SCIENCE-JAPAN: Ambition Soars with Supersonic Plane Project

By IPS Correspondents Reprint | | Print |

Edwin Karmiol

TOKYO, Aug 6 2001 (IPS) - It will fly 10 percent faster than the Concorde, have a far greater flying range, consume less fuel and produce engine noise levels akin to just that of a jumbo jet.

These are the features of a next-generation supersonic travel (SST) aircraft that Japan’s National Aerospace Laboratory (NAL) is developing, and hopes will be doing commercial flights in 2020.

The 28 billion yen (224 million U.S. dollar) project, known as the National Experimental Supersonic Transport (NEXST-1), includes plans to test a reduced scale model of the plane in Australia in March 2002.

“The SST is a necessity and it is a natural way to go,” Naohito Tsuda, a structural engineer with the Society of Japan Aerospace Companies (SJAC), said of the ambitious project, with which Japan hopes to build on its development of other aircraft in past decades.

In the sixties, Japan’s aviation industry constructed the YS- 11, a 50-passenger plane. This was followed in the 1970s by Mitsubishi’s MU 2 turboprop executive plane and by the MU 300 in the 1980s.

Japanese scientists also believe that a new supersonic plane, research on which began in 1997 and saw additional technological developments recently, would meet future needs for bigger aircraft to accommodate the growing number of passengers.

Business travelers are constantly looking for faster travel times, they add.

The utilisation rate of a supersonic plane would be also of use to airlines, they say.

Still others say the supersonic plane project is attractive as a scientific challenge in the history of flight.

“With the introduction of the SST, the speed will be increased 2.5 times and save 50 percent of travel time,” Tsuda said, adding that this would certainly be welcomed by tourists.

Designed to cruise at a speed of Mach 2.2 (about 2,400 km/h), the Japanese version of the SST would have a flying range of 11,000 km, or nearly twice that of the Anglo-French supersonic fleet.

The plane is being designed accommodate 300 passengers, or triple that of the Concorde’s seating capacity of 100.

But the most challenging achievement will consist of ensuring that the supersonic plane is environmentally friendly — taking into consideration its noise levels and pollution.

There is the issue of notable reduction by the Japanese SST plane of nitrogen oxide (NOx) emissions, produced by jet engines’ burning of fuel in flight, which will be 75 percent lower than the Concorde.

Hidehiko Nakayasu, head of the research team on the plane project, said that to minimise the aircraft’s lift/drag ratio, its airframe’s aerodynamics would be enhanced.

This calls for smaller engines, whose turbines would not only have to be more compact but also more powerful. The use of composite materials would lighten the plane’s weight and lead to better fuel efficiency.

To reduce the increased noise level caused by the high speed of the jet and the rise of the engine’s exhaust speed, NAL is also conducting research on noise reduction devices. These consist of a mixer-ejector nozzle and acoustic liners.

Combustion technology, now in its research stage, would contribute to the abatement of polluting gas exhausts. To obtain very low nitrogen oxide emissions, NAL is developing a burner that combines a short-flame for complete combustion and quick NOx quenching.

Tests with a model of a ceramic-made combustor showed that very low nitrogen oxide emissions can be realised even with combustor inlet air temperatures as high as 900 degrees Celsius.

Although the pollution and noise emissions of the Japanese SST would be greatly reduced, there is a limit to their control.

“The SST has a big problem, namely the sonic boom,” Yoshio Yibaragi, also from JADC, said in an interview. “It’s a problem that could not yet be solved. It is very difficult.”

But Tsuda says that while the supersonic boom cannot be solved, “most of the routes are over the oceans, so part of the troubles can be avoided”.

Looking ahead, Japan Air Lines (JAL) officials say the airline would consider using the SST plane if it meets environmental standards and become economically viable to operate.

Asked if JAL would use such an aircraft if it is successful, Sataka replied: “Yes we would, if the economics of the plane would be similar to subsonic planes and if the aircraft conformed to environmental standards.”

This early, scientists are looking forward to the flight test of a two-tonne, engineless Japanese experimental SST that will be conducted in the Australian desert of Woomera in March next year.

The prototype airplane, one-tenth the size of the intended aircraft, will have a wingspan of 4.72 metres, measure 11.5 metres long and 1.25 metres high.

It will be launched and propelled by a 10 meter-long solid rocket to an altitude of 20 km before separating. The SST will then glide back down to earth at a speed of Mach 2 in two phases to allow scientists to gather data at altitudes of 15 and 12 km.

More than 800 sensors, installed on the surface of the airframe, will help analyse the flight performance of the NEXST-1 during the approximately 12-minute flight.

More recently, scientists were able to optimise wing shape with the help of the CFS (Computational Fluid Dynamics) super computer. This technique enables the entire testing procedure to be simulated before going ahead with the practical trials.

The targeting performances for the SST’s airframe, for instance, were entered into the programme. This led researchers to adopt an arrow head-shaped wing and a curved body to reduce the plane’s drag.

Tests will last one year and then be followed by others between 2004 and 2006 with NEXST-2, involving an aircraft powered by jet engines.