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 flight of the vehicle. 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 great 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 initial results of the HARP program, the U.S. Army agreed to provide $250,000 per year in funding.