Do the following:
2.) Construct a solar power satellite (SPS) out of local materials at a
construction site located a few kilometers away from the NEO.
3.) Fly the completed SPS back to Earth geosynchronous orbit using
electrical propulsion (e.g., ion drive a la Deep Space 1, or MHD, or M2P2,
etc.).
4.) Start operation of the SPS in GEO, transmit power to Earth, make
money.
No complex mass driver/catcher systems is required.
Material transport between the NEO and construction site is trivial.
Constant sunlight is available at the construction site.
There is plenty of available electrical power with which to transport the
finished product back to GEO. There is no need for low-efficiency chemical
rocket engines.
Ron Menich
1.) Transport workers and tools to a suitable NEO.
2.) Construct a solar power satellite (SPS) out of local materials at a
construction site located a few kilometers away from the NEO.
3.) Fly the completed SPS back to Earth geosynchronous orbit using
electrical propulsion (e.g., ion drive a la Deep Space 1, or MHD, or M2P2,
etc.). This is a pretty good proposal, and you make some good points, but I would still tend to favor retrieving resources from the NEO, transporting them back to High Earth Orbit, and building the SPS there. There's no way to obtain asteroidal resources without sending human beings far from Earth, and that can't be helped. But I think there would be advantages to concentrating most of ourother activities, such as ore refinement, parts fabrication, and assembly as close to Earth as possible. For one thing, if telepresence technologies advance sufficiently to come into play, they can be used from Earth at the distance of HEO (or even the moon), but not at the distance of a NEO. And being relatively close to Earth is good in an emergency situation. Two of your advantages, constant sunlight and use of high efficiency drives, would also be applicable if most industrial operations take place in HEO. I'll always have asoft spot for mass driver tugs, but it's conceivable that some of the other high-efficiency/low-thrust drives you mention could also be used to fly resources from a NEO back to HEO. Some thinkers at SSI have recently said it might be better to send your ore refinery/manufacturing center to a NEO and to build a space habitat there rather than in HEO. But here too, I'd tend to favor assembly in HEO. I think initial stocking of the ecosystem would be easier if Earth were nearby, and unanticipated, near-emergency requirements for this kind of decomposition bacteria or that kind of plant might be better met if Earth was 2-3 days away rather than 2-3 months. But I will say this for the "build your settlement next to a NEO" approach. Just about the only undeniable advantage of settlements on the surface of Mars vs. O'Neill settlements is that the resources you need are literally underfoot. Building habitats in HEO will require importation of all raw materials from elsewhere in space. But I think an O'Neill habitat being built next door to a NEO would have the same easy access to resources as a Martian colony, and thus feel that the oneremaining advantageto building settlements on Mars would collapse in that scenario. Long term, I expect far more habitats to be built next door to an asteroid than in HEO. But I still expect the first generation habitats to be built in HEO. I also expect SPS intended for Earth surface service to be manufactured and assembled in HEO, regardless of whether we tap the moon for resources, a NEO, or both at the same time.
Mike Combs
> Do the following:
>
> 1.) Transport workers and tools to a suitable NEO.
construction/machining. That's a lot of mass to have to send. It
would be more ecconomical to send just the mining/refining tools,
leaving the construction/machining tools in Earth Orbit. Then return
with the refined materials (which you would be sending anyway, just
in finished form). Also, SPS's are relatively delicate compaired to
bulk refined materials. How many micrometeorites, dust particles,
hell, even large debris will the traveling SPS encounter durring it's
2-12 month journey?
> 2.) Construct a solar power satellite (SPS) out of local materials
at a
> construction site located a few kilometers away from the NEO.
> 3.) Fly the completed SPS back to Earth geosynchronous orbit using
> electrical propulsion (e.g., ion drive a la Deep Space 1, or MHD,
or M2P2,
> etc.).
> 4.) Start operation of the SPS in GEO, transmit power to Earth,
make
> money.
>
Something just occured to me. Has anyone ran the numbers for
transmitting power from an SPS at a NEO? You would have to build a
rectenna in Earth Orbit but it would probably be of much less mass
than a comparable SPS. If the loss isn't too great, why move the SPS
at all? Just build it at the NEO and start beaming. Heck, you can
continually upgrade and expand the SPS untill you run out of asteroid.
Or am I just loopy?
king_rodent (putting the eek in geek)
"I don't know where the 51st state will be,
but the 52nd will be in orbit"
Depends on whether the NEO is closer or further from the sun than the earth
is.
distance, further away means less energy/m^2.
Also, rectennas would have to absorb and retransmit, so a reflector that
reconcentrates the beam would be preferable.
Additionally, the distance from the NEO to HEO is likely to be further than
say, the moon to HEO, so the size of the rectenna/reflector would have to be
much larger and hence more expensive...
Tom M.
TomM@...
Beaming energy directly from the NEO to Earth orbit is, I think, infeasible because of the huge, huge required size of the antenna/rectenna pair. The distance from GEO to Earth is 40,000km, and researchers have worked out the required sizes of the antenna/rectenna pair for that scenario, and they are already large at that distance. The distance from a NEO to GEO would be three orders of magnitude larger, and this fact would pump up the required antenna/rectenna sizes to ridiculous proportions.
Ron Menich
"Tom Musgrove"
07/05/2001 04:52 PM
Depends on whether the NEO is closer or further from the sun than the earth
is.
Since the radiation intensity decreases with the inverse square of the
distance, further away means less energy/m^2.
Also, rectennas would have to absorb and retransmit, so a reflector that
reconcentrates the beam would be preferable.
Additionally, the distance from the NEO to HEO is likely to be further than
say, the moon to HEO, so the size of the rectenna/reflector would have to be
much larger and hence more expensive...
Tom M.
TomM@...
" There's the gotcha. Sending all the tools, both mining/refining AND
construction/machining. That's a lot of mass to have to send. It
would be more ecconomical to send just the mining/refining tools,
leaving the construction/machining tools in Earth Orbit. Then return
with the refined materials (which you would be sending anyway, just
in finished form)."
" Also, SPS's are relatively delicate compaired to
bulk refined materials. How many micrometeorites, dust particles,
hell, even large debris will the traveling SPS encounter durring it's
2-12 month journey?"
Interplanetary space is very empty in comparison with GEO (and especially in comparison with LEO, which is relatively cluttered with flecks of paint and such). There is an interplanetary probe with which the DSN communicated this past year that was launched in 1965 and is still operating. Interplanetary space is a fairly benign debris environment.
I'd be more concerned with control of debris during construction, and this is a concern no matter where the SPS is constructed (at the NEO, in HEO, etc.).
>
> In your scenario, the construction/machining would presumably be done
> in HEO (GEO or above) and tools would be shipped up from LEO. But
> LEO to GEO delta-V is already more than Earth escape delta-V. So I
> don't perceive a great disadvantage to shipping the
> construction/machining tools directly to the NEO instead.
>
L-5 libration orbits.
It takes a lot less energy to get there than to GEO if lunar flyby is
used.
The finished product (SPS) can be shipped from L-4/5 to GEO fairly
cheaply.
Consider the delta-V required to go from LEO to L4 or L5 with Lunar assist.
Is this more or less than the delta-V required to escape Earth completely
from LEO?
Charles
07/06/01
10:28 AM
Please
respond to
ssi_list
>
> In your scenario, the construction/machining would presumably be done
> in HEO (GEO or above) and tools would be shipped up from LEO. But
> LEO to GEO delta-V is already more than Earth escape delta-V. So I
> don't perceive a great disadvantage to shipping the
> construction/machining tools directly to the NEO instead.
>
The best place to do the manufacturing would be the Earth-Moon L-4 or
L-5 libration orbits.
It takes a lot less energy to get there than to GEO if lunar flyby is
used.
The finished product (SPS) can be shipped from L-4/5 to GEO fairly
cheaply.
<<
Consider the delta-V required to go from LEO to L4 or L5 with Lunar assist.
Is this more or less than the delta-V required to escape Earth completely
from LEO?
It is a few percent more than the energy needed to get from LEO to elliptical trans-Lunar Transfer Orbit.
LTO in turn is a few percent more delta-v than eliiptical geostationary transfer orbit.
These are all a lot less than LEO to GEO. It is the large final circularization burn delta-vee at GTO apogee which is the killer for LEO to GEO.
I have the numbers at home in a spreadsheet, I can post them over the weekend if y'all are interested.
Cheers,
CR.
>
> Consider the delta-V required to go from LEO to L4 or L5 with Lunar assist.
> Is this more or less than the delta-V required to escape Earth completely
> from LEO?
>
more or less. It is about the same, maybe slightly more, maybe
slightly less.
The difference is small enough that other factors will be a lot more
important.
In particular, the main problem with a NEO is the lack of launch
windows, they can be several years apart.
On the other hand, we can shuttle back and forth between LEO, GEO and
Lunar L-4/5 any time we want to.
So for ease of logistics and planning (which includes financial
planning) the modus operandi should be to send as little as possible to
the NEO, because the dominant problem will be getting ROI as quickly as
possible to keep the investors happy. Rather than save a few percent
in propellant, they would much rather get their ROI a couple of years
sooner.
Hence the following scenario would be more attractive than sending
everything to a NEO in one shot (that would require a huge up front
investment and tie the money up for a long time):
1) Finance, develop and build a NEO propulsion system.
Select one or more target NEO's, and send the propulsion system(s)
there.
Grab all or part of each NEO and send it to lunar L-4/5.
In parallel to 1) :
2) Finance, develop and build manufacturing facility at Lunar L-4/5.
This can proceed asynchronous to the NEO recovery mission allowing for
improved flexibility in planning and fundraising. This project could
be started after the propulsion unit is on its way to NEO, and thus
spread out the time over which money must be invested. This will be a
lot easier than trying to raise all the money up front.
Also, the L-4/5 facility can be fed by multiple NEO objects, so we are
not locking ourselves into having our manufacturing facility being tied
up on a single NEO which could take several years to return to Earth.
====
We can send multiple propulsion units to multiple NEO's and set up a
steady stream of payloads to arrive at L-4/5. All feeding a single
manufacturing facility.
We can also use other sources of feedstock. A manufacturing facility at
L-4/5 can use spent rocket stages in Earth orbit as rich feedstock. A
space tug in LEO can use precession to drift towards different orbital
planes (same inclination, different ascending node) over periods of
time, and then rendezvous and grab each stage and take it to L-4/5 via
luanr flyby. Then a subsequent lunar flyby at apogee can be used to
change the inclination. Most of the propellant can be oxygen extracted
from NEO or lunar material.
"In particular, the main problem with a NEO is the lack of launch
windows, they can be several years apart.
Lunar L-4/5 any time we want to.
"
There may be NEOs located at the Sun-Earth L4 and L5 libration points
(so-called "Earth Trojans"). Currently, there are 5 known Mars Trojans
and 1007 known Jupiter Trojans (c.f.,
http://cfa-www.harvard.edu/iau/lists/Trojans.html ). If Earth Trojans
were to exist, then there would exist continuous launch windows to them
from Earth with constant delta-V.
I've heard that it is very tough to detect Earth Trojans from the surface
of the Earth because of the viewing angles. (If I'm envisioning my
geometry correctly, the L4/L5 points of the Sun-Earth system are not
visible from Earth at night. Recall that L4/L5 are each 60 degrees away
from the Earth in the same orbit. ) That is, the lack of any known Earth
Trojans at this time may not so much be an indication that no such object
exists as it is an indication that such an object, even if it were it to
exist, would be much more difficult to detect from Earth than NEOs in other
orbits.
Even sans Earth Trojans, we need to examine the term "launch window"
carefully, I think, for the case of NEOs whose orbits are very similar to
Earth's. Launch windows are periods of time during which launch should
take place in order to achieve a certain low delta-V value, given an
assumed mission profile. Launches at other times are not impossible, but
their delta-V values will be higher. It is conceivable to design a
spacecraft that would allow a range of possible delta-V values, with more
cargo or less cargo delivered depending on whether the required delta-V
were smaller or larger. All of the delta-V required for HEO->NEO->HEO
transport could be provided with high specific impulse engines. This is
an important difference vis a vis the Moon, for which descent/ascent
to/from the surface must be accomplished by chemical propulsion with low
specific impulse (unless you've got your complex mass driver infrastructure
or tether infrastructure already built).
Thus, the required delta-V for a NEO mission could be much larger than for
a Moon mission but yet have more cargo capacity because of the high
efficiency engines that are usable for NEO missions but not for Moon
missions.
Ron Menich
>
> "In particular, the main problem with a NEO is the lack of launch
> windows, they can be several years apart.
>
> On the other hand, we can shuttle back and forth between LEO, GEO and
> Lunar L-4/5 any time we want to.
> "
>
> There may be NEOs located at the Sun-Earth L4 and L5 libration points
> (so-called "Earth Trojans"). Currently, there are 5 known Mars Trojans
> and 1007 known Jupiter Trojans (c.f.,
> http://cfa-www.harvard.edu/iau/lists/Trojans.html ). If Earth Trojans
> were to exist, then there would exist continuous launch windows to them
> from Earth with constant delta-V.
>
>
> Even sans Earth Trojans, we need to examine the term "launch window"
> carefully, I think, for the case of NEOs whose orbits are very similar to
> Earth's. Launch windows are periods of time during which launch should
> take place in order to achieve a certain low delta-V value, given an
> assumed mission profile.
This means the economic Hohmann transfer opportunity.
> Launches at other times are not impossible, but
> their delta-V values will be higher. It is conceivable to design a
> spacecraft that would allow a range of possible delta-V values, with more
> cargo or less cargo delivered depending on whether the required delta-V
> were smaller or larger. All of the delta-V required for HEO->NEO->HEO
> transport could be provided with high specific impulse engines. This is
Anything is possible, but a vehicle travelling on non-Hohmann trajectory
will need a lot more delta-vee,
and even a high SI system will add signicantly to the cost of vehicle.
On the other hand it can have the benefit of reducing the trip time,
which will please the investors who want their ROI as soon as
possible. This benefit can be quantified using time value cost of
money equations.
The total cost of debt service grows exponentially with time.
> an important difference vis a vis the Moon, for which descent/ascent
> to/from the surface must be accomplished by chemical propulsion with low
> specific impulse (unless you've got your complex mass driver infrastructure
> or tether infrastructure already built).
>
We were not discussing landing on the Moon, that is a different matter.
We were discussing whether it is better to put the manufacturing
facility at L-4/5 and
bring the NEO to L-4/5, or whether we should send the manufacturing cell
to the NEO and send the finished product back to L-4/5.
> Thus, the required delta-V for a NEO mission could be much larger than for
> a Moon mission but yet have more cargo capacity because of the high
> efficiency engines that are usable for NEO missions but not for Moon
> missions.
>
Yes it is expensive to soft land on the Moon, but that is not the issue
I have been dicussing in this thread.
O'k to most of your points, Charles. Apologies for mistaking the thrust of
your previous messages; I should have read them more carefully.
"Anything is possible, but a vehicle travelling on non-Hohmann trajectory
will need a lot more delta-vee,
and even a high SI system will add signicantly to the cost of vehicle.
"
My original suggestion --- build the SPS at the NEO and fly it back to GEO
using electrical propulsion --- would involve a continuous-thrusting
trajectory rather than a Hohman trajectory. Electrical propulsion
essentially necessitates non-Hohman trajectories because of low thrust.
But achievable delta-V is directly proportional to specific impulse, and
electrical propulsion systems can offer specific impulses over 10 times
what the best hydrogen/oxygen chemical engine can provide.
As I understand it, there is some latitude during design of electrical
propulsion systems to **choose** the specific impulse. Choosing higher
specific impulse results in larger mass for solar arrays and power
conditioning equipment, so it is often not optimal to choose the highest
specific impulse attainable. Transporting a completed SPS back to GEO
presents an interesting design problem: given that I have a x hundred
megawatts of available power and that I must transport the y thousand ton
SPS back to GEO in z days, what specific impulse should I choose?
Ron Menich
Charles
07/10/01
10:59 PM
Please
respond to
ssi_list
>
> "In particular, the main problem with a NEO is the lack of launch
> windows, they can be several years apart.
>
> On the other hand, we can shuttle back and forth between LEO, GEO and
> Lunar L-4/5 any time we want to.
> "
>
> There may be NEOs located at the Sun-Earth L4 and L5 libration points
> (so-called "Earth Trojans"). Currently, there are 5 known Mars Trojans
> and 1007 known Jupiter Trojans (c.f.,
> http://cfa-www.harvard.edu/iau/lists/Trojans.html ). If Earth Trojans
> were to exist, then there would exist continuous launch windows to them
> from Earth with constant delta-V.
>
Right.
>
> Even sans Earth Trojans, we need to examine the term "launch window"
> carefully, I think, for the case of NEOs whose orbits are very similar to
> Earth's. Launch windows are periods of time during which launch should
> take place in order to achieve a certain low delta-V value, given an
> assumed mission profile.
This means the economic Hohmann transfer opportunity.
> Launches at other times are not impossible, but
> their delta-V values will be higher. It is conceivable to design a
> spacecraft that would allow a range of possible delta-V values, with more
> cargo or less cargo delivered depending on whether the required delta-V
> were smaller or larger. All of the delta-V required for HEO->NEO->HEO
> transport could be provided with high specific impulse engines. This is
Anything is possible, but a vehicle travelling on non-Hohmann trajectory
will need a lot more delta-vee,
and even a high SI system will add signicantly to the cost of vehicle.
On the other hand it can have the benefit of reducing the trip time,
which will please the investors who want their ROI as soon as
possible. This benefit can be quantified using time value cost of
money equations.
The total cost of debt service grows exponentially with time.
> an important difference vis a vis the Moon, for which descent/ascent
> to/from the surface must be accomplished by chemical propulsion with low
> specific impulse (unless you've got your complex mass driver
infrastructure
> or tether infrastructure already built).
>
We were not discussing landing on the Moon, that is a different matter.
We were discussing whether it is better to put the manufacturing
facility at L-4/5 and
bring the NEO to L-4/5, or whether we should send the manufacturing cell
to the NEO and send the finished product back to L-4/5.
> Thus, the required delta-V for a NEO mission could be much larger than
for
> a Moon mission but yet have more cargo capacity because of the high
> efficiency engines that are usable for NEO missions but not for Moon
> missions.
>
Yes it is expensive to soft land on the Moon, but that is not the issue
I have been dicussing in this thread.
We were discussing whether it is better to put the manufacturing
facility at L-4/5 and
bring the NEO to L-4/5, or whether we should send the manufacturing cell
to the NEO and send the finished product back to L-4/5. My opinion on this is that if there were any portion of the raw material which went to waste, then we might say that sending mining/manufacturing facilities to the NEO and sending only finished products back to cislunar spacemight involve transporting less mass. But I don't think this is the case. Even the slag left over from the refining operation is useful for shielding, or possibly as reaction mass if mass driver tugs are being used. Given this, since the total amount of material transported back from the asteroid might logically be the same in either case, I say concentrating most industrial operations closer to Earth would be where the advantage lay.
Mike Combs
>>>>>>>>>>>>>>>>>>>>
Date: Wed, 11 Jul 2001 08:39:33 -0500
concentrating most
industrial operations closer to Earth would be where the advantage
lay.
>>>>>>>>>>>>>>>>>>>>
If the manufacturing cell fails because of some syustem failure,
it will be a lot easier to fly up spare parts to repair it and get it
going again.
The alternative would be to fly a huge stock of spare partds and repair
tools to the NEO base.
Thinking some more....there might be an even better location than
Earth-Moon L-4/5.
The Earth-Sun L-1 and L-2 points, about 1.5 million kilometres from
Earth, towards the Sun and away from the Sun respectively. The SOHO
spacecraft was placed at the Earth-Sun L-1 in 1995 to study the Sun, and
just a week or two back the MAPS spacecraft was sent to the Earth-Sun
L-2 point to study the cosmic microwave background.
These points are quite close to Earth in energy terms, and somewhat
easier to reach for a NEO than the Eartrh-Moon libration points.
Also, in the Earth-Moon vicinity there might be public fear about the
danger of the asteroid colliding with the Earth. At the Earth-Sun
libraiton points the separation distance is greater which should clam
public fears.
A Question: Would tethers work for keeping the solar cells, reflectors,
etc. oriented at the Earth-Sun L-1 point? If so, that would seem to
simplify the requirements for an O'Neill type colony there. Sincerely, Jay
S. Huebner at jhuebn@...
"Some thinkers at SSI have recently said it might be better to send your
ore refinery/manufacturing center to a NEO and to build a space habitat
there rather than in HEO. "
Ron Menich
"Combs, Mike"
ssi_list@... ssi_list@...
07/05/01
04:50 PM
Please
respond to
ssi_list
1.) Transport workers and tools to a suitable NEO.
2.) Construct a solar power satellite (SPS) out of local materials at a
construction site located a few kilometers away from the NEO.
3.) Fly the completed SPS back to Earth geosynchronous orbit using
electrical propulsion (e.g., ion drive a la Deep Space 1, or MHD, or M2P2,
etc.).
This is a pretty good proposal, and you make some good points, but I would
still tend to favor retrieving resources from the NEO, transporting them
back to High Earth Orbit, and building the SPS there. There's no way to
obtain asteroidal resources without sending human beings far from Earth,
and that can't be helped. But I think there would be advantages to
concentrating most of our other activities, such as ore refinement, parts
fabrication, and assembly as close to Earth as possible. For one thing, if
telepresence technologies advance sufficiently to come into play, they can
be used from Earth at the distance of HEO (or even the moon), but not at
the distance of a NEO. And being relatively close to Earth is good in an
emergency situation.
Two of your advantages, constant sunlight and use of high efficiency
drives, would also be applicable if most industrial operations take place
in HEO. I'll always have a soft spot for mass driver tugs, but it's
conceivable that some of the other high-efficiency/low-thrust drives you
mention could also be used to fly resources from a NEO back to HEO.
Some thinkers at SSI have recently said it might be better to send your ore
refinery/manufacturing center to a NEO and to build a space habitat there
rather than in HEO. But here too, I'd tend to favor assembly in HEO. I
think initial stocking of the ecosystem would be easier if Earth were
nearby, and unanticipated, near-emergency requirements for this kind of
decomposition bacteria or that kind of plant might be better met if Earth
was 2-3 days away rather than 2-3 months.
But I will say this for the "build your settlement next to a NEO" approach.
Just about the only undeniable advantage of settlements on the surface of
Mars vs. O'Neill settlements is that the resources you need are literally
underfoot. Building habitats in HEO will require importation of all raw
materials from elsewhere in space. But I think an O'Neill habitat being
built next door to a NEO would have the same easy access to resources as a
Martian colony, and thus feel that the one remaining advantage to building
settlements on Mars would collapse in that scenario.
Long term, I expect far more habitats to be built next door to an asteroid
than in HEO. But I still expect the first generation habitats to be built
in HEO. I also expect SPS intended for Earth surface service to be
manufactured and assembled in HEO, regardless of whether we tap the moon
for resources, a NEO, or both at the same time.
Regards,
Mike Combs
"Some thinkers at SSI have recently said it might be better to send your
ore refinery/manufacturing center to a NEO and to build a space habitat
there rather than in HEO. "
Regards,
Mike Combs
>
> A Question: Would tethers work for keeping the solar cells, reflectors,
> etc. oriented at the Earth-Sun L-1 point? If so, that would seem to
> simplify the requirements for an O'Neill type colony there. Sincerely, Jay
It might actually complicate things.
The L-1/2 points are not stable, so stationkeeping is reqired. The
two ends of the tether will require independent staitonkeeping. This
will be difficult to coordinate.
Might be easier to have a single platform with active attitude control
system.
What about a tether that straddles the L1 point, with one end in the
Lunar gravity well, the other in Earth's. Weights on each end could be
raised and lowered to help stabilize it in one dimension. Would that be
sufficient or just make it worse?
if there is any half-way decent open-source software out there to do
basic stuff like this with a reasonable degree of accuracy. I doubt
there's any such software that would include long tethers, but something
would be nice.
Andrew
A Question: Would tethers work for keeping the solar cells, reflectors,
etc. oriented at the Earth-Sun L-1 point? If so, that would seem to
simplify the requirements for an O'Neill type colony there. Sincerely,
Jay
This is not obvious.
It might actually complicate things.
The L-1/2 points are not stable, so stationkeeping is reqired. The
two ends of the tether will require independent staitonkeeping. This
will be difficult to coordinate.
Might be easier to have a single platform with active attitude control
system.
What about a tether that straddles the L1 point, with one end in the
Lunar gravity well, the other in Earth's. Weights on each end could be
raised and lowered to help stabilize it in one dimension. Would that be
sufficient or just make it worse?
if there is any half-way decent open-source software out there to do
basic stuff like this with a reasonable degree of accuracy. I doubt
there's any such software that would include long tethers, but something
would be nice.
Andrew
A Question: Would tethers work for keeping the solar cells, reflectors,
etc. oriented at the Earth-Sun L-1 point? If so, that would seem to
simplify the requirements for an O'Neill type colony there. Sincerely,
Jay
This is not obvious.
It might actually complicate things.
The L-1/2 points are not stable, so stationkeeping is reqired. The
two ends of the tether will require independent staitonkeeping. This
will be difficult to coordinate.
Might be easier to have a single platform with active attitude control
system.
>
> What about a tether that straddles the L1 point, with one end in the
> Lunar gravity well, the other in Earth's. Weights on each end could be
> raised and lowered to help stabilize it in one dimension. Would that be
> sufficient or just make it worse?
>
The L-1 point is a saddle point, some complex manouvering is required to
maintain station.
> All the questions on this list about orbital mechanics makes me wonder
> if there is any half-way decent open-source software out there to do
> basic stuff like this with a reasonable degree of accuracy. I doubt
> there's any such software that would include long tethers, but something
> would be nice.
>
Not to my knowledge. Some commercial products exist and they are very
expensive.
Haved you looked at www.tethers.com ?
What about a tether that straddles the L1 point, with one end in the
Lunar gravity well, the other in Earth's. Weights on each end could be
raised and lowered to help stabilize it in one dimension. Would that be
sufficient or just make it worse? Unfortunately, I'm pretty sure that wouldn't work. Consider that the raising and lowering of the weights would themselves be momentum transfers, and oppositeto the ones you would want, I'm thinking. I'm pretty sure that action-reaction (Newtonian) thrusters of some kind would be needed. But my perception of this situation is that the finer your ability to detect deviations from position, and the finer your ability to thrust, the smaller your reaction mass requirements become. I know that by bouncing lasers off of Apollo reflectors on the moon, scientists can measure the moon's distance to an accuracy of a few inches. So surely keeping on top of that instability would be no major task.
Mike Combs
Lunar gravity well, the other in Earth's. Weights on each end could be
raised and lowered to help stabilize it in one dimension. Would that be
sufficient or just make it worse? It should work anywhere in earth orbit Andy, but it seems like overkill. You should be able to maintain orbit a lot easier with rockets or maybe a mass driver.