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Re: Engineering Newsletter

Kevin C. Houston writes:
 > To: all nitpickers
 > From: A nit(wit) who is tired of getting picked on.  ;)

Sorry, but conservation of energy and momentum are too
fundamental to ignore.  If you can't follow those rules then you
may as well give up and design a warp drive, since you're
throwing out the laws of physics anyway.

 > see my web page
 > http://www.umn.edu/nlhome/m056/hous0042/asimov.html
 > for an idea that is consistant with Steve and Timothy's objections.
 > i.e. reflection transferrs momentum to the normal, and absorbtion 
 > transfers momentum in the direction of the photons original vector.
 > Advance billing: it is _still_ possible to cancel the momentum within the 
 > structure of the antenna/sail .
 > HA!

We'll see.  You must either absorb the photon and thereby absorb
its momentum, or reflect the photon and get momentum to balance
the change in direction of the photon.  The only way to not get
any momentum change is to either not interact with the photon or
reflect it so as to leave it travelling in the same direction it
came with the same energy.

If the system consisting of the photon beam and the spaceship
plus sail assembly doesn't have the same momentum after the
interaction as before, then you'll have to go back to the drawing
board.  Perhaps after a brief refresher course in physics.