N-1, N-2, and H-1 : Japan’s Deltas

N-1, N-2, and H-1 : Japan's Deltas

H-1-2 stands on its Tanegashima pad in 1987.

N-1, N-2, and H-1 : Japan's "Deltas"

From 1975 through 1992, it was possible to see “Delta” lookalike rockets liftoff from Tanegashima, Japan, a place regarded by many to be the world’s most beautiful launch site. During that span, the National Space Development Agency of Japan (NASDA) launched 24 Thor-family rockets assembled under license from the U.S.

The U.S. rockets provided a reliable method for NASDA to gradually develop its own orbital launch vehicle technologies. NASDA worked its way through three model variations, each fitted with more components developed or produced in Japan.

The N-1 (“N” stood for “Nippon”) rocket, launched from 1975 through 1982, was essentially a Long Tank Thor Delta with three Castor 2 boosters, creating an approximate Delta M copy.

A Rocketdyne MB-3-3, licensed to Ishikawajimi-Harima Heavy Industries (IHI), powered the first stage. Mitsubishi Heavy Industries (MHI) held the license from McDonnell Douglas for the first stage. Nissan had the license for the Thiokol Castor 2 strap on and Star 37N third stage solid motors. Export restrictions required the U.S. companies to build some of the critical assemblies while providing technical assistance for Japanese production of other hardware.

N-1-1 Prepares for Launch in 1975

N-1, N-2, and H-1 : Japan's "Deltas"

An MHI built LE-3 engine powered the second stage. LE-3 burned nitrogen tetroxide and Aerozine-50 to produce 5.44 tonnes of thrust with a 285 second specific impulse for up to 250 seconds. A Star 37N solid motor served as the N-1 third stage. The rocket used radio-inertial guidance and was topped by an Agena payload fairing. N-1 stood 32.57 meters tall, weighed 90.4 tonnes at liftoff not including payload, and could lift 1.2 tonnes to LEO or 0.36 tonnes to GTO.

N-1 lifted off from a new “N” launch complex at Tanegashima built as a near-copy of the Delta Cape Canaveral pads. Seven N-1 rockets flew, achieving six successes, during the 1975 to 1982 period. Notable successes included Japan’s first geostationary orbit launch, of Kiku 2 (ETS-2) on February 23, 1977. The lone launch vehicle failure occurred on February 6, 1979 when the fifth N-1’s Star 37N third stage collided with its Experimental Communications Satellite (ECS-A) satellite payload shortly after spacecraft separation. The follow up launch of ECS-B the following year was successful from a launch vehicle perspective (the sixth N-1 put its payload into GTO) but the satellite’s apogee kick motor catastrophically failed when it was fired to lift ECS-B into geostationary orbit.

Also read: Extended Long Tank Delta

The first N-2 launch in 1981

N-1, N-2, and H-1 : Japan's "Deltas"

NASDA’s N-2 was essentially an Extended Long Tank “Straight Eight” Delta, with nine strap on motors. The rocket used the MB-3-3 engine rather than the more powerful RS-27 used by equivalent U.S. Deltas. It used an upper stage Aerojet AJ10-118FJ engine that was improved from previous versions flown on U.S. Deltas. A Star 37E served as a third stage motor. N-2 used inertial guidance and a U.S. built 2.44 meter diameter payload fairing. The rocket stood 35.36 meters tall, weighed 135.2 tonnes not including payload, and could launch 2 tonnes to LEO or 0.73 tonnes to GTO.

Eight N-2 rockets lifted off from the “N” pad during the 1981-1987 period. All succeeded.

H-1, which began flying in 1986, was a radical departure from NASDA rockets based on NASA’s “workhorse” family. It replaced the pressure fed hypergolic fueled second stage with a new NASDA-developed common bulkhead liquid hydrogen fueled second stage that was powered by a brand new NASDA-developed LE-5 engine built by MHI and IHI. The rocket was controlled, for the first time, by an inertial guidance system developed in Japan.

The 2.49 meter diameter, 10.32 meter long second stage weighed 10.6 tonnes fueled with 8.8 tonnes of propellant. LE-5 was a gas generator cycle engine that produced 10.57 tonnes of thrust at a 450 second specific impulse during a burn that could last 357 seconds.

H-1, which weighed 135 tonnes at launch, could lift 3.2 tonnes to LEO or 1.1 tonnes to GTO. The rocket flew from the “N” pad, using a new umbilical tower. The old umbilical tower continued to stand on the opposite side of the pad so that N-2 launches could continue for several years after H-1 entered service. The last of nine H-1 rockets flew in 1992. All were successful.

H-1 provided a substantial payload increase over N-2 and served as a stepping stone to Japan’s subsequent home-built H-2 launch vehicles. For a time during the post-Challenger accident period, McDonnell Douglas considered adopting Japan’s upper stage, or at least the LE-5 upper stage engine, for use on U.S. Delta launch vehicles.

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