Fifty years ago today, three American astronauts departed Earth to become the first men to orbit the Moon during the flight of Apollo 8. This epic mission also featured the first manned flight of the mighty Saturn V launch vehicle as well as history’s first super-orbital entry of a manned spacecraft.
Following the Apollo 1 tragedy in January of 1967, the United States would not fly another manned space mission until October 1968. That flight, Apollo 7, was a highly successful earth-orbital mission in which the new Block II Apollo Command Module was thoroughly flight-proven.
Notwithstanding Apollo 7’s accomplishments, only 14 months remained for the United States to meet the national goal of achieving a manned lunar landing before the end of the 20th century’s 7th decade. The view held by many in late 1968 was that an already daunting task was now unachievable in the narrow window of time that remained to accomplish it.
The pessimism about reaching the Moon before the end of the decade was easy to understand. The Saturn V moon rocket had not been man-rated. The Lunar Module had not flown. Lunar Orbit Rendezvous (LOR) was untried. Men had not even so much as orbited the Moon. Yet, history would record that the United States would find a way to accomplish that which had never before been achieved.
George Low, manager of NASA’s Apollo Spacecraft Program Office, came up with the idea. Low proposed that the first manned flight of the Saturn V be a trip all the way to the Moon. It was something that Low referred to as the “All-Up Testing” concept. The newly-conceived mission would be flown in December 1968 near Christmas time.
While initially seen as too soon and too risky by many in NASA’s management hierarchy, Low’s bold proposal was ultimately accepted as the only way to meet the national lunar landing goal. Yes, there was additional risk. However, the key technologies were ready, the astronauts were willing, and the risk was acceptable.
Apollo 8 lifted-off from LC-39A at the Kennedy Space Center in Florida on Saturday, 21 December 1968 at 12:51 hours UTC. The crew consisted of NASA astronauts Frank Borman, James A. Lovell, Jr. and William A. Anders. Their target – the Moon – was 220,000 miles away.
After a 69-hour outbound journey, Apollo 8 entered lunar orbit on Tuesday, 24 December 1968 – Christmas Eve. The Apollo 8 crew photographed the lunar surface, studied the geologic features of its terrain, and made other observations from a 60-nautical mile circular orbit. The spacecraft circled the Moon 10 times in slightly over 20 hours.
For many, the most poignant and memorable event in Apollo 8’s historic journey occurred on Christmas Eve night when each of the flight crew took turns reading from the Book of Genesis in the Holy Bible. The solemnity of the moment was evident in the voices of the astronauts. They had seen both the Moon and the Earth from a perspective that none before them had. Fittingly, they expressed humble reverence for the Creator of the Universe on the anniversary of the birth of the Redeemer of mankind.
Apollo 8 departed lunar orbit a little over 89 hours into the mission. Following a nearly 58-hour inbound trip, Apollo 8 reentered the earth’s atmosphere at 36,221 feet per second on Friday, 27 December 1968. The first manned super-orbital reentry was performed in total darkness. It was entirely successful as Apollo 8 landed less than 1 nautical mile from its target in the Pacific Ocean. The USS YORKTOWN effected recovery of the weary astronauts and their trustworthy spacecraft. Mission total elapsed time was 147 hours and 42 seconds.
The year 1968 was a tumultuous one for the United States of America. Martin Luther King and Robert Kennedy had been assassinated. American military blood flowed on the battlefields of Vietnam and civilian blood was let in countless demonstrations taking place in the nation’s cities. The ill-posed sexual revolution continued to erode the country’s social and moral moorings.
But, as is so often the case, an event from the realm of flight, now newly extended to lunar space, reminded us of our higher nature and potential. For a too brief moment, Apollo 8 put our collective purpose for being here into sharp focus. Perhaps a short phrase in a telegram sent to Frank Borman from someone he had never met said it best: “You saved 1968!”
However, looking through the lens of history, we now know that Apollo 8 did much more than end the penultimate year of the 1960’s on a positive note. Indeed, it may be said that Apollo 8 saved the entire Apollo Program.
Fifty-five years ago today, USAF NF-104A (S/N 56-762) crashed to destruction following a rocket-powered zoom to 101,600 feet above mean sea level (AMSL). The pilot, USAF Colonel Charles E. “Chuck” Yeager, was seriously injured, but survived when he successfully ejected from the stricken aircraft approximately 5,000 feet above ground level (AGL).
The USAF/Lockheed NF-104A was designed to provide spaceflight-like training experience for test pilots attending the Aerospace Research Pilot School (ARPS) at Edwards Air Force Base, California. The type was a modification of the basic F-104A Starfighter aircraft. Three copies of the NF-104A were produced (S/N’s 56-0756, 56-0760 and 56-0762). It was the ultimate zoom flight platform.
In addition to a stock General Electric J79-GE-3 turbojet, the NF-104A was powered by a Rocketdyne LR121-NA-1 rocket motor. The J79 generated 15,000 pounds of thrust in afterburner and burned JP-4. The LR-121 produced 6,000 pounds of thrust and burned a combination of JP-4 and 90% hydrogen peroxide. Rocket motor burn time was on the order of 90 seconds.
Around 1400 hours PST on Tuesday, 10 December 1963, Colonel Yeager took-off from Edwards Air Force Base to attempt his second zoom flight of the day. That morning, he had zoomed NF-104A, S/N 56-760 to an altitude of 108,700 feet. Four days earlier, Yeager had zoomed the same airplane to the highest altitude he would ever achieve in the type; 110,500 feet AMSL.
The zoom apex altitude for the ill-fated afternoon flight was only 101,600 feet AMSL with rocket motor burnout taking place 5 seconds post-apogee. That is, the aircraft was already on the descending leg of the zoom trajectory and in the early stages of reentry. Yeager later reported that the aircraft angle-of-attack at that point was on the order of 50 deg; a figure that is well past the NF-104A pitch-up angle-of-attack (i.e., 14-17 deg). Yeager had flown the aircraft this way on previous zoom flights and had always been able to lower the nose via reaction control system (RCS) inputs.
Unfortunately, the RCS did not not have sufficient pitch control authority to bring the nose down on the mishap flight. As a result, the aircraft began the reentry in an extremely nose-high attitude. As the dynamic pressure rapidly built-up, the NF-104A departed controlled flight and went through a series of post-stall gyrations between 90,000 and 65,000 feet. These gyrations ultimately led to a series of flat spins occurring between 65,000 and 20,000 feet.
Running out of altitude, Yeager desperately deployed his drag parachute as an anti-spin device. This action indeed stopped the flat spin. Airspeed picked-up to 180 KIAS with the aircraft hanging in the chute, but the pilot was unable to get an airstart on his J79 turbojet which had spooled down to 6% of maximum RPM. At 12,000 feet, Yeager jettisoned his drag chute and the NF-104A immediately pitched-up again into a flat spin. After three-quarters of a turn, Yeager ejected about 5,000 feet AGL. Yeager landed close to where the mishap aircraft had impacted and was in a great deal of pain due to burns he received during the ejection process. Happily, he survived this traumatic event and recovered completely from his injuries.
Objective analysis of the loss of NF-104A, S/N 56-762 reveals that the aircraft simply was not flown in a manner commensurate with the intricacies of the zoom environment. The critical importance of quickly intercepting and maintaining the target inertial pitch angle during pull-up had been repeatedly demonstrated by other test pilots as had proper control of aircraft angle-of-attack during reentry. Colonel Yeager elected not to fly the aircraft in accordance with these dictates.
In all of his NF-104A zoom attempts, Colonel Yeager consistently flew the airplane over the top at angles-of-attack well beyond the pitch-up value. RCS control authority was sufficient to lower the nose to sub-pitch-up angles-of-attack just prior to reentry on all but the mishap flight. Unfortunately, the low apex altitude (101,600 feet AMSL) of that zoom resulted in a higher dynamic pressure that, in conjunction with very high angles-of-attack, produced a nose-up aerodynamic pitching moment that the RCS could not overcome.
The aircraft mishap of 10 December 1963 forever changed the way in which NF-104A pilots would be allowed to fly the rocket-powered zoom mission. Prior to the mishap, the NF-104A had been zoomed to an altitude of 120,800 feet AMSL by USAF Major Robert W. Smith on 06 December 1963. This unofficial United States record still stands today. After a mishap investigation, NF-104A maximum altitude was limited to 108,000 feet AMSL. This restricted performance was mandated ostensibly out of concern for the safety of ARPS student test pilots.
The ultimate and lasting result of the post-mishap restriction on NF-104A flight performance was that it did a great disservice to ARPS student test pilots in that it made their spaceflight training experience something less than what it could and should have been. It is ironic that, although the correct manner in which to zoom the airplane had been repeatedly validated by USAF and Lockheed test pilots prior to the 56-0762 mishap, the decision to restrict NF-104A performance was based on a single flight which clearly demonstrated how not to fly the airplane.
Fifty-five years ago today, USAF Major Robert W. Smith zoomed the rocket-powered USAF/Lockheed NF-104A to an unofficial world record altitude of 120,800 feet. This mark still stands as the highest altitude ever achieved by a United States aircraft from a runway take-off.
A zoom maneuver is one in which aircraft kinetic energy (speed) is traded for potential energy (altitude). In doing so, an aircraft can soar well beyond its maximum steady, level altitude (service ceiling). The zoom maneuver has both military and civilian flight operations value.
The USAF/Lockheed NF-104A was designed to provide spaceflight-like training experience for test pilots attending the Aerospace Research Pilot School (ARPS) at Edwards Air Force Base, California. The type was a modification of the basic F-104A Starfighter aircraft. Three copies of the NF-104A were produced (S/N’s 56-0756, 56-0760 and 56-0762). It was the ultimate zoom flight platform.
In addition to a stock General Electric J79-GE-3 turbojet, the NF-104A was powered by a Rocketdyne LR121-NA-1 rocket motor. The J79 generated 15,000 pounds of thrust in afterburner and burned JP-4. The LR-121 produced 6,000 pounds of thrust and burned a combination of JP-4 and 90% hydrogen peroxide. Rocket motor burn time was on the order of 90 seconds.
The NF-104A was kinematically capable of zooming to altitudes approaching 125,000 feet. As such, it was a combined aircraft, rocket, and spacecraft. The pilot had to blend aerodynamic and reaction controls in the low dynamic pressure environment near the zoom apex. He was also required to fly in a full pressure suit for survival at altitudes beyond the Armstrong Line.
On Friday, 06 December 1963, Bob Smith took-off from Edwards and headed west for the Pacific Ocean. Out over the sea, he changed heading by 180 degrees in preparation for the zoom run-in. At a point roughly 100 miles out, Smith then accelerated the NF-104A (S/N 56-0760) along a line that would take him just north of the base. Arriving at Mach 2.4 and 37,000 feet, Smith then initiated a 3.75-g pull to a 70-degree aircraft pitch angle. Turbojet and rocket were at full throttle.
Things happened very quickly at this point. Smith brought the J79 turbojet out of afterburner at 65,000 feet and then moved the throttle to the idle detent at 80,000 feet. The rocket motor burned-out around 90,000 feet. Smith controlled the aircraft (now spacecraft) over the top of the zoom using 3-axis reaction controls. The NF-104A’s arcing parabolic trajectory subjected him to 73 seconds of weightlessness. Peak altitude achieved was 120,800 feet above mean sea level.
On the back side of the zoom profile, Bob Smith restarted the windmilling J79 turbojet and set-up for landing at Edwards. He touched down on the main runway and rolled out uneventfully. Total mission time from brake-release to wheels-stop was approximately 25 minutes.
Much more could be said about the NF-104A and its unique mission. Suffice it to say here that two of the aircraft ultimately went on to serve in the ARPS from 1968 to 1971. The only remaining aircraft today is 56-0760 which sits on a pole in front of the USAF Test Pilot School (TPS) at Edwards.
Bob Smith went on to make many other noteworthy contributions to aviation and his nation. Having flown the F-86 Sabre in Korea, he volunteered to fly combat in Viet Nam in his 40th year. Stationed at Korat AFB in Thailand, he commanded the 34th Fighter Squadron of the 388th Tactical Fighter Wing. Smith flew 100 combat missions in the fabled F-105D Thunderchief; many of which involved the infamous Pack VI route in North Viet Nam.
Bob Smith was a true American hero. Like so many of the airmen of his day, Smith was a man whose dedication, service, and courage went largely unnoticed and underappreciated by his fellow countrymen. Bob Smith’s final flight came just 3 months shy of his 82nd birthday on Thursday, 19 August 2010.
Thirty-seven years ago this month, the Space Shuttle Columbia completed the second orbital space mission of the Space Shuttle Program. Designated STS-2, the mission marked the first reuse of a space vehicle for manned orbital flight.
America’s early manned spacecraft – Mercury, Gemini and Apollo – were single-flight vehicles. That is, a new spacecraft was required for each space mission. This was appropriate for meeting the aims of the early space program which concentrated on getting America to the moon before the end of the 1960’s.
The concept of space vehicle reusability came into vogue with the introduction of the Space Transportation System (STS). The original goal of the STS was to provide frequent and routine access to space via a fleet of Space Shuttle vehicles. For the STS to achieve economic viability, this meant flying a Space Shuttle once every two weeks. History records that this projected flight rate was much too optimistic.
The Space Shuttle vehicle was ultimately configured as a 3-element system consisting of (1) a winged orbiter, (2) a pair of solid rocket boosters (SRB’s) and (3) an external tank (ET). Both the orbiter and the SRB’s were designed to be reusable. The ET would be the only disposable element of the system since higher costs would be incurred in the recovery and refurbishment of this piece of flight hardware than in simply using a new one for each flight.
The Space Shuttle was designed to haul large payloads; on the order of 60,000 and 50,00 lbs into and out of orbit, respectively. With a maximum landing weight of 230,000 lbs, the Space Shuttle Orbiter needed wings to generate the required aerodynamic lift force. Wings were needed to satisfy the Orbiter’s 1,100-nm entry cross range requirement as well.
Following the successful first flight (STS-1) of the Space Shuttle Columbia in April of 1981, preparations began immediately to ready the Orbiter for its equally monumental second flight. The STS-2 flight crew would consist of Commander Joe Henry Engle and Pilot Richard Harrison Truly. STS-2 would be the first orbital spaceflight for both men.
On Thursday, 12 November 1981, the Space Shuttle Columbia lifted-off at 15:09:59 UTC from Cape Canaveral’s LC-39A. Ascent flight was nominal and Columbia was placed into a 125-nm x 120-nm orbit. At this point, Columbia became the first manned spacecraft to achieve Earth-orbit twice. It was an extra special occasion for Richard Truly inasmuch as it was his 44th birthday.
Engle and Truly anticipated 5-days in orbit with their celestial steed. However, one of Columbia’s three fuel cells failed early-on and the mission was reduced to just over two days. Nonetheless, the crew achieved 90 percent of the mission’s goals. They even remained awake during a scheduled sleep period to exercise the new Canadian Remote Manipulator System (RMS).
On Saturday, 14 November 1981, Columbia and her crew successfully completed STS-2 by landing on Rogers Dry Lake at Edwards Air Force Base, California. Main gear touchdown occurred at 21:23:11 UTC. Joe Engle flew the entire reentry manually. He holds the distinction of being the only pilot to manually fly a lifting space vehicle all the way from orbit to landing. Engle completed a total of 29 Programmed Test Input (PTI) aerodynamic maneuvers in the process.
STS-2 was a monumental success. Columbia became the first space vehicle to be reused for manned orbital space operations. Other Orbiters would follow including Challenger, Atlantis, Discovery, and Endeavor. The final mission of the Space Shuttle Program (STS-135) was flown by Atlantis in July 2011.
As a footnote, Joe Engle went on to command one more Space Shuttle mission in 1985 (STS-51I). He retired from the USAF in November of 1986. Richard Truly served as Commander of STS-8 in 1983. That mission featured the first night launch and landing of the Space Shuttle. Richard Truly also served as NASA Administrator from May of 1989 to May of 1992.
Sixty-five years ago today, the USN/Douglas D-558-II Skyrocket became the first aircraft to fly at twice the speed of sound. This historic event took place in the skies over Edwards Air Force Base, California.
The D-558-II was a United States Navy (USN) X-aircraft and first flew in February of 1948. It was contemporaneous with the USAF/Bell XS-1. The aircraft measured 42 feet in length with a wing span of 25 feet. Maximum take-off weight was 15,266 pounds. Douglas manufactured a trio of D-558-II aircraft (Bureau Numbers 37973, 37974 and 37975).
The original version of the swept-wing D-558-II had both rocket and turbojet propulsion. The latter system providing a ground take-off capability. However, like other early X-aircraft such as the XS-1, X-1A, X-2 and X-15), the D-558-II achieved max performance through the use of a mothership and rocket power alone.
The record-setting day was Friday, 20 November 1953. On that occasion, the white D-558-II (Bureau No. 37974) was carried to the drop altitude of 32,000 feet by a USN P2B-1S (Bureau No. 84029). NACA test pilot A. Scott Crossfield was in the D-558-II cockpit. Although ailing with the stomach flu, Crossfield was not about to let a little urpiness force him to miss today’s historic aeronautical events!
Following a successful drop from the mothership, Crossfield ignited the Reaction Motors LR8-RM-6 (USN designation for the XLR-11) rocket motor and started uphill. After closely adhering to a carefully planned climb schedule, Crossfield initiated a pushover at 72,000 feet that resulted in a shallow dive. Passing through 62,000 feet, the D-558-II hit a speed of 1,291 mph; Mach 2.005.
The D-558-II reached Mach 2 due to a confluence of several factors. First, Crossfield flew the profile as briefed. Second, temperatures at altitude that day were unusually low. This lowered the speed of sound and thus increased Mach number. Third, the ground crew did an extraordinary job of optimizing the D-558-II for the maximum speed mission.
Expanding on the last point mentioned above, extension tubes were added to the LR8-RM-6 rocket motor. This increased thrust from 6,000 to 9,000 pounds. The aircraft was then cold-soaked overnight in an effort to maximize its propellant load. Finally, external airframe gaps and panel openings were taped over and the aircraft was waxed and polished in an effort to minimize aerodynamic drag.
Scott Crossfield received the 1954 Lawrence B. Sperry Award for his Mach 2 exploits. The record-setting aircraft (Bureau No. 37934) is currently displayed at the National Air and Space Museum in Washington, D.C. in tribute to its many contributions to aviation history.
Fourteen years ago today, the NASA X-43A scramjet-powered flight research vehicle reached a record speed of over 6,600 mph (Mach 9.68). In doing so, the X-43A eclipsed its own record speed of Mach 6.83 (4,600 mph) and became the fastest air breathing aircraft of all time.
In 1996, NASA initiated a technology demonstration program known as HYPER-X. The central goal of the HYPER-X Program was to successfully demonstrate sustained supersonic combustion and thrust production of a flight-scale scramjet propulsion system at speeds up to Mach 10.
Also known as the HYPER-X Research Vehicle (HXRV), the X-43A aircraft was a scramjet test bed. The aircraft measured 12 feet in length, 5 feet in width, and weighed close to 3,000 pounds. The X-43A was boosted to scramjet take-over speeds with a modified Orbital Sciences Pegasus rocket booster.
The combined HXRV-Pegasus stack was referred to as the HYPER-X Launch Vehicle (HXLV). Measuring approximately 50 feet in length, the HXLV weighed slightly more than 41,000 pounds. The HXLV was air-launched from a B-52 mothership. Together, the entire assemblage constituted a 3-stage vehicle.
The third and final flight of the HYPER-X program took place on Tuesday, 16 November 2004. The flight originated from Edwards Air Force Base, California. Using Runway 04, NASA’s venerable B-52B (S/N 52-0008) started its take-off roll at approximately 21:08 UTC. The aircraft then headed for the Pacific Ocean launch point located just west of San Nicholas Island.
At 22:34:43 UTC, the HXLV fell away from the B-52B mothership. Following a 5 second free fall, rocket motor ignition occurred and the HXLV initiated a pull-up to start its climb and acceleration to the test window. It took the HXLV 75 seconds to reach a speed of slightly over Mach 10.
Following rocket motor burnout and a brief coast period, the HXRV (X-43A) successfully separated from the Pegasus booster at 109,440 feet and Mach 9.74. The HXRV scramjet was operative by Mach 9.68. Supersonic combustion and thrust production were successfully achieved. Total engine-on duration was approximately 11 seconds.
As the X-43A decelerated along its post-burn descent flight path, the aircraft performed a series of data gathering flight maneuvers. A vast quantity of high-quality aerodynamic and flight control system data were acquired for Mach numbers ranging from hypersonic to transonic. Finally, the X-43A impacted the Pacific Ocean at a point about 850 nautical miles due west of its launch location. Total flight time was approximately 15 minutes.
The HYPER-X Program was now history. Supersonic combustion and thrust production of an airframe-integrated scramjet had indeed been achieved for the first time in flight; a goal that dated back to before the X-15 Program. Along the way, the X-43A established a speed record for air breathing aircraft and earned several Guinness World Records for its efforts.
As a footnote to the X-43A story, the HYPER-X Flight 3 mission would also be the last for NASA’s fabled B-52B mothership. The aircraft that launched many of the historic X-15, M2-F2, M2-F3, X- 24A, X-24B and HL-10 flight research missions, and all three HYPER-X flights, would take to the air no more. In tribute, B-52B (S/N 52-0008) now occupies a place of honor at a point near the North Gate of Edwards Air Force Base.
Fifty-two years ago this month, NASA’s pioneering spaceflight program, Project Gemini, was brought to a successful conclusion with the 4-day flight of Gemini XII. Remarkably, the mission was the tenth Gemini flight in 20 months.
Boosted to Earth orbit by a two-stage Titan II launch vehicle, Gemini XII Command Pilot James A. Lovell, Jr. and Pilot Edwin E. “Buzz” Aldrin, Jr. lifted-off from Cape Canaveral’s LC-19 at 20:46:33 UTC on Friday, 11 November 1966. The flight was Lovell’s second trip into space and Aldrin’s first.
Like every Gemini mission before it, Gemini XII was not a glitch-free spaceflight. For instance, when the spacecraft’s rendezvous radar began acting oddly, the crew had to resort to sextant and chart to complete the last 65 nautical miles of the rendezvous with their Agena Target Vehicle. But, overcoming this and other obstacles served to provide the experience and instill the confidence needed to meet the truly daunting challenge that lay ahead; landing on the Moon.
Unquestionably, Gemini XII’s single most important contribution to the United States manned space effort was validating the notion that a well-trained astronaut could indeed do useful work in an Extra-Vehicular Activity (EVA) environment. The exhausting and even dangerous EVA experiences of Gene Cernan on Gemini IX and Dick Gordon on Gemini XI brought into sharp focus the daunting challenge of performing even seemingly simple work assignments outside the Gemini spacecraft.
Buzz Aldrin performed a trio of EVA’s on Gemini XII. Two of these involved standing in his seat with the hatch open. The third involved a tethered EVA or space walk. On the latter, Aldrin successfully moved about the exterior of the Gemini-Agena combination without exhausting himself. He also used a special-purpose torque wrench to perform a number of important work tasks. Central to Aldrin’s success was the use of foot restraints and auxiliary tethers to anchor his body while floating in a weightless state.
Where others had struggled and not been able to accomplish mission EVA goals, Buzz Aldrin came off conqueror. One of the chief reasons for his success was effective pre-flight training. A pivotal aspect of this training was to practice EVA tasks underwater as a unique means of simulating the effects of weightlessness. This approach was found to be so useful that it has been used ever since to train American EVA astronauts.
Lovell and Aldrin did many more things during their highly-compressed 4-day spaceflight in November of 1966. Multiple dockings with the Agena, Gemini spacecraft maneuvering, tethered station-keeping exercises, fourteen scientific experiments, and photographing a total eclipse occupied their time aloft.
On Tuesday, 15 November 1966, on their 59th orbit, a tired, but triumphant Gemini XII crew returned to Earth. The associated reentry flight profile was automated; that is, totally controlled by computer. Yet another first and vital accomplishment for Project Gemini. Splashdown was in the West Atlantic at 19:21:04 UTC.
While Gemini would fly no more, both Lovell and Aldrin certainly would. In fact, both men would play prominent roles in several historic flights to the Moon. Jim Lovell flew on Apollo 8 in December 1968 and Apollo 13 in April 1970. And of course, Buzz Aldrin would walk on the Moon at Mare Tranquilitatis in July 1969 as the Lunar Module Pilot for Apollo 11.
Fifty-one years ago this month, USAF Major William J. “Pete” Knight piloted the fabled USAF/North American X-15A-2 rocket-powered hypersonic flight research aircraft to a record speed of 4,520 mph – roughly a mile and a quarter per second. This mark is approximately 50 percent faster than the highest speed ever attained by a “speeding bullet”.
North American’s original X-15 production run consisted of three (3) aircraft. The X-15A-2 was a rebuild of the 2nd airframe (S/N 56-6671) which had been severely damaged during an emergency landing at Mud Lake, Nevada in November of 1962.
The rebuilt aircraft was configured with a pair of propellant-containing drop tanks that allowed the type’s XLR-99 rocket engine to operate 60 seconds beyond the stock X-15’s 80-second burn time. Among other modifications, the aircraft also carried a pylon-mounted dummy ramjet in the ventral region of the aft fuselage.
With the addition of the external propellant tanks, the X-15A-2 was really a three-stage vehicle. The first stage was the NASA NB-52B mothership which launched the X-15 at Mach 0.82 and 45,000 feet. The second stage consisted of the propellant-laden external tanks which were jettisoned at Mach 2.0 and 70,000 feet. The third stage was the X-15A-2 with its entire internal propellant load.
Due to the increased speed of the X-15A-2, the aircraft was covered with Martin MA-25S ablator to protect it from the higher aerodynamic heating loads. The baseline ablator was pink in color and gave the X-15A-2 a rather odd appearance. Fortunately, application of a white wear/sealer over the ablator gave the aircraft a more dignified look.
On Tuesday, 03 October 1967, Pete Knight and the X-15A-2 dropped away from the NB-52B (S/N 52-008) at the start of the X-15 Program’s 188th mission. Knight ignited the XLR-99 rocket engine and executed a pull-up followed by a pushover to level flight at a little over 102,000 feet. Aircraft speed at XLR-99 burnout was 4,520 mph (Mach 6.7).
As the aircraft decelerated following burnout, Knight executed a series of pre-planned flight maneuvers to acquire vital aerodynamics data. However, passing through Mach 5.5, he received an indication in the cockpit that a high temperature condition existed in the XLR-99 engine bay.
Knight attempted to jettison the aircraft’s remaining propellants, but to no avail. The jettison tubes were welded shut by whatever was happening in the engine bay. This meant he would land heavier and faster than usual. Fortunately, Knight’s piloting skills allowed him to get the X-15A-2 on to Rogers Dry Lake in one piece.
As flight support personnel inspected the X-15A-2 airframe following Knight’s emergency landing, they were alarmed at what they found. The aft ventral region of the aircraft had incurred significant thermal damage. Further, the dummy ramjet was gone.
As reported in the classic NASA document, TM-X-1669, higher-than-expected aerodynamic heating levels were responsible for the damage to the X-15A-2.
First, shock wave/boundary layer interaction heating on the lower fuselage just ahead of the pylon (1) completely destroyed the ablator in that region and (2) penetrated the Inconel-X airframe structure. This introduced very high temperature air into the X-15 engine bay.
Second, impingement of the dummy ramjet nose shock on the detached bow shock coming off of the pylon produced a shear layer that focused on the pylon leading edge. The resulting heating rates were of sufficient magnitude and duration to both burn away the pylon ablator and burn through the pylon structure. The weakened pylon structural attachment eventually failed and the dummy ramjet departed the main airframe.
Pete Knight will forever hold the record for the fastest X-15 flight. However, the X-15A-2 never flew again. Only 11 more flights remained in the X-15 Program at the time. A lack of time and funding meant that little was to be gained by repairing the thermally-damaged aircraft.
As for the final disposition of the X-15A-2 (S/N 56-6671), the aircraft’s remaining ablator was removed with its external surface cleaned-up and original markings restored. The aircraft now resides in a place of honor at the National Museum of the United States Air Force located at Wright-Patterson AFB in Dayton, Ohio.
Sixty-four years ago this week, the USAF/Douglas X-3 Stiletto experimental flight research aircraft encountered a violent dynamic instability during a flight test maneuver. NACA test pilot Joseph A. Walker was able to successfully recover the aircraft from this flight upset known as Inertial Roll Coupling.
The X-3 was designed to fly at speeds up to Mach 2. The aircraft was approximately 67 feet in length and had a wing span on the order of 23 feet. Aircraft gross take-off weight was 23,840 pounds.
A pair of Westinghouse J46-WE-1 turbojets were intended to power the X-3. However, protracted developmental problems and installation issues with these powerplants would eventually prevent their use in the aircraft.
The X-3 was ultimately outfitted with a pair of Westinghouse J34-WE-17 turbojets. The result was that the X-3 was now grossly underpowered and could barely fly supersonically. Indeed, the Stiletto’s maximum demonstrated Mach number was 1.21 which was achieved in a 30-deg dive!
Notwithstanding the above, the X-3 took to the air 54 times between October 1952 and May 1956 for the purpose of conducting transonic flight research. However, it would be on the type’s 43rd flight that the X-3 would make perhaps its most important contribution to aviation.
On Wednesday, 27 October 1954, Joe Walker took-off in the X-3 (S/N 49-2892) from Edwards Air Force Base, California. At Mach 0.92 and 30,000 feet, Walker applied left aileron at fixed-rudder in an effort to develop a rapid roll response. To Walker’s utter amazement, the X-3 went wild in both pitch and yaw.
Although it seemed to last much longer, Walker was able to recover control of the X-3 within 5 seconds of his initial left aileron input. In true test pilot fashion, Walker again made an abrupt rudder-fixed left aileron input at Mach 1.05. The same thing happened. However, this time the aircraft’s motions were more violent.
Happily, Walker again recovered control of the X-3. Having had enough of flight test frontiersmanship for one day, the intrepid Walker uneventfully recovered the experimental aircraft back at Edwards.
The phenomenon that Joe Walker and the X-3 encountered that day in 1954 is known as Inertial Roll Coupling. It is a resonant divergence in either pitch or yaw due to the presence of roll rate. Aircraft like the X-3, which have low longitudinal and/or directional static stability as well as high pitch-to-roll and yaw-to-roll moment of inertia ratios, are especially susceptible to this phenomenon.
As a postscript to our story, the phenomenon of Inertial Roll Coupling had been hypothesized by the NACA’s William H. Phillips back in June of 1948. For Joe Walker in October of 1954, engineering theory would become flight test fact in a few terrifying seconds high in the skies over Edwards Air Force Base.
Fifty-six years ago this month, Mercury Astronaut Walter M. Schirra, Jr. orbited the Earth six (6) times in his Mercury spacecraft code-named Sigma 7. The near-perfect 9-hour spaceflight was the United States’ third manned orbital mission flown within a period of eight (8) months.
Project Mercury was United States’ first manned spaceflight program. This historic pioneering space effort helped lay the foundation for America’s quest for the Moon. A total of six (6) missions (2 sub-orbital and 4 orbital) was flown between May of 1961 and May of 1963.
The Mercury Spacecraft measured 11.5 feet in length and had a diameter of 6.2 feet. Orbital weight was roughly 3,000 pounds. With a cockpit volume of only 60 cubic feet, an astronaut’s corporeal fit inside the spacecraft was exceedingly tight. Vehicle entry and egress was a real shoe-horning process. It is not complete hyperbole to say that, once inside, an astronaut wore, more than rode in, the Mercury space vehicle.
Despite its diminutive size, the Mercury Spacecraft was an able space-faring ship. Indeed, it was configured with a complete suite of life support, navigation, attitude control, communications, deboost, recovery and thermal protection systems. Aided by a vast national mission support team, recovery force, and world-wide tracking system, the Mercury spaceflight effort was entirely successful in establishing America in space.
America’s first astronauts were known as the Mercury Seven. History records their names; Shepard, Grissom, Glenn, Carpenter, Schirra, Cooper and Slayton. In the tense 1960’s Space Race with the Soviet Union, these men were indeed America’s Single-Combat Warriors immortalized by the late author Tom Wolfe in his classic book, The Right Stuff.
Mercury-Atlas No. 8 (MA-8) was the fifth Mercury mission. Whereas the two (2) previous flights had been three (3) orbit missions, MA-8 was scheduled to orbit the Earth six (6) times. The focus would be on spacecraft operations instead of space science. The intent was to verify that the Mercury spacecraft could be cleared for an orbital mission duration of at least 24 hours on the very next flight
As was the custom for a Mercury astronaut, Schirra personally named his orbital steed. As such, Schirra chose the name Sigma 7. The term Sigma, the Greek mathematical symbol for summation, signified a summation or culmination of flight experience and engineering development that led to a mature Mercury Spacecraft system. The numeral 7 represented the Mercury Seven.
The MA-8 mission began with lift-off from Cape Canaveral’s LC-14 at 12:15:12 UTC on Wednesday, 03 October 1962. The Atlas D launch vehicle placed Schirra into a 152.8-nm x 86.9-nm orbit. Once in orbit, Schirra quickly got down to business. This included tracking the Atlas booster, maneuvering the spacecraft, observing and photographing the Earth, and conducting various scientific experiments.
Schirra did a particularly good job at conserving the precious supply of Reaction Control System (RCS) fuel. One of the MA-8 objectives had been to do so. In fact, Schirra conserved fuel even more efficiently than planned. Other than an annoying and uncomfortable spacesuit heating problem that occurred several times, the entire MA-8 mission was what Schirra would ultimately call “textbook”.
MA-8 retro-fire occurred at 21:07:12 UTC. During the reentry, the automatic rate stabilization system damped spacecraft pitch and yaw oscillations. Drogue and main parachute deployment took place at 40,000 feet and 15,000 feet, respectively. Splashdown in the Pacific Ocean occurred 1,200 nm northwest of Hawaii at 21:28:22 UTC.
The success of MA-8 paved the way to Gordon Cooper’s historic 22-orbit, 34-hour MA-9 mission in May of 1963. The Gemini and Apollo Programs would soon follow. Wally Schirra would play a big part in both. He commanded the historic Gemini 6 orbital rendezvous mission in December of 1965. Schirra also went on to command the critical Apollo 7 mission in October of 1968.
Wally Schirra was the only member of the Mercury Seven to orbit the Earth in Mercury, Gemini and Apollo spacecraft. He left this earthly scene in May 2007 at the age of 84.
