# Re: New idea Laser launcher/scoop systems

To Kelly,

>>I assume that with "impulse ratio" you mean "impulse velocity". Than the
>>So after "extracting" the energy of the fusion fuel, you could better dump
>>the excess mass without accelerating it! (Because if you accelerate it the
>>other mass could be accelerated less)
>
>Actually no.  Specific impulse is a term with rockets that tells how much
>thrust you can get out of a mass of reaction mass or fuel.  (in a normal
>rocket they are the same.)  For example a pound of hydrogen and oxegen
>pumped into a shuttle motor generates about 455 pound secounds of thrust.

(Meaning 1 pound can lift 455 pound?)

>My numbers showed that unless the specific impulse were geting out of the
>Explorer classes engines is over 2,000,000 we don't get to go.

I think the specific impulse can be calculated as follows:

Spec. Impulse = Vexh/a    (non-relativistic)

Vexh=exhaust velocity
a=acceleration (10 m/s/s)

So that would give a Spec.Imp. of about 2.5E6

>So I was
>woundering is using the fusion fuel directly would make more or less
>performance mass sence then mixing it in with extra reaction mass, or
>converting the power to electricity that accelerates a smaller reaction
>mass in a lineac?

I'm sorry, I cannot make sense of this sentence, I think you made some
writing errors.

>Given that the energy in the fusion reactors was all
>turned into kinetic energy in the exaust plasma, I had assumed using it
>directly would be most efficent.

Ofcourse that depends on the possible efficiency and on the exhaust speed of
the plasma. Can the latter be regulated by making the outlets smaller or