Project HARP, for high altitude research project, was a joint venture of the United States Department of Defense and Canada's Department of National Defence created with the goal of studying ballistics of re-entry vehicles and collecting upper atmospheric data for research. Unlike conventional space launching methods that rely on rockets, HARP instead used very large guns to fire projectiles into the atmosphere at extremely high speeds.
A HARP gun operated by the U.S. Army's Ballistic Research Laboratory (now called the U.S. Army Research Laboratory) at Yuma Proving Ground currently holds the world record for the highest altitude that a gun-fired projectile has achieved: , well above the Kármán line conventionally marking the beginning of outer space.
History
Preparations Project HARP originated as the brainchild of Gerald Bull, a renowned but controversial ballistic engineer specializing in high-velocity guns and gun propulsion systems. In the mid-1950s, Bull was working on anti-ballistic missile (ABM) and intercontinental ballistic missile (ICBM) research at the Canadian Armaments and Research Development Establishment (CARDE) when he formulated the idea to launch satellites into orbit using an enormous cannon. Bull believed that a large supergun would be significantly more cost-effective at sending objects into space than a conventional rocket. Bull argued it would not need expensive rocket motors, firing a large gun wouldn't require the missile to throw away multiple rocket stages to break through the Earth's atmosphere to reach orbit. In theory, a sabot would protect the payload during firing and later fall away as the satellite inside emerges.
During the late 1950s, Bull conducted preliminary launch experiments at the CARDE (now known as Defence Research and Development Canada – Valcartier, or DRDC Valcartier) using guns as small as 76mm. These experiments soon caught the attention of the U.S. Army's Ballistic Research Laboratory and the U.S. Army's Chief of Army Research and Development, Lieutenant general Arthur Trudeau. At the time, aircraft engineers needed more information on the atmosphere's upper regions to design better jet planes. However, launching rockets into the air to collect data was generally considered costly and inefficient. The U.S. military, in particular, was especially in need of a low-cost launch system that could cover altitudes that conventional aircraft and weather balloons couldn't reach to support the development of new supersonic aircraft and missile systems. By late 1960, CARDE and the Ballistic Research Laboratory (BRL) conducted several feasibility studies surrounding small gun-launched probes' structural integrity. Around the same time, BRL developed a smooth-bore, 5-inch gun system at Aberdeen Proving Ground that successfully launched a probe to altitudes exceeding 220,000 feet.
In 1961, Bull resigned from CARDE and McGill University hired him as a professor. Working together with Donald Mordell, the university's Dean of Engineering, Bull moved forward with his space gun project and requested funding from various sources. He received a $200,000 loan from McGill University's board of governors. He was given a verbal promise for a $500,000 grant from the Canadian Department of Defence Production (CDDP), which was later reportedly denied due to bureaucratic opposition. In October 1961, Bull met with Charles Murphy, the head of the Ballistic Research Laboratory, to pitch his project for a supergun and was met with overwhelming support. The U.S. Army provided Bull with substantial financial backing and two 16-inch naval gun barrels complete with a land mount and surplus powder charges, a heavy-duty crane, and a $750,000 radar tracking system. Bull and Mordell officially announced the HARP project as a program under McGill University's Space Research Institute at a press conference in March 1962. HARP was presented as a research initiative dedicated to "developing low-orbital capacity for geodetic and atmospheric objectives". However, the project's long-term goal was to place satellites into orbit economically.
Construction In 1962, Bull and Mordell established a McGill University research station on Barbados (then still a British colony and part of the West Indies Federation) as HARP's main base of operations for its 16-inch super gun. The site location was first suggested by Mordell, who believed that a launch site closer to the equator would allow the projectile to procure extra velocity from the Earth's rotation to reach higher altitudes. In addition, the site's close proximity to the Atlantic Ocean made for the safe impact of re-entry projectiles. As a result of McGill University's close connections with the island's Democratic Labour Party, Bull met with the Barbados Prime Minister Errol Barrow to arrange the construction of a firing site at Foul Bay, St. Philip. HARP reportedly received enthusiastic support from the Barbados government due to expectations that the island nation would become heavily involved in space exploration research.
The installation of the 16-inch gun began at the newly established High Altitude Research Facility in April 1962. A gun pit was dug into the island's coral base, and a concrete emplacement was built on a plateau so that the gun barrel could stand vertically. The 16-inch naval gun barrels provided by the U.S. Army served as the barrels of the HARP gun. They had to be transported to the site on the U.S. Army landing ship, the Lieutenant Colonel John D. Page, with the U.S. Army Transportation Corps assistance, the U.S. Army Research Office, and the Office of the Chief of Research and Development. Hundreds of people from Barbados were employed to transport the two 140-ton gun tubes from the coast to the designated emplacement 2 miles from the beach using a temporary purpose-built railway. By late 1962, the HARP 16-inch gun was set up, and construction on workshops, storage buildings, radar installations, and other facilities neared completion. Around this time, the U.S. Army Research Office increased its financial support of the project to $250,000 per year. The first test shot from the 16-inch gun on Barbados was fired on January 20, 1963, marking the first time that a gun of this caliber was fired at a near-vertical angle. The 315 kg test slug reached an altitude of 3000 meters with a flight time of about 58 seconds at a launch velocity of 1,000 m/s before coming down a kilometer off-shore.
Operations The projectiles fired by the 16-inch HARP gun on Barbados belonged to a family of cylindrical, finned missiles called Martlets, named after the martin bird that appeared on the McGill University crest. Inside the gun barrel, the Martlet was surrounded by a sabot. This machined wooden casing protected the projectile as it traveled through the barrel by absorbing the combustive energy and then splitting apart in the air after the Martlet exited the barrel. The Martlets also carried payloads of metallic chaff, chemical smoke, or meteorological balloons to gather atmospheric data as well as telemetry antennas for tracking the missile's flight. The Harry Diamond Laboratories designed several telemetry systems used in the HARP program. The firing of these Martlet missiles was always accompanied by a huge explosion that shook the houses within close proximity, leading to cracks in several areas. Since the Barbados government refused to recognize householders' damage claims, HARP fell into ill favor by much of the Barbados population.
From late January to early February 1963, the 16-inch gun on Barbados conducted its first test series using the Martlet 1, the first of which flew for 145 seconds and reached an altitude of 26 km. It was the first Martlet flight to feature a radio transmitter beacon that tracked the vehicle's flight. The second test series was conducted in April 1963 with the new Martlet 2 missiles, which set the world's new gun-launched altitude record of 92 km. Around the same time, development for the Martlet 3A began in the spring, with test launches commencing in September. By the end of 1963, approximately 20 Martlet 2 missiles were launched and regularly reached altitudes of 80 km. From these tests, researchers obtained a significant amount of atmospheric data as well as the internal ballistics of the 16-inch gun and the flight performance of the Martlet 2, 3A, and 3B. Impressed with the HARP program's initial results, the U.S. Army agreed to provide $250,000 per year in funding.
In 1964, the HARP gun on Barbados continued to primarily launch Martlet 2 missiles that carried a wide variety of payloads. Part of the reason was its low cost, since the firing of the Martlet 2 cost from $2500 to $3000 and took only half an hour to load. The new results from HARP convinced the U.S. Army to increase the annual funding of the project from $250,000 to $1.5 million per year. By March 1964, Canada's Department of Defence Production (DDP) agreed to provide joint funding for the HARP program for a total of $3 million per year. However, HARP funding reportedly faced several obstacles in the form of bureaucratic sabotage due to opposition in the Canadian government. The funding promised by the DDP for July 1, 1964, to June 30, 1965, did not arrive until May 1965. During this period, McGill University covered the funds to the best of its ability, although changes had to be made to the original plan. For each subsequent funding periods, the DDP repeatedly delayed HARP funding late into the fiscal year.
The first attempts to improve the performance of the 16-inch gun at Barbados were made in 1964, primarily by increasing the barrel's length. In 1962, the Ballistic Research Laboratory increased the barrel length of a 5-inch gun system by welding a second section of barrel to the first barrel's muzzle, lengthening the barrel to 8.9 meters. The resulting gun system demonstrated a higher muzzle velocity at the muzzle exit. The longer barrel allowed the propellant gases to push on the projectile for a longer period of time. In September 1964, a ten-calibers extension was added to the 16-inch gun based on BRL's experiment with the 5-inch gun. However, while increased velocity and altitude was recorded for test flights, the extension failed in December after the eleventh shot was fired. In 1965, a successful extension of the 16-inch gun was established after enlarging the gun pit to accommodate the equipment's large size. The extension almost doubled the length of the gun to 120 feet and weighed nearly 200 tons, making the 16-inch Barbados gun the largest operational artillery piece in the world at the time.
By the end of 1965, Project HARP had fired more than one hundred missiles at heights over 80 km high into the ionosphere. At this point, the project starting planning the launch of the Martlet 4, a projectile that used rocket jets that would ignite mid-flight to send the missile into orbit. For this endeavor, BRL designed the telemetry system that utilized Sun sensors to determine the projectile's altitude. This telemetry system would serve as an early precursor to the U.S. Army's Aeroballistic Dynamic Fuze (DFuze).
By 1966, the HARP program had established several different launch sites around the United States and Canada, including a second 16-inch HARP gun at the Highwater Range in Quebec and a third 16-inch HARP gun at Yuma Proving Ground, Arizona.
On November 18, 1966, the HARP gun operated by BRL at Yuma Proving Ground launched an 84-kg Martlet 2 missile at 2,100 m/s, sending it briefly into space and setting a world altitude record of 179 km. This feat has remained the world altitude record for any fired projectile.
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