1. STRATEGIES FOR MARS NETWORK MISSIONS VIA AN ALTERNATIVE ENTRY, DESCENT, AND LANDING ARCHITECTURE 10 TH INTERNATIONAL PLANETARY PROBE WORKSHOP 17-21 June, 2013; San Jose State University, CA, United States Sarag J. Saikia, Blake Rogers, James M. Longuski School of Aeronautics and Astronautics, Purdue University

2. MISSION CONCEPT AND ARCHITECTURE GOAL: Deliver four Mars Phoenix-class landers with a minimum separation of 3,000 km via a single launch from Earth

3. LAUNCH AND CRUISE CONFIGURATION  Payload mass of 60 kg (x4)  Flight system mass of 1380 kg + 2% reserve (x2)

4. SINGLE-EVENT DRAG MODULATION

5. BALLISTIC COEFFICIENT ANALYSIS

6. INTERPLANETARY TRAJECTORY TRAJECTORY CONSTRAINTS Atlas V 541 Launch Vehicle Maximum launch V ∞ for a mass of 1382 kg ≈ 7 km/s Maximum entry speed of 6 km/s Reduces the heating rates and heat loads of EDL Corresponds to a maximum arrival V∞ of ≈ 3.5 km/s

7. INTERPLANETARY TRAJECTORY 7 DAY SEPARATION: LOW THRUST Vehicle Number Launch Date (d/m/y) Arrival Date (d/m/y) Launch V∞ (km/s) Arrival V∞ (km/s) Onboard Propellant Required (kg) 17/29/20202/22/20213.822.540 27/29/20203/1/20213.821.6458.5 110/12/20226/22/20236.002.370 210/12/20228/20/20236.001.3963.1 14/12/203310/27/20332.993.370 24/12/203311/26/20332.992.5856.0

8. RANGE SEPARATION AND DIVERT CAPABILITY Global Reach Capability

9. MONTE CARLO RESULTS: RANGE SEPARATION LANDING ERROR Flight System 1 Flight System 2

10. STAGNATION-POINT HEATING RATE

11. DECELERATION, RELEASE

12. MONTE CARLO RESULTS SPACECRAFT RANGE AND RANGE SEPARATION DISTRIBUTION

13. MONTE CARLO RESULTS PRIMARY SPACECRAFT RANGE DISTRIBUTION

14. MONTE CARLO RESULTS INTEGRATED HEAT LOAD: PRIMARY SPACECRAFT

15. MONTE CARLO RESULTS INTEGRATED HEAT LOAD: SECONDARY SPACECRAFT

16. OTHER POTENTIAL APPLICATIONS Range Sep. [km] FPARelease Time [s] Secondary Landing Error 3-σ [km] Secondary Heat Load [J/cm 2 ] Stagnation Heat Rate [J/cm 2 ] Comment 1054-10.2°12260290028~ Phoenix 346-10.8°12215131028 140-10.8°1441242511TPS Needed? 706-10.0°14445200428 270-10.0°1641380613TPS Needed?  Primary heat load for all the cases is < 2200 J/cm 2  Primary landing 3-σ error for all the cases is < ±10 km

17. CONCLUSIONS  Low-Thrust Propulsion represents an attractive ‘augmentation’ for any future mission to Mars  Benign aerothermal environments, reduced heat rates and loads  Very low ballistic coefficient achievable: no supersonic decelerator (parachute) required  Increased risks of separation: flight systems, spacecraft from a flight system  Mass increase: due to extra spacecraft adapter; Decrease due to reduction in cruise stages and supersonic parachutes  Other potential applications of multiple spacecraft lander/orbiter missions  Single Atlas V 541 launch required  Incorporation of the guidance on the second will reduce the landing error

18. ACKNOWLEDGMENT Thanks to the IPPW10 student organizing committee for providing the ‘generous’ scholarship to attend the workshop

19. QUESTIONS?

20. BACKUP

21. Instruments Mass Breakdown  Payload mass of 60 kg (same as Phoenix mission)  Mass of flight system is 1380 kg + 2% reserve Mission Mass Breakdown Flight System 1 or 2 (Identical) Mass (kg) Additional Margins Lander 1 343 Lander 2 343 Backshell and Parachute 1 110 Backshell and Parachute 2 110 Ex.Heat Shield 1 124 Heat Shield 2 62 Cruise Stage 100 Propellant 1 65 Propellant 2 6540% Secondary Spacecraft Adapter and Release Mechanism 60 Total Mass 1382~30 kg

22. MONTE CARLO RESULTS INTEGRATED HEAT LOAD  % TPS mass is estimated using an empirical formula based on previous probe missions  Slightly high TPA mass for primary, and lower for secondary  Total range separation requirement is the determinant of % TPS mass of secondary  For low range requirements (<500km) secondary needs no TPS mass at all!

23. ANALYSIS OF DRAG MODULATION ParameterValue 70.0 kg/m 2 37.6 kg/m 2 20.5 kg/m 2 Combine with the previous slide #4

24. DRAG SKIRT OPTIONS Heat Shield Extension Rigid Deployable Decelerator (ADEPT) Hypersonic Inflatable Aerodynamic Decelerator (HIAD)

25. UNCERTAINTY ANALYSIS: MONTE CARLO SIMULATION UNCERTAINLY MODEL PARAMETERS AND INPUT ParameterDetails/ Models3σ3σComments No. of Runs1000- Density ModelMars-GRAM 2005Include Details Check Papers FPA0.003°Phoenix Velocity0.439 m/sPhoenix Altitude0 m Range0.002°Phoenix Ballistic coefficient 1 kg/m 2 Include dispersions in mass and Aerodynamic Coefficients Time of releaseTime Trigger1-2 seconds Correlated with Velocity Trigger