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N-I and N-II

Since 1975 NASDA has been conducting a parallel program of launching Japanese satellites for space technology and applications purposes using liquid-propellant vehicles. The original N-series (N-I and N-II) launch vehicles were developed under license from the US and were closely related to the Delta launchers. Flown during 1975-1987, the N-series was replaced by the H-l launch vehicle (first flight in 1986), a hybrid US-Japanese design.

N-I rocket is three-stage launch vehicles employing the U.S "Thor-Delta Rockets" technology and used for launching experiments, communications, broadcasting, meteorological and earth observation satellites. The Thor was originally designed as an Intermediate Ballistic Range Missile (IRBM) in December 1954 and first flew in 1957. In 1959, the newly formed NASA asked Douglas to create a civilian launch vehicle based on Thor Able. The new rocket was presenting the fourth configuration for the Thor, so it was named Delta - the military code for the fourth letter of the alphabet. The Delta M (introduced in 1968) represented siginificant leap in Delta evolution. With its Long Tank Thor first stage it hardly resembled the original Thor. The long, untapered tanks siginificantly increased propellant capacity. The Thor and Delta series of rockets became the workhorse of the American space program and launched more satellites than any other rocket family.

Mitsubishi Heavy Industries has played an important role in the development and manufacturing of Japanese space transportation systems from early on. MHI took part in the development of the N-I launch vehicle starting in 1971. NASDA developed its first N-1 launch vehicles 1 (N for Nippon) from the first stage of the Thor Delta M rocket built by Mitsubishi under license from McDonnell-Douglas. The second stage was made in Japan with an American engine and also used liquid propellants. The launch vehicle was completed by a third stage using solid propellant and 3 strap-on boosters, also based on American technology. The N-I launcher carried between 100-130kg (225-300 pounds) into geostationary orbit. N-I was utilized in a total of 7 launches from 1975 to 1982.

N-II rocket is three-stage launch vehicles employing the U.S "Thor-Delta Rockets" technology and used for launching experiments, communications, broadcasting, meteorological and earth observation satellites. The N-II was based on the Extended Long Tank Thor which had an eight foot in diameter booster. The first stage was built by Mitsubishi Heavy Industries (MHI) under license from Douglas. The main engine was a Rocketdyne licensed MB-3 built by Ishikawajima-Harima Heavy Industries (IHI) and generated 172,000 pounds of thrust. The first stage is supplemented by a ring of nine solid fuel Castor-2 engines. The second stage of the N-II used a re-startable Aerojet AJ10-118F built in Japan by IHI. The third stage engine was built by Nissan, which licensed the Thiolkol 364-4 rocket. The N-II, which was heavily dependant upon American technology and export regulations, could carry about 350kg. (770 pounds) into geostationary orbit which was nearly three times as the predecessor N-I launcher. The N-II had eight flights between 1981-1987, all of which were successful. KIKU-3(ETS-IV) confirmed N-II launch vehicle capability prior to the launching of 350-kg class geostationar meteorological, communications and broadcasting satellites and it performed testing of on-board equipment. N-II was utilized in a total of 8 launches from 1981 to 1987.

	N-I	N-II
Overall length	32.57m	35.36m
Diameter	2.44m	2.44m
Total weight	90.4t (Payload not inclued)	135.2t (payload not included)
Guidance system	Radio guidance system	Inertial guidance system