RISK ASSESSMENT APPLICATIONS TO SCIENCE AND EXPLORATION MISSIONS Dr. Todd Paulos [email protected] Risk Analysis of Aerospace Missions II: Mission Success Starts with Safety Workshop Key Bridge Marriott Arlington, Virginia October 29, 2002 Introduction z Brief PRA Review z Exploration Missions z Mars ’03 z Mars ’07 z Mars ’09 z MSR (Mars ’13? Or Mars ‘not in my lifetime) z Science Missions z CloudSAT z GRACE z Herschel Planck z Summary SRA, October 29, 2002 T. Paulos 2 Brief PRA Review Inputs to Decision Making Process Master Logic Diagram (Hierarchical Logic) Event Sequence Diagram (Logic) IE End State: ES1 A B End State: OK EndEnd State: State: ES2 ES2 End State: ES2 C D E End State: ES1 End State: ES2 Event Tree (Inductive Logic) Fault Tree (Logic) One to Many Mapping of an ET-defined Scenario End Not A IE A B C D E NEW STRUCTURE State LOGIC MODELING Logic Gate 1: OK Basic Event Internal initiating events One of these events External initiating events 2: ES1 Hardware components AND 3: ES2 Human error 4: ES2 Software error one or more Common cause of these 5: ES2 elementary Environmental conditions events 6: ES2 Other Link to another fault tree Probabilistic Treatment of Basic Events Model Integration and Quantification of Risk Scenarios Risk Results and Insights 30 50 60 25 50 40 End State: ES2 Integration and quantification of 20 40 30 100 logic structures (ETs and FTs) 30 15 Displaying the results in tabular and graphical forms 10 20 80 and propagation of epistemic 20 uncertainties to obtain Ranking of risk scenarios 10 5 10 End State: ES1 60 0.02 0.04 0.06 0.08 Ranking of individual events (e.g., hardware failure, 0.01 0.02 0.03 0.04 0.02 0.04 0.06 0.08 minimal cutsets (risk 40 human errors, etc.) scenarios in terms of Examples (from left to right): 20 basic events) Insights into how various systems interact Probability that the hardware x fails when needed likelihood of risk Tabulation of all the assumptions Probability that the crew fail to perform a task 0.01 0.02 0.03 0.04 0.05 scenarios Identification of key parameters that greatly inflence Probability that there would be a windy condition at the time of landing uncertainty in the likelihood estimates the results The uncertainty in occurrence of an event is Presenting results of sensitivity studies PROBABILISTIC characterized by a probability distribution SRA, October 29, 2002 T. Paulos 3 Small Event Tree vs. Large Event Tree Approaches z Small Event Trees z Systems with repair z Steady-state systems dealing with perturbations z Mutually exclusive set of initiating events develops into set of event trees z Large Event Tree z Systems without repair z Dynamic missions dealing with mission objections and performance z One initiating event develops into a single, large event tree SRA, October 29, 2002 T. Paulos 4 Three Important Things z Do NOT emphasize the “P” in PRA z The first benefit of doing a PRA is in doing the process z Scenario approach z Systems analysis z The second benefit of doing a PRA is that it identifies and prioritizes risks z Helps with risk management efforts z Cost-benefit analyses SRA, October 29, 2002 T. Paulos 5 Mars Exploration Rover (’03) SRA, October 29, 2002 T. Paulos 6 MER Assembly SRA, October 29, 2002 T. Paulos 7 Mission Requirements z Key Requirements z Level 1: Provide a surface mission lifetime of ¡ 90 sols z Level 1: Provide a UHF communications capability on the surface of Mars compatible with the Mars Surveyor 2001 Orbiter and/or a compatible orbiting asset z Level 1: Accommodate science payload z Panoramic Camera (PanCam) z Miniature Thermal Emission Spectrometer (mini-TES) z Mössbauer Spectrometer (MS) z Alpha Particle X-Ray Spectrometer (APXS) z Microscopic Imager (MI) z Rock Abrasion Tool (RAT) z Mission Constraints z Each Mission Duration = 90 sols z Two Concurrent Landed Missions - Prime missions overlap from 2/25/04 to 4/6/04 SRA, October 29, 2002 T. Paulos 8 MER Cruise Stage and Lander SRA, October 29, 2002 T. Paulos 9 MER EDL and Deployment SRA, October 29, 2002 T. Paulos 10 MER Rover SRA, October 29, 2002 T. Paulos 11 Rover “Arm” z Arm has three joints, similar to a human arm z Four tools are located on the arm z The Microscopic Imager z The Mössbauer Spectrometer z The Alpha Particle X-Ray Spectrometer z The Rock Abrasion Tool SRA, October 29, 2002 T. Paulos 12 Cameras z Each Rover has nine cameras z Four Hazcams z Two Navcams z Two Panoramic Camera z One Microscopic Imager SRA, October 29, 2002 T. Paulos 13 Miniature Thermal Emission Spectrometer z Infared spectrometer z Studies mineralogy of rocks and soils z Detects patterns of thermal radiation z Only 5 pounds SRA, October 29, 2002 T. Paulos 14 Mössbauer Spectrometer z Instrument designed to specifically study iron- bearing materials z Very sensitive z Very small (fits in the palm of hand) z Instrument head in contact with object for 12 hours SRA, October 29, 2002 T. Paulos 15 Alpha Particle X-Ray Spectrometer z The APXS is designed to study the alpha particles and x-rays emitted by rocks and soils in order to determine their elemental chemistry z Alpha particles are emitted during radioactive decay and X-rays are a type of electromagnetic radiation z Most APXS measurements will be taken at night and will require at least 10 hours of accumulation time, although just x-ray alone will only require a few hours SRA, October 29, 2002 T. Paulos 16 Flight Schedule MER-A Open Phase MER-B Open Phase Phase Definition Start Start Launch to thermally stable, positive energy balance Launch May 30, 2003 June 25, 2003 state, launch telemetry played back Cruise End of Launch phase to Entry-45 days May 31, 2003 June 26, 2003 Approach Entry-45 days to Entry November 20, 2003 December 11, 2003 EDL Entry to end of critical deployments on Sol 1 January 4, 2004 January 25, 2004 Egress End of EDL to receipt of DTE on Sol 4 January 4, 2004 January 25, 2004 Surface Mission End of Egress to EOM January 8, 2004 January 29, 2004 Successful receipt of last scheduled UHF data EOM April 6, 2004 April 27, 2004 return the night of Sol 91 SRA, October 29, 2002 T. Paulos 17 EDL Sequence # )9' " ' 9'& " 2)" ' / 7 ; * #.' * #" ' # )-# !"!"$< " γ## # > #%! *# #%!(& +,#----!"-!"$ #%&' ( )" %# # !"#"$ # !"##"$ # #6 (& . " #/+ '0&1' !" Launch =6/27/03 #0 2*34 -- 5" Arrival = 2/8/04 #/ &! 7 *8/0(93/ :-5#-"5"$ Landing at 10N #6 .' ---#" # *- Nominal Times #6 '&?#/ @ #!" and States #/ 6% ( < *" #(4 $% &7 * *A" # *" SRA, October 29, 2002 T. Paulos 18 MER PRA Tasks z Form PRA team z JPL engineers z PRA consultants z Weekly meetings z Training z Definition of PRA goals z Schedule z Analysis z Programmatic reviews SRA, October 29, 2002 T. Paulos 19 JPL Personnel z Fault Protection z Flight System Engineering z Reliability z Engineering Economics, Cost & Risk Analysis SRA, October 29, 2002 T. Paulos 20 PRA Task Objectives z Participate in the Risk Management process z Risk awareness z Looking at things from a sequence/scenario perspective z Hardware and operational aspects z Interfaces, human interaction, external events and common cause failures z How to use PRA results z Identify the largest contributors to risk z Identify ways to mitigate or prevent risks z Perform cost-benefit trade studies z Train participants in PRA z Give JPL a better understanding of what PRA is and what it can do z Focus on EDL portion of MER mission z Approach z Deployment SRA, October 29, 2002 T. Paulos 21 Example Event List z Deployment Phase • remove lander batteries from • shutdown bus • survive night 2 • isolate lander bus from rover • morning wake bus • extend lander petals • deploy PMA • retract airbags • shutdown • release middle wheel • survive night 1 • cut rover/lander cable 3 • morning wake • turn in-place • cut rover/lander cable 2 • acquire surface image for egress • deploy rocker suspension (rover • drive off lander deck lift/rocker suspension deploy) • vehicle survives deploy phase • rocker deploy • find sun • disconnect lift mechanism • Subsystem survival • release rear wheels • bogie deploy (rear wheel drives back) SRA, October 29, 2002 T. Paulos 22 EDL Event Sequence z Event tree includes functions that need to occur for: z Vehicle survival z Mission success z Failures that could end mission z Event tree development is an iterative process z Changes made periodically to reflect changes to hardware or operations z Simplifications can be made once the model is felt to be complete or for computational purposes z Event tree development tried to incorporate as much as possible from the mission level fault tree SRA, October 29, 2002 T. Paulos 23 Example Event Tree terminal descent enable RAS ground acquire RAD fire airbag inflate backshell IMU backshell IMU TIRS not TIRS three sigma rocket bridle disable no unintentional ground phase acquisition firing solution reatiner airbags needed surface wind assisted release pyro buses firing of pyro impact release day deceleration bus survival TERM-DES-PH EDL-RAS EDL-GND-ACQ EDL-RAD-FIR-SOL EDL-ARBG-REL EDL-ARBG-INF APR-BS-IMU EDL-BS-IMU EDL-TIRS-N EDL-TIRS EDL-3S-HOR-V EDL-RAD EDL-BRID-REL EDL-D-PBUS-E22 EDL-UPF-E23 EDL-IMPACT-SUR # END-STATE-NAMES 1T BASE-PET-DWN 2 LOV 3T BASE-PET-DWN 4 LOV 5 LOV 6 LOV 7 LOV 8 LOV 9T BASE-PET-DWN 10 LOV 11 T BASE-PET-DWN 12 LOV 13 LOV 14 LOV 15 LOV 16 LOV 17 LOV 18 T BASE-PET-DWN 19 LOV 20 T BASE-PET-DWN 21 LOV 22 LOV 23 LOV 24 LOV 25 LOV 26 T BASE-PET-DWN 27 LOV 28 T BASE-PET-DWN 29 LOV 30 LOV 31 LOV 32 LOV 33 LOV 34 LOV 35 LOV 36 LOV 37 LOV 38 LOV SRA, October 29, 2002 T.