Sgt.Squarehead Posted April 19, 2013 Share Posted April 19, 2013 (edited) Why lift your fuel/reaction mass when you can utilise the atmosphere and direct energy transfer: Skip to 2:30 for the good bit! http://en.wikipedia.org/wiki/Laser_propulsion Edited April 19, 2013 by Sgt.Squarehead Link to comment Share on other sites More sharing options...
eagle Posted April 19, 2013 Share Posted April 19, 2013 (edited) My first prognosis is that the device would appear to rely on the presence of air .As the craft would rise the air would decrease therefore reducing the efficiency of propulsion .And indeed would not work in space as there is no air. The device is limited by it operation to attain only half the height expected and would reach a ceiling of usefulness. Perhaps only 10 miles high. Where the edge of space is some 20 miles high . Their efforts would be better put to use if they came up with a ladder that was 22miles long. And then they could ascend to space in a more conventional means such as a lift mechanism attached to the ladder. Edited April 19, 2013 by eagle Link to comment Share on other sites More sharing options...
Sgt.Squarehead Posted April 19, 2013 Author Share Posted April 19, 2013 (edited) You mean like a space elevator ? Now if we could get our act together and build one of those, our problems as a species would largely be over.....Which presumably is why there is no official interest in them whatsoever. Not sure how much potential they have as a subject for modellers though. The proposed lightship design does include internal propellant for use in the final stage of the ascent and orbital maneuvering, but the vast bulk of the lift is performed using the laser, hence making the craft much more efficient than any conventional rocket. Also for the first ten miles of the lift the craft would actually be generating Ozone in its exhaust plume rather than destroying it. Edited April 19, 2013 by Sgt.Squarehead 1 Link to comment Share on other sites More sharing options...
pigsty Posted April 19, 2013 Share Posted April 19, 2013 Now if we could get our act together and build one of those, our problems as a species would largely be overThis bit I understand......Which presumably is why there is no official interest in them whatsoever.This bit I don't. It requires all the world's governments to say, in effect, "we can see all these problems and we're going to do nothing about any of them, ha ha ha", which seems a little unlikely. Could the reason there's no interest actually be that a space elevator is impossible with current technology? Link to comment Share on other sites More sharing options...
eagle Posted April 19, 2013 Share Posted April 19, 2013 A space ellevator is viable and currently nasa are exploring a cable system by way of glasgow uni. However my way is better as a ladder will provide a safety system for ehen the lift breaks down. Lifts have previous for such events. I see no solid reason why a solid structure could not pass from the ground to the edge of space providing it has a solid structure. 20 miles on a motorway is nothing all we need to do is build vertical 20 miles up. There you are i have set the way for the british federation of space. Link to comment Share on other sites More sharing options...
pigsty Posted April 20, 2013 Share Posted April 20, 2013 Er ... you do know it's not just a tower twenty miles high? A space elevator has to reach at least as far geostationary orbit, which is over 22,000 miles, and the tether has to be strong enough to withstand the forces that would be trying to pull it apart. See here for some more detail. Link to comment Share on other sites More sharing options...
eagle Posted April 20, 2013 Share Posted April 20, 2013 (edited) Er ... you do know it's not just a tower twenty miles high? A space elevator has to reach at least as far geostationary orbit, which is over 22,000 miles, and the tether has to be strong enough to withstand the forces that would be trying to pull it apart. See here for some more detail. Space begins at 22miles up that's rarified air and weightlessness .If you park your space vehicle there you can use much less energy and go where you want. The ISS is only 250 miles up.The x program gets up to about 60 miles. A space elevator is a fairy story Edited April 20, 2013 by eagle Link to comment Share on other sites More sharing options...
Sgt.Squarehead Posted April 20, 2013 Author Share Posted April 20, 2013 (edited) Space elevators are perfectlly plausible, there are a number of private companies looking at the technologies, with little or no official help whatsoever.....Keep in mind that Daimler & Benz, and the Wright Brothers weren't working on official projects, but you certainly can't discount their inventions. Edited April 20, 2013 by Sgt.Squarehead Link to comment Share on other sites More sharing options...
pyro-manic Posted April 25, 2013 Share Posted April 25, 2013 http://en.wikipedia.org/wiki/Beam-powered_propulsion#Direct_impulse Space begins at 22miles up that's rarified air and weightlessness .If you park your space vehicle there you can use much less energy and go where you want. The ISS is only 250 miles up.The x program gets up to about 60 miles. A space elevator is a fairy story A "tower 20 miles high" is nigh on impossible - such a construction would crush itself under it's own weight, or be so vast at it's base as to be impractical. There is no building material light enough (and abundant enough) that could do the job. And the ISS is not "fixed" - it orbits rapidly and requires frequent boosts to maintain/adjust it's orbit. If you "park your space vehicle" 22 miles up it will not stay there for very long! Link to comment Share on other sites More sharing options...
eagle Posted April 25, 2013 Share Posted April 25, 2013 You need to look at the Burj Khalifa. Link to comment Share on other sites More sharing options...
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