Before Apollo 8, the Soviets were planning a lunar flyby mission with a cut-down Soyuz spacecraft launched by a Proton booster. More recently the Russians have spoken seriously about a lunar flyby tourism mission in a Soyuz at the price of around $100 million per seat.<br /><br />http://www.astronautix.com/craft/soyz7kl1.htm<br /><br />http://www.astronautix.com/craft/dsealpha.htm<br /><br />Now unlike the Apollo 8 mission which braked into orbit around the moon, the Russian circumlunar missions would just swing-by the moon and head back towards Earth on a free-return trajectory. Ordinarily the Soyuz descent-capsule would do a skip-reentry at Earth arrival. <br /><br />But what if the Soyuz spacecraft didn't aim for Earth return? What if the spacecraft was aimed to swing-by the Earth and head back out again? Could the orbit be adjusted so it would swing out again towards the moon? Could such an orbit be adjusted so that the spacecraft would swing back and forth between the Earth and the moon in a perpetural figure 8 orbit? How stable could such an orbit be? And if unstable how much Delta-V would such an orbit require to maintain?<br /><br />Anyone know the answers to these questions? Please help.