Editing Project HARP (section)

=== 5-inch gun systems ===
The 5-inch HARP guns were based on a modified [[120 mm gun M1|120&nbsp;mm T123 service gun]] and used by the [[Ballistic Research Laboratory]] before the HARP program in order to fulfill the needs of the U.S. military's Meteorological Rocket Network, a program dedicated to collecting atmospheric wind and temperature data. They were designed to carry a 0.9&nbsp;kg payload to an altitude of 65&nbsp;km, which consisted of radar reflective chaff to collect wind data and small [[radiosonde]]s that returned radio telemetry of information like temperature and humidity as they drifted back down under large parachutes.<ref name=":4" /><ref name=":15">{{Cite journal|last=Kampe|first=H.J.|date=October 1960|title=Meteorological Rocket Network: For Measuring Atmospheric Parameters up to 250.000|journal=Weatherwise|volume=13|issue=5|pages=192–195|doi=10.1080/00431672.1960.9940979|bibcode=1960Weawi..13e.192K }}</ref> This initial design for the 5-inch HARP gun reached an altitude of 130,000&nbsp;ft when tested in 1961.<ref name=":14" /> The 5-inch L70 smoothbore guns was the first vertical firing gun system developed under Project HARP.<ref name=":11" /> In 1962, a 10-ft extension was implemented for the 5-inch HARP gun by welding a second barrel section to the first, allowing it to launch projectiles at muzzle velocities of 1554&nbsp;m/s (5,100&nbsp;ft/sec) to altitudes of 73,100&nbsp;m (240,000&nbsp;ft).<ref name=":14" /> Throughout HARP, further modifications were made to the 5-inch gun, such as adding three sets of stiffening wires to maintain barrel alignment. Due to their small size, they were easily transported from their initial site at Aberdeen Proving Ground to different launch sites across North America and the Caribbean.<ref name=":4" /><ref name=":15" /> One of the 5-inch HARP guns was acquired by the Atmospheric Sciences Laboratory (which consolidated into the U.S. Army Research Laboratory in 1992) to measure the stratosphere's winds.<ref>{{Cite news|last=Kennedy|first=Bruce|url=http://www.wsmr-history.org/HandsAcrossHistory-02-15.pdf|title=Gun Probe Was Used To Study Winds|date=February 2015|work=Hands Across History|access-date=February 11, 2020}}</ref> The 5-inch gun was deemed successful as a low-cost launch system, costing only around $300 to $500 per launch.<ref name=":4" /> By May 1966, a total of the HARP program's 5-inch guns launched 162 flights at Wallops Island, 47 flights at White Sands Missile Range, 30 flights at Barbados, and 24 flights at Fort Greeley.<ref name=":14" />