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Lunar Sample Return via Tether



 
 
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  #1  
Old December 7th 03, 02:49 AM
Vincent Cate
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Default Lunar Sample Return via Tether

My father (Henry Cate) and I have come up with an initial tether project
that might be fun, affordable, and profitable. The idea is to use a
rotating tether to pickup some Lunar samples, bring them back to Earth,
and sell them.

The Apollo Lunar Orbit Rendezvous was a big win because they did not need
to land their return vehicle or fuel on the moon, just the lander. With a
rotating tether we could win even more by only having a small scoop at the
end of the tether touch the moon.

Since there is no landing vehicle, we can also use a high ISP ion drive the
whole time. By lifting a small scoop of regolith (probably under 10 Kg,
maybe under 1 Kg) many times we could lift a reasonable total mass of
lunar regolith using a small tether. For the 1.6 km/sec tip speed of a
tether for lunar pickup, the tether only needs to be like 3 to 10 times
the payload mass. The ion drive has to replace the momentum before the
next pickup.

The Dnepr at $10 to $13 mil for 9920 lbs (4500 Kg) to LEO seems like a
good deal.

http://www.spaceandtech.com/spacedat...nepr_sum.shtml

Starting with a 4500 Kg vehicle in LEO we use an ion-drive to go to the
moon, spin up a tether (probably winching in and out 2 tethers), and start
picking up samples when the end of the rotating tether touches the moon.
After picking up enough that it is running low on fuel, it could head back
to earth and have a capsule reenter with the samples.

The question of how many Kg of lunar sample you could bring back depends
on a lot of things, like ISP of thruster, watts/Kg for solar, ratio of
capsule mass to payload mass, how long the mission can be, etc. To really
get a detailed answer would take some real work. You can also trade off
time and mass returned to some extent (higher ISP can bring back more but
takes longer). Our initial guesstimate is that you could return between
1,000 Kg and 10,000 Kg in something like 1.5 to 4 years.

All of the Apollo missions combined returned 381.7 Kg. The Apollo costs
have been estimated at $100 billion in 1994 dollars (next URL). If this
project can be done for $50 million (not by NASA for sure) then this would
be like 2000 times cheaper and return 2.5 to 25 times as much. :-)

http://www.asi.org/adb/m/02/07/apollo-cost.html

In a more fair comparison, the Artemis people were going to start with
44,000 lbs in LEO (so 4.4 times as much as us). They would return between
200 lbs (95 Kg) and (227 Kg) of lunar material (we return ~4 to ~100 times
as much).

http://www.asi.org/adb/04/03/10/05/returned-mass.html

If you think of the investment cost as scaling with the lbs to LEO (a
reasonable first approximation) and the financial return value as the Kg
of Lunar material returned (not totally fair as the price goes down with a
bigger supply), then the tether method is 16 to 400 times better. Artemis
was sort of marginal as an investment, but this could be a reasonable
investment.

It is of course hard to estimate what people would pay for lunar regolith
once there was a real supply. If it was $1,000/gram and you had 2,000 Kg,
that would be $2 bil. Probably be hard to get that much, but it could
really be a good return on investment.

Additional missions would cost much less than the first, since you would
not have the development costs again. You could even design the vehicle
to be resupplied for a new mission (more xenon, new reentry capsule, etc).

This would be able to pick up samples from many parts of the Moon, any
part that passed under the orbit. If it was in a polar orbit it would even
be possible to get a sample from a dark crater at the North or South pole
to see if there was water ice.

Most of the regolith is very fine dust. You might get more money selling
lunar rocks. It might be possible to have a computer guided harpoon on
the end that could target small rocks.

Another interesting option is to use the tether to toss small reentry
capsules from the Moon in such a way that they fall back to Earth. One
nice thing about this is that you could start selling your product much
sooner. The other nice thing is that and if at some point their was a
catastrophic failure you would at least have what had been returned so
far. People bidding on what you had so far would not know how much more
would be coming. So concern that your vehicle might fail at any time
might keep the price of Lunar material high longer.

We have not seen this idea of using a rotating tether to pick up lunar
samples anyplace else and think it looks very promising. What do you
think?

-- Vince
  #2  
Old December 8th 03, 03:54 AM
Charles F. Radley
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Default Lunar Sample Return via Tether

Vincent,

Nice idea, but not original. Hoyt, Forward and Moravec have each proposed
using tethers for lunar landing and sample return some years ago.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually. You can
do it entirely with zero momentum exchange, you simply deposit payloads on
to the lunar surface whose mass equals that of the samples you remove.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html

Best regards,

Charles F. Radley AFAIAA

(Vincent Cate) wrote in message . com...
My father (Henry Cate) and I have come up with an initial tether project
that might be fun, affordable, and profitable. The idea is to use a
rotating tether to pickup some Lunar samples, bring them back to Earth,
and sell them.


[snip]


We have not seen this idea of using a rotating tether to pick up lunar
samples anyplace else and think it looks very promising. What do you
think?

-- Vince

  #3  
Old December 8th 03, 03:54 AM
Charles F. Radley
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

Vincent,

Nice idea, but not original. Hoyt, Forward and Moravec have each proposed
using tethers for lunar landing and sample return some years ago.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually. You can
do it entirely with zero momentum exchange, you simply deposit payloads on
to the lunar surface whose mass equals that of the samples you remove.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html

Best regards,

Charles F. Radley AFAIAA

(Vincent Cate) wrote in message . com...
My father (Henry Cate) and I have come up with an initial tether project
that might be fun, affordable, and profitable. The idea is to use a
rotating tether to pickup some Lunar samples, bring them back to Earth,
and sell them.


[snip]


We have not seen this idea of using a rotating tether to pick up lunar
samples anyplace else and think it looks very promising. What do you
think?

-- Vince

  #4  
Old December 8th 03, 05:50 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

In article ,
Vincent Cate wrote:
We have not seen this idea of using a rotating tether to pick up lunar
samples anyplace else...


I *think* I have seen rotating tethers for orbital samplers mentioned
before, but I'm unable to locate a specific reference.

...and think it looks very promising.


There are some obvious issues with precision navigation over an uneven
surface, but they don't seem insuperable.

It certainly does have potential.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #5  
Old December 8th 03, 05:50 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

In article ,
Vincent Cate wrote:
We have not seen this idea of using a rotating tether to pick up lunar
samples anyplace else...


I *think* I have seen rotating tethers for orbital samplers mentioned
before, but I'm unable to locate a specific reference.

...and think it looks very promising.


There are some obvious issues with precision navigation over an uneven
surface, but they don't seem insuperable.

It certainly does have potential.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #6  
Old December 8th 03, 11:32 AM
Ian Stirling
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

Charles F. Radley wrote:
Vincent,

Nice idea, but not original. Hoyt, Forward and Moravec have each proposed
using tethers for lunar landing and sample return some years ago.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually. You can
do it entirely with zero momentum exchange, you simply deposit payloads on
to the lunar surface whose mass equals that of the samples you remove.


Assuming a spherical moon.
For non-spherical, non-ideal gravity moons, things get more interesting.
  #7  
Old December 8th 03, 11:32 AM
Ian Stirling
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

Charles F. Radley wrote:
Vincent,

Nice idea, but not original. Hoyt, Forward and Moravec have each proposed
using tethers for lunar landing and sample return some years ago.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually. You can
do it entirely with zero momentum exchange, you simply deposit payloads on
to the lunar surface whose mass equals that of the samples you remove.


Assuming a spherical moon.
For non-spherical, non-ideal gravity moons, things get more interesting.
  #8  
Old December 8th 03, 11:37 AM
Vincent Cate
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

(Charles F. Radley) wrote in message
. com...
Nice idea, but not original. Hoyt, Forward and Moravec have each
proposed using tethers for lunar landing and sample return some
years ago.


I realize that they proposed tethers for the Moon; however, I have
not seen them point out that you could pick up samples without any
infrastructure in place on the Moon. The thing that might be
original is that a single probe, with no advance landing on the moon,
could use a tether to scoop up samples.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually.
You can do it entirely with zero momentum exchange, you simply
deposit payloads on to the lunar surface whose mass equals that of
the samples you remove.


If we use an ion drive of 10,000 seconds ISP, it is throwing xenon
out the back at about 98 km/sec. To pick up something from the
Moon we need to give it 1.6 km/sec of momentum. So with the momentum
from 1 Kg of xenon we can pick up 98 kps / 1.6 kps or about 61 Kg
of regolith. If you simply deposited equal mass on the lunar surface
you would only pick up 1 Kg for every 1 Kg you put down. So this way
is cheaper for a probe on a sample return type mission.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html


When I say "lunar sample return" I mean that there is nothing already
in place on the Moon. I have not seen anything in these or any
others papers I have read that indicates they were thinking of a
sample return type mission. Sure people have looked at Lunar
tethers. And I do think that two way lunar tether traffic would be
*really cool*. In particular once we have lots of tourists going to
the moon and coming back.

-- Vince
  #9  
Old December 8th 03, 11:37 AM
Vincent Cate
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

(Charles F. Radley) wrote in message
. com...
Nice idea, but not original. Hoyt, Forward and Moravec have each
proposed using tethers for lunar landing and sample return some
years ago.


I realize that they proposed tethers for the Moon; however, I have
not seen them point out that you could pick up samples without any
infrastructure in place on the Moon. The thing that might be
original is that a single probe, with no advance landing on the moon,
could use a tether to scoop up samples.

It can be done even more cheaply than you propose.

You do not even need any ion drive or propulsion at all actually.
You can do it entirely with zero momentum exchange, you simply
deposit payloads on to the lunar surface whose mass equals that of
the samples you remove.


If we use an ion drive of 10,000 seconds ISP, it is throwing xenon
out the back at about 98 km/sec. To pick up something from the
Moon we need to give it 1.6 km/sec of momentum. So with the momentum
from 1 Kg of xenon we can pick up 98 kps / 1.6 kps or about 61 Kg
of regolith. If you simply deposited equal mass on the lunar surface
you would only pick up 1 Kg for every 1 Kg you put down. So this way
is cheaper for a probe on a sample return type mission.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html


When I say "lunar sample return" I mean that there is nothing already
in place on the Moon. I have not seen anything in these or any
others papers I have read that indicates they were thinking of a
sample return type mission. Sure people have looked at Lunar
tethers. And I do think that two way lunar tether traffic would be
*really cool*. In particular once we have lots of tourists going to
the moon and coming back.

-- Vince
  #10  
Old December 8th 03, 03:03 PM
Charles F. Radley
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

(Vincent Cate) wrote in message . com...
(Charles F. Radley) wrote in message
. com...
Nice idea, but not original. Hoyt, Forward and Moravec have each
proposed using tethers for lunar landing and sample return some
years ago.


I realize that they proposed tethers for the Moon; however, I have
not seen them point out that you could pick up samples without any
infrastructure in place on the Moon. The thing that might be
original is that a single probe, with no advance landing on the moon,
could use a tether to scoop up samples.


The Hoyt/Forward proposals do not need infrastructure on the Moon.
A bit of infrastructure might be nice to collect the specimens ahead
of time and make them ready for pick-up, but that is not essential.


If we use an ion drive of 10,000 seconds ISP, it is throwing xenon
out the back at about 98 km/sec. To pick up something from the
Moon we need to give it 1.6 km/sec of momentum. So with the momentum
from 1 Kg of xenon we can pick up 98 kps / 1.6 kps or about 61 Kg
of regolith. If you simply deposited equal mass on the lunar surface
you would only pick up 1 Kg for every 1 Kg you put down. So this way
is cheaper for a probe on a sample return type mission.


OK. Whether that is better than zero momentum exchange depends on
whether you are interested in putting payloads on the lunar surface.
Since soft landing on the Moon using rockets is extremely expensive,
the tether method of depositing payloads is much cheaper. It would
open up new markets for lunar development.

Adding an ion drive has the advantage of lowering the amount of mass
which must be launched from Earth, but it loses the opportunity
benefit of soft-landing lots of payloads on to the Moon.

For the details, take a look at these web links:

http://www.tethers.com/MXTethers3.html

http://www.tethers.com/MXTethers.html


When I say "lunar sample return" I mean that there is nothing already
in place on the Moon. I have not seen anything in these or any
others papers I have read that indicates they were thinking of a
sample return type mission. Sure people have looked at Lunar


True, their paradigm is rather the inverse, soft landing high-value
payloads on to the Moon. They did not recognize collecting lunar
samples as a significant market.

You have taken the precise opposite viewpoint, going for the lunar
samples, and ignoring the oppportunity to soft-land payloads.

Perhaps reality will be somewhere in between.

tethers. And I do think that two way lunar tether traffic would be
*really cool*. In particular once we have lots of tourists going to
the moon and coming back.


In the short term we can soft land lots of infrastructure on to the
Moon basically for free (except for the cost of launch from Earth),
and build hotels ready for the tourists when they come.
 




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