The Bell X-2 "Starbuster"

The Bell X-2 was the fastest X-plane yet-aiming for Mach 3-but it was also one cantankerous beast. The program began in late 1945, but powered flights didn't begin until a decade later. In the interim, there were delays with the Curtiss-Wright XLR-25 throttleable, 15,000-lb. thrust rocket engine. The 2 aircraft built completed a total of 20 flights: 7 glide and 13 powered (6/27/52- 9/27/56). The X-2 was 37 ft 10 in long, with a wingspan of 32 ft 3in; gross weight was 24,910 lbs; empty weight, 12,375 lbs. NASA Photo.

During a ground test run of the XLR-25 engine, you can see technicians and engineers in shirtsleeves behind simple barricades VERY CLOSE to the X-2. This was very dangerous, because as the X-15 would prove years later, rocket engines could easily blow up during ground tests. Bell Photo.

The X-2's landing gear initially consisted of a small nosewheel, a retractable belly skid, and little retractable skis under each wing. But as was typical for X-Planes, the X-2's designers had made the gear as lightweight as possible, and unfortunately, that led to a number of problems and failures in the early days of the test program. NASA Photo.

The X-2's cockpit was very small, even by X-plane standards. Iven Kincheloe found himself wedged in so tightly that his helmet could barely move without bumping into the canopy. The panel was so small that special guages had to be made to fit. Bell Photo.

This diagram, in addition to showing the cockpit capsule layout, gives you an idea how small the X-2's cockpit was. Iven Kincheloe, the tallest X-2 pilot, once joked, "I just won't rattle around as much." Bell Image.

June 27, 1952: On its first glide flight, with Bell factory test pilot Jean "Skip" Ziegler at the controls, the X-2's nosewheel collapsed, and it dug into the lakebed before finally grinding to a stop. Landing-gear problems and subsequent damage would be a recurring theme in the early X-2 glide flights. Skip Ziegler and USAF test pilot Frank "Pete" Everest (below) managed a few glide flights in 1952, but on May 12 the next year, Ziegler and engineer Frank Welko were killed when the No. 2 airplane exploded and fell from the B-50 mothership during a propellant-system check near the upstate-New York Bell plant. The B-50 made it home safely, but was so badly-damaged it had to be scrapped. The tragedy left only one X-2 for the test program. NASA Photo.

EverestX2color.jpg Pete Everest & Bell X-2 picture by DanaC_

Lt. Col. Frank K. "Pete" Everest and the X-2. Everest made the type's first powered flights, up to Mach 2.87. Note the "Indian War Bonnet" motif on Pete's helmet. USAF Photo.

The X-2 was bigger and heavier than previous rocket planes, so the old reliable B-29 mothership was retired late in the X-1 series program in favor of a bigger, more powerful B-50. The B-50 was an improved version of the B-29, with stronger metals and structure, a taller tail, revised systems, and 4-row, 28-cylinder Pratt & Whitney R4360 radials. All in all, a better weight lifter and performer (and therefore a better X-plane mothership) than the B-29. When configured to carry rocket planes, the bomber was designated an EB-50. NASA Photo.

Video: Launch of the X-2 (MPEG)

Because the X-2 was larger than the X-1 and had swept wings, it couldn't use the X-1 loading pit. To load the X-2 on the EB-50, hydraulic jacks were installed in the ramp, and the main gears were jacked up to lift the bomber's tail; the X-2 was towed underneath and lifted into the bomb bay. USAF Photo.

Video: Loading & launching the X-2 (Q)

A research aircraft program required a lot more than just an X-plane, bomber, rocket pilot, bomber crew, and a few engineers. In the foreground, you have the X-2 and Iven Kincheloe. To the left, you have the control car. Just behind the X-2 are the engineering and support staff from Bell, Curtiss-Wright, the Air Force, NACA, and Goodyear (makers of the flight test data computer used for the first time in the X-2 program.) To the right of the X-2's tail, you have one of the base fire trucks and its crew of firefighters. At left, behind the control car, you have the ambulance and medics. Behind all of this, you have the EB-50 mothership and her 13-man crew and ground crew team. Behind and to the left of the EB-50, you have (top to bottom) a Lockheed T-33 chase and observation aircraft and its pilot and crew chief, the LOX truck and driver, and the North American F-86 Sabre used for "low-chase" (descent, approach, and landing) and its ground crew. On the other side of the bomber (top to bottom) are the North American F-100 Super Sabre used for "high chase" (launch and powered flight) and its ground crew, a tow truck and driver and a maintenance vehicle and driver, and the Sikorsky H-19 search-and-rescue helicopter and crew. (The chase planes were usually flown by the program's test pilots not doing the actual rocket flight; for example, if Pete Everest was flying the X-2 today, Iven Kincheloe might be flying high chase in the "Hun," while Mel Apt flies low chase in the F-86.) USAF Photo.

Video: X-2 tracking & landing (Q)

X2TowardtheUnknown.jpg X-2 in "Toward the Unknown" picture by DanaC_

During the X-2's brief career, it became a movie star. In March of 1956, the aircraft became the central "character" (airplane-wise) in the film Toward the Unknown (the English translation of the Edwards AFB USAF Flight Reseach Center's motto, Ad In Explorata), starring William Holden, Lloyd Nolan, and Virgina Leith. The film crew is shown here at work on Rogers Dry Lake, filming the X-2 and actors in a scene just after the end of a flight. They were allowed unprecedented access to the base, facilities and aircraft for the shoot-in some cases, shooting scenes right next to the fully-fueled X-2 just before actual test flights! The film came out just after Iven Kincheloe's record-setting high-altitude flight-and just before Mel Apt's tragic accident just after breaking Mach 3. Pete Everest was the film's technical advisor. Everest, Kincheloe, Apt, Bob White, and other noted pilots participated in the fly-by of Century Series jet fighters at the end. Decades later, the X-2 would become a film star again, first on the premier episode of the time-travel sci-fi series Quantum Leap (in which time-travelling scientist Scott Bakula "leaps" into the body of a test pilot in 1956 and has to fly the bird through Mach 3-even though Bakula's character is not a pilot!) and later, in fictionalized 2-seat form in the film Space Cowboys. The Bob Rohrer Collection via BellX-2.com

This view of the EB-50 carrying the X-2 shows the high-visibility "Dayglo" paint scheme of the bomber to advantage, as well as the vapor vent tubes along the sides of the fuselage. These vent off fumes and vapors from the X-2's propellant tanks and the top-off tanks in the bomber, to prevent the buildup of explosive gasses. USAF Photo.

USAF Captains Iven Kincheloe (standing) and Milburn G. "Mel" Apt and the X-2. "Kinch," a double-ace in the Korean War, took the X-2 to a record 126,200 ft. Afterword, the press dubbed him, "The First Spaceman." Mel Apt had never flown a rocket plane before, but he was an experienced fighter test pilot. He only got 1 flight in the X-2, on September 27, 1956. On that flight, Mel went 2,060 MPH, and he became the first man to break Mach 3-then, the unforgiving rocket plane went out of control, and he was killed. USAF Photo.

Video: NPR's newsreel of Kinch's record flight (R)

Video: NPR's tape of Kinch's interview w/Walter Cronkite (R)

Iven Kincheloe prepares for a high-altitude flight in a Lockheed F-104 Starfighter. His pressure suit is basically the same model worn in the flight test programs of the rocket planes back then. After the X-2 crash that killed Mel Apt and ended that program, Iven was assigned as the lead Air Force pilot for the upcoming X-15. Sadly, he never got to fly it-the famous Korean War Sabre ace was killed trying to eject from a disabled F-104 on July 26, 1958. USAF Photo.

A lean, mean, flying machine!

by Miller, Jay

For many years, a mysterious, obelisk-like object sat on my desk. Triangular in cross-section and about 12 inches high, the part represented the state of the art in aerospace engineering during the early 1950s. Only the most knowledgeable could identify the aircraft it came from, and even fewer knew anything about the aircraft itself. blade of K-monel alloy and covered with blistered white paint, the part was in fact a section that had been laboriously hand-sawn out of the leading edge of the world's first Mach 3 aircraft-the Bell Aircraft Corp. X-2, serial no. 46-674.

Highly temperamental, the X-2 new faster and higher thao anything of its day. Born during late 1944, its sweptwing configuration represented Bell's hope for a follow-up to the then unproven, bullet-shaped X-1. Known at Bell as "Design 371)," it was proposed to the Air Force as an X-1 successor with nearly twice its performance.

During the mid-1940s, little was known about the attributes and pitfalls of swept wing aerodynamics. Predictably, the Air Force initially rejected Bell's proposal, and that forced the company to move on to a second-generation X-1 family (X-1A, X-1B and X-1D) that used the same straight wing as was used on the first generation. During October 1945, however, George Ray, Bell's preliminary design department head, formally initiated work on a totally new X-1 successor with a wing that had a 40-degree leading-edge sweep.

On December 14, 1945, the Air Force and Bell, with the National Advisory Committee for Aeronautics (NACA) in attendance, signed a contract calling for the development, construction and initial flight-testing of two XS-2 swept wing research aircraft (the "S" for "supersonic" had been dropped from its designation by 1947)-Air Force serial numbers 46-674 and 46-675.

The X-2 was conceived and built to explore flight at speeds and altitudes far beyond anything achievable with the first generation-and, in fact, second-generation-X-1s. At the time, the swept wing was an unknown quantity. Later, reference data based on the ingenious research of the U.S.'s Robert Jones and the seminal studies of Germany's Adolph Busemann provided Bell and the Air Force with a convincing argument that a swept wing could significantly enhance the performance of a third-generation high-speed research aircraft.

"Project MX-743," as the X-2 was officially called at Wright Field, formally got under way at Bell's Wheatfield, New York, plant on September 11, 1945. Stanley Smith (who was soon appointed chief project engineer) called together Bell engineers Jack Strickler, Paul Emmons, Jack Woolams, Harold Hawkins, Charles Fay and Robert Stanley to initiate discussions that would soon lead to the production of the fastest, piloted, sweptwing aircraft ever built. In Stanley's office, he and his team agreed to submit a preliminary design proposal to Wright Field no later than October 1 that year.

Some five years later, on November 11, 1950, the second X-2 airframe, 46-675 (the first completed), minus its rocket engine, was rolled out through the Wheatfield plant's doors and prepared for extensive static ground tests. This took no less than eight months, inadvertently allowing time for the completion of modifications to the EB-SOA (SIN 46011) carrier aircraft-also at Bell.

During July 1951, mated to the EB-50A mother ship, the X-2 took to the air over Wheatfield on the first of several trial hops. These were completed during early 1952 and followed by a cross-country delivery flight to Edwards AFB, California, on April 22. After ground checks had been completed, there were two more captive flights to verify compatibility. Finally, on June 27, with Bell test pilot Jean "Skip" Ziegler at the controls, 46-675 was launched on its first glide flight. Although Ziegler assessed the X-2's general control and handling characteristics as "adequate," its landing qualities were somewhat less than ideal. On touchdown, the nose gear collapsed and caused enough damage to warrant a two-month delay for repairs.

On October 10, again with Ziegler at the controls, a second glide flight was completed; this time, the landing went without incident, but as time would tell, this was purely serendipitous.

Two days after Ziegler's second glide flight, Air Force test pilot Capt. Frank Everest took over the X-2's controls. His first flight was successful, though there was considerable concern over the right balancing skid's failure to extend just prior to landing. (The main gear-skid area had been increased by 300 percent, and two small balancing skids had been installed at mid wingspan in an attempt to cure the landing-instability problem.) The touchdown jarred the stuck skid into the down-and-locked position, and the rest of the rollout went without incident.

Six days later, the X-2 and the EB-50A were mated and flown back to New York so that the first flight-worthy engine could be installed. They hoped to start powered flight trials very soon; unfortunately, during the Curtiss-Wright XLR2S two-chamber rocket engine's development, significant problems had surfaced, partly because the engine was unquestionably the most advanced man-rated rocket-propulsion system in the world. The XLR25 was throttleable, it used circulation-type (regenerative) liquid cooling for each of its two thrust chambers, and it had a complex turbo-pump system that was the lightest and most powerful of its kind.

Not surprisingly, the XLR25 engine's numerous technological advances did not come without penalty; in fact, the problems were so complex and, at times, so exasperating that serious thought was given to program cancellation. Delays in Curtiss-Wright's ability to deliver a flightworthy engine led eventually to the X-2's falling no less than three years behind schedule. The demise of the engine would almost certainly have led to the termination of the entire project, and in light of the emergent X-15, many in the Air Force and the NACA considered this prospect untenable.

In early 1953, one flight-worthy engine at last reached Bell. Following its installation in 46-675, it was statically ground tested with generally favorable results. With the engine in place, mated flights over Lake Ontario (just a few minutes by air from Wheatfield) were conducted in March 1953.

On May 12, during a routine propellant-system emergency-dump test while attached to the mother ship, 46-675 exploded and fell, in pieces, into Lake Ontario, taking company test pilot Jean Ziegler and EB-SOA observer Frank Wolko with it. The EB-SOA was damaged on its underside and flap areas, and after the aircraft landed, a closer inspection revealed a crack in the main spar. Several years passed before the cause of the tragic explosion was determined: the culprit was the infamous Ulmer leather gasket of the type used extensively in the X-2's powerplant compartment to accommodate sealing requirements for propellant plumbing joints. Ulmer leather, when saturated with liquid oxygen, was found to be highly unstable; a shock of virtually any significant magnitude would cause the gaskets to explode. Eventually, this was concluded to have been the cause of 46-675's demise.

Coupled with the aforementioned engine and landing-- gear problems, the loss of 46-675 brought the X-2 program to its knees. Wright Field informed Bell that contractor flight trials would have to be completed as quickly as possible, as it would soon be too late for the X-2 to make any meaningful contribution to high-speed, high-altitude flight research. The X-15 would be arriving in 1958 and would quickly take over in the flight arena that the X-2 was attempting to explore. Additionally, the Air Force had agreed to turn the X-2 over to the NACA at some point, and that deadline was beginning to encroach on Air Force flight-- test scheduling as well.

On July 15, 1954, the surviving X-2--46-674-with its still untested XLR25 engine, was mated to a new EB-50D carrier aircraft and flown to Edwards AFB. On August 15, following a month of static testing, Capt. Frank Everest flew 46-674, unpowered, for the first time.

Everest's flight was successful until touchdown. Almost at the instant the nose-wheel contacted the lakebed, the aircraft yawed left and instantaneously rolled in the opposite direction. Just as quickly, the instability corrected itself, only to begin again in reverse. During each rapid cycle, the wingtips slammed the ground, scraping paint and bending metal. As speed decayed, the rolling oscillations slowly decreased in frequency until the aircraft came to a dusty stop.

That the X-2 was inherently unstable during landing rollout could no longer be denied. It was also apparent that a complete solution would not be possible until a more thorough investigation had been undertaken. In the interim, the aircraft was loaded aboard the EB-50D and transported back to Bell for repairs. It was not returned to Edwards until late February 1955.

On March 8, 46-674's second glide flight was undertaken. Unfortunately, the landing-like Everest's first-- became another wild ride, and the aircraft was seriously damaged. On April 6, like its predecessors, the third glide flight ended with damage that required that 46-674 be sent back to Bell.

Everest and the Air Force now demanded a solution to the landing problem. In frustration, Bell grounded the aircraft and methodically proceeded to assess its post-- touchdown dynamics. After considerable study, Bell convinced the Air Force to allow the installation of a new 12inch-wide main skid and a shortening of the Oleo strut to approximately half its original length. The latter modification significantly lowered the X-2's center of gravity and, happily for all, at last solved the landing-instability problem. Three years later, than originally planned, the X-2 was ready to begin its powered flight program.

With Everest again at the controls, the first powered flight, took place on November 11, 1955. Although a small fire in the engine compartment caused significant damage, the decision was made to move ahead with the remainder of the flight schedule as rapidly as possible. Repairs to the burned empennage took nearly four months to complete. On March 24, a second powered flight was successful and was followed rapidly by three more on April 25, May 1 and May 11. After years of frustration, the X-2 seemed to be on its way to realizing the aspirations of its designers and builders and, of course, those in the Air Force and the NACA.

On May 25, 1956, Air Force test pilot Capt. Iven Kincheloe became the second man to fly 46-674. Everest had, however, completed two more X-2 flights before permanently passing on the reins. The first, on July 12, was only moderately successful as a result of premature engine shut-down; the second, on July 23, took Everest out to a speed of Mach 2.87 (1,900.34mph) at 68,205 feet-the highest speed ever achieved. It resulted in Everest's being, for a short time, "the fastest man alive"-a title he later used on the front cover of his 1958 autobiography.

In his post-flight analysis, Everest noted the X-2's poor stability at high Mach numbers. He predicted that 0.2 Mach could be gained if the aircraft were flown on a "perfect mission profile" (everything going as planned). As time would tell, his comments were prescient. His reflections on the aircraft's stability anomalies were later shown to be particularly insightful by Mel Apt's disastrous September 27 mission.

The X-2 now was in the very capable hands of the energetic Iven Kincheloe. His three flights quickly followed Everest's final mission; two were basically general familiarization flights, but the third, on September 7, 1956, set an altitude record that was not broken until the advent of the X-15 some four years later.

Kincheloe's record flight began with a trouble-free drop at an indicated airspeed of 225mph and at an altitude of 30,000 feet. Approximately six seconds later, the XLR25 was ignited, and the X-2 was pitched nose up and allowed to accelerate freely along its flight path. Propellant was exhausted at a pressure altitude of 104,000 feet. The X-2 then continued upward on a semi-- ballistic trajectory that took it four miles higher. After reaching the apex of its ascent, it stabilized in a gentle, nose-down attitude, and Kincheloe gingerly maneuvered it for the return glide to Edwards. The landing proved routine.

Post-flight analysis indicated the X-2's maximum pressure altitude to be 119,800 feet at Mach 1.7; the corresponding radar-measured geometric altitude was 126,200 feet. To this day, this flight represents the highest altitude ever achieved by a conventional, swept wing aircraft. The X-2's last and most famous-and, in many ways, its most spectacular-- flight- was on September 27, 1956. Capt. Milburn Apt, an Air Force test pilot newly assigned to the X-2 program, was at the controls. It turned out to be the aircraft's most significant mission and was consequently, however tenuous, its stepping stone into aviation history.

It was Apt's first flight in the X-2 and, somewhat ironically, it was the program's 13th powered mission. The flight had been difficult from the start: Kincheloe had made three attempts, but problems repeatedly led to "aborts."

By the time Apt joined the flight program, procedures were a little rushed. The Air Force, citing a September turnover date for the aircraft to go to the NACA, felt pressured to make the most of what remained of its X-2 time. Accordingly, there were very few mission restrictions; in fact, Air Force records indicate that Apt was told to fly the aircraft only within the self-determined constraints of his abilities and experience.

Apt's exposure to the performance extremes represented by the X-2 had been limited; he had not flown any. of the Air Force's small stable of rocket-propelled research aircraft, and his exposure to their idiosyncrasies consisted primarily of knowledge gained during briefings by Kincheloe and simulated missions flown in the Goodyear Electronic Digital Analyzer (GEDA-by today's standards, a terribly crude flight analysis computer/simulator).

Apt's flight, like all other X-2 high-performance missions, began with a 230mph launch from the EB-SOD at 31,800 feet. Shortly after release, full thrust was obtained in both of the XLR25's chambers, and the aircraft accelerated rapidly. By the time it passed through 43,000 feet, it was supersonic.

During most of the mission, Apt followed the predetermined flight profile. Despite his limited experience, he miraculously managed to stay exactly within the trajectory parameters outlined prior to launch. This set up the X-2's flight path so precisely that it achieved absolute maximum performance for the first time ever. Just as surprisingly, the engine ran for several seconds longer than predicted and thus provided critical power and acceleration time. Apt's maximum altitude was later determined to have been just over 72,000 feet. This was followed by a nose-over to 66,000 feet, at which point Mach 3.196 was achieved. Through the nose-over and during the final acceleration phase, a nearly optimum flight path was maintained.

Following propellant exhaustion and engine shut-down, Apt was heard to say, "Engine cut; I'm turning." Flight records clearly showed that when the engine shut down, Apt used about two degrees of right aileron and started to roll to a level flight attitude. For some inexplicable reason, he then reversed aileron to increase the left bank while moving the control stick back slowly.

Moments later, the X-2 was in a steep bank and pulling about 2 1/4G. Apt had moved the stick to the right, but it had not yet passed through neutral. The roll rate was 15 degrees per second, and the speed was Mach 3 at 62,000 feet.

Even after Apt reacted by moving the stick to the full right position, the X-2 continued to roll left. During the next nine seconds, the left side slip induced by this action rapidly built up to nine degrees. The speed was Mach 2.8 and altitude was 60,000 feet. At this point, Apt was heard to exclaim something unintelligible over the radio.

The X-2 now rolled violently with positive vertical forces ranging between 5 and 6G. Less than a second later, its attitude changed, shifting its angle of attack to minus 35 degrees; G-forces went from plus 6 to minus 6, gradually decreasing in intensity to a minus 1/2G over a period of 11 seconds.

Cockpit film later showed Apt being violently thrown about. Some 45 seconds after engine shutdown, however, the aircraft was in a relatively stable, apparently inverted attitude with Apt in a survivable, negative-G environment. Up to this point, there had been no structural failure of any kind.

Film shows Apt, in the cockpit, moving the stick to attempt a standard spin recovery. He then momentarily leaned forward-apparently to reach for the T-handle that would initiate the nose capsule's ejection. The film's last frame shows Apt being thrown upward and back in his seat-apparently at the moment the capsule was jettisoned.

The capsule was later determined to have separated at approximately 40,000 feet, some 68 seconds after the engine had depleted its propellant supply. The capsule drogue chute deployed normally at a relatively low speed. All indications were that the capsule descended as it was designed to; the canopy was apparently jettisoned at a very low altitude.

Post-accident analysis determined that Apt had successfully released his heavy lap belt but had been unable tour hadn't had time to-- jump clear of the capsule and use his seat-pack parachute. His body was found on the desert, partially ejected from the cockpit, and with the rest of the intact but crushed nose capsule lying on its side.

While the capsule was descending, nose down, the main fuselage component continued a series of long glides and stalls until it hit the ground some five miles from the capsule. Apart from the damage incurred on impact, it was relatively unscathed; a small fire erupted but soon went out.

The X-2's remains were painstakingly gathered by hand from the desert floor and trucked back to the Bell hangar at Edwards' south base following a thorough daylong on-site inspection. After several weeks of meticulous study, the remaining parts were hauled to a specially dedicated Edwards disposal site and buried.

Later calculations determined that Apt had piloted the X-2 to a new-though unofficial-absolute world speed record for piloted aircraft of Mach 3.196. This was equivalent to 2,094mph at 66,000 feet-the first over-2,000mph piloted flight in history. It remains the fastest speed ever achieved by a conventional, sweptwing, piloted aircraft.

In retrospect, it is difficult to assess the position of the X-2 in the hierarchy of the world's most significant research aircraft. Owing to the short and peripatetic status of its test-flight program, it never came even remotely close to achieving its original mission objectives. Eventually viewed as a scientific failure, it can nevertheless lay claim to the following:

first aircraft built of exotic alloy metals: stainless steel and K-monel;
first piloted aircraft equipped with a fully throttleable rocket engine;
first aircraft to be equipped-- though not flown-with an electrical fly-by-wire flight control system;
first aircraft to be equipped with a fully encapsulated emergency egress;
first piloted flight above Mach 3 and to an altitude in excess of 100,000 feet.

That mysterious desk "obelisk"-a piece of the X-2 wing leading edge given to me by Stan Smith, chief project engineer on the precedent setting swept wing research aircraft-is now safely ensconced in the little-known but superb Aerospace Education Center in Little Rock, Arkansas. Like many rare artifacts in that collection, it is stored in a restricted-access aviation research library. Someday, it will be on public display-a poignant reminder of a time when there were still significant unknowns in the world of flight-testing.