Orbit 1 has angular momentum h and eccentricity e. The direction of motion is shown. Calculate the Δv required to rotate the orbit 90° about its latus rectum BC without changing h and e. The required direction of motion in orbit 2 is shown.
By symmetry, the required maneuver may occur at either B or C, and it involves a rigid body rotation of the ellipse, so that vr and v⊥ remain unaltered. Because of the directions of motion shown, the true anomalies of B on the two orbits are
θB)1=−90∘θB)2=+90∘The radial coordinate of B is
rB=μh21+ecos(±90)1=μh2For the velocity components at B, we have
Substituting these into Eqn (6.19), yields
Δv=(vr2−vr1)2+v⊥12+v⊥22−2v⊥1v⊥2cosδ (6.19)
so that
ΔvB=h2μ1+2e2 (a)
If the motion on ellipse 2 were opposite to that shown in Figure 6.34, then the radial velocity components at B (and C) would in the same rather than in the opposite direction on both ellipses, so that instead of Eqn (a) we would find a smaller velocity increment,
ΔvB=h2μ