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Lowest altitude viable Mars orbit
Is it possible to be in Mars orbit and collide with Olympus Mons?
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Lowest altitude viable Mars orbit
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Lowest altitude viable Mars orbit
"Explorer8939" wrote in message om... Is it possible to be in Mars orbit and collide with Olympus Mons? It's possible to be in Mars orbit and scrape the bottom of the Valles Marineris if your perigee is low enough. Once, anyway 8-) Jonathan Wilson |
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Lowest altitude viable Mars orbit
In article ,
Explorer8939 wrote: Is it possible to be in Mars orbit and collide with Olympus Mons? No, alas. (Not that anyone would want to collide with it, but an orbit passing low over it would be quite the tourist ride...) Aerobraking and reentry altitudes on Mars are actually similar to those on Earth -- the atmosphere is much thinner, but the weaker gravitational field means density drops off rather less rapidly with altitude. And Olympus Mons is high, but it's not *that* high... -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
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Lowest altitude viable Mars orbit
"Explorer8939" wrote in message om...
Is it possible to be in Mars orbit and collide with Olympus Mons? Doubt it. It's 27km high and there are dry ice clouds up as high as 50km. http://www.daviddarling.info/images/...tmosphere1.jpg -- __ "A good leader knows when it's best to ignore the __ ('__` screams for help and focus on the bigger picture." '__`) //6(6; ©OOL mmiv :^)^\\ `\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/' |
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Lowest altitude viable Mars orbit
I wrote:
[...] the pressure at "datum" is 61 millibars, so the pressure at the summit is about 0.5 millibars, ^^^^^^^^^^^^^^ Typo correction: The above should read "6.1 millibars," not "61 millibars." -- Gordon D. Pusch perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;' |
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Lowest altitude viable Mars orbit
Henry Spencer wrote:
In article , Explorer8939 wrote: Is it possible to be in Mars orbit and collide with Olympus Mons? No, alas. (Not that anyone would want to collide with it, but an orbit passing low over it would be quite the tourist ride...) Aerobraking and reentry altitudes on Mars are actually similar to those on Earth -- the atmosphere is much thinner, but the weaker gravitational field means density drops off rather less rapidly with altitude. And Olympus Mons is high, but it's not *that* high... But if you are doing touristy things on Mars, you could aerobrake to near it then start a retrofire and fly past it on the other side to retrograde orbit. -- Sander +++ Out of cheese error +++ |
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Lowest altitude viable Mars orbit
Henry Spencer wrote: In article , Explorer8939 wrote: Is it possible to be in Mars orbit and collide with Olympus Mons? No, alas. (Not that anyone would want to collide with it, but an orbit passing low over it would be quite the tourist ride...) Aerobraking and reentry altitudes on Mars are actually similar to those on Earth -- the atmosphere is much thinner, but the weaker gravitational field means density drops off rather less rapidly with altitude. And Olympus Mons is high, but it's not *that* high... My remembrance of Martian aerobraking guidance studies in the late 1980's (single pass) was that we were using periapsis altitudes less than the height of Mt. Olympus. That would depend on the mission of course, and the atmospheric models have presumably been upgraded since then. - Matt Managed to dig out a conference paper: AIAA 87-2401, "Optimal Guidance for Future Space Applications," J.E.Bradt, M.V.Jessick, J.W.Hardtla. AIAA GN&C Conference 1987 The last example trajectory is a Martian aerocapture patterned after the Mars Sample Return Mission studies of the day. Periapsis altitude was 80000 ft, a bit less than 25km. L/D 0.75 and 141 lbf/ft**2 ballistic coefficient |
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Lowest altitude viable Mars orbit
T writes:
Explorer8939 wrote: Is it possible to be in Mars orbit and collide with Olympus Mons? Without yet reading the other (probably more informed) replies That is generally a mistake. I'll say if you can sustain a Powered Orbit (counteracting the tendency of a fast orbit speed leading to a greater orbit circumference) I think you need to review your basic orbital mechanics. The lower an orbiting body is, the faster that orbiting body moves. then you can skim right over the top of the highest peak you choose. The real problem is friction from the martian atmosphere. So unless you want to consider hovering flight under rocket power a "powered orbit," IMO, your answer is incorrect. -- Gordon D. Pusch perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;' |
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Lowest altitude viable Mars orbit
Of possible interest, it is my understanding that because of gravity, the
Martian atmosphere extends further from the ground then Earths, so any long term orbit would necessarily need to be higher to avoid significant drag. 400 kilometers might not be a good place to park your crew return vehicle, for example, unless you were confident that it could be reliably reboosted as needed. |
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