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RE: starship-design: What is safest?

On Sunday, December 14, 1997 10:01 AM, Timothy van der Linden 
[SMTP:TLG.van.der.Linden@tip.nl] wrote:
> But is designing for a doubling of lifetime impossible in the next few
> decades?

I think I would plan on it.

> 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?

I would think that the engines would experience the greatest amount of wear 
and tear of the entire system. In fact, it may be advisable to plan on a 
complete rebuild or a complete replacement set for the trip back. It really 
depends upon the eventual mission profile and burn time though. I don't 
remember the exact number, but current thrusters that are being researched 
(not built) top out at only a few thousand hours of use.

For a mission profile built around an initial boost with a long coast phase 
this probably wouldn't be a problem (3 months = 2,000 hours). If it becomes 
possible to boost continuously, then we are looking at engine service 
lifetimes around 20,000 hours assuming a rebuild at the other end (or one 
way). Incidentally, that is sufficient boost time to take us practically 
anywhere in the local group.


                                                      (o o)