Bullwhip To Space?

Factual Questions
1

The thought processes behind this one are something I’d rather not get into at the moment, but I just had an idea…

Ok, so to start off with, the bullwhip. Everybody knows what I’m talking about… handle, length of rawhide, ya flip yer wrist and CRACK! sonic boom, right?

So what’s actually going on here? It’s an energy-condensing machine of some sort or other… you input kinetic energy into the handle, and with just the right motion can condense it all to the tip at one moment. This provides the massive acceleration needed to propel that tip through the air fast enough to break the sound barrier, and ya get a little sonic boom.

Now, we’re already working on the Space Elevator, which is science-fiction-hopefully-turning fact. The concept here is that you tether an orbiting station to the earth, and let the natural rotation pull that tether tight… holding the station in place, and providing a ‘beanstalk’ if you will. Then ya just run elevators up and down the tether, and presto, no more giant booster rockets needed.

Ok, granted, the technology doesn’t exist, yet. But we’re working on it.

So what if we designed something similar, but decided that we wanted to use it not as an orbiting platform, but as a means of launcing vehicles into space? Sure, you can do that from the one ‘they’ are working on, that’s kinda the whole point, but one specifically designed for this and nothing else?

In particular, one that ONLY served to launch vehicles?

I mean, send a payload up the elevator. Then, at the right moment, start shaking the everliving crap out of the tether… get the oscillations JUST right, and snap the outerspace end of it, just like a bullwhip, at the exact moment the payload is on the tip… and WHOOOSH, that sucker goes flying at a substantial portion of the speed of light. Or something.

Besides the obvious problem of there being no such thing as a space elevator, would this even work?

Maybe I should get some sleep.

2

The idea is an interesting one and there are certainly effects that hypothetically could be exploited in such a way, but creating materials that could withstand the stresses involved would probably be impossible, as would hardening your payload (or worse still, passengers) against the sudden acceleration.

3

A whip is like a lever; it converts a slow powerful motion into a fast but less forceful motion. I don’t think such a mechanism will be of any use to a spacecraft. When it comes to interplanetary travel, a slow steady acceleration is perfectly acceptable.

Anyway, if you already have a space elevator, I think it would be a simple matter to build an extention that functions as a railgun to accelerate spacecraft. Or if you build a long enough extention to the space elevator, centrifugal force alone will accelerate the spacecraft along the rail/tower and into interplanetary space.

4

OK i read this book about a year ago but cant remember the title. Anyone know it?

5

If it works (and I doubt it would, for the aforementioned materials problems) I propose that every usage must be accompanied by the Indiana Jones theme.

6

Found it “The Web Between The Worlds” by Charles Sheffield and Arthur C. Clark

7

Assuming you have a standard geosynch tether, with the far end serving as your counterbalance, how fast would the tip be moving? Escape velocity?Earth-Mars transit trajectory?

8

I think the suddenness of the accompanying g-forces would be insurmountable.

9

At geo-sync speed like all ther geo-sync satelites that are up there.

They are 0 mph in relation to us.
They are any speed you want depending on your reference point.

10

I think the book you are thinking about is “The Fountains of Paradise” by Arthur C. Clarke.

11

The answer is, anything above geosync velocity that you like. It depends how much the total lengh of the thing is, and while there is a lower limit there is no theoretical upper limit.

All parts of your tether have to have a 24 hour period. Only the part at geosync height (35800 km) is in orbit, the parts below that are below their orbital speeds and trying to fall, the parts above that are above their orbital speeds and trying to fly off. Clearly you have to arrange it so that stuff trying to fly off will at least counterbalance the stuff trying to fall, but you can take it as far as you like beyond that - it just increases the tension in your tether. You can have a short tether above the geosync height with a bloody great rock on the end of it to hold the whole thing up, or you can have another hundred thousand km of tether if you want.

A related question is, what length of tether would you need so anything released at the end of it is at Earth escape velocity? Not sure how easy it would be to work out, since escape velocity falls the longer the tether gets.

12

Okay, I’ve done my sums.

Assuming Earth’s radius is 6400 km and 9=9.81 m/s/s at the surface, and gravity decreases with the inverse square of the distance from the centre, then:

For a geostationary tether of length 46960 km, the tip will just be at Earth escape velocity at that height. Send something to the top and let it go and it will keep getting further away for ever, other bodies permitting.

With a shorter tether, let something go at the top and it will go into some kind of Earth orbit, although considerably higher than the tether itself.

That isn’t a particularly long tether considering that it must to be longer than 35800km in order to stay up. No whip cracks necessary!