Hopes for the future of Japan's troubled space programme rest with a simplified and cut-price version of its H-2 launcher

Andrzej Jeziorski/TOKYO


The 20th century closed on a low point for Japan's National Space Development Agency (NASDA). Two failures of its expensive H-2 expendable launch vehicle not only cost it dearly in financial terms, but damaged the credibility of Japan's commercial satellite launch capability. A major rethink of space spending was needed.

The first accident, in February 1999, happened because of a second stage engine chamber break. The second, involving H-2 No 8, took place on 15 November and was blamed on cracks in a fuel tank or combustion chamber.

This last loss cost NASDA, the Civil Aviation Bureau and the Meteorological Agency ¥34.3 billion ($318.8 million) and led to the cancellation of the remaining planned H-2 launch and the suspension of other NASDA programmes. The funding that would have gone to the suspended programmes has been rechannelled into NASDA's potential saviour: the lower cost, higher capability, H-2A launch vehicle.

The H-2 was never commercially attractive from the customer's point of view, but NASDA hopes that the H-2A will be. The agency spent ¥2.7 trillion of government money between 1983 and 1993on developing the H-2 and found that each launch cost ¥19 billion. Since 1996 it has spent another ¥90 billion developing the H-2A in the hope of halving the launch cost.

"[The H-2] was very expensive compared with other launch vehicles - for example, the Ariane, Atlas and Proton launchers," says Mamoru Endo, acting director of the space transportation planning department of NASDA's Office of Space Transportation Systems. Endo says the cost in yen was more or less what NASDA had expected from the start, but the US dollar exchange rate plummeted during the launcher's development, from ¥240 to about ¥100. This meant that the launcher became expensive to international customers.

Bigger successor


The H-2 was developed as a larger, 260t successor to the 140t, three-stage H-1, which was designed to launch 550kg (1,210lb) loads into geostationary orbit. Nine satellites were launched by the H-1 between 1986 and 1991. It was the first launcher to incorporate an indigenously developed liquid oxygen/liquid hydrogen (LOX/LH) engine, the LE-5, in its second stage. Endo says LOX/LH propulsion is over 1.5 times more efficient than other liquid-fuelled rockets, but difficulties arise from the low temperature at which LH evaporates - about -250°C. The first stage was powered by a LOX RJ-1-fuelled engine, similar to NASDA's earlier N-1 and N-2 rockets.

Both stages of the H-2 were also powered by LOX/LH engines, built by Mitsubishi Heavy Industries (MHI) - the lower stage by the specially developed LE-7 and the upper stage by the LE-5A, a development of the H-1's second stage engine. With two strap-on solid rocket boosters (SRBs), also built by MHI, the vehicle was designed to be able to place a 2t satellite in geostationary orbit.

But with two failures in seven launches since 1993, the launcher has a poor record. With both of last year's failures blamed on the propulsion system, NASDA and the government are looking at quality control in launch vehicle production. With the more recent failure on 10 February of the third launch of an M-5 rocket, developed by the Japanese education ministry's Institute of Space and Astronautical Sciences, the government and space agencies face the prospect that there could be a more fundamental flaw in the Japanese space programme.

As a result, the first launch of the more capable H-2A, set for last month, has been delayed to 2001. In the meantime, additional verification tests will be run on the new launcher's engines and SRBs. Space industry officials hope that, with the additional funding and manpower diverted from other NASDA programmes, the satellite launch industry in Japan will be saved by the H-2A's success. In the meantime, they admit that the industry remains in a "very, very dangerous" position.

Simplicity and reliability

The H-2A's design aims for simplicity and reliability, with the most obvious differences in its MHI-built engines and boosters. NASDA predicts that its basic launch configuration - named H2A202, with two SRB-A boosters - will have a reliability of over 0.97. A planned heavyweight development of the rocket, with an additional external liquid rocket booster (LRB) - called H2A212 - will have a reliability exceeding 0.96. The agency qualifies these predictions, however, by saying that they are made with a "confidence level" of 60%.

The H-2A's first stage is powered by the improved LE-7A LOX/LH-fuelled engine, which provides 247,000lb of thrust (1,100kN) - substantially more than the H-2's LE-7 engine, which generated 190,00lb of thrust at sea level. Manufacture of the engine and of the first stage has been simplified by increased use of casting and machining, and less welding, to reduce costs and risk.

The H-2's SRBs were made from polybutadiene composite shells and generated about 350,000lb of thrust each. The H-2A's SRB-A boosters are also composite, but, while Endo says that the original H-2 SRB was made in four steel casing segments, each SRB-A is built as a single unit of polybutadiene composite. This technology was imported from the USA's Thiokol, which provided the machinery and know-how, says Endo.

The new materials and manufacturing process cut weight and increase structural integrity. The SRB-As also generate 507,000lb of thrust each, compared with the original SRB's 350,000lb.

The second stage is powered by the 31,000lb-thrust LE-5B engine, which is slightly more powerful than the 26,400lb-thrust LE-5A. Apart from the increased thrust, the key difference between the two is in the construction of the LOX and LH fuel tanks. In the H-2, the tanks were manufactured together as a single welded unit, with the larger LH tank fixed to the top of the LOX tank. The tanks are now fabricated as separate units for ease of manufacture and for safety. There is, however, a weight penalty to be paid for this change, says Endo.

Foreign technology

"When we developed the H-2, the target was 100% Japanese manufacture, but in the H-2A we decided to use foreign technology and materials," says Endo. For example, some components of the second stage fuel tanks are imported from the USA. This outsourcing, as well as the increased use of commercial off-the-shelf components, from both Japanese and foreign suppliers, has helped to keep costs down.

The H-2A uses a strap-down inertial guidance and control system, similar to the H-2's, comprising a newly developed inertial measurement unit, using ring laser gyros and a guidance control computer. These control thrust vectoring in the engine nozzles of both stages, while the second stage has an additional gas jet reaction control system.

The vehicle has been fitted with a simplified electrical system, featuring a 1553B databus. Japanese electronics and computer giant NEC is providing much of the on-board computer and telemetry equipment, while the inertial measurement system comes from Japan Aviation Electronics Industry. The H-2A is fitted with an automated diagnostic system, intended to reduce pre-launch processing time dramatically.

All these innovations and modifications are intended to cut the H-2A's launch costs to about half of the H-2's - to about ¥8.5 billion. If all works well, NASDA proposes a family of launch vehicles, with capabilities far exceeding anything Japan has launched to date. The H2A202, H2A2022 and H2A2024 configurations will be able to put 4-4.5t payloads in geostationary transfer orbit (GTO), with the extra launch thrust provided by up to four solid strap-on boosters as well as the two SRB-As.

The LRB-equipped H2A212 allows an extra 3.5t of payload, giving a 7.5t capability to GTO, with NASDA planning an enlarged payload fairing for this configuration. The LRB itself is powered by two LE-7A engines. The agency plans the first launch of this configuration a year after the first H-2A launch. NASDA is also studying a further augmented configuration, H2A222, with two LRBs as well as the SRB-As, which would offer a 9.5t-to-GTO capability.

Whether any of these developments see the light of day depends largely on the success of the H-2A's first launch in a year's time. Payload space is reserved by Hughes and Loral, which will only turn into real contracts if the first two launches go smoothly.

Source: Flight International