THEMIS MIWG #3Probe Separation Analysis - Page 1June 15 & Probe Separation Analysis Daniel Rummel UCB THEMIS MIWG #3Probe Separation Analysis - Page 2June 15 & Overview Linear Separation Analysis 3D Re-Contact Analysis Early Attitude Maneuvers Long-Term Monte Carlo Simulation THEMIS MIWG #3Probe Separation Analysis - Page 3June 15 & Linear Separation Analysis Separation Events Summary 3rd Stage Burn Out Probes B-E Release Probe A Release 3rd Stage Chuffing THEMIS MIWG #3Probe Separation Analysis - Page 4June 15 & Linear Separation Analysis Probe A to 3rd Stage Separation (Springs) Using mass properties and the details of the separation system, a nominal and low separation velocity can be calculated between Probe A and the Launch Vehicle. (LV = Star 48 3rd Stage + Probe Carrier) THEMIS MIWG #3Probe Separation Analysis - Page 5June 15 & Linear Separation Analysis Residual Thrust Error Sources Four 3sigma Error Sources contribute to velocity imparted by residual thrust: Mass of 3rd Stage Probe A Separation time 3rd Stage Burn time Residual Thrust in 3rd stage (initial thrust & decay rate define the thrust curve) THEMIS MIWG #3Probe Separation Analysis - Page 6June 15 & Linear Separation Analysis Residual Thrust Integration Results Velocity Imparted by 3rd Stage Chuffing: Nominal + 3sigma Velocity = THEMIS MIWG #3Probe Separation Analysis - Page 7June 15 & Linear Separation Analysis Results/Margins Nominal margins remain high. 3sigma margins remain positive. Subtracting the residual thrust velocity from the spring separation system velocity yields separation margins. THEMIS MIWG #3Probe Separation Analysis - Page 8June 15 & D Re-Contact Analysis Summary 3D Re-Contact Analysis Utilized GTDS using the full high-fidelity force model for 3D orbit propagation. Short-term analysis at 1 sec. resolution for the first 20min after release. Long-term analysis at 1 min. resolution for 7 days. THEMIS MIWG #3Probe Separation Analysis - Page 9June 15 & D Re-Contact Analysis Short-term Results: Probe A Nominal Separation 3Sigma Low Separation Nominal Separation Probe A obtains ~900m in first 20 min. In 3sigma case Probe A still maintains ~100m after first 20 min. THEMIS MIWG #3Probe Separation Analysis - Page 10June 15 & D Re-Contact Analysis Short-term Results: Probes B-E Nominal Separation 3Sigma Low Separation Nominal Separation Probes B-E obtain ~2000m in first 20 min. As expected residual thrust has little effect on Probes B-E. THEMIS MIWG #3Probe Separation Analysis - Page 11June 15 & D Re-Contact Analysis Long-term: Probe A to LV Nominal Separation +3Sigma Separation General trend: A Linear increase in separation at each successive orbit node. Nominal separation yields ~170km at the first node. THEMIS MIWG #3Probe Separation Analysis - Page 12June 15 & D Re-Contact Analysis Long-term: Probe A to LV - Close Up +3Sigma Separation Close Up General trend: Linear increase in separation at each successive orbit node. Nominal separation yields ~170km at the first node. +3Sigma Separation yields ~15km at the first node. THEMIS MIWG #3Probe Separation Analysis - Page 13June 15 & Early Attitude Maneuvers Early Attitude Maneuvers and the Imparted dV Within ~14hours after release the probes will need to be placed in a power positive attitude. (From the LV attitude to any sun normal attitude). Modeling these maneuvers in GMAN indicates that they impart ~1 m/s of dV partially in the direction of separation and out of release formation. Residual dV Reorientation THEMIS MIWG #3Probe Separation Analysis - Page 14June 15 & Early Attitude Maneuvers Early Attitude Maneuver Sequence Spacing these maneuvers out over ~8 hours can aid in probe separation. A E Early Attitude Maneuver Sequence D C B Probe Release (*Night 3 is a lunar shadow.) THEMIS MIWG #3Probe Separation Analysis - Page 15June 15 & Early Attitude Maneuvers Probe A-> LV Nominal Release w/ Early Attitude Maneuvers Nominal release shows benefit of ~50km after the first 20 hours. THEMIS MIWG #3Probe Separation Analysis - Page 16June 15 & Early Attitude Maneuvers Probe A-> LV 3sigma Release w/ Early Attitude Maneuvers 3sigma release shows benefit of ~45km after the first 20 hours. THEMIS MIWG #3Probe Separation Analysis - Page 17June 15 & Early Attitude Maneuvers ProbeA -> ProbeB separation w/ Early Attitude Maneuvers Probe A Release+9hours Probe B Release+13Hours The green line indicates additional separation due to the attitude maneuvers. THEMIS MIWG #3Probe Separation Analysis - Page 18June 15 & Early Attitude Maneuvers Probe A->Probe B Long-term Sep. w/ Early Attitude Maneuvers Probe A Release+9hours Probe B Release+13Hours Long-term separation continues. Trends are similar for all other probes. THEMIS MIWG #3Probe Separation Analysis - Page 19June 15 & Monte Carlo Simulation Random Dispersion of Velocity Vectors Dispersions Applied: All Velocity & timing dispersions from Linear Analysis. Rotation of the launch vehicle 15 +/-3 RPMs. 0.5 sec release window for Probes B-E. 2 deg/sec tip off rate of Launch Vehicle. THEMIS MIWG #3Probe Separation Analysis - Page 20June 15 & Monte Carlo Simulation More Details In Addition to the new dispersion the simulation also includes modeling of the Early Attitude Maneuvers. 18,000 cases completed for each probe. (1000 cases for every 5 of a 90 phase of the launch vehicle.) Run at 1 min resolution in GTDS A E Early Attitude Maneuver Sequence D C B THEMIS MIWG #3Probe Separation Analysis - Page 21June 15 & Monte Carlo Simulation Results For each Probe and the LV post-release minimum approach distance to any of the other objects was tracked: THEMIS MIWG #3Probe Separation Analysis - Page 22June 15 & Summary & Conclusions Linear separation analysis of separation springs and residual thrust. - Nominal margins remain high. - 3sigma margins remain positive. 3D re-contact analysis - Nominal and 3sigma separation checks out. Early attitude maneuvers - Effects are minimal but are beneficial to separation. Monte Carlo simulation - 3 sigma dispersions show no re-contact due to orbital perturbations.