H-IIA, Japan’s largest space launcher, is an improved version of H-II, the country’s first liquid hydrogen fueled booster. Two-and-one-half stage H-II could boost 4 metric tons into geosynchronous transfer orbit (GTO). It consisted of 4 meter diameter first and second stages, augmented by a pair of solid rocket boosters (SRBs).
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 turned out to be both costly and complex. Cost reduction was the primary reason that NASDA developed H-IIA.
The standard H-IIA, dubbed H2A202, uses 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 weighs 287 tons at liftoff, excluding payload, and stands 52.5 meters tall. During the first 100 seconds of flight, the rocket is 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 can throttle, ignites on the launch pad and burns for 400 seconds. The single-chamber engine gimbals for pitch and yaw control. Auxiliary jets, fed by low-mixture ratio gas from the main engine preburner mixed with hydrogen gas, provide first stage roll control.
The H-IIA second stage was modified in several ways from its H-II precursor. It is powered by a simplified, multi-restartable LE-5B LOX/LH2 engine, which provides 14 tons thrust for up to 534 seconds. LE-5B gimbals for pitch and yaw control while the second stage reaction control system (RCS) uses hydrazine jets for roll control during powered flight and for roll/pitch/yaw control during unpowered flight.
The second stage uses 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), is 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, sits below the LH2 tank and is housed within the intertank structure until the first stage falls away.
The H-IIA strap-down inertial guidance system, located on the second stage, controls the entire vehicle during flight.
At least three H-IIA growth versions are available. H2A2022, with two additional smaller solid strap on boosters (SSB), can boost 4.5 tons to GTO. H2A2024 uses four SSBs to put 5 tons into GTO. H2A204, with four SRB-As, can put 6 tons into GTO.
Also read: H-IIA/B – Space Launch Report
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. With four SRB-A strap-on boosters, H-IIB will be able to boost 8 tonnes to GTO or 16.5 tonnes to low earth orbit (LEO). H-IIB is expected to fly beginning in 2008.
H-IIA is 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 is 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 can only occur 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.
Vehicle Configurations
| LEO Payload (metric tons) 250 km x 30 deg | GTO Payload 1800 m/s from GEO* (metric tons) | Configuration | LIftoff Height (meters) | Liftoff Mass (metric tons) | |
| H-IIA 202 | 10 t | 3.8 t | 2SRB-A + Stg1 + Stg2 + PLF | 53 | 290 t |
| H-IIA 2022 | 4.2 t | 2SRB-A + 2SSB + Stg1 + Stg2 + PLF | 53 m | 320 t | |
| H-IIA 2024 | 4.7 t 5.0 t** | 2SRB-A + 4SSB + Stg1 + Stg2 + PLF | 53 m | 350 t 348 t** | |
| H-IIA 204 | 5.7 t | 4SRB-A + Stg1 + Stg2 + PLF | 53 m | 445 t |
* GEO: Geosynchronous Earth Orbit
** Beginning with F14
Vehicle Components
| SRB-A (each) | SSB (each) | H-IIA 1st Stage | H-IIA 2nd Stage | Payload Fairing | |
| Diameter (m) | 2.5 m | 1 m | 4.0 m | 4.0 m | 4.07 m |
| Length (m) | 15.1 m | 14.9 m | 37.2 m | 9.2 m | 12.0 m |
| Propellant Mass (tons) | 66 t 65 t** | 13.1 t | 101.1 t | 16.9 t | |
| Total Mass (tons) | 77 t 75.5 t** | 15.5 t | 114 t | 20.0 t | 1.4 t |
| Engine | SRB-A | SSB | LE-7A | LE-5B LE-5B-2** | |
| Engine Mfgr | Nissan | ||||
| Fuel | Solid | Solid | LH2 | LH2 | |
| Oxidizer | LOX | LOX | |||
| Thrust (SL tons) | |||||
| Thrust (Vac tons) | 230 t | 75.97 t | 112 t | 14 t | |
| ISP (SL sec) | |||||
| ISP (Vac sec) | 280 s 282.5 s** | 282 s | 440 s | 447 s 448 s** | |
| Burn Time (sec) | 100 s | 60 s | 397 s | 530 s | |
| No. Engines | 1 | 1 | 1 | 1 |
