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Alex Belits - Stupid question about Curiosity Mars landing.
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Stupid question about Curiosity Mars landing.
There are many things that probably should be said about the latest Mars landing. I see it as a great achievement in development of technology, it creates new possibilities for both research, and development of even more complex equipment for space exploration, but at the moment one question bothers me:

The whole crane thing was supposed to soften the landing, so rover will not be subjected to rapid deceleration that would happen when a more conventional platform touches the ground. I guess, it's possible that a crane supported by nothing but rockets is more stable while in flight than a landing platform when it touches the ground over a pillow of gas from the same rockets, so there may be less acceleration in the end.

But on NASA TV it was clearly visible that when the whole thing entered the atmosphere, acceleration was more than 10g, therefore each and every component of the rover and its carrier, was supposed to tolerate many minutes of such acceleration. So if the platform can guarantee less than 10g when it touches the ground, it can safely land without any complicated mechanisms, with rover on top, just like it was done for decades with smaller but just as fragile devices.

So  traditional solution has top mount for rover, low-altitude altimeter, rocket engines designed to exploit ground effect while immediately over the ground, but no crane, no procedure for keeping platform extremely stable for the whole time while rover is lowered by the crane then getting the platform away from the rover, and no weird direction of the nozzles to keep gas away from the rover. For me, that sounds clearly superior.

I really can't understand what was the reason for choosing the crane. Anyone has any idea?
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Matthew Belcher From: Matthew Belcher Date: August 6th, 2012 08:17 pm (UTC) (Link)
In the "Seven Minutes of Terror" video they said it was to keep the rockets from kicking up dust that might damage the rover.
abelits From: abelits Date: August 7th, 2012 01:34 am (UTC) (Link)
But there was still dust from the rockets firing above. The rover has to be completely enclosed while it is flying through the atmosphere anyway, so as long as there is some cover left on it when it reaches the surface (what may be just a section of the hull or heat shield, so it won't introduce additional mass), dust is not a problem. Once the dust is settled, the cover can be opened. Since cover opening mechanism should only work once, things can be done in a very simple and reliable way -- we have cover opening mechanism vs. the whole crane, so simplicity of the design is still not on the crane side.

With the crane, the whole descent stage becomes the last "cover", except it opens too early, produces more dust after that, and can damage the rover if anything goes wrong with any part of the mechanism. The last part also means that while it's acceptable for the robotic rover, it's unlikely to be re-used for manned Mars expedition, so that doesn't look like a plausible explanation, either.

As I thought of it, I could only speculate that initially there could be a project that involved descent stage remaining in the air for some other reason (taking photographs or other measurements, deploying other devices or even being used multiple times to transport the rover over some great distance that it can't cover by itself), but that part of the project was removed along the way.

Edited at 2012-08-07 01:35 am (UTC)
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