DESIGN OF LOW-THRUST TRANSFER ORBIT TO EARTH-MOON LAGRANGE ORBIT VIA ELECTRIC DELTA-V LUNAR GRAVITY ASSIST

The International Space Exploration Coordination Group, ISECG addresses the use of a cislunar habitat for future space exploration such as Lunar and Mars exploration. For the transportation to the cislunar, there three types of transfer options: 1) in-direct transfer via Powered Lunar swing-by, 2) Weak Stability Boundary Transfer in which Solar gravity perturbation is utilized, and 3) low-thrust orbit raising to Lunar orbit. The in-direct transfer requires roughly 500 m/s order of delta-V however the Time-of-Flight, TOF from Earth to Cislunar is practically short i.e., roughly 5 similar to 7 days. This type of transfer is assumed for human transportations. The WSB transfer will significantly decrease the required delta-V, however the TOF will be 2 similar to 6 months and it will largely change depending on the launch epoch. The low-thrust orbit raising will increase the payload mass, however it will take 6 similar to 12 months to get to the destination. Considering such situation, this paper focuses on a new type of low-thrust transfer option which fulfils the significant gap between the two transfer methods. The proposed method is called Electric Delta-V Lunar Gravity Assist, EDV-LGA. The use of electric propulsion will reduce the fuel mass for the transfer, besides the TOF of EDV-LGA is roughly 1 month which is almost equivalent to the life-support capability of Orion. As another merit of the low-thrust transfer, the author thinks it may also increase the safety of human transportation to the habitat. If some trouble occurs at the impulsive delta-V in the in-direct transfer, the maimed space ship may not be able to come back to the Earth within the duration of a life support system. However, the low-thrust transfer is relatively easily restored from such kinds of troubles. These characteristics of the proposed transfer method will provide a new transfer option for future deep-space habitat.