Aerofax Datagraph 3
BeIIX-1 Variants •
By Ben Guenther and Jay Miller ISBN 0-942548-40-X
X-1 SECOND GENERATION GENERAL ARRANGEMENT ©1988
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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.
De-icing Fluid Tank 22. Canopy 23. Oxygen Filler 24. Lox Tank 25. Nitrogen Filler 26. External Power Receptacle 27. Hydrogen Peroxide Filter Hydrogen Peroxide Tank Lox Filler Fuel Tank Fuel Filler Turbine Pump Pick-Axe Antenna XLR11·RM-S Motor ANfAPN-60 Antennas AN/APN-60 Radar Installation Pitol Tube Tube Bundles (Nitrogen) Main Wheel Door Actuator Air Bollie Main Wheel Door Actuator Air Bottle Filler 21. AN/AAC-5 Radio Installation
Stor.k No. 0303
ABBREVIATIONS AND ACRONYMS: AAF AB AF AFB AH ARDC ASD g.
NACA NASA PARD PSI RMI tIc tho
USAF VHF X
Army Air Force Air Base Air Force Air Force Base Amp Hour Air Research and Development Command Aeronautical Systems Division Gravity National Advisory Committee for Aeronautics National Aeronautics and Space Administration Pilotless Aircraft Research Division Pounds per Square Inch Reaction Motors, Inc. Thickness/Chord Ratio Thrust United States Air Force Very High Frequency Experimental
THE BELL X·1 VARIANTS STORY
The second X-I, 46-063, during final assembly inside Bell's Niagara Falls, New York facilily, during late 194~. The wing~ with a thickness/chord ratio of 8%, and its associated center section, later were swapped with the 10% wmg of the flfsl X-I, 46-062, pnor to the latter s hlslonc flfst supersonic flight on October 14, 1947. With the exception of their wings and serial numbers, when compfeted, 46-062 and 46-063 were externally, Virtually Identical.
leading edge and all changes in velocity and pressure take place quite sharply and SUddenly. The airflow ahead is not influenced until the air molecules SUddenly are forced out of the way by the concentrated pressure wave set up by the actual object. Simply stated, compressibility anomalies occur at those speeds which approach or exceed the speed of sound. This velocity, in turn, is defined as the speed at which small pressure disturbances will be propagated through the air-which in turn is solely a function of air temperature. The accompanying table illustrates speed of sound variations in the standard atmosphere:
CREDITS: The authors and Aerofax, Inc. would like to express our thanks to the many individuals who contributed to this detailed description of the Bell X-1 research aircraft family. Three people who were particularly helpful in 3ssisting us under the auspices of Bell Aerospace [extron include Eddie Marek, Stanley Smolen, and Bob 3herwood. Eddie's Willingness to pull and file rare original legatives, and Bob's willingness to let him do it, provided the final contribution assuring the publication of this book. Stan's support and assistance gave Eddie the boost needed to persevere while digging. Because of the efforts of these three individuals, much of the imagery seen on the pages of this book has been released for pUblic consumption for the first time. Others whose efforts on our behalf won't soon be lorgotten include David Anderton, Bill Beavers, 'Joe Cannon, Bob and Gloria Champine (the latter of NASA Langley), Robert Cooper, Richard Forest (special thanks), Elaine Heise (Bell Aerospace Textron), Wes Henry (USAF Museum), Cheryl Hortel (Office of History, Edwards AFB), Alvin "Tex" Johnston; Helen Lapp (special thanks); Dave Menard; Robert Perry (RAND Corp.); Terrill Putnam (NASA Dryden); Michael Rich (RAND Corp.); Mick Roth; Sue Seward, Stanley Smith (special thanks); Tom Vranas (NASA Langley); and Lucille Zaccardi (retired from the Edwards AFB History Office). For another perspective on the X-1 story, Aerofax, Inc. highly recommends Richard Hallion's Supersonic Flight (the MacMillan Co., NY, 1972). And for a detailed description of the rest of the X-series aircraft, the pUblisher also recommends author Jay Miller's The X-Planes, X-I to X-31 (Aerofax, Inc., TX, 1988).
PROGRAM HISTORY: As an object moves through the air mass, velocity and pressure changes occur which create pressure disturbances in the airflow surrounding the object. Traveling at the speed of sound, these pressure disturbances are propagated through the air in all directions, extending indefinitely. If the object is traveling at low speed, the pressure disturbances primarily are propagated ahead of Ihe object and the oncoming airflow thus is influenced by the pressure field being generated. Once an object approaches sonic velocity, this scenario dramatically changes. There now is no warning for oncoming air molecules that the object is about 10 pass through. The oncoming air molecules cannot be influenced by a pressure field because none exists ahead. Thus, as flight speed nears the speed of sound, a compression wave (shock wave) is formed at the
Variation of Temperature and Speed of Sound With Altitude in the Standard Atmosphere Altitude
Ft. Sea level 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 50,000 60,000
• F. 59.0 41.2 23.3 5.5 -12.3 -30.2 -48.0 -65.8 -69.7 -69.7 -69.7
·C. 15.0 5.1 - 4.8 -14.7 -24.6 -34.5 -44.4 -54.3 -56.5 -56.5 -65.5
Speed of Sound Knots 661.7 650.3 638.6 626.7 614.6 602.2 589.6 576.6 573.8 573.8 573.8
Thus it is that all compressibility effects depend upon the relationship of airspeed to the speed of sound. It is important to note that Ernst Mach (pronounced "Mahk"), a nineteenth century Austrian physicist and mathematician, became the first to enunciate the mathematical theory dealing with airflow. This theory assigned a numerical value to the ratio between the speed of a solid object through a gas (or space) and the speed of sound through that same medium. This became known as "Mach number"-with Mach 1 being equivalent to the speed of sound and with anything more or less than Mach 1 being given in terms of a percentage (i.e..85 Mach would be 85/100ths the speed of sound; Mach 2 would be twice the speed of sound; etc.). Today, Mach is the generally accepted term used to quantify supersonic speeds. By the beginning of WWII, aerodynamicists, structural engineers, powerplant designers, and numerous pilots had concluded that the science of flight was faced with an insidious aerodynamic hurdle of truly staggering implications. For the first time ever, compressibility phenomenon (also later referred to as the "transonic barrier" or "sound barrier"), a dynamic gaseous event wherein air molecules compress into a seemingly im· penetrable wall in front of an aircraft's wings and fuselage (and, as it were, spinning propeller blade leading edges) when it nears Mach 1, had raised its serpentine head. During the late 1930s and very early 1940s, new high·
Rarely seen view of all three first-generation Bell X-I s under construction inside the Bell plant during late 1945. The aircraft on the left is 46-062, the one m the middle IS 46-064, and the one on the far nght IS 46-063. The forward fuselage section of 46-062 has been rotated 90° in its support crade.
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Early NACA Generic Supersonic Aircraft Studie:
One of the first Bell design studies, dated early 1945, illustrating what was to become the Model 44, and later, the X-I. Noteworthy are the dual-wheel-and-tire main landing gear, the side-opening canopy, and the unfaired XLRII combustion chambers.
A I/Bth-scale subsonic wind tunnel model representing the X-I as it eventually would be built. Of particular interest is the extended landing gear configuration and the diminutive, rarely-seen, lift dumping upper-wing-surface spoilers.
performance pursuit (as they then were called) aircraft, such as the U.S. Army Air Force's Lockheed P-38 Lightning and Republic P-47 Thunderbolt, capable of achieving Mach numbers approaching. 75 in a dive, had begun to enter the operational inventories of the world's military flying services. Their speed capabilities were close enough to sonic velocity and its associated compressibility phenomenon to cause serious, and sometimes irreversible buffet, structural overload, control, and stability problems. Already compressibility's associated loss of control and resultant occasional catastrophic structural failures had led to the deaths of several pilots. It had become painfully obvious to the world aviation community that, unless something was done to eliminate or circumvent the problem, more deaths soon would follow. Because research tools during the 1930s and early 1940s were limited in capability and technology, compressibility was not an easily understood phenomenon. Wind tunnel data, so commonplace as a means of predicting aircraft performance and flight characteristics today, almost was non-existent in the speed and dynamics regime encompassed by transonic and supersonic aircraft design, and only bullets then were known to be capable of stabilized "flight" at speeds in excess of sonic velocity. Supersonic phenomena, which occurred beyond the speed of sound, also were little understood. Such things as wave drag, high-speed flutter, "shock stall", centerof-pressure shift, the affect of supersonic speeds on interference drag, and the static and maneuvering load anomalies associated with supersonic flight were mysterious, and at times frightening unknowns. There even was concern over the possibility that something beyond prediction might occur-no human being had flown supersonically and lived, and no one knew for certain what strange and potentially disastrous' surprises awaited the first to explore. Over a period of several years, the phrase "sound barrier" came to describe the invisible...