[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: starship-design: What is savest?

In a message dated 12/9/97 6:51:22 AM, TLG.van.der.Linden@tip.nl wrote:

>Zenon wrote: (But the message is to all)
>>>   ;)  Ah but that one would be impossible, or at least an order or two
>>> magnitude more expensive.
>>?? As follows from all our discussions,
>>the biggest problem is the propulsion.
>>And the one-way mission has only HALF of this problem.
>>So you calim that having half the problem makes 
>>it impossible or more expensive?
>>I agree that the one-way outpost-building mission
>>will need more supplies (including a sort of factory
>>to build even more at the target), but I think
>>this additional cost will be negligible as compared with
>>the cost of engine/fuel needed for the way back.
>>The engine for a two-way mission must be made reliable 
>>for twice the time and for two start-cruise-stop cycles.
>It is almost a fact that every two-way mission needs to get its fuel for the
>return-trip from the target system. That is, if you want to decrease cost
>(and thus effort).
>If a design allows to do without resources from the target system, it means
>that fuel supplies square, which usually makes bad numbers worst.
>However most of our designs can't do without resources from the target
>system anyway, so we have to face that we'll need some form of industry at
>the target system. This does not necessarily mean that we need complete
>rocket building factories, but instead specialized fuel or other bulk ore
>The question is how much effort would a one-way mission save? It likely does
>need less bulk resources, but more specialized resources. There's a big
>chance that both kinds of mission will cost as much.
>There is however a big advantage of staying in the target system, rather
>than "floating" through space another 10 year. In the target system you have
>all the resources you want (including energy), but in space you've nothing.
>Also in the target system you won't need your most critical (and likely most
>deteriorating) part of the ship: The engines.
>Kelly continously tells us, that to stay at the target system we need to be
>selfsufficient. But don't we need to be selfsufficient if we stay from home
>20 years (which is the minimum time for a two-way mission)?
>In short, I'm not so much wondering what is cheaper, but more about what is
>saver. Or to put is less subjective: What has a bigger chance of succeeding?

Actually because staying in place requires you stay longer, and thus need more
suplied, repairs, etc.  I do think the 2-way would be cheaper, smaller, and
more relyable.

In our case the engines are actually not a big factor.  You need the full set
of engines to decel into the system, or you'ld overshoot.  On a boost back, if
some of the engines fail, you drop them and burn the others longer until you
use up the rest of the fuel.  You might want to drop them anyway to cut weight
and increase your total speed a bit.  (The decel burn into Sol doesn't use the
ships engines in any of our systems.