MSL landing sites Options

[tuvas]

As there are some pictures being released from HiRISE of proposed MSL landing sites, I thought I'd give you what little I know about the process. As of the HiRISE team meeting a month ago or so, there were about 40 proposed sites to land MSL. These sites were prioritized, and are being photographed roughly in priority order. Each site requires a picture from each of the 3 main cameras (CTX, CRISM, and HiRISE) in their highest resolution in order to proceed. If it's determined that there can be a safe landing site, as well as interesting science targets, then they will advance to the next level, where I presume they will "wallpaper" the areas with HiRISE and CRISM (CTX, well, they get the whole landing ellipse in one shot, I think...). They likely will also photograph science areas near the proposed sites to look for interesting targets. After that, well, your guess is as good as mine. Note that none of this is official, but it's what I would expect. Also note that the landing site selection is still opened to new suggestions, the ones they have so far are not a complete list. The priority also doesn't mean anything right now other than they are the targets which will be photographed first, these priorities are still subject to change. But, well, I thought I'd send this out there for you all sink your teeth on, it really is quite interesting!

[edstrick]

The more pounds per square foot (grams per square centimeter) of vehicle you have behind a heatshield (and a bigger vehicle is more or less inevitably deeper, front to back with more "column mass"), the less the atmosphere can slow you down before you do "ares-braking" instead of "aero-braking"...

zip..... CRUNCH!

I'm going to be off by a factor of a few times, but here's a zero'h order armwave...

Earth. 1 atmosphere surface pressure. 14 pounds (mass) of air per square inch.

Mars. 1/200'th atmosphere surface pressure. That's about 10 ounces / 30 grams per square inch. Double that (roughly) to compensate for gravity. How many ounces per square inch is the MSL in it's heat shield? There's only so many pounds of atmosphere in the way of a so many pound entry vehicle trying to slow it down.

When an entry vehicle masses more than a column of atmosphere of the same diameter between surface and space, it just can't slow down a vehicle before the vehicle hits. Would a column of atmosphere (along an entry trajectory) massing the same as an entry vehicle slow it down 50%... very very roughly, I think so (ignoring gravity).