# starship-design: Focusing on the problem (or focusing IS the problem)

```DotarSojat@aol.com wrote:

<Parts snipped because I'm still too confused to make proper comment>

> 2. DATA FOR 100-LIGHT-YEAR TRIP (in spite of the above)
>
> A run with the program SAILTRIP (appended to my 9/20 note) with
> DSTAR = 100 lt-yr gives the following data for the one-way trip:
>
> Proper (ship) time = 23.8473 yr
> Apparent (Earth) time = 104.2934 yr
> Total Earth time for emission = 4.2934 yr
> Peak proper velocity = 7.2603 lt-yr/yr
> Peak apparent velocity = 0.9906 lt-yr/yr
> Minimum acceleration (at turnover) = 0.0685 g
> Exhaust velocity for deceleration = 0.89346 lt-yr/yr
> Mass ratio for deceleration (eta = 1.0) = 33.62
>
> The trip time for the crew is not as short as Kevin estimated
> ("ten years") because the acceleration is so low for most of the

Hey!  I'm nearly within a factor of 2.  Not bad for a rough guess  8-p

> trip.  His estimates for emission time ("3-4 ... year"), Earth
> time for round trip ("a good 250 years") and speed ("insanly
> high fractions of C") are pretty good, however.
>
> Rex   <DotarSojat@aol.com>  (Rex Finke)
>
> P.S. To Timothy: You're right in advising Nick not to use aspects
> of both particle and wave mechanics at the same time to define
> the Doppler effects.  (And welcome back, Nick; even though the
> Group became aware of me late, I have continuous copies of the
> April, 1995, to make me aware of previous member contributions.)

Okay,

Now about focusing,  Do you mean to say, that a mirror
(forget masers, starships, and everything else for the moment)
just a simple mirror cannot be made to focus on a spot 6 lightyears
distant?  I find this really hard to accept.  What is the nature of
the interference, or have I mis-understood what you said.

I'm going to go back and read your message again.  hopefully more
of it will make sense this time.

--
Kevin "Tex" Houston 	http://umn.edu/~hous0042/index.html

```