h a l f b a k e r y"Bun is such a sad word, is it not?" -- Watt, "Waiting for Godot"
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mass in orbit is very precious and VERY energy intensive to
get into earth orbit.
getting mass from the moon's surface to low earth orbit is
actually about HALF as energy intensive as getting it to low
earth orbit FROM THE SURFACE OF THE EARTH.
furthermore , because the moon has no atmosphere,
launching mass from lunar surface to low earth orbit requires
NO concern for aerodynamic drag (other than using aero-drag
of the earths atmosphere to slow down and lay easily into LEO
with the lowest possible use of fuel).
this is a major difference. if you had raw mass on the moon
versus raw mass on Earth, it would cost half the energy
budget AND have no design constraints dealing with
atmospheric problems.
THUS, you can potentially launch mass to low earth orbit
using SLOW and persistent ENERGY BEAMING from lasers.
thus-------------the question then becomes why?
LOW earth orbit is a great place to build and field sattelties,
fuel dumps and other sources of energy for sattelites, space
stations, and potentional future missions to deep space and
other planets.
the moon has plenty of raw mass in the form of oxygen,
hydrogen silicon and other elements that can easily be
delivered FAR MORE CHEAPLY to low earth orbit than from
earth. furthermore, the mass could be moved on a continuous
basis is small modular amounts due to the fact that a laser
can be used to boost small packages of mass into space
through persistent ablation.
ablation has been proven on earth to work, only its severly
limited to to both aerodynamic DRAG and more so , due to
laser attenuation in the atmosphere.
with a modular lunar payload, it could be virtually any shape
it wants to be , it can accelerate far more slowly without
having to contend with any drag and the subsequent high
speed shockwaves and vibration of a launch vehicle from
earth AND MOST IMPORTANTLY the lunar laser could power
the package continuously for a far longer period of impulse
than any remote power beaming that could be accomplished
from earths surface through the atmosphere.
[link]
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[slab]! You're back! And you've spent your time away in the science fiction section of the library! I'm very pleased. |
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Oh...it's in other:general. Do we have to do this all over again? |
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I'm just not sure about the "slow" part. You need to achieve lunar escape velocity (2.38 km/s) to not orbit back to where you started. Other than that, it is an old but good idea. |
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the novelty of the idea is really that you can use a laser to
go 'slow' in the sense that you can impart the energy
relatively slowly because the atmosphere is not getting in
the way. that means you can impart the energy continuously
for as FAR as possible from laser source to LEO. meaning you
cna use as low power a laser as possible, making the entire
endeavor more possible. |
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Which way are you pointing the laser? Pointing it straight up, I sense that once you push the mass over the "hill" between the two gravity wells, it will plummet into the Earth due to it having some fraction of the Moon's orbital velocity. |
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So, don't you have to angle the laser to speed the mass up as you raise it? Is that even possible? |
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OK, so I'm envisioning a long railgun type system that gets the payload to orbital velocity, with a few lasers positioned around the lunar equator to provide additional orbital energy post-launch, placing the payload in lunar orbit. From there, you can slowly raise the orbit to the point where it goes 'over the hill' and enters earth orbit. As long as it goes over the hill with a trajectory that places it outside of common orbits, you can wait until it comes back around and hit it from the front to slow it down and slowly lower the apogee. From here, it's just a matter of time, as you can continue to lower its orbit a little at a time. |
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Now here's a kicker, and a point which would require serious trade studies: A long, slow raising of the orbit is less efficient than a Hohmann transfer, so would take more energy than an insertion burn. On the other hand, you're not carrying your fuel with you, so there's less mass to accelerate, reducing your energy requirements. |
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There are other engineering challenges as well, but this doesn't sound outside the range of possibility. |
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Lossy: what would you get, inverse root 2 efficiency at most ? |
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// inverse root 2 efficiency at most // That would
be about 71% |
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hmm ? whoops... 67% for exhaust distribution from a flat surface. |
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