RE: starship-design: FTL and Special Relativity

["Walker, Chris" <Chris.Walker@BSKYB.COM>]

Hi Tom,

> Please, Do not call my "Electric Armor" by any other name such as SMA
shell. 
> Name your own inventions if you wish not mine. Your suggested name SMA
reminds me
> of government jargon and I do my best to be jargon free in speech.
> Should your name catch on by accident...

Not my name! Industry-standard acronym. Just felt it described the invention
more precisely (ie. it's a shield made from a shape memory alloy). But, like
you say, it's your invention not mine. Yes - I do realise that many people
may very well not have heard of the acronym and so you wish to avoid using
this jargon in a broad public context. However, I was using it for shorthand
for this mailing list.

I was just thinking about the material fatigue issues. For example, say you
have an average of one particle impact every second. For a year-long
mission, you will have over 30 million impacts to deal with. This means 30M+
thermal and mechanical cycles that the electric armour will undergo. I'm no
materials scientist (you guessed? ;) but I think that fatigue failure would
be likely to occur more than once per year in this case, leading to frequent
replacements.

So, why not just use a big lump of material instead? Then, you just have to
deal with the erosion effects - needs replacing less often. Presumably, you
feel that the electric armour offers a sufficiently greater advantage to be
worthwhile using?

> Then and only then will I chose or not to replace the many pieces that
have 
> been replaced periodically in routine maintenance. 

Fair enough. Out of curiosity, do you envisage carrying the replacement
materials with you (costly), or manufacturing them on the voyage (eg. from
mining passing asteroids or planets)?

> I have addressed all the issues many years ago you raise now. I value your

> feedback and hope to complete a FAQ(jargonsorry). That I can refer new
readers 
> of my patent from 1988.

Would be a good idea. You may have addressed all the issues, but we don't
know your solutions until we ask ;)
 
> You do worry a lot you need to get out more. 

As a spacecraft subsystem engineer by trade (attitude and orbital control),
it's a job requirement to be conservative and worry about problems, both
likely and unlikely. My question (though intended more tounge-in-cheek as a
dig towards NASA's recenet "mishap") dealt with a simple risk assesment
issue. The chances of a launch going wrong and sending the craft towards
Earth may be low, but the consequences are very serious indeed.

Get out more to where? ;)

Regards,

Chris