Re: starship-design: Engine Parameters

["N. Lindberg" <nlindber@u.washington.edu>]

Lee,
	here are some comments on your low/medium/high categories.
An acceleration of 90 m/ss for your high engine performance is
impractical.  This is for the simple reason that this equals about nine
gee's.  Even if an engine could be made to do this, no human frame can
take that much acceleration for more than a few minutes (here I assume we
continue with the idea of manned missions, even an unmanned vessel's
electronics would have to be special built to take the strain).
Military pilots wearing g-suits are limited to 9.5 gees for a few
seconds. 
	As for the middle range, having done some aerobatics myself, I can
truthfully relate that taking three gees is somewhat uncomfortable, and
doctors know that it isn't good for you in the long run.
	NASA has probably done gee tolerance studies that give better
numbers, but I personally would be loath to spend the next several years
at more than 1.5 gees.
Best Regards
Nels


On Thu, 8 Oct 1998, L. Parker wrote:

> Okay, since we all pretty much agree that predicting what the engine will be
> is impossible, and that the likelihood of something unpredictable happening
> between now and fifty years from now is at least a non-zero number <G> lets
> do as Nels suggests and propose a set of requirements that will define
> performance parameters necessary to propel several different classes of
> ships. I would suggest basing the classes on a low median and high model of
> performance based on the following divisions:
> 
> LOW: Thrust is not continuous, may never exceed 10 m/sec, total change in
> delta v of 100,000 km/sec (1/3 c)
> 
> MEDIAN: Thrust may extend for long periods but is not normally for entire
> mission duration, may achieve transient thrust levels of up to 30 m/sec,
> total delta v limited to 200,000 km/sec (2/3 c)
> 
> HIGH: Thrust is typically continuous over duration of mission, maximum
> acceleration is 90 m/sec, total delta v is 300,000 km/sec (0.99 c)
> 
> All of these assume an acceleration deceleration phase with no reserve fuel,
> change in delta v is a maximum only and assumes there is enough fuel to
> decelerate also (in other words, the delta v figures should really be
> doubled).
> 
> Comments or suggestions?
> 
> Lee
> 
>