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Lunar Sample Return via Tether



 
 
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  #11  
Old December 8th 03, 03:03 PM
Charles F. Radley
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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.
  #12  
Old December 8th 03, 03:07 PM
Charles F. Radley
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Default Lunar Sample Return via Tether

Ian Stirling wrote in message ...
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.


Maybe.

A lot of control can be gained by reeling the tethers in and out. A
small propulsion system might help, but it is too early to say whether
it is an essential component.

Some analysis is needed.
  #13  
Old December 8th 03, 03:07 PM
Charles F. Radley
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Default Lunar Sample Return via Tether

Ian Stirling wrote in message ...
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.


Maybe.

A lot of control can be gained by reeling the tethers in and out. A
small propulsion system might help, but it is too early to say whether
it is an essential component.

Some analysis is needed.
  #14  
Old December 8th 03, 04:19 PM
Henry Spencer
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Default Lunar Sample Return via Tether

In article ,
Vincent Cate wrote:
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.


...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.


Yes and no and maybe. It uses less fuel, but that does not necessarily
equate to "cheaper". The issue is not fuel cost -- xenon is one of the
few fuels whose cost actually *is* comparable to LEO launch costs, but
even so, that's a relatively minor issue here -- but hardware costs and
complexity and reliability.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #15  
Old December 8th 03, 04:19 PM
Henry Spencer
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Posts: n/a
Default Lunar Sample Return via Tether

In article ,
Vincent Cate wrote:
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.


...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.


Yes and no and maybe. It uses less fuel, but that does not necessarily
equate to "cheaper". The issue is not fuel cost -- xenon is one of the
few fuels whose cost actually *is* comparable to LEO launch costs, but
even so, that's a relatively minor issue here -- but hardware costs and
complexity and reliability.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #18  
Old December 8th 03, 06:19 PM
Vincent Cate
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Default Lunar Sample Return via Tether

(Henry Spencer) wrote in message ...
I *think* I have seen rotating tethers for orbital samplers mentioned
before, but I'm unable to locate a specific reference.


From:
http://www.uah.edu/library/archives/...sinessBio.html
... "Tether-Assisted Planetoid Sampler" that would use a sampling
penetrator on the end of rotating tether to obtain a sample from the
surface of an airless planetoid (from comets and asteroids to Luna
and Mercury) during a flyby trajectory and return it to the Earth, ...


Our idea of orbiting for months and winching in sample after sample
using a high ISP thruster is a little bit different from this single
flyby idea. Though going from that to ours is not much of a leap. :-)

Anyway, if you or anyone finds any references I am interested.

-- Vince
  #19  
Old December 8th 03, 06:19 PM
Vincent Cate
external usenet poster
 
Posts: n/a
Default Lunar Sample Return via Tether

(Henry Spencer) wrote in message ...
I *think* I have seen rotating tethers for orbital samplers mentioned
before, but I'm unable to locate a specific reference.


From:
http://www.uah.edu/library/archives/...sinessBio.html
... "Tether-Assisted Planetoid Sampler" that would use a sampling
penetrator on the end of rotating tether to obtain a sample from the
surface of an airless planetoid (from comets and asteroids to Luna
and Mercury) during a flyby trajectory and return it to the Earth, ...


Our idea of orbiting for months and winching in sample after sample
using a high ISP thruster is a little bit different from this single
flyby idea. Though going from that to ours is not much of a leap. :-)

Anyway, if you or anyone finds any references I am interested.

-- Vince
  #20  
Old December 8th 03, 09:35 PM
Andrew Nowicki
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Default Lunar Sample Return via Tether

I believe there is more money to make on hands-on space experience than
on the Moon rocks. It would be fun for the overweight Internet generation
to control a low Earth orbit satellite and take pictures of a home town.
It would be even more fun to do some real work. For example, the lunavator
can deposit toy size, rock hunting excavators on the visible half of the
Moon so that relatively cheap terrestrial microwave dishes can communicate
directly with the excavators. The Internet users would control the excavators
with a mouse. They would hunt for rocks and scratch graffiti on the Moon
dust. A few years ago a businessman considered launching a remotely
controlled lunar buggy and renting it for "virtual" joy riders. Whatever
you do, keep in mind that novelty of such space hardware will wear off
quickly unless the hardware can do new things that have not been done before.

I would start with finding a massive piece of junk in low Earth orbit and
attaching a 100 kg Zylon bolo to the junk. The bolo has internal wires which
can be used as electrodynamic tethers and power supply for a remote
manipulator riding on the bolo. The wires can make lots of electric power
at night, and they can control the orbit of the junk/bolo satellite. Add
a 200 kg sounding rocket, a few Hall thrusters, and you can use the bolo
to launch your lunavator in 20 kg pieces assembled in space with another
remote manipulator. When the lunavator is assembled, you have your own,
dirt cheap, lunavator bolo relay, which is Earth-to-orbit, Earth-to-Moon,
and Moon-to-Earth space transportation system.
 




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