Re: RE: starship-design: Pellet track

[KellySt@aol.com]

In a message dated 8/18/97 4:25:11 PM, lparker@cacaphony.net (L. Parker)
wrote:

>Just a general observation for everyone to think about...we are doing this 
>backwards...
>
>Kelly and Isaac were (are) having a conversation from which this is
excerpted:
>
>>>Assuming a .1% percentage, a rocket with a 10:1 thrust/weight ratio
>>>and 1 millions sec Isp would be absorbing 10^12 watts/kg in waste
>>>heat.  Without massive heat rejection systems (which would adversely
>>>affect the thrust/weight ratio), that's going to melt the rocket in
>>>a fraction of a second.
>
>>>Therefore I don't consider the Bussard Votage compressions system
>>>to truly offer a plausible chance at such high thrust/weight ratios,
>>>considering how various components are directly impacted by fusion
>>>products (thus implying a significant waste heat problem).
>
>>Actually the Bussard system use anti-nutronic fuels that convert virtually
>>all the power of the fusion reaction into the kinetic energy of the charged
>>waste particals.  Efficency is about 99.9+%.  (give or take).  Most of the
>>waste can just be vented to the sides.  
>
>There is a great deal more, but the relevant parts have already been stated.
>
>First, any sort of rocket propulsion capable of propelling a starship needs
an
>ISP of about 1 million give or take a few.
>  
>Second, any such propulsion system is going to generate waste heat.
>
>Third, it is fairly likely that the total thermal gain to the ship is going
to
>
>be significant, NO MATTER WHICH SPECIFIC DRIVE YOU USE.
>
>Fourth, the ship will be subjected to this temperature continuously for
extremely
>long periods of time and will therefore also be subject to thermal and
elastic
>
>fatigue.
>
>There are no metals, alloys, ablatives, or EM fields currently available to
deal
>with this thermal gain. It will occur with fusion drives, plasma drives,
photon
>
>drives and antimatter drives. It will even occur with Kyle's ZPE drive. So
lets
>reverse engineer this thing. Start by assuming a particular metal alloy for
the
>
>skin of the ship, determine its melting point, divide by two for a safety
margin,
>now; what efficiency is NECESSARY in order to get an ISP of 1 million
without 
>exceeding the figure we just arrived at? Can we design a and build a drive
to those
>requirements?
>
>Lee 


Good point but a little misstated.  The specific impulse isn't related to the
heat load.  And the question is what is the heat gain, and the wait of te
cooling system.

Kelly