NASA astronauts have literally been playing with fire aboard the International Space Station, as part of experiments to determine how flames behave in space.
The ‘Confined Combustion’ experiments have been conducted since Christmas Eve to determine the how fires spread and behave differently in zero gravity.
Due to the differences in gravity, fires could be more dangerous on the moon than on Earth, with more robust fires that spread quicker.
The experiments could provide important insights for NASA’s upcoming trip to the moon in 2024, and the long-term missions to establish a lunar outpost there.
A high-res, still camera image of an experimental fire in low gravity conditions
‘Living on the moon is a different environment from space station and Earth, and fires will behave differently there,’ said Dr Paul Ferkul, of the Universities Space Research Association, who is working on the project.
‘There’s reason to believe that fires could be more dangerous on the moon than on Earth,’ Dr Ferkul told the Guardian.
When a flame burns on Earth, gravity draws colder, denser air down to the base of the flame, replacing the hot air, which rises – an effect called buoyancy.
This upward flow of air gives a flame its distinctive teardrop shape.
But in zero gravity, hot air doesn’t move upwards due to the lack of gravity, giving fires a spherical or dome shape.
On Earth, a candle burns with a tall, yellow flame (right). In space, a smaller, blue flame burns on the center of the wick
According to NASA, buoyancy actually prevents scientists on Earth from gaining a fundamental understanding of how flames spread.
However, in microgravity, this buoyancy is eliminated, allowing scientists to better study the physics of flame spread.
‘Removing gravity eliminates natural convection; the hot air isn’t going up because there is no “up”,’ said Ferkul.
NASA astronauts lit fires in boxes of different sizes, with a fan blowing air through them to provide oxygen – which fires need to burn.
The crew used cotton, fibreglass and acrylic samples as fuel to see how different air flows and box sizes alter the combustion rates.
In the 15 experiments conducted so far the flame has burned for between one and 22 minutes.
The experiments examined the behaviour of flames as they spread in differently-shaped confined spaces in microgravity – in particular studying the interaction between spreading flames and surrounding walls.
Flame spread in confined spaces such as buildings and vehicles may pose a more serious fire hazard than flame spread in open spaces, caused partly by radiative heat feedback from the surrounding walls.
Flames spread faster in smaller confined spaces than in larger spaces, even if all other environmental conditions such as oxygen supply and pressure were the same.
The tests suggest flames could be more dangerous on the moon than on Earth, due to the lower buoyancy – because heat stays closer to the ground.
NASA can use this knowledge to improve material selection for its lunar outpost on the moon, which it plans to establish by 2028, as well as fire safety strategies.
As part of the space agency’s Artemis program, NASA plans to send the first woman to the moon in 2024 and establish ‘sustainable missions’ by 2028.
NASA envisages the moon as an industrial base for further space exploration, as well as a home for refuelling depots and a facility for processing samples from the Moon’s surface.
The Confined Combustion experiments aren’t the first to light fires aboard the ISS; in 2008, NASA launched the Combustion Integrated Rack to understand the fundamentals of the combustion process.
The ‘Saffire’ experiments conducted from 2016 to 2017 investigated large-scale flame spread and material flammability limits, including a fire intentionally lit aboard the Cygnus spacecraft before it burnt up in Earth’s atmosphere.
WHAT IS NASA’S ARTEMIS MISSION TO THE MOON?
Artemis was the twin sister of Apollo and goddess of the Moon in Greek mythology.
NASA has chosen her to personify its path back to the Moon, which will see astronauts return to the lunar surface by 2024 – including the first woman and the next man.
Artemis 1, formerly Exploration Mission-1, is the first in a series of increasingly complex missions that will enable human exploration to the Moon and Mars.
Artemis 1 will be the first integrated flight test of NASA’s deep space exploration system: the Orion spacecraft, Space Launch System (SLS) rocket and the ground systems at Kennedy Space Center in Cape Canaveral, Florida.
Artemis 1 will be an uncrewed flight that will provide a foundation for human deep space exploration, and demonstrate our commitment and capability to extend human existence to the Moon and beyond.
During this flight, the spacecraft will launch on the most powerful rocket in the world and fly farther than any spacecraft built for humans has ever flown.
It will travel 280,000 miles (450,600 km) from Earth, thousands of miles beyond the Moon over the course of about a three-week mission.
Artemis 1, formerly Exploration Mission-1, is the first in a series of increasingly complex missions that will enable human exploration to the Moon and Mars. This graphic explains the various stages of the mission
Orion will stay in space longer than any ship for astronauts has done without docking to a space station and return home faster and hotter than ever before.
With this first exploration mission, NASA is leading the next steps of human exploration into deep space where astronauts will build and begin testing the systems near the Moon needed for lunar surface missions and exploration to other destinations farther from Earth, including Mars.
The will take crew on a different trajectory and test Orion’s critical systems with humans aboard.
The SLS rocket will from an initial configuration capable of sending more than 26 metric tons to the Moon, to a final configuration that can send at least 45 metric tons.
Together, Orion, SLS and the ground systems at Kennedy will be able to meet the most challenging crew and cargo mission needs in deep space.
Eventually NASA seeks to establish a sustainable human presence on the Moon by 2028 as a result of the Artemis mission.
The space agency hopes this colony will uncover new scientific discoveries, demonstrate new technological advancements and lay the foundation for private companies to build a lunar economy.