A space vehicle approaching a planet has a speed v, very long way out and is on a trajectory which would miss the centre of the planet by a distance R if it continued in a straight line. If the planet has a mass M and radius r, what is the smallest value of R in order that the resulting orbit will just miss the surface:
(1) R=r2GMv
(2) R=vr[1+r2GM]
(3) R=vr[v2+r2GM]
(4) R=vr[v2+r2GM]1/2