Tires on the ground ...

I think people might take a dim view of deploying nuclear reactors on mars [8D]

On the vacuum balloons, I presume we are talking about some sort of Dewar flask. I don't think it can be done but we might want to consider using the Peltier effect. Basically a thermocouple, we make a lot of tiny ones and embed them into a polymer sheet.

Should we not start off from our payload for the landers and not the size? That way we can work out the diameter of our baloons and also the area of solar cells we might need on a land rover to shift that amount of mass. I think it's always better to give a mass restriction and have the engineers fret about working to that.

Just out of idle curiosity, if the Mars storm is a rather mild affair, how is it that the sand dunes look remarkably like the ones on Earth?

A quick go at making a rover. I wanted the simplest steering, which I think would be from the centre, rather like a dumper truck's. The problem I discovered is that the wheels need to be on longish arms to get clearance. I made the body of the thing oval to try and save on packing space.

A link to the sizes of those gyros.

www.nec-tokin.com/english/product/piezodevice2/ceramicgyro.html

Deploying contained satellite type nuclear reactors should probably be standard procedure, I think there is already one in orbit in the MRO. But that is a separate topic anyway.

Stoat, I cannot do the 3D imaging that you do so well, but here is my try with some details:



Let me know what you think, Mark

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Stoat</i>
<br />if the Mars storm is a rather mild affair, how is it that the sand dunes look remarkably like the ones on Earth?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Standard theory is that they were formed billions of years ago back when the Mars atmosphere was twice as thick as Earth's. Meta theory says they were formed by water flow during the one-time gigantic flood 3.2 million years ago that came from the explosion of Body C, a water world then orbiting Mars. This latter scenario predicts that the true dunes (to be carefully distinguished from the "glassy tubes", which are not sand dunes) are all confined to one hemisphere of Mars, the hemisphere that is now mostly the southern one but overlaps the crustal dichotomy boundary on one side by about 20-30 degrees. Do any of our sharp-eyed Mars image examiners know of any exceptions? -|Tom|-

Okiedoke, I'll knock up that model and get back to you on any design mods that may be needed. The good thing about 3d is that it can show up any faults pretty quickly.

i suppose we should allow any power sources and then weed out the ones that are impractical.

<b>[Stoat] "I don't understand what you mean by a vacuum balloon, surely that's impossible."</b>

Great question, glad you asked.

Like many of my ideas, this one is adapted from something that someone else thought of first. This one comes from a fact article in my favorite magazine, <i>Analog Science Fiction And Fact</i>.

The author wondered how, given a small iron asteroid that had been dragged into Earth orbit, would we ever get all that iron down to the surface where the factories are? After discussing the usual proposals (space ships, catapults, parachutes, beanstalks), including both high and low tech variations on many of them, and the problems that each method has, he got to his idea.

Use (lasers?) to cut the asteroid in half and carve out two hemisphereical shells which are then welded back together to form a spherical shell, with a hard vacuum trapped inside. Suppose you do this and end up with a shell that is 1 kilometer in diameter and one meter thick? How much iron do you have?

A bunch. Millions of tonnes. Now you use a rocket to slow it down a little and atmospheric drag will do most of the work. Because of its size to mass ratio (similar to that of a balloon satellite) it begins to slow down much higher than most objects. If the initial trajectory is correct it will do most of its slowing down at high altitude, before drag becomes large enough to distort it and cause collapse. Because of the vacuum inside it will become somewhat buoyant before reentry is complete, and in just a little while this thing has lost all of its speed and is floating in the air. The spherical shape combined with the strength of iron are sufficient to keep it from imploding.

The author says that with the dimensions given above it should float initially at an altitude of a kilometer or two above sea level. If the seam between the two hemispheres has the right leak rate, it will slowly fill with air and sink to ground in about a month, giving us time to tow it to a suitable landing site near where it will be used. After it comes to ground, and air continues to leak inside, the ongoing loss of buoyancy will eventually cause it to collapse into a several meter tall pile of almost pure iron about a kilometer in diameter. Assuming that the asteroid was almost pure iron, of course.

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Shrink that down to 100 meters in diameter for my version. Now, the strength to mass ratio of most things goes up as the size goes down. So the shell thickness could be less than the 100 cm of a linear scale-down. Maybe only 1 cm thick. And if it is made of something stronger than 99% iron (easy to do), maybe the shell only needs to be 1 mm thick?

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That is about as far as I have taken this speculation so far. Obviously we aren't going to be able send a 100 meter sphereical shell of titanium to Mars. The idea needs work, and it may never pan out.

Comments, questions and criticism are solicited.

LB