Mechanical System Design & the StarLight Project

1. Mechanical System Design & the StarLight Project Andy Jarski Mechanical Systems Engineer Ball Aerospace & Technologies

2. Overview • Brief Intro to Mechanical Design process • StarLight as an example • Some designs I’m working on • Conclusions

3. Quick Look at the Design Process • Identify the requirements • Mission • Launch Environments • Instrument / Payload Accommodations • Create Preliminary Configurations • Subsystem requirements (size, location, FOV) • Accessibility • Producibility • Structural Characteristics (load paths, stiffness) • Design Options • Materials (strength, stiffness, weight, CTE, corrosion resistance, cost, etc.) • General shape / layout • Validation of Requirements • Test Criteria • Design Criteria • Iterations • Until requirements are met • Detailed design goes to production

4. StarLight is the 1st of it’s Kind • Demonstrate 2 key technologies of particular importance for Terrestrial Planet Finder: • Autonomous Formation Flying • Separated-Spacecraft Interferometry • Mission uses 2 spacecraft, launched together which then separate to 600-1000m to simulate the performance of a single large telescope • JPL provides interferometer instruments and formation flying sensors • Ball provides 2 spacecraft, integration and test, and operations for the spacecraft • Heliocentric, earth trailing orbit to eliminate gravity field perturbations • Two spacecraft formation-flying to 2 cm accuracy • Low-jitter spacecraft to permit interferometer to lock on fringes

5. Black Magic of Interferometry

6. Formation Flying, in the Dark X 42º Starlight View Range 26º Half Cones of Shadow (all components are shaded) Collector Optics 52º Starlight View Range Collector S/C Intra Instrument Line of Sight Combiner S/C Combiner Instrument

7. Who’s Driving our Configuration? • Fit both spacecraft within the 3m, 3 stage, Delta II Fairing Envelope • Interface to the standard Delta 37” clamp band • Keep the CG within launch vehicle limitations • Accommodation of Interferometer instruments and Formation Flying Sensors • Provide unobstructed fields of view for • StarLight interferometer • intra-interferometer starlight link • Formation Flying sensors • Star Trackers • Antennas • Thrusters • Sun sensors • Solar arrays • Maintain CG balance after fuel depletion

8. Launch & Cruise Configurations Delta II 3m-3 Stage Fairing Combiner S/C 100” Collector S/C 37’’ Interface Ring Star 48B 3rd Stage Motor 108”

9. These Spacecraft are Nicely Equipped Interferometer Sun Sensors (x14) Low Impulse Cold Gas thrusters (x16) UHF antennas (Inter s/c comm) Solar Panel 106 in./270 cm dia. Deployable Sunshade 134 in./340 cm dia. High Accuracy Formation Flying Sensors Star Trackers (x2)

10. Modular Designs Reduce Risk • Modularity reduces I&T complexity and time required • Modularity improves accessibility • S/C bus components housed in Main Bus Assembly • Instrument is it’s own entity Interferometer Main Bus Assembly 2-Piece Solar Array Propulsion Module Formation Flying Sensor Module Hatch

11. Commonality is Important • StarLight uses nearly identical composite structures to • closely match the characteristics of the interferometer optical benches • minimize mass • Commonality helps to • Reduce I&T complexity • Reduce risk • Lower cost IMU X-Band Transponder Telecom “gear” Transceiver Propulsion “gear” Relay Box Reaction Wheels (x4) Battery Hatch Star Trackers (x2) SCU (Computer)

12. Structural Requirements • Minimum natural frequency of the launch stack • 15 Hz Lateral • 35 Hz Axial • 35 Hz Secondary • Applied to all components except the fixed sun shade • Max Axial Load: 9.5 g axial combined with 0.1 g lateral • Max Lateral Load: 2.8 g axial combined with 3.0 g lateral • Minimum factor of safety • Yield: 1.25 • Ultimate: 1.50 • Other requirements (acoustic, random, etc.) not expected to be critical • Alignments

13. StarLight FEM • Finite element models • of Launch Configuration for structural modes analysis • of separated s/c to analyze on-orbit disturbances Combiner Spacecraft Launch Configuration Collector Spacecraft

14. Modes Analysis 1st Axial Mode of 38 Hz 1st Lateral Mode of 15.3 Hz

15. Deployable is a Dangerous Word • Inter-Satellite Separation Mechanisms • Tolerance analysis • Separation dynamics • ABSOLUTELY MUST WORK! • Sunshade • Material selection crucial • RF transparent • Visibly opaque • Stiffness • ABSOLUTELY MUST WORK! Connector Separation Plane Separation Nut Separation Spring

16. Some Other Thoughts • Some basic engineering principles I think are important • When you start a design, just get something down on paper • If you leave something as a placeholder, document it as such and make sure to go back and fix it • Allocate lots of time for test, this is where everything comes together, and that is the point, isn’t it? • Test early, test often, test it again • Never compromise your ethics • If the design isn’t working, is behind schedule or over budget, say so, don’t mislead anyone, they may be able to help • If you see a problem, speak up • Getting involved is the best way to learn • Space Grant provided opportunities I couldn’t get anywhere else • Great exposure to industry • Opportunities you don’t always get in industry • Learning in a classroom is one thing, but applying your skills in a “real world” environment with real accountability and responsibility is where the challenge and fun are.

17. Questions?