- Length: 34 m
- Diameter: 2.44 m
- Launch Mass: 131 T
- Low Earth Orbit Capacity: 1200 kg
The N-I was manufactured by Mitsubishi Heavy Industries with the first launch on 1975-09-09. N-I has 6 successful launches and 1 failed launches with a total of 7 launches. The N-I or N-1 was a derivative of the American Thor-Delta rocket, produced under licence in Japan. It used a Thor-ELT first stage, a Mitsubishi Heavy Industries-designed LE-3 engine was used as a second stage, and three Castor SRMs. Seven were launched between 1975 and 1982, before it was replaced by the N-II.