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.
-- teslaberry, Apr 20 2015

[slab]! You're back! And you've spent your time away in the science fiction section of the library! I'm very pleased.

Oh...it's in other:general. Do we have to do this all over again?
-- normzone, Apr 20 2015


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.
-- neutrinos_shadow, Apr 21 2015


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.
-- teslaberry, Apr 23 2015


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.

So, don't you have to angle the laser to speed the mass up as you raise it? Is that even possible?
-- the porpoise, Apr 24 2015


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.

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.

There are other engineering challenges as well, but this doesn't sound outside the range of possibility.
-- Freefall, Apr 24 2015


[+]

Lossy: what would you get, inverse root 2 efficiency at most ?
-- FlyingToaster, Apr 24 2015


// inverse root 2 efficiency at most // That would be about 71%
-- MaxwellBuchanan, Apr 24 2015


hmm ? whoops... 67% for exhaust distribution from a flat surface.
-- FlyingToaster, Apr 24 2015



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