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Mars Landing 'out of the box' (Q/A)
by
aero
on 04 Nov, 2012 14:19
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This question verges on science fiction, so please don't point that out, and I can think of several related precurser questions needing answers before this question is even relavent. My basic assumption is that some orginization has decided to colonize Mars. The objective question is this.
What would it take to launch a Mars Space Elevator from Earth?
My example mission would include a single massive Mars Transfer Vehicle including a tether and a 'Rod from God' anchor. The MTV would approach Mars in a hyperbolic orbit in the equitorial plane, launch the tethered anchor ahead, then reel itself into a tethered orbit above stationary altitude. The elevator car would then use electricity to deliver the colonists to the surface needing no descent, landing or Mars launch reaction mass.
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#1
by
aero
on 05 Nov, 2012 16:59
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I guess the first question should be:
Does there exist a teather material strong enough to work for a Mars Space Elevator?
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#2
by
aero
on 08 Nov, 2012 12:40
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I guess the first question should be:
Does there exist a teather material strong enough to work for a Mars Space Elevator?
I wanted to close out this question. For those interested, the answer is "maybe" if you had a huge enough rocket to waste, but it would be a waste until you did something with Phobos. Phobos orbits well below space elevator altitude and has like six opportunities a day to crash into a Mars space elevator teather.
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#3
by
kevin-rf
on 20 Nov, 2012 17:35
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I vaguely remember a sci-fi from years ago that solved the problem by adjusting the resonance (swaying) of the elevator so Phobos always missed... But then again, this is not a Sci-Fi forum, so I'm off topic.
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#4
by
A_M_Swallow
on 10 Feb, 2013 09:05
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A space elevator does not have to be on the equator, so simply move the base of the elevator. There will however be a large reduction in the maximum payload.
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#5
by
Michael Bloxham
on 10 Feb, 2013 09:17
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Could you construct an elevator with a large Phobos-sized gap in the middle? :-P
Like a gigantic tennis-racket
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#6
by
Kaputnik
on 10 Feb, 2013 09:55
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A space elevator does not have to be on the equator, so simply move the base of the elevator. There will however be a large reduction in the maximum payload.
Is that true? Do you mean the elevator can come in at a slight angle, with the centre of the mass of the whole system still passing through the equatorial plane? Or something else?
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#7
by
ClaytonBirchenough
on 07 Apr, 2013 02:29
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In the book "Red Mars", I forget by who, an asteroid was slowed into Martian orbit, and then machines/robots manufactured the tether from the asteroid itself. Could Phobos's orbit be adjusted with SEP so that it could serve such a purpose? (Assuming this is all possible)
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#8
by
MickQ
on 07 Apr, 2013 11:19
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In the book "Red Mars", I forget by who, an asteroid was slowed into Martian orbit, and then machines/robots manufactured the tether from the asteroid itself. Could Phobos's orbit be adjusted with SEP so that it could serve such a purpose? (Assuming this is all possible)
Red Mars, Green Mars & Blue Mars were written by Kim Stanley Robinson.
Mick.
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#9
by
ClaytonBirchenough
on 07 Apr, 2013 12:26
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In the book "Red Mars", I forget by who, an asteroid was slowed into Martian orbit, and then machines/robots manufactured the tether from the asteroid itself. Could Phobos's orbit be adjusted with SEP so that it could serve such a purpose? (Assuming this is all possible)
Red Mars, Green Mars & Blue Mars were written by Kim Stanley Robinson.
Mick.
Yes, thank you. They were great books I thought.
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#10
by
douglas100
on 07 Apr, 2013 12:40
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I vaguely remember a sci-fi from years ago that solved the problem by adjusting the resonance (swaying) of the elevator so Phobos always missed... But then again, this is not a Sci-Fi forum, so I'm off topic.
The Fountains of Paradise by Arthur C. Clarke.
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#11
by
douglas100
on 07 Apr, 2013 13:34
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A space elevator does not have to be on the equator, so simply move the base of the elevator. There will however be a large reduction in the maximum payload.
Is that true? Do you mean the elevator can come in at a slight angle, with the centre of the mass of the whole system still passing through the equatorial plane? Or something else?
Not sure, but I think moving the base station a significant distance in latitude from the equator will displace the tether in a north-south direction. That would force most points of the tether to "orbit" in planes which would not pass through the centre of the planet. It's not clear if any part of the tether would lie in the equatorial plane at all--the only point at which an orbital spacecraft could dock with it. I would welcome any comments on this: it's an interesting problem.
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#12
by
ClaytonBirchenough
on 07 Apr, 2013 15:42
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Ehhh, I think any kind of space elevator needs to be on the equator.
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#13
by
douglas100
on 07 Apr, 2013 16:13
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...My example mission would include a single massive Mars Transfer Vehicle including a tether and a 'Rod from God' anchor. The MTV would approach Mars in a hyperbolic orbit in the equatorial plane, launch the tethered anchor ahead, then reel itself into a tethered orbit above stationary altitude. The elevator car would then use electricity to deliver the colonists to the surface needing no descent, landing or Mars launch reaction mass.
I think "reeling" into orbit around Mars is completely unworkable. You are going to have to dissipate several kilometres a second of kinetic energy through braking the reeling mechanism to slow the vehicle down. (This is assuming the tether doesn't break, the anchor doesn't pull out or the ship isn't ripped apart.)
This should really be in Advanced Concepts.
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#14
by
ARD
on 07 Apr, 2013 16:29
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A space elevator does not have to be on the equator, so simply move the base of the elevator. There will however be a large reduction in the maximum payload.
Is that true? Do you mean the elevator can come in at a slight angle, with the centre of the mass of the whole system still passing through the equatorial plane? Or something else?
It would approach the equatorial plane asymptotically. If you get too far north, it starts to lie horizontally from the view of an observer on the surface--on the Moon, one can get it pretty darn far north. Earth has a limit of 20 degrees, according to this fellow here:
http://www.pbs.org/wgbh/nova/space/edwards-elevator.htmlFixing it to the equator on Earth has a weather advantage.
Mars, I presume, would be somewhat more forgiving in latitude and climate.
The mass of the elevator would probably be high enough that you probably wouldn't want to launch directly from LEO anyway. Then again, I could be wrong--I wouldn't know where to start running the numbers on this.
One can also drop a cable from Phobos to the fringe of Mars's atmosphere. You wouldn't be moving faster than a kilometer per second at the tip of the cable, so rocket-based landing should be trivial at that point.
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#15
by
douglas100
on 07 Apr, 2013 16:52
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It would approach the equatorial plane asymptotically. If you get too far north, it starts to lie horizontally from the view of an observer on the surface--on the Moon, one can get it pretty darn far north. Earth has a limit of 20 degrees, according to this fellow here: http://www.pbs.org/wgbh/nova/space/edwards-elevator.html
Yes, that sounds right. The centre of gravity of the tether would be pulled toward the equatorial plane, but not all of it could lie in the equatorial plane. Thanks for the link.
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#16
by
ClaytonBirchenough
on 07 Apr, 2013 17:27
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It would approach the equatorial plane asymptotically. If you get too far north, it starts to lie horizontally from the view of an observer on the surface--on the Moon, one can get it pretty darn far north. Earth has a limit of 20 degrees, according to this fellow here: http://www.pbs.org/wgbh/nova/space/edwards-elevator.html
Yes, that sounds right. The centre of gravity of the tether would be pulled toward the equatorial plane, but not all of it could lie in the equatorial plane. Thanks for the link.
Probably the problem with having the space elevator not on the equator, the strength of the material used would have to be stronger, no?