Thread: TL9 Spaceships
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Old 08-13-2011, 02:48 PM   #37
teviet
 
Join Date: May 2005
Default Re: TL9 Spaceships

Quote:
Originally Posted by munin View Post
The heliopause is in the neighborhood of 100 AUs from the sun. For a magsail to maintain constant acceleration all the way out to there it would need to increase its loop circumference also by a factor of 100, implying that it only has 1% of its cable spooled out when traveling at 1 AU (it can't spool out more closer to the sun because there's a point where, as you said, the acceleration of a larger loop exceeds the cable's tensile strength). I don't think you would design a magsail that way, you'd have the whole thing spooled out all the time and just get less acceleration as you move further from the sun -- and I think the Spaceships magsail stats are based on having the entire mass of the system devoted to acceleration, and not spooled up. Thus the rule on p. 39 to divide the magsail's acceleration by (1/D)^2 (though it is weird it's not mentioned in the magsail's description, like the light sail).
Sorry, I did say that I was talking about magsails in reality, not GURPS magsails, so the assumptions will be different. Feel free to ignore me! :)

But if you're still interested... a real magsail would not deploy to its full radius in all environments, because it wouldn't be able to maintain a magnetosphere; it would collapse under stellar wind pressure. Instead it would deploy multiple loops of smaller radius. At larger distances it would deploy the same cable in fewer loops of larger radius.

Double-checking my notes, the net acceleration will not be constant, but will decrease as 1/D rather than 1/D^2.

I haven't read up as much on the M2P2 sail; maybe it can maintain constant acceleration, but it might also need more consumables as it expands.

TeV
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