[ti:Why Is Helium Causing Problems with Spacecraft?]
[al:Science & Technology]
[ar:VOA]
[dt:2024-09-13]
[by:www.voase.cn]
[00:00.00]Helium leaks have been a major problem for spacecraft and rockets.
[00:06.28]Recent reports about Boeing's Starliner and SpaceX's Polaris Dawn mission have involved problems controlling helium.
[00:18.02]Recently, the Starliner had a helium leak in a propulsion system.
[00:23.49]Polaris Dawn also had helium issues on its ground equipment.
[00:29.72]Helium leaks have affected past missions including the Indian Space Research Organization's Chandrayaan 2 and the European Space Agency's Ariane 5.
[00:43.72]Recently, Reuters news agency explored why spacecraft and rockets use helium, and why it can cause problems:
[00:53.64]Helium is inert, meaning it does not chemically react with other substances. 
[01:01.27]It also does not burn. Helium's atomic number is 2, making it the second lightest element after hydrogen.
[01:11.09]Rockets need to reach exact speeds and altitudes to maintain their orbits. 
[01:17.95]Heavier rockets need more energy to fly and use more fuel. 
[01:24.65]They also require more powerful engines, which are costlier to develop, test, and maintain.
[01:32.80]Helium has an extremely low boiling point of -268.9 degrees Celsius.
[01:43.44]This means that it remains a gas even in extremely cold environments like space. 
[01:50.99]That is an important quality because many rocket fuels are stored at low temperatures.
[01:59.01]Helium is not toxic. 
[02:01.50]But it cannot be breathed on its own because it displaces oxygen. 
[02:08.29]Humans need oxygen to live.
[02:11.42]Because of its special qualities, helium is used to pressurize fuel tanks.
[02:18.84]It helps ensure fuel flows to the rocket's engines without stopping. 
[02:24.27]Helium is also used for cooling systems.
[02:28.45]As fuel and oxidizer are burned in the rocket's engines, helium fills the resulting empty space in the tanks, maintaining the correct pressure inside.
[02:42.47]Because it is non-reactive, it can safely mix with other contents in the tanks.
[02:49.60]Helium's small atomic size and low molecular weight mean its atoms can escape through small spaces or seals in storage tanks and fuel systems.
[03:03.33]However, because there is very little helium in the Earth's atmosphere, leaks can be easily detected.
[03:12.32]This makes the gas important for identifying possible problems in a rocket or spacecraft's fuel systems.
[03:21.97]In May, hours before Boeing's Starliner spacecraft made its first attempt to launch an astronaut crew, sensors inside the spacecraft detected a small helium leak.
[03:37.19]The American space agency NASA spent several days studying the leak before deciding it was low risk.
[03:45.66]Additional leaks were detected in space after Starliner launched in June.
[03:52.95]Such discoveries played a part in NASA's decision to bring Starliner back to Earth without its crew.
[04:01.99]As a result, two NASA astronauts who flew to the International Space Station aboard a Starliner capsule will need to return to Earth on a SpaceX vehicle early next year.
[04:16.82]The frequency of helium leaks across space-related systems, some engineers say, has shown an industry-wide need for innovation.
[04:30.08]Innovation is needed in the design of valves and the mechanisms that tighten them. 
[04:37.65]A valve is a mechanical device that controls the flow of a gas or fluid.
[04:44.43]Some rocket scientists have experimented with gases such as argon and nitrogen, which are also inert and can sometimes be less costly. 
[04:57.77]Helium, however, is much more common in the space industry.
[05:03.52]In Europe's new Ariane 6 rocket, designers replaced the helium that was used in the rocket's predecessor Ariane 5.
[05:14.86]The Ariane 6 has a new pressurization system. 
[05:19.47]The new system changes a small amount of liquid oxygen and hydrogen propellants to gas, which then pressurizes those fluids for the rocket engine.
[05:32.21]That system failed in space, however, during the final part of Ariane 6's otherwise successful launch in July. 
[05:42.43]The failure of the new system added to the international rocket industry's list of pressurization difficulties.
[05:52.37]I'm John Russell.