The N-I or N-1 was a derivative of the American Thor-Delta rocket, produced under license in Japan. The N stood for "Nippon" (Japan). It used a Long Tank Thor first stage, a Mitsubishi Heavy Industries-designed LE-3 engine on the second stage,^[3][4][5] and three Castor SRMs.^[2][6] Seven were launched between 1975 and 1982, before it was replaced by the N-II. Six of the seven launches were successful, however on the fifth flight, there was recontact between the satellite and the third stage, which caused the satellite to fail.

N-I

The N-I rocket[1]
Function	Carrier rocket
Manufacturer	McDonnell Douglas (design) Mitsubishi Heavy Industries (production)
Country of origin	United States (design) Japan (production)
Size
Height	34 metres (112 ft)[1]
Diameter	2.44 metres (8.0 ft)
Mass	131,330 kilograms (289,530 lb)[1]
Stages	2 or 3
Capacity
Payload to LEO
Mass	1,200 kilograms (2,600 lb)[1]
Payload to GTO
Mass	360 kilograms (790 lb)[1]
Associated rockets
Family	Delta
Launch history
Status	Retired
Launch sites	LA-N, Tanegashima
Total launches	7
Success(es)	6
Partial failure(s)	1
First flight	9 September 1975
Last flight	3 September 1982
Boosters – Castor 2
No. boosters	3[2]
Powered by	1 TX-354-3
Maximum thrust	258.9 kilonewtons (58,200 lbf)
Specific impulse	262 sec
Burn time	37 seconds
Propellant	Solid
First stage – Thor-ELT
Powered by	1 MB-3-3
Maximum thrust	866.7 kilonewtons (194,800 lbf)
Specific impulse	290 sec
Burn time	270 seconds
Propellant	RP-1/LOX
Second stage
Powered by	1 LE-3
Maximum thrust	52.9 kilonewtons (11,900 lbf)
Specific impulse	290 sec
Burn time	246 seconds
Propellant	NTO/A-50
Third stage (optional) – Star-37N
Powered by	1 solid
Maximum thrust	45 kilonewtons (10,000 lbf)
Specific impulse	290 sec
Burn time	42 seconds
Propellant	Solid
[edit on Wikidata]

Mock up of N-1

On 29 February 1976, the second N-I conducted the only orbital launch to occur on a leap day.^[7]