Fifty-nine years ago this month, the USN/Douglas XA3D-1 Skywarrior prototype strategic bomber made its initial test flight at Edwards Air Force Base, California. Legendary Douglas test pilot George R. Jansen was at the controls of the swept-wing, turbojet-powered, carrier-based aircraft.
The USN/Douglas A3D Skywarrior was the product of late 1940’s Navy studies calling for a carrier-based, long range bomber capable of delivering a 10,000 lb bomb load. Douglas Aircraft Company was awarded a contract to manufacture and test a pair of XA3D-1 airframes (BuAer No. 125412 and No. 125413) in 1949. Westinghouse was selected as the powerplant provider.
The XA3D-1 had a design weight of roughly 68,000 lbs, which would allow the aircraft to operate from existing Navy aircraft carriers. Power was provided by a pair of Westinghouse J40 turbojets. Each of these powerplants generated 7,500 lbs of military thrust and 10,500 lbs of afterburner at sea level. Unfortunately, the XA3D-1 was underpowered with these powerplants. In any event, the J40 engine experienced significant development problems and never did see production.
The No. 1 XA-3D-1 (BuAer 125412) made its maiden flight on Tuesday, 28 October 1952 with Douglas test pilot George R. Jansen doing the piloting honors. Although a Navy program, the flight was conducted at Edwards Air Force Base in California. The safety provided by the presence of the world’s longest (11.5 miles) natural runway, Rogers Dry Lake, was one reason for doing so. The XA3D-1 initial test hop was unremarkable.
The results of early Skywarrior testing significantly aided the evolutionary development and improvement of the aircraft. The A3D-1 was the first Skywarrior variant to see limited production. This was ultimately followed by the A3D-2; considered by many to be the definitive Skywarrior. Large for a carried-based aircraft, the Skywarrior was nick-named “The Whale”.
The A3D-2 measured 76.3 feet in length and had a wing span of 72.5 feet. Wing leading edge sweep and planform were 36-deg and 812 square feet, respectively. The aircraft had a GTOW of 82,000 lbs versus a empty weight of 39,400 lbs. Power was provided by twin Pratt and Whitney J57-P-10 turbojets. Each powerplant generated 10,500 lbs of military thrust at sea level. Each engine could produce an additional 2,400 lbs of thrust using water injection.
The A3D-2 could carry a maximum conventional or nuclear bomb load of 12,800 lbs. Maximum unrefueled range was 1,826 nm. With a service ceiling of 41,000 feet, the aircraft typically cruised at 452 knots. Maximum airspeed was 530 knots. The A3D-2 flight crew consisted of a pilot, navigator and bombardier. Interestingly, the crew was not provided with ejection seats as a cost-saving measure. This led Skywarrior crews to asert that “A3D” was actually an acronym that meant “All 3 Dead”.
While the Skywarrior was designed as a strategic bomber, the aircraft was used in other roles over the course of its long operational life. Indeed, the Skywarrior was modified to serve in the electronic warfare role, as a photo-recon platform and as an aerial tanker. Historical records indicate that 282 Skywarriors were produced between 1956 and 1961.
The Skywarrior and its crews served faithfully throughout the Cold War period including Vietnam. Significantly, the Skywarrior holds the distinction of being the largest and heaviest aircraft ever to see operational service aboard an aircraft carrier. The last operational Skywarriors were taken out of the active inventory in September of 1991.
As a further tribute to the Skywarrior, the Air Force liked the aircraft so much that it contracted with the Douglas Aircraft Company to design, test and produce a very similar aircraft; the B-66 Destroyer. First flight occurred in June of 1954. Operationally, the B-66 was used primarily in the electronic warfare and recon roles. A total of 294 airframes were ultimately produced for the junior service. Happily, ejection seats were standard equipment.
Thirty-seven years ago this month, the first USAF/Rockwell B-1A multi-role strategic bomber was rolled-out at the contractor’s USAF Plant 42 facility in Palmdale, California. The swing-wing, supersonic aircraft was intended to replace the venerable USAF/Boeing B-52 Stratofortress.
The USAF/Rockwell B-1A Lancer was the product of 1960’s-era Air Force studies calling for a supersonic-capable, low-level penetration bomber. North American Rockwell was awarded a contract to manufacture and test four (4) prototype airframes (S/N’s 74-0158, 74-0159, 74-0160 and 76-0174) in 1970. General Electric was selected as the powerplant provider.
The B-1A was designed for both Mach 2.3 flight at 50,000 feet and Mach 0.85 flight at sea level. The aircraft was able to satisfy these requirements by virtue of several design features. Formost among these was the aircraft’s ability to adjust its wing sweep in flight. Coupled with its sleek, aerodynamically-efficient fuselage, this gave the aircraft very low wave drag. Another key element were the type’s quartet of General Electric F-101 turbofan engines which generated a total of 120,000 lbs of afterburner thrust at sea level. Thrust performance was optimized through the use of variable-geometry air intakes.
The B-1A measured 150.2 feet in length and featured a wing span that could be varied in flight from 136.7 feet (15-deg sweep) to 78.2 feet (67.5-deg sweep). Gross take-off and empty weights were 395,000 lbs and 115,000 lbs, respectively. Unrefueld range was 5,300 nm. The aircraft was designed to carry 75,000 lbs of nuclear and/or conventional ordnance internally and up to 40,000 lbs externally. Operationally, the B-1A’s four-man crew would consist of aircraft commander, pilot, offensive systems officer and defensive systems officer.
The No. 1 B-1A (S/N 74-0158) was rolled out for the public on Saturday, 26 October 1974. About 10,000 people attended this event which took place at Rockwell’s facility on USAF Plant 42 property in Palmdale, California. The big, white, sleek aircraft was visually stunning and bore a majestic presence. The media covered the event in some detail.
The No. 1 B-1A took-off for the first time from USAF Plant 42 on Monday, 23 December 1974. The flight test aircrew included Charles Bock, Jr. (aircraft commander), Col. Emil (Ted) Sturmthal (pilot) and Richard Abrams (flight test engineer). The aircraft’s landing gear was not retracted and wing sweep was not varied during this initial flight test. These systems were operated on the type’s second flight test which occurred on Thursday, 23 January 1975.
Each of the B-1A prototypes served a distinct role in the aircraft’s flight test program. The No. 1 aircraft (74-0158) was the flying qualities evaluation testbed. It flew 79 times (405.3 hours) and was the first B-1A to hit Mach 1.5 (Oct 1975) as well as Mach 2 (Apr 1976). Aircraft No. 2 (S/N 74-0159) evaluated structural loading parameters, flew 60 times (282.5 hours), and achieved the highest Mach number of any B-1A aircraft (Mach 2.22 on Oct 1978). Aircraft No. 3 (S/N 74-0160) amassed 138 flights (829.4 hours) as an offensive and defensive systems testbed. Aircraft No. 4 (76-0174) had a similar role in that it tested essentially operational versions of the offensive and defensive systems. It flew 70 times (378 hours).
The B-1A program was cancelled by the Carter Administration in June of 1977. While it never attained operational status, the aircraft broke new ground in mutiple areas including aircraft design, aerodynamics, flight performance, and electronic warfare. Indeed, the multiple technological capabilities that it pioneered were ultimately exploited in the type’s direct heir; today’s USAF B-1B Lancer.
Fifty-six years ago this month, the USAF/Republic YF-105A Thunderchief took to the air for the first time from Edwards Air Force Base. With Republic test pilot Russell M. Roth at the controls, the fabled Thud exceeded the speed of sound during its maiden flight.
The USAF/Republic F-105 Thunderchief was a member of the fabled Century Series of jet-powered production aircraft. It was designed specifically as a fighter-bomber capable of delivering nuclear ordnance. Famed Republic aircraft designer Alexander Kartveli is credited with creation of the F-105 airframe.
The Thunderchief was a big airplane. The original version (YF-105A) measured 61.5 feet in length and featured a wing span of 35 feet. Gross take-off and empty weights were 40,561 lbs and 28,966 lbs, respectively. Power was provided by a single Pratt and Whitney J57-P-25 turbojet which produced 15,000 lbs in afterburner thrust at sea level.
The YF-105A was designed to have a maximum speed of 778 mph at sea level and a maximum speed at 36,000 feet of 857 mph. The aircraft had a combat ceiling of 49,950 feet and could carry an ordnance load of about 8,000 lbs. With an internal fuel load of 850 gallons, the aircraft could fly 878 nm. Range was increased to 2,364 nm with the addition of 1,870 gallons carried externally.
The first YF-105A Thunderchief (S/N 54-0098) made its maiden flight on Saturday, 22 October 1955. This initial test hop was conducted at Edwards Air Force Base, California, with Republic test pilot Russel M. Roth doing the piloting honors. Despite a high level of transonic drag resulting from the lack of fuselage area-ruling, the aircraft hit Mach 1.2 on its first time in the air.
The Thunderchief entered the USAF inventory in May of 1958 as the F-105B. A number of variants followed in the years that followed. The F-105D was the definitive single-seater version. The F-105F served as a combat-capable trainer. The F-105G was also a two-seater and flew the Wild Weasel mission.
Performance of the later versions of the Thunderchief significantly exceeded that of the YF-105A. For example, the F-105D Thunderchief was powered by a Pratt and Whitney J75-P-19W turbojet that produced 24,500 lbs of thrust in afterburner. The engine was fed by side-mounted, variable-geometry, forward-swept air intakes that were more efficient than the original design. Further, the fuselage employed area-ruling to reduce transonic wave drag. Taken together, these changes gave the Thunderchief a Mach 2+ capability.
The F-105D had a gross take-off weight of 52,546 lbs carrying a 14,000 lb conventional ordnance load-out. Empty weight was 27,500 lbs. The aircraft’s small wing area (385 square feet) resulted in a very high wing loading. While this permitted very stable flight during the high-speed, low-altitude run-in to the target, the Thunderchief was no match for the agile MIG-17 flown by the North Viet Nam Air Force. Notwithstanding, the Thunderchief had 27.5 air victories against the North Vietnamese compared to 17 losses to the enemy.
Republic Aircraft manufactured a total of 833 copies of the Thunderchief by the time production ended in 1964. Viet Nam was the Thunderchief’s war. Over 20,000 sorties were flown by Thunderchief aircrews. Many of these missions were flown into the Pack VI region of the air war over North Viet Nam. A total of 382 Thunderchief aircraft were lost during the air war. This inordinately-high loss rate was largely due to the shackling and politically-motivated rules of engagement enforced by the Johnson Administration.
The F-105 no longer graces the skies. However, one can see the aircraft on display at a number of air museums throughout the country. The National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, OH is one such example.
In its time, the Thunderchief was a mighty performer and particularly loved by its pilots. Many books have been written by those who flew “The Thud” into hostile skies. These personal accounts are quite inspiring and often poignant. To get a sense of what it was like to fly and fight in the Thunderchief, Jack Broughton’s “Thud Ridge” is an unforgettable read.
Fifty-two years ago this month, the USAF Bold Orion air-launched ballistic missile performed a successful intercept of the Explorer VI satellite. This event marked the first time in history that a endoatmospherically-launched missile intercepted a target vehicle in space.
Bold Orion was a 1950’s-era air-launched ballistic missile (ALBM) prototype developed by Martin Aircraft for the United States Air Force (USAF). It was part of USAF’s Weapons System 199 (WS-199) research and development program. The goal of WS-199 was to develop technology to be used in emerging strategic weapons systems by the Strategic Air Command (SAC).
The Bold Orion was developed using components obtained from existing missile systems as a cost savings measure. The missile was initially configured as a single stage vehicle. Power was provided by a Thiokol TX-20 Sergeant solid rocket motor. However, preliminary flight tests showed that the vehicle lacked sufficient kinematic performance. The addition of an ABL X-248 Altair solid rocket motor made Bold Orion a two-stage vehicle.
The two-stage Bold Orion configuration was 37 feet in length and had a maximum diameter of 31 inches. The vehicle was air-launched from a USAF/Boeing B-47 Stratojet aircraft. Missile launch occurred while the carrier aircraft executed a zoom climb maneuver. The option was available to fly either a maximum range endoatmospheric mission (about 1,000 nm) or achieve exoatmospheric altitudes as high as 150 nm.
The Bold Orion flight test program consisted of a dozen missions. The first six of these were single-stage vehicles which were flown between May and November of 1958. The remaining rounds were two-stage configurations which were tested between December of 1958 and October of 1959. All missions were air-launched off the coast of Florida and flown down the Eastern Test Range.
Bold Orion’s grandest moment came on the occasion of its final flight. The goal was to test the vehicle’s ability to perform in the anti-satellite (ASAT)role. The Explorer VI satellite served as the mission target. A direct hit was not required since an actual interceptor would be configured with a nuclear warhead. In that scenario, detonation of the warhead within several miles of the target would be sufficient to destroy it.
Bold Orion’s ASAT mission occurred on Tuesday, 13 October 1959. Launch took place within the Atlantic Missile Range Drop Zone (AMR DZ). The altitude, latitude and longitude of the drop point were 35,000 feet, 29 deg North and 79 deg West, respectively. Bold Orion successfully intercepted the Explorer 6 satellite, passing its target at a range of less than 3.5 nm and an altitude of 136 nm.
The Bold Orion ASAT test marked the first interception of a satellite in space and verified the feasibility of an ASAT system. However, negative political ramifications came along with technical success. Specifically, the Eisenhower Administration intended to keep space neutral. Bold Orion’s overtones of hostile intent did not play well with that mandate. As a result, ASAT development within the United States was halted not long after Bold Orion’s final mission.
Bold Orion’s success gave USAF the flight experience and technology to develop the Skybolt ALBM. Known as GAM-87, this two-stage missile sported a W59 thermonuclear warhead with a yield of 1.2 megatons. A quartet of pylon-mounted Skybolt missiles would be carried by and air-launched from a USAF/Boeing B-52H Stratofortress. While Skybolt’s kinematic performance was impressive, test problems and the development of the Submarine-Launched Ballistic Missile (SLBM) ultimately led to its cancellation.
Fifty-five years ago this month, the first Jupiter-C launch vehicle flew a suborbital mission in which it attained a maximum velocity of 16,000 mph. The successful flight test was a significant step in the development of what would ultimately result in the United States’ first satellite launcher.
The Jupiter-C was a derivative of the Army’s Redstone Short Range Ballistic Missile (SRBM). It was designed to test sub-scale models of the warhead reentry vehicle used by the Jupiter Intermediate Range Ballistic Missile (IRBM). The “C” in Jupiter-C stood for Composite Reentry Test Vehicle.
The Jupiter-C launch vehicle was composed of three (3) separate stages. The vehicle measured 68.5 feet in length and had a maximum diameter of 70 inches. Lift-off weight was 62,700 lbs. All Jupiter-C launches took place from LC-5 and LC-6 at Cape Canaveral, Florida.
The Jupiter-C first stage was a Redstone missile stretched by 8 feet to allow for increased propellant load capability. Power was provided by a single Rocketdyne A-7 liquid rocket engine that burned alcohol and liquid oxygen as propellants. The A-7 produced 78,000 lbs of thrust for about 150 seconds.
The Jupiter-C second and third stages consisted of clusters of Baby Sergeant solid rocket motors. Specifically, the second stage clustered eleven (11) of these motors that generated a total thrust of 16,500 lbs for 6 seconds. The third stage utilized a cluster of three (3) Baby Sergeants that produced a total thrust of 4,500 lbs for 6 seconds. Propellants for the solids included polysulfide-aluminum and ammonium perchlorate.
The second and third stage solid rocket motors were housed in a large cylinder that sat atop the first stage. This cylinder (referred to as the “tub”) was spun at a rotational velocity that varied from 450 to 750 RPM in flight. The purpose in doing so was to mitigate the effects of thrust misalignments and provide gyroscopic stability during the firing periods of the second and third stage solid rocket motor clusters.
The kinematic performance capability of the Jupiter-C was such that it could readily put a payload in orbit given a fourth stage. However, the State Department strictly forbade any attempt to orbit a satellite with the Jupiter-C. Even if that were to happen “accidentally”. The philosophy at the time was that America’s first satellite would be orbited using a non-military booster.
The first Jupiter-C was launched from LC-5 at Cape Caneveral, Florida on Wednesday, 19 September 1956. Launch time was 05:47 UTC. (For the record, we note here that some historical sources quote the launch date as being Thursday, 20 September 1956.) The vehicle did not carry a scaled Jupiter nose cone test article, but a dummy fourth stange and about 20 lbs of instruments in its stead.
The kinematic performance of the first Jupiter-C was impressive. The vehicle reached a speed of 16,000 mph (1,500 mph less than orbital requirement) at third stage burnout. Impact occurred in the Atlantic Ocean roughly 2,861 nm downrange of the launch site. Apogee for the suborbital flight was 593 nm.
There were only two more Jupiter-C test flights after the inaugural mission. These occurred on Wednesday, 15 May 1957 and Thursday, 08 August 1957, respectively. Each vehicle carried a scaled Jupiter nose cone test article. Surface temperatures exceeded 2,000 F and the ablative thermal protection system worked remarkably well. So much was learned from these missions that further Jupiter-C flights were deemed unnecessary.
The addition of a live fourth stage rocket motor to the Jupiter-C was known as Juno I. Indeed, using a single Baby Sergeant solid rocket motor and a small scientific payload constituted the Explorer I satellite. History records that Explorer I was orbited by a Juno I launch vehicle on Friday, 31 January 1958. Significantly, it was the first satellite to be orbited by the United States.
Sixty-three years ago this week, the USAF/Convair XF-92A Dart made its first official flight from Muroc Army Airfield in California. Convair test pilot Ellis D. “Sam” Shannon was at the controls of the experimental delta-winged aircraft.
The XF-92A Dart holds the distinction of being the first delta-winged, turbojet-powered aircraft in the United States. It was designed and produced by the Consolidated Vultee Aircraft (Convair) Company for the United States Army Air Force. Only one copy of the type (S/N 46-682) was ever built and tested.
At the time, the delta wing planform was something of a novelty. Convair designers chose this shape principally due to its aerodynamics benefits. For example, transonic wave drag is significantly lower than that of a swept wing of equal area. The delta wing also exhibits favorable lift-curve slope, center-of-pressure travel and ground effect characteristics.
The large chord of a delta-winged aircraft allows for static pitch stability to be realized without the use of a classic horizontal tail. Pitch control is obtained via wing trailing edge-mounted elevons; surfaces which combine the functions of an elevator and the ailerons. When differentially-deflected, elevons provide roll control.
The XF-92A measured 42.5 feet in length and had a wing span of 31.33 feet. Empty and gross weight were 9,978 lbs and 14,608 lbs, respectively. Early in its development, the XF-92A was powered by an Allison J33-A-21 turbojet which generated a maximum thrust of only 4,250 lbs. The final version of the aircraft was configured with an Allison J33-A-16 turbojet which produced a maximum sea level thrust of 8,400 lbs.
The XF-92A made its maiden flight on Saturday, 18 September 1948 from Muroc Army Airfield, California. Convair test pilot Ellis D. “Sam” Shannon did the piloting honors. Although the aircraft handled well, it was a bit over-responsive to control inputs. In addition, the XF-92A was underpowered.
Convair completed the last of 47 Phase I test flights on Friday, 26 August 1949. The Air Force conducted the first Phase II flight test on Thursday, 13 October 1949 with none other than Major Charles E. “Chuck” Yeager at the controls. Phase II testing was completed on Wednesday, 28 December 1949 by USAF Major Frank K. “Pete” Everest.
Following Phase II testing, the aircraft was re-engined with an Allison J33-A-29 turbojet capable of generating 7,500 lbs of sea level thrust. The Air Force continued to fly the XF-92A on various and infrequent test missions into February of 1953. Pilots of historical note who flew the aircraft include Al Boyd, Kit Murray, Jack Ridley, Joe Wolfe and Fred Ascani. It appears that the Air Force flew a total of 47 flight tests using the XF-92A.
The lone XF-92A was turned over to the National Advisory Committe For Aeronautics (NACA) once the Air Force was done testing it. The aircraft was promptly configured with an Allison J33-A-16 turbojet that generated 8,400 lbs of sea level thrust. NACA test pilot A. Scott Crossfield flew the XF-92A a total of 25 times. The type’s last flight occurred on Wednesday, 14 October 1953.
The XF-92A was not all that great from a piloting standpoint. Among other things, the aircraft had a severe pitch-up problem which produced normal accelerations between 6 and 8 g’s. The XF-92A was also plagued with landing gear failure problems. As noted previously, the aircraft was underpowered; a situation that was not uncommon for jet-powered aircraft of the era.
Inspite of its flaws, the design and flight experience gained from the XF-92A’s development led to an extensive series of delta-winged highly-successful aircraft produced by Convair in the 1950’s. These historically-significant aircraft include the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, XF2Y Sea Dart and XFY Pogo.
Sixty-years ago this month, a live biological payload consisting of a primate and a colony of mice was lofted to an altitude of 236,000 feet by a two-stage Aerobee X-8 sounding rocket. The mission marked the first recorded instance where a mamallian payload survived the rigors of high altitude rocket flight.
The post-World War II period saw a rapid expansion in America’s efforts to explore space. Emphasis was placed on flying faster and higher. Rocket power led the way. First, into the upper atmosphere, and ultimately into the lower reaches of space.
Early post-war flight research capitalized on using V-2 rockets captured from the defeated Third Reich. These vehicles were brought to America and adapted to boost instruments to high altitude. While servicable in this new role, the V-2 was less than ideal from the standpoints of launch, performance and payload recovery.
In light of the above, a variety of purpose-built rocket systems rapidly came into being during the post-war years. Prominent among these was the Aerobee high altitude sounding rocket. Aerojet General initiated development of the system in 1946. The first Aerobee test vehicle was flown in November of 1947 at White Sands proving Grounds (WSPG).
The first Aerobee configuration was about known as the X-8. It consisted of a solid propellant booster and a liquid sustainer. The booster generated 18,000 lbs of thrust for 2.5 seconds. Sustainer propellants included aniline and furfuryl-alcohol (fuel) and red fuming nitric acid (oxidizer). The sustainer rocket engine produced 2,600 lbs of thrust for 40 seconds.
The X-8 launch vehicle measured 26.4-feet in the length with a launch weight of about 1,100 lbs (including 150-lb payload). The sustainer stage was a little more than 20-feet in length and 15-inches in diameter. The launch weight of the booster was roughly 50 lbs more than that of the sustainer.
The X-8 was launched from a 143-foot tower which was typically canted 3-degrees off of the vertical. Booster burnout occurred at 950 ft/sec and 1,000 feet above the ground. Sustainer burnout took place at 4,420 ft/sec and an altitude of 17-nm. Apogee was on the order of 66-nm.
The Aerobee carried a variety of scientific instruments to probe the atmospheric and space environments. Measurements were made of high altitude thermodynamic properties, winds, radiation and magnetic fields. The Aerobee Program also provided a wealth of information regarding vehicle aerodynamics, flight dynamics and dispersion.
The Aerobee was also used to loft live biological payloads into near space. At the time this flight research began in the late 1940’s/early 1950’s, very little was known about the effects of high altitude rocket flight on living organisms. A variety of small animals were used as test subjects including primates, mice, and insects. The data obtained from these animal flights were ultimately used to safely launch men into space.
History records that it was not all that easy to rocket animals into space and have them survive the experience. Animals died either due to the rigors of rocket flight, launch vehicle failure or recovery system malfunction. Sometimes everything worked, but an animal died due to heat exhaustion when recovery crews could not extract it from the downed payload section soon enough. It would take over 3-years of flight experience before success was achieved.
The great day came on Thursday, 20 September 1951. An Aerobee X-8 RTV-A1 served as the launch platform. The live biological payload consisted of a monkey named Yorick and a colony of eleven (11) mice. The launch took place at 15:31 UTC from Holloman Air Force Base, New Mexico. The X-8 carried the monkey and mice payload to an apogee of 236,000 feet. The parachute recovery system finally worked. Recovery was also successful.
Many more successful Aerobee animal flights took place in the ensuing years. Even as Aerobee rocket performance increased significantly as numerous variants of the X-8 were developed over the life of the program. Indeed, almost 1,100 payloads were lofted into the realms above by the time the Aerobee was taken out of active service in 1985.
Fifty-two years ago this week, the United States Air Force successfully conducted an Initial Operational Capability Demonstration (IOC DEMO) of the Atlas D Intercontinental Ballistic Missile (ICBM). The Atlas Missile System was pronounced operational following the successful launch from Vandenberg Air Force Base, California.
Named for the superhuman strongman of Greek mythology, Atlas was the United States’ first operationally deployed intercontinental ballistic missile (ICBM). Program roots go back to 1946 when Consolidated Vultee Aircraft (Convair) was awarded a study contract by the United States Army Air Forces for a 1,500 to 5,000 mile range missile that could carry a nuclear warhead.
At the time Convair began its study, no missile within conception could carry even the smallest nuclear warhead available at the time. However, a confluence of technological developments in the early 1950’s led to Atlas becoming a high priority development within the United States defense community. First, the thermonuclear weapon was successfully demonstrated. Second, a design breakthrough occurred wherein nuclear warhead mass was sharply reduced. Finally, CIA activities revealed that the Soviet Union was making significant progress with their own ICBM program.
Atlas A, B and C were the initial test and development variants of America’s first ICBM. Atlas D was the first operational version. Configured with a Mark 2 reentry vehicle, it measured 75 feet in length and 10 feet in diameter. Atlas D weighed 255,000 lbs at launch and had a range of 10,360 miles.
The Atlas propulsion system consisted of a single Rocketdyne LR105 sustainer (57,000 lbs thrust) and a pair of Rocketdyne LR89 boosters (150,000 lbs thrust each). Roll control and fine velocity control was provided by a pair of Rocketdyne LR101 vernier rocket engines (1,000 lbs thrust each).
The Atlas sustainer rocket engine was mounted between the outboard booster rocket engines. This trio of rocket engines was ignited at launch. While the boosters were jettisoned around 130 seconds into flight, the sustainer core continued to fire until propellant exhaustion. This unique arrangement made Atlas a stage-and-a-half launch vehicle.
In striving for the minimum weight solution, the Atlas airframe included propellant tankage constructed of very thin stainless steel. This so-called “balloon tank” design required internal pressurization with nitrogen gas at about 5 psig to provide structural rigidity. An Atlas launch vehicle would simply collapse under its own weight if not so pressurized.
Atlas A, B, C and D variants employed radio guidance. That is, the missile sent position information from its guidance system to the ground via radio. In turn, the ground sent course correction information back to the missile. Starting with the Atlas E, the guidance system was entirely autonomous.
On Wednesday, 09 September 1959, the Strategic Air Command (SAC) conducted an Initial Operational Capability Demonstration (IOC DEMO) launch at Vandenberg Air Force Base, California. The Atlas D 12D launch vehicle lifted-off from Launch Complex 576-A2 at 17:50 UTC. Its Mark II reentry vehicle flew 4,480 nautical miles downrange and landed less than 1 nautical mile from its target near Wake Island. Apogee and maximum speed were 972 nautical miles and 16,000 mph, respectively.
The Atlas IOC DEMO mission was entirely successful. General Thomas D. Power, SAC Commander-in-Chief, was so impressed with the results of the flight that he immediately declared the Atlas System to be operational.
The Atlas missile ultimately stood sentinel at 11 separate launch sites located throughout the United States. Roughly 350 Atlas missiles were manufactured during the program’s lifetime, with a maximum of 129 missiles being deployed at any one time being 129. However, the introduction of the famous Minuteman missile in 1963 sounded the death knell for Atlas. Indeed, there were no more operational Atlas missiles after April of 1965.
Although its operational service life was somewhat brief, Atlas provided a proving ground for a multiplicity of emerging missile technologies. Further, Atlas development served as the organizational and procedural template for all future ICBM programs.
Following retirement from active ICBM service, depostured Atlas ICBM’s were converted to the space launch role. It was employed for nearly a quarter of a century in such capacity. Indeed, all Mercury Earth-orbital missions were launched using man-rated Atlas launch vehicles.
The Atlas is still active in the US launch vehicle inventory. Although now manufactured by Lockeed-Martin and having a configuration quite distinct from that of its ICBM forbears, the latest version of the venerable vehicle is the Atlas V. This modern Atlas variant can send nearly 65,000 lbs of payload into LEO and 29,000 lbs into GTO.
Fifty-five years ago this week, the USAF/Boeing KC-135A Stratotanker took to the skies for the first time. The jet-powered aircraft would go on to become the most famous military tanker in the history of aviation.
The KC-135A Stratotanker was a derivative of the famous Boeing Model 367-80. The type was the only jet-powered aircraft designed specifically for the aerial refueling mission. As such, it replaced the older and slower propeller-driven KC-97 Stratotanker. For the first 15 years of its operational life, the KC-135 was the only tanker flown by the Strategic Air Comman (SAC).
The KC-135A measured 136.25 feet in length and had a wingspan of 130.8 feet. Gross take-off weight and empty weight were 297,000 lbs and 109,000 lbs, respectively. Four (4) wing pylon-mounted Pratt and Whitney J57-P-59W turbojets provided a sea level thrust of 58,000 lbs in afterburner. The aircraft was designed to have an unrefueled range of 4,000 miles, a cruise speed of 552 mph and an operational ceiling of 40,000 feet.
Jet fuel was carried internally within six (6) wing tanks and four (4) fuselage tanks. All but 1,000 gallons of this fuel could be pumped to the receiver aircraft via an extendable boom located at the rear of the tanker. The KC-135 boom operator would lie in a prone position and actually flew the boom into the receiving aircraft’s fuel receptacle.
On Friday, 31 August 1956, the first KC-135A Stratotanker production aircraft made its maiden flight from the Boeing airfield at Renton, Washington. Known as the “The City of Renton”, this aircraft was the first of 820 KC-135 aircraft that Boeing would ultimately produce. Roughly 90 percent of these production aircraft were true tankers while the remainder were employed as cargo transports and flying command posts.
The service that the KC-135 has provided to our nation’s aerial warfighters has truly been astounding. For example, during nine years of the Vietnam conflict, KC-135s made 813,000 aerial refuelings of combat aircraft. In support of the Persian Gulf conflict, KC-135 tankers made 18,700 hookups and transferred 278,000,000 lbs of fuel.
The KC-135 has evolved into numerous variants over the course of its long operational life. A variety of modifications have extended the service life of the KC-135 into its sixth decade. Key upgrades include reskinning the wings with an improved aluminum alloy and more powerful and fuel-efficient CFM-56 turbofans. Total sea level thrust is more than 90,000 lbs in afterburner.
As a tribute to this venerable aircraft, her designers and her flight crews, we note here that the KC-135 Stratotanker remains the primary USAF aerial refueling aircraft to this very day.
Fifty-seven years ago this month, USAF Major Arthur W. “Kit” Murray set a new world altitude record of 90,440 feet in the rocket-powered Bell X-1A. In doing so, Murray reported that he could detect the curvature of the Earth from the apex of his trajectory.
The USAF/Bell X-1A was designed to explore flight beyond Mach 2. The craft measured 35.5 feet in length and had a wing span of 28 feet. Gross take-off weight was 16,500 pounds. Power was provided by an XLR-11 rocket motor which produced a maximum sea level thrust of 6,000 lbs. This powerplant burned 9,200 pounds of propellants (alcohol and liquid oxygen) in about 270 seconds of operation.
Similar to other early rocket-powered X-aircraft such as the Bell XS-1, Douglas D-558-II, Bell X-2 and North American X-15, the X-1A flew two basic types of high performance missions. That is, the bulk of the vehicle’s propulsive energy was directed either in the horizontal or in the vertical. The former was known as the speed mission while the latter was called the altitude mission.
On Saturday, 12 December 1953, USAF Major Charles E. “Chuck” Yeager flew the X-1A (S/N 48-1384) to an unofficial speed record of 1,650 mph (Mach 2.44). Moments after doing so, the X-1A went divergent in all three axes. The aircraft tumbled and gyrated through the sky. Control inputs had no effect. Yeager was in serious trouble. He could not control his aircraft and punching-out was not an option. The X-1A had no ejection seat.
Chuck Yeager took a tremendous physical and emotional beating for more than 70 seconds as the X-1A wildly tumbled. His helmet hit the canopy and cracked it. He struck the control column so hard that it was physically bent. His frantic air-to-ground communications were distinctly those of a man who was convinced that he was about to die.
As the X-1A tumbled, it decelerated and lost altitude. At 33,000 feet, a battered and groggy Yeager found himself in an inverted spin. The aircraft suddenly fell into a normal spin from which Yeager recovered at 25,000 feet over the Tehachapi Mountains situated northwest of Edwards. Somehow, Yeager managed to get himself and the X-1A back home intact.
The culprit in Yeager’s wide ride was the then little-known phenomenon identified as roll inertial coupling. That is, inertial moments produced by gyroscopic and centripetal accelerations overwhelmed aerodynamic control moments and thus caused the aircraft to depart controlled flight. Roll rate was the critical mechanism since it coupled pitch and yaw motion.
In the aftermath of Yeager’s near-death experience in the X-1A, the Air Force ceased flying speed missions with the aircraft. Instead, a series of flights followed in which the goal was to extract maximum altitude performance from the aircraft. USAF Major Arthur W. “Kit” Murray was assigned as the Project Pilot for these missions.
On Thursday, 26 August 1954, Kit Murray took the X-1A (S/N 48-1384) to a maximum altitude of 90,440 feet. This was new FAI record. Murray also ran into the same roll inertial coupling phenomena as Yeager. However, his experience was less tramatic than was Yeager’s. This was partly due to the fact that Murray had the benefit of learning from Yeager’s flight. This allowed him to both anticipate and know how to correct for this flight disturbance.
Murray’s achievement in the X-1A meant that the X-1A held the records for both maximum speed and altitude for manned aircraft. It did so until both records were eclipsed by the Bell X-2 in September of 1956.
Kit Murray was a highly accomplished test pilot who never received the public adulation and notoreity that Chuck Yeager did. He retired from the Air Force in 1960 after serving for 20 years in the military. Murray went on to a very successful career in engineering following his military service. Kit Murray lived to the age of 92 and passed from this earthly scene on Monday, 25 July 2011.
