starship-design: Re: Re: starship design

[KellySt@aol.com]

Hi Timothy,

Sounds like you have some good ideas.  You might want to join the group to 
discus them.  I'll comment on a couple points here and forward the message to 
the group. 


> Fusion drives can convert only about 1% of the mass of  
> their fuel into energy.

Actually its usually less then 1/2 to 1/3rd of that.


> This means That a direct thrust fusion drive can attain 
> a maximium exchaust velocity of abot 10% of light 
> speed. The velocity attained by a rocket is = to the 
> exchaust velocity tiimes the natural logarithim of 
> the mass ratio.  A mass fraction per stage of about 5-1 
> is the most that is realistic. ==

Here we disagree.  In space the mass ratio of a stage can be expanded to 
rediculas degrees.  I assumed a Lithium-6 fuel cycle since the stuf has a lot 
of power and is a stable structural metal.  With no tank required you could 
have a fuel mass ratio of 100's.  Your acceleration rate would suffer, but 
you could do it, and for a starship you would need too!

> == A fusion rocket stage with an exchaust velocity of .1c 
>  and a mass ratio of 5-1 burns out at 16% of light 
> velocity. A two (5-1) stage fusion rocket is required 
> to reach .32c. A three( 5-1) stage fusion rocket can 
> reach .48c. The maximium delta v availible on a 
> roundtrip mission is thus .12c. A one way decelerated 
> mission could reach .24 c. ==

I think I figured a 50-1 ratio would give you about a .4c delta V.  Hence 
things like fuel/sail or explorer where external sources of fuel/thrust were 
used to provide half the delta-v, and they needed to refuel in the target 
system.  I.E. we'll need a big telescope array to verify a good fuel ore bed 
in system orbit!! 

> ==There are 2 types of fusion pulse rockets that could 
> be used in this way.These are an Orion class fusion 
> nuclear pulse rocket  which detonates a sequance of 
> multimegaton h-bombs behind an inertial plate or a 
> deadalus class nuclear pulse rocket. To make a practical
> deadalus class system requires the use of lithium 
> hydride fuel pellets with a mass of 1mg to 1gm per 
> pellet. To theorecticly induce fusion in the pellets 
> lasers beams of the following power level are 
> required. A 1mg pellet needs  to be zapped with at 
> least a 500 kilowatt laser discharge to heat it up 
> to 200,000,000 centigrade and cause fusion reactions
> to even theoreticly occurr. A 1 gm pellet requires 
> a laser discharge of at least 500,000,000 watts to 
> heat it up to 200,000,000 centigrade.Also the pellets
> should be in the shape of disks so that 2 laser beams 
> can zap them simultaneusly on the top and the 
> bottom of the pellets to heat them up.

Well there are other configurations, but I agree pulse fusion systems are a 
good idea.

> You would also need a superconducting 10 tesla 
> electromagnetic nozzle and a couple of large nuclear 
> fission reactors capable of generating 500kw to 500 mw 
> of electric power per reactor. ===

Ah you can use the fusion reactors to produce some power.  You'ld need some 
power for start up, or for base load during the mission.

> ===I have many starship designs of many kinds. 
> Nuclear electric ramjets and rockets are not the
>  only starship designs that I have.
> 
> Timothy J. Mayes

Send them on to the group.

Kelly