N-I

The N-I, also written N-1, was a Japanese launch vehicle derived from the American Thor-Delta and produced under licence in Japan; the N stands for Nippon. It combined a Long Tank Thor first stage derived from the PGM-17 Thor intermediate-range ballistic missile, a second stage with the LE-3 engine designed by Mitsubishi Heavy Industries, and three Castor 2 solid rocket motors, with an optional Star-37N solid third stage that flew on three of its seven launches. The seven launches took place between 1975 and 1982 and six were successful; the fifth failed when the payload and the third stage collided shortly after separation. The second launch, on 29 February 1976, is the only orbital launch made on a leap day as of February 2024. The N-II replaced the N-I after 1982.