Encyclopedia Astronautica
7 inch HARP Gun



7a5prob2.jpg
HARP 7 & 5 in probes
From left to right: HARP 7-1, 7-2, 5-1, and 5-3.
Canadian gun-launched sounding rocket. The highly successful 5 inch HARP gun had demonstrated the immense versatility of small portable gun systems for atmospheric exploration. The 7 inch HARP gun system represented the 5 inch system scaled up to the largest barrel size practical, while still remaining portable.

The 7 inch gun launcher was created by smooth boring a 175 mm gun and extending it in a similar manner as the 5 inch gun system. The completed gun barrel was 16.8 m (55 feet) long (7 inch L 92.4) and was installed in a modified T-76 mount. Two of the new guns were constructed. The 7 inch guns had 3 times the payload capacity of the 5 inch guns and an altitude capability in excess of 100 km. The 7 inch guns filled the altitude gap between the maximum 5 inch gun altitude and the minimal attractive altitude for 16 inch gun probes.

The original HARP 7-1 gun probe was fundamentally a scaled up version of the 5-1 gun probe and was used for similar payloads.. The 7-1 probe had a mean diameter of 91 mm, a length of 1640 mm, and a flight weight of 27.3 kg. The vehicle was launched at a velocity of 1650 m/s (5400 ft/sec) with a 50 kg (110 lb) charge of M17 propellant.

The 7-1 probe, although serviceable as an atmospheric tool, failed to reach its theoretical apogee in test flights. Although directly scaled from the 5-1 vehicle, it was not optimal for the 7 inch gun ballistics and was simply too heavy. A new vehicle was designed to take these factors into account and the 7-2 probe was created.

The Harp 7-2 vehicle was an optimised version of the 7-1 vehicle. The 7-2 had a body diameter of 76 mm a length of 1410 mm a flight weight of 18.2 kg and a payload volume of 2048 cc. The 7-2 prove was designed with a much-improved streamlined shape and exhibited far cleaner aerodynamics. The smaller 7-2 probe was capable of reaching altitudes of 105 km which allowed it to carry payloads through the D-layer and into the lower E-layer of the ionosphere - the very edge of space itself.

The 7-2 probe was used for a multitude of payloads including the standard ejectable chaff flown in the 5-1 probes. Of note was the 7-2 probe's ability to carry chemical payloads such as caesium nitrate, which was used to create artificial electron clouds, and to carry Langmuir probes with associated radio telemetry.

The 7 inch gun system proved to be an economical and versatile system. It was not long after HARP began to explore the feasibility of gun-launched rockets that a rocket boosted vehicle was proposed for the 7 inch gun system.

The gun-launched rocket vehicle for the 7 inch gun system was called the Martlet 3E. The Martlet 3E vehicle was a full bore rocket assisted vehicle 2248 mm long with a flight weight of 61.2 kg and a rocket fuel weight of 42.6 kg.

The development of the Martlet 3E vehicle was nearly complete when funding for the HARP program was cancelled and it would have become operational the year following the end of the program. The Martlet 3E vehicle was capable of carrying a 20 kg payload to an altitude of 250 km which was well in excess of the 16 inch Martlet 2C vehicle's performance. With its portable 7 inch gun the Martlet 3E would have allowed high altitude soundings to be conducted from a vast number of sites around the world. With a launch cost similar to that of the Martlet 2 series, the Martlet 3E would have replaced the Martlet 2, freeing up the fixed 16 inch guns so that they could be dedicated to satellite launches. It is interesting to note that even today HARP's 7 inch gun system could fulfil many of the current research requirements for a cost per flight much less than that of conventional sounding rockets..

The 7 inch HARP gun system proved to be a valuable atmospheric research tool with some 60 operational flights over a 3 year period. Perhaps the least recognised gun system of the HARP program, the 7 inch HARP guns were poised to prove just how versatile and valuable a research tool they could have been when, in 1967, the HARP project abruptly ended leaving their true potential unfulfilled.

by Richard K Graf

Payload: 18 kg (39 lb) to a 105 km altitude. Launch data is: incomplete. Launch Price $: 0.001 million in 1962 dollars.

AKA: High Altitude Research Project.
Status: Retired 1966.
Payload: 18 kg (39 lb).
Height: 1.41 m (4.62 ft).
Diameter: 0.18 m (0.59 ft).
Apogee: 105 km (65 mi).
First Launch: 1965.11.22.
Last Launch: 1966.02.25.
Number: 17 .

More... - Chronology...


Associated Countries
Associated Spacecraft
  • HARP 7-1 Canadian earth atmosphere suborbital probe. Flights from 1961. The original HARP 7-1 gun probe was fundamentally a scaled up version of the 5-1 gun probe and was used for similar payloads. More...
  • HARP 7-2 Canadian earth atmosphere probe. Study 1961. The Harp 7-2 vehicle was an optimized version of the 7-1 vehicle. The 7-2 had a body diameter of 76 mm a length of 1410 mm a flight weight of 18.2 kg and a payload volume of 2048 cc. More...

See also
  • Gun-launched Artillery dominated military ballistics from the earliest use of gunpowder. In 1865 Jules Verne could only realistically consider a cannon for a moon launch in his influential novel. Even after the rocket established its primacy as a method of accessing space, Canadian Gerald Bull began a life-long struggle to use guns for cheap access to space. His successes could not generate funding to continue. Others since then have pursued the technology, convinced it was the only way for low-cost delivery of payloads to orbit. More...

Associated Manufacturers and Agencies
  • Bull Canadian manufacturer of rockets, spacecraft, and rocket engines. Bull, Canada. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.

Associated Launch Sites
  • Wallops Island Small NASA launch site for sounding rocket launches and occasional Scout launches to orbit. Air launches are conducted from the Drop Zone Wallops Island, 37.00 N 72.0 W. With the last orbital launch in 1985 and the decline in sounding rocket launches, Wallops fell into near-disuse as a launch center. Its fortunes revised with the establishment of Mid-Atlantic Regional Spaceport in 2005 and orbital launches resumed in 2010. More...
  • Barbados Sounding rocket launch site located on island in the Caribbean. It was also from here that Gerard Bull tested his Martlet series of gun-launched sounding rockets. Known to have been used for 40 launches from 1963 to 1968, reaching up to 150 kilometers altitude. More...
  • Barbados Sounding rocket launch site located on island in the Caribbean. It was also from here that Gerard Bull tested his Martlet series of gun-launched sounding rockets. Known to have been used for 40 launches from 1963 to 1968, reaching up to 150 kilometers altitude. More...

Associated Stages
  • HARP-1 Solid propellant rocket stage. Loaded mass 100 kg. More...

7 inch HARP Gun Chronology


1965 November 22 - . 23:09 GMT - . Launch Site: Barbados. Launch Vehicle: 7 inch HARP Gun.
  • MAXWELL Aeronomy mission - . Nation: USA. Agency: USAF. Apogee: 100 km (60 mi).

1965 November 23 - . 03:59 GMT - . Launch Site: Barbados. Launch Vehicle: 7 inch HARP Gun.
  • PARAGON Aeronomy mission - . Nation: USA. Agency: USAF. Apogee: 100 km (60 mi).

1965 November 23 - . 06:31 GMT - . Launch Site: Barbados. Launch Vehicle: 7 inch HARP Gun.
  • QUEENS FORT Aeronomy mission - . Nation: USA. Agency: USAF. Apogee: 100 km (60 mi).

1965 November 23 - . 08:28 GMT - . Launch Site: Barbados. Launch Vehicle: 7 inch HARP Gun.
  • ROCKLEY Aeronomy mission - . Nation: USA. Agency: USAF. Apogee: 100 km (60 mi).

1965 November 23 - . 10:16 GMT - . Launch Site: Barbados. Launch Vehicle: 7 inch HARP Gun.
  • SEAWELL Aeronomy mission - . Nation: USA. Agency: USAF. Apogee: 100 km (60 mi).

1966 February 2 - . 17:35 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 53 km (32 mi).

1966 February 7 - . 16:00 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 46 km (28 mi).

1966 February 8 - . 18:16 GMT - . Launch Site: Wallops Island. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 8 - . 19:58 GMT - . Launch Site: Wallops Island. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 11 - . 16:00 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 46 km (28 mi).

1966 February 16 - . 17:00 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 20 - . 21:53 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 23 - . 22:38 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 24 - . 03:23 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 24 - . 06:16 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 24 - . 16:00 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

1966 February 25 - . 16:00 GMT - . Launch Site: Barbados. Launch Complex: Barbados HARP. Launch Vehicle: 7 inch HARP Gun.
  • Aeronomy mission - . Nation: Canada. Agency: HARP. Apogee: 60 km (37 mi).

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