There's a piece in the New York Times this morning about a German project to send a balloon-borne rover to Mars that's got a little something for everyone. It's a Mars mission, which never gets old, but it's also a privately financed project, and thus a nice demonstration of the power of private enterprise, for those who favor private space exploration. It's not quite clear to me that what they're proposing will work (one or two of the elements sound a little goofy), but they're certainly fired up about it.
And really, why shouldn't they be? Balloons on Mars are just cool.
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There's a little squib in the New York Times today about the return of the Dawn mission to visit a couple of asteroids, one of their little not-quite-a-full-story things in the "Week in Review" section of the print edition (we get the Sunday Times delivered, because I find it much more civilized…
Yet another in today's series of reposts of articles about space policy. This is another old blog post from 2004, back when the Moon-and-Mars plan was first announced. As with the previous posts, any numbers or links in the post may be badly out of date, and there are some good comments at the…
By Dr. Richard Quinn; Carl Sagan Center for the Study of Life in the Universe, SETI Institute, and Gail Jacobs
Is the surface of Mars really sterile, or could there be still-undiscovered traces of life littering this hostile landscape? Chemist Richard Quinn focuses on understanding the reactive…
As threatened in passing yesterday, I dug up some old posts on space policy, and will re-post them here. This first one dates from January of 2004, around the time that Bush first floated the idea of the new Moon-and-Mars plan that's re-shaping NASA.
The original post has a ton of links in it, and…
1) "...a vehicle inspired more by dirigibles like the Hindenburg..." Riiight.
2) Earth air has average MW = 29/760 torr. One liter masses 1.295 g/STP. Helium has MW = 4.003. One liter masses 0.1787 g. A helium balloon has 1.116 gram/liter of lift (less balloon mass).
Mars air is 95% CO2 5% nitrogen at 7 torr maximum. Average MW = 43.21. One liter masses 0.01777 g. Helium at 7 torr masses 0.001646 g/l. A Mars helium balloon has 0.01612 g/liter of lift.
Temperature corrections from STP won't save you.
3) A 170 lb craft with a 33-foot diameter balloon is claimed. 170 lbs = 77,273 g needing 4.8 million liters of helium for neutral boyancy at 7 torr. 33-foot diameter sphere is 502.9 cm radius or 533,000 liters at 7 torr. Ain't even close. Inflating the balloon in vacuo from a 24 liter 3000 psi tank is cute (tribocharging!). Helium's Joule-Thompson inversion temp is ~50 kelvin. Turbine expansion for cooling a half-millon liters during fill?
http://en.wikipedia.org/wiki/Joule-Thompson_effect
http://www.aero.org/publications/donabedian/donabedian-1.html
Tell Uncle Al why a Zylon paraglider (double Kevlar's strength; decomposes at 650 C) weighing as much as the balloon plus included gas is not a better drag solution - especially form factor.
http://www.aramid.com/aramid_industrial_fibers_zylon.asp
Ah... but what spreads the paraglider prior to re-entry? A little inflation. For the comparatively small inflation volume needed a liquefiable gas like ammonia is good enough - easy to store and dispense.
http://history.nasa.gov/SP-4002/images/fig32.jpg
1960s Gemini paraglider
http://www.coatingapplications.co.uk/paragliders.htm
http://members.core.com/~flyboy/para.jpg
http://uplink.space.com/attachments/307940-paragliders.jpg
statistical spread
Bottom line: Who gives a rat's ass about desiccated irradiated Mars?