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View Full Version : Short rotovator = bolo

neilzero
2010-May-24, 01:19 AM
My guess is we are close to deploying a short bolo, without a first stage to reach the tip at perhaps 5 kilometers per second, altitude 200 kilometers, briefly at 21 second intervals. The center is orbiting at 8 and the outer tip at 11 kilometers per second, so it can put perhaps one ton in LEO at 240 kilometers in a circular orbit. So the bolo is 20 kilometers radius, with the tips chasing each other at 3 kilometers per second Circumference of the tip path is 62.8 kilometers so the tip speed with respect to the other tip is almost 2.1 kilometers per second. We gain 6 kilometers per second with respect to Earth's surface at the Equator, if I'm not confused. The pay load will experience several g.
If the tether survives a month, it is likely reparable long term with a Dr. Edwards type climber, so we will fund the climber and a vehicle to attach a payload at 200 kilometers at 5 kilometers per second. If it survives less than a month, we will attempt a better tether design and evasive maneuvers to dodge space junk. The Edwards type climber can help dodge the space junk by starting and stopping and reversing direction. This puts traveling transients on the tether which change the tether position (hopefully) by enough to miss the piece of space junk.
The momentum exchange is not free. The bolo will loose altitude and rotational speed with each attachment and each launch, unless there is a means to restore the altitude and tip speed. I suggest a tip rocket at each of the two tips. That means some of the attachments need to be fuel for the tip rockets. In theory we can do about 100 attachments and releases per hour, and serve all the countries of Earth, with a semi polar orbit, so enormous amounts of mass can be orbited even at one ton per launch.
There is also a rather nasty jerk shortly after the attachment of each payload. The tether will stretch significantly, perhaps a lot. The tip rocket can likely reduce the jerk and give the pay load a slight extra boost and direction change at release, if this is desirable for this launch. Neil

mugaliens
2010-May-24, 06:22 AM
Intriguing "guess." Schematics? Blueprints?

Hop_David
2010-May-24, 11:53 PM
My guess is we are close to deploying a short bolo, without a first stage to reach the tip at perhaps 5 kilometers per second, altitude 200 kilometers, briefly at 21 second intervals. The center is orbiting at 8 and the outer tip at 11 kilometers per second, so it can put perhaps one ton in LEO at 240 kilometers in a circular orbit. So the bolo is 20 kilometers radius, with the tips chasing each other at 3 kilometers per second Circumference of the tip path is 62.8 kilometers so the tip speed with respect to the other tip is almost 2.1 kilometers per second. We gain 6 kilometers per second with respect to Earth's surface at the Equator, if I'm not confused. The pay load will experience several g.

I can only hope this is true. Cite?

The momentum exchange is not free. The bolo will loose altitude and rotational speed with each attachment and each launch, unless there is a means to restore the altitude and tip speed. I suggest a tip rocket at each of the two tips. That means some of the attachments need to be fuel for the tip rockets. In theory we can do about 100 attachments and releases per hour, and serve all the countries of Earth, with a semi polar orbit, so enormous amounts of mass can be orbited even at one ton per launch.

If propellent were required to maintain a tether's orbit, there would be less incentive to have a tether.

However, a tether's kinetic engergy can be increased without propellent.

Wikipedia's electrodynamic tether artcie (http://en.wikipedia.org/wiki/Electrodynamic_tether)

If there were payloads incoming from higher up the gravity well, these could add momentum thus balancing momentum lost by capturing suborbital loads. But this type of balancing act isn't viable until we have two way traffic.