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Re: starship-design: What is safest?

In a message dated 12/14/97 10:24:53 PM, TLG.van.der.Linden@tip.nl wrote:

>>>Before making the discussion unnecessary long: What kind of repairs do you
>>>consider to be mayor and to be necessary in 60 years but not within 30?
>>More structural repair due to fatigue and corosion.  Power cables and
>>distrabution systems, reaction vessels for life support reactions
>>of water, air processing and synthasis, etc), plumbing, ductwork, pumps,
>>bearings for the hab centrafuge, etc.  Also electronics get increasingly
>>erratic at those ages.
>But is designing for a doubling of lifetime impossible in the next few
>In what way can current Eartly goods be compared to the equipment we need.
>Are there any goods of which lifetime doesn't depend on costeffectiveness?
>(Ie. Are there manufacturers for whom it pays to design a 3 times more
>expensive product but with a 2 times longer lifetime?)

Impossible?  In some cases yes, in others no.  Certainly many things could be
designed more resilantly, but the military has pushed that pretty hard already
in a lot of areas.  Other systems age because of effects we don't know how to
correct, and have been trying to compensate for.

All in all, I'ld expect we could improve a lot of stuff, and have assumed that
for the 40 year life expectence assuption.  Geting even that far is iffy,
beyond seems really unlikely.

>>Food also becomes an issue.
>For some reason 40 years of freezedried food doesn't soon very appealing. I
>guess that potato chips may be a useful food source after all. ;)

Frozen foods, not freeze dried (except for emergency reserves).  I'm not
crazy!  ;)

>>Paradoxicly the engines to boost back are fairly safe.  They don't need
>>complex micro systems, and being unpowered arn't under load or much thermal
>>stress.  Due to the large scale these engines and reactors must be.  Minor
>>corosion on metal to metal contact points isn't critical.  To be stable the
>>engines would have to stick to simple stable alloys (copper vers super
>>conductors etc.), which would also increase stability.  
>While an engine may be more robust than "micro systems", it also has to cope
>with orders of magnitude more stresses. Won't these stresses speed up metal
>fatigue beyond proportion?

To a degree, but the drive is only run a few months, rather then decades, and
has to be rated for full operation for those months under any condition.  So
it would need a lot of reserve toughness built in.

>>So a 2 way flight puts most stress on the drive systems, which generally
>>only been used for a few months, but least on the general suport systems for
>>the ship which have alread  been in use for deacades.
>It does however need to gather bulk amounts of fuel in the target system.
>(Assuming you don't need other infrastructure like beaming stations.)

True you need minning and processing equip.  Hence my selection of a
plentifull, easy to mine fuel.  ;)