cant is enough to stabilize the idiot thing?
A few easy cold-gas jet tests in a cheap hypersonic wind tunnel could answer that well enough to permit a successful design. That design could be flight-proven in suborbital entry tests here, then verified for the final probe or two we send to Mars, before we use it to land men there.
But, we'd better get on with it. If the landing is about 20 years from now, there's not much time left to get all that done. Tougher yet if we accelerate to a landing only 10 years from now, but still doable. 5 years? Hard to get a good job done (test on 1 probe, if any).
GW
Oops. Aluminum wheels may not have been the best choice for a long-life nuke rover. News stories today indicate unanticipated rates of wear attributed to rough ground.
Everybody who has ever hiked around in the mountains knows how rough that kind of ground can be. Not sure whether weight or cost drove them to aluminum wheels, but I'd bet that team is regretting that choice now.
GW
To answer Josh's question in post #17 above: the evolutionary pressure to re-expand from underground onto the surface always exists. The surface conditions may (or may not) be too harsh to permit it. On Mars, it appears that surface conditions may currently be too harsh. I do not know whether the radiation, the chemistry, or the near-vacuum air pressure (that forces water to vaporize away) is the worst, but the combination of those three is rather daunting for life on the surface.
As for the form-of-iron discussion: life finds a way to utilize what is there, as long as too-harsh conditions don't prevent it. Underground on Mars is not as harsh as the surface. Buried ice does not sublime, liquid water might even be stable given some heat. Radiation is far reduced, down to nil the deeper you go. Subsurface chemistry is different from surface chemistry here, so probably there as well; it's just that we won't know how it differs until we go there and drill deep.
GW
My question: "I think that governments (plural) will fund one (and only one) manned mission to Mars, if any at all. Do you agree with that assessment of the politics-of-money?"
GW
Nobody will know until somebody looks inside rocks from way more than a meter underground, with something way better than a magnifying lens. Here on Earth, there are single-cell creatures that live in the pores of deep rocks. That kind of life may well outweigh all of the life on the surface, no one yet knows. If our surface environment were to "die" the way Mars's evidently did, those underground microbes would still be there.
GW
edit 12-21-13 to "single-cell" from "single-"
I kinda like outward for what I guess would be better flip-flop stability. The vehicle sort-of "looks like" a concavity to the oncoming flow. This would also act to increase the "effective" diameter by extending the region disturbed by the jets.
Those effects acting together would seem to me to increase the drag. But all of that requires some wind tunnel testing to confirm. For blunt objects, you only need to exceed Mach 3 to get into "hypersonics", where the shock envelope size and shape is pretty much independent of the actual Mach number.
When I was a student there long ago, UT Austin had a Mach 5 wind tunnel with a 5-inch by 7-inch test section. It was fairly cheap to use. The answers we all seek on this issue could be resolved reasonably quickly with a clever model in that wind tunnel, and for likely well under $1M.
GW
An MCP suit done as vacuum-protective underwear would not need any liquid-cooling undergarment, because you just sweat straight through your permeable compression underwear. No snorkel needed in the space helmet, unlike current designs, because there is no liquid to leak. Wear the same kind of outer clothing that you wear here, for each environmental condition that you face. Hot, cold, abrasive, impact hazards, etc. Fix tears with duct tape instead of dying. Why "they" never got serious about this, I cannot understand.
Artificial gravity cannot and was never intended to counter radiation diseases. You do shielding for that. There is a little shielding from metallic structures in the spacecraft, but your water and wastewater tanks offer a whole lot more. 20 cm of water takes out the solar flare risk and cuts much of the cosmic ray risk by a factor approaching 2. I don't understand why these are still issues, just do it.
As for artificial gravity, a = r*w where a = acceleration, r = radius from cg, and w is the spin angular velocity. For numbers, ratio these: 1 gee at 56 m and 4 rpm. Bear in mind that untrained civilians seem to tolerate 3, perhaps 4, rpm just fine. Also bear in mind that spinning a baton-shaped vehicle end-over-end is both stable and a very easy and convenient way to get large radii out of otherwise very practical designs. And with docked modules, it is easy to reconfigure your same baton length at each mission step, no matter how many propellant tanks you shed. It's all in how you choose to stack them up.
GW
"What exactly is the problem with making methane from carbon-dioxide and water?"
Technically - not a lot. Although, it is a very long and expensive way from a desktop scientific demonstration device to something that makes mass quantities reliably in the (very hostile) field.
Ethically - betting lives on gear that you simply don't have a lot of experience with, is a real problem. Why not take both the propellants and the propellant-maker on that first trip? If it works, you get to fly to more places. If not, you still get home.
GW
Sure would be nice to get some ground truth on that site, wouldn't it? If it really is buried massive freshwater ice, then that is a very inviting site.
GW
For the vehicles in my proposal, I did the departure and arrival burns without staging-off any empty tanks. The only staging is leaving empties in orbit at Mars, and returning home on propellant tanks dead-headed to Mars. This two-burn approach increases the number of required modules, yes, but it also allows you to recover and reuse every single scrap of hardware. These propellant modules I assumed to be 5% hardware and 95% propellants.
GW
In my ancient Hoerner drag "bible", there is NASA-generated data for a single centerline jet in Mach 2 retro-propulsion on a Mercury capsule shape. It acted to reduce drag by a factor between 1 and 2, dependent upon the massflow magnitude of the jet. This test ignored retro-plume flip-flopping instability.
If you put multiple jets around the periphery, I dunno what happens to the drag. Increase, decrease, who knows? The Super Draco thrusters on Dragon are fitted like that. They are canted at roughly 45 degrees, so that their nozzles point through the aftershell, not the heat shield itself. Cant angle ought to put the kibosh on plume instability.
How much cant is needed for stability? No one knows, I suspect. My intuition and wind tunnel experience suggests that 10-15 degrees would work. But I dunno for sure. Without repeatable data, I doubt anybody knows. Yet. But at least some folks are looking at it.
GW
I very much doubt that multicellular life could have evolved on Mars. There wasn't enough time before it salted-up/acidified/went dry/went cold. Only about 1 B yrs was available before it all went south. Evolving multicellular life apparently took almost 3 B yrs here.
That being said, I would be very surprised that single-celled life never happened on Mars. In fact, I would bet it's still there, underground.
From what I read, there was some sort of microbe that helped precipitate the iron out of the ocean here as the banded-iron formations, around 2 B years ago. Combination of geology, chemistry, and biology. Although, being an engineer not a biologist or a scientist, I might have misunderstood what I read.
GW
Hi Quaoar:
What I had in mind was a ship composed of docked-together modules, most of them propellant modules. The ship will be lighter on the return, and will need fewer propellant modules than it did outbound, but it will still need a lot of propellant. By stacking them up properly, one should still get a baton on the order of 150 m long.
Go see the mission plan I just posted over at http://exrocketman.blogspot.com a couple of days ago. Fig 19 shows a sketch of what I had in mind. Bear in mind that my design proposal recovers and reuses the manned vehicle in Earth orbit at the end of the mission. It's not a one-shot free return design.
Isn't Quaoar the name of a dwarf planet discovered recently in the Kuiper belt? It sounds familiar.
GW
From what I read, the galactic cosmic radiation (GCR) varies with sunspot cycle, every 11 years. Minimum GCR at solar max is 24 rem/year, and maximum GCR at solar min is 60 rem/year. NASA astronauts currently have a limit of 50 rem/yr.
We don't violate that limit by very much at all, worst case, and stay well under it most of the cycle. Close to max exposure, one starts bumping into career limits with younger astronauts if the mission runs over 2.5 years. And that doesn't take into account the half-sky shielding effect of the planet for the approximately 1-year stay at Mars, nor the slight shielding effects of spacecraft structures (admittedly very slight). Nor does it consider atmospheric shielding at Mars, which is more effective than any of us had hoped. But, the crew that makes this trip doesn't need to fly one like it again.
Radiation that kills is more likely a big solar flare event. The worst of these only needs about 20 cm of water for an effective shield. Any craft on a 2.5 year voyage will have water and wastewater tanks. You just wrap them around your designated shelter zone. The smart designer would make that the flight control station.
Radiation as a reason not to go to Mars is an canard and an excuse. We've known what has to be done for a few decades now. And we have known how to do it for those same decades now.
GW
RobertDyck is largely correct in his assessment that without an ISPP demo (meaning on-site on Mars), we can't use it on a manned Mars mission. But, that's IFF lives are to be bet upon it.
If not, then we don't have to have a separate demo, we can do the demo while the men are there. If it works so much the better. If not, well, at least we have data with which to fix it.
RobertDyck says without ISPP the mission is simply too expensive. Maybe, maybe not. NASA simply does not have a good track record planning for men to Mars. It wasn't very long ago their flags-and-footprints mission was priced at $450B.
And, as near as I can tell, they still have no working efforts to incorporate spin gravity, radiation shielding with water/wastewater, and a decent non-restrictive spacesuit, nor are they paying much attention to the living space issue for a 500 day mission, much less a 2.5 year mission.
Yet many of us here on these forums have posted outlines supported by calculations for better mission plans than anything we have seen from NASA, and many of these price out in the $10-100B class. Not the $0.5T+ class. I think the $10B plans are too close to "flags-and-footprints", but that's just my opinion.
The one I just posted over at "exrocketman" is nearer $100B, but is way-to-hell-and-gone more than a "flags-and-footprints" mission: multiple landings plus the start of a base all in one trip. It could be done factor 2-to-4 cheaper with nuclear, but I think I'd rather go right now with in-hand chemical. I think NASA and DOE would botch any resurrection of nuclear thermal rocketry.
Why this wide disparity between our $10-100B plans and NASA's $0.5T plans exists is possibly a good question for Zubrin, I dunno. He knows more about DC politics-of-money. I'm just a very, very, very experienced engineer.
GW
Hmmmm. Mobile hab driving around. Interesting notion! Have to stay away from rough ground, though. Will need huge balloon tires, spares, and a good way to change them.
Spacenut: my lander has no parachutes, it simply does rocket braking to touchdown, once the hypersonics of the entry process end. The crew control cabin is an abort capsule on top that works the same way, being something similar to the Red Dragon design concept. The heat shields could be either low-density PICA-X, which could be used many times at Mars orbit entry conditions, or it could be low-density ceramic composite, with a potentially "infinite" service life. Either way, the limiting factor for vehicle service life is not likely to be the heat shield, unlike here at home.
One of the two big reasons I went with LH2 not methane is that any permanent base will need local water for life support, anyway. You don't want to establish a base at any site without it. The other reason was far higher payload fraction capability in a single-stage, two-way vehicle.
In my opinion, those two reasons together make solving the problems of compressing, liquifying, and storing LH2 worthwhile. That doesn't preclude making methlox, of course, because it is likely there will be vehicles that use it, too. I just didn't have one in my posted plan.
GW
The US Army has done experiments with walking machines, inspired actually by the good results they previously had with pack mules. Walking machines are very difficult to implement on anything but a paved floor, but, if implemented successfully, they can go where wheeled vehicles cannot. It's a very rough-country application. Your other choice is a vertical takeoff/landing flying machine, and even that gets restricted by a suitable landing spot.
GW
I think it's a fine idea.
GW
I think an inflatable module for a crew habitat is fine. You do need a rigid structure to take the spin-up /spin-down loads with exciting a bunch of unwanted vibrations. If this structure is your propellant tankage, that fills the bill very nicely. I rather doubt an inflatable boom would e rigid enough for this. To reach 1 full gee, you need a radius of 56 m from center-of-mass, at about the max credible 4 rpm.
GW
Hi Josh:
I think you got the gist of what I did just fine, except that I'm not really against ISRU/ISPP. My emphasis was on ISRU/ISPP trials, just not bet-your-lives dependence upon them, because any of a number of things can go wrong, all of which can be site-dependent. It's risky enough as it is.
This is dependent upon the propellant combination you select, of course. The only risks I see with methlox is having to bring the hydrogen (no local water), and can we make enough tons fast enough to be useful? That's just not done with a "desktop device". Making LOX-LH2 should actually be easier, once you actually find the water. Massive buried ice would be fairly easy to mine. The rover needs a blade on its front, as well as a drill rig on its rear. Dunno whether to try pit mining or extraction by melting up the well. Have to try both, I suppose.
I went with LOX-LH2 propulsion, because the payload fraction I could achieve was 14%, vs 5% with LOX-LCH4. That makes a huge difference in the size of the lander, for a fixed payload (79 tons vs 200+ tons, same payload). Making LOX-LH2 in situ merely requires a local source of ice, something any base or colony will have to have, anyway. Anywhere you can do that, you can also make methlox, and you don't have to bring the hydrogen.
I hadn't thought about going suborbital from site to site, except as an adjunct to orbit-based exploration of very widely separated sites (4000+ km apart?). That would be fueled by in-situ propellants.
What I had in mind was one crew of 3 on the surface with the other 3 in orbit as the "safety" watch. I'd have to think about how that might work with extensive suborbital flight available, and how much equipment gets displaced with a longer run of supplies. I think it'd work, though. Any bird capable of full entry is more than capable of suborbital entry, that's no problem.
One of things you can do with your manned vehicle in low (or any other) orbit is continue spin gravity. That way, no crew gets debilitated by more than a month or two's exposure to low gee. What I couldn't do was squeeze enough performance out of a lander to match orbits with a manned vehicle in a high-apogee orbit.
I actually went through three studies this size, the first two of which were based out of an ellipse apogee'd at Phobos's orbit. The maneuvering propellants required to get the lander to a low orbit where it could function more than ate up the capture and departure savings of the high apogee. Didn't seem to matter how I arranged it, I lost more than I could gain. And that's with LOX-LH2. LOX-LCH4 was completely infeasible for trips like that.
What I finally came up with nets 6 landings with 3 landers, to the surface, plus one trip to Phobos, and the core of a base established at the site with the most accessible ice deposits. You build one manned vehicle in the vicinity of 650 tons in orbit, and you get to reuse it on other missions. You have to build 3 unmanned ships (pushed by your landers), all in the 1000 ton class. Everything but the lander assembly is nothing but docked modules. There's only 4 kinds of modules, so this will be a lot easier than building the ISS was. That's an awful lot of bang for order-of-magnitude $100B, even if ISRU/ISPP fails completely. If it works, you explore more sites before setting that base.
I tried using my usual suspenders-and-belt-plus-armored-codpiece way of thinking for this. That way, the mission succeeds, almost no matter what else happens. That's the only real difference between my plan and the others.
GW