Question

Find the ratio between circular orbit radii (outer to inner) beyond which it is more economical to use bielliptical transfers than the usual Hohmann tranfer between coplanar circular orbits.

Answer 1

1.Bielliptical transfers are more economical because ratio of final to initial semi-major axis is 11.94 or greater which is less than Hohmann transfer

2 Some Bielliptic transfers require lower amount of total delta-V than a Hohmann tranfer.

3.It takes less time than Hohmann for optimal alignment of departure and arrival of objects towards the transfer time.

4. Hohmann orbit leaves you at apogee with speed lower than the target by 'x'. Arrival from infinity or outside into a flyby trajectory leaves with speed higher than the target by 'y'. If the radii are much different, the difference between speed for Hohmann transfer and between escape is 'z1'. If you arrive from outside the system and want to choose altitude of your flyby then it is 'z2'.

5. Now if y+z1+z2<x, Bielliptic transfer takes less delta-V than Hohmann tranfer.