1. STUDIES ON THE UTILIZATION OF SOLAR SAIL IN LUNAR-TRANSFER TRAJECTORY Zhao Yuhui 1,2, Liu Lin 1,2 1. Astronomy Department, Nanjing University, Nanjing, 210093,China 2. Institute of Space Environment and Astrodynamics, Nanjing University, Nanjing, 210093, China

2. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Outline I. Primary Trajectory II. The orbit under real ‘dynamical model’ III. The acceleration due to light pressure IV. Numerical simulations and results V. Conclusions

3. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Introduction

4. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Introduction

5. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Introduction Hohmann transfer: shorter transfer time, larger fuel consumption Use the instability of : energy- saving, long time consumption Reasonable use of light pressure: this paper studies

6. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University The force due to light pressure surface pressure: relative to the mass area ration conservative central repulsive force: It doesn’t accelerate or decelerate moving bodies continuously. Therefore, the normal direction of the solar sail usually point in a particular direction in order to use light pressure to guide a probe and save energy consumption. Introduction

7. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Earth gravity filed Lunar gravity field Earth parking orbit H ＝ 200km T ＝ 12h T ＝ 24h T ＝ 48h Transfer orbit The edge of Moon gravity field co-two body problem

8. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Primary Trajectory Co-tow Body Problem (Hohmann Transfer) Earth parking orbit: 200km-height circular orbit T=12 hour orbit T=24 hour orbit T=48 hour orbit Transfer orbit: from earth parking orbit to the 300km high point above north pole of the moon Orbit around moon: 300km×200km lunar polar orbit we consider the two primaries separately, central gravitations in each gravitational field are: is used to calculate the accelerations.

9. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University The kinematical equations are: Earth’s central gravity acceleration: Lunar central gravity acceleration: The acceleration due to : Solar gravity perturbing acceleration: The orbit under ‘real dynamical model’

10. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Acceleration due to light pressure: Generally this doesn’t accelerate or decelerate a probe continuously in space exploration. Continuously accelerating: When the normal direction of the solar sail is along the bisector between the direction of the probe from the sun and the direction of motion of the probe The acceleration due to light pressure

11. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Acceleration due to light pressure: The acceleration due to light pressure

12. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University five simulation models: 1) hohmann transfer orbits when the sun and the moon are on two sides of the earth 2) takes the light pressure into account on the basis of 1) 3) hohmann transfer orbits when the sun and the moon are on the same side of the earth 4) takes the light pressure into account on the basis of 3) 5) a transfer orbit ‘only’ guided by light pressure Numerical Simulations

13. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University trajectory: Model 1)-4) (4 times impulse) 200km-height circular orbit GT0 orbit GEO orbit transfer orbit 300km×200km lunar polar orbit Model 5) (4 times impulse) 200km-height circular orbit GT0 orbit apogee=100,000km transfer orbit 300km×200km lunar polar orbit Numerical Simulations By light pressure only

14. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Initial conditions: Choose the time that the position of the sun and the moon meets the above requirements during March 2007 as the launch time, and the normal direction of the solar sail in model 2),4),5) points the particular direction given above to accelerate the probes continuously. Suppose of the earth’s It’s about Numerical Simulations

15. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Results: Numerical Simulations

16. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Analysis: 1),2)and 3),4): The relative position of the 3 bodies have effects on the acceleration due to light pressure and energy-saving. 2),4),5): The effect of light pressure used in a hohmann transfer is not obvious because of the short transfer time while a reasonable use will achieve energy saving along with a not very long transfer time. Numerical Simulations

17. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University Conclusions Acceleration due to light pressure is effected by the relative position of the moon and the sun, and has a slight effect in hohmann transfer orbit. However, if light pressure is reasonably used, energy saving could be actually realized with not too much time consumption by adjusting the solar sail’s normal direction to point a particular direction. This kind of orbits has applications and perspective in deep space exploration, it’s an alternative ‘propellant’ to guide a deep space detector

18. 南京大学空间环境与航天动力学研究所 Institute of Space Environment and Astronautics, Nanjing University