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THEMIS MISSION PRE-ENVIRONMENTAL REVIEW MASS PROPERTIES & SPIN BALANCE David Pankow

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

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THEMIS MISSION PRE-ENVIRONMENTAL REVIEW MASS PROPERTIES & SPIN BALANCE David Pankow

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

  2. 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

  3. Themis PER: mass properties & spin balance • TEST OBJECTIVES • 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

  4. Themis PER: mass properties & spin balance • TEST SEQUENCE • 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

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

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

  7. Themis PER: mass properties & spin balance BACKUP SLIDES

  8. 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 (S5MR2, 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

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