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I have lots of experience designing, repairing, and operating piston and turbine engines on a lot of weird fuels. But, I cannot imagine using a slag-forming reaction (from burning tri-silane with atmospheric CO2) inside anything with moving parts. I just do not see how it could survive the grit and other solids for more than a few seconds. Blades, valves, pistons, makes no difference.
On the other hand, a device without moving parts could survive such abuse, so long as one you periodically (or continuously) get rid of the slag buildup inside. I also have decades of experience with ramjet engines, so that does come to mind. Not the ones with the baffle or colander flameholders, the simple dump combustors, which had wider flameout limits here on Earth, anyway.
I'm not sure how any "air"-breathing engine could ever produce useful power relative to its weight on Mars, because the atmosphere is so thin. Nor am I sure that airplanes would ever be practical there, for the same reason. But, under the assumption that low engine cycle pressures and high wing loads can feasibly be addressed, one might consider a ramjet airplane with a rocket booster for planetary transport on Mars.
Use the tri-silane or some other fuel with some oxygen in a separate rocket motor to takeoff and accelerate to supersonic-type ramjet speed, generally Mach 2-ish here on Earth, probably similar there. Then switch to tri-silane (or magnesium powder) burning with Martian atmospherioc CO2 in the ramjet (and shut the rocket down). You cut all power to decelerate and glide to landing, with some reserve rocket propellants to support go-around or divert.
I picked the supersonic-inlet ramjet variant because the performance potential is much higher (higher cycle pressures in the engine) than the subsonic variety. This plus other extraordinary design measures would be needed to counter the disadvantage of the extremely thin "air" there. This is still subsonic combustion, though, not "scramjet", which simply is not yet ready for prime time. Flight speeds will be in the Mach 2 to Mach 4 range quite easily.
Air transport on Mars? Maybe. That "air" is awfully thin. Engine thrust and power, and wing lift, will be more-or-less proportional to atmospheric density (as a ratio to here: pressure ratio .006 times molecular weight ratio 1.57 divided by temperature ratio something like 1.2, for .0079). The weights to be moved are proportional to gravity's pull (as a ratio to here: 0.38 gee). Power to weight, and wing loading, will be more or less in density/gravity ratio to here: 0.02.
It'll be 50 times harder than here to get decent power out of an airbreathing engine, and 50 times harder than here to balance structural weights against wing lift required to fly. Very tough to engineer.
GW
Standard military weapons-release speed is 485 knots indicated. At sea level, that's about 0.85 Mach. Definitely subsonic at all low altitudes of any interest. Condensation clouds can exist in the intake of a jet parked static on a carrier deck.
I tried ballutes as a stabilizing drogue back in the mid 80's. Ribbon chutes worked better, and were good to 2.5 Mach, if you bagged it properly for control of opening shock. Different application, same decelerators.
These were ram-air inflated devices, though. In space, you are really talking about low to medium-pressure forced inflation of a shaped balloon. Not quite the same thing. It was the ram air inflation I found unreliable, unlike a ribbon chute.
GW
As regards artificial gravity, I think you'll find we actually do have some idea of what spin rates are tolerable. Aircraft and early astronautic work defined it. That boundary is a bit fuzzy, but 4 rpm seems to be a good rule of thumb for a top rotation rate.
What we don't know is how much gee is enough. That research has never been done, and I for one do not trust people's lives and health to surrogate studies like enforced bed rest. It's just not the same.
Our only direct experiences are at 1 gee and zero gee, with the result that in zero gee bad things start happening to the body that cannot really be reversed, after somewhere in the vicinity of a year. Again, a fuzzy boundary.
Most missions to Mars involve a one-way transit time of 6-9 months, plus some extended stay on the surface. Total mission times are around 2 years. Mars has 0.38 gee, but we have no data whether that's "enough gee", precisely because those studies were never done in a spinning lab in LEO.
So, it looks to me like it's one full gee at no more than 4 rpm. Period.
That's a 56 meter radius. If you build the vehicle long and narrow and put the habitat on one end, you can just spin it end-over-end for gee. De-spin for maneuvers. Easy. No battlestar-galactica, no extended space truss structures, no complicated cable-connected anything.
Think around a dozen-and-a-half to two-dozen docked 30-50 ton modules, mostly propellant tanks, each one around 5 m diameter and 15-20 meter long, or something in that vicinity. 1 full gee at way under 4 rpm. I'd put a Skylab-like module up there for 6 folks, at one end, and a NERVA-type nuclear rocket on the other. (We know how to build those engines, by the way. They all but flew 4 decades ago.)
The "Skylab" could be 3 or 4 inflatables docked together. Just provide lots of open space inside, in which to live sanely for several months at a time.
Don't count on ISRU return propellant on the first trip, it's an untried technology as yet. Losing a crew is simply more "expensive" than carrying the return propellant with you. It is crucial to design-in a "way out" for the crew at every single phase. These people must return alive if there is ever to be another trip.
You can send the landers and their propellants and surface supplies separately, and then rendezvous in LMO with it when you get there. It's the surest way, one we already know works. "KISS" is how to ensure it all works.
So, we're looking at assembly of a small "fleet" in LEO. We know how to do that, we built the ISS that way.
Once you're in the shuttle payload range of 25+ tons, it no longer really matters very much what the module size is. What matters is cost per kg delivered to LEO. With Falcon-Heavy up to 53 tons priced at about $2000/kg, what do we need with a big, expensive government rocket development anymore?
Just thinking out loud, and trying to raise some very pertinent questions.....
GW
I was not so very much a fan of X-33's 8% structural inert fractions. Turns out I was right: those propellant tanks fractured under their own weight, when stood on end.
I am very much a fan of very low ballistic coefficients/wing loadings for re-entry. I like the idea of an extension of the venerable old Piper Cub as a re-entry vehicle. Absorbing BTU's is easy. High skin temperatures is not.
Sort of poetic justice, in a way. I rather like stick-and-rudder flying. I learned to fly in a Piper J-5, if anybody knows what one of those is.
GW
There will always be a need for paper. I don't care how "electronic" we get, you will always have to have a permanent storage medium for critical data.
And, nothing will ever replace toilet paper.
If bamboo is good for those uses, then so be it.
GW
Actually, it could be done, with a better buoyancy-defining density ratio there than here. At equal pressures and temperatures otherwise, gas density ratio boils down to molecular weight ratio. That's 2 (for hydrogen) vs 28.97 (for air here) vs 44 (for CO2 there). Mars density ratios are about 50% better.
From a practical standpoint, I would worry about the envelope's survivability: plastics have a very short life on exposure to UV, which is very harsh on Mars. You won't be able to build this dirigible (or balloon, or blimp) out of aluminum. Too heavy. Just like here.
Even here, hydrogen explosions are less of a risk than most folks suspect. The Hindenburg would have burned and crashed, even if it had been filled with helium. The forensic data (confirmed by old insurance records) suggest that the real culprit was static-spark ignition of the doped fabric skin. That dope was nitrate-base (a monopropellant explosive/pyrotechnic), and was pigmented with a mixture of aluminum powder and iron oxide (which is today known as thermite!!!!). The hydrogen just added a little to the yield of the fire. But the flame propagation speed along the Hindenburg's skin was around 10 times what fully-premixed hydrogen-air is capable of. And it wasn't even pre-mixed.
The ONLY real problem with a smallish hydrogen-air flame here on Earth is that you can't see it in full daylight. But, on Mars, you won't even have one at all in a CO2 atmosphere.
From a design standpoint, the real design problem with a Martian dirigible/blimp/balloon is that the material-of-construction weight only scales down by 0.38 (for the strength of gravity), while actual gas densities scale down by 7mbar out of 1013, roughly. A dirigible/blimp/balloon on Mars will have to be very much larger in proportion to its useful payload there, than here.
But, yes, it could be done. And safely.
GW
quote:
"Musk seems to have several things going for him: (1) a team of dedicated young engineers who want to succeed; (2) the luxury of looking at the big picture and figuring out the cheapest, easiest way to do it, without lobbyists asking to fund their special big rocket or Congressmen insisting on expenditures in their district. Musk also seems to have good instincts about what near-term technological innovations to pursue and which need to wait."
There you went and put your finger squarely on what is wrong with NASA, and what will eventually afflict ESA, JAXA, and all the rest: a government program in which tactical details (not just overall strategy) are political footballs. This went wrong for NASA in the 1970's, and they have accomplished no significant large exploration objectives since. The ones they have accomplished have all been robotic, and all have been the subject of drastic political fighting in Congress.
Let that be a lesson to all my non-US correspondent friends.
If anyone can break this deadlock, it will be Musk. But I have my doubts he can single-handedly pull off a manned Mars mission that really leads anywhere. That's because he only has the resources to fly there maybe once or twice. And, (here's the real problem) the "exploration" isn't yet done. There is a capstone exploration mission with men that you simply cannot do with minimalist mission designs. You do not need "Battlestar Galactica", but you cannot do it with one Dragon full of 1-6 men, either.
The key is limiting your government legislatures to ONLY strategic objectives. Forbid them EXPLICITLY from dictating tactical details. It is likely way too late for the US & NASA, but ESA and JAXA might still stand some chance if this is done.
This is important because most corporations DO NOT function like Musk's Spacex: they will not invest in anything unless there is demonstrable short-term profit. Mars will not show profit for a long time yet. (Sorry, but it it just won't. To expect otherwise is simply not realistic.) Neither did the Roanoke colony. Even Jamestown was a financial loss for a long time.
You have to focus on what government can do best and on what corporations can do do best. There's less overlap than most folks believe. The "smarts" lie within the corporations, not the government labs. But corporations only do speculative things if a government will pay them to do it. Chicken-and-egg......
Once you get by that conceptual hurdle, you can design practical missions to the moon, Mars, NEO's, even to the stars.
But NOT until you take that hurdle into account. Sorry.
That's about 500 years of our history talking, not me.
GW
Yep, it matters.
Days or weeks or months of micro-acceleration are incompatible with the delta-vees one computes under the impulsive (pretty near zero burn time) assumption.
GW
"Lower heating if decelerating at higher up" is really lower peak skin temperatures at lower ballistic coefficient. The total integrated BTU's (KW-hr) absorbed over the trajectory is actually higher in that case, but that's an easier problem to solve than high skin temperatures. Control of survivable gees is the real key to how this trajectory is selected.
For a winged vehicle here on Earth, a "ballistic coefficient" is better expressed as "wing loading", which is vehicle weight divided by wing planform area. To obtain the benefit of earlier deceleration higher up, this needs to look more like a small light aircraft (10-20 lb/sq.ft) than the shuttle or a jet fighter (100-200 lb/sq.ft). Peak skin temperatures are under 2000 F, which ceramics, or very, very, very heavily-cooled Inconel-X, can survive. Better odds on the ceramics.
For a space capsule here on Earth, it is vehicle weight divided by heat shield broadside area. This has typically been about 4 times the shuttle/jet fighter range (400-800 lb/sq.ft). These vehicles punch very deep into the air before they slow significantly. Peak skin temperatures (stagnation point, leading edges) is around 3500-4000 F. That's why Shuttle had ablative carbon-carbon leading edge and nose cap pieces, and why Mercury, Gemini, Apollo, and Dragon had/have ablative phenolic composite heat shields.
PICA-X on Dragon (and the other new capsules) is actually nothing but a modernized version of the 1960-ish vintage silica-phenolic, which is really nothing more than what the old capsules used in the 1960's and 1970's.
Think about it: if you can actually achieve such a low wing loading/ballistic coefficient (around 10-20 lb/sq.ft), you could survive re-entry here on Earth (from orbit) with a steel truss "airframe" and a ceramic fire-curtain cloth skin, as long as there was some sort of insulating standoff between the frame and the skin, and some sort of ventilation inside to absorb the BTU's. In other words, a ceramic fabric-skinned variant of a Piper Cub might actually be a feasible re-entry vehicle from LEO.
Anything that might work here would work on Mars. The heating there is less demanding. I see some experiments that need to be done here!!!!
GW
The original topic was wind power on Mars. The maximum achievable energy capture of a windmill I once read to be around 59% of what kinetic energy rate (kinetic power) there was in that portion of the wind stream tube intercepted by the mill. I don't remember how that limit was derived, but no real windmills actually recover that much. Sort of like a Carnot engine in thermodynamics, you can't really build anything quite that good.
Now, the KE rate (kinetic power) of a windstream is essentially 0.5 mass flow rate * velocity squared. Mass flow rate is density*velocity. So the kinetic power available is 0.5*density*velocity cubed. You will recover about half or so of 59% of that stream power in a good mill; say about 25%.
Density on Mars is quite low relative to density on Earth, and wind speeds are comparable. So the velocity-cubed factors are similar there and here. Temperatures are colder on Mars, which act to increase density by inverse proportionality, while pressures are lower, which act to decrease density in direct proportion. Say 233K there versus 288K here, and 7 mbar there compared to 1013 mbar here.
The density ratio there to here is then (7*288)/(1013*233) = 0.0085 or thereabouts. Wind power potential there is a bit less than 1% of wind power potential here, at similar speeds. Twice the speed there vs here would give you power potentials 8 times higher (about 6.8% of here).
Myself, I'd be looking harder at solar PV, solar thermal, and nuclear, than wind. The "air" is just too thin there.
GW
VASIMR is a variation on the ion drive. All the electric propulsion schemes, including VASIMR, will have vehicle accelerations measured in milli-gees or less. Some much less. The burn is definitely not a short impulsive burn, by any standards.
If your burn is impulsive, meaning delivered over an extremely short time, not a large percentage, relative to travel time, then you have no gravity losses relative to what we normally compute for the rockets and orbits we are familiar with.
Minute acceleration levels make you burn through a large percentage of your travel, incurring gravity losses during the entire burn. Your effective specific impulse is nowhere near as high as you would compute from a bench or static test.
These electric things do help quite a bit on very long trajectories, but the shorter the trip, the "crappier" they look relative to plain old high-thrust, very-impulsive rockets. Mars is not far away enough for it to look good. Itokawa was.
GW
My engineering intuition suggests that trailed drag devices won't be very effective, because of "shadowing" in the wake of the main vehicle. Even if the tow cable were miles long, this effect would still obtain, we've seen it in the persistent ionized trails the space shuttle left behind during its re-entries.
To make a towed drag device effective, it would have to be wider than than the wake left behind by the vehicle, which is somewhat wider than the vehicle itself. That means you are looking at some sort of conical ring-shaped ballute inflatable. Anything in the middle shadowed by the wake is ineffective as a drag device. But it would be inherently dynamically stable to use such a towed drag device.
I haven't go a clue how to build such a device, but it would need every bit the same heat protection as the vehicle itself, and so would its tow cable, being immersed in incandescent plasma. That's a very harsh environment for all known materials. Interesting idea, though. Certainly deserving of tests.
It would be rather smart to include test articles on ferry flights to ISS, and release them for test coming home.
GW
Quote:
"Once we have a basic energy, industrial and agricultural infrastructure in place, follow up missions would be relatively cheap."
You just made my pessimistic point.
None of the mission plans I have ever heard of since 1956 was planned to establish anything like useful infrastructure of any kind. Since the 60's, it's been flag-and-footprints with 1-12 men, and usually only one vehicle making a single landing.
One or two limited-objective missions is all that the government(s, all of them) will ever do. Until there is at least some infrastructure on Mars , business will not go. Chicken-and-egg.
Except maybe Elon Musk. He bucks the trend, and resembles the more adventurous companies of about 5 centuries ago in what he wants to try.
Hope springs eternal.
GW
Those are all good ideas.
Actually, doffing and donning a compression glove in a multipiece MCP rig is not all that hard. It's like donning thin tight rubber gloves, then pulling a zipper up the back of your glove to increase the compression.
For most purposes, there would be little need to doff the compression gloves. These are about as supple as wearing thin tight rubber gloves down here. But, if I was trying to install a bunch of tiny machine screws with a dinky little screwdriver, or tap a drilled hole down in the 1/16 inch range or smaller, I might have to doff the gloves, given safe handling temperatures.
GW
For nuclear engines, I have often said in other threads that the best place to test such things is on the very near-by moon. Testing any kind of rockets requires a stable thrust stand where you wring it out before you ever consider flying.
Solar PV power is possible in large sizes. The shuttle bay was 65 feet long (about 20 m). The insides of those doors were a solar array, rated at a max of 25 KW. That's now an older design, but it still gives you a notion of the size of the thing vs its power. (The second layer of door panels was the waste heat radiator.)
I quite agree that the politicians are completely perfidious and behave nonsensically with respect to space, to nuclear, or to any other science or technology issues one cares to name. They won't change until we hold them responsible for what they have done, and have not done.
GW
For a rocket-burn landing, that's what we did on the airless moon. It's exactly the same as a gravity-turn ascent, just done in reverse.
Now, on Mars, there's enough atmosphere to be a heating problem, both ways. What speed you will be going when you hit atmosphere depends mostly on the altitude of your parking orbit. So, park fairly high to reduce speed at entry.
Hit the sensible atmosphere well into your gravity-turn-in-reverse trajectory, at speeds well below the orbit speed. You'll do canted burn with assistance from heat shield aero drag, then canted burn with assistance from a parachute (or series of chutes) once you're below about M2.5-ish. Then canted burn to touchdown. I think that's what they're really going to do with one-way Spacex Dragons on Mars.
The point is to use aero drag to reduce the thrust required during what is otherwise a continuous-burn descent. Reducing thrust reduces propellant demand. It's not a huge effect, but every bit helps. There's no such help during ascent, but there is also no need to cant the engines. Even during descent, once the hypersonics are over, there is no need to cant the engines. Straight-axis thrust eliminates the cosine loss.
Now, the instability of straight-axis thrust with the jet straight into the oncoming hypersonic stream is a real problem. Whether computer-controlled attitude thrusters can cope with it, well, some experiments need to be done. My intuition suggests it is possible, but your attitude thruster system needs some real force to it. If it could be done, the need for canted propulsion engines during descent disappears.
For the delta-vees needed to do this job on Mars, either as a one-way descent vehicle, or as a two-way lander, "reasonable" mass ratios and the rocket equation generally seem to rule out chemical Isp's, except as staged vehicles. What is "reasonable" for mass ratio? Well, that depends on whether the vehicle is to be used once, or many times.
What we are used to building is one-shot throwaway rocket stages, for which inert fractions in the 8-10% range seem feasible at this time. Maybe a tad higher for those with heat shields and landing legs, say 10-15%.
A reusable vehicle, on the other hand, needs to be tougher than an old boot in order to take the abuse of repeated spaceflight entry conditions (and they are very abusive, even on Mars). I would point to airplanes, which are very reusable flight vehicles. Transports and bombers for decades have been in the range of 40-50% inerts. So was the X-15 rocket plane (40% inert).
The lander we are discussing in this thread is not an airplane, and likely has no wings at all. It's a different structure. But I would hazard a guess that a reusable "landing boat" vehicle would have an inert fraction closer to the 20-25% range than anything we've seen in prior rocket vehicle designs. It's simply not strong if the material isn't there. And that material has a weight to it.
So, that's what brought me to the nuclear rocket technology for a single-stage two-way Mars landing boat: about 20% inerts puts you into a simple tradeoff of payload fraction vs propellant fraction. At Isp 400-class, I couldn't solve the problem single stage. At Isp 1000-class, I could, and with an out-of-plane capability to boot. That's solid-core nuke, something we know we could build, because we did it before.
Now, in my design study, I did not cant the engines, I only had one. But I could have used 3 or 4 small ones instead. Those could be canted slightly on descent at a cosine loss, and gimballed straight on ascent. I'd fire through the heat shield from near center. It simply lays out better as a big conical vehicle that way, with a cockpit near the tip of the cone, away from the radioactive stuff.
Anyhow, that's my two cent's worth.
GW
I think I'd take the bikes and a big rover with a drill rig on it, pressurized or not. But I'd go with MCP suits, either way.
I'd completely divorce the vacuum protection from all the thermal and mechanical protection. The MCP rig is just vacuum-protective underwear plus a gas breather helmet. You wear then ordinary coveralls, ordinary hiking boots, ordinary leather work gloves, an ordinary wide-brimmed hat (on top of the helmet), or whatever is required. Doff what you don't need, whenever circumstances warrant.
With an MCP suit made of separate pieces (one-piece union suits make little sense to me since they hold no gas pressure), if dirt temperatures are between around -10C to 45 C, you can doff the work gloves, and the compression gloves, and thus handle dirt and rocks absolutely bare-handed on Mars (or in deep space) for up to about 10+ minutes at a time. That limit requires you re-don the compression gloves before swelling (tissue edema) sets in. The old experiments seemed to show significant pain and swelling in hands, starting around 20 minutes of exposure to vacuum.
Can you imagine being able to do fine electrical, plumbing, or mechanical assembly work in LEO with a suit like that? All you need is an unpressurized bay inside a an enclosure, with enough lighting power to bring the workpieces up to a range where you can touch them barehanded without frostbite or burns (-10 to 45 C).
Wow!
GW
Oops, sorry if I insulted somebody. Didn't mean to.
I'm already very sure the crudely-45 degree canted Super Dracos will work during entry anywehere, because the thrusters on all the capsules and shuttles we ever flew worked. Effectively, they're canted thrusters, too, just different angles. It's only right into the airstream that's unstable.
Somebody asked why you couldn't reduce velocity before entry. You can, it just costs a lot of propellants. With chemical rockets, the Isp and practical mass ratios limit you to using as much aero deceleration as you can get. With solid core nuclear, you just begin to get into the regime of Isp at which you can reduce velocity before entry, and still maintain a decent mass ratio.
Advanced gas core nuclear concepts do even better, but we never built any of those, just solid core. And we quit even that in 1973, right before we were to fly them. The guys who did it are mostly dead now. But I met 3 survivors last August. They're in their 80's now. The "engineering art" dies with them.
Solid core nuclear is enough to rocket-burn to landing from low Mars orbit, and still rocket-burn back to orbit, in a single stage vehicle of "reasonable" mass ratio. In other words, we could build a single-stage, re-usable "landing boat" out of that technology!
Send one lander and a lot of propellant for it, and make many landings with it, refueling in orbit after every trip. I was looking at 10% payload, 20% inert structure and equipment, and 70% propellant (liquid hydrogen), for the round trip, at 30-degrees out-of-plane maneuver both ways! 60 ton lander, 6 ton payload. Wow!
Do you like that prospect? I sure do.
GW
RobS:
Sure, the canted thrusters will work. That idea worked very long ago for the tractor rockets of the escape towers on Mercury and Apollo, and also for parachute delivery of very heavy items like tanks, with last-second rocket braking. It was the Soviets who actually fielded this parachute/rocket braking.
If one is using a descent trajectory that involves at least some rocket braking (so you can steer arbitrarily) during the hypersonics, then precision landings become possible, regardless of the atmospherics. The missing piece is a radar transponder to home-in on. Once a first landing at any given site has been made, that is how one precisely guides subsequent properly-equipped vehicles down to exactly the same site.
GW
I am guessing that, in part, that is why the Super Draco thrusters on Dragon are canted roughly 45 degrees off axis. You "heat shield it" partway through re-entry, then burn to make sure you're down to around Mach 2 (that's a ribbon chute limit, it's actually closer to Mach 2.5), deploy a chute, then chute plus thrusters to land. Or just thrusters to land.
Dragon is a one-way vehicle to Mars's surface like that, so we're likely talking unmanned probe or cargo carrier. The canted thruster plumes avoid most of the hypersonic instabilities you spoke of.
The other reason they are canted is for launch escape service on the manned version of Dragon. Match made in heaven. I like well thought-out systems.
GW
Louis:
I sort of disagree about the living space requirement. Bigger really is better, ask any prisoner who ever served time in solitary. But, inflatables really make the best sense, provided access to the pressure shell is unimpeded by the equipment inside. You have to be able to patch leaks very quickly. There have been some hints about cramped living from the old Salyuts, Mir, and even the ISS. But not from Skylab. Too little space we already know is very bad from Gemini 7: 2 weeks of a 3 week plan nearly cracked that crew up (I know that was really, really, really cramped, though).
I agree with using a modular transit vehicle. I had slightly-modified Dragons as crew return vehicles in the mission design in my paper last August, at the Mars Society convention in Dallas. My transit vehicle was a stack of propellant modules, a nuke propulsion module, a 3-part habitat module, and two crew return Dragons, for a crew of 6. It was a long stack, so you could spin it end-over-end rather slowly for artificial gravity. (The landers went to Mars with all the landing propellant as separate vehicles. They were single-stage, reusable nuclear.)
GW
Josh:
The MIT design is being forced to achieve a design target of 1/3 atm compression. They cannot meet that goal yet.
But they could easily meet Paul Webb's 190 mm Hg level.
The 1/3 atm goal (about 253 mm) is unrealistic given the materials we have, and further, it is unnecessary, given what is actually needed for life support (actually a bit less even than Webb's 190 mm, you only really need somewhere between 152-190 mm.)
GW
Practicality of a supple MCP suit? Yep. We already know it works.
Look at the 1969-vintage video of Paul Webb's elastic spacesuit tests way back then. The test subject was riding a bicycle ergonometer (at high effort level) for an extended period of time in an MCP rig, in a vacuum tank, at a simulated 87,000 feet (way above the "vacuum death point" for an unprotected human). He was sweating right through the MCP garment into vacuum, so he needed no cooling system other than his own biological one.
Webb did that with a breathing helmet and tidal volume bag, a bag restraint jacket, pure O2 at 190 mm Hg total (absolute) pressure, and a garment made of 6 layers of the then-new pantyhose material. The whole rig, including a liquid O2 supply, weighted 85 pounds total. Most of that was the helmet and O2 backpack.
Yeah, we can do this. We could have done it years ago. We could have done it decades ago.
GW
Falcon-heavy will launch 50-53 ton payloads to LEO from Canaveral. We built the ISS with 15-25 ton payloads in the Shuttle. Assembly is not a problem. Cost will be, once the payload size threshold for practical assembly (25 ton) is crossed. Falcon-heavy is projected at $800-1000/pound of delivered payload.
Do you really think a government heavy-lifter will ever be that cheap? (I don't.)
If so, please tell me why, when shuttle was $1.5 billion for 25 tons. And Delta-4 is way above the competition curve between Atlas-5 and the Falcon family. Falcon is the better choice, by the way. I posted that data on "exrocketman" a little while back. It's a strong function of payload size, but flattens some as you get into the 20 ton + range.
If not, then why do we need an expensive 100-ton lifter when 2 cheap 50-ton lifters will do the same job?
GW
The reason I asked the questions I did is the history of government behavior re: space since the space race ended with Apollo 11. You don't get to do what's smart because no one wants to spend the money. You actually get to do very little in the way of missions.
Private corporations are largely even worse: they invest in nothing that's not near-term profitable. Musk's Spacex launcher business is exactly that. His Mars dreams are the exception to the rule. I cannot name one other.
I rather suspect the US government (probably partnered with the others) will support 1, or maybe 2, trips to Mars with men, and that will be it. No more. Period. All else is fantasy.
The prospecting and resource development you spoke of, and the real exploration that makes it possible (that I keep yammering about), will have to get done in those 2 missions, or else no one will ever have the necessary info to successfully locate a survivable settlement! You can't turn over rocks peering down from an orbiting robot, that's just not good enough.
We do not have the resources or the opportunities to go there and do these things in too-small a way on each mission, because there won't be enough missions to get it all done that way. It's going to have to be just about all-or-nothing, on each mission.
A smart plan responding to a financial squeeze like that would be a multi-landing exploration on the first mission, based from orbit. The more sites (identified from all these probes) the better, and concept prototypes for ISRU also get tried out as experiments. That was the gist of my paper at the Mars Society convention in Dallas last August.
The second mission visits the best one (or at most 2) sites, as verified from the first mission, but is based on the surface, located at that one site or two. That mission does the heavy-duty prospecting and tries out engineering-prototype ISRU equipment identified as promising from the first mission.
Then, later, if "somebody" decides to fund a permanent base or settlement of some sort, it'll be the best one of those sites verified by the second mission. That's about where Musk might jump in, in the lead role. And if he is successful, others might follow. But the governments will not. They never have. Never will.
"Cassandra has spoken" (and her news is never good)
GW