A Conversation for Space Travel, Propulsion and Other Minutiae

No such thing as a free launch?

Post 1

Brussels Sprout

Well there isn't.

You have to expend a great deal of energy to get anything into orbit around the Earth - let along break completely free of its gravitational pull.

So, where are we going wrong?

Simply put, we use a great deal of energy to push things away from the Earth. It would be much more effective to pull things away from the Earth.

This is where a cute idea from that physics smarty-pants, Arthur C. Clarke comes in. (You know, the guy who had the idea of putting satellites in geostationary orbit for communications use). He proposed making a "skyhook" which would be attached to a small asteroid in orbit around the Earth. Then you have an elevator all the way to space! Sure, it would need an awful lot of small green pieces of paper to build the skyhook, but then you could take anything you wanted into low-Earth orbit at a very low cost per kilo.

Anybody know if the materials technology exists on Earth yet?

No such thing as a free launch?

Post 2


i'm pretty sure that even with the amout of red tape the US seems 2 create whenever someone proposes something like this, they would have done it by now, if they had the technology, you will probably be waiting untill someone manages 2 find an easy way 2 manufacture diamond by putting carbon atoms together!

No such thing as a free launch?

Post 3


Read Red Mars

No such thing as a free launch?

Post 4

Daniel the 49290th

Plus, wouldn't it be possible to regain energy from it?

If there is an 'elevator', then after you lift stuff up, you would have to send if down again... If you used Earth's gravity to bring it down (you'd have to give it a push at the start to get it out of the Clarke orbit (yes, it was named after him!)), then you could use a simple generator to obtain elecricity, which could then be stored for the ascent. It couldn't power itself, obviously, but it would make it cheaper...

No such thing as a free launch?

Post 5

Daniel the 49290th

Oh yeah, Marvin, is Red Mars (and the other two!) any good? I was thinking of buying them...

No such thing as a free launch?

Post 6

The Wisest Fool

Assuming there is this 'asteroid' thing at the top of the elevator. What would happen if something reasonably big (e.g. small meteorite) hit it at speed?
I bet it would make a really eery whistling noise when the wind blew past it.

No such thing as a free launch?

Post 7


What would happen if it didn't get hit by a meteorite?

After all a few million tons of rock aren't going to be any bigger than your average town and how often do they get hit by meteorites big enough to do any damage.

Yes you could recover some electricity from goods on the way down, probably using direct induction rather than a generator.

The best material to use would be something developed in the same labs that produced carbon60 - it's a kind of chain molecule that they claim approaches the theoretical limits of strength and would (almost) certainly do the job.

The best book to read is "The Fountains of Paradise" by Sir Arthur.

I've also just done a guide entry which explains it all fairly simply - but I'm having trouble adding anything at the moment so it's still on my word processor. I'll try again and you may be abe to get to it from my home page.


No such thing as a free launch?

Post 8


Hi, there is a lot of stuff about uses for the recently discovered form of carbon molecule called Buckminsterfullerine (Honest!)
Also known as "Bucky balls". I read somewhere on the net that this material is being investigated as a source of a suitable cable.

No such thing as a free launch?

Post 9

Jedi Jane Vega

Actually, there is some research being done at NASA and here at the University of Michigan on a variation of Bucky balls called "nanotubes". These are basically buckyballs with the ends cut off to form tubes. They are orders of magnitude stronger than normal materials.... Unfortunately, they also form on the nanometer scale (hence the name) and it is unlikely we'll get the stuff in any usable quantity for quite some time.

No such thing as a free launch?

Post 10


Does it matter if it might take a while? Those of us under 40 today have a miniscule, but still significant chance, of living a very long time. It took 500 years between Leonardo conceiving the helicopter before it actually took off.
Regarding the expense, if you were to launch all the material to build a space elevator from Earth then it would cost more than everything mankind has ever done all put together. However, that would be a silly way to go about it. In 20 years or so a 'cheap' affordable launch system could easily be viable, so you could just go and grab any old asteroid, stick it into geo-stationary orbit, and then unleash all those nanomachines you'll need anyway to make the Buckminsterfullerene, and then just sit back and wait.
I really recommend Red Mars etc as an example of space elevators and longevity, and of the new politics and societies space exploration would possibly engender.

No such thing as a free launch?

Post 11


Hello again,

The space elevator deserves it's own entry and it's at http://www.h2g2.com/A179787

It's been submitted so I would be really grateful if all you experts could give me your input (via email from my homepage is easiest).

I'll revise it in the next few days to take account of the forum entries above.

No such thing as a free launch?

Post 12


The H2G2 Interplanetary Society is meeting at http://www.h2g2.com/a190180

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