N-1, N-2, and H-1: Japan's "Deltas"
Eleventh in a Series Reviewing Thor Family History
by Ed Kyle, Updated 9/15/2009
H-1-2 stands on its Tanegashima pad in 1987.
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
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
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
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.
The first N-2 launch in 1981
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
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