ABSTRACT
In a conventional rocket using chemical fuel the velocity of the exhaust gas is constant relative to the rocket. Consider instead a 'perfect rocket' in which the exhaust velocity u at any time is equal to the initial exhaust velocity U0 plus the current velocity v of the rocket; i.e. u = U0 + v. Thus viewed from the initial rest frame of the rocket the exhaust gases have the same velocity throughout the flight (Fig 80).
