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Mars Transport, Discussions of the methods of transitting to Mars
Art Martin
post Dec 24 2014, 03:06 PM
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Today I read an article that was fascinating and seems to offer up new and cheaper options for putting spacecraft into Martian orbit. It's described in this article:

A New Way to Reach Mars Safely, Anytime and on the Cheap
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mcaplinger
post Dec 28 2014, 09:07 PM
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http://arxiv.org/abs/1410.8856 is a link to the original paper.

This seems of limited utility; conventional Hohmann transfers use less energy for orbits of usefully low periapse or landing. It increases trip time but does allow for more flexibility in departure time.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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djellison
post Dec 29 2014, 02:47 AM
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That's what I got from it as well....the definition of 'reach Mars' is somewhat limited in scope. The article says " the big burn to slow down and hit the Martian bull's-eye—as in the Hohmann scenario—is done away with" ... well, direct landings have no such burn, so there's no benefit there whatsoever.

Moreover "Although launch and cruise costs remain the same...." and "A straight shot with abrupt braking at Mars takes about six months whereas a trip relying on ballistic capture would take an additional several months" are at odds with one another.

MAVEN launched on the cheapest LV available - an Atlas V 401 which had more than enough performance to deliver MAVEN and the fuel for a 'traditional' MOI. Saving a few hundreds lbs of MOI fuel would have saved nothing in launch costs, and added costs for extended cruise operations. The same was basically true of MGS, MRO, MEX and Odyssey. Assuming a transition to a cheaper Falcon 9 for similarly sized missions in the future...it has even more performance to spare than the Atlas V 401.

Really not sure how applicable this is to anything but a very specific kind of mission...and one we've not actually needed yet.

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MahFL
post Dec 29 2014, 12:25 PM
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QUOTE (djellison @ Dec 29 2014, 03:47 AM) *
... "A straight shot with abrupt braking at Mars takes about six months whereas a trip relying on ballistic capture would take an additional several months" are at odds with one another..."


I think they are not considering the insertion burn as part of the cruise. Also of course you have several extra months of cruise time which has to be "manned" back on Earth, which also costs money.
Also a longer cruise time could mean more time for a failure to occur.
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djellison
post Dec 29 2014, 03:34 PM
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QUOTE (MahFL @ Dec 29 2014, 04:25 AM) *
Also of course you have several extra months of cruise time which has to be "manned" back on Earth, which also costs money.


That was the exact point I was making.
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Art Martin
post Dec 29 2014, 07:27 PM
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Thanks guys for the analysis. You see science articles outside of this venue and they seem legitimate and vetted but I know I'll always get the straight answers in here. Nice to know weight isn't as much a concern as it used to be with the beefier launch systems. Sometimes it's interesting to see the brainstorming others are using out there.
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