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.



Dangerous Flooding Hits US Southeast as Snow and Frigid Cold Forecast for Northeast and Plains

 In this photo provided by Donnie Smith, a kayaker navigates floodwaters Saturday, Feb. 15, 2025, in rural Knox County, Ky. (Donnie Smith via AP)
In this photo provided by Donnie Smith, a kayaker navigates floodwaters Saturday, Feb. 15, 2025, in rural Knox County, Ky. (Donnie Smith via AP)
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Dangerous Flooding Hits US Southeast as Snow and Frigid Cold Forecast for Northeast and Plains

 In this photo provided by Donnie Smith, a kayaker navigates floodwaters Saturday, Feb. 15, 2025, in rural Knox County, Ky. (Donnie Smith via AP)
In this photo provided by Donnie Smith, a kayaker navigates floodwaters Saturday, Feb. 15, 2025, in rural Knox County, Ky. (Donnie Smith via AP)

Heavy rains and dangerous flooding struck the Southeast US as much of the East endured a renewed round of harsh, soggy weather Saturday, with at least one fatality reported in Kentucky.

A man was found dead in floodwaters in Clay County, Kentucky, WKYT-TV reported. Clay County Emergency Management officials did not immediately respond to a message from The Associated Press seeking additional information.

Water submerged cars and buildings in Kentucky and mudslides blocked roads in Virginia. Both of the states were under flood warnings, along with Tennessee and Arkansas. The National Weather Service warned residents to stay off the roads.

Forecasters also predicted weekend snowstorms in the Northeast and the threat of tornadoes for the Mississippi Valley.

West Virginia Gov. Patrick Morrisey issued a state of emergency in 10 southern counties Saturday night due to heavy rains and flooding, allowing the state to use its resources to help local authorities.

Kentucky Gov. Andy Beshear preemptively declared a state of emergency in Kentucky, where flash flooding was expected into Sunday. Flash flooding hit some roads in Bowling Green and parts of western Kentucky could face up to 8 inches (20.3 centimeters) of rain.

“We want to specifically put assets in places that flood and have flooded in the past,” Beshear said on social media.

Beshear later used social media to update residents on areas in danger of flooding, including Jackson County, and said Kentucky State Police officers were performing wellness checks while shelters were opening in Pike County and Jenny Wiley State Resort Park in Prestonsburg.

Beshear said in a post late Saturday that he had written to the White House requesting an emergency disaster declaration and federal funds for impacted areas.

The Kentucky River Medical Center in the city of Jackson said closed its emergency department and was transferring all patients to two other hospitals in the region. The hospital said it would re-evaluate conditions Sunday morning to determine when it can safely reopen. The north fork of the Kentucky River was forecast to crest nearly 14 feet (4.3 meters) above flood stage that afternoon, the weather service said.

Photos posted by authorities and residents on social media showed cars and buildings underwater in south-central and eastern Kentucky. In Buchanan County, Virginia, the sheriff’s office said multiple roads were blocked by mudslides.

The Simpson County Office of Emergency Management in Kentucky said authorities performed several rescues from stalled-out vehicles in floodwaters.

“Stay home if you can,” the office said on Facebook.

Flash flooding was possible in the Mississippi, Tennessee and Ohio valleys, the weather service said. In Tennessee, flash flood warnings were issued for much of the middle of the state through the evening.

The National Weather Service called the expected rain a “major, potentially historic, flash flood event.”

Meanwhile heavy snow was expected to blanket much of New England and then transition to sleet, making travel nearly impossible. The heaviest accumulations, possibly a foot (30.5 centimeters) or more, were expected in upstate New York and portions of northern New England.

“Ice accumulations up to a quarter inch are forecast for some areas, making driving conditions dangerous. Heavy icing in some locations may result in downed trees and power outages,” the weather service warned.

Snow and arctic temperatures swept much of the Midwest and Upper Plains, covering roads in eastern Nebraska, northern Iowa and much of Wisconsin. Winter weather advisories were issued for parts of those states and Michigan, with up to 4 inches (10.6 centimeters) of snow predicted throughout Iowa, southern Wisconsin and most of Michigan by Sunday evening.

Frigid polar vortex

Meteorologists said the US was about to get its 10th and coldest polar vortex stretching event this season, with the northern Rockies and northern Plains first in line. Weather forces in the Arctic are combining to push the chilly air that usually stays near the North Pole into the US and Europe.

In Denver, where temperatures were expected to dip as low as 14 degrees (minus 10 degrees Celsius) over the weekend, the city opened shelters for those living on the streets.

Forecasters reported an inch (2.5 centimeters) of snow falling every hour just north of Denver. In Boulder County, an unoccupied vehicle that was stuck in the snow after attempting to cross railroad tracks was struck Saturday afternoon and mangled by a train. There were no injuries, but authorities warned drivers about slick roads.

The weather service also warned of extreme cold in the Upper Plains over the coming days, with wind chills ranging from minus 30 degrees (minus 34 degree Celsius) to as low as minus 60 (minus 51 degrees Celsius) in parts of western Montana, North Dakota, northern South Dakota and western Minnesota. People in those areas were urged to stay indoors and make provisions to shelter livestock and other animals.

California struggles with mudslides

Dry weather returned to Southern California after the strongest storm of the year. But the risk of rock and mudslides on wildfire-scarred hillsides continued because dangerous slides can strike even after rain stops, particularly in areas where vegetation that helps keep soil anchored has burned away.

Water, debris and boulders rushed down the mountain in the city of Sierra Madre on Thursday night, trapping at least one car in the mud and damaging several home garages with mud and debris. Bulldozers cleaned up mud-covered streets in the city of 10,000 people.

A storm in the Sierra Nevada dumped 6 feet (1.8 meters) of snow over 36 hours. Two Mammoth Mountain ski patrol workers were caught in an avalanche during avalanche mitigation work Friday morning, the resort said in a Facebook post. One was extracted and was responsive, while the other was taken to a hospital with serious injuries.