Contributions and Lessons from the X-15 Program For Access to Space Projects

1. Contributions and Lessons from the X-15 ProgramFor Access to Space Projects Johnny Armstrong Chuck Rogers AFFTC Access to Space Office AIAA Symposium The X-Vehicles: Advancing the Limits of Technology June 16, 2000 Version 3

2. Outline • Historical Prospective • X-15 Contributions • Program Set Backs • Lessons • Concluding Remarks

3. X-Planes Historical Prospective X-38 X-37

4. X-15 Contributions • Exercised the Prediction Techniques available in the 50’s • Hypersonic Aerodynamics, Stability & Control, Heating, Space Ops, Energy Management, et al • Procedures/Operations • Low L/D Power-Off Landings • Test Techniques • Flight Planning with Simulators • Pilot Training with Simulators • Real-Time Mission Control • Transfer of Processes to Manned Space Program Traceable to Walt Williams, former head of the NACA High Speed Flight Station at Edwards

5. X-15 Program in Prospective The X-15 Program has been described “as the most successful flight research program ever conducted producing over 750 research papers and reports.” The X-15 Program was Lead with a Resolve to Proceed to Accomplish the Goals even in the Face of Major Failures

6. X-15 Flight and Repair Periods 1 Glide Flt +20 XLR-11 Flts 247K APU Fuel Tank Bulkhead Rupture Total Power Failure #1 81 M>3 Emer Land Damage Emer Land Damage/Mod M>5 Heat Damage 9 XLR-11 Flts #2 X-15A-2 53 M>2 M>4 M>6 M=6.7 APU Fuel Tank Rupture-Ground 314,750 FT 354K Crashed #3 65 199 125 Launch Aborts 12 Captive Flights

7. X-15-2 Rosamond Drylake Landing • XLR-11 Engine Fire Caused Emergency Landing • Incomplete Propellant Jettison at Landing • Fuselage Broken behind Cockpit • Aircraft Repaired and Flown again in 3 Months

8. X-15-3 Ground Run Explosion • Fuel Tank Pressure Relief Valve and Procedure Fault Caused Tank Rupture and Explosion • Aircraft Totally rebuilt from mid fuselage aft • Aircraft flew 16 Months Later

9. X-15-2 Emergency Landing at Mud Lake • Engine Power Stuck at 30% • Engine Shutdown Manually for Emergency Landing • Incomplete Propellant Jettison • Landing Flaps did not Deploy • Main Gear failed and Aircraft Rolled • Aircraft Repaired and Modified as X-15A-2 • Aircraft Flown again in 19 Months

10. SMITH RANCH 10 / 1 ELY TONOPAH RAILROAD VALLEY 2 MUD 34 / 4 DELAMAR 62 / 1 GRAPEVINE BEATTY PANAMINT LAS VEGAS BALLARAT HIDDEN HILLS 50 CUDDEBACK 1 / 2 SILVER 14 / 1 EDWARDS ROSAMOND 26 / 1 ROGERS 188 X-15 Emergency Landings • 10 Emergency Landings • 3 Were to Intermediate Lakebeds • 2 Were due to Faulty Instrumentation • 57 not 199 Flights if No Emergency Lakebeds

11. Local Heating Effects • Wing Leading Edge Slots • Windshield Shattering • Canopy Seals and Nose Gear Door Seals • Nose Gear Deployed (M=4.4) • Nose Gear Scoop Door Opened (M=4.5) • Main Skid Deployed (M=4.4)

12. X-15A-2 Modifications • Hypersonic Ramjet Test Capability • 29-inch Fuselage Extension - LH2 • External Propellant Tanks • Additional Peroxide Tank • Additional Helium Tank • New Canopy Windshield • Lengthened Landing Gear • Ablative Thermal Protection

13. Shock Impingement Heating • Major Structural Damage during Flight to Mach 6.7 • Shock Impingement Heating from Dummy Ramjet 7 to 10 Times Normal Heating • Melting of Inconel-X Lower Ventral (T>2800 deg F) • Data from Area Ceased about Mach 4 during Deceleration • Dummy Ramjet Separated from Aircraft during Flight

14. X-15-1 Total Power Failure • 67 Seconds after Engine Light, X-15-1 Lost All Power including the Engine • All Warning Lights Came On • Then All Lights went Off • Both APU’s Shutdown leaving no Hydraulic or Electric Power • Pilot Restarted One APU and Made an Emergency Landing at Mud Lake • The Electrical Overload was concluded to be caused by the IR Scanner being Tested to Track Missiles to be Launch at Vandenberg on Future Flights 67 Sec 4210 fps 108,000 Ft

15. 3.Dual use of same Guidance Needle • (Roll Angle Vs Sideslip) 1. FCS Dampers Disengaged 2. Auto Blending of RCS and Aero Controls Ceased 4. Nose manually driven away from Flight Path X-15-3 Crash • X-15-3 Broke-up in flight at about 65,000 feet while recovering from a Spin at Hypersonic Speed, killing the Pilot • A Series of Events Contributed to the Accident but the initial anomaly was electrical arcing in an experiment in a Wing Tip Pod Nose • 5. FCS Gain driven away from optimum by Electrical Transients • 6. Control Surface deflections excessive as Dynamic Pressure Increased during Entry • 7. Structural Capability Exceeded

16. Lessons • Incremental Envelope Expansion • Captive Flights and Glide Flights before Powered Flights • Reasonable Steps in Mach, Angle of Attack, Dynamic Pressure • Post Flight Inspection for Potential Hot Spots • Adopt Test Concept to Provide Emergency Landing Sites • Insure Adequate Structural Margin for Emergency Landings • Optimize Propellant Jettison System for Emergency Landing • Make Sure Your Decision Instrumentation is Correct • Do not use the same Display for 2 Different Parameters • Prevent Electric Arcing at High Altitude

17. Concluding Remarks X = EXPERIMENTAL Experiment Implies Results Unknown RECOVER FROM FAILURES TO FLY ANOTHER DAY AD INEXPLORATA

18. The X-15’s Today X-15-1 Smithsonian Institute X-15A-2 USAF Museum X-15-3 Replica at NASA DFRC

19. BackupThe Dummy Ramjet Search • Data Showed Sudden Decrease in Longitudinal Acceleration during the Turn in the Landing Pattern • Concluded that the Ramjet Separated from the Aircraft at that Point • Correlated with Radar Track Data and Selected Likely Impact Area on Edwards Bombing Range • Two-Man Search Party Located Ramjet on First Walk