Stephen Chenin Beijing

Published: 12:00pm, 23 Feb 2025

In an ironic twist of cosmic problem-solving, Chinese researchers have transformed a lingering Nasa headache – the stranded Boeing Starliner astronauts – into a revolutionary propulsion breakthrough that could redefine modern warfare and space travel.

The two Nasa astronauts have been marooned at the International Space Station since June last year after multiple helium leaks incapacitated the thruster systems of their spacecraft – Boeing’s troubled Starliner capsule.

As a result, helium, the ultralight gas used to pressurise liquid rocket fuel, has become an emblem of engineering frailty.

Now, Chinese scientists report they have harnessed that very flaw to achieve what Pentagon planners have long sought: a solid-fuel rocket capable of tripling its thrust on demand while chilling its exhaust to near-ambient temperatures, rendering it almost invisible to infrared sensors.

In a study published in Acta Aeronautica et Astronautica Sinica this month, the team led by aerospace researcher Yang Zenan, from Harbin Engineering University, detailed how injecting helium into traditional solid rocket motors via micron-scale pores triggers a thrust surge.

Helium does not burn, but optimal ratios of helium to combustion gas (1:4) boosted the specific impulse by 5.77 per cent, enabling thrust levels to soar 300 per cent through adjustable injection, Yang and his colleagues wrote.

The cold helium gas also helps take thermal stealth to a whole new level. Exhaust plumes cooled by 1,327 degrees Celsius (2,420 Fahrenheit) can technically evade detection by almost any infrared missile-warning satellites, computer simulation suggests.

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And the flight would remain smooth. Helium’s inert nature avoids combustion instability, unlike volatile alternatives such as hydrogen.

The technology could also be used on fast-response solid-fuel rockets to launch satellites at a lower cost, a capability urgently needed by the military, according to the researchers.

The physics behind this idea is that at 4g/mol, helium’s ultralight gas expands and accelerates exhaust velocity when micro-injected – 2mm pores are optimal – at a much higher rate than conventional combustion by-products – 29g/mol.

Room-temperature helium, when absorbing excess heat from combustion gases, not only slashes infrared signatures but also helps protect nozzle materials, according to Yang’s team.

Their work has found that real-time helium flow adjustments allow a single motor to scale thrust from 100 per cent to 313 per cent, a potential game-changer for high-speed missile manoeuvrability.

The researchers linked the technology to “resolving high-speed, long-range, infrared stealth challenges” – a direct nod to US hypersonic missile defences.

The cooled plumes could evade SpaceX Starshield’s heat-seeking satellites and SM-3 Block IIA interceptors, while thrust modulation enables erratic terminal trajectories.

Nasa said earlier this month that SpaceX would bring Butch Wilmore and Suni Williams, the two stranded astronauts, home in mid-March.

“Human space flight is full of unexpected challenges,” Nasa’s commercial crew programme manager Steve Stich said in a statement.

Stephen Chen

Stephen Chen is the SCMP's science news editor. He investigates major research projects in China, a new power house of scientific and technological innovation,