Re: starship-design: Modular Ship Design

[KellySt@aol.com]

Kelly,



I have been thinking more about the modular concept. Although I still like

the idea of modularizing the ship, I am less enthusiastic about moving the

engine form one end to the other. There are a number of technical

difficulties which although, not insurmountable, would make it rather

cumbersome, chief among which is suddenly having the floor of the living

section become the ceiling....

Since I had a centrafuge with rotating segments.  The floor's can move to the
sides front or rear as nessisary. Or for that mater you could just flip the
hab segment over as you restack the modular ship?



If on the other hand the main living quarters were to be built in the center

of the ship surrounded on all sides by the fuel tank, the protection would

be optimum. Then we go back to spinning the ship end for end. Due to the

fuel/payload ratios of the first few ships to go out (assuming fusion or

fusion hybrid rather than pure antimatter) there will be plenty of fuel for

shielding.



I would still want to be able to detach the engine module for local

intersystem exploration. Which means that it would need to have some

redundant tankage of its own on board. I am envisioning something like a can

in shape, with some of the systems shaped like wafers attached to the front

and rear of the can so they can be easily detached.

By picking Lithum-proton as a fusion fuel, I figured we could do without tanks
at all since the fuel is a structural metal.  So the drive system is
effectivly a tug pushing a huge (or small depending) solid block of metal.
Wrap yourself in it for shielding, stack it in frount for easy shoving, maybe
even use it for structural supports.


I also erred in assuming that a faster return trajectory was possible this

way. The problem is again the fuel to payload ratio. The mass of the

research/exploration module although not small, is insignificant when

compared to the mass of the fuel. There might be some decrease in trip time,

but I doubt it would be much.

Yeah even with fusion your ship looks like a huge block of fuel with a little
ship (probably half engine by weight, attached to it.



I am still leaning toward a continuous engine burn rather than coasting. The

fuel requirement is much larger, but within reach and the decrease in trip

time is significant. The key factor there is actually going to be engine

lifetime as we had discussed earlier. Current magnetic nozzle technology is

several generations short of being able to provide burn time measured in

months or years but I feel confident that the next fifty years will see

major changes in the state of the art.

I don't worry as much about burn time limits, but with the fuel carry limits
we have a prett much fixed upper speed limit.  I'ld rather get to it quickly,
not speed half the flight geting to speed.



Lee Parker

Kelly