Tires on the ground ...

For the Earth oriented ball rover designs, wind will be a problem. One way to keep the rover from being blown off course would be to stop in a gully or other low spot and pump all the air out of the tire. When the wind dies down, re-inflate and continue the journey.

If wind should turn out to be a problem on Mars, this would work there as well.

<b>[Stoat] " ... a human size one would be the ultimate dangerous sport. A two metre ball ... "</b>

The terminal speed of a free falling human sans parachute is about 200 kph, if the human assumes the frog position (body horizontal, arms and legs spread wide). In the dive position (body vertical, arms tucked in next to the body, legs together and straight) terminal speed is much higher, 2X or so at low altitude. The Army claims that at least one high altitude jumper has broken the sound barier. Terminal speeds while tumbling out of control are between these extremes, but generally closer to the low end.

Believe it or not several people have survived multi-kilometer falls. (I saw a Ripley's segment on this a while back. There are articles on the 'Net about flight attendants and bomber crew that have also survived.)

The terminal speed of a 2 or 3 meter ball with only a little more mass than a human would be much less than 200 kph. Landing on a slope would further reduce the impact forces ...

<b>[Stoat] " Scares me."</b>

I plan to watch from a safe distance.

For the central axle, I had thought of it being like a telescopic brolly handle. These spring open and lock but we could have the end part still free to move on its spring. The end hubs then have some give on impact. I thought we could put the cameras in the hubs and have them rather like the design of road cat's eyes. The Brit ones have a lens cleaner built in. Drive over one and it pushes down and cleans the lens as it does so.

For the central diff affair, I have the gearbox and motor near the central axle. The rod that extends downwards, to the paylaod, is telescopic as well. This is so we can fold the whole thing up for transport.

I suppose the people ball only needs a wire cage and a two stroke engine. Solves the exhaust problem, unless we want to make it a water sport. We don't need a gear box for it either as the driver can just shift his/her weight to steer it.

Some good suggestions. At this stage of the design process we need to be looking at as many solutions as possible, rather than trying to pick the final design details.

Each solution to a problem has advantages and disadvantages relative to other solutions. During the late stages of design, one of them has to be chosen for actual use in the product. The customers start using it, and that is when you get to find out if you really knew what you were doing.

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The ball racer stage of this project can help us weed out (some) bad design elemenmts. And perhaps make a little money to keep the investors happy. Happy stage one investors means we might actually have a shot at stage three. The flip side is, if the ball racer idea flops, the investors will likely lose interest.

Risk. No way to avoid it.

Larry and Stoat,

I have been thinking about this project a lot. I am definately onboard, insofar as I have no capital to expend, but consider this idea. Could we make an earth-based introductory product, to explore remote locations of the globe that people (older, with money and poor mobility) could rent? A trip to remote Patagonia, Antartica, Gobi desert, Volcanic craters, the bottom of the ocean? I know that this is far away from Mars, but it could be a considerable (and cheaper) proving ground for the technology. Just a thought

Mark Vitrone

That sounds good to me. Patagonia and the Arctic ice sheets sound two good survey sites, as they allow good science. Fill our balls with heaver gas.

Suppose we took a small perspex rod and laser cut a thread onto it, rather like an Edison cylinder cd record. Then we do the same to a perspex tube but with a series of rings. Glue on to the rod an led and pop a couple of fine springs to each end. Pop the rod into the tube. Perhaps hook this up to our peizoelectric gyro compass. If the rod moves very slightly it sets up interference patterns, as we have a Moire pattern etched into the rod and tube. A mini seismograph.

Talking of which, could there be oil deposits on Mars? Oceans and possible diatomic life suggests that it's possible. If we had a mini seismograph we could crash land something and see if there might be oil deposits. The fact that it's so far away won't put off oil men, they think in terms of the long haul.

Related to this as a survey goal, how much of this project's cost has to be set against necessary infomation for any manned landing?

I found this, which suggests a micro seimometer already exists. www.marsdaily.com/reports/Brits_Unveil_L...or_Life_On_Mars.html

(edited) The JPL seismometer is a capacitor shaped like the petals of a flower. The top plateis a gramme and has springs round its edge. So it looks as though the electronics measures changes in plate area. The Moire pattern is much more cheap and cheerful. it would use the circuitry of an electronic micrometer but should be able to measure incredibly smal movements of the rod.