I agree with all your points except the fourth. Once outside the atmosphere and up to speed, rockets are actually pretty efficient. The space shuttle main engines achieved 15% propulsive efficiency if I remember correctly; this is better than many land vehicles.
I’ve studied launch loops and they have massive power requirements, on the order of magnitude of heating up the atmosphere significantly (up to a degree or so). Space elevators can be efficient, if the power delivery system is efficient, and so far all workable proposals (laser power beaming, conductive cables) seem extremely inefficient.
Rockets are in many ways the ideal space launch system, the major disadvantage being enormous unit cost.
Once outside the atmosphere and up to speed, rockets are actually pretty efficient. The space shuttle main engines achieved 15% propulsive efficiency if I remember correctly; this is better than many land vehicles
Yes, but getting out of the atmosphere is really inconvenient.
Do you have a citation or a back of the envelope for the statement about launch loops having such large power requirements? I don’t think I’ve seen that before, and I’d be interested in seeing that.
100 billion tons/year may sound like a lot but you really do need to launch that much cargo in order to recuperate construction and operation costs. The 0.1 degree heating cited on that page is a bit optimistic since it doesn’t take into account secondary effects.
Is the claim that launching a ton of payload by launch loop heats the earth more than launching a ton by rockets? That is very hard to believe. To a first approximation, the energy savings of the launch loop are heat savings.
Or is the claim that launching enough payload to make a launch loop worthwhile is too much heat, either way?
I agree with all your points except the fourth. Once outside the atmosphere and up to speed, rockets are actually pretty efficient. The space shuttle main engines achieved 15% propulsive efficiency if I remember correctly; this is better than many land vehicles.
I’ve studied launch loops and they have massive power requirements, on the order of magnitude of heating up the atmosphere significantly (up to a degree or so). Space elevators can be efficient, if the power delivery system is efficient, and so far all workable proposals (laser power beaming, conductive cables) seem extremely inefficient.
Rockets are in many ways the ideal space launch system, the major disadvantage being enormous unit cost.
Yes, but getting out of the atmosphere is really inconvenient.
Do you have a citation or a back of the envelope for the statement about launch loops having such large power requirements? I don’t think I’ve seen that before, and I’d be interested in seeing that.
I don’t remember exactly where I read that, but here’s a page with some power calculations: http://launchloop.com/LaunchLoopHeating
100 billion tons/year may sound like a lot but you really do need to launch that much cargo in order to recuperate construction and operation costs. The 0.1 degree heating cited on that page is a bit optimistic since it doesn’t take into account secondary effects.
Ouch. Yeah, that’s not reasonably viable.
What, exactly, is the claim?
Is the claim that launching a ton of payload by launch loop heats the earth more than launching a ton by rockets? That is very hard to believe. To a first approximation, the energy savings of the launch loop are heat savings.
Or is the claim that launching enough payload to make a launch loop worthwhile is too much heat, either way?
Good point. Hmm, now I’m confused.