New group for Space Tethers

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
> Al Globus wrote:
> > Tethers are, obviously, useless for launch from Earth
>
> Rotating tethers have been credibly proposed to latch on to a
> single-stage launch vehicle. This makes the launch vehicle /much/
> smaller and improves the payload.

Right. You do need a suborbital rocket. But it is much easier
to make a reusable suborbital rocket. Also, the rocket is going
to be much smaller and not have such tight weight margins.
You can do it where the rocket needs to be able to do like
5 km/sec instead of 9 km/sec. So any of the "flyback boosters"
or maybe the Falcon-1 first stage could work.

> Once latched on, the remaining delta-v can be provided by a high
> ISP thruster, and because the launch vehicle is dropped off
> before adding the delta-v, you can get significant reduction
> in the fuel required.

Right, the fuel for a 10,000 second ISP ion-drive give you
10,000/400 or 25 times less reaction mass for the same
momentum.

But you can do even better than this. You can actually push
on the Earth's magnetic field and so get by with no reaction
mass. This is called an Electrodynamic Tether or EDT. It
has been tested for breaking orbital speed by generating
electricity, but has not been used to accelerate any sat yet.

-- Vince