Apollo Sites from LRO |
Apollo Sites from LRO |
Jul 17 2009, 02:52 PM
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#101
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
Thought this deserved a new thread- we can't talk about EVERY LRO target in the one thread
I made a mistake in this one - I didn't include the thruster plume guards. My MER/MPF simulation for HiRISE seemed to come out about right - so fingers crossed that this will be there or there abouts as well. Still in a comissioning phase, something of a slant angle - I'd expect approx 1.5m/pixel if it's at the 120km figure mentioned earlier. |
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Sep 4 2009, 03:41 AM
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#102
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Just to be completely clear -- I think we should stop referring to a "tank," as it seems some people are envisioning tankage that fed liquid propellants into a combustion chamber complete with attached nozzle extension.
The Surveyor main retro motor was a solid rocket motor. It was a sphere a little less than a meter in diameter that was filled with between 1,200 and 1,300 pounds of solid propellant. A star-shaped core opened out to a throat and nozzle that, when the spacecraft was properly aligned, faced into the velocity vector. Ignition charges would ignite the fuel down into the core, the fuel burns from the core out to the casing, and the rest is a simple application of the Rocket Principle. While the motor is a "pressure vessel" in the same way that any SRBs are pressure vessels (they must contain the pressure of the expanding gases as the solid fuel burns), it's not what comes to my mind when I think of a pressure vessel. My conception of a pressure vessel is a tank that holds a liquid at pressure. (After all, other SRBs are referred to as "motors" when filled and "casings" when empty, but never referred to as "tanks"...) It's hard to say how much impact force a burned-out solid rocket motor casing, with only a few pounds of fuel left inside, could withstand without pancaking. But the assembly did have a big open throat when it impacted, and was vented to vacuum inside and out, so we'd only be talking about the inherent tensile strength of the metal and the welds after they had been heated dramatically by the burning of the fuel and been stressed by containing the pressure of the burning fuel (in all directions except through the nozzle, of course). It would not have the same kind of resistance to pancaking that a pressurized tank would have. -the other Doug p.s. -- no, Ilbasso, the mock-up you have pictured doesn't include the retro motor. The motor nestled in a cavity exactly in the middle of the landing legs. The sphere extended below the plane of the footpads, and the nozzle, of course, extended even further down than that. Any Surveyor model you see that doesn't have a big sphere sticking out like a potbelly from between its legs doesn't include the retro motor. DVD -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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