ASEN 5519: Interplanetary Mission Design

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ASEN 5519: Interplanetary Mission Design

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1. ASEN 5519: Interplanetary Mission Design Monday, September 25th, 2006 Jeffrey S. Parker

2. Lecture Overview Pork Chop Plots Launch Windows Launch Parameters B-Plane Targeting Planetary Quarantine Requirements Mars Odyssey Example Spacecraft observations and Orbit Determination Using the B-Plane to Target a Planetary Arrival Next Week: B-Plane Targeting applied to Gravity Flybys

3. Interplanetary Mission Design Why do we go? Science, Exploration, Survival What is the cost? Launch energy Excess arrival energy Time of transfer Planetary Quarantine concerns How do we get there? Launch Optional: Gravity Assists Optional: Resonant Orbits Optional: Deep Space Maneuvers Optional: Low-thrust Choose an itinerary that optimizes cost vs. benefit!

4. Terminology Quick review of terminology: C3: Launch Energy (km2/s2) V8: Hyberbolic excess velocity (km/s). It is the velocity you have arriving/departing a planet’s sphere of influence (SOI) w.r.t. the planet. V8 = VS/C – VPlanet V8in: The excess velocity when arriving at a planet. V8out: The excess velocity when departing from a planet.

5. Lambert’s Problem Formulation of Lambert’s Problem: Given: t0, R0, tf, Rf Find: V0, Vf Basic limitations: 2-body equations of motion Practical Implementation: Determines an approximate ?V budget for Planet A – Planet B transfers for many different dates. Pork Chop Plots

6. Application of Lambert’s Problem Trajectories that all depart the Earth at the same date, but arrive at Mars at different dates

7. Application of Lambert’s Problem More Mars arrival dates Remember: Earth and Mars are not coplanar! Real Hohmann transfers rarely exist

8. Application of Lambert’s Problem More Mars arrival dates Type II Trajectories

9. Application of Lambert’s Problem Summarizing the results Departure date constant Arrival date variable

10. Varying Departure Dates Now, let us allow the Earth-Departure time to vary

11. Pork Chop Plots (PCP’s) Add full trade-space of departure/arrival dates Building-block of basic interplanetary mission design Example shown is a PCP for Earth-Mars in 2005.

12. Pork Chop Plots (PCP’s)

13. Pork Chop Plots (PCP’s)

14. Resulting Trajectories

15. What happens if we miss our launch date?

16. Pork Chop Plots (PCP’s)

17. Distant Planets A single Pork Chop Plot analysis will generally be sufficient for a mission to a local planet. For distant planets, it is usually desirable to swing by nearby planets enroute to the distant planet to save energy. Implications: Produce a PCP for each segment in the itinerary!

18. Review: The Hyperbola

19. Hyperbola Toolbox (See Handout on Website)

20. Launch Parameters

21. Launching from Earth Earth’s pole is tilted with respect to the ecliptic. This obliquity angle is approximately 23.45° Additionally, launch vehicles have a limited available azimuth-range.

22. Definition of the B-Plane

23. B-Plane Toolbox (Handout on Web)

24. B-Plane Targeting Advantage of B-Plane targeting: well-linearized system! Example: constructing a TCM enroute to Mars

25. Planetary Quarantine Requirements Planetary Quarantine Requirements (PQRs) enforce that a spacecraft shall have a “very low” chance of impacting a planet if at any time during its mission all of its propulsion capabilities fail. Especially important in the cases of Venus, Earth, Mars, Europa, and various other moons in the solar system. In some cases, that means there has to be a 99% chance of missing the planet at any time during a trajectory leg. In other cases, e.g., Cassini flying over Earth carrying radioactive materials, the chances of miss must be better than 99.9999% (literally).

26. On to the Mars Odyssey Example! (Click here to directly link)

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