RE: starship-design: Re: Re: regarding fuel expenditures

["L. Parker" <lparker@cacaphony.net>]

On Friday, November 14, 1997 4:41 PM, KellySt@aol.com 
[SMTP:KellySt@aol.com] wrote:
>
> In a message dated 11/13/97 1:09:16 AM, you wrote:

Kelly, I didn't get Hal's address from this post. If you know what it was 
you might want to forward the information at the end to
>
> You really don't need to do the sligshot manuvers around Earth and the
> Sun.
>  A star Ship needs such powerfull engines, and has to boost to such high
> speeds, that the gains from these manuvers are a joke.

Not quite true, that particular orbital maneuver has already been 
researched thoroughly, we have even discussed it here. It is called the 
"Powered Perihelion Maneuver" and is capable of generating up 400 g's of 
thrust initially. The drawback of course is that this thrust is more than a 
human can withstand and that it tapers off as your course takes you further 
from the sun.

Due to human limitations, the highest cruise velocity obtainable without 
further boost from some other sort of engine is only 0.003 c. Something 
akin to Forward's Starwisp on the other hand, could be accelerated to over 
0.3 c in only a few days and even faster using a combination of this 
maneuver and follow on beamed power from an orbital power satellite.

>
> How close a probe could get to the sun depends on what kind of
> shielding/cooling system it uses, and the amount of time it stays there,
> so
> their no simple answer.

This maneuver was calculated at 0.1 AU (about 1 solar radius) which was 
calculated to be the closest feasible approach without getting into thermal 
shielding difficulties. Even so, the sail would be operating at between 
1,000 and 1,750 K depending on its reflectivity.

On a related note, I went back through some old material relating to sails 
and found mention of a pure boron sail which would be analogous to your 
lithium sail. It was spec'd to be only 10 ^-8 m thick, which based on what 
you and David and I were discussing, might be thick enough to stop a 
significant amount of protons. However, boron's melting temperature is 2600 
K ... I don't think we would need to worry about it at any velocity we are 
likely to attain with a sail.

> >  What I would really "love" to do, is create some form of random
> >  Stellar
> >system generation program that would "accrete" the formation of the
> >system, calculate the planetary density, radius, and so forth.  Then, if
> >I
> >could get a few realistic formulas regarding formation of planets and so
> >on, I could create a program that would simulate the universe within a
> >set
> >"distance" of earth, and allow people to interact with it as though they
> >were "exploring" the universe.  It would take into account the fantasy
> >Faster than light drives, along with some of the more realistic Slower
> >than light drives.
>
> You might be able to find such programs as shareware somewhere.  Can't
> think
> of where of hand though.

Search the net under the keyword "starfire" there is such a program, it 
generates random star systems from a seed. I don't remember if it also 
generated planets or not. I believe it probably did because it was designed 
to generate a playing field for the RPG "Starfire". The output is a text 
file.

Lee