HARP Gun (Photo by Peter . ... HARP, for High Altitude Research Project, was a study of the upper atmosphere by instruments shot from a cannon. ... The cannon which propelled the Martlet to the high atmosphere was the creation of Gerald Bull, a Canadian engineer who specialized in the design of cannon. ... When the cannon fired--its loud bang was heard all over Barbados--the airtight cover over the muzzle was blown away and the Martlet rose into the high atmosphere, to altitudes of 80-90 miles. ...