Coil guns vs. mass drivers

Bill,

It would be helpful to see a sketch of the design being considered. If the acceleration is similar to the linear motor concept being used for maglev trains, then I don't understand the design limitation. At the higher velocity sections, the propulsion magnets could be spaced further apart if timing becomes an issue. In a vacuum, the only constraint I am aware of is the ability to construct the magnetic support rails exceedingly straight. The structure might be blown around by the solar wind :-)

Tom
From: bill t
To: spacesettlers@egroups.com
Sent: Wednesday, December 27, 2000 7:36 PM
Subject: [spacesettlers] Re: Coil guns vs. mass drivers

The inductance will limit the acceleration not the velocity. The DOD
were building high acceleration devices (>100 g). I had did the
calculations about a decade ago, and came up with a safe acceleration
to escape velocity of about 70 m/s^2. I'll try to dig up my old notes
and transcribe it for everyone and you can try to find problems with
the physics.

Bill

--- In spacesettlers@egroups.com, "Mike Combs" wrote:
> --- In spacesettlers@egroups.com, Ian Woollard
> wrote:
> >
> > 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.
>
> Actually, I've heard pessimists proclaim that coil guns can't even
> get up to 1 km/s, which would mean that they couldn't even be used
as
> a lunar launcher. But as I remarked in "Making Dreams from
> Moondust", I'm not sure a direct comparison can be drawn between the
> kind of coil gun that the DoD funded, and the kind of mass driver
> O'Neill was experimenting with. I know I did get a reply from Dr.
> Les Snively, who worked with O'Neill on Mass Driver 3. He said that
> the coil rise time the critics were pointing to as an insuperable
> problem was an implicit part of their models.
>
> I still consider it within the realm of possibility that those who
> built that coilgun for the military simply erred in some fundamental
> way, and that the mass driver may still work as anticipated.
>
> And as you say later, the erosure problem rail guns have may be a
> show stopper there.
>
> Regards,
> Mike Combs

It would be helpful to see a sketch of the design being considered. If the acceleration is similar to the linear motor concept being used for maglev trains, then I don't understand the design limitation. At the higher velocity sections, the propulsion magnets could be spaced further apart if timing becomes an issue. In a vacuum, the only constraint I am aware of is the ability to construct the magnetic support rails exceedingly straight. The structure might be blown around by the solar wind :-)

Tom
From:
bill t
To:
spacesettlers@egroups.com
Sent:
Wednesday, December 27, 2000 7:36 PM
Subject:
[spacesettlers] Re: Coil guns vs. mass drivers
The inductance will limit the acceleration not the velocity. The DOD
were building high acceleration devices (>100 g). I had did the
calculations about a decade ago, and came up with a safe acceleration
to escape velocity of about 70 m/s^2. I'll try to dig up my old notes
and transcribe it for everyone and you can try to find problems with
the physics.
Bill
--- In spacesettlers@egroups.com, "Mike Combs"
> --- In spacesettlers@egroups.com, Ian Woollard
> wrote:
> >
> > 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.
>
> Actually, I've heard pessimists proclaim that coil guns can't even
> get up to 1 km/s, which would mean that they couldn't even be used
as