ash / amuchastegui - august 1970 - subroutine chncnc
initial set-up for conic section motion from position and velocity
revised sept 1971 for use in pep
optimized 1977 jan  j.f.chandler

goose       = input value of square root of gravitational constant
times mass of central body. units are l**3/2*(t**-1)
x(1-6)      = input cartesian coordinates
cond(1) = a    = semi-major axis
cond(2) = e    = eccentricity
cond(3) = inc  = inclination
cond(4) = asc  = right ascension of ascending node
cond(5) = per  = argument of perigee
cond(6) = anom = initial mean anomaly