Mechanical SuperNova/Acceleration Probe SNAP Study Dave Peters George Roach June 28, 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

SNAP Study, June 28, 2001 Goddard Space Flight Center Mechanical Page 2  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 Topics

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

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

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

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

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

SNAP Study, June 28, 2001 Goddard Space Flight Center Mechanical Page 10 Launch Vehicle Performance (Delta III)

SNAP Study, June 28, 2001 Goddard Space Flight Center Mechanical Page 11 Launch Vehicle Performance (Atlas III)

SNAP Study, June 28, 2001 Goddard Space Flight Center Mechanical Page 12 Launch Vehicle Performance (Sea Launch)