Here is the problem. A rocket of mass m is in a circular orbit around the Earth at a distance R from the center. (a) What tangential impulse, mΔv, must be given to the body so that it just escapes to infinity? My attempt: I set the problem in terms of energy, E=1/2m((dr/dt)^2+r^2(dø/dt)^2) V(r) and using conservation of angular momentum I get dr/dt=[2mMG/r-(l/mr)^2]^1/2, where l=mr^2dø/dt. Am I missing something? Thank you.