Latest on lunar mass drivers

Can anyone point me to recent studies done on lunar mass drivers?

In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?

Thanks

Alex

Alex Terrell wrote:
Can anyone point me to recent studies done on lunar mass drivers?

In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

Use a big gun, direct chemical to kinetic energy conversion.

(Indirect at the microscopic level, it just skips the electricity part.)

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

No, better to use aluminum.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

The general idea is to make them long and slow, so that people can ride
out with the cargo, and the cargo can be actual functioning spacecraft.

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?

Not that I know of.

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kT wrote:
Alex Terrell wrote:
Can anyone point me to recent studies done on lunar mass drivers?

In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

Use a big gun, direct chemical to kinetic energy conversion.

(Indirect at the microscopic level, it just skips the electricity part.)

At the 2km/s level the charge would need to weigh more than the pellet.
What material would you use?

If you make it on the moon, you use electricity to make the chemical
energy, so this would actually be less direct.

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

No, better to use aluminum.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

The general idea is to make them long and slow, so that people can ride
out with the cargo, and the cargo can be actual functioning spacecraft.

That might have been in the 60s Sci-Fi, but even on the moon this would
need some 30km long accelerator. Better send the people up by elevator
or rocket. They don't weigh much.

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?

Not that I know of.

Thanks anyway.

"Alex Terrell" wrote:

:In the 70s, these were conceived as being several miles long, but now
:it seems only 160m or so is enough. How short can they be?

How much acceleration can you stand and how firmly can you anchor your
coils?

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Alex Terrell wrote:
kT wrote:
Alex Terrell wrote:
Can anyone point me to recent studies done on lunar mass drivers?

In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?
Use a big gun, direct chemical to kinetic energy conversion.

(Indirect at the microscopic level, it just skips the electricity part.)

At the 2km/s level the charge would need to weigh more than the pellet.
What material would you use?

Moon Dirt. It's the only game in town.

If you make it on the moon, you use electricity to make the chemical
energy, so this would actually be less direct.

I thought you were just going to take the big gun with you.

You know, for a media stunt : shoot the moon.

Real men shoot guns. Use a golf ball.

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?
No, better to use aluminum.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?
The general idea is to make them long and slow, so that people can ride
out with the cargo, and the cargo can be actual functioning spacecraft.

That might have been in the 60s Sci-Fi, but even on the moon this would
need some 30km long accelerator. Better send the people up by elevator
or rocket. They don't weigh much.

In the future the moon will be a vast industrial wasteland :

This End Up City. I'm sure they'll be able to handle it.

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?
Not that I know of.

Thanks anyway.

My pleasure. Good luck with it.

How many Ares IV launches do you think it will take?

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"Alex Terrell" wrote in message
ups.com...

Can anyone point me to recent studies done on lunar mass drivers?
In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

160 m was as short as I ever heard speculation on.

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

Do you mean in the bucket, or in the launcher itself? The bucket coils were
conceived of as being super-conductive, but the drive coils were ordinary
aluminum wire. Although... there was a proposal for something called a
Quench Gun which relied on a superconducting effect in the drive coils for
operation. I don't know nearly as much about that, but I've gotten the
impression that while it might have a smaller mass budget than the
mass-driver, it might not have the rapid fire rate.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

It's expected that the buckets will be decelerated (allowing the payload to
fly free), recirculated, and reused.

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?


Every so often SSI says something about new mass-driver studies. I don't
know if this is just to drum up contributor interest, or if it genuinely is
on the back-burner.

I would just keep up with SSI announcements (http://ssi.org). If anybody
were to start up new mass-driver research, it would be them.

--


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

In article ,
"Mike Combs" wrote:

Every so often SSI says something about new mass-driver studies. I don't
know if this is just to drum up contributor interest, or if it genuinely is
on the back-burner.

I would just keep up with SSI announcements (http://ssi.org). If anybody
were to start up new mass-driver research, it would be them.

Well, maybe. I get the impression that SSI as a whole has grown a bit
distinguished (read "old") and weary, and doesn't actually do much
anymore. Their last website update seems to be from last June, for
example. I also have somehow gotten the impression that the SSI folks
believe (perhaps justifiably) that the mass-driver problem has been
essentially solved, and doesn't need any further research.

For both reasons (if there is any truth to them), I wouldn't be
surprised to see the next big advancements in lunar mass drivers to come
from someplace else.

Best,
- Joe

Mike Combs wrote:
"Alex Terrell" wrote in message
ups.com...

Can anyone point me to recent studies done on lunar mass drivers?
In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

160 m was as short as I ever heard speculation on.

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

Do you mean in the bucket, or in the launcher itself? The bucket coils were
conceived of as being super-conductive, but the drive coils were ordinary
aluminum wire. Although... there was a proposal for something called a
Quench Gun which relied on a superconducting effect in the drive coils for
operation. I don't know nearly as much about that, but I've gotten the
impression that while it might have a smaller mass budget than the
mass-driver, it might not have the rapid fire rate.

If the coil is simple aluminium, it could be launched as part of the
payload. Making a "disposable" coil would be easy, though energy
intensive. It would depend on the relative value of energy on lunar
surface and in orbit.

Superconducting bucket coils would be tricky but probably better than
driver superconductors.

The quench gun seems to be a way to store large amounts of energy in a
superconducting drive coil. This means no capacitors are needed. The
proposal I saw was for launching 1.5 ton tanks of Oxygen, but I'd
prefer to launch 1kg pellets. Assuming bucket of 1kg, 2kg total, this
is only 5MJ. Assuming 50% efficiency, 10MJ, with a peak power of 100MW.
Advanced power capacitors deliver 4KW / Kg, so 2.5 tons of capacitors
are all that's needed.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

It's expected that the buckets will be decelerated (allowing the payload to
fly free), recirculated, and reused.

Makes sense

With a 10cm bore, it would seem a catapult launching 1kg pellets could
be quite light - perhaps only 100 tons or so. Are there any recent
engineering studies into this?


Every so often SSI says something about new mass-driver studies. I don't
know if this is just to drum up contributor interest, or if it genuinely is
on the back-burner.

I would just keep up with SSI announcements (http://ssi.org). If anybody
were to start up new mass-driver research, it would be them.

They've done some good work - especially reducing the size of the
launcher to something even NASA could consider.

Alex Terrell wrote:

Every so often SSI says something about new mass-driver studies. I don't
know if this is just to drum up contributor interest, or if it genuinely is
on the back-burner.

I would just keep up with SSI announcements (http://ssi.org). If anybody
were to start up new mass-driver research, it would be them.

They've done some good work - especially reducing the size of the
launcher to something even NASA could consider.

SSI doesn't do anything much of anything anymore.

--
The Tsiolkovsky Group : http://www.lifeform.org

My Planetary BLOB : http://cosmic.lifeform.org

Get A Free Orbiter Space Flight Simulator :

http://orbit.medphys.ucl.ac.uk/orbit.html

In article ,
Mike Combs wrote:
In the 70s, these were conceived as being several miles long, but now
it seems only 160m or so is enough. How short can they be?

160 m was as short as I ever heard speculation on.

Could be rather shorter than that, in principle, given that extremely high
accelerations proved to be rather easy to achieve. Note, one crucial
realization was that a practical mass driver is a linear synchronous
motor, *not* a linear induction motor -- the latter do not scale at all
well to high accelerations.

If memory serves, at the end of the old SSI work, people were talking
seriously about 10,000G mass drivers, which would give you lunar escape
velocity in circa 27m (plus roughly the same again to decelerate the
buckets). Depends on whether you're up to solving the structural and
electrical problems of such rapid acceleration, of course...

There are some studies proposing superconducting coils. Are these
necessary or will aluminium do?

Do you mean in the bucket, or in the launcher itself? The bucket coils were
conceived of as being super-conductive, but the drive coils were ordinary
aluminum wire.

There were various schemes, with reliance on superconductors generally
dropping as time went on and people found ways to do the job with ordinary
metals. If (dim) memory serves, there were at least proposals for
entirely non-superconducting mass drivers, although it's less convenient
that way.

Is the current thinking to reuse the the launch drive (induction
coils), or to fire these with the cargo?

It's expected that the buckets will be decelerated (allowing the payload to
fly free), recirculated, and reused.

That is, in fact, the definition of a mass driver. (It's not a generic
synonym for "electromagnetic catapult".) The big advantage, of course, is
that with a mass driver and a "catcher" system, you can launch very small,
cheap, "dumb" payloads -- just lunar soil in glass-fiber bags -- which
lets you make the mass driver small.
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