MISSION PRE-ENVIRONMENTAL REVIEW MASS PROPERTIES & SPIN BALANCE THEMIS MISSION PRE-ENVIRONMENTAL REVIEW MASS PROPERTIES & SPIN BALANCE David Pankow University of California – Berkeley

Thm-mint-proc-049 – draft 2 Released to GSFC & ManTech on 5/29 Themis PER: mass properties & spin balance TEST Specifications Thm-mint-proc-049 – draft 2 Released to GSFC & ManTech on 5/29 SAI-plan-0731 – Released ManTech-09PC-W158, Rev. 4 – Released SAI-TM-2873 – Spin Balance Predicts

TEST OBJECTIVES Themis PER: mass properties & spin balance Probe Static Balance: < 0.180” CG offset in X,Y plane (PB.mec-6) Probe Dynamic Balance: < 1 P.A. offset w.r.t. Geometric Z (PB.mec-7) Probes will be balanced with Mag Booms Stowed (like Wind, Polar, & Fast) MB Simulator masses will reflect the deployed boom CG & POI changes DCG ~ 0.16” • DP.A. ~ 0.5 MB Simulator - MOI’s and mass must be subtracted from measured data FM-MB masses and moments must be added using measured masses & coord’s. Probe Mass Properties (CG & MOI confirmation) Needed for Spin Stability Confirmation (PB.mec-5) & EFI SPB deployments Spin Stability (IS/IT) > 1.04 • Mass Tracking (IS/IT)  1.10 ±2% Transverse MOI measurement’s of One Probe is adequate

TEST SEQUENCE Themis PER: mass properties & spin balance First Probe Calibrate MPMF (Miller Table) and Measure Themis Fixture TARE’s First Probe Z (spin) Axis – Measure mass, X,Y CG, then XZ & YZ POI’s (by spinning) Compute and mount the needed balance masses Re-Measure mass, X,Y CG, then XZ & YZ POI’s (by spinning) Measure ZZ axis MOI X’, Y’ (lateral) Axes, where X’ is Tank CL’s horizontal, and Y’ is vertical Measure table plane CG and table rotation axis MOI Four Follow-on Probes Same as 1st Probe, except lateral axes are not needed “WET” PCA spin balance will be performed later at ASTROTECH

PROBE COORDINATES & BALANCE POINTS (SAI-PLAN-0731) Themis PER: mass properties & spin balance PROBE COORDINATES & BALANCE POINTS (SAI-PLAN-0731) +Y +X’ +Y’ +X

SPIN BALANCE TEST FIXTURES Themis PER: mass properties & spin balance Probe on MPMF (2 test attitudes) Probe Spin Adaptor Probe Turnover Fixture

Themis PER: mass properties & spin balance BACKUP SLIDES

Themis PER: mass properties & spin balance Anticipated SPIN (or Z) Axis PCA MOI Measurement Results Flight Probes (5 of 5 will be measured & balanced – CBE values here) 51.8 kgm2 ±1% = MPMF Measured Local Izz (5 probes) 259 kgm2 ±1% = Calculated Parallel Axis Contributions (S5 MR2, DR/R small) 311 kgm2 ±1% = Total Izz Contribution Probe Fuel 49.0 +0.5/-0.0 kg = Measured Mass (±0.1 kg each probe) 3.35 kgm2 ±4% = Calculated Local Izz (10 tanks - 98% full) 181 kgm2 ±1% = Calculated Parallel Axis Contributions (S5 MR2, DR/R small) 184 kgm2 ±1% = Total Izz Contribution Probe Carrier Assembly (< ± 10% needed for Star-48 yo-yo despin) 17.5 kgm2 ±10% = best Pro-E value for PC Local Izz 311 kgm2 ±1% = Probe Contribution (from above) 184 kgm2 ±1% = Fuel Contribution (from above) 513 kgm2 ±1% (RSS) or ±1.4% (worst case) = PCA TOTAL