starship-design: Re: Solar sail breaking

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

Hi Nick,

>(The photons is reflected, so its change in momentum is twice the magnitude
>of its initial Doppler shifted momentum. I think that the reflected photon
>is of the same -shifted- frequency of the incident photon, since otherwise
>the solar sail would have to absorb more energy than it radiated, and this
>surely cannot be a theoretical requirement;

The sail does radiate more energy than it receives. How else are you going
to stop the starship and loose kinetic energy.

>I need some help on the following point. Does time dilation result in the
>high velocity starship intercepting more photons per unit time than an
>observer in orbit around the star sees the star emit in the ship's
>direction?
>Does relativity really increase both the impulse gained from
>each photon AND the photon flux (in the ship's frame)? I don't know enough
>to answer this, and I'm too tired to think about it now. If the aswer to
>this is yes, than I think some serious modelling of the sail brake should
>be done immediately. Please could someone answer this for me as soon as
>poss.

No, either count the amount of photons, or use their frequency. Don't use
both particle and wave mechanics. (Rex, please tell me I'm right.)

Timothy