Re: starship-design: Re: One way (again...)

[Kelly St <KellySt@aol.com>]

>> >If the parts are primary structure (remember we'll be shaving
>> >weight margines to get the thing flying) you need major shipyard
>> >facilities.
>>
>> I don't think we'll be shaving weight.  Even at .2c, the
>> thing has _got_ to last at least 20 years or the whole endeavor
>> wasn't worth a damn.
>
>Which is exactly the point. We have NEVER built any mechanism that was 
>designed to function flawlessly for twenty years without ongoing 
>maintenance. Historical evidence would tend to argue that we can't.

The deep space probes like Pioneer, Viking, and Voyager  had multi decade
service lives.  Thou thie trivially simple compare to these ships.

>> >>>Normal systems on that scale usually burn out after 40-50 years.
>> >>>Given the lack of replacement parts (stored parts also don't last
>> >>>forever),
>>
>> >>They don't have to last forever.  They just have to last several
>> >>decades.
>
>The Air Force places a red tag shelf life on safety harness webbing at five 
>years. This means if it sits on a shelf for five years, the inspector must 
>physically destroy the webbing rather than chance its being used 
>accidentally.

Oo, excelent example.  I forgot about material decays in plastics.



===>
>> Why would it almost certainly fail in months or years?  Exactly
>> what mission critical components are certain to fail, even with
>> triple redundancy?  (If there's only one or two crew left,
>> the life support systems will be well below capacity.)
>
>I already posted a long list of relatively simple, everyday items that must 
>be included on the ship, ALL of which will fail within five years.
>
>Here is a real good question for you: if you fill an air tank with 
>compressed air to 3,000 psi and put it on a shelf then come back five years 
>later, how much air is in the tank? Answer: 14 psi. We can't even build a 
>non-moving air tank that will hold air with no pressure loss for five 
>years. How are you going to keep it in the ship?

Excelant point.  One possible siolution for a star ship would be solder joints
on all seals.  If you want to rotate something, you heat the joints until they
melt, rotate them, then cool and resolder the joint.

Still would leak out all the air every few years thou.  Ox and CO2 isn't a big
problem, we can store tha in chemical bounds, but how the hell do you store
nitrogen?!  It doesn't bound well with anything,and cryo tanks would bleed off
long before we were done.

==>
>Lee

Kelly