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Re: Re: starship-design: What is safest?

In a message dated 12/20/97 7:23:56 AM, TLG.van.der.Linden@tip.nl wrote:

>>>What areas and why would they do that? What if a 2 times longer life means
>>>3 times higher price? From an economical view, the latter would likely make
>>>little sense, so I wonder if the military did research in that direction.
>>The Mercedes Benz economics.  Military systems do get that kind of treatment
>>since they HAVE to work, and will be used in the worst situations.  NASA and
>>space systems get that treatment sometimes too.  But to a degree it is
>>assumed you can fix things in a decade or four, and you usually throw things
>>away, even if working fine, after a half century or so.
>What military system HAS to work? Virtually all systems have backups of some
>kind. While the backup is being used, the primary system can be repaired or
>replaced with all the outside help that may be needed.
>In case of field equipment where no direct outside help is available there
>too are many (although less efficient) backups available. It would not be
>very smart to bet on one single system during a fight, no matter how well

To a degree ALL important systems are dedsigned that way.  You always make
sure the failure of one system would shut everything down, or at least not
shut it down catostrophicly.  But that not always practical.  Rip one of the 4
tires of a truck or car, and the vehical is stuck until fixed.  Since Military
equipment is usually operated in as bad a situation as we can find (war) and
put to the most adverse conditions the enimy can find, and operated away from
suply and sevicing bases, its has to be very tough.  Just like exploration

>>Some things are easy to make more long lived.  Heavier structures, thicker
>>tubing, better filtration on working fluids, etc will obvioiusly compensate
>>for a lot of things, if you can afford the weight.  Circutry, and IC chips
>>a bigger problem, especially if you don't want to dramatically decrease
>>abilities.  Etc..
>When parallel computing is made to work, then making computers more robust
>is supposed to be easy. Furhermore superconducting magnets are great to
>avoid mechanical wear. (I'd suggest you'd use these on your hab train.)
>Also shielding equipment from a normal moist, temparture fluctuating, dusty
>environment increases lifetime significantly.

Shadow processors are used even now to keep a hot back up, or verification
systems, on-line.  But sooner or later the computers will fail, and after
comparativly short service lives.

>>>Reserve toughness? So one can build in more than enough reserve (double?)
>>>toughness for engines, but not for micro objects that have much less
>>>This argument doesn't fully convince me.
>>The engines stress would be simple structural and thermal loads.  So you can
>>compensate with tougher structures.  Because of their scale the kind of
>>corosion or microdamage that would criple a micro object, would be
>>to small to effect the performance of a macro object.  Think of a pit of
>>corrosion the size of a pencil point on the surface of a sheet of metal as
>>think as table top.  Now think if the same corrosion on the srface of a IC
>>chip, or a junction of an printed circut board.  The very scale of the
>>make one vulnerable, the other indifferent, to the same damage.
>"Simple" structural loads? While the exhaust of a rocket engine looks crude
>and simple, the complete engine consists much more than that. I wonder if
>the fusion engines make the design simpler. That little bit of corrosion you
>talked about may very well affect reflectivity/conductivity that will
>escalate the corrosion within seconds (or less).

The fusion engines are far simpler then standard rocket engines.  I.E. few
pumps, nozzels, no presure vessels, etc.  I'm not clear what you mean about
reflectivity/conductivity.  Certainly a system with the scale your talking
about wouldn't have its conductivity effected by surface blemishes.  If its a
problem, design the system so it will work with the entire surface corroded or

>If an engine part fails, disasterous things will happen. If a circuitboard
>fails, it likely can be repaired before lifetreathening situations arise.

That depends un what the circut board controls.  Circut failures can and do
kill people rapidly.