H-IIA/B – Space Launch Report

H-IIA/B - Space Launch Report

H-IIA and H-IIB are Japan’s primary launch vehicles.   H-IIA was an improved version of H-II, the country’s first liquid hydrogen fueled booster. H-IIB replaced the H-IIA single-engine first stage with a wider body, dual-engine stage. 


H-IIA/B  - Space Launch Report

Two-and-one-half stage H-II could boost 4 metric tons into geosynchronous transfer orbit (GTO). H-IIA could lift nearly 6 tonnes .  H-IIB could haul 8 tonnes.

National Space Development Agency of Japan (NASDA) launched the first H-II on February 3, 1994. Six more flew during the next five years. The first five H-IIs succeeded, but the last two failed. The rocket, which consisted of 4 meter diameter first and second stages augmented by a pair of segmented solid rocket boosters (SRBs), turned out to be both costly and complex. Cost reduction was the primary reason that NASDA developed H-IIA.


H-IIA/B  - Space Launch Report

The standard H-IIA, dubbed H2A202, used simplified, lower-cost core motors and new, single-segment, lower-cost strap-on solid rocket boosters (SRB-As) to put 4.1 tons into GTO or 10 tons into low earth orbit (LEO). H2A202 weighed 287 tons at liftoff, excluding payload, and stood 52.5 meters tall. During the first 100 seconds of flight, the rocket was powered by two SRB-A strap-ons producing 230 tons vacuum thrust each to augment the single LE-7A core stage engine’s 112 tons vacuum thrust.

LE-7A, a staged combustion cycle engine that could throttle, ignited on the launch pad and burned for 400 seconds. The single-chamber engine gimbaled for pitch and yaw control. Auxiliary jets, fed by low-mixture ratio gas from the main engine preburner mixed with hydrogen gas, provided first stage roll control.

The H-IIA second stage was modified in several ways from its H-II precursor. It was powered by a simplified, multi-restartable LE-5B LOX/LH2 engine, which provided 14 tons thrust for up to 534 seconds. LE-5B gimbaled for pitch and yaw control while the second stage reaction control system (RCS) used hydrazine jets for roll control during powered flight and for roll/pitch/yaw control during unpowered flight.

The second stage used a simplified structure, consisting of separate propellant tanks held together by 24 carbon composite support trusses. (H-II’s second stage tanks used a more difficult to manufacture common bulkhead.) The upper, 4-meter diameter second stage LH2 tank, built by Mitsubishi Heavy Industries (MHI), was essentially the same structure supplied by MHI to Boeing for its Delta III and Delta IV-M second stage LH2 tanks. An elliptical LOX tank, roughly 3 meters in diameter, sat below the LH2 tank and was housed within the intertank structure until the first stage fell away.

The H-IIA strap-down inertial guidance system, located on the second stage, controled the entire vehicle during flight.

H-IIA growth versions soon entered service. H2A2022, with two additional smaller solid strap on boosters (SSB), could boost 4.5 tons to GTO. H2A2024 used four SSBs to put 5 tons into GTO. H2A204, with four SRB-As, could put 6 tons into GTO.

Larger versious of H-IIA were studied, but dropped. Initial concepts for an H2A212 variant consisted of a standard H-IIA with a parallel liquid rocket booster (LRB) powered by two LE-7A engines, capable of boosting 6 tons to GTO. 

This was replaced by plans to build an “H-IIB” with a larger, 5.2 meter diameter first stage powered by two LE-7A engines. 

H-IIA was stacked vertically in the Yoshinobu Launch Complex Vehicle Assembly Building at Tanegashima, a building that was enlarged to two bays for the H-IIA program. On launch day it was rolled on a massive, rubber-wheeled mobile launch table to one of two seaside launch pads.

For H-IIA, a second pad was added near the original H-II pad. Tanegashima launches could take place only during 190 days each year during January-February and June-September, and November-December due to agreements with local fisherman.

The first H-IIA lifted off in 2001. After five successful missions, the sixth H-IIA, launched in 2003, failed to reach orbit. That failure occurred when one of two SRB-A boosters failed to separate. The root cause of this failure was an insulation burn-through on the SRB-A nozzle that allowed hot gases to damage a separation detonating fuse.

When the time came for the SRB-A to jettison, the fuse failed to fire and the solid booster remained attached to the first stage. The rocket continued to fly down range, with the second stage separating and starting, but the extra mass robbed the vehicle of so much velocity that it was not possible to reach orbit. A range safety destruct command was transmitted 11 minutes into the flight.

H-IIA successfully returned to flight with a beefed up SRB-A design in 2005.  In 2007, H-IIA F13 successfully launched Japan’s first large lunar orbiter, SELENE (KAGUYA),  “The largest lunar mission since the Apollo program”.  The SELENE complex weighed about 3.09 tonnes at liftoff, making it the heaviest lunar explorer since Luna 24 in 1976. 

H-IIA F14, a 2024 model used to launch the KIZUNA “Internet satellite” to GTO in 2008, used improved SRB-A booster nozzles and a new LE-5B-2 (improved LE-5B) second stage engine. 

The changes increased SRB-A vacuum specific impulse from 280 seconds to 282.5 seconds.  The LE-5B-2  engine provided 448 second specific impulse, a 1 second improvement from LE-5B.  The changes allow more payload.  KIZUNA weighed 4.85 tonnes at liftoff.  H-2A was formerly rated for only 4.7 tonnes to GTO.

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H-IIA/B  - Space Launch Report

H-IIB was developed to launch Japan’s H-II Transfer Vehicle (HTV), an unmanned spacecraft designed to haul cargo to the International Space Station.   HTV, which weighed up to 16.5 tonnes, could haul up to 6 tonnes of wet and dry cargo.

  H-IIB consisted of a 5.2 meter diameter core stage, powered by two LE-7A engines, that was augmented by four SRB-A strap on motors.  The second stage was essentially the same as the H-IIA version.  A new 5.1 meter diameter payload fairing was used for the initial HTV flights.

In addition to its LEO heavy lifting capability, the more powerful H-IIB rocket could lift up to 8 tonnes to GTO.  This ability made H-IIB the third most capable GTO launch vehicle in the world, after Delta IV Heavy and Ariane 5 ECA.  

Japan Aerospace Exploration Agency (JAXA) launched its first H-2B launch vehicle, carrying Japan’s first HTV ISS cargo spacecraft, from Tanegashima Space Center on September 10, 2009.  The 56.6 meter tall, 531 tonne 2.5 stage rocket lifted off from Yoshinobu Launch Pad 2 at 17:01 UTC to start H-2B Test Flight 1.  HTV-1 entered a 51.6 degree inclination low earth orbit about 15 minutes later.  

All four SRB-A boosters ignited on the pad and burned for 1 minute 50 seconds.  The twin LE-7A engines burned for 5 minutes 47 seconds.  The 4 meter diameter second stage, powered by a single LE-5B LOX/LH2 engine, burned for about 8 minutes 13 seconds to inject HTV-1 into orbit.  

Vehicle Configurations

(metric tons)
250 km x 30 deg [1]
250 km x 51.6 deg [2]
1800 m/s
from GEO*
(metric tons)
not including
H-IIA 20210 t [1]3.8 t2SRB-A + Stg1
+ Stg2 + PLF
53290 t
H-IIA 2022 4.2 t2SRB-A + 2SSB
+ Stg1 + Stg2
53 m320 t
H-IIA 2024 4.7 t
5.0 t**
+ Stg1 + Stg2
53 m350 t
348 t**
H-IIA 204 5.7 t4SRB-A + Stg1
+ Stg2 + PLF
53 m445 t
H-IIB 30416.5 t [2]8 t4SRB-A + H2BStg1
+ Stg2 + PLF
56.6 m531 t

Vehicle Components

1st Stage
1st Stage
2nd Stage
Diameter (m)2.5 m1 m4.0 m5.2 m4.0 m4.07 m5.1 m
Length (m)15.1 m14.9 m37.2 m38 m9.2 m12.0 m15 m
Propellant Mass (tons)66 t
65 t**
13.1 t101.1 t177.8 t16.9 t  
Total Mass (tons)77 t
75.5 t**
15.5 t114 t202 t20.0 t1.4 t3.2 t
Engine MfgrNissan      
Oxidizer LOXLOXLOX  
(SL tons)
(Vac tons)
230 t75.97 t112 t223.9 t14 t  
ISP (SL sec)      
ISP (Vac sec)280 s
282.5 s**
282 s440 s440 s447 s
448 s**
Burn Time (sec)100 s60 s397 s352 s530 s  
No. Engines11121  

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