High Altitude Tribute to the High Fliers

From the Bell X1 to the SR71 a high altitude pursuit. Watch in full screen your going flying.

The World record for both speed and height by an air-breathing aircraft (not a rocket) was 85,135 feet.

It was set in an SR-71 Blackbird in 1976. The speed record is also held by an SR-71, at 2,193 mph. This is not as high or as fast as the airplane can fly, however, its absolute speed and altitude limits are classified.

Most US military aircraft can exceed 50,000 feet, if they really try. Again, the limits are classified.

Most commercial jetliners cruise somewhere between 30,000 and 45,000 feet above mean sea level. At higher speeds and altitudes, there isn’t enough oxygen in the air to continuously burn the jet fuel required to stay up there. Engines designed to work very well that high, have serious limitations when they are operated closer to the surface.

There are aircraft that have flown higher and faster (the X-15) but they really aren’t aircraft, they are rockets, because they carry their own source of oxygen, instead of using the air. However, the fastest and highest airplanes are the American SR-71 Blackbirds.

As aircraft climb to higher altitudes, the air outside gets thinner. The actual equation for the change in pressure with altitude gives an exponential rather than linear decay. This is essentially because air is squash-able so is compressed together at lower altitudes. Therefore pressure is decreased more rapidly near the ground than at higher altitudes. It is approximately halved by 18,000 ft.

Airplanes are pressurized to maintain a comfortable living environment for human beings. Ideally an airplane would be pressurized to ground level pressure, but this is not practical as the fuselage of a plane would have to be incredibly strong (and hence very heavy and expensive to fly) to withstand the outward force caused by the high pressure inside. Therefore modern commercial jets compromise and are pressurized to an altitude of 5000-8000 ft. This explains the phenomenon of ‘ears popping’ on take-off and landing as the air trapped in the ear is effected by the change in pressure from ground level to this effective altitude.

A typical commercial jet (most standard flights) cruises at around 28-35,000 ft (up to 6.6 miles of altitude). The main exception is Concorde which was designed to fly at a higher altitude (and hence lower wind resistance) at around 45,000 ft. Although many jets could fly at higher altitudes, they are usually certified to an altitude giving a wide safety margin.

For example the new generation Boeing 737 is certified to 41,000 ft (7.8 miles). Many military jet aircraft are able to fly considerably higher. Often, the plane itself is not pressurized and instead the pilot wears a pressure suit that provides him with a pressurized environment. Originally, very high altitude military planes were used for surveillance — the current versions of the famous U2 spy plane, originally designed in the 1950s can cruise at up to 90,000 ft (17 miles). The Stealth Bomber cruises at up to 50,000 ft (8.3 miles) and many other combat planes can now also attain significant altitudes.


Video uploaded by U Tube user MB Productions


From Wikipedia:

During the X-15 program, 13 different flights by eight pilots met the USAF spaceflight criterion by exceeding the altitude of 50 miles (80 km) thus qualifying the pilots for astronaut status.  The USAF pilots qualified for USAF astronaut wings, while the civilian pilots were awarded NASA astronaut wings in 2005, 35 years after the last X-15 flight.

Of all the X-15 missions, two flights (by the same pilot) qualified as space flights per the international (Fédération Aéronautique Internationale) definition of a spaceflight by exceeding 100 kilometers (62.1 mi, 328,084 ft) in altitude.

Early flights used two Reaction Motors XLR11 engines. Later flights were undertaken with a single Reaction Motors Inc XLR99 rocket engine generating 57,000 pounds-force (250 kN) of thrust that powered the aircraft. This engine used ammonia and liquid oxygen for propellant and hydrogen peroxide to drive the high-speed turbopump that delivered fuel to the engine.  It could burn 15,000 pounds (6804 kg) of fuel in 80 seconds.  The XLR99s could be throttled, and were the first such controllable engines that were man-rated.

The XLR11 used ethyl alcohol and liquid oxygen, and the XLR99 used ammonia and liquid oxygen as fuel.  The X-15 reaction control system (RCS), for maneuvering in low-pressure/density environment, used hydrogen peroxide as a mono-propellant.  More specifically, it was high-test peroxide, which decomposes into water and oxygen in the presence of a catalyst, and can give an ISP of 140 seconds.  The HTP also fueled a turbopump for the main engines and auxiliary power units (APUs).  Additional tanks for helium and liquid nitrogen performed other functions, for example the fuselage interior was purged with helium gas and the liquid nitrogen was used as coolant for various systems.

There are two definitions of how high a person must go to be referred to as an astronaut. The USAF decided to award astronaut wings to anyone who achieved an altitude of 50 miles (80 km) (80.5 km) or more. However, the FAI set the limit of space at 100 kilometers (62.1 mi).  Thirteen X-15 flights went higher than 50 miles (80 km) and two of these reached over 100 kilometers.

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The Development of the X-15

NASA documentary about the developement and early flights of the X-15 rocket plane.

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Cockpit Blackbird

From Wikipedia:

The SR-71 served with the U.S. Air Force from 1964 to 1998. Of the 32 aircraft built, 12 were destroyed in accidents, and none were lost to enemy action.  The SR-71 has been given several nicknames, including Blackbird and Habu, the latter in reference to a Okinawan species of pit viper.  Since 1976, it has held the world record for the fastest air-breathing manned aircraft, a record previously held by the YF-12.

The Blackbird’s Pratt & Whitney J58-P4 engines were innovative marvels that used the most extreme materials of their time. Each J58 could produce 32,500 lbf (145 kN) of static thrust.  The J58 was most efficient around Mach 3.2,  the Blackbird’s typical cruising speed.

The SR-71 was the world’s fastest and highest-flying operational manned aircraft throughout its career. On 28 July 1976, SR-71 serial number 61-7962 broke the world record for its class: an “absolute altitude record” of 85,069 feet (25,929 m).   Several aircraft exceeded this altitude in zoom climbs but not in sustained flight.  That same day SR-71, serial number 61-7958 set an absolute speed record of 1,905.81 knots (2,193.2 mph; 3,529.6 km/h).

The SR-71 also holds the “Speed Over a Recognized Course” record for flying from New York to London distance 3,508 miles (5,646 km), 1,435.587 miles per hour (2,310.353 km/h), and an elapsed time of 1 hour 54 minutes and 56.4 seconds, set on 1 September 1974 while flown by U.S. Air Force Pilot Maj. James V. Sullivan and Maj.  Noel F. Widdifield, reconnaissance systems officer (RSO).  This equates to an average velocity of about Mach 2.68, including deceleration for in-flight refueling. Peak speeds during this flight were probably closer to the declassified top speed of Mach 3.2+. For comparison, the best commercial Concorde flight time was 2 hours 52 minutes, and the Boeing 747 averages 6 hours 15 minutes.

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From Wikipedia: 

When first seen in reconnaissance photography, the large wing planform suggested an enormous and highly maneuverable fighter.  This was during a period of time when U.S. design theories were also evolving towards higher maneuverability due to combat performance in the Vietnam War.  The appearance of the MiG-25 sparked off serious concern in the West, and prompted dramatic increases in performance for the McDonnell Douglas F-15 Eagle in late 1960s.

The capabilities of the MiG-25 were better understood in 1976 when Soviet pilot Viktor Belenko defected in a MiG-25 to the United States via Japan .  The large wing turned out to be due to the aircraft’s very heavy weight.

The first flight of the interceptor prototype, “Ye-155-P1“, took place on 9 September 1964.  Development of the MiG-25, which represented a major step forward in Soviet aerodynamics, engineering and metallurgy, took several more years to complete.

On 9 July 1967, the new aircraft was first shown to the public at the Domodedovo air show, with four prototypes (three fighters and a reconnaissance aircraft) making a fly past.

The Mikoyan-Gurevich design bureau soon realized that the performance of the new aircraft gave it great potential to set new flight records.  In addition to their normal duties, the prototypes Ye-155-P1, Ye-155-R1, Ye-155-R3 were made lighter by removing some unneeded equipment, and were used for these attempts.  Under Federation Aeronautique Internationale (FAI) classification the Ye-155 type belonged to class C1 (III), which specifies jet-powered land planes with unlimited maximum take-off weight.

Record set included:

  • on 31 August 1977,  “Ye-266M” flown by MiG OKB Chief Test Pilot Alexander V. Fedotov, set the recognized absolute altitude record for a jet aircraft under its own power.  He reached 37,650 metres (123,520 ft) at Podmoskovnoye, USSR in zoom climb (the absolute altitude is a different record than the sustained altitude in horizontal flight).  The aircraft was actually a MiG-25RB re-engined with the powerful R15BF2-300. It had earlier been part of the program to improve the aircraft’s top speed that resulted in the MiG-25M prototype.

In all 29 records were claimed, of which seven were all-time world records for time to height, altitudes of 20,000 m and higher, and speed.  Several records still stand.

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