The Case for Mars

Great Debates
21

Certainly, we should delay going to Mars until we’ve gathered as much data robotically as we can; but if the day ever comes when a robot is the functional and true intellectual equivalent of a well-trained, creative human being – well, we’ll probably be to busy putting down the revolt of our robot slaves to be colonizing Mars.

Wasn’t ‘Cavorite’ what they used to explore the moon? They couldn’t carry enough of anything to make it all the way to Mars; anyway, I think Lionel Jefferies is dead. Good reference to a Hammer film, though.

Why would we want to ‘colonize’ an asteroid or coment when Mars is obviously much more ‘terraformable’ and has a nice, stable orbit that doesn’t bring its surface temperature within spitting difference of absolute zero for most of the time?

I’ve always wondered why we don’t exploit Earth-crossing asteroids for a ‘free’ ride to Mars. Using the two phase approach someone has previously mentioned, we can send a robot ship ahead with all necessary supplies and fuel-generators. There are literally hundreds (maybe thousands, at last count I believe I heard about 2100) of such
asteroids that have already been detected, with more being found every week. If you stop to think that even in the Space Shuttle, we’ve demonstrated the ability to fly for millions of miles, the sphere of available space around the Earth is huge, so the asteroid doesn’t even necessarily have to come all that close.

So, as the asteroid passes close to the Earth on the way out (we having brilliantly plotted its future course to show it coming close to Mars), and we send out a mission to hitch a ride. One advantage: if we miss on the hitch, the ship’s course can be plotted to bring it back to Earth fairly fast. Assuming we catch it, we have a nice, big asteroid to do productive research on while the trip takes place, instead of a lot of people floating around looking out the window getting depressed and homesick as the Earth fades to the rear, and finding various ways to twiddle their thumbs until Mars comes up. Also, we have a nice asteroid to mine for various substances like nickel, iron, molecular substances of all kinds.

Then, we just have to be damn sure there’ll be an available asteroid to ride home on; or else, that the one-way trip home will be a lot easier to make – as always, life support will be the big stumbling block. Could be, though, that the asteroid itself will help solve that problem.

Also, the single best reason to colonize the moon or Mars is to assure the survival of the species in the event of a planet-killer asteroid strike.

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DIF…cavils and comments on your asteroid post:

I was under the impression that the origin of Cavorite as a fictional anti-gravity-producing substance was from a H.G. Wells story back around the turn of the (20th) century. Don’t remember seeing it in any film use.

Someone (Arthur C. Clarke?) had pooh-poohed the idea of “hitching a ride on a comet” (with “asteroid” interchangeable with “comet” for these purposes, though I think we’re all clear on the real differences). The general idea was that since a space vehicle able to rendesvous with a comet/asteroid headed for Mars orbit was already on a free-fall orbit that would permit the rendesvous, it was already on (or nearly so) a free-fall orbit that would take it to Mars, and nothing would be gained by making the rendesvous, since the delta-V needed to make the rendesvous would be (virtually) the same as to make the flight without the rendesvous.

However, you have made one clear and obvious point that had, so far as I know, escaped Clarke(?) and everybody that has repeated that argument since: that on such a long trip, there would be both scientific, resource-availability, and human-values reasons for using a passing asteroid as a “base in transit.” Nice work!

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Polycarp, I’ll reply more after I get back from lunch. I knew about the Wells’ reference to Cavorite. They made a movie of it back around 1964 (IIRC), with Edward Judd, Lionel Jefferies, and (IIRC) Martha Hyer. First Men in the Moon, IIRC. Should be easy to find on the IMDB.

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Polycarp and DIF are BOTH right…Cavorite was an anti-gravity substance, an invention of a British scientist named Cavor (duh) in H.G. Well’s novel THE FIRST MEN IN THE MOON. It was filmed in 1964, not particularly well, with Lionel Jeffries playing the Cavor role and a coupla never-weres as the Romantic Interest.

– Uke, miffed at mixing the moon and Mars.

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Damn. Sorry for the redundancies, DIF. I was so excited about answering PolyC that I skimmed right over your last post.

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Hitching a ride on an asteroid isn’t going to do you any good. You have the mistaken idea that position is important. It’s really not. It’s all about the energy required to translate from one orbit to another. So you burn a bunch of fuel to match orbits with the asteroid, then it gets to Mars and you detach… and you’re still in the asteroid’s orbit. Now you have to burn a bunch of fuel to get into Mars orbit. Unless the asteroid’s orbit is already the optimum transfer orbit to Mars, this will cost you more fuel than just flying there on your own.

27

Whaaat the fuck was thaaa–!!!

Damn, Ike, thought I’d just had the first SDMB UFO sighting, and it just turns out to be you!

Polycarp:

Hope you won’t mind the redact.

I apologize, Poly, for having somewhat misled you with words like “hitch a ride”. What I have in mind would involve intersecting orbits which would bring a mission vehicle close to the asteroid briefly, but not entail matching full velocity with it. I was trying to think of an analog situation over lunch, and I think I hit on one, if you’ll pardon the obvious differences.

Imagine a kid on skates standing at the crest of a hill on a paved street. By himself, with a bit of an assist from gravity, he can get going about 10 mph. But he wants to latch onto the city bus, approaching at 25 mph. He gets himself going and, as the bus rushes past, he makes a very carefully planned throw with a grappling hook that lands perfectly inside the bus’s bumper. Now, if that was all, when the tether on the hook played out, the kid would jerked off his feet, signifying mission failure.

But (and it may be a big but, but someone else will have to do the finer math) let’s suppose that, instead of just rope, the kid has a very elastic bungee cord instead. Without trying to draw the analogy too perfectly, as the cord plays out, the kid readies himself, and when the jerk comes, the cord begins pulling him, but only gradually, so that the kid can adjust to the speed and begins accelerating. Gradually, the bungee cord recoils, pulling him forward faster and faster, but never so fast that he loses balance. Also, once he’s going, the kid begins reeling in the cord until he’s up with the bus’s bumper and can grab on.

You see where I’m going? The mission ship’s orbit would be a big loop that would bring it back to Earth if the ship failed to catch the asteroid. The ship throws out a huge aramid fiber net in space in the path of the asteroid – let’s say the asteroid is as big as 10-story building. Let’s also say the cord on the net is initially 10 kilometers long, but can stretch to 200 before stopping. So those aboard the ship have time to adjust to the admittedly sudden change in direction because the instantaneous delta-V is relatively small; it’d probably still be in the range of 6-7 G, but bearable.

On the way out, assuming the asteroid is the correct type, the crew mines the asteroid for nickel and iron, using a solar furnace. The nickel they attach a rocket to, and put it in a parking orbit over Mars. As they approach, they plant an explosive which separates them, along with a big chunk of the rock, from the main body of the asteroid. As final approach nears, they break the chunk of rock up and start throwing it off AFAP to the front, reducing their momentum and reducing the amount of aerobraking they’ll eventually need to do.

Cavils?

28

dhanson: nope, for the reasons just given.

29

Sounds to me like it would work, and save on needed fuel, in the unlikely event of having an asteroid on the appropriate orbit. I say unlikely because it is not enough to get from Earth to Mars’ orbit, but to the particular point on that orbit occupied by a rather small red planet at the time.

30

DIF…What I meant by exploiting other heavenly bodies was that we could get the basics (water) etc. from comets, asteroids etc. without having the expense of getting them into space.

Therealbubba

31

Here I go dragging the science discussion back over to literature…humanities major, he humbly apologized.

This getting dragged off the planet on an asteroid is reminding me of the OTHER 19th century SF writer everyone knows, Jules Verne, and his novel HECTOR SERVADAC. Sometimes known in English as OFF ON A COMET.

A chunk of Earth gets ripped off by the tail of a passing comet, and the group of assorted Europeans left on board have to deal with the fact that they’re now scooting all over the solar system. One of Verne’s most virulently anti-Semitic novels, and also one where he gives free rein to his distaste for the Germans and the English.

Traveling around space on the tail of a comet? I sure as hell never understood the Science in THAT one.

Uke

32

Polycarp, I see what your saying; but are you really aware of just how freakin’ many of these things there really are? Also, a couple of things occurred to me after that last post. First (assuming a nickel-iron asteroid) the nickel would represent a fabulously valuable lure for further expeditions if it was left in Mars orbit. Perhaps even a robot mission would be sent just to attach a large enough rocket engine to the nodule to nudge it into a orbit toward the Earth (but, safely bypass the planet if no one made the catch). The iron tailings coming off could be formed into hollow cylinders or rings and shot out with an electric mass-driver. As far as getting to the ‘particular point’ you mentioned – it occurred to me that, once the asteroid has been used to provide the delta-V necessary for shortening the trip to a few months, you really don’t absolutely need it anymore. As long as Mars and the asteroid are heading in the same general direction, you just carefully pick the point you want to launch into the transfer orbit for rendezvous, using optimal values of fuel, etc.

Gotcher point, Bubba! One quibble – I’m not sure how easy it would be to mine a comet for water. By the time it gets close in enough to Earth, it’s also going to be so close to the Sun that it’s going to be out-gassing like mad. But it just now occurred to me – you might place an opaque net in front of one, design it to wrap around the body (bolus?), and then, on its way out, have an explosive charge shatter some considerable ‘nugget’ of ice free and harvest that. As for an asteroid – a robot miner similar to what I’ve described might do that, using a mass driver to send the nickel Earthward a lump at a time.

UkeIke: Did you ever see the early '60s movie with (IIRC)Sean McClory? Don’t remember that much about it. I think I saw it with my brother, and we both thought it was absurb, even then.

33

DIF: Wow! Four stars for YOU this afternoon! No, I’d never heard of it, never known that it had been attempted. Looked it up in IMDB just now: VALLEY OF THE DRAGONS, 1961. Maltin thinks about as much of it as you did.

Uke

34

Therealbubba wrote:

What about the Mars Observer mission a few years ago? That thing just plain QUIT on its way to Mars.

35

Robots are cheaper and becoming better at what they do. Also, there loss is not tragic like the loss of an astronaut. Colonizing Mars with robots will only make us build better robots.

Only humans commit inhuman acts.

36

Tracer, missed that one. I stand corrected. Anyone know what happened? Was it a lander or an orbiter? Good thing there were not astronauts on board.

Therealbubba

37

My memory of the subsequent NASA investigation of the loss of the craft was their (tentative, and fated to remain so) guess was that a failure in a pressurized gas line necessary for control led to a loss of the craft as it approached Mars. And, of course, (as did this last mishap) the charge of “they’re covering up the discovery of a Martian civilization!” on the part of fringe groups.

38

Therealbubba wrote:

If the Mars Observer had been designed to carry astronauts, they would’ve (A) tested the spacecraft a LOT more thoroughly before sending it to Mars with people on board, and (B) had manual overrides which would have allowed the astronauts to pilot the spacecraft by hand.

Carl Sagan remarked that once you put human beings on board a spacecraft, that spacecraft’s primary mission then automatically becomes one of returning the humans safely to the Earth. All other mission objectives immediately become secondary.

If one manned mission costs the same as 10 unmanned missions, and three of those unmanned missions fail, we’re still ahead by a factor of 7-to-1 if we go the unmanned route.

Quick-N-Dirty Aviation: Trading altitude for airspeed since 1992.

39

I say we don’t send manned missions to Mars until the US completely converts to Metric. :slight_smile:

Seriously, I think these are the steps needed to get men to Mars:[list=1][li]Getting a viable space station going. Then, start setting up stations in solar orbits between Earth and Mars to act as resting points (ala the camps on the way to Mt. Everest’s peak).[/li][li]Developing a way to extract usable O[sub]2[/sub] from Martian soil. Depending on pre-tanked O[sub]2[/sub] would be too risky a venture.[/li][li]Develop a propulsion system that isn’t chemically driven. Some sort of solar sail or ionic propulsion would be ideal.[/li][*]Contact the Martians to make sure our tourist visas are all in order. :)[/list=1]

40

AWB wrote:

Stations in solar orbits between Earth and Mars won’t work. The farther out from the sun you are, the more slowly you orbit it. The likelihood of a solar-orbiting “station” being right on the Earth-Mars trajectory at any one moment is tiny; the chance of being able to hit all of them en route is vanishingly small. Plus, even if your trajectory did manage to intersect an intervening station, you’d still be going way too fast when you reach it – you’d have to waste energy (fuel) slowing down to dock with it, then waste more energy (fuel) speeding up again to get back on course for Mars.

Earth-orbiting space stations are seen as a useful taking-off point for deep space exploration, not because you can reload supplies from them, but because ALL deep-space missions start off as Earth-orbiting missions – so you can use them as refueling stages or as places to build a spacecraft in Earth orbit. In low Earth orbit you start off with 17,500 miles per hour of delta-V on your side, and as Heinlein once remarked, “17,500 m.p.h. is half way to anywhere.”

Quick-N-Dirty Aviation: Trading altitude for airspeed since 1992.