Mining the Sky & Space Tethers to achieve LEO

From: Dr. Omni
To: spacesettlers@egroups.com
Sent: Monday, December 11, 2000 10:09 AM
Subject: Re: [spacesettlers] 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
.)
Tom - I'll have to check it out.

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.

Tom - I haven't seen this particular proposal. It is true that a significant investment would be required, but a two hundred weight, partially made-up of spent boosters, would suffice, and conventioal materials are suitible for the tether per the analysis I've seen. Either nuclear or solar power can be used to charge, or replace the orbital velocity lost when picking up a payload. Nuclear could recharge in a couple of weeks and solar around 9 months depending upon final configuration.
I think it is time for fresh thinking in this arena. Perhaps we are trying to do the equivalent of flying to NY and back without realizing the need for a major airport at our destination? A single or even a dozen flights would be very expensive since we would have to take all of our fuel with us and landing/take-off would be difficult at best. The massive investment to build an international airport is not obvious to early air travelers, just as the need to build/invest in space facilities to reduce the costs of LEO are not obvious to us today. The key question is what would be the payback period and how long would the facility last in orbit?
How much would it be worth to the space, tourist industry if costs to LEO and to orbit near the moon were brought down to around $50/lb? Would an investment of 100 billion be cost-effective? What about 200 billion? The key is projecting tourist demands since they will be the initial paying customers.

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?

Tom - Pictures are really needed to illustrate, but I will give a high-level overview. The tether rotates much like a croquette mallet if tossed into the air. The counter-weight is about 100 to 200 tons and includes a power source to boost orbit using current interaction with the earth's magnetic field. The end of the tether has a grapeling device that dips down into the atmosphere just when a space plane is at the peak of it's "pop up" and it grabs the payload and pulls it into orbit. See the tether web site for papers for details. There are over 150 of them, and NASA is funding some of the research.
Drawbacks:
1) orbital velocity may not be provided by the tether.
2) rendezvous between tether and payload may be dicy at best,
3) There may be a better way than using a tether.

Regards,

Tom Tucker

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

From:
Dr. Omni
To:
spacesettlers@egroups.com
Sent:
Monday, December 11, 2000 10:09 AM
Subject:
Re: [spacesettlers] Mining the Sky & Space Tethers to achieve LEO
From: "Tom Tucker (Olympia)" <
tntucker@...
>
To: <
spacesettlers@egroups.com
>
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
.)
Tom - I'll have to check it out.
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.

Tom - I haven't seen this particular proposal. It is true that a significant investment would be required, but a two hundred weight, partially made-up of spent boosters, would suffice, and conventioal materials are suitible for the tether per the analysis I've seen. Either nuclear or solar power can be used to charge, or replace the orbital velocity lost when picking up a payload. Nuclear could recharge in a couple of weeks and solar around 9 months depending upon final configuration.
I think it is time for fresh thinking in this arena. Perhaps we are trying to do the equivalent of flying to NY and back without realizing the need for a major airport at our destination? A single or even a dozen flights would be very expensive since we would have to take all of our fuel with us and landing/take-off would be difficult at best. The massive investment to build an international airport is not obvious to early air travelers, just as the need to build/invest in space facilities to reduce the costs of LEO are not obvious to us today. The key question is what would be the payback period and how long would the facility last in orbit?
How much would it be worth to the space, tourist industry if costs to LEO and to orbit near the moon were brought down to around $50/lb? Would an investment of 100 billion be cost-effective? What about 200 billion? The key is projecting tourist demands since they will be the initial paying customers.

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?
Tom - Pictures are really needed to illustrate, but I will give a high-level overview. The tether rotates much like a croquette mallet if tossed into the air. The counter-weight is about 100 to 200 tons and includes a power source to boost orbit using current interaction with the earth's magnetic field. The end of the tether has a grapeling device that dips down into the atmosphere just when a space plane is at the peak of it's "pop up" and it grabs the payload and pulls it into orbit. See the tether web site for papers for details. There are over 150 of them, and NASA is funding some of the research.
Drawbacks:
1) orbital velocity may not be provided by the tether.
2) rendezvous between tether and payload may be dicy at best,
3) There may be a better way than using a tether.

Regards,

Tom Tucker
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