Re: My Two Bits Ain't Worth 1E-15 (Take 2)

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

Hi Brian,

I first like to say something to you, I'm having troubles reading your
messages, I am not sure if it is because English is not my native language
or that it is your writing. Anyway I have the feeling that sometimes you
jump too fast to an idea (you warned us about that in one of your first
letters, I think). So before I can understand what you are talking about,
I've need to read a certain part several times. I'm not sure if others have
a similar problem, but would it be possible to write some things more clear?

>Okay, I just realized something about my two bits worth.  They ain't worth 
>squat.  I ran the numbers for 11GW/ton/s on my portable RPB decelerator idea 
>and came back to the same problem that Kelly has with his Explorer design. 
> We need too stinkin much power.
>
> Assuming 11GW/ton/s to accelerate a measly .036 g and using a De + 3He 
>reaction that yields 3.606E14 Watts/kg and applying that over the time it 
>takes to accelerate to 1/3c at .036 g the numbers got supremely ugly in 
>terms of fusion fuel weight.

Besides the amount of fuel needed, the time needed is too much too. I
calculated that it takes 9 years to reach 1/3c at 0.036 g. In that time we
will have travelled 1.5 ly. And then we still will need to decelerate.

>Back to the drawing board.
>
>Perhaps the launcher idea could still work with the Explorer design.   What 
>we have to do turn the Asimov into its own fuel launcher.  Have the ship 
>rail gun launch most to all of the ship's reaction mass behind it.  The 
>particles will have to be at least fast enough to cover  a .25 ly track in 
>the time it takes to cruise to Tau Ceti.

Why would you first shoot the RM out of the back, to catch it again later?
(after decelerating a bit)

>I wonder: If we could keep the track together over that amount of time and 
>distance, would it be easier to launch the track from Earth?  Would the 
>stablizing system that Kevin told us about help?  I noticed this discussion 
>but I don't know if it answers my question:

< A disscusion left out >

>So is the answer yes or no.

I think we more or less agreed that particle beams are possible but only for
not too large distances (less than 1 ly).

>As the Asimov begins its deceleration phase, the relatively faster moving 
>reaction mass track slams back into the ship.  We ionize the RM and run it 
>through the accelerator for thrust just as if it were interstellar medium. 
> A downside to this idea is the drag caused by hitting the really fast 
>particles at the end of the deceleration run.   Also there are going to be 
>serious power cost to launch the track.

I think this drag will cause more problems then it solves. The extra energy
needed to overcome the drag could just as well be used to take some extra RM
with the Asimov.

>Since we'll have to carry so much reaction mass for the launch track, I 
>suggest we use the E18W we have planned to mag-sail launch the ship.   So I 
>guess we launch the track via the ion accelerator using it as a rail gun if 
>that is possible.

This part is an example of the kind of thing where I don't get what you want
to say even after reading it several times.


Timothy