Kanichi Amano/TOKYO Andrzej Jeziorski/SINGAPORE

When the Japanese Ministry of International Trade and Industry (MITI) approved funding for a new supersonic engine demonstrator programme, Tokyo once again proved its readiness to put real money behind the development of technology for a new supersonic transport (SST) aircraft.

In September, the MITI cleared ´2.7 billion ($20 million)to cover the first year of a five-year follow-on programme to the current Hypersonic Transport Propulsion System Research (HYPR) programme, which ends with this fiscal year on 31 March 1999. This so-called "post-HYPR" project begins immediately afterwards, and will exhibit a new focus on lower-risk technology.

According to Takeo Hoshino, deputy director of MITI's aircraft and space development division, the ministry has approved in principle a further four years of funding at the same level, to be given to a Japanese industrial group working with international engine manufacturers. The project funding awaits a final green light from the Ministry of Finance, but this is expected imminently.

"We strongly believe that the post-HYPR project will be established, and the Ministry of Finance will make its final decision within days," says Hoshino.

The post-HYPR industrial team will be the same as that for the current programme. Japanese industry will be represented by the Society of Japanese Aerospace Companies, including Ishikawajima-Harima Heavy Industries, Kawasaki Heavy Industries and Mitsubishi Heavy Industries. Alongside these will be international partners General Electric, Pratt & Whitney, Rolls-Royce and Snecma

Whereas the HYPR programme has focused on a combined-cycle turbojet/ramjet engine - with the ramjet taking over from the turbojet for speeds between Mach 3 and Mach 5 - the post-HYPR engine will be a turbofan, optimised for flight at M2 to M3.

According to Hoshino, the international consensus is that any next generation SST will seat 250-300 people, and have a range of about 11,000km. He adds that in its SST studies, Boeing is pushing for a cruise speed of M2.4, while Aerospatiale's concept is more conservative at M2.0.

"The limitations of the national budget forced us to reconsider the strategy of the ramjet, and focus on more short-term, lower-risk technology which could be applied to a Concorde successor," says Hoshino. A combined-cycle engine would be needed for a hypersonic transport, but the technology required by such an aircraft is still not mature enough to make it economically feasible.

The post-HYPR engine could operate at present engine noise levels and an estimated one-seventh of current NOx emissions, minimising damage to the upper atmosphere.

The aim of the programme will be to develop a demonstrator engine for ground testing, expected in 2003-4. Hoshino says the engine will use of advanced, light heat-resistant, materials such as metal-matrix composites (MMCs)and ceramic-matrix composites (CMCs), but some steel and titanium will still be used in high-stress components, making the test engine substantially heavier than a flight-standard engine. Producing the latter will be the likely goal of a third phase programme which the MITI hopes will begin in fiscal year 2004-5.

Hoshino says that the demonstrator engine's rotor and stator blades will be made of advanced composites. In an operational SST, as muchas 60% of the airframe could be made of composites.

With materials playing such a crucial role in the programme, MITI has allocated ´900 million towards composites research this fiscal year, and Japanese manufacturers such as Fuji, Kawasaki and Mitsubishi are working alongside materials and chemicals firms like Toray and Mitsui Toatsu Chemicals on new applications and production techniques.

MITI is hoping that the advanced composites under development will be used in the second of two flying SST models being developed by the National Aerospace Laboratory (NAL), based at Mitaka near Tokyo.

NAL's experimental supersonic flight project envisages the testing of two 11%-scale models, the first unpowered, built of aluminium alloy and launched with the aid of a solid rocket booster; the second built using composites and fitted with twin, 8kN-thrust Teledyne drone engines.

The ´20 billion project was initiated in 1996, with preliminary design of the first prototype beginning in September 1997. The final configuration is due to be defined by the end of December, with NAL then starting the detail design phase, followed by manufacturing in time for the first, unpowered, supersonic test flight in 2001-2.

The second, powered model has just entered the conceptual design phase, although the configuration is expected to be similar to the first model (below), except for the addition of engine nacelles.

The project's goal is to fly the model at M2.0 in free air at an altitude of 65,000ft (20,000m), to measure its aerodynamic properties in supersonic flight. The results of these tests will serve as a datum for computational fluid dynamic (CFD)analysis and computational code validation. The supersonic flight experiment is intended to be equivalent to supersonic wind tunnel testing at high Reynolds numbers, - approximating operational flight - which is not available in the current NAL facilities on the ground.

The 2,000kg first model's draft experimental flight profile consists of a booster assisted launch and subsequent climb to test altitude and speed, followed by booster separation. The model then glides down into free air, in the course of which the pressure distribution, surface temperature and transition from laminar to turbulent flow over the wing are the main factors to be measured against the model's angle of attack and the Reynolds number, which varies as the model descends.

The data is recorded and downlinked by one of the on-board computers. Finally, the model, complete with its recorded data, makes a parachute and airbag assisted landing. Four flights are planned from an Australian test site at Woomera. Each flight will last 200-250s and cover about 100km.

The project aims to study the supersonic laminar airflow which is expected over most of the wing's upper surface, to develop flight guidance and control systems, and to develop advanced onboard measurement systems for data acquisition in free flight.

The final wing configuration, selected out of 99 candidate geometries, is a 4.72m-span, cranked arrow planform, integrated with a slender, 11.5m-long, fuselage designed using the area rule for wave drag reduction. The wing aerofoil sections are designed to maintain supersonic natural laminar flow over the upper surfaces and the spanwise warping of the wings is designed to reduce the lift-dependent drag.

The guidance and control systems comprise three computers and related analogue networks: the first is the air data computer (ADC),interpreting flight conditions for guidance and control by measuring dynamic and static pressure, temperature, the angle of attack, etc; the second is the inertial measurement unit (IMU), measuring pitch, acceleration, and rate of rotation; and the last is the flight control computer (FCC) responsible for commands to control surfaces necessary for launch, following the selected flight path and landing, as well as emergency procedures.

The second model will be similarly sized, and used to verify CFD codes for a high lift/drag -ratio design as well as testing the use of composite materials and the integration of the engines, believed by engineers to be one of the most challenging drag-minimisation tasks in future SST design. The NAL proposes more than 10, 10-minute flights of the powered model, beginning around 2004.

Despite these concrete efforts on Japan's part towards making the next-generation SST a reality, the country cannot hope to go it alone. Rather it hopes to use the know-how and technology it has developed while other SST advocates have dragged their feet to attain a lead role in an international partnership, be it with the USA or Europe.

A concept for a hypersonic aircraft carrying Japan Airlines livery: Japanese industry remains strongly involved in supersonic research

Making do in Europe

Julian Moxon/PARIS

A small, but determined group of researchers from France, the UK and Germany is at the heart of European research into civil supersonic transports (SSTs). Funding has virtually dried up, and the team is having to make do with $10 million a year, supplied through national industry and research budgets that are always subject to the axe. Yet, Aerospatiale's director of SST programmes, Elie Khasaki, says the work "...must go on. We have a lot of problems to resolve, and we think they can be surmounted. But we very much regret that there is no long-term supersonics programme in Europe".

For several years the work has been centred around the European Supersonics Research programme involving Aerospatiale, DaimlerChrysler Aerospace and British Aerospace, along with the three national research bodies: France's Onera, the UK's DERA and Germany's DLR. The European Commission has been minimally involved, through its small aeronautics research budget, although there is no money for supersonics in the latest 1999-2002 Fifth Framework spending plan.

The budget may be small, but the money is spent "very efficiently", says Khasaki, being directed around the various centres according to need and in a way that avoids duplication. "We work through a 'virtual office' which ensures total harmony in Toulouse, Bristol and Munich. We may be dispersed geographically, but as far as we are concerned this is a single programme with defined responsibilities".

Most of the work is on materials research, says Khasaki, with "strong emphasis" also on environmental considerations.

Source: Flight International