Mining the Sky & Space Tethers to achieve LEO

From: Ian Woollard
To: spacesettlers@egroups.com
Sent: Thursday, December 21, 2000 9:11 PM
Subject: Re: [spacesettlers] Re: Mining the Sky & Space Tethers to achieve LEO

bill t wrote:

>> Tom - exactly what is a coil gun and who is working on it? Saddam?
>>
>> Bill
>>
>
> Actually the American military have a working prototype of a coilgun
> used as a weapon.
>
> A coil gun is a what O'neil called a mass launcher.

I looked into this stuff a while back.

Coil guns can do about 2.5 km/s which is enough for the
moon (or punching though armour plate), but I think it runs
out of 'steam' after that. The inductance of the coils gets
to be a huge problem.

Tom - I am concerned about mass drivers being used in orbits where space habitats will reside. You see, each pellet or rock become a projectile which, if launched into the right orbit, will eventually return as an earth crossing object. Only if the projectiles were fired in a direction retrograde to earth's orbit would they be safe for long-term use.
Nuclear powered plasma rockets are my preference. In space around the earth, power can be sent from the moon or space station to the " space tug" via microwaves since aroung 10 MW would be needed. With an ISP of 3000 to 30,000 for a VASIMR rocket, why use anything else? Just use H2 for fuel.

Rail guns have a higher top speed. Atleast that's what
I heard.

Rail guns don't have a theoretical top speed- they don't have
much inductance. I think they're up around 3 or 4 km/s,
state of the art- the rails tend to erode when you launch
and that's a bit of a problem really.

Then there's the Jules Verne gun (light gas gun). This can
handle 5+km/s. There's no limit to the top speed of this
one that I'm aware of. Even a table top example outperforms
a Coil gun.

Actually the military are interested in this, but not quite
as interested as you might think. One problem is that
they tend to leave a rather too neat hole. The military like
more of a mess ;-)
Tom - I suspect that a neat or jagged hole in an incoming warhead would be just fine :-) provided it could be targeted. I suspect that the military is focusing on chemical UV or soft X ray lasers as weapons of choice for warhead destruction.

> Bill

From:
Ian Woollard
To:
spacesettlers@egroups.com
Sent:
Thursday, December 21, 2000 9:11 PM
Subject:
Re: [spacesettlers] Re: Mining the Sky & Space Tethers to achieve LEO
bill t wrote:
>> Tom - exactly what is a coil gun and who is working on it? Saddam?
>>
>> Bill
>>
>
> Actually the American military have a working prototype of a coilgun
> used as a weapon.
>
> A coil gun is a what O'neil called a mass launcher.
I looked into this stuff a while back.
Coil guns can do about 2.5 km/s which is enough for the
moon (or punching though armour plate), but I think it runs
out of 'steam' after that. The inductance of the coils gets
to be a huge problem.
Tom - I am concerned about mass drivers being used in orbits where space habitats will reside. You see, each pellet or rock become a projectile which, if launched into the right orbit, will eventually return as an earth crossing object. Only if the projectiles were fired in a direction retrograde to earth's orbit would they be safe for long-term use.
Nuclear powered plasma rockets are my preference. In space around the earth, power can be sent from the moon or space station to the " space tug" via microwaves since aroung 10 MW would be needed. With an ISP of 3000 to 30,000 for a VASIMR rocket, why use anything else? Just use H2 for fuel.
Rail guns have a higher top speed. Atleast that's what
I heard.
Rail guns don't have a theoretical top speed- they don't have
much inductance. I think they're up around 3 or 4 km/s,
state of the art- the rails tend to erode when you launch
and that's a bit of a problem really.
Then there's the Jules Verne gun (light gas gun). This can
handle 5+km/s. There's no limit to the top speed of this
one that I'm aware of. Even a table top example outperforms
a Coil gun.
Actually the military are interested in this, but not quite
as interested as you might think. One problem is that
they tend to leave a rather too neat hole. The military like
more of a mess ;-)
Tom - I suspect that a neat or jagged hole in an incoming warhead would be just fine :-) provided it could be targeted. I suspect that the military is focusing on chemical UV or soft X ray lasers as weapons of choice for warhead destruction.