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by lrichardson 4232 days ago
> Building a vehicle to carry sufficient fuel and supplies for the trip to Mars is not especially technically challenging, when compared to the design of an earth-entry vehicle. Earth orbit rendezvous allows for the assembly of massive (though expensive) space vehicles such as the ISS.

Of course, they do have to land on mars, don't they? Isn't this roughly similar (and thus similarly as challenging) as earth re-entry?
1 comments
NickNameNick 4232 days ago
Possibly more so.

I think it was someone working on Curiosity that said mars has just enough of an atmosphere that you have to worry about it, but not quite enough to be useful.

And bearing in mind that when your spacecraft hits the martian atmosphere, it was traveling at interplanetary transit speeds, much greater than orbital speed.

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Solarsail 4232 days ago
I'm pretty sure that was Steve Squyres in the book Roving Mars, discussing Spirit and Opportunity. From memory, a heat shield can get you from escape velocity down to ~mach 3, and then supersonic parachutes can get you down to ~100mph. It's an issue because you've still got to slow down beyond that, but you can't just ignore atmospheric shielding like you could with the Moon (in response to iwwr)

I could be wrong about him saying that in Roving Mars (I can't exactly grep my paperback copy, and Google isn't helping), but I'm pretty sure it wasn't on the subject of Curiosity... I heard it in 2006 or 2007, while Curiosity was still called the Mars Science Laboratory.

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iwwr 4232 days ago
>I think it was someone working on Curiosity that said mars has just enough of an atmosphere that you have to worry about it, but not quite enough to be useful.

It certainly is useful and you can still shed 90-95% of the inbound orbital velocity or even that from an interplanetary trajectory with a reasonable heat shield. It would be far more difficult if Mars were completely airless. You still need retrorockets for landing big payloads but at a discount.

Though the other atmosphered bodies in our solar system: Earth, Venus (cloud deck), Titan can be achieveable with just parachutes.

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