Summary of the results of the LISA-Pathfinder Test Mass release Carlo Zanoni1 1 D. Bortoluzzi , J.W. Conklin2 , I. Koeker3 , B. Seutchat1 , S. Vitale1 1 University of Trento and INFN (Italy) of Florida (USA) 3 Airbus Defence and Space (Germany) 2 University Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 1 / 13 Outline Content Validation of the Release Mechanism performance (= minimize TM velocity) by means of analytical and experimental studies on the main phenomena. 1 Intro to Caging and Release Operations 2 Mechanism Physical Model 3 Adhesion Contribution to Final Velocity 4 Simulations and Results 5 What’s next? 6 Conclusion Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 2 / 13 Intro to Caging and Release Operations Caging Mechanism CVM: Caging and Vent Mechanism. 1200 N load during launch. GPRM: Grabbing, Positioning and Release Mechanism. First centering and alignment. Carlo Zanoni, UniTN and INFN 22 May 2014 RT: Release Tip. Small contact area, high retraction quickness (40 mm/s). Gold alloy. LISA Symposium X 3 / 13 Intro to Caging and Release Operations Caging Mechanism CVM: Caging and Vent Mechanism. 1200 N load during launch. GPRM: Grabbing, Positioning and Release Mechanism. First centering and alignment. Carlo Zanoni, UniTN and INFN 22 May 2014 RT: Release Tip. Small contact area, high retraction quickness (40 mm/s). Gold alloy. LISA Symposium X 3 / 13 Intro to Caging and Release Operations Caging Mechanism CVM: Caging and Vent Mechanism. 1200 N load during launch. GPRM: Grabbing, Positioning and Release Mechanism. First centering and alignment. Carlo Zanoni, UniTN and INFN 22 May 2014 RT: Release Tip. Small contact area, high retraction quickness (40 mm/s). Gold alloy. LISA Symposium X 3 / 13 Intro to Caging and Release Operations Release Procedure [Acrobat Reader needed for the video] Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 4 / 13 Intro to Caging and Release Operations Requirement and main issues linear velocity < 5 µm/s (mission critical) Approach requirements on other states/axes: demanding, but less challenging every asymmetry determines momentum transfer to the TM: adhesion: limited repeatability mechanism actions (e.g. delay) Carlo Zanoni, UniTN and INFN 22 May 2014 Collect information on asymmetry sources. Extrapolate on ground data to in-flight conditions. Estimate the TM velocity after release. LISA Symposium X 5 / 13 Intro to Caging and Release Operations Requirement and main issues linear velocity < 5 µm/s (mission critical) Approach requirements on other states/axes: demanding, but less challenging every asymmetry determines momentum transfer to the TM: adhesion: limited repeatability mechanism actions (e.g. delay) Carlo Zanoni, UniTN and INFN 22 May 2014 Collect information on asymmetry sources. Extrapolate on ground data to in-flight conditions. Estimate the TM velocity after release. LISA Symposium X 5 / 13 Intro to Caging and Release Operations Requirement and main issues linear velocity < 5 µm/s (mission critical) Approach requirements on other states/axes: demanding, but less challenging every asymmetry determines momentum transfer to the TM: adhesion: limited repeatability mechanism actions (e.g. delay) Carlo Zanoni, UniTN and INFN 22 May 2014 Collect information on asymmetry sources. Extrapolate on ground data to in-flight conditions. Estimate the TM velocity after release. LISA Symposium X 5 / 13 Intro to Caging and Release Operations Requirement and main issues linear velocity < 5 µm/s (mission critical) Approach requirements on other states/axes: demanding, but less challenging every asymmetry determines momentum transfer to the TM: adhesion: limited repeatability mechanism actions (e.g. delay) Carlo Zanoni, UniTN and INFN 22 May 2014 Collect information on asymmetry sources. Extrapolate on ground data to in-flight conditions. Estimate the TM velocity after release. LISA Symposium X 5 / 13 Intro to Caging and Release Operations Requirement and main issues linear velocity < 5 µm/s (mission critical) Approach requirements on other states/axes: demanding, but less challenging every asymmetry determines momentum transfer to the TM: adhesion: limited repeatability mechanism actions (e.g. delay) Carlo Zanoni, UniTN and INFN 22 May 2014 Collect information on asymmetry sources. Extrapolate on ground data to in-flight conditions. Estimate the TM velocity after release. LISA Symposium X 5 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Mechanism Physical Model Release Tip model & Identification RT model required because of mechanism-adhesion mutual interaction RT moved by a piezo-stack preloaded by washer springs. lumped-element model. 10 parameters, no hysteresis. identified with unloaded retractions of the FMs. nominal input: 120 V step. improvement of previous versions1 . 1 D. Bortoluzzi, J.W. Conklin, and C. Zanoni, Prediction of the LISA Pathfinder release mechanism in-flight performance, Advances in Space Research, 2013. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 6 / 13 Adhesion Contribution to Final Velocity Adhesion: experimental facility limited repeatability. worst-case: adhesion acts on one TM side only. experimental facility to study dynamic adhesion: pendulum in space-like environm. (10−7 mbar) representative surfaces Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 7 / 13 Adhesion Contribution to Final Velocity Adhesion: measurements TM motion measured by a SIOS interferometer Tip motion measured with DOSS sensor Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 8 / 13 Adhesion Contribution to Final Velocity Adhesion: results Rough Extrapolation: Fine Extrapolation (Fit): F (∆) = X1 ∆l e−∆l/X2 peak force < 50 mN. peak duration ∼ 1 ms. flight mechanism speed 10× ground actuator. extrap. impulse <50% req. Carlo Zanoni, UniTN and INFN 22 May 2014 fit the acceleration time profile simulation requires analytical expression. LISA Symposium X 9 / 13 Simulations and Results Montecarlo Simulation Randomization of: mechanism parameters (identification). contact geometries (design tolerances). input voltage time profile (measurements). adhesion (experimental campaigns). 99.73 % worst case velocity: 1.50 µm/s Adhesion contribution: 1.36 µm/s Mechanism contributions: 0.24 µm/s Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 10 / 13 Simulations and Results Numerical analysis of contact (preliminary) Motivation: validation of experimental data (avoid underestimation) estimation of compression behavior (used Hertz, so far) F (∆l) in rough contact sum of forces computed with JKR/DMT/ductile models for single asperity local plasticity hard to model Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 11 / 13 What’s next? What’s next? GPRM testing: LISA-Pathfinder → eLISA optimization example (radius) worst-case momentum: ∝ contact depth (push time) ∝ contact area (adhesion strength) further margin possible maximize representativeness. learn GPRM functioning for mission support. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 12 / 13 What’s next? What’s next? GPRM testing: LISA-Pathfinder → eLISA optimization example (radius) worst-case momentum: ∝ contact depth (push time) ∝ contact area (adhesion strength) further margin possible maximize representativeness. learn GPRM functioning for mission support. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 12 / 13 What’s next? What’s next? GPRM testing: LISA-Pathfinder → eLISA optimization example (radius) worst-case momentum: ∝ contact depth (push time) ∝ contact area (adhesion strength) further margin possible maximize representativeness. learn GPRM functioning for mission support. Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 12 / 13 Conclusion Conclusion validation activity of requirement for the TM release. experimental assessment of the most important phenomena. modeling and Montecarlo simulation of the release. estimated worst-case velocity compliant with the requirement. (but not 100% representativeness). direct testing with GPRM to be started in June (this year). Contacts: carlo.zanoni@unitn.it daniele.bortoluzzi@unitn.it Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 13 / 13 Conclusion Conclusion validation activity of requirement for the TM release. experimental assessment of the most important phenomena. modeling and Montecarlo simulation of the release. estimated worst-case velocity compliant with the requirement. (but not 100% representativeness). direct testing with GPRM to be started in June (this year). Contacts: carlo.zanoni@unitn.it daniele.bortoluzzi@unitn.it Carlo Zanoni, UniTN and INFN 22 May 2014 LISA Symposium X 13 / 13 Full Requirement State offset linear velocity angle angular rate Carlo Zanoni, UniTN and INFN Value ± 200 µm ± 5 µm/s ± 2 mrad ± 100 µrad/s 22 May 2014 LISA Symposium X 1/3