From: Mike Lorrey (mlorrey@datamann.com)
Date: Wed May 15 2002 - 10:19:22 MDT
spike66 wrote:
>
> Now realize that the average exhaust velocity of a rocket in m/sec
> is its Isp in newton seconds per kg. Further realize that you can
> accelerate particles to arbitrarily large velocities, given unlimited
> energy. The SLAC up the street here accelerates particles to
> velocities so high that relativistic mass increase is significant. So
> Isp can be made arbitrarily large. But of course for propulsion
> you need to carry the energy.
>
> If Isp is sufficiently high, the propulsion system is energy limited.
> If Isp is sufficiently low, it is mass limited. Right at the transition
> between mass limited and energy limited is the point of most
> efficiency for a given mission.
You speak wisdom, little grasshopper.
Of course, with relativity to play with, given enough energy, you have
practically infinite mass at your disposal.
I would posit that the instances of relativistic protons striking our
upper atmosphere with such high energies as to be unexplained by modern
cosmology are that they are the exhaust of starships, which dump immense
amounts of energy into individual particles on their long treks through
the universe. The fact that these particles striking our atmosphere is
so rare is indicative that we are a long way from the Qeng Ho trade
routes.
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