By Buz Carpenter, Smithsonian Udvar Center Docent & former SR-71 Instructor Pilot.
SR-71As 29 operational aircraft built, 11 lost. Trainers built- 2 SR-71Bs, 1 lost & 1 SR-71C
Historical: 54,000 flying hours; 17,000 sorties; 3500 ops missions; 11,000 ops hours; 26,000 refuelings.
1St Flt 22 Dec 1964, 1st Combat Flight March 1968, & Operational Flights end Oct 1989
Aircraft 972 arrives Dulles Airport after Speed runs (LA to Dulles 64 min) on 6 Mar 1990
Structure – 93% titanium – America’s first stealthy A/C & last designed with Slide rule
Speed -. Top speed 3.3 mach, 2,200 Miles/hour, 36 miles/min or 3200feet/sec
Faster than a standard 30.06 hunting rifle bullet when fired. Normal turn took about 75nm+ radius
Why black? (1) Protect mostly titanium surfaces, (2) best heat radiating color to help remove heat from the aircraft during flight and pass heat into the extremely cold upper air atmosphere (-55°C/-70F).
Average temp At cruise, about 600°F (causes the aircraft to grow 3-4 inches length & 1-2 width during cruise). Temp range cool 450 F to hot engine area 3200 F. Pilot windows 620 F
J58 bleed bypass turbojet engines 34,000 lbs thrust in afterburner at sea level; afterburners lit coming off tanker to initiate climb and acceleration; stay on continuously for cruise until descent 1-1/2+ hour later.
Engine Chemical Ignition System TEB (triethylborane), a pyrophoric (burns on contact with air) with burn temp up to 3000°F.
Fuel – JP-7 kerosene base with additives; tanks inerted with nitrogen to prevent auto detonation
Engine oil 70-550°F normal temp range; consistency at 60°F honey, 40°F Jell-O, 32°F solid. Preheat engine to 70°F before start.
Tires BF Goodrich, aluminum powder impregnated to reject airframe heat; 425 psi filled with nitrogen; 22 ply rating; 3 ply tread.
Glass – Laminated Quartz glass. About 2.5 inches thick
Flight duration – Most training and ops flights 2.5-4.5 hours (required one or two in-flight refuelings)
Aerial refueling – Aircraft carries up to 80,000lbs of fuel (12,000+ gallons). Refueling normally lasted about 12-15 minutes with 70,000-80,000 lbs of fuel transferred. Normally flown around 25,000 ft with KC-135Q tanker starting at about 325 knots; as fuel transferred from tanker; it would accelerate to 350 knots IAS (its airspeed limit). Max distance between refuelings about 2800 nm (3200 statute miles).
Pressure suits – Derived from Gemini designs used through mid 70s. Late 70s replacement 1030 pressure suits would later serve as the initial Space Shuttle suits for Shuttle test flights.
Two Man Crew (1) Pilot in front with normal flight controls and functions, (2) Reconnaissance Systems Officer in back had no flight controls; ran astronavigation system, all camera systems, and the aircraft systems checklist; controlled the electronic defensive systems; and did many of the radio calls.
View at Altitude – At 80,000 ft you can see the curvature of the Earth about 500 miles in all directions. The sky is a deep blue-black, as most of the atmosphere, which gives the blue color, is below.
Engine start – Normally 30 minutes prior to takeoff; enough time to do all ground checks and taxi to end of runway for one final check before taking the runway.
Performance points – Most take-offs at 40,000 lb fuel load.
- From brake release and afterburner light, about a 4,500 ft takeoff rolls of about 20 seconds.
- Liftoff at 210 knots (about 240 mph).
- Rapid climb passed through 20,000 ft in about 2 minutes.
- After dropping off the tanker and afterburner ignition it took about 22 minutes to climb to 75,000 ft + and Mach 3. This took about 360 nautical miles distance and consumed 1/3 of your fuel.
- Level off normally around 75,000+ ft to a cruise-climb condition that, as fuel burned off, would climb up around 82-85,000 ft before starting down.
- Descent and deceleration from 80,000+ ft to 25,000ft took about 10 minutes and 220 nm.
- Landing approach speed was 175 knots plus (200 mph) with landing at 150-155 knots (170mph). With the large orange drag chute the aircraft would stop in about 5000 ft. If the drag chute did not work it was a 10,000 ft landing roll out to slow and stop the aircraft.
- Film and recorders would be down loaded for processing after engine shutdown
Buz Carpenter, Smithsonian Udvar Hazy Center Docent and former SR-71 Instructor Pilot