Researchers have adjusted the traditional catapult launch method used on aircraft carriers to enable safe and easy orbital launches of aircraft at supersonic speeds.
Wang Yunpeng, an associate professor at the Institute of Mechanics under the Chinese Academy of Sciences in Beijing, and his colleagues utilized a small-scale version of an orbital aircraft, similar to a space shuttle, along with a supersonic launch vehicle to test the method at speeds seven times the speed of sound. In a paper published on December 8 in the journal Astronautica Sinica, the research team reported that the results demonstrate that the catapult technology, which is considered outdated on modern aircraft carriers, can be adapted to launch vehicles into orbit from near-space altitudes.
A high-speed camera captures the separation process of the small-scale aircraft and the launch vehicle in the wind tunnel. (Photo: SCMP).
The research also addressed a long-standing issue that has perplexed supersonic researchers for decades: how to overcome unpredictable strong turbulence at extremely high speeds and achieve a smooth separation process between the launch vehicle and the space aircraft. Until now, researchers had not found an effective way to eliminate the risks of vehicles separating at an angle or even colliding.
The research team launched the aircraft at 1/80 of its actual size from a one-meter-long model launch vehicle, using a piston to simulate rocket engine ignition while the JF-12 wind tunnel operated at Mach 7 (8,643 km/h). In an instant, the aircraft shot up from the top of the launch vehicle. As the speed in the tunnel decreased, the aircraft fell to the ground and broke into several pieces. According to Wang’s team, this rapid experiment “verified the feasibility and effectiveness of the active separation method.”
The JF-12, one of the strongest wind tunnels in the world, simulates extremely hot airflow at supersonic speeds with shock waves generated by chemical explosions. Although mimicking the extreme conditions of supersonic flight, these conditions can only be sustained for one second. This duration is sufficient to confirm that compared to other standard separation processes, the catapult design eliminates the distance between the two aircraft and minimizes the risk of collision.
In traditional aircraft carriers, the catapult method acts as a short runway for aircraft, providing enough lift for the vehicle to leave the deck while the ship moves against the wind at a maximum speed of about 60 km/h. In the supersonic version, researchers reduced the slope of the runway to create a perfectly flat surface, which helps decrease the drag that could occur when two vehicles separate at extremely high speeds in the atmosphere.
In the wind tunnel experiment, the research team observed that the nose of the aircraft tilted slightly upward as it approached the end of the flat runway, due to the thrust from the shock waves formed over the top of the aircraft. However, as the aircraft was about to separate from the launch vehicle, another shock wave formed near the tail, causing it to dive downward. The two opposing forces canceled each other out, resulting in a perfectly smooth separation process.
Wang and his colleagues attached a powerful gas-operated piston to the rear of the test aircraft to facilitate takeoff during the brief duration of the experiment. They also developed an automated system to coordinate everything from the mechanical equipment in the experiment to high-speed cameras that recorded the separation process in detail.
Wang stated that a full-sized spacecraft weighing 87 tons, equivalent to a space shuttle, would take off in approximately eight seconds, powered by rocket engines with a maximum thrust of 1,500 kilonewtons. The catapult process would use less than one-tenth of the thrust of the main engine. The results from the wind tunnel need to be combined with other long-term experiments before the technology is ready for practical application.
China is planning to develop a fleet of supersonic passenger aircraft capable of reaching any location on Earth within 1 to 2 hours. The country is developing a supersonic launch vehicle equipped with air-breathing jet engines that can fly at near-space altitudes at Mach 5 (6,174 km/h). Some scientists are confident that this technology will revolutionize transportation. The aircraft could take off and land at existing airports, at a cost only a fraction of that of rockets. The vehicle could also serve as a launch pad for spacecraft.
