Mining the Sky & Space Tethers to achieve LEO

From: "Tom Tucker (Olympia)"
To:
Sent: Segunda-feira, 11 de Dezembro de 2000 02:09
Subject: Re: [spacesettlers] Mining the Sky & Space Tethers to achieve LEO

[snikt]
IMO, the earth's gravity well is too deep for a single plane or stage to
orbit (i.e. STO) vehicle to work unless we somehow discover anti-gravity
:-). This is why I am examining the tether approach. You see, what is the
tether could build-up speed in LEO using nuclear or solar power, and then
dip down to pick-up the payload from a Boeing space plane at say 100KM? Why
go all the way to orbit when something in orbit could work as a team and
meet you half-way, so to speak? Lets think outside of the box and not be
tied to the notion that we have to have a single vehicle that can
independently go from earth to LEO un-assisted.

I agree that space tethers would be the cheapest way to go into orbit (after
a huge initial investment, of course). However, I'm not that skeptical about
a STO vehicle. As Darren said in another message, the LightCraft concept -
where the vehicle would not have to use any propellant during part of the
ascent and would have to use much less propellant from that point on - seems
very promising; moreover, theoretical calculations for the LightCraft are
sound, IMHO. (See http://www.sciam.com/1999/0299issue/0299beardsleybox4.html
.)

The great appeal of STOs is that they would need no startup investment in
space in order to reach space in a cheap way. Space tethers as I know them
would require gargantuan tasks in space, far beyond our current technology,
like putting a carbonaceous asteroid with a few cubic kilometers into
geosynchronic orbit and then building a cable made of carbon nanotubes
(nowadays a material far more expensive than gold) till touch Earth. A STO,
on the other hand, would be made on Earth and would be several orders of
magnitude cheaper, and they so they are the next logical research target
until all possibilities are exhausted.

>From your text above, I think that the site that you linked in your other
message proposes other kinds of space tethers; unfortunately, the site was
down when I tried to access it. Would you please explain briefly the
principles involved?

Zubrin also points out that the major rocket manufacturers have absolutely
no incentive to reduce the cost to LEO since they feel that they would be
cutting their own financial throat. Independent efforts are indicated and,
IMO, the winner may not be flown from US soil at the rate we are going now.

No wonder that the LightCraft project is under USAF, if I remeber
correctly...

Cheers,

Cheers,

Tom

Lucio