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At 6:18 PM 6/5/96, Timothy van der Linden wrote:
>Kevin wrote:
>>> I tried to keep it in the middle (laser or maser), at some places I even
>>> used EM-beams. I don't understand the explanation with your numbers above:
>>> You say the cost of a beaming station increases because the conversion from
>>> sunlight into electricity is ~ 10%, but masers don't need electricity too?
>>What I mean is that while there could be a way to turn sunlight to laser light
>>without going through an in-between step like electricity, there is no way to
>>do this for masers.  The sun's microwave output is just too dim compared
>>to its
>>visible output.
>Huh? I got the idea that you preferred maser because it is so efficient, now
>your saying that laser may not need an in-between-step, from which I would
>conclude that laser is a preferred method.
>Oh wait, you are pointing at two things here:
>maser: needs an extra step, easy to convert to electricity
>laser: may not need an extra step, less easy to convert to electricity
>Did I get it right?

The sail system for a microwave beam sail is simpler and lighter than for a
laser sail.

Of course if your using my hybrid fuel/sail configuration you want a havyer
sail...  ;)

>>>>>9 Red shift is especially important when the starship reaches relativistic
>>Okay, so it is an increased cost, and not a technical difficulty
>It may become a technical difficulty if the shift becomes too large, then
>the reflectivity (and absorption) may change for the worse. While it may not
>matter much that some energy is lost, it may matter that a small part (even
><0.001%) of high intensity radiation enters the crew space filled with
>sensitive computers etc.

Given the power levels were tossing about a .001% absorbtion would melt the

>>> 12.
>>> Yes, I know, but that doesn't decrease the weight of the sail, which may
>>> become a crucial point in the whole design. I'll add this in the solution
>>> section.
>>Agreed.  I like Kelly's idea of using 6Li for the sail, very elegant.

Thank you.

>Unless we need a sail for the way back home...

You make a new, far smaller & lighter, sail before you leave for home.

>>> Advantages:
>>> >3) Ship can accelerate continously, taking advantage of the time dialation
>>> >effect. and providing the crew with a near normal gravity environment
>>> Are other designs like fusion engines not able to do this? (in theory) The
>>> advantages of time dilations are not clear to me (see also 9)
>>I think the problem with the fusion rockets, is that in order to accelerate
>>continuously, the need planatary sized fuel tanks.  Kelly's top speed is about
>>.4C and that's taking advantage of every trick in the book.

<..and if anyone can suggest other books...>

>I agree, but it is only partly true, since you also need to decelerate using
>onboard reaction mass (not necessary fuel). If you accelerate too much, that
>amount of reaction mass needs to get bigger in order to be able to stop the
>>The main advantages of
>>Kelly's hybrid fusion/maser design are
>>1) lowered cost
>>2) decell stage is independent of earth.

I'ld add in technical fesability.  We still haven't fiqured out how to
brake a pure sail ship into a unprepared starsystem.

Also power requirements should be far less.

>>The advantage of time dialations, is that _all_ stars (within reason of
>>tend to be nearly the same time away (as seen by the crew) and much
>>savings of
>>food and other supplies can be acheived.  Also, regardless of the actual
>>based) time of flight, earth (or the return masers) only need to send out
>>a two-year long pulse of energy to sustain the flight

Did you mean to say return masers?  Obviously the 2 year pulse bit works
outgoing, but not incoming, ships.



Kelly Starks                       Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)