Sling launch from lunar surface

Proposed system to launch raw materials from the lunar surface to
escape velocity:

At the top of a 160 meter tall tower is a platform rotating at 100 rpm.
Attached to the platform are two 160 meter tethers, also spinning,
with the acceleration at the tips of the tethers = 1790 gees. One kg
payloads of raw material slide 'down' each essentially-horizontal
tether and are released at lunar escape velocity. Assuming a launch
rate of about 1kg/second (3.6 ton/hr), the power consumption is less
than 3MW. No super-conducting, complex, reusable 'buckets' required,
as would be for a linear magnetic mass driver. The biggest concern
would be wear on the tethers. Perhaps this could be handled by having
an aluminum hollow cylinder bushing at the core of each payload and
current running down the cable so magnetic levitation would keep the
payload from contacting the tether.

Perhaps the tower could be eliminated if each tether has a maglev 'car'
at the tip, riding on a 1 km circumference passive aluminum track. The
'cars' and track would support the tethers during down time.

wrote in news:1138288465.715089.213180
@g14g2000cwa.googlegroups.com:

What are the tethers made of that they can instantly impart
several km/sec of velocity to that mass? Something's got
to give.

--Damon

Good idea.

But why not reel the tether out while accelerating? You have a tower
with a tether drum on top. While at rest, the tether is mostly reeled
in and the payload can be attached to the tip.

During acceleration, you reel out the tether. That reduces g-loads on
the payload and you do not have anything sliding along the tether.
Since a rotating tether in a vacuum is a very efficient energy storage
device, you could take as long as you want to spin up the tether,
depending on available power. You could even use it as a battery in the
night.

If the tower is high enough (approx. 1km) you can reduce tip
acceleration to a survivable level to launch soft payloads such as
humans.

It certainly makes much more sense than an electromagnetic accelerator.
You have energy storage built in and you have the potential to launch
soft payloads.

wrote in message
oups.com...
Proposed system to launch raw materials from the lunar surface to
escape velocity:

I do know that the space settlement researchers talked about a "rotary
pellet launcher" for the moon before they later hit on the idea of the
mass-driver. I would assume they dumped it for the mass-driver for one
advantage or another.

But I suppose it could be that what you're proposing might be significantly
different from their rotary pellet launcher concept.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

With a 160m high tower, able to support latera; forces, such a launcher
would mass more than a linear accelerator (also about 160m long).

If the tether could be played out and reeled in, then the tower could
perhaps be only 10m high, and this does become a possibility.

However, I think there will be accuracy problems - hitting a catcher in
space would require the release to be perfectly timed - I suspect nano
second level precision. So this would require launching cargoes with
their own guidance and propulsion. This puts up the minimum weight into
the multi kilo level.

Next, do the two tethers release their payloads at same time? In which
case they'll go on different orbits - one may be optimised, but you
can't do both.

Then you have to manage how the raw materials "slide" down the tether.
The tether will bemd, and the materials will have both tangential and
radial velocity.

This is all possible, though you might as well go for a simple mass
driver.

wrote in message
oups.com...
Proposed system to launch raw materials from the lunar surface to
escape velocity:

At the top of a 160 meter tall tower is a platform rotating at 100 rpm.
Attached to the platform are two 160 meter tethers, also spinning,
with the acceleration at the tips of the tethers = 1790 gees. One kg

hmmmmm, I wonder, is there any reason why the tether cannot be horizontal?
maybe not perfectly horizontal but a possible conical setup? would use a
shorter tower, or a hill of correct size.

No difference. This is the old rotary pellet launcher. The problems are
friction, too much of, and accuracy, not enough, by a lot.

wrote:
With a 160m high tower, able to support latera; forces, such a launcher
would mass more than a linear accelerator (also about 160m long).

If the tether could be played out and reeled in, then the tower could
perhaps be only 10m high, and this does become a possibility.

Another possibilty is to have sloping, rotating 160m-long arms to
support the tethers up to maybe 3 RPM. At that point, the tethers will
rise from the supports to a more horizontal position and continue
speeding up to 100 RPM. I prefer the maglev 'car' at the ends of the
tethers, riding on a track. The major point of using this system
versus an electromagnetic mass driver is avoiding complex and expensive
buckets.

However, I think there will be accuracy problems - hitting a catcher in
space would require the release to be perfectly timed - I suspect nano
second level precision. So this would require launching cargoes with
their own guidance and propulsion. This puts up the minimum weight into
the multi kilo level.

I think the tether could be made to vary the friction on the payload to
help time the release and, as I think electromagnetic mass driver
proponents have suggested, lasers beyond the release point could zap
the payload and tweak the trajectory.

Next, do the two tethers release their payloads at same time? In which
case they'll go on different orbits - one may be optimised, but you
can't do both.

No, the tethers don't release simultaneously; we could have an
off-center mass oscillating near the center of the platform, acting as
a counterbalance to the payloads being released every 1/2-revolution.

Then you have to manage how the raw materials "slide" down the tether.
The tether will bemd, and the materials will have both tangential and
radial velocity.

I'm not sure how much the tether will bend; the maglev 'car' at the end
may mass a lot more than a payload and keep the tether taut. I'm
planning on giving the payloads both a radial and tangential velocity
(roughly equal); if we slowly 'lowered' the payload to the tether end
and then released it with only a radial velocity, we'd need a 226m long
tether.

This is all possible, though you might as well go for a simple mass
driver.

Again, it's the superconducting 'buckets' that make a 'simple' mass
driver not so simple.

wrote in message
oups.com...

, as I think electromagnetic mass driver
proponents have suggested, lasers beyond the release point could zap
the payload and tweak the trajectory.

I think you mean electron beams.

Again, it's the superconducting 'buckets' that make a 'simple' mass
driver not so simple.

I've been wondering recently if Halbach Arrays of permanent magnets might
could replace the superconducting coils of a mass-driver bucket. I do know
they can be arrayed in toroidal shapes.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Mike Combs wrote:
wrote in message
oups.com...

, as I think electromagnetic mass driver
proponents have suggested, lasers beyond the release point could zap
the payload and tweak the trajectory.

I think you mean electron beams.

Again, it's the superconducting 'buckets' that make a 'simple' mass
driver not so simple.

I've been wondering recently if Halbach Arrays of permanent magnets might
could replace the superconducting coils of a mass-driver bucket. I do know
they can be arrayed in toroidal shapes.

Here's a partially-baked idea for a mass driver that has:
1) no contact, and so no friction, between payload and driver;
2) no need for high-tech containers (ex; with super-conducting coils);
3) no need to separate payload from container or recycle the
containers.

Look at the simple toys that use an electromagnet above an iron-bearing
toy (ex; a small globe) to lift it upwards. As the toy approaches the
magnet it blocks a light beam which causes the magnet to reduce the
upward force. Result: the toy hovers beneath the magnet. Voila,
poor-man's levitation.

Now imagine 1kg payloads of regolith/ore/whatever placed in cheap
standard steel cans. The cans are pushed beneath a long (160m or so)
rotating (100 RPM) arm covered with electromagnets and optical sensors.
Each can is pulled toward a magnet on the arm but the sensor keeps it
from quite reaching the magnet. Centrifugal force (yes, I know, a
useful illusion) pushes the can down the arm to the next magnet that
tugs on it, accelerating it to the speed of that segment of the arm.
Information on the mass and magnetic qualities of each can are sent to
the next magnet down the arm to set the initial force of that
electromagnet. The magnets would have to strongest at the tip of the
arm where the can would have to be pulled 'up' at 1790 gees while the
first magnet would only pull at 1/6 gee. Each can picks up both radial
and tangential velocities and leaves the arm at lunar escape velocity.

Obviously the tricky part is making the magnet control response fast
enough.