C null 01-17-2011
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C null 01-17-2011 Presentation Transcript

  • 1. How one Functional Human-Factors Requirement Influenced a Rocket Dr. Cynthia H. Null, Technical Fellow NASA Engineering and Safety Center This briefing is for status only and may not represent complete engineering information 1
  • 2. Outline• Development of CxP Human System Requirements• Human Tolerance to Acceleration and Vibration• Thrust Oscillation• Developing a performance criterion for vibration• Validation of a countermeasure• Lessons Learned This briefing is for status only and may not represent complete engineering information 2
  • 3. Development of CxP Human System Requirements• Derived from NASA-STD 3000 (now 3001)• Focus on crew health and safety• Focus on performance issues during a mission, specifically – The human and system must function together – Within the environment(s) and habitat(s) – To accomplish tasks for mission success This briefing is for status only and may not represent complete engineering information 3
  • 4. Example: High Level Functional Performance Requirement• Design system is to allow for all crewmembers to perform any of the required tasks efficiently and effectively, for nominal, off- nominal and emergency operations, thus ensuring crew health, safety, and mission success.• System means vehicle, habitat, operations• Efficiently, so that all mission goals are met• Effectively = low probability of error = within the time required Human performance is affected by nearly all aspects of the mission and system design: vehicle design, subsystem design, environments, ConOps, interfaces, tasks, procedures, etc. This briefing is for status only and may not represent complete engineering information 4
  • 5. Examples of Specific Requirements• The system shall provide potable water at or below the physiochemical limits [from] table Potable Water Physiochemical Limits at the point of crew consumption.• The system shall provide a portable fire suppression system.• The system shall provide a translation path for assisted ground egress of an incapacitated suited crewmember.• Hatches shall be operable without the use of tools.• Connectors shall have physical features that preclude mis- mating and misalignment.• Controls shall be designed such that the input direction is compatible with the resulting control response. This briefing is for status only and may not represent complete engineering information 5
  • 6. Examples of Requirement Categories• Anthropometry, biomechanics, and strength• Environments• Safety• Architecture• Crew Functions (Food, Hygiene, Exercise, Medical)• Crew Interfaces• Maintenance• Information Management• EVA This briefing is for status only and may not represent complete engineering information 6
  • 7. Acceleration Limits (CxP 70024 -- SRR 2006)This briefing is for status only and may not represent complete engineering information 7
  • 8. Occupant Protection: Crew Injury Risk Limits• The Constellation Architecture shall limit the injury risk criterion, β, to no greater than 1.0 according to the Brinkley Dynamic Response model in Appendix N, table Dynamic Response Limits. This briefing is for status only and may not represent complete engineering information 8
  • 9. Vibration Health Limit• The Constellation Architecture shall limit vibration to the crew such that the vectorial sum of the X, Y, and Z frequency-weighted [using ISO 2631-1] accelerations between 0.5 and 80 Hz is less than or equal to the levels and durations in [the] table during dynamic phases of flight. Maximum Vibration Maximum Frequency- Exposure Duration Per Weighted Acceleration 24-hr Period 10 Minutes 0.4 g rms 1 Minute 0.6 g rms This briefing is for status only and may not represent complete engineering information 9
  • 10. But what about performance during or after vibration?• Members of the Human Systems Special Interest Group (HSIG) wanted to develop additional requirements in Fall 2006, SRR time frame.• Not viewed as an issue (POGO for Gemini/Apollo, vibration low for shuttle)• Expectation that DOD had the necessary data and experience, if such a requirement would be needed This briefing is for status only and may not represent complete engineering information 10
  • 11. NESC AGILE Project (Oct 2007) (Assessment of Gravito-Inertial Loads and Environments ) • Literature Search • Workshop of Experts – NASA • Scientists (Human Performance, Medical) • Engineers (Propulsion, Seats, Suits, etc) • Astronauts (Apollo, Shuttle) • CxP Projects – DOD – Industry – University • Gap AnalysisLead: Dr. Bernard Adelstein This briefing is for status only and may not represent complete engineering information 11
  • 12. Vibration Levelg (0-peak) Historical Data/Guidelines/Requirements “Health Risks Likely” —ISO 2631-1:1997 Historic Crew Performance Vibration Limits (at “11 Hz”) Possible Perceptual & Physiological Aftereffects Severe Performance 1963 Gemini Centrifuge-Vibration Study Degradation (Vykukal & Dolkas, 1966) 3.5 Gx (Chest-in) Bias 0.14-1.65 gx vibration at 11 Hz*** Achievable Performance (Vykukal & Dolkas, 1966) •Simple visual & manual tasks only; Performance Degradation Gemini crew spec (0.25 g) •Coarse visual & manual tasks; speech Shuttle crew (0.1 g)? •Fine visual & manual tasks 12
  • 13. Crew Vibration Knowledge Gaps & RisksHSIR Vibration Health Limits based on ISO 2631-1 health-risk boundary •ISO health boundaries derived for upright body posture (1-Gz bias, i.e., head-down) and gz vibration for short-duration 1-, 3-minute exposure. •Validated for semi-supine posture (1-Gx bias, i.e., chest-in) for short duration only (Temple et al,1964), but NOT for 1-, 3-minute exposure. •Vibration tolerance differs between seat designs and seat-suit coupling (Temple et a., 1964) •ISO frequency-dependent vibration tolerance were derived for 1-Gz bias. Hyper-Gx alters human body and internal organ impedance; may require revised frequency-dependent weighting functions.Vibration Visual and Manual Performance •Bulk of performance literature is for upright body posture and gz vibration. •Vykukal & Dolkas (1966) for self-rated critical crew task performance at 3.5 Gx and Clarke et al (1965) for dial reading at 3.85 Gx are the only reported vibration studies for hyper-G bias. These two studies were conducted for Gemini vintage displays (and ConOps), only for gx vibration, and only at 11 Hz vibration (i.e., Titan-II POGO). •Orion will be commanded through electronic interfaces, i.e., virtual (soft) switch panels; procedures will be displayed electronically; computer-stored checklists will be located and navigated via an electronic procedure viewer. •Orion analyses indicate crew-seat vibration transfer in x-, y-, and z-axes. •Orion thrust oscillation response, currently 12 Hz, may change with seat, suit and display mitigations.Vibration Aftereffects •No systematic study (only anecdotal report by Faubert et al. (1963)) of perceptual and performance aftereffects for gx vibration at levels below the health limit This briefing is for status only and may not represent complete engineering information 13
  • 14. Thrust Oscillation (Nov 2007)• Issue raised at CxP Integrated Stack TIM• Thrust Oscillation Focus Team (TOFT) established Experts from several centers, many disciplines, industry – 1. Review the forcing functions, models and analysis results to verify the current predicted dynamic responses of the integrated stack – 2. Identify and assess options to reduce predicted responses – 3. Validate and quantify the risk to the Ares I vehicle, Orion spacecraft, crew, and other sensitive subsystems and components to the extent allowed by the Ares I/Orion design maturity – 4. Establish and prioritize mitigation strategies and establish mitigation plans consistent with the CxP integrated schedule This briefing is for status only and may not represent complete engineering information 14
  • 15. Thrust Oscillation Focus Team Team Membership• Leads - Garry Lyles / Eli Rayos (ILSM SIG)• Chief Engineer’s Office - Leslie Curtis• Vehicle Loads Analysis- Jeff Peck / Isam Yunis / Pravin Aggarwal• Vehicle Controls Analysis - Steve Ryan• Motor Analysis - Tom Nesman / Jonathan Jones / Dan Dorney / Jeremy Kenny / ATK Engineering (Tyler Nester / Terry Boardman)• Ares Vehicle Systems Integration - Rob Berry (Element Integration Lead)/ Bob Werka (Global Mitigation Lead)/ Belinda Wright / James Sherrard• Orion Systems Engineering - Chuck Dingle / Corey Brooker / Thomas Cressman (SM) / John Stadler (LAS) / Tom Goodnight (SM) / Keith Schlagel (LM)• Ares Systems Engineering - Joe Matus (US) / Rick Ballard (USE) / Wendy Cruit (FS)• Safety and Mission Assurance - Ho Jun Lee / Chris Cianciola• Crew and Human Factors - Phil Root / Bernard Adelstein• NESC Structures and Dynamics Team - Curt Larsen / Alden Mackey• NESC Consultants - Scott Horowitz / Gloyer-Taylor Labs (Paul Gloyer, Tim Lewis, Gary Flandro, Fred Culick, Vigor Yang)• Independent Structural Dynamics Discipline Experts - Hal Doiron / Bob Ryan / Luke Schutzenhofer / George Zupp / Ken Smith / Jim Kaminski / Jim Blair / George James• Boeing - Ted Bartkowicz / Steve Tomkies• Shuttle Booster Project Engineering - Mike Murphy / Steve Ricks / Sam Ortega• Aerospace Corporation - John Skratt / Kirk Dotson , et al• Pratt and Whitney Rocketdyne - Tom Kmiec / Steve Mercer This briefing is for status only and may not represent complete engineering information 15
  • 16. Why was more data necessary?• Modern displays are complex, crowded, small fonts and have different task and demands from historical experience• Understand impacts of vibration on crew performance• Exposure levels may exceed the ~0.1 g (0-to-peak) experience of Gemini-Apollo-Shuttle and maybe the previous 0.25 g limit• Previous results were at 11 Hz, CxP expected to be at 12 Hz• Quantify risk This briefing is for status only and may not represent complete engineering information 16
  • 17. Number Reading Task • Begin at central fixation • Locate magenta block • Read middle row • 5-s maximum viewing time •Is 3-digit string a monotonic (ascending/ descending) sequence? •50/50 “yes” / “no” 573 681 489 “No” 17 This briefing is for status only and may not represent complete engineering information
  • 18. Vibration and Reading (Stationary, 12 Hz Gx vibration)This briefing is for status only and may not represent complete engineering information 18
  • 19. Expected G-loading effects on human performance• Impaired accommodation and decrease static visual acuity• Decreased visual sensitivity• Increased response time• Decreased field of view• Increased workload This briefing is for status only and may not represent complete engineering information 19
  • 20. ARC 20-G Centrifuge Facility Chair reclining at 15.3 vibration chair (fixed) 20
  • 21. ARC 20-G Centrifuge Vibration Chair Display (raised)Head Restraint Dual triaxial Head Rest accelerometer assembly Vibration Egress Harness Actuator (1 of 4) 5-point restraint 400 lb capacity each Emergency 1.5 in max stroke switch 2-button handheld input device 21
  • 22. Critical Crew Capabilities• Two Critical Capabilities identified by Crew Office for thrust oscillation period: 1. Maintain situation awareness (SA) of vehicle state and vehicle status through processing Primary Flight Display (PFD) symbology 2. Manually steer (hand-fly) the vehicle immediately following exposure to vibration This briefing is for status only and may not represent complete engineering information 22
  • 23. Display Usability Rating Study (under 1-G and 3.8-G)1-D Graphical FeaturesCrew participants rated their abilityto acquire information about thestate of system (e.g., valve state)while ignoring the text This briefing is for status only and may not represent complete engineering information 23
  • 24. Display Usability Rating Study (under 1-G and 3.8-G)2-D Graphical FeaturesCrew participants rated theirability to use the PFD(while ignoring the text) This briefing is for status only and may not represent complete engineering information 24
  • 25. Task 2: Manual Control Flight TaskImmediately after TO vibration stops: •PFD disappeared •Screen remained blank for 2 s •PFD reappeared with pre-inserted four- quadrant pitch & roll offset: pitch-up or -down PLUS roll-left or -right •Participant instructed to make immediate initial joystick input to null the error in both axesFor full 30 s trial: •Superimposed continuous 0.05 Hz sinusoidal pitch & roll error •Participants made continuous joystick inputs to null errors (i.e., they “flew the needles”) This briefing is for status only and may not represent complete engineering information 25
  • 26. SA & Manual Steering Questions This briefing is for status only and may not represent complete engineering information 26
  • 27. Centrifuge Study (3.8-G): Error Rates And Response Times During Vibration Error Rate (ER) Response Time (RT)• Up to 7-fold increase in mean ER under some conditions (0.5 g for 10-pt)• Up to 450-ms increase in mean RT under some conditions (0.5 g for 10-pt) This briefing is for status only and may not represent complete engineering information 27
  • 28. Vibration Study (3.8G) : Error Rates and Response Times After Vibration Error Rate (ER) Response Time (RT)•ER and RT return to zero-vibration (last 5 trials) levels as soon as145-s vibration stops This briefing is for status only and may not represent complete engineering information 28
  • 29. Countermeasure Validation• Inspired from stroboscopic techniques commonly employed for visual inspection of oscillating and/or vibrating machinery• Developed an LCD monitor backlit by an array of LEDs, which could strobe synchronizely with respect to the vibration pattern, adjusting its phase and duty cycle This briefing is for status only and may not represent complete engineering information 29
  • 30. Display Strobe / Vibration Results (Stationary, 0.7-gx 12 Hz vibration)I. In the non-strobe condition, errors quadrupled (3.5% to 16.4%) and response times slowed by 325 ms with vibration, consistent with 0.7-g condition in previous studies. Lower constant luminance (EL) slowed response times by 110 ms.II. In the zero-vibration condition, display strobing slowed response times by 110 ms versus a display with comparable constant luminance (EL).III. Under 0.7-g vibration, display strobing at 5% duty cycle reduced error rates to ~5%, a level not significantly different than for zero vibration, and sped response times by 240 ms. This briefing is for status only and may not represent complete engineering information 30
  • 31. Vibrations StudiesStudy Team Scientists:ARC/TH: B. Adelstein, B. Beutter, M. Kaiser, R. McCann, L. StoneJSC/SK: W. PaloskiIn Collaboration with:ARC/TH: M. Anderson, F. Renema, B. Spence, M. Godfroy, G. Flores, D. MunozARC 20-G Centrifuge Facility: C. Wigley, N. Rayl, T. Purcell, J. Dwyer, R. Ryzinga, P. Brown, T. Luzod, R. Westbrook, M. Steele, V. PostARC Engineering and Hazard Analysis: O. Talavera, M. Ospring, R. PhillipsARC Chief Medical Officer & HRIRB Chair: R. PelligraJSC/CB: P. Root, T. Verborgh, M. Ivins, M. Kelly, L. MorinJSC/SF: K. HoldenJSC/ILSM-SIG: (TOMCAT) E. Rayos, M. SamirJSC Engineering: A. Sena, D. Gohmert, B. DanielJSC Medical Monitors: J. Jones, R. Scheuring, J. ClarkJSC Video: J. Blair, R. MarkowitzESMD-HRP: B. Woolford, J. Connolly, D. Russo, D. GroundsHSIG: J. Dory, J. RochlisNESC: C. NullOrion Project: J. Fox, J. FalkerParticipants from ARC community & JSC Crew Office This briefing is for status only and may not represent complete engineering information 31
  • 32. Lessons Learned• Expertise is critical. Don’t confuse intelligence with expertise• System issues are solved though inclusion – Cast a wide net – Do not assume from where the solution will come• Archive data• Write up findings• Beware of solutions for a single condition• Systems management and systems engineering are NOT synonyms• Interconnections may not be obvious• Not everything that is critical for design (or operations) can be found in the requirement or interface documents This briefing is for status only and may not represent complete engineering information 32