# Re: USING A ELECTROMAGNETIC BEAM TO PROPELL A STARSHIP

```Kevin wrote:
>> But what has the upper hand? The constructive or destructive side... (This
>> was the reason for my inquiry.)
>
>Both.  Constructive in the direction of TC, destructive in other directions

Maybe I'll make a simulation about that some time.

>> I already thought this was the base of your misunderstanding. For what I
>> know (I'm not 100% certain) this method only increases resolution (in the
>> sense of larger angle deviations), but it does not decrease diffraction in
>> the same way.
>> The term interferometry points at the comparing of two parts of a wavefront.
>> The difference in phase is then used in calculations that increase the
>> resolution. I know it is a bit fague, but I don't have good literature about
>> it at the moment. (Feel free to attack me if you still feel you are right).
>
>ME? Attack? Never!  *8^S
>However, If it can produce better resolution, does this help the "jitter"
>problem?

Don't think so, however, those phased arrays (as I think they work) are
probably doing the thing you want.
One can focus radiowaves (using interference), by placing antennas in a line
at specific distances. Note however that these single antennas are radiating
in all directions (in contrary to a laser).

I'll check it out in literature if I get a chance.

>> Oops, last time I told you that the Doppler effect was cancelled for the
>> people in the starship, I think I was mistaken there.
>> Note the following expression for the Doppler shift, after the arrow I've
>> rewritten it so that you can see that there is more than f/gamma in it.
>>
>>                  2
>>        Sqrt[1 - b ]                             f       1
>> f'= f --------------  (where b=v/c) --> f' = ------- -------
>>           1 + b                               gamma   1 + b
>>
>
>Hmm... so earth would need to roughly double output near the middle of the
>pulse?
>where b=.99