This is the most important CATS post ever!

The technology described in this post has not been tested, but
it looks trivial when compared to rocket launchers, and it
may reduce the cost of space access to a few dollars per kilogram!

The technology is based on GPS, a reusable sounding rocket,
cheap terrestrial bolo, cheap lunar rotovator, cheap cargo
sacks, and a small Zylon sling. The bolo and the rotovator
are useful terms defined by Robert Forward. They are described
he http://www.islandone.org/LEOBiblio/SPBI122.HTM
(Robert P. Hoyt calls lunar rotovator "lunavator.")
The rotovator hurls the sacks filled with regolith (Moon dust)
towards the Earth. It is mounted on a rotating arm which is
attached to a large, rotating, toroidal greenhouse. The arm
rotates independently of the greenhouse, so it can easily
change the angular velocity of the rotovator. The maximum
length of the rotovator is about 200 km. When a winch reels
its cargo in, the cargo moves faster to conserve its angular
momentum. This fact makes it possible to increase the orbital
energy of the rotovator and the greenhouse without the need
for any external thrust. It is as simple as capturing
the cargo, reeling it in, and releasing it. The orbital
velocity of the rotovator is only 1.6 km/s, much less than
the Moon's escape velocity (2.4 km/s). When the cargo is
released from the rotovator, its velocity relative to the
Moon is 3.2 km/s. It is gradually slowed down by the lunar
gravity to 0.8 km/s (3.2 km/s - 2.4 km/s = 0.8 km/s).
Gravitational pull of the Earth accelerates the cargo by
11.2 km/s, which is the Earth's escape velocity. When the
cargo is captured by the terrestrial bolo, its velocity
relative to the bolo is 4.3 km/s. (The cargo gains 3.5 km/s,
which is the difference between the Earth's escape velocity,
and the orbital velocity of the bolo, which is 7.7 km/s).
The bolo is larger than the rotovator, but it has the same
design, and is mounted on a rotating arm, which is attached
to a large, rotating, toroidal greenhouse. The bolo
reverses velocity of the cargo and drops it on the Earth.
This maneuver increases the orbital energy of the bolo and
the orbital energy of the greenhouse which is attached to the
bolo. When the cargo is released from the bolo, its velocity
relative to the Earth is only 3.4 km/s. Before the cargo
enters the atmosphere, it is captured at the altitude of
100 km by a sling attached to a payload which was launched
from the Earth a few minutes earlier. The payload has the
same mass as the cargo. Its velocity relative to the Earth
is only 2.5 km/s. The sling is made of Zylon, makes up 20%
of the payload's mass, and is strong enough to reverse
relative velocity of the cargo and the payload. When the
cargo and the payload separate, cargo velocity relative
to the Earth is reduced to 1.6 km/s, and payload velocity
relative to the Earth is increased to 4.3 km/s. Finally, the
payload is captured by the bolo. If the payload is going to
be used in the greenhouse orbiting the Earth, the bolo's
winch reels it in. If it is going to be used in the
greenhouse orbiting the Moon, The bolo reverses payload's
velocity and hurls it toward the rotovator, which captures
it.

The rotovator and the bolo do not have to be made of
unobtanium, buckytubes, or even Zylon. Carbon fibers and
S-glass fibers are strong enough, and they are immune to the
radiation and temperature extremes of the outer space. Perhaps
the most practical material for the rotovator and the bolo is
a composite made of carbon fibers and S-glass fibers fused
together under high pressure and high temperature. More info
about slings: http://www.islandone.org/LEOBiblio/SPBI1SL.HTM

It is easy to design a reusable sounding rocket which lifts
the payload to the altitude of 100 km and accelerates it to the
velocity of 2.5 km/s. (When the payload separates from the
rocket, its total energy is equivalent to the kinetic energy
of only 3 km/s.)

Modern GPS technology guarantees high precision of the maneuvers:
http://gipsy.jpl.nasa.gov/igdg/syste....html#accuracy

I left out many important details:

If there is only one bolo, payload trajectory is tilted
upwards, and cargo trajectory is tilted downwards after
separation. Cargo velocity relative to the Earth is reduced
to more than 1.6 km/s, and payload velocity relative to the
Earth is increased to less than 4.3 km/s.

If there are several bolos, the sounding rocket does not
accelerate the payload, but merely lifts it to the altitude
of 100 km. The sling captures and releases several small
cargoes, so its mass is smaller. My favorite propellant
for the sounding rocket is hydrogen peroxide monopropellant
because it is safe and clean.

I have just improved design of the bolo and the sling.
Here is complete, revised text:

This system of Earth-to-orbit transportation is called
"lunavator bolo exchange." It is trivial when compared
to rocket launchers, and it may reduce the cost of space
access to a few dollars per kilogram! The system is based
on GPS, a reusable sounding rocket, terrestrial bolo,
lunar rotovator, cargo sacks, and a small Zylon sling.

The lunar rotovator is called lunavator. It hurls sacks
filled with regolith (Moon dust) toward the Earth. The
lunavator is mounted on a rotating arm which is attached to
a large, rotating, toroidal greenhouse. The arm rotates
independently of the greenhouse, so it can easily change
the angular velocity of the lunavator. The maximum length
of the lunavator is about 200 km. When a winch reels its
cargo in, the cargo moves faster to conserve its angular
momentum. This fact makes it possible to increase the
orbital energy of the lunavator and the greenhouse without
the need for any external thrust. It is as simple as
picking the cargo from the Moon, reeling it in, and tossing
it backward. The orbital velocity of the lunavator is only
1.6 km/s, much less than the Moon's escape velocity (2.4
km/s). When the cargo is released from the lunavator, its
velocity relative to the Moon is 3.2 km/s. It is gradually
slowed down by the lunar gravity to 0.8 km/s (3.2 km/s -
2.4 km/s = 0.8 km/s). Gravitational pull of the Earth
accelerates the cargo by 11.2 km/s, which is the Earth's
escape velocity. An ion thruster guides the cargo toward
the terrestrial bolo. When the cargo is captured by the
terrestrial bolo, its velocity relative to the bolo is 4.3
km/s. (The cargo gains 3.5 km/s, which is the difference
between the Earth's escape velocity, and the orbital
velocity of the bolo, which is 7.7 km/s). The bolo is
larger than the lunavator, but it has the same design, and
is mounted on a rotating arm, which is attached to a large,
rotating, toroidal greenhouse. The bolo captures the cargo
and reels it in. Human crew divides the cargo, which is
called lunar cargo into 4 identical cargoes, which are
called terrestrial cargoes. The terrestrial cargoes and a
sling are secured to the bolo. The sling is placed at the
outer tip of the bolo, while the terrestrial cargoes are
evenly spaced along the bolo. When the bolo is accelerated
to its maximum angular velocity, the sling and the
terrestrial cargoes are released almost simultaneously. The
bolo reverses velocity of the cargoes and thus gains
orbital energy. The sling is released first. Its velocity
relative to the Earth is only 2 km/s. Before the sling is
released, small rocket engines permanently attached to both
ends of the the sling make it spin about the outer tip of
the bolo. At the same time a sounding rocket lifts a
payload to the altitude of 100 km. (My favorite propellant
for the sounding rocket is the hydrogen peroxide
monopropellant because it is safe and clean.) The payload
and the sling have the same mass; their total mass is the
same as the mass of the lunar cargo. The sling captures the
payload, which at this moment is stationary relative to the
Earth. The sling is made of Zylon and is strong enough to
reverse relative velocity of the terrestrial cargoes and
the payload. If we treat the momentum exchange as perfectly
elastic collision, the principle of conservation of linear
momentum implies that when the payload and the sling unite,
their velocity relative to the Earth is 1 km/s. The small
rocket engines permanently attached to the sling control
its angular momentum and guide it toward the terrestrial
cargoes. When the outermost terrestrial cargo is released
from the bolo, its velocity relative to the Earth is 3
km/s. After the exchange of momentum with the payload, its
velocity is reversed and reduced to only 0.2 km/s. At the
same time the payload velocity relative to the Earth is
increased from 1 km/s to 1.8 km/s. After momentum exchanges
with the four terrestrial cargoes the payload has the same
velocity (3.4 km/s relative to the Earth) as the bolo tip,
and it is captured by the bolo. If the payload is going to
be used in the greenhouse orbiting the Earth, the bolo's
winch reels it in. If it is going to be used in the
greenhouse orbiting the Moon, The bolo reverses payload's
velocity and hurls it toward the lunavator, which captures
it. Modern GPS technology guarantees high precision of all
maneuvers.

The lunavator and the bolo do not have to be made of
unobtanium, buckytubes, or even Zylon. Carbon fibers and
S-glass fibers are strong enough, and they are immune to
the radiation and temperature extremes of the outer space.
Perhaps the most practical material for the lunavator and
the bolo is a rope made of S-glass fibers fused together
under high tension and high temperature.

================================================== =======

PS. This is not just another newsgroup post, but history
in the making. I am going to post drawings and updates at:
http://www.islandone.org/LEOBiblio/S..._bolo_exchange

Andrew Nowicki wrote in message ...
The technology described in this post has not been tested, but
it looks trivial when compared to rocket launchers, and it
may reduce the cost of space access to a few dollars per kilogram!

The technology is based on GPS, a reusable sounding rocket,
cheap terrestrial bolo, cheap lunar rotovator, cheap cargo
sacks, and a small Zylon sling.

A suborbital rocket and some kind of a space tether does seem like
a very good way to reduce the cost to orbit.

The bolo and the rotovator
are useful terms defined by Robert Forward. They are described
he http://www.islandone.org/LEOBiblio/SPBI122.HTM
(Robert P. Hoyt calls lunar rotovator "lunavator.")

It seems funny to call a space tether with a tip speed of 1.6 km/sec
a "bolo" if it is orbiting Earth and a "rotovator" or "lunavator" when
it is orbiting the moon. The same device gets a different name
depending on where it is? There is no distinction in what a
simulator computes for either. Also, if you search for "rotovator"
in Google, most of what you get has nothing to do with "space tethers".
Anyway, I think it is better to just use "space tether".

The rotovator hurls the sacks filled with regolith (Moon dust)
towards the Earth.

In order to do this more than once, it needs to get momentum back
from someplace.

The next problem is that your sack will need some guidance and
thruster control to get exactly where it needs to go to. You can
not fling something 1/4 million miles and have it get within a
few meters of the spot you were aiming for at exactly the right
time.

It is mounted on a rotating arm which is
attached to a large, rotating, toroidal greenhouse. The arm
rotates independently of the greenhouse, so it can easily
change the angular velocity of the rotovator. The maximum
length of the rotovator is about 200 km.

With the mass of the tether and payload on a 200 km lever arm
you would need a *really* huge greenhouse to store up an
equal amount of angular momentum.

For a similar idea I like 2 hotels in GEO connected by a 20 km
tether and rotating fast enough to get 1/6th G. This is 131 m/sec
tip speed which is so low that the tether can be like 0.8% of
combined mass of the 2 hotels. Of course my hotels would have
greenhouses, but they are mostly hotels.

When a winch reels
its cargo in, the cargo moves faster to conserve its angular
momentum. This fact makes it possible to increase the orbital
energy of the rotovator and the greenhouse without the need
for any external thrust.

You conserve both your angular momentum (around own center
of mass) and your tether systems momentum around the moon. Since
you picked up something that was not moving, your overall orbital
speed is slower (more mass and less speed for same momentum).
So the opposite side of the orbit from where you pick up gets lower.
Depending on how high it was to start, you can only do this a few
times before you hit the moon. Why do you think you don't need
thrust?

When the
cargo is captured by the terrestrial bolo, its velocity
relative to the bolo is 4.3 km/s.

For spectra-2000 you would need a tether like 600 times as heavy
as your payload to handle a 4.3 km/s tip speed.

It is easy to design a reusable sounding rocket which lifts
the payload to the altitude of 100 km and accelerates it to the
velocity of 2.5 km/s. (When the payload separates from the
rocket, its total energy is equivalent to the kinetic energy
of only 3 km/s.)

I think it is easy to get a reusable sub-orbital rocket going
much faster than 2.5 km/sec. I think you are putting too much
work on the tether and not enough on the rocket.

In order for your LEO tether to pickup something every 90 minutes,
I think it has to be in an Equatorial orbit. But the moon only
crosses the equatorial plane every 2 weeks, so you can not toss
to it all the time from an Equatorial orbit. So I like the idea
of tossing to a lower tip speed tether at GEO which can toss
large collections of objects to the moon every 2 weeks. You save
huge in reducing the mass of your LEO tether because you can get
by with a lower tip speed tossing to GEO instead of the moon.
Think of it as a two stage tether system where the total mass
is less than a single stage tether system because of the exponential
tether mass problem. This is very much like the TSTO vs SSTO
problem. If you have equal mass going both directions (i.e.
as much regolith coming back from the moon as payload going to
the moon), then you don't need thrust on LEO-tether, GEO-tether,
or Lunar-tether.

But getting a setup working with the moon seems like a more costly
way to start than some others.

We like an EDT to boost momentum for the LEO tether and a solar sail
to boost momentum for the GEO tether. The mass for the solar cells
for the EDT or the solar sail for the GEO tether are not all that bad.
And once you have this infrastructure in place you could do a
reasonable sized payload (we work with 4,000 kg) every 90 minutes.
This looks like CATS to the Cates. :-)

Have you tried things on tether simulator?
http://spacetethers.com/spacetethers.html

-- Vince

(Vincent Cate) wrote in message . com...
We like an EDT to boost momentum for the LEO tether and a solar sail
to boost momentum for the GEO tether. The mass for the solar cells
for the EDT or the solar sail for the GEO tether are not all that bad.
And once you have this infrastructure in place you could do a
reasonable sized payload (we work with 4,000 kg) every 90 minutes.
This looks like CATS to the Cates. :-)

We also plan that most of the traffic to the GEO hotel is round
trip tourists. If the LEO-tether and GEO-tether are picking up
10 tourists at the same time they are sending 10 tourists home,
then there is no need for thrust (or regolith).

Only once per day do we do one-way traffic. We plan to open the
hotel when only some of the rooms are finished and just let
people stay for a shorter time. For example, if 1/7th of the rooms
are finished and the designed hotel capacity is for 1 week stays
with the tether transport capacity, then the average stay can only
be 1 day.

And that 90 minutes should really be 100 (I often forget this).
The problem is that while the orbit is 90 minutes, the launch
site on Earth and the GEO-hotel you are tossing to rotate during
this time. So for things to line up again it takes an extra
10 minutes, for a total of about 100.

-- Vince

Vincent Cate wrote:
VC The same device gets a different name depending on
VC where it is?

You did not read the web page which explains the difference:
http://www.islandone.org/LEOBiblio/SPBI122.HTM

The name depends on whether the device picks up
its cargo from the surface of a planet or a moon. If it
can do that, it is called the rotovator. If it cannot,
it is called the bolo. I have seen the rotovator term in
several publications.

AN The rotovator hurls the sacks filled with regolith
AN (Moon dust) towards the Earth.

AN In order to do this more than once, it needs to get
AN momentum back from someplace.

No, it does not.

VC The next problem is that your sack will need some
VC guidance and thruster control to get exactly where
VC it needs to go to. You can not fling something 1/4
VC million miles and have it get within a few meters
VC of the spot you were aiming for at exactly the right
VC time.

You did not read the web page about GPS accuracy:
http://gipsy.jpl.nasa.gov/igdg/syste....html#accuracy

VC With the mass of the tether and payload on a 200 km
VC lever arm you would need a *really* huge greenhouse
VC to store up an equal amount of angular momentum.

VC For a similar idea I like 2 hotels in GEO connected
VC by a 20 km tether and rotating fast enough to get
VC 1/6th G. This is 131 m/sec tip speed which is so
VC low that the tether can be like 0.8% of combined
VC mass of the 2 hotels. Of course my hotels would have
VC greenhouses, but they are mostly hotels.

I agree. The first, small system of this kind can be any
large spinning object. Note that the system can "bootstrap"
itself, which means that a small, one ton system can lift
into space a much more massive system.

AN When a winch reels its cargo in, the cargo moves
AN faster to conserve its angular momentum. This fact
AN makes it possible to increase the orbital energy
AN of the rotovator and the greenhouse without the need
AN for any external thrust.

VC You conserve both your angular momentum (around own
VC center of mass) and your tether systems momentum
VC around the moon. Since you picked up something that
VC was not moving, your overall orbital speed is slower
VC (more mass and less speed for same momentum). So the
VC opposite side of the orbit from where you pick up
VC gets lower. Depending on how high it was to start,
VC you can only do this a few times before you hit the
VC moon. Why do you think you don't need thrust?

The lunavator picks up cargo from the Moon, reels it in
and hurls it backward before it gets to the other side
of the Moon. Its orbital energy is increased, but its
angular momentum about its own center of mass is
decreased. This is why the arm is needed to adjust the
angular momentum of the lunavator. When you run out of
the angular momentum, you have to reverse the angular
velocity of the lunavator before you release its cargo.
(If you reverse the angular velocity of the lunavator,
you cannot pick up anything from the Moon unless you
reverse it again.)

AN When the cargo is captured by the terrestrial bolo,
AN its velocity relative to the bolo is 4.3 km/s.

VC For spectra-2000 you would need a tether like 600
VC times as heavy as your payload to handle a 4.3 km/s
VC tip speed.

You did not read the web page which explains it:
http://www.islandone.org/LEOBiblio/SPBI1SL.HTM

The characteristic velocity of Spectra 2000 is 2690 m/s,
so the minimum tether mass is about 40 times greater
than the cargo mass.

AN It is easy to design a reusable sounding rocket which
AN lifts the payload to the altitude of 100 km and accelerates
AN it to the velocity of 2.5 km/s. (When the payload separates
AN from the rocket, its total energy is equivalent to the
AN kinetic energy of only 3 km/s.)

VC I think it is easy to get a reusable sub-orbital rocket
VC going much faster than 2.5 km/sec. I think you are
VC putting too much work on the tether and not enough on
VC the rocket.

We could argue about that point for ever. I prefer to use
the tethers because they use almost no propellants. The
only consumables are Xenon gas used by the ion engines
and the cargo sacks.

VC In order for your LEO tether to pickup something every
VC 90 minutes, I think it has to be in an Equatorial orbit.
VC But the moon only crosses the equatorial plane every 2
VC weeks, so you can not toss to it all the time from an
VC Equatorial orbit.

No. The bolo orbit must be in the same plane as the Moon
orbit. This means that the sounding rockets are launched
from a different latitude in summer than in winter.

VC Have you tried things on tether simulator?
VC http://spacetethers.com/spacetethers.html

Yes, but it is too simple to simulate the system we are
talking about (lunavator bolo exchange). The system
is a complex celestial ballet of 3 rotating tethers. There
is a great need for a simulator that explains the ballet,
and you are the best guy to make such a simulator!

PS. I made another sling improvement: terrestrial cargoes
are attached to both ends of the sling when the sling is
released from the bolo. I also made a drawing of the
lunavator. It is posted at:
http://www.islandone.org/LEOBiblio/S...M/SPBI1324.JPG

Andrew Nowicki wrote:
AN I also made a drawing of the lunavator. It is posted at:
AN http://www.islandone.org/LEOBiblio/S...M/SPBI1324.JPG

Wrong URL. The drawing is posted at:
http://www.islandone.org/LEOBiblio/SPBI1324.JPG
and http://www.medianet.pl/~andrew/SPBI1324.JPG

Andrew Nowicki wrote:
AN I also made a drawing of the lunavator. It is posted at:
AN http://www.islandone.org/LEOBiblio/S...M/SPBI1324.JPG

Wrong URL. The drawing is posted at:
http://www.islandone.org/LEOBiblio/SPBI1324.JPG
and http://www.medianet.pl/~andrew/SPBI1324.JPG

Andrew Nowicki wrote in message ...
You did not read the web page which explains the difference:
http://www.islandone.org/LEOBiblio/SPBI122.HTM

In fact I did read it before posting. My previous
comment still stands.

VC In order to do this more than once, it needs to get
VC momentum back from someplace.

No, it does not.

Thats not an argument, that's just contradiction. :-)

VC The next problem is that your sack will need some
VC guidance and thruster control to get exactly where
VC it needs to go to. You can not fling something 1/4
VC million miles and have it get within a few meters
VC of the spot you were aiming for at exactly the right
VC time.

You did not read the web page about GPS accuracy:
http://gipsy.jpl.nasa.gov/igdg/syste....html#accuracy

Once again, yes, I looked at that. While it is true that
GPS can be made very accurate, this does not imply that
you can fling a sack from the moon and hit a 10 meter target
1/4 million miles away that is going around the Earth at
7.7 km/sec without any mid-course correction. If that is
in there, I missed it. :-)

VC For spectra-2000 you would need a tether like 600
VC times as heavy as your payload to handle a 4.3 km/s
VC tip speed.

You did not read the web page which explains it:
http://www.islandone.org/LEOBiblio/SPBI1SL.HTM

The characteristic velocity of Spectra 2000 is 2690 m/s,
so the minimum tether mass is about 40 times greater
than the cargo mass.

No, it is not. See, two can play contradiction. :-) Though this
is not the best use of a newsgroup.

We could argue about that point for ever.

No, I won't argue any of these points any more. We mostly have
contradiction and you telling me I have not read things I have read.
And that is not an argument worth attending.

Yes, but it is too simple to simulate the system we are
talking about (lunavator bolo exchange). The system
is a complex celestial ballet of 3 rotating tethers. There
is a great need for a simulator that explains the ballet,
and you are the best guy to make such a simulator!

In fact my simulator can handle 3 tethers at once (or any number).
And you can track a payload, or zoom and pan, etc. So you could
simulate and follow very complex things. It is just easier to develop
the parts separately. Once all the parts stop changing, I will
make a sort of movie where you can watch everything from start to
finish.

I also made a drawing of the
lunavator. It is posted at:
http://www.islandone.org/LEOBiblio/S...M/SPBI1324.JPG

It is really at:

http://www.islandone.org/LEOBiblio/SPBI1324.JPG

I love your 3D drawings.

-- Vince

Andrew Nowicki wrote in message ...
You did not read the web page which explains the difference:
http://www.islandone.org/LEOBiblio/SPBI122.HTM

In fact I did read it before posting. My previous
comment still stands.

VC In order to do this more than once, it needs to get
VC momentum back from someplace.

No, it does not.

Thats not an argument, that's just contradiction. :-)

VC The next problem is that your sack will need some
VC guidance and thruster control to get exactly where
VC it needs to go to. You can not fling something 1/4
VC million miles and have it get within a few meters
VC of the spot you were aiming for at exactly the right
VC time.

You did not read the web page about GPS accuracy:
http://gipsy.jpl.nasa.gov/igdg/syste....html#accuracy

Once again, yes, I looked at that. While it is true that
GPS can be made very accurate, this does not imply that
you can fling a sack from the moon and hit a 10 meter target
1/4 million miles away that is going around the Earth at
7.7 km/sec without any mid-course correction. If that is
in there, I missed it. :-)

VC For spectra-2000 you would need a tether like 600
VC times as heavy as your payload to handle a 4.3 km/s
VC tip speed.

You did not read the web page which explains it:
http://www.islandone.org/LEOBiblio/SPBI1SL.HTM

The characteristic velocity of Spectra 2000 is 2690 m/s,
so the minimum tether mass is about 40 times greater
than the cargo mass.

No, it is not. See, two can play contradiction. :-) Though this
is not the best use of a newsgroup.

We could argue about that point for ever.

No, I won't argue any of these points any more. We mostly have
contradiction and you telling me I have not read things I have read.
And that is not an argument worth attending.

Yes, but it is too simple to simulate the system we are
talking about (lunavator bolo exchange). The system
is a complex celestial ballet of 3 rotating tethers. There
is a great need for a simulator that explains the ballet,
and you are the best guy to make such a simulator!

In fact my simulator can handle 3 tethers at once (or any number).
And you can track a payload, or zoom and pan, etc. So you could
simulate and follow very complex things. It is just easier to develop
the parts separately. Once all the parts stop changing, I will
make a sort of movie where you can watch everything from start to
finish.

I also made a drawing of the
lunavator. It is posted at:
http://www.islandone.org/LEOBiblio/S...M/SPBI1324.JPG

It is really at:

http://www.islandone.org/LEOBiblio/SPBI1324.JPG

I love your 3D drawings.

-- Vince