'Space elevator' would take humans into orbit | Hacker News Reader

'Space elevator' would take humans into orbit

edition.cnn.com

4 pointslancashire10 comments

I had an idea yesterday about the minimum distance needed. Now, I have yet to work the math on this one but, rather than a 32,000 mile long elevator why not try sticking something from the equator to just above LEO, and using a series of orbiting satellites (or a cable around the earth) to keep it up (you would need to deflect them). Granted you still need to add orbital velocity but if you can get a useful amount of mass stable at that altitude you could build a pair of them to safely get something into orbit using a long rail gun between two of them.

I don't think it's stable but if you wanted to move a huge amount of mass out of the gravity well it might work.

It sounds like an orbital ring: http://en.wikipedia.org/wiki/Orbital_ring

Sounds fascinating, using rail guns. Neat!

Let's try to find out what I don't understand about what you just said.

You have a too-short elevator.

You have satellites.

The satellites are going too fast for their orbit, and by "deflection" they push up the anchor of the elevator as they pass underneath?

What relationship do the "pair" of space-elevators have to each other? What would the rail gun be for?

Maybe you are thinking of an upside-down maglev train riding eastward at greater than 17,000 miles per hour, on a track that circles the earth, several hundred miles above the equator. The track is held down by guywires angling out to the sides.

By the way, have you read this?

http://www.spaceelevator.com/docs/acclarke.092079.se.1.html

The Space Elevator: 'Thought Experiment', or Key to the Universe?

It's probably a dumb idea, but I am more interested in what's wrong than what's correct. The basic idea is static force to keep something from falling but that does not mean it's takes any energy.

So, can you get a stable orbit that includes a single strong deflection in the direction of the earth? It's probably close to impossible due to targeting issues but in theory I think you can.

Now as long as what's doing the reflection is not moving there should not be a significant exchange of energy between the two objects. Just lift on what's doing the deflecting and if there is some drag you could probably add energy from the tower to the satellites even as they provide static lifting force.

Ok, well to lift something you need some extra force extracted from the orbiting satellites, but the energy to do the lifting is not taken from the orbiting satellites it's taken from the elevator / what's moving the car and you can just try an lift the ground when not lifting the car's weight. So, you could build an elevator that picks up car from the ground to above the atmosphere but the car is not going to have much orbital velocity as it's not at a Geosynchronous altitude.

PS: I really like the idea of a space elevator but 32,000 miles is a long way and would take a lot of vary strong stuff.

Edit: As to the orbital train idea think about removing the track and extending the train the full orbit.

Edit2: Now to get some orbital velocity you could magnetic car that get's lift and energy from the moving rail to get into orbit. You would want to get into orbit before reaching the station again but you could do that with less than 3G.

can you get a stable orbit that includes a single strong deflection in the direction of the earth?

You are referring to an eliptical orbit, right? The satellite in this elliptical orbit bounces against a space-elevator anchor at apogee, right?

you could probably add energy from the tower

What tower? You never mentioned a tower.

the car is not going to have much orbital velocity as it's not at a Geosynchronous altitude.

Indeed. So, what is the point of this too-short space-elevator?

Indeed. So, what is the point of this too-short space-elevator?

It's just the seed of an idea. But, I was wondering what the shortest useful length you could make a space elevator and getting out of the atmosphere seems to give you a lot of options.

Well, like you said, getting out of the atmosphere gives you the option of using a rail-gun (electronic catapult), but you could launch satellites from the roof a tall building, the same way. A 100-mile wide, 100-mile tall cylindrical building could have a circular track on top, or spiraling up to the top, that could perhaps be long enough to accelerate objects to orbital velocity.

Umm, yea that's what I call freaking huge but it could probably work.

The space elevator is miles off, so...

I put my money on Elon Musk and SpaceX to make space travel cheap enough in the meantime, until we can build the elevator. Got to focus on the short-term, the elevator is long-term.

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