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[Fwd: Re: starship-design: Hitching a Ride on a Magnetic Bubble]

-------- Original Message --------
Subject: Re: starship-design: Hitching a Ride on a Magnetic Bubble
Date: Sun, 08 Oct 2000 21:06:43 -0400
From: curtismanges@netscape.net (Curtis Manges)
Reply-To: curtismanges@netscape.net (Curtis Manges)
To: STAR1SHIP@aol.com
Cc: starship-design@lists.uoregon.edu
References: <6e.3b1bd19.27115c4f@aol.com>


you wrote:

The inverse square law 
> limits the practicality as the observed sun grows dimmer and smaller wrt to 
> the bubble. For the conservation of energy or momentum to balance on both 
> sides of the equation, an added energy source would be in order.
> Energy added to the bubble from internally aboard the craft may be required 
> to cancel the remainder of the inverse square function. 

When I looked at this thing and sent it, it just seemed like a neat idea and I hadn't examined it critically, but I have to agree that this thing wouldn't be very effective beyond some range; the acceleration would have to fall off to a useless value. 

If this is what you want to do, it's all right, but I personally don't care much for sailcraft; I think their mission abilities are too limited by their means of propulsion.

I don't really think the mag-sail has any advantage over an ion drive, and it has definite disadvantages.

Anyway, this all reminds me of how little of the sun's energy we collect in the first place. I did an extremely rude approximation once, and I think I recall that the amount of the sun's total output that hits Earth is like 
1x10E-23. (Feel free to double-check that for me; it was quite a while ago that I did it.) So, when you go throwing inverse-square into the mix, the free lunch is going to end somewhere, as it wasn't much to begin with. Wherever that somewhere is, an ion engine (or other reaction device) could continue to accelerate and the sail would not.

Keep looking up,