# starship-design: Re: Re: starship design

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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
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