Re: starship-design: What is safest?

[TLG.van.der.Linden@tip.nl (Timothy van der Linden)]

Hello Kelly,

>>It has to be tough, but not into extremes, since backups are available or
>>will be shortly. I'd guess that if military cars had to be made more
>>reliable, they should not use air-pressured tires. Chances of a car getting
>>stranded by a punctured tire on rough terrain seem to be rather high.
>>BTW Many succesful explorers from the past used equipment that they could
>>repair or rebuild themselves without outside help. Several expedition
>>leaders designed equipment with that criteriom themselves before they went
>>exploring.
>
>True but unlike explorers of the past, interstellar explorers would be able to
>carru enough to fix things that are as sophisticated as they need.  We'ld
>probably need to accept that the exploration gear will only last a few years,
>archive the data, and make the ship systemsm durable enough to get back.

Explorers of the past could haul large amounts too, however it hindered
their progress, often too much to reach their goal.
We may be able to carry enough to fix sophisticated equipment, but it likely
would increase ship weight (and crew) far beyond what would be the minimum
for a succesful mission.

>>While some applications may ask for highgrad computing power, many don't
>>need to. In much electric equipment limits are pushed, something that we
>>certainly can't trust to do in our starship.
>>So we should make circuits/chips that have the computing power of x years
>>back but use the much more precise and reliable technology of today.
>
>Given that even 10 year old circuts are generally a 100 times less capable
>then current systems, that might not be acceptable.  Also its not clear that
>old design IC's built with new equipment would last especially longer then
>current designs built on the same equipment.

Well let me give a simple example then: Say you've two gears, in the past
the quality of steel was rather poor, so they had to be big to have a
reasonable lifetime. Now we can control the strength of steel much better so
can make these gears thinner and smaller and still have the same lifetime.
I'd guess that if we used better steel and kept the same size as in the
past, then we'd really increase lifetime.
Indeed the much larger mass of such a gear may not be acceptable, but if it
means that it will need much less maintenance, thus less crew, thus less
food, thus a smaller habitat, then I wonder if it really is less acceptable.

>>Similar to what Zenon wrote, we shouldn't expect the same luxuries as in our
>>homes.
>
>The ship is a high tech exploration system.  Computing power isn't a luxury.
>Any cut in computer sophistication will be a direct impact in the ability of
>the science teams on the ship to analiae the data the surveyteams on the
>ground, and the probes, recover.

Well, would todays technology combined with shortlived 2050 technology
really be too crude for an interstellar exploration mission?
(The 2050 equipment would be used until it failed and then the old and
easier to repair technology would be used for further exploration.)

>>>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 clean.
>>
>>If a fusion engine is so simple, then a fusion power plants should not be to
>>hard to build and maintain either. What I've seen from fusion power designs
>>is that they look pretty complex, more complex than chemical rocket engines.
>
>Power plants would need to be a little more complicated since they need to
>convert reactor power to electric power.  Also the current designs (ignoring
>the magnetic tourus systems which are pretty unusable) arn't that complicated.
>Even better most of their components are large blocks of materials (lenses and
>photo multipliers for laser fusion, thick conductor bands for magnetic and
>electrostatis control systems, heavy metal support structure, etc.).  Compared
>to a computer core their trivial.

I wasn't comparing with a computer core, but with a chemical propulsion
system (although I could have been more explicit). I believe that according
to Lee todays propulsion systems do have a MTBF long enough for a two-way
mission.
I wondered whether fusion rockets would have similar reliability, since they
likely are more complex than their chemical counterparts. And if our rockets
are pulsed, they may get much more structural stress than chemical rockets
that as far as I know are continuous.

Furthermore, while a fusion rocket may not need to turn the heat into
electricity, it still is comparable with a fusion powerplant, since it too
has to control the energy flow. It can't just be compared to a H-bomb, which
can freely expand in all directions and hoped to do as much damage as possible.

>>>>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.
>>
>>I don't know what kind of circuit failure you mean.
>
>Anything that could disrupt the function of the circut.  (Corosion shorting
>out pathways, capacitors starting to leak, diodes breaking down and not
>filtering the electron flows, IC chips logic burning out, etc.)

How do these kill people rapidly? I'd expect some authonomous backup systems.

Timothy