NASA hands over $900K for Laser propulsion system LaserMotive has scooped a $900,000 prize from NASA for demonstration of an elevator powered from a ground-based laser. LaserMotive's climber crawled up 1km of rope held in place by helicopter, achieving an average speed of four metres per second and powered by a laser focused onto solar panels on the back of the climber. That …
"I wouldn't fancy it as being very good."
... yet.
People need competitions like this to see what can be done. Once it's proven to be workable, it will inspire entrants and others to work it into something usable (or not). Photon by photon the world becomes the future we were due about 20 years ago :)
This whole nonsense of space tethers and beamed power is stupid.
What they plan to do is (get this...) have a heavy satellite linked to the ground by a tether many thousands of kilometers in length and of almost unimaginable strength. It's incredible. It's ambitious. And it's rubbish.
Why not simply make the tether twice as long, in a loop, and have a pulley at the top and a simple motor at the bottom? No requirement for foolish and inefficient power beaming schemes. Just a simple motor on the ground.
"A loop with a pulley at the top? Well that would be IMPOSSIBLE! Harumph!"
Idiots.
Talked about since the mid 60s, actual hardwware built within a few years of prize being established.
One thing does puzzle me. NASA (particularly JPL) has worked on power transmission by microwave since the mid 1970s for satellite solar power. High efficiency, high power microwave sources are fairly readily available (IIRC 10kw magentrons in the RS catalogue at one time). The design is documented in some detail (in 1 case specifically to drive a deep space probe). A 10kw laser is still a bit hefty, unless NASA supplied this as part of the Govt. Furnished Equipment.
But is there a prize for getting cable to the needed spec? The whole system falls down without this.
Mine's the one with a copy of the Fountains of Paradise in the pocket.
The reason you cannot have a pulley at the top is that there is nothing for it to be attached to. In order to construct a space elevator you need: a cable reaching up to a satellite in geostationary orbit and another cable of equal length on the other side of the satellite with a counterweight to balance the thing. The whole construction is then held in place by centrifugal force.
"Every heard of a circuit?
Hint: requires In and Out, +ve and -ve, Live wire and Earth return.. etc...
Another product from the school of: Science, we've heard of it."
Don't set people up like this. You know fine well the response will be "ok... two cables!", even though you know the real reason is that the Venusians will prevent the Thetans from trying to escape their mortal coils. Of course, non-believers will talk about the resistive load being too high of a circuit that long...
What gets me, is most of the cable is not in geostationary orbit, and so is exhibiting a force downwards on the object that is in the geostationary orbit... surely this is going to effect the geostationary orbit of the satellite? Surely you can't apply unlimited amount of force on the satellite? It must be possible to pull it down for example?
it won't land on the bottom.
The cable is moving faster than the surface of the earth, the lower part not much faster, and the lower part is thin. That falls.
The upper part is going much faster, and although it is ithick, it hits the atmosphere at quite a rate, and burns.
If the break is lower down - in the less strong and thinner part of the cable - then the majority of it rises up out of the atmosphere and stays in orbit.
Leaving aside the experiment you can do with a bucket and some water, and with a rope on the bucket handle if you want to work harder ...
All of the cable is in geostationary orbit.
It isn't something hung from a satellite that magically remains suspended in space, it is a long object whose centre of gravity is in the geostationary orbit and which extends below its centre of gravity to the surface of Earth, or balloon station or wherever, and outward probably for less distance but in a more massive construction a corresponding amount.
If you pull harder on it, part of it moves forward - orbital mechanics is complicated, but this is not a static system.
Extend it quite a way out from the geo/s point and you have a route to the universe - trundle on out, pick a moment, and let go.
If the whole cable is in geostationary orbit, then why are they stating that one of the problems they have with the concept is that they could not currently build cables able to with stand it's own weight that is hanging from the space craft/point at which the cable is sufficiently weightless?
As you get closer to Earth so to be in orbit you have to go faster. Hence it would be technically feasible to be in orbit just above the tree's, but you'd have to be going at one hell of a pace, which would be considerably faster than the Earth's rate of rotation, so making a geostationary orbit impossible at this height.
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