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Posted: |
Feb 19, 2021 - 11:03 PM
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By: |
Grecchus
(Member)
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That's not an instant one. Mars is a big planet, but it's not as big as Earth. Both the descent and ascent stages of the Apollo lunar module had fairly small rocket engines. It was an amazing piece of kit. With limitations, it could descend to the lunar surface and ascend to orbit to rendezvous with the mother ship. It had enough delta_v propellant to push itself around the Moon to accomplish its mission.
The 3rd stage of the Saturn V, once propelled towards the moon would sometimes impact on it with intent once the CSM/LM stack separated. Mid course corrections effected by the CSM/LM ensured it would go above the Moon's local horizon, rather than under it. When you do this farther out from the gravitating body you're heading towards, the less rocket engine impulse is required to make a deviation with respect to the planetary horizon. It's like the further away you are when you make make a course correction, the greater the leverage you have (the less fuel you need to get the job done, too) - the closer you get, the inverse square law ensures you get less leverage because the acceleration caused by gravity is so much greater and any push required to make a significant 'dent' to a spacecraft's inertial motion toward or away from the planetary local horizon is going to be so much greater. So, I tend to think the body of the probe that separated from Perseverance would not have deviated greatly from itself because they were on a corridor approach straight into Mars' atmosphere, having left each other close enough to the planet that the outcome was for both of them to go in. If separation had occured much earlier and under control it may have been possible to send the attachment around the planet, rather than into it. My guess is that would not have been possible because Perseverance required services from the module to stay powered and in good shape and they needed to stay attached for as long as possible. It the service module section had gone around Mars it would then add to the bits of loose change flying around the solar system local to the Earth. Also, Newton's laws of motion mean that when Perseverance separated from its trunk the equal and opposite reaction forces between them slowed one down and the other one up a bit. Since Perseverance was in 'front' of the trunk, which was 'behind' it, then Perseverance would not have the trunk acting as a possible obstruction directly ahead, because it (the trunk) was moving slightly slower and behind. The same thing happened with Apollo. The CM separated so that it was in front of the SM with respect to their combined motion into the re-entry corridor to Earth's atmosphere. In space, nothing can be left to chance.
But, as with the lunar module and the Moon, the smaller the planetary body you're navigating with respect to, the less force is required by the engines to go this way or that way whenever the need arises. All I can say, Sol, is that Mars is somewhere in size between the Moon and the Earth.
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A planet that has a signature indicating the presence of life will not contain a chemically inert atmosphere. This is the basic idea.
Probably on a lockdown, anyway! 
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