cheap orbital insertion

From: Ed Minchau [mailto:ed_minchau@...]

A mass driver consists of a series of solenoids, which move a charged
projectile

I think you mean a "magnetic" projectile. For example, the O'Neill mass
driver used a "bucket" which had superconducting coils. But the issue there
is circulating currents, not charge.

along their length by alternately turning on and off one
by one.

The mass driver I propose would consist of solenoids 100 m in
diameter,

Wow, nobody can accuse you of thinking small. I once designed a space
launcher for a sci-fi novella. (
http://members.aol.com/howiecombs/bridge.htm
) Bearing in mind that the
expense of the launcher would be directly proportional to its size, I made
it as small as possible, with a diameter just large enough to surround a
vehicle sized for passengers two abreast. But an awful lot could be
launched from such a launcher, provided that turn-around times could be made
short.

made of a superconducting material.

Actually, there's no need for the accelerating coils to be superconductive.
Each coil only fires for the briefest of instants, so dissipating the heat
is no problem. Superconducting coils in the launch vehicle would be
advantageous, though.

They would be spaced
along the mountain range so that they would provide a constant 3g
acceleration.

Again, bearing in mind that cost would scale with size, I made mine as short
as possible, and assumed a 10 G launch. This would be fine for most
reasonably-fit people for the few seconds required.

The projectile would resemble a supersonic airplane,
gliding from one solenoid to the next. A maglev track could be used
to provide the initial velocity required for the airfoil to provide
sufficient lift to carry the craft from one solenoid to the next.

In earlier mass driver models, dynamic induction levitation was used to
provide lift. Later models used a pull-only mode of operation, which
provided a strong centering force on the bucket and thus enabled them to
eliminate the levitation strips.

The craft would make a series of parabolic glides until it received
its final boost at the end of the mass driver.

I think you may be assuming a greater separation between driver coils than
what may be practical. I'll admit I don't have a firm notion of what's
correct here, but I'm thinking it would be measured in a few feet, and I
suspect you're thinking in terms of miles.

I figure that such a mass driver would have to be about 1500 miles
long to achieve escape velocity at 3g.

Mine started out at 100 km launching raw materials at 30 Gs, then was later
expanded to a little over two hundred kilometers for satellite launching at
20 Gs, then later grew to three hundred and ten kilometers (186 mi.) for 10
G launching of passengers. But like I said, this was just for a sci-fi
story. I'm not sure I really believe in 186 mile long mass drivers.

Regards,

Mike Combs

From:
Ed Minchau [mailto:ed_minchau@...]
A mass driver consists of a series of solenoids, which move a charged
projectile

I think you mean a "magnetic" projectile. For example, the O'Neill mass driver used a "bucket" which had superconducting coils. But the issue there is circulating currents, not charge.

along their length by alternately turning on and off one
by one.
The mass driver I propose would consist of solenoids 100 m in
diameter,

Wow, nobody can accuse you of thinking small. I once designed a space launcher for a sci-fi novella. (
http://members.aol.com/howiecombs/bridge.htm
) Bearing in mind that the expense of the launcher would be directly proportional to its size, I made it as small as possible, with a diameter just large enough to surround a vehicle sized for passengers two abreast. But an awful lot could be launched from such a launcher, provided that turn-around times could be made short.

made of a superconducting material.

Actually, there's no need for the accelerating coils to be superconductive. Each coil only fires for the briefest of instants, so dissipating the heat is no problem. Superconducting coils in the launch vehicle would be advantageous, though.

They would be spaced
along the mountain range so that they would provide a constant 3g
acceleration.

Again, bearing in mind that cost would scale with size, I made mine as short as possible, and assumed a 10 G launch. This would be fine for most reasonably-fit people for the few seconds required.

The projectile would resemble a supersonic airplane,
gliding from one solenoid to the next. A maglev track could be used
to provide the initial velocity required for the airfoil to provide
sufficient lift to carry the craft from one solenoid to the next.

In earlier mass driver models, dynamic induction levitation was used to provide lift. Later models used a pull-only mode of operation, which provided a strong centering force on the bucket and thus enabled them to eliminate the levitation strips.
The craft would make a series of parabolic glides until it received
its final boost at the end of the mass driver.

I think you may be assuming a greater separation between driver coils than what may be practical. I'll admit I don't have a firm notion of what's correct here, but I'm thinking it would be measured in a few feet, and I suspect you're thinking in terms of miles.
I figure that such a mass driver would have to be about 1500 miles
long to achieve escape velocity at 3g.

Mine started out at 100 km launching raw materials at 30 Gs, then was later expanded to a little over two hundred kilometers for satellite launching at 20 Gs, then later grew to three hundred and ten kilometers (186 mi.) for 10 G launching of passengers. But like I said, this was just for a sci-fi story. I'm not sure I really believe in 186 mile long mass drivers.

Regards,
Mike Combs