Lunar regolith degrades human health and equipment, making mitigation paramount for lunar missions. Cryogenic liquid sprays are a recently developed, simple and convenient concept for dust reduction in a lunar environment. However, the removal efficiency and material degradation under the extreme cryogenic vacuum environment are unknown. Traditional spacesuit dust reduction technologies used during the Apollo missions, such as brushing and vacuuming, caused abrasion of the suit fabric, which must be addressed for all dust reduction methods considered for deployment on the moon.

A new study shows that a liquid nitrogen spray developed by scientists at Washington State University can remove nearly all of the simulated lunar dust from a spacesuit, potentially posing a significant challenge for future astronauts landing on the moon. The sprinkler outperformed all previously studied methods, eliminating more than 98% of a lunar dust simulant in a vacuum environment with little damage to spacesuits.

Men have been placed on the moon, but no one has yet discovered a way to keep them clean while there. Similar to the stickiest packing peanuts, moon dust clings to anything it touches. The dust, consisting of extremely small particles with the consistency of ground fiberglass, is worse than the packing peanuts.

1/6 scale astronaut after applying fabric
Composite image of a 1/6 scale astronaut after applying fabric (left); after dust application and treatment in a vacuum (middle); after dust application, treatment in a vacuum and spot treatment with a portable liquid cryogenic spray (right).

Ian Wells, the paper’s first author and a senior in WSU’s School of Mechanical and Materials Engineering, said: “Moon dust is electrostatically charged, abrasive and permeates everything, making it a very difficult substance to deal with. You end up with a fine layer of dust that covers everything.”

Astronauts used a brush to remove dust from their spacesuits during the six crewed Apollo missions to the moon in the 1960s and early 1970s, but it wasn’t particularly effective. Electronics and motors can be damaged by abrasive particles and small dust particles. They also entered the spacesuits, broke the seals and rendered some expensive suits unusable. Researchers believe that long-term exposure to dust can lead to lung damage similar to that of Black Lung Disease. Astronauts have reportedly reported experiencing “moon hay fever”.

Wells said, “It caused a lot of problems that affected the missions and the astronauts once they got home.”

The research team demonstrated their space suit cleaning technology using the Leidenfrost effect in their work. Pouring cold water onto a hot skillet will cause water beads to form and flow around the pan, demonstrating impact. By spraying a heated, dust-covered object with very cold liquid nitrogen, the dust condenses and floats on the nitrogen vapour.

The team experimented with their cleaning technique both under normal atmospheric conditions and in a vacuum atmosphere that was more like space. In the vacuum atmosphere, the sprayer performed better.

Scientists noted, “The liquid nitrogen spray was much gentler on space suit materials than other cleaning methods. While a brush caused damage to the space suit material after just one brushing, the liquid nitrogen spray took 75 cycles to show damage.”

Magazine reference:

  1. I. Wells, J. Bussey, N. Swets, J. Leachman, et al. Moon dust removal and material degradation by liquid nitrogen sprays. Acta Astronautica. DOI: 10.1016/j.actaastro.2023.02.016