Autonomous Formation Flying and Proximity Operations using Differential Drag on the Mars Atmosphere

Transcription

1 Autonomous Formation Flying and Proximity Operations using Differential Drag on the Mars Atmosphere Andrés E. Villa M.S. in Aerospace Engineering candidate California Polytechnic State University May 5 th, 2016

2 Agenda Introduction Mars facts Literature review Methods Results Pending work Conclusions 2

3 Introduction Motivation Why Mars? Why aerodynamic drag? Why formation flying? Why autonomous? 3

4 Introduction Feasibility Analysis A feasibility analysis was conducted showing that differential drag can be applied in Low Mars Orbits of 220 kilometers in altitude (maximum) Two different areas exposed to drag were simulated, obtaining enough drag to be used as means of control A paper was written and will be published 4

5 5 Acceleration due to atmospheric drag when the biggest area faces the Ram direction

6 6 Acceleration due to atmospheric drag when the smallest area faces the Ram direction

7 Introduction Purpose of the Study Use existing differential drag techniques Same as for Earth, but for Mars atmosphere Minimize the fuel used Cost reduction Finite resource Contamination / distortion 7

8 Introduction Research Questions Is it possible to use the same formulation as for Earth atmosphere? How different is the Martian atmosphere with respect to Earth? Is the Martian atmosphere enough dense to perform formation flying around it? How much time will be needed to constitute a formation? 8

9 Introduction Significance to the Field Mars aerobraking techniques already exist and have been proven to work, but No previous work has been done to demonstrate that formation flying is possible Means of control in finite time Requirements Limitations 9

10 Introduction Definitions Chief, Leader, Target Deputy, Follower, Chaser Ephemeris Time Data kernel Aberration due to communication delay 10

11 Introduction Limitations In-track maneuvers only No Solar Radiation Pressure was considered for Mars Each spacecraft has to know the navigation information of the other spacecraft involved GPS-like navigation system Inter-spacecraft communication system 11

12 Mars facts (compared to Earth) Parameter Earth Mars Mean radius 6378 kilometers kilometers Tilt of axis 23.5 degrees 25 degrees J2 harmonics (55% greater than on Earth) Solar irradiance 1378 kw/m kw/m 2 Length of day 23 hours 56 minutes 24 hours 37 minutes Length of year days 687 Earth days Atmosphere Nitrogen, Oxygen, Argon, others Mostly carbon dioxide, H20 vapor 12

13 Literature Review Extensive review conducted More than 15 papers are relevant to the field Differential drag Flight dynamics with linearized J2 perturbations Control techniques Autonomy requirements Only a couple are specific for Mars Multi-spacecraft navigation Mars atmosphere 13

14 Methods Introduction Two Mars atmospheric models available NASA s Mars-GRAM ESA s Mars Climate Database (MCD) Simulation using MATLAB Wrapper to access MCD FORTRAN routines for atmospheric models Wrapper to use Navigation and Ancillary Information Facility (NAIF) to store information 14

15 Methods Setting Two 6U CubeSat flying in a co-planar circular orbit at 220 kilometers Use of Schweighart-Sedwick equations Including linearized J2 perturbations Used to describe relative motion Optimal control being implemented Cost function such to minimize rendezvous time 15

16 Schweighart and Sedwick equations Satellite Motion Relative to a Second Satellite x = x 0 cos nt 1 s + 1 s s y 0 sin nt 1 s y = s 1 s x 0 sin nt 1 s + y 0 cos nt 1 s z = lt + m sin qt + φ s = 3J 2R e 2 8r ref cos 2i ref 16

17 Results As suggested in literature, integration time of 3 minutes can be used Preliminary results have been obtained to demonstrate feasibility of using same techniques on Mars atmosphere Analyzing theory of Lossless Convexification and Linear Programming methods 17

18 Pending work Finish implementing the optimal control Code fails to run. Now debugging. Finish writing the report Results of optimal control Comparison with Lossless Convexification Comparison with Linear Programming Writing conclusions Finish presentation for defense 18

19 Conclusions (as for now) Earth Formation flying techniques can be applied to Mars, where optimal control is desirable to minimize the time required to rendezvous Availability of Mars atmospheric models allows to implement high fidelity simulations Mars atmosphere is dense enough to perform formation flying missions 19

20 Questions?