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China conducts ground test of hypersonic ramjet that can change shape in flight

The graphite seal used in the Chinese breakthrough is the same one the US defence industry desperately needs

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A Northwestern Polytechnical University hypersonic vehicle lifts off in northwestern China last year. The university’s researchers have reported a new breakthrough in graphite-sealed engine technology with implications for the US-China hypersonic race. Photo: Handout
Stephen Chenin Beijing
At a test facility in China, a hypersonic engine that reshapes its internal airflow channel – much like a throat tightening and relaxing – has operated continuously from a relatively modest Mach 1.8 (nearly twice the speed of sound) all the way to Mach 6 without failing.

And the material that kept superheated gases from escaping? Essentially the same black mineral found inside a pencil: graphite.

For years, engines of this type could not ignite until the aircraft had already reached Mach 4 – meaning a separate rocket booster was needed to get up to speed first, adding cost and complexity.

Now, researchers from Northwestern Polytechnical University and the Beijing Power Machinery Institute say they have solved a problem that has stumped engineers for decades.

They ran the variable-geometry ramjet – a type of air-breathing jet engine with no moving compressor – at a ground-based facility that simulates high-speed flight conditions.

The engine’s combustion chamber throat – a moving metal component that tightens and relaxes to manage airflow at different speeds – adjusted itself in one third of a second while inhaling gases at 1,650 degrees Celsius, according to a paper published in the Journal of Propulsion Technology on May 28.

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