Re: Rail gun


G. R. L. Cowan wrote:
Brian McDermott wrote:

boss_not_in@xxxxxxxxxxxx wrote:
How about if we put a railgun in a vacum chamber and fire a projectile
at very high speed toward a target. The target is a 2cm diameter capsule
full with hydrogen/duetrium.
Will that able to ignite fusion reaction?

From this website;
http://www.powerlabs.org/railgun.htm

"RailGuns are by far the most spectacular type of electromagnetic
accelerators ever developed. They hold the record for fastest object
accelerated of a significant mass, for the 16000m/s firing of a .1 gram
object by Sandia National Research Laboratories' 6mm Hypervelocity Launcher,
and they can also propel objects of very sizeable masses to equally
impressive velocities, such as in the picture to the left, where Maxwell
Laboratories' 32Megajoule gun fires a 1.6kilogram projectile at 3300m/s
(that's 9megajoules of kinetic energy!) at Green Farm research facility."

The required muzzle velocity of your proposed rail gun would have to be
many times the escape velocity of Earth in order to work to produce
fusion.

How much, do you think? A few years ago I thought frozen D2 and T2
on the tips of heavy metal bullets might do the job, because the
heavy hydrogens would hit and the bullets behind them would keep on
coming, and do work on the DT plasma, making it hotter than it would
otherwise be. But then I realized all the electrons that could get free
in a heavy metal plasma would tend to limit the temperature rise.


--- G. R. L. Cowan, former hydrogen fan
Burn boron in pure oxygen for vehicle power:
http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.html




Ok, time for a little math. We're going to assume the following:

-a solid 2 gram (1 mole, 6.02x10^23 atoms) Deuterium ice "bullet" fired
at a stationary Deuterium ice target;

-A fusion burn temperature of 20 keV, or roughly 220 million degrees.

In order to get the atoms in the bullet to fuse with those in the
target, the kinetic energy of each atom in the bullet needs to be
20keV. We convert 20,000eV into Joules:

(20,000)*(1.6x10^-19)=3.2x10^-15 Joules per atom

Because the bullet has a mass of 2 grams (0.002kg), it is the
equivalent of one mole of deuterium, and thus contains 6.02x10^23
atoms. Thus, we find the total kinetic energy in the bullet:

(3.2x10^-15)(6.02x10^23)=1.9x10^9 Joules

That's a ton of energy, and I mean that literally because one ton of
TNT is about the same as 4.184x10^9 joules. But let's take this to
completion and solve for velocity:

E=(1/2)mv^2

manipulating, we get:

V=sqrt(2E/m)

V=sqrt(2(1.9x10^9)/0.002)

V=1.4x10^6 meters/second

That's just over a million meters per second, about 1400 kilometers per
second, 875 miles per second, or nearly 1 percent the speed of light.
Earth's escape velocity is 11 kilometers per second, so you're looking
at a muzzle velocity over 100 times greater than that.

Each D-D fusion releases about 3meV worth of energy. Thus, one mole of
fused deuterium is worth about 3x10^11 Joules. You'd have a net gain of
2 orders of magnitude if you could get such a system to work, assuming
no losses and 100% efficiency.

Possible? Maybe. Plausible? Probably not. Practical? I'll let you
answer that for yourselves.

QED,

Brian McDermott

.

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