3 ms·

Attaching the payload would indeed pull on the line, since the payload wouldn't have the velocity to maintain itself in that orbit, and so would need an upward

Attaching the payload would indeed pull on the line, since the payload wouldn't have the velocity to maintain itself in that orbit, and so would need an upward force from the line to not fall down. The line would of course need to be designed to handle that, as well as the increased load as the payload is hoisted up to the moon.

banku_brougham 7y ago
Why is it less energy expended to hoist a load on a line than to use rocket propulsion?
- radford-neal 7y ago
  Well, whether it takes less energy would obviously depend on how the hoisting is done. But one advantage is that you can hoist slowly if that's advantageous, whereas you can't do things slowly with a rocket, at least until you've achieved orbit. Also, if we start with a rocket+fuel on earth, and end with a rocket on the moon, there's an inevitable input of energy to move the rocket to a location of higher gravitational potential, that would have to be provided with hoisting as well, but there's also be a lot of rocket exhaust (formerly fuel) that's now zipping around the solar system, carrying away energy.
- mynegation 7y ago
  To attempt a generalized version of sibling comment from radford-neal, the energy that goes specifically into changing the position of the payload is the same, but how much of the total energy spent goes into that, depends on the method. For the rocket energy goes into so many things other than lifting the payload: kinetic energy of the exhaust, high temperature, sound, and - most importantly - lifting the fuel itself, quickly. Or to think another way think of all the challenges with human powered helicopter where the record is reaching 3.3 meters in 64 second flight, whereas any moderately physically fit person can climb the same height on the rope much faster and hang out there indefinitely, because they did not have to lift the weight of the helicopter and send the big masses of swooshing air down from the blades just to combat the force of gravity.
- Tepix 7y ago
  You don't need to carry rocket fuel to do it. You can use solar energy.

banku_brougham 7y ago

Why is it less energy expended to hoist a load on a line than to use rocket propulsion?

radford-neal 7y ago
Well, whether it takes less energy would obviously depend on how the hoisting is done. But one advantage is that you can hoist slowly if that's advantageous, whereas you can't do things slowly with a rocket, at least until you've achieved orbit. Also, if we start with a rocket+fuel on earth, and end with a rocket on the moon, there's an inevitable input of energy to move the rocket to a location of higher gravitational potential, that would have to be provided with hoisting as well, but there's also be a lot of rocket exhaust (formerly fuel) that's now zipping around the solar system, carrying away energy.
mynegation 7y ago
To attempt a generalized version of sibling comment from radford-neal, the energy that goes specifically into changing the position of the payload is the same, but how much of the total energy spent goes into that, depends on the method. For the rocket energy goes into so many things other than lifting the payload: kinetic energy of the exhaust, high temperature, sound, and - most importantly - lifting the fuel itself, quickly. Or to think another way think of all the challenges with human powered helicopter where the record is reaching 3.3 meters in 64 second flight, whereas any moderately physically fit person can climb the same height on the rope much faster and hang out there indefinitely, because they did not have to lift the weight of the helicopter and send the big masses of swooshing air down from the blades just to combat the force of gravity.
Tepix 7y ago
You don't need to carry rocket fuel to do it. You can use solar energy.