Playdor's thread Nov 13, 2011 5:07:54 GMT -4
Post by ka9q on Nov 13, 2011 5:07:54 GMT -4
If you are referring to the four plume deflectors mounted on the descent stage that project up under the downward-pointing RCS engines on the ascent stage, they were constructed from metal. And no, they were not coated with plastic.
Or at least they weren't coated with a plastic intended to withstand the heat of the plumes during flight. But it's entirely possible they were covered before launch with a plastic to protect them during manufacturing and installation.
These plume deflectors were specifically designed to keep the downward RCS plumes from impinging on the thermal blankets protecting the descent stage. That's because the RCS thruster quads were mounted well above the top of the descent stage.
But there was nothing below the descent engine to protect against its plume; the engine itself was the lowest point on the LM except for the landing probes.
That is not to say that the descent engine didn't cause any heating problems. In fact, it did. But the exhaust plume wasn't the problem, rather it was the engine nozzle. It became extremely hot, probably to the point of visibly glowing. It therefore emitted a great deal of infrared that heated other structures on the bottom of the LM, in particular the landing radar antennas. That's why you'll find, on the bottom of every LM, a white rectangular shield mounted between the descent engine nozzle and the radar antenna to block direct IR radiation from the engine nozzle from striking the radar antenna.