Mechanical

1. SuperNova/Acceleration Probe SNAP Study Mechanical Dave Peters George Roach June 28, 2001 ...a man who's willing to make a decision in the first place can always make another one to correct any mistake he's made. Harry S. Truman

2. Topics • Launch Vehicle Volume Comparisons • Configurations • Launch • Deployed • Bus layout • Mechanical Mass, Cost, & TRL • Mass Properties • Issues and Concerns • Back-ups • Launch vehicle lift capacity comparisons SNAP Study, June 28, 2001 Goddard Space Flight Center

3. Launch Vehicle Volume Comparisons Delta III Atlas EPF SeaLaunch Delta II 6.57 M SNAP Study, June 28, 2001 Goddard Space Flight Center

4. Deployed Configuration Secondary Mirror and Mount Optical Bench Primary Mirror Solar Array Wrap around, body mounted 50% OSR & 50% Cells Thermal Radiator Sub-system electronics Detector/Camera Assembly Propulsion Tanks SNAP Study, June 28, 2001 Goddard Space Flight Center

5. Bus Layout Sub-system electronics Momentum Wheels (4 Ithaco “B”) Sub-system electronics 5# thrusters (4 sets of 2) Propulsion Tanks FIDO electronics • Points to consider • Mass balance • Thermal • Access for servicing propulsion tanks • Integration and test access Sub-system electronics SNAP Study, June 28, 2001 Goddard Space Flight Center

6. Mechanical Mass, Cost, & TRL(composite structure assumed) • Mass (kg) • Bus Structure • Thrust tube 33 (can be lower - not structural) • Plates 31 • Misc. brackets, clips, etc. 79 143 total • TRL #6 : System/subsystem model or prototype demonstration in a relevant environment (ground or space) • Subsystem prototypes or models of the proposed bus have been successfully tested under space conditions in orbital flight, but in a bus configuration different than the proposed bus. • Bus prototypes or models will require major modifications for proposed mission. This will require flight requalification. • Proven launch vehicle to be used. SNAP Study, June 28, 2001 Goddard Space Flight Center

7. Mass Properties Z • Spacecraft • Lift-off • C.G………………… 23.4, -126.3, 1186.0 (mm) • Inertia’s wrt C.G. • Ixx ……………… 3.6e9 • Iyy ……………… 3.3e9 • Izz ……………… 2.1e9 Y X SNAP Study, June 28, 2001 Goddard Space Flight Center

8. Mechanical Issues and Concerns • RSDO Spacecraft Bus • There are several “RSDO” buses that could accommodate this mission. However, due to the unique payload instrument interface, extensive re-design of the mechanical structure is necessary. A mission unique structure will be mandatory. At this time we feel that there will be sufficient volume to accommodate the sub-system components. The main concern being the reaction wheels and their relationship to the C.G. • Mass and Volume • No mass problem • Volume is close on the Delta III and Atlas EPF. • This volume conflict is very slight and could be resolved by a slight reduction of the MLI Shroud Assembly • Mechanical interfaces • Mission axial C.G. height within limits for launch vehicle PAF. • Mission lateral C.G. are within limits for launch vehicle PAF. • Mission stiffness for launch vehicle is TBD at this phase of the study. SNAP Study, June 28, 2001 Goddard Space Flight Center

9. BACK-UP Slides SNAP Study, June 28, 2001 Goddard Space Flight Center

10. Launch Vehicle Performance(Delta III) 2700 -2 SNAP Study, June 28, 2001 Goddard Space Flight Center

11. Launch Vehicle Performance(Atlas III) 3100 -2 SNAP Study, June 28, 2001 Goddard Space Flight Center

12. Launch Vehicle Performance(Sea Launch) 3300 -2 SNAP Study, June 28, 2001 Goddard Space Flight Center