What is Helium and Why is it Used in Rockets?

India's Geosynchronous Satellite Launch Vehicle Mk III-M1 blasts off carrying Chandrayaan-2, from the Satish Dhawan Space Centre at Sriharikota, India, July 22, 2019. REUTERS/P. Ravikumar/File Photo Purchase Licensing Rights
India's Geosynchronous Satellite Launch Vehicle Mk III-M1 blasts off carrying Chandrayaan-2, from the Satish Dhawan Space Centre at Sriharikota, India, July 22, 2019. REUTERS/P. Ravikumar/File Photo Purchase Licensing Rights
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What is Helium and Why is it Used in Rockets?

India's Geosynchronous Satellite Launch Vehicle Mk III-M1 blasts off carrying Chandrayaan-2, from the Satish Dhawan Space Centre at Sriharikota, India, July 22, 2019. REUTERS/P. Ravikumar/File Photo Purchase Licensing Rights
India's Geosynchronous Satellite Launch Vehicle Mk III-M1 blasts off carrying Chandrayaan-2, from the Satish Dhawan Space Centre at Sriharikota, India, July 22, 2019. REUTERS/P. Ravikumar/File Photo Purchase Licensing Rights

Two NASA astronauts aboard Boeing's (BA.N) Starliner will stay on the International Space Station for months, because of a faulty propulsion system whose problems included helium leaks. Back on Earth, SpaceX's Polaris Dawn mission has been delayed because of helium issues on ground equipment.

Boeing's Starliner spacecraft landed uncrewed in a New Mexico desert late on Friday.

Past missions have that have been affected by pesky helium leaks include ISRO's Chandrayaan 2 and ESA's Ariane 5. Why do spacecraft and rockets use helium, and what is so tricky about it?

WHY HELIUM?

Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen.

Rockets need to achieve specific speeds and altitude to reach and maintain orbit. A heavier rocket requires more energy, not only increasing fuel consumption but also needing more powerful engines, which are more expensive to develop, test, and maintain.

Helium also has a very low boiling point (-268.9°C or -452°F), allowing it to remain a gas even in super-cold environments, an important feature because many rocket fuels are stored in that temperature range.

The gas is non-toxic, but cannot be breathed on its own, because it displaces the oxygen humans need for respiration.

HOW IS IT USED?

Helium is used to pressurize fuel tanks, ensuring fuel flows to the rocket's engines without interruption; and for cooling systems.

As fuel and oxidiser are burned in the rocket's engines, helium fills the resulting empty space in the tanks, maintaining the overall pressure inside.

Because it is non-reactive, it can safely mingle with the tanks' residual contents.

IS IT PRONE TO LEAKS?

Helium’s small atomic size and low molecular weight mean its atoms can escape through small gaps or seals in storage tanks and fuel systems.

But because there is very little helium in the Earth's atmosphere, leaks can be easily detected - making the gas important for spotting potential faults in a rocket or spacecraft's fuel systems.

In May, hours before Boeing's Starliner spacecraft made an initial attempt to launch its first astronaut crew, tiny sensors inside the spacecraft detected a small helium leak on one of Starliner's thrusters that NASA spent several days analysing before deeming it low-risk, according to Reuters.

Additional leaks were detected in space after Starliner launched in June, contributing to NASA's decision to bring Starliner back to Earth without its crew.

The frequency of helium leaks across space-related systems, some engineers say, have highlighted an industry-wide need for innovation in valve design and more precise valve-tightening mechanisms.

ARE THERE ALTERNATIVES?

Some rocket launches have experimented with gases such as argon and nitrogen, which are also inert and can sometimes be cheaper. Helium, however, is much more prevalent in the industry.

Europe's new Ariane 6 rocket ditched the helium of its predecessor Ariane 5 for a novel pressurization system that converts a small portion of its primary liquid oxygen and hydrogen propellants to gas, which then pressurizes those fluids for the rocket engine.

That system failed in space during the final phase of Ariane 6's otherwise successful debut launch in July, adding to the global rocket industry's long list of pressurization challenges.



Mercedes 1955 ‘Streamliner’ Set to Smash F1 Record at Auction

Mechanics push a W196 old timer racing car at a Mercedes Benz vintage car show marking the German car maker's 125 anniversary at the former Tempelhof airport in Berlin, August 27, 2011. (Reuters)
Mechanics push a W196 old timer racing car at a Mercedes Benz vintage car show marking the German car maker's 125 anniversary at the former Tempelhof airport in Berlin, August 27, 2011. (Reuters)
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Mercedes 1955 ‘Streamliner’ Set to Smash F1 Record at Auction

Mechanics push a W196 old timer racing car at a Mercedes Benz vintage car show marking the German car maker's 125 anniversary at the former Tempelhof airport in Berlin, August 27, 2011. (Reuters)
Mechanics push a W196 old timer racing car at a Mercedes Benz vintage car show marking the German car maker's 125 anniversary at the former Tempelhof airport in Berlin, August 27, 2011. (Reuters)

A sleek, long-nosed Mercedes raced by Stirling Moss and five-times Formula One world champion Juan Manuel Fangio in 1955 could become the most expensive grand prix car of all time at an auction in Stuttgart on Saturday.

The W196 R Stromlinienwagen ("Streamline car"), one of only four complete examples in existence, is being sold by RM Sotheby's on behalf of the Indianapolis Motor Speedway (IMS) at a target price of more than 50 million euros ($52 million).

If it meets the estimate, it would also be the second costliest car ever sold at auction after a 1955 Mercedes 300SLR Uhlenhaut Coupe sportscar that changed hands for 135 million euros in May 2022.

The most expensive grand prix car sold at auction to date was another ex-Fangio 1954 Mercedes W196 that fetched $29.6 million at Goodwood in 2013.

The IMS car is the first streamline-bodied W196 R to become available for private ownership and, in its open-wheel form, was driven to victory by Fangio at the non-championship Buenos Aires Grand Prix in 1955.

Moss raced it with the streamline body at the Italian Grand Prix at Monza, retiring after setting the fastest lap at an average speed of 215.7 kph.

Mercedes withdrew from factory-sponsored motorsport in 1955 after a Le Mans 24 Hours disaster that killed 84 people, returning to Formula One as an engine maker in 1994.

The car is presented in its Monza livery with full documentation.

"Without any doubt, it's the most beautiful race car in the world and ever. Nothing can compare. It's simply a masterpiece of style and design," Marcus Breitschwerdt, head of Mercedes-Benz heritage, told Reuters Television.

"It is very fast. The top speed is actually above and beyond 300 kph.

"I wouldn't expect that it's too much of an effort to get it back to driving condition. And we gladly will offer whoever buys the car to do it for them."

The car, chassis number 00009/54, was donated to the IMS by Mercedes in 1965 and is being sold to raise funds for the museum's restoration efforts.

The Indianapolis museum, which is aiming to become more US-focused, is selling a total of 11 cars from its collection at three separate auctions this year.

The Mercedes "Silver Arrows" dominated the immediate pre- and post World War Two era of grand prix racing with the W196 R a world-beater in 1954 and 1955.

The streamlined bodywork with enclosed wheels was used at high-speed circuits, with the open-wheeled version favored for more twisty tracks.