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Did NASA really make it to Mars?
Dear Bill:
If you were in front of me on a PhD Qual Oral, you bet I'd can your ass too, if this is any example of your know-nothing 'understanding' of spaceflight basics. Mars's lower gravity doesn't squeeze the air down so tightly, so above about 100-200 km, it's actually thicker than earth's. That's where aerobraking (and natural meteors) mostly occur. It's not "at most a mile thick". You must have been confusing it with your head. "Such a small, thin atmosphere would require such a huge parachute to slow the descent appreciably over such a short difference in altitude that it seems obvious that the weight of such a parachute would make it impractical." And -- correct me if I'm wrong -- you whine that you were UNFAIRLY denied entry to a PhD program in space science at the University of Texas? Bill, you're lucky you were given an 8th grade certificate. Find something to do that you're competent at, and make yourself -- and us -- happier. Your 'tough love' friend, JimO "Bill Clark" wrote in message om... It is my understanding that the atmosphere of Mars is so thin that the winds that always go hundreds of miles per hour would only feel like a light breeze. Also, Mars being such a small planet, the atmosphere itself is a much thinner than on Earth, being at most a mile thick. This makes me doubt the efficacy of the recent Mars missions that have supposedly used aerobraking to save fuel, using the friction of the Martian atmosphere to slowly bring the spacecraft into a low Mars orbit. I almost wonder if aerobraking is possible at all; except NASA claims to have used it successfully on the satellites currently orbiting Mars. I also wonder how the Mars landers use parachutes to effectively slow the descent of the latest Mars landers. Such a small, thin atmosphere would require such a huge parachute to slow the descent appreciably over such a short difference in altitude that it seems obvious that the weight of such a parachute would make it impractical. Yet, the NASA missions that have landed on Mars claim to use parachutes quite effectively - even for the latest two landers which are monster robots compared to little sojourner which was the size of a PC box, versus the refrigerator sized landers there now. These simple notions make it seem like the whole thing is a hoax, and that we never made it to Mars at all but just some remote desert in Arizona . . . Just curious |
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I don't want to get in the middle of your fight, Jim, but it's pretty well
known that the air (if you could call it that) on Mars is actually quite a bit thinner than what we're accustomed to on earth. Aerobraking isn't so exotic a technique as many might think, but that aside, the point about the parachutes is well made. And BTW, that's no longer an issue of space flight. Wasn't that a beer can I saw under one of those rocks? Mars's lower gravity doesn't squeeze the air down so tightly, so above about 100-200 km, it's actually thicker than earth's. That's where aerobraking (and natural meteors) mostly occur. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.637 / Virus Database: 408 - Release Date: 3/20/04 |
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On Wed, 24 Mar 2004 17:38:19 GMT, in a place far, far away, "ashlar"
made the phosphor on my monitor glow in such a way as to indicate that: I don't want to get in the middle of your fight, Jim, but it's pretty well known that the air (if you could call it that) on Mars is actually quite a bit thinner than what we're accustomed to on earth. Reread what he wrote. The air at the surface is thinner, but at higher altitude it's actually thicker, because it's compressed less. the point about the parachutes is well made. No, it's not. |
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On Wed, 24 Mar 2004 13:02:42 -0600, in a place far, far away, Herb
Schaltegger made the phosphor on my monitor glow in such a way as to indicate that: In article , h (Rand Simberg) wrote: Reread what he wrote. The air at the surface is thinner, but at higher altitude it's actually thicker, because it's compressed less. Let's not be sloppy in our terminology lest Stuffie show up and start castigating us once more. "Thicker" in terms of linear distance, or "thicker" in terms of density? I meant in terms of density, but it may be in the other sense of the word as well--I'd have to go look it up. |
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"Rand Simberg" wrote in message ... On Wed, 24 Mar 2004 13:02:42 -0600, in a place far, far away, Herb Schaltegger made the phosphor on my monitor glow in such a way as to indicate that: In article , h (Rand Simberg) wrote: Reread what he wrote. The air at the surface is thinner, but at higher altitude it's actually thicker, because it's compressed less. Let's not be sloppy in our terminology lest Stuffie show up and start castigating us once more. "Thicker" in terms of linear distance, or "thicker" in terms of density? I meant in terms of density, but it may be in the other sense of the word as well--I'd have to go look it up. How about: the rate of density decrease with altitude is lower on Mars than on Earth? |
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On Wed, 24 Mar 2004 14:51:45 -0500, in a place far, far away, "Scott
Hedrick" made the phosphor on my monitor glow in such a way as to indicate that: In article , h (Rand Simberg) wrote: Reread what he wrote. The air at the surface is thinner, but at higher altitude it's actually thicker, because it's compressed less. Let's not be sloppy in our terminology lest Stuffie show up and start castigating us once more. "Thicker" in terms of linear distance, or "thicker" in terms of density? I meant in terms of density, but it may be in the other sense of the word as well--I'd have to go look it up. How about: the rate of density decrease with altitude is lower on Mars than on Earth? Yes, but I should clarify that when I say "thinner" and "thicker" above, I mean relative to earth's profile, not to each other. The Martian atmosphere 's definitely thinner at altitude than it is at the surface, but it's thicker than earth's at (some) altitude. |
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"Rand Simberg" wrote in message ... On Wed, 24 Mar 2004 17:38:19 GMT, in a place far, far away, "ashlar" made the phosphor on my monitor glow in such a way as to indicate that: I don't want to get in the middle of your fight, Jim, but it's pretty well known that the air (if you could call it that) on Mars is actually quite a bit thinner than what we're accustomed to on earth. Reread what he wrote. The air at the surface is thinner, but at higher altitude it's actually thicker, because it's compressed less. Compared to the same altitude on Earth. Just to be clear, neither Rand nor Jim are saying that the atmosphere magically gets denser as you get higher. (at least not until you hit the ether.:-) the point about the parachutes is well made. No, it's not. |
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"James Oberg" wrote in message
... Dear Bill: Jim, did you cross-post this rubbish to the sci.space groups? I mean, if the 'alien' type want to believe this rubbish, let them, but I am in the sci.space groups for knowledge and the idiot that came up with this rubbish has nothing at all to offer. -- Alan Erskine We can get people to the Moon in five years, not the fifteen GWB proposes. Give NASA a real challenge |
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