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Old 26th Jun 2009, 07:16
  #10 (permalink)  
james ozzie
 
Join Date: Dec 2004
Location: Brisbane
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Hmm, I think not...

I think many of the posts above are incorrect (now thats asking for it!)

Consider the basic physics for a rocket - not quite the same but still a reaction motor. It is well understood that a rocket can only attain its own exhaust velocity if its full-to-empty mass ratio is equal to or better than "e" (2.718...), efficiencies aside. But if better than "e", it can and will exceed its own exhaust velocity and in fact needs to, to escape earth. This basic relationship does not depend on whether there is air present or not, other than the fact that rocket motor efficiency is degraded by the presence of external air pressure acting against the nozzle - the basic physics still applies.

Perhaps people are forgetting that what happens to the exhaust gases after leaving the nozzle is irrelevant.

This misunderstanding is what caused eminent scientists (including the Royal Observatory Astronomer Royal, no less) in the 1930s/40s to declare "Space travel is impossible". So you are in good company.
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