Twenty-six years ago this month, the United States Army’s Homing Overlay Experiment (HOE) anti-missile successfully intercepted a ballistic missile target in space. The feat marked the first time in aerospace history that an exoatmospheric hit-to-kill intercept was achieved.
The HOE Program was a technology demonstration effort conducted by the United States Army (USA) to enable a nonnuclear hit-to-kill intercept capability for application against Soviet nuclear warheads. The Lockheed Company was awarded the development contract in 1978. A total of four (4) exoatmospheric flights tests were conducted from February 1983 through June 1984.
The HOE interceptor was unique in that it employed a 13-ft-diameter radial net that markedly increased the frontal area of the interceptor. The net mechanism was deployed just before target intercept. This unit consisted of 36 aluminum spokes, to each of which was affixed a trio of stainless steel weights or fragments.
The HOE test vehicle was equipped with an IR seeker for target detection in space. Upon target detection, the onboard propulsion system was driven by vehicle guidance and control to place the interceptor on a collision course with the target. At a closing velocity of 20,000 ft/sec, the kinetic energy of the 2,600-lb HOE interceptor was more than sufficient to destroy the target.
A two-stage Minuteman 1 Intercontinental Ballistic Missile (ICBM) served as the HOE booster. It was launched from Meck Island on the Kwajalein Missile Range out in the Marshall Islands. The target vehicle was also a Minuteman missile configured with a dummy warhead. It was launched from 4,500 miles away at Vandenberg Air Force Base, California.
The first three (3) HOE flight tests failed to produce a successful hit-to-kill intercept due to system detection and guidance anomalies. However, on Sunday, 10 June 1984, everything worked as planned when the fourth and final HOE test vehicle successfully intercepted and destroyed the ballistic target via kinetic kill. In the glow of the post-flight celebration, the successful HOE intercept was likened unto hitting a bullet with a bullet.
The HOE flight demonstration success came at a pivotal time in that the vaunted Strategic Defense Initiative (SDI) had begun in January of 1984. The importance of the first-ever hit-to-kill intercept was recognized in 1986 when the HOE Program received that year’s American Defense Technical Achievement Award.
The HOE concept never saw mass production since it was a heavy and rather expensive solution to the hit-to-kill problem. However, its technical legacy extends to the present day. Indeed, the highly capable and ever-evolving Aegis Ballistic Missile Defense (ABMD) system is a vital component of our nation’s Ballistic Missile Defense System (BMDS).
Thirty-eight years ago this month, the No. 1 USAF/Northrop YF-17 Cobra Lightweight Fighter (LWF) prototype made its maiden flight from Edwards Air Force Base, California. Northrop Chief Test Pilot Henry E. “Hank” Chouteau was at the controls of the agile twin-engine jet.
The Lightweight Fighter (LWF) Technology Program was a United States Air Force (USAF) effort to develop a reduced-cost, highly maneuverable combat aircraft. The LWF Program, which began in 1971, ultimately resulted in a competitive fly-off between the Northrup YF-17 and General Dynamics YF-16 in 1974.
The Northrop YF-17 Cobra measured 56 ft in length and had a wingspan of 35 ft. Gross Take-Off Weight (GTOW) was 34,280 lbs. Power was provided by twin General Electric YJ101-100 afterburning turbofans, each generating 14,400 lbs of thrust. The aircraft had a maximum design speed of Mach 1.95, an unrefueled range of 2,600 nm and a service ceiling of 50,000 ft.
The accent on agility and maneuverability led designers to configure the YF-17 with leading edge strakes and twin vertical tails. The leading edge strakes helped alleviate asymmetric vortex shedding and the associated induced yawing moment at high angle-of-attack. Similarly, the twin vertical tails provided enhanced directional stability at high angle-of-attack flight conditions.
YF-17 Ship No. 1 (S/N 72-1569) first took to the air on Sunday, 09 June 1974. The aircraft displayed impressive performance, agility and handling qualitities. On Tuesday, 11 June 1974, the Cobra exceeded the speed of sound in level flight. This marked the first time in United States aviation history that an aircraft did so without using afterburner.
On Wednesday, 21 August 1974, YF-17 Ship No. 2 (72-1570) joined the Northrop LWF flight test force. Together, these two airframes flew 288 flight test sorties for a total of 345 flight hours. During the test program, the Cobra hit Mach 1.95, pulled 9.4 g’s and achieved a maximum altitude beyond 50,000 ft. The jet handled like a dream and lived-up to its advance billing in virtually every way.
Despite the YF-17’s great promise, it did not win the LWF fly-off with the YF-16. Competitions of this sort are often between equals and the final decision can go either way. Nuanced political factors and the like often determine the final outcome. Such was the case in this situation. Both aircraft were exceptional, but only one could be declared the winner.
Happily for American aviation, the YF-17 story did not end with the LWF loss. Indeed, the YF-17’s merits were so obvious to the aviation community that it received new life with the United States Navy. In May of 1975, the team of Northrop and McDonnell Douglas secured the Navy Air Combat Fighter (NAVF) contract to produce a remarkable aircraft that was a direct descendant of the YF-17 Cobra. We know that aircraft today as the F/A-18 Hornet.
Forty-one years ago this week, the last of the USAF/Boeing Thor Burner II launch vehicle series successfully orbited the SESP-1 space environment satellite. Launch took place from SLC-10W at Vandenberg Air Force Base, California on Tuesday, 08 June 1971.
The Thor Burner family of launch vehicles was designed to orbit classified meteorological satellites for the Defense Meteorological Satellite Program (DMSP). Launched into polar orbit, these satellites aided Keyhole spy satellite operations by ensuring that target imaging took place only over sparsely-clouded terrain.
The liquid-fueled Thor SM-75 missile served as the first stage of the Thor Burner launch vehicle. The Thor airframes selected for the program formerly stood sentinel in Europe in the Intermediate Range Ballistic Missile (IRBM) role. The Burner upper stages utilized solid propellant propulsion.
There were four (4) versions of Thor Burner as distinguished principally by the type of solid propellant rocket motor employed in the upper stage(s) and the orbitable payload mass. Thor Burner 1 used a single Altair-type solid motor upper stage which produced about 5,000 lbs of thrust for 27 seconds. The upper stage and satellite payload were spin stabilized. A total of six (6) Thor Burner I vehicles were flown.
Thor Burner II employed a single Star 37B solid motor which generated 10,000 lbs of thrust for 42 seconds. The upper stage had its own 3-axis flight control system that incorporated multiple hot and cold gas reaction jets. The solid rocket motor and satellite payload were contained within a hemispherically-blunted conical fairing that was colored a distinct orange-red. Thor Burner II flew twelve (12) times.
Thor Burner IIa was a three-stage configuration. A Star 37D (slightly less energetic than the Star 37B) solid motor powered the third stage which was accomodated through the addition of a cylindrical section inserted between the Thor first stage and the hemispherically-blunted conical fairing. Eight (8) Thor Burner IIa vehicles were launched.
The fourth and final Thor Burner variant was essentially a modified Thor Burner IIa vehicle. The second and third stages were now powered by a Star 37XE and Star 37S-IISS rocket motor, respectively. The shape of the external fairing was the same as that of the Thor Burner IIa, only a higher degree of nose blunting was used. A total of five (5) of these vehicles were flown.
The Thor Burner series flew from 1965 through 1980. Twenty-eight (28) of the thirty-one (31) missions were rated as successful. Indeed, the Burner concept proved so effective that variants thereof showed-up on the Atlas and Titan missile programs. Little-remembered today, the Thor Burner Program holds an important place in the annals of American aerospace history.
Fifty-one years ago this month, the United States Navy Strato Lab V manned balloon soared to a record altitude of 113,740 feet above the Gulf of Mexico. The crew for this historic flight was Commander Malcolm D. Ross, USNR and Lt Commander Victor G. Prather, USN.
Strato Lab was a United States Navy program to scientifically explore the upper reaches of the stratosphere using manned balloons. An additional focus of the program was the acquisition of aero medical data in support of the United States man-in-space effort.
A total of five (5) Strato Lab balloon flights took place from 1956 to 1961. Each Strato Lab mission was flown by a two-man crew with Malcolm Ross as the flight commander. The Strato Lab I, II, III, and IV aerial excursions attained maximum altitudes between 76,000 and 86,000 feet.
Strato Lab V, which took place on Thursday, 04 May 1961, achieved the highest altitude (113,740 feet) of the program. The purpose of this flight was to perform a maximum test of the Navy’s Mark IV full-pressure suit. As such, Ross and Prather flew in an open gondola with nothing save their individual Mark IV suits providing protection from the space-equivalent environment at high altitude.
Launch took place from the USS Antietam (CV-36) stationed out in the Gulf of Mexico. The size of the Strato Lab V balloon was truly immense. It sported a volume of 10,000 million cubic feet and measured 300 feet in diameter at float altitude. Despite extreme cold and various technical problems, the crew successfully made the trip upstairs in about two and a half hours.
Ross and Prather were sobered by the view they had of earth and space as well as the realization that no person had ever seen either from such a vantage point. They did not linger long before starting the trip home. Descent was largely uneventful. Splashdown occurred within a mile and a half of the USS Antietam. Mission time was 9 hours and 54 minutes.
As they waited for helicopter pick-up, the crew savored their safety, the success of their mission and the outstanding performance of the Mark IV full-pressure suit. Malcolm Ross was the first to be picked-up by the recovery helicopter. With some difficulty, he was safely retrieved from the water-borne Strato Lab V gondola.
Then tragedy struck suddenly and irrevocably as Prather was being hoisted into the helicopter. The naval officer slipped from the retrieval sling and fell into the water. Divers in the helicopter quickly jumped into the ocean in an effort to save Prather. Despite their rapid response, Victor Prather drowned. Ironically, the Mark IV suit, which just hours before had preserved life, now took that life away as it filled rapidly with sea water and dragged Prather below the surface.
For their significant efforts, Ross and Prather (posthumously) were awarded the 1961 Harmon Trophy for Aeronauts. The performance of the Mark IV suit was so outstanding that it served as the basis for the Project Mercury spacesuit. Interestingly, the day after the Strato Lab V mission, USN Commander Alan Bartlett Shepard became the first American in space during the sub-orbital flight of Freedom 7.
Thirty-six years ago this week, production unit No. 5,000 of the incomparable USAF/McDonnell F-4 Phantom II fighter-bomber was delivered in a public ceremony held at Lambert-St. Louis International Airport. This occasion (Wednesday, 24 May 1978) also marked the 20th anniversary of the type’s maiden flight (Saturday, 24 May 1958).
Rhino, Lead Sled, Flying Brick, Flying Anvil, Old Smokey, Double Ugly, The Hammer; such are among the many terms of endearment used by pilots, back seaters and crew chiefs to describe the fabled F-4 Phantom II. Perhaps no other military aircraft is as emblematic of the air warfare mission than this classic two-seater, twin-jet airframe.
Initially developed for the United States Navy, the Phantom was also employed by the U.S. Marine Corps, United States Air Force, and the air forces of many allied nations. As such, it served in numerous air warfare roles including fighter, bomber, attack, interceptor, defense suppression, and aerial reconnaissance. Indeed, over 50 variants of the F-4 were produced between 1958 and 1981.
The aircraft was Mach 2.2-capable with a service ceiling of 60,000 feet. At a GTOW of 41,500 lbs, the Phantom could carry an ordnance load of 18,650 lbs wherein combinations of air-to-air missiles, air-to-ground missiles and a variety of multiple-yield bombs were employed.
The Phantom was conceived in a time when reliance on missiles appeared to obviate the need for cannon in air combat engagegments. Subsequent air warfare experience in Viet Nam dictated otherwise and a centerline-mounted M61 Vulcan cannon was installed on the F-4E variant.
The Phantom was heavily used by the military services in southeast asia and proved to be extremely effective. So much so, that it gained an additional nickname as the “World’s Leading Distributor of MiG Parts”.
In its time, the Phantom also held many speed, altitude, and time-to-climb aircraft performance records. Noteworthy is the fact that the F-4 also holds the distinction of being the only aircraft flown by both the United States Air Force Thunderbirds and United States Navy Blue Angels flight demonstration teams.
Today, there are over 600 Phantoms still flying worldwide. In the United States, one is likely to see a Phantom in its natural element only at an air show. Even in an age when the F-15 Eagle, B-1B Lancer and F-22 Raptor grace the sky, it is a choice experience indeed to witness the mighty F-4 come by show center in full afterburner. Rhinos forever!
Forty-nine years ago today, the USAF/Northrop X-21A Laminar Flow Control (LFC) experimental aircraft exhibited a significant reduction in skin friction drag. This achievement marked the first time in aviation history that the LFC principle was successfully demonstrated in flight. Perhaps aviation’s greatest holy grail is the pursuit of technology that allows a laminar boundary layer to be maintianed over the entire surface of an aircraft. Doing so holds the promise of significantly reducing the overall drag and thereby markedly increasing aircraft range and endurance performance. Maintaining a laminar boundary layer is difficult since the boundary layer is naturally turbulent over most of the aircraft at flight Reynolds numbers. The X-21A LFC system was based on the principle of boundary layer removal. This was achieved by drawing surface airflow through a series of fine, porous slots machined into the upper and lower surfaces of the wing. Airflow suction was provided by laminar flow control pumps located in nacelles on the underside of the wing. A pair of existing USAF B-66D Destroyer airframes were converted to the X-21A LFC configuration. Following conversion and checkout, Ship No. 1 (S/N 55-0408) first flew on Thursday, 18 April 1963 with Northrop test pilot Jack Wells doing the honors. On this initial test hop, the X-21A flew from Northrop’s Hawthorne Airport facility to Edwards Air Force Base, California. The first successful flight demonstration of aircraft drag reduction occurred on Tuesday, 14 May 1963. Ultimately, the X-21A demonstrated laminar flow control on about 75% of the type’s wing surface. Aircraft handling was satisfactory even with asymmetric boundary layer state on opposing wings (i.e., one wing with laminar flow and the other with turbulent flow). However, the Achilles Heel of LFC is the natural flight environment itself wherein dust, dirt, particulates and even bugs clog the boundary layer suction slots. LFC system maintenance is a nightmare; laborious, time-consuming and expensive. While clearly successful, the X-21A LFC Program came to an end in 1964. Despite its promise and allure, no operational production aircraft has ever utilized an LFC system.
Fifty-nine years ago this month, the USAF/North American YF-100A Super Sabre air-superiority fighter made its maiden flight with North American test pilot George S. Welch at the controls. During this initial test flight, the Super Sabre exceeded the speed of sound. The North American F-100 Super Sabre was the successor to the fabled F-86 Sabre fighter. The Super Sabre holds the distinction of being the first of the 1950’s era Century Series aircraft. It was also the first USAF production aircraft capable of flying supersonically in level flight. A total of 2,294 copies of the Super Sabre in 18 variants were produced over an operational lifetime that spanned 25 years. The air forces of the United States, France, Denmark, Turkey and the Republic of China (Taiwan) flew the aircraft affectionately known as “The Hun” by its pilots. The YF-100A was the initial version of the F-100. Two copies were produced. Ship No. 1 (S/N 52-5754) first flew on Monday, 25 May 1953 at Edwards Air Force Base, California. The aircraft performed well and hit Mach 1.03 on this first flight. The Super Sabre entered the USAF active inventory in late 1954 and set a number of speed records early in its operational life. The type won the Bendix Trophy for flying 2,020 nm at an average speed of 610.726 mph in September of 1955. The F-100 was also the first USAF combat jet to enter the Vietnam War. The USAF Thunderbirds flew the Super Sabre from 1956 to 1968. In spite of these notable achievements and distinctions, the aircraft was plagued by numerous design deficiencies and shortcomings that had to be corrected before the type reached an acceptable level of maturity. Particularly vexing were roll inertial coupling issues at high speeds and pitch-up tendencies at low speeds. Indeed, the aircraft had a deserved reputation as a widow-maker starting early in its career. History records that 889 F-100 airframes were destroyed in mishaps of one kind or another. That translates to a stunningly-high loss rate of 38.75%. Soberingly, 324 pilots lost their lives flying The Hun. Progress in aviation sometimes comes at a very high price. The F-100 Super Sabre, unique in its day, now a relic of history, is a particularly profound example of this truism.
Forty-years ago this month, the United States successfully conducted the next-to-last Apollo lunar landing mission with the flight of Apollo 16. The lunar landing occurred in the densely-cratered Descartes Highlands region located near the Descartes crater.
On Sunday, 16 April 1972, Commander John W. Young, Command Module Pilot Thomas K. Mattingly II, and Lunar Module Pilot Charles M. Duke, Jr. lifted-off from Cape Canaveral’s LC-39A at 17:54:00 UTC. Apollo 16’s goal was to land in the lunar highlands whose surface material was older than that of the previously-visited lunar maria landing sites.
Apollo 16 entered lunar orbit in the 75th hour of the outbound flight. Young and Duke undocked their Lunar Module Orion from the Command Module Casper piloted by Mattingly just short of 96.5 hours into the mission. Slightly more than 8 hours later, Orion safely touched-down near Descartes crater at 2:23:35 UTC on Friday, 21 April 1972.
During their 71-hour lunar stay, Young and Duke conducted a trio of surface EVA’s to explore the Descartes region. Totaling more than 20 hours, these exploratory jaunts were facilitated by use of the motorized Lunar Rover that allowed the crew to venture as far as 2.7 miles from the Lunar Module.
Although too extensive to adequately report here, the astronauts’ exploratory discoveries were truly phenomenal and ultimately changed our understanding of the Moon’s geology. Young and Duke collected roughly 211 lbs of lunar surface samples. At 1:25:47 UTC on Monday, 24 April 1972, Orion and her crew lifted-off from the lunar surface and docked with Casper a little more than 2 hours later.
Following transfer of crew and cargo to Casper, Orion was jettisoned, and the 3-man crew remained in lunar orbit for almost a full earth day conducting experiments and surface observations before being rocketed back to Earth. The trip home and earth atmospheric entry were uneventful in the main.
Command Module splashdown took place at 19:45:05 UTC on Thursday, 27 April 1972 in the South Pacific Ocean. Crew, lunar cargo and spacecraft were safely recovered aboard the USS Ticonderoga some 37 minutes later.
Apollo 16 was a grand achievement both scientifically and technologically. Along with the other Apollo lunar landing missions, Apollo 16 reminds us what be accomplished when vision, commitment and hard work are brought to bear. Today, the lone Apollo 16 spacecraft component to return to Earth, the Command Module Casper, is on public display at the U.S. Space and Rocket Center in Huntsville, Alabama.
Forty-five years ago this month, the United States Air Force successfully flew and recovered the third and final Project PRIME Flight Test Vehicle (FTV-3). PRIME stood for Precision Recovery Including Maneuvering Entry. The ability to generate aerodynamic lift allows a reentry vehicle to maneuver along the endoatmospheric portion of its entry flight path. The main goal of Project PRIME was to flight test a hypersonic, maneuvering lifting body vehicle designated as the USAF/Martin SV-5D. Configured with 3-axis aerodynamic and reaction controls, the SV-5D weighed 892 lb and measured 6.7 ft, 4.0 ft and 2.8 ft in length, span and height, respectively. Thermal protection was provided by a then-novel charring ablator material. The SV-5D was an autonomous vehicle and thus had its own guidance, navigation and control system. On Wednesday, 19 April 1967, PRIME FTV-3 was launched by an Atlas booster from Vandenberg Air Force Base, California. The vehicle’s trajectory took it toward Kwajalein Missile Range (KMR) located 4,400 nm to the west in the Marshall Islands. FTV-3 performed a variety of controlled maneuvers during entry in which a maximum crossrange of 710 nm was achieved. The vehicle modulated crossrange by banking as much as 64 degrees while simultaneously pulling angles-of-attack as high as 57 degrees to achieve the required lift vector. Indeed, this very same crossrange maneuvering strategy would be used by the Space Shuttle Orbiter a decade and a half later. FTV-3 deployed a drogue parachute as it passed through Mach 2 at 100,000 feet. Main parachute deployment then occurred in the vicinity of 50,000 feet. As the vehicle-parachute combination neared an altitude of 12,000 feet, the crew of a USAF/Lockheed JC-130B Hercules then executed the only successful aerial recovery of a PRIME flight test vehicle. A planned fourth flight was cancelled due to the great success achieved in the preceding trio of PRIME flight tests. As a final note, FTV-3 was subsequently returned to the contractor for post-flight inspection and testing. Today, the recovered FTV-3 airframe is on public display at the United States Air Force Museum in Dayton, Ohio.
Fifty-years ago this week, future Apollo 11 Astronaut Neil A. Armstrong piloted the fifty-first and longest mission of the X-15 Program. The research flight was highlighted by Armstrong having to make a 180-degree turn over Los Angeles to recover the X-15 back at Edwards Air Force Base following a 45-mile overshoot of the intended landing area. X-15 Ship No. 3 (S/N 56-6672) was configured with the Honeywell MH-96 adaptive flight controller for the purpose of easing the pilot’s workload during atmospheric exit and entry. NASA test pilot Neil Armstrong was assigned responsibility to perform the early flight testing of this unit. On Friday, 20 April 1962, Armstrong made his fourth and last flight in Ship No. 3. Peak altitude and speed achieved during the flight was 207,447 feet and 3,788 mph (Mach 5.31), respectively. As Armstrong approached the Edwards area from the northeast, his trajectory ballooned anomalously. That is, rather that continuing to descend and scrub-off velocity, the X-15 climbed slightly and maintained an above-nominal speed. As he passed by Rogers Dry Lake heading south, Armstrong was still traveling at 100,000 feet and Mach 3. Armstrong banked the aircraft until it was practically inverted and invoked full elevator in an effort to get the X-15 to bite into the atmosphere and turn back towards Edwards AFB. However, it wasn’t until he was over Los Angeles, roughly 45 miles beyond the base, that he got the aircraft turned around. Now, would he have enough energy to glide back and touchdown on Rogers Dry Lake? Somehow, Armstrong managed his energy state properly and made it back to Edwards. But it was a close thing. Rather than making the standard overhead turn and landing on the north side of Rogers Dry Lake, Armstrong executed a straight-in approach and landed on the south side of the desert playa. Chase pilots are recorded to have said that he cleared the Joshua trees at the south end of Rogers Dry Lake by only about 100-150 feet. Nonetheless, pilot and aircraft were unscathed in what turned-out to be the longest flight in the history of the X-15 Program (12 minutes 28.7 seconds). In the post-flight joviality, fellow NASA test pilots reportedly referred to Armstrong’s adventure as “Neil’s cross-country flight”.
