1. Dynamics and Control Attitude dynamics Communications Pointing
Chris Heidelberger
Dynamics and Control
Attitude dynamics
Communications Pointing
Thermal considerations

2. Attitude Dynamics
Assumptions: -circular orbit (will be changed) -translation not affected by orientation -axially symmetric body
Nominal motion is stable
Large 5 degree perturbation is still stable.
Without maneuver, near inertially fixed orientation throughout orbit.

3. Orientation
Assuming fully extended tether and no influence from Earth or Mars.
May want to wait a few days after Earth launch until deploying the tether.
Similarly, reel in tether a few days before Mars arrival

4. Communications Pointing
Need dish to “follow” Earth for high bandwidth antenna.
Will a motor be able to move fast enough and precisely enough?
Will there be any black out periods during transfer?
Will there be a need for a maneuver to maintain pointing?
Drawn by Chris Heidelberger

5. Setup of Problem
Orbital mechanics will tell us what W and w will be at any point in time. b now known.
Distance from Sun to Earth and spacecraft also known for any point in time.
Drawn by Chris Heidelberger

6. Setup, part 2
a, b, b, a, L known.
Can find c and e from law of cosines.
With e, can find z
z and a will add to f
Drawn by Chris Heidelberger

7. Setup, part 3 C, L, and f known. Use law of cosines to find Y and g.
g is the final answer needed.
Matlab code to find g as a function of time and range of g.
Drawn by Chris Heidelberger

8. Pointing during transfer
During 180 day transfer, no black out periods. During free return there doesn’t appear to be any, either (needs analysis).
There doesn’t appear to be large angles for pointing.
Further analysis needed after code is written.

9. Communications Conclusions
Dish size will determine max range of pointing angle. This will determine whether a maneuver will be needed to maintain pointing.
3-d motor needed to spin dish. Rate will be determined after analysis.
No black out periods during 180 day transfer.

10. Thermal Considerations
Use similar methods to find percentage of time each part of the vehicle is exposed to the Sun and at what angles.
This can be used to selectively place shielding and structures, lowering weight by not using full coverage when it isn’t needed. Sensitive objects can also be placed in low exposure areas.