starship-design: Re: Anti-antimatter

[TLG.van.der.Linden@tip.nl (Timothy van der Linden)]

Timothy replies to Ken:

>Could someone please re-post Timothy's 1/30 Re: 
>Relativistic Electric Thrusters so I could try to read it?  Thanks!

I'll sent it to you at the same time this letter is sent.

>	As for the ongoing discussion on Relativistic Thrusters, I'm 
>slowly getting up to speed. I checked out Timothy's Web Page and saw why 
>a fusion spacecraft should limit the fuel speed to 0.1c; I didn't check 
>the numbers, but it sounds reasonable.

Since Rex has done similar calculations and got the same numbers, I'm quite
confident about the results.

>	So for self-powered ships, that seems to leave relativistic 
>engines to the regime where you can transfer your ship mass to energy 
>with a near-unity efficiency.

And even then, only if you want high (>0.9c) final velocities of the
spaceship (high velocity means more energy)

>  The most obvious way to do this is with 
>antimatter, of course, but here I'm a bit skeptical.  Even if we're 
>assuming some pretty amazing technological advances, I find it hard to 
>imagine storing huge quantities of anti-matter on a ship.  I don't know 
>if this has been discussed already, but I would guess there would be 
>some sort of theoretical minimum matter/antimatter ratio, just from 
>containment considerations.  Anyone want to tackle that one?

A minimum ratio? Why would do you think that?

>	So, keeping this in mind, here are another two ideas for 
>"antimatter-type" engines; ways to convert mass to pure energy--without 
>using antimatter.  These are nearly as speculative as large-scale 
>antimatter containment, but I'd still argue that they're more probable.

I've thought of a flywheel before, but never mentioned it because it seemed
too unpractical:

- Its estimated weight was too high.
- Containing/guiding a huge fly wheel that rotates with super high
  velocities seemed almost infeasable.

>So already, for a 200 meter radius flywheel, 
>we're talking about an energy storage of 10^10 J/Kg.  We'd probably need 
>at least 10^14 J/Kg to make a decent spaceship.

Actually I think that 1E16 J/kg is the absolute minimum if you want to get
into the direction of relativistic velocities.

>	Idea #2:  Catalyze nucleon decay using captured magnetic 
>monopoles.

The mean idea of using a monopole is probably it's heigh energy:weight
ratio. Maybe we can find other ways to store energy.
For example storing photons in a perfect mirror sphere.

Timothy