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starship-design: Re: Re: regarding fuel expenditures

In a message dated 11/13/97 1:09:16 AM, you wrote:

>Hello Kelly,
>  Thanks for your response on the matter <grin>.  I have always enjoyed
>science fiction for two reasons.  The first is that it is entertaining,
>and the second is that some of the speculative stuff winds up becoming
>fact given enough time.

Same here.

>  If you ever get a change, and feel like taking the time and effort
>(which I suspect is in short supply <grin>), take a look at GURPS VEHICLES
>II, which is a set of comprehensive rules for approximating vehicles past,
>present, and future.  There are obvious "problems" and such, but for the
>most part, it makes a person think a little.  Recently, I began to think
>about what the interstellar probe might be like some 100 years of so into
>the future.  Using GURPS VEHICLES, I postulated a maglev like structure
>built upon the moon, or perhaps free floating in orbit.
>  In any case, the idea was to launch the device towards the earth, and
>from there, towards the sun.  The maglev launcher would launch a rocket
>assembly towards the sun such that the "rocket booster" wouldn't actually
>fire until the probe was near the hyperbola portion of it's "free fall
>towards the sun".  The rocket engine would insure that it went into a
>hyperbolic orbit.  While close to the sun, the separated assemblies (ie
>the rocket was exhausted and a small modest booster charge separated the
>payload from the booster) would go their own way, with the payload
>automatically spreading it's solar sails.  Using the solar sails as a
>further boost, the probe would accellerate to faster speeds.
>  My biggest question about the above mentioned "concept" is just how
>close could a payload come to the sun and not be damaged?
>  The other thing is, I never actually "designed" the payload system nor
>the booster system to see what the "imaginary" spaceprobe's top speed
>could be leaving the system.

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.

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.

>  On a related note: by chance, do you or anyone on your discussion list,
>know how to calculate proper motion with respect to stars?  I downloaded a
>50 meg hipparcos file some time back, and it has two entries for proper
>motion.  They look to be the same format as declination and right
>ascention.  I got the formula for converting right ascention and
>declination (along with the parallax) into cartesian co-ordinates.  What I
>would like to be able to do, is create, using TRUE BASIC, a program that
>will calculate not only the x,y,z co-ordinates, but also where those stars
>will be 50, 100, or 500 years from now.  Best of all, I can then begin to
>account for other factors such as the fact that a ship leaving a planet
>has the velocity of the planet plus or minus it's accelleration (dependant
>upon what direction the accelleration vector was aimed) along with the
>velocity of the star that the ship is leaving from.  Of course, this could
>work against the ship's favor if you have to overcome the star's velocity
>before you can accellerate towards a star that your sun is moving away

It takes thousands of years for stars to move visibly in the sky.  So as far
as a starship is concerned you can assume the possition relative to our sun
is fixed.

>  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.

>  Well, I have bent your ears enough, and I am probably boring you to
>tears.  Any help you could send my way would be greatly appreciated.
>     Respectfully yours,
>       Hal

Hop the above helps.