1. 12004 MAPLD/202Portillo Lunar Module Attitude Controller Assembly Digital Input Processing José Portillo Lugo jportillo34@hotmail.com

2. 22004 MAPLD/202Portillo Uses the Apollo Guidance Computer Counter Interrupt system. Two types of Input to the Apollo Guidance Computer: –PROPORTIONAL Make use of the LM Guidance Computer Counter Interfaces for Analog- to-Digital conversion, and Transformer-based Interface circuit. Used for Rate Command Augmentation Mode. –DISCRETE Make use of the LM Guidance Computer discrete Interface Channel bits. Used for Pulse Mode. Used for Man-in-the-Guidance-Loop capabilities. Lunar Module Attitude Controller Assembly Digital Input Processing

3. 32004 MAPLD/202Portillo Proportional Input Processing

4. 42004 MAPLD/202Portillo 1958: NACA technical paper describing “Systems that Command Velocity” as feedback control concept. Simulator investigation of Command Reaction Controls - Holleman, Euclid C.; Stillwell, Wendell H. - NACA RM H58D22 - April 14, 1958. 1959: Development of a Self-Adaptive flight control system: the X-15 research 1960: vehicle. 1963: Development of an Analog Rate Command Augmentation/Attitude-Hold 1964: control system for the Gemini Spacecraft. 1964: AIAA conference paper describing a Rate Command and Acceleration Comand systems implemented in the Langley Research Center Gemini- Agena Docking Simulators. Full-Scale Gemini-Agena Docking using Fixed and Moving base Simulators - Hatch, Howard G.; Riley, D. R.; Cobb, J. - AIAA paper 64-334 - June-July 1964. 1964: Apollo lunar program: decision to implement a “Digital Autopilot” for the Lunar Module Primary Guidance System. Manual Rate Command Augmentation Systems A brief chronology

5. 52004 MAPLD/202Portillo 1966: NASA LRC technical paper describing a Rate Command and Acceleration Command electronic control system for control of the Lunar Landing Research Vehicle. Flight Tests of a Manned Rocket-Powered Vehicle Utilizing the Langley Lunar Landing Research Facility - O’Bryan, Thomas C. - Presented at AIAA Guidance and Control Specialists Conference - Siattle, Washington - August 1966. 1966: NASA technical paper describing a Rate Command Augmentation system (fly-by-wire bang-bang) implemented in the DFRC lunar Landing Research simulation vehicle. Operational experience with the Electronic Flight control Systems of a lunar-Landing Research vehicle - Jarvis, Calvin R. - NASA TN D-3689 - July 5, 1966. 1966: Grumman Aircraft developed a Lunar Module Simulator for development and testing purposes. An Analog processing for the Hand Controller was implemented. Lunar Module Hover and Landing, Separation and Docking Simulation - Greene S.; Russo, J. - Presented at AIAA Flight Test, Simulation and Support Conference - Cocoa Beach, Florida - February 6-8, 1967. Manual Rate Command Augmentation Systems A brief chronology

6. 62004 MAPLD/202Portillo 1968: Development of a Rate Command Augmentation system embedded into the LGC Digital Autopilot. 1969: First flight test of the Lunar Module Digital Autopilot, including its manual Rate Command Augmentation/Attitude-Hold capability. Apollo 9 Mission in earth orbit. 1969: First Lunar Landing operation for the Lunar Module Digital Autopilot. Apollo 11 Mission. It includes an more complete Manual Rate Command Augmentation System. Manual Rate Command Augmentation Systems A brief chronology

7. 72004 MAPLD/202Portillo Embedded into the Digital Autopilot Software. Shows all the advantages of Digital Control System implementations over Analog Control System implementations: input data processing follows conditional paths, switching points, and storage for external entered and internal fixed memory constant parameters. Make use of the Counter Interrupt system of the Apollo Guidance Computer. Apollo Lunar Module Digital Manual Rate Command Augmentation System Proportional Commands ExternalControlParameters

8. 82004 MAPLD/202Portillo “A” Circuit “Start Gating” bit 10 cps Out-Of-Detent Inbit (Channel 31) 10 cps Digital Autopilot DETENTCK EXTEND READ CHAN31 TS CH31TEMP MASK BIT15 EXTEND BZF RHCMOVED CAF OURRCBIT MASK DAPBOOLS EXTEND BZF PURGENCY RHCMOVED CS RCSFLAGS MASK BIT9 ADS RCSFLAGS CA OURRCBIT MASK DAPBOOLS EXTEND BZF JUSTOUT - 1 RATERROR CA CDUX TS CDUXD HI LO (proportional) RHCCTR Counter Apollo Lunar Module Digital Manual Rate Command Augmentation System Interface Level

9. 92004 MAPLD/202Portillo Two steps: –INITIALIZATION PASS. –NORMAL RATE COMMAND PASS. Two Control Laws were employed for Manual Rate Command Augmentation: –DIRECT RATE Used each time the change in “Commanded Rate” between two Digital Autopilot passes exceeds a “Breakout Level” Switch. Computes Jet-on time based only in Rate Error information: do it fast! To damp vehicle Rates below a “Target” Dead Band (before return control to the Attitude Hold Autopilot). Used on a per-Axis base. –PSEUDO-AUTOMATIC Used while there is no Manual input. To Hold an Attitude. Computes Jet-on time based upon Rate and Attitude Error information. Uses a Phase-Plane logic to exercise Control. It can achieve very small Commanded Rates. Used on a per-Axis base to prevent Attitude drift about uncommanded Axes. Apollo Lunar Module Digital Manual Rate Command Augmentation System

10. 102004 MAPLD/202Portillo Apollo Lunar Module Digital Manual Rate Command Augmentation System Control Law Selection MCR Commanded Rate Exceeds Breakout Level? no yes Breakout Level Switch ACA Counter PSEUDO- AUTOMATIC Control Law DIRECT RATE Control Law Dead Band Switch Digital Autopilot Control Parameters: Constant Values in Rope Memory Entered in-flight by crew Flags set ON/OFF by previous iterations Control Flow Flags Scaling + -

11. 112004 MAPLD/202Portillo Discrete Input Processing

12. 122004 MAPLD/202Portillo Make use of the Guidance Computer Input Channel. Provides a way to input low Rate Commands as well as Man-in-the-Guidance- Loop capabilities. Apollo Lunar Module Digital Manual Minimum Impulse and LPD Redesignator Discrete Commands ExternalControlParameters

13. 132004 MAPLD/202Portillo “D” Circuit Minimum Impulse & Discrete LPD Discrete Inbit (Channel 31) Out-Of-Detent Inbit (Channel 31) 10 cps CA L No MASK -AZBIT CCS A -AZ CS AZEACH ADS AZINCR1 CA L MASK +AZBIT CCS A +AZ CA AZEACH ADS AZINCR1 CA L MASK -ELBIT CCS A -EL CS ELEACH ADS ELINCR1 CA L MASK +ELBIT CCS A +EL CA ELEACH ADS ELINCR1 TCF RESETRPT Interrupt 10 (Redesignator Trap) Fixed-Address Instruction 4050 DXCH ARUPT 4051 CA RUPT10BB 4052 XCH BBANK 4053 TCF PITFALL Digital Autopilot Apollo Lunar Module Digital Manual Minimum Impulse and LPD Redesignator Interface Level

14. 142004 MAPLD/202Portillo Two Discrete Inputs: –MINIMUM IMPULSE Enables the crew to perform economical low Rate maneuvers. Embedded into the Digital Autopilot Software. LM Guidance Computer Channel 31 includes the Input bits. –LPD REDESIGNATOR Enables the crew to enter into the Lunar Landing Automatic Guidance Loop. Embedded into the Landing Approach Phase Guidance Software (the so called “Manual Steering Section”). LM Guidance Computer Channel 31 includes the Input bits. LPD Redesignation Input Commands are processed by the Interrupt system. Apollo Lunar Module Digital Manual Minimum Impulse and LPD Redesignator

15. 152004 MAPLD/202Portillo Uses the Apollo Guidance Computer Counter Interrupt system. Two types of Input to the Apollo Guidance Computer: –PROPORTIONAL Make use of the LM Guidance Computer Counter Interfaces for Analog- to-Digital conversion, and Transformer-based Interface circuit. Used for Rate Command Augmentation Mode. –DISCRETE Make use of the LM Guidance Computer discrete Interface Channel bits. Used for Pulse Mode. Used for Man-in-the-Guidance-Loop capabilities. Lunar Module Attitude Controller Assembly Digital Input Processing In resume

16. 162004 MAPLD/202Portillo 1.Handling Qualities for Pilot Control of Apollo Lunar-Landing Spacecraft – Cheatham, D. C., Hackler, C. T. - Journal of Spacecraft and Rockets, Vol. 3, No. 5, May 1966, pp. 632- 638. 2.MIT's Role in Project Apollo - Volume III – Computer Subsystem – Hall, Eldon C. - August 1972. 3.Manual Attitude Control of the Lunar Module – Stengel, Robert F. – AIAA paper 69-892 – August 1969. 4.Apollo Experience Report - Crew Station Integration - Volume III – Spacecraft Hand Controller Development - Wittler, rank E. – Lyndon B. Johnson Space Center, Huston Texas 77058 - March 1975. 5.A Manual Retargeted Automatic Landing System for the Lunar Module - Klumpp, Allan R. – Journal of Spacecraft and Rockets - Volume 5 - Number 2 -February 1968 - pp 129- 138. 6.Lunar Module Digital Autopilot - Widnall, William S. - Journal of Spacecraft - Vol. 8, No. 1 - January 1971. 7.Lunar Module Attitude Controller Assembly Input Procesing – Portillo Lugo, José R. – MAPLD 2004 Conference paper – September 2004. References