Wreckage Of Beagle 2 Found? |
Wreckage Of Beagle 2 Found? |
Dec 20 2005, 01:07 AM
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Member Group: Members Posts: 147 Joined: 3-July 04 From: Chicago, IL Member No.: 91 |
Wreckage of Beagle found scattered in Mars crater
Talk about being unlucky assuming this is confirmed. |
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Guest_BruceMoomaw_* |
Dec 21 2005, 08:30 AM
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Guests |
Given how close MER-A (I refuse to use that cornball name "Spirit") came to disaster because of the unexpectedly low density of Mars' upper atmosphere -- even after its hasty last-minute reprogramming to open its parachute earlier, it came within 3 seconds of opening the chute too late to avoid a crash -- I think this has an excellent chance of being the fatal flaw in Beagle: it just came down too damned fast due to the lower than predicted Martian air density, and kaplooey. We'll never know whether some additional flaw also existed that would have done it in anyway, given the flaws that the failure board found to be riddling its design -- but the air density problem by itself would have been enough, and is very likely to have happened.
I am only now coming to realize how hard it actually is to land on Mars because of its peculiar halfway nature. As Ed Strick (and Rob Manning) say, it's very hard to utilize either purely aerodynamic braking or purely rocket braking to land on it, and Mars' thin air density has a height profile such that it's difficult even to combine the two effectively enough to get the braking job done in time. We may actually have been very lucky up to now to pull off as many successful Mars landings as we have -- most of the previous failures (Mars 2, 3 and 7; Polar Lander) were due to unconnected technical problems, but Mars' atmosphere alone may seriously endanger landers, and may conceivably have done in both Mars 6 and Beagle as well as almost killing MER-A. And the bigger the lander, the more serious the problem rapidly becomes. |
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Dec 22 2005, 09:01 PM
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#3
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (BruceMoomaw @ Dec 21 2005, 01:30 AM) I am only now coming to realize how hard it actually is to land on Mars because of its peculiar halfway nature. As Ed Strick (and Rob Manning) say, it's very hard to utilize either purely aerodynamic braking or purely rocket braking to land on it, and Mars' thin air density has a height profile such that it's difficult even to combine the two effectively enough to get the braking job done in time. We may actually have been very lucky up to now to pull off as many successful Mars landings as we have -- most of the previous failures (Mars 2, 3 and 7; Polar Lander) were due to unconnected technical problems, but Mars' atmosphere alone may seriously endanger landers, and may conceivably have done in both Mars 6 and Beagle as well as almost killing MER-A. And the bigger the lander, the more serious the problem rapidly becomes. Both of the Viking craft used more of their fuel than expected (8-15%), but still held excess in reserve. Every single Martian landing craft has enter at a higher attitude and come down harder than expected, deployed parachutes later than expected, and left unanswered questions about their parachute drag coefficients and descent profiles. Every one. With lower engineering margins, the Mars 2,3,6, Polar lander and Beagle did not have chance. The MRO has the potential of providing a definitive answer to these curiousites, but you must be willing to look at the possibility that there are very weak, second order gravitational effects. Weak second order effects, based upon the total mass of a system cannot be ruled out from our earth-moon platform, because the local mass-fraction is dominated by the solar mass. But further from the Sun and orbiting at an altitude of only 150 km, the MRO will sense gravity anomalies that are a full and unexplicable order of magnitude greater than the 300km orbiters. |
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Dec 23 2005, 07:51 PM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
QUOTE (The Messenger @ Dec 22 2005, 01:01 PM) ...orbiting at an altitude of only 150 km, the MRO will sense gravity anomalies that are a full and unexplicable order of magnitude greater than the 300km orbiters. A couple of points: MRO's mapping orbit isn't at 150 km -- it's between about 250 km and 320 km. Early in mission planning a lower periapse was considered, but this wasn't chosen. Both MGS and I believe Odyssey routinely went below 150 km during aerobraking. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Dec 27 2005, 04:37 PM
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#5
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (mcaplinger @ Dec 23 2005, 12:51 PM) A couple of points: MRO's mapping orbit isn't at 150 km -- it's between about 250 km and 320 km. Early in mission planning a lower periapse was considered, but this wasn't chosen. Bummer. The mapping will provide much more detail, and hopefully provide better insight into what is proving to be the ellusive - the moment of inertia. QUOTE I think it is how the degeneracies in the harmonics have been identified, but I do not fully understand the details. QUOTE (ljk4-1 @ Dec 23 2005, 08:26 AM) I remember reading that Mars 3 may have kept working just fine on the surface - it was the orbiter that somehow lost the link with the lander. Any details on this? I wonder if it stored any data onboard? Would it still be readable if so? Yes, I realize I am talking about a 1971 Soviet computer. It would be fun to send one of the MER's on a long-hull mission to check it out...extend the mission to 2304... Mars 3 impacted at about twice the expected velocity (~20m/s), but was designed to withstand such an impact. Since little in the way of lightning has been noted by MER's in a year of exploration, the possibility that the quick zap out was due to static effects is appearing less likely. http://klabs.org/richcontent/Reports/mars/...oad_to_mars.pdf (Soviet Report on the Difficult road to Mars, this is a good read.) http://nssdc.gsfc.nasa.gov/database/Master...og?sc=1971-049F The surface gravity numbers I have for the Viking probes are 1.5% above NASA's currently published estimate (3.725 Viking mean, current NASA: 3.71m/s^2), but I do not know how this current value was derived. Until the moment of inertia is pinned down, the unknown mass distribution limits the resolution of the surface gravity. http://techreports.larc.nasa.gov/ltrs/PDF/...76-cr159388.pdf (Vintage Viking document, also a fun read) As per Doug's request, I will keep my speculations-as-to-cause off the board, but everyone appreciates the importance of noting and trying to understand the cause of anomalies. This board is too good to miss - for any reason. |
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