New Technologies Developed to Support Long-Term Space Operations NASA Overcomes Obstacles to Store and Transfer Cryogenic Fluids in Space . Credit: scitechdaily.com

Preparing for Long-Term Operations at the Moon and Mars

Preparing for long-term operations at the Moon and Mars brings about numerous possibilities and obstacles that NASA has yet to face. These activities require the use of new technologies and methods to ensure the agency is ready for its challenging Artemis missions and those that follow.

One of the main challenges is managing cryogenic fluids, which are liquids that exist at incredibly low temperatures, ranging from minus 238 degrees Fahrenheit to absolute zero (minus 460 F). These fluids, such as liquid hydrogen, methane, and oxygen, are essential for spacecraft propulsion and life support systems. In the future, they may also be produced on the lunar and Martian surfaces using in-situ resource utilization (ISRU).

However, deep space exploration involves storing large amounts of cryogenic fluids for extended periods of time and transferring them between spacecraft or fuel depots in orbit and on the surface. These tasks are incredibly challenging, and so far, cryogenic fluids have only been stored for a few hours in space. To address this, engineers working within NASA's Cryogenic Fluid Management (CFM) portfolio, led by Technology Demonstration Missions, are tackling these issues before future missions.

Addressing Challenges in Cryogenic Fluid Management

"This is a task that neither NASA nor our partners has ever faced before. Our future mission concepts rely on massive amounts of cryogenic fluids, and we need to figure out how to efficiently use them for long durations. This requires a series of new technologies that far exceed our current capabilities." - Lauren Ameen, deputy CFM Portfolio manager

For cryogenic fluids to be usable, they must remain in a frigid, liquid state. However, the physics of space travel, with changes in temperature and gravity, make it challenging to keep these fluids in a liquid state and accurately measure how much is in the tank.

The heat sources in space, such as the Sun and spacecraft exhaust, create a warm environment inside and around storage tanks, causing evaporation or "boiloff." This evaporation reduces the effectiveness of the fluids as rocket fuel and increases the risk of leakage or tank rupture. Furthermore, low gravity poses challenges as the fluids tend to float and slosh around, making it difficult to accurately gauge and transfer them.

Ameen explained, "Previous missions using cryogenic propellants could only be in space for a few days due to boiloff or venting losses. These spacecraft used thrust and other maneuvers to settle propellant tanks and enable fuel transfers. However, during Artemis, spacecraft will dwell in low gravity for much longer and need to transfer liquid hydrogen in space for the first time. Therefore, we need to mitigate boiloff and find innovative ways to transfer and measure cryogenic propellants."

The Cryogenic Fluid Management Portfolio

The CFM portfolio includes 24 development activities and investments aimed at reducing boiloff, improving gauging, and advancing fluid transfer techniques for in-space propulsion, landers, and ISRU. Currently, there are four near-term efforts taking place on the ground, in near-Earth orbit, and soon on the lunar surface.

In 2020, NASA awarded four contracts to American industry focused on CFM technologies - Eta Space, Lockheed Martin, SpaceX, and United Launch Alliance - to help develop and demonstrate these technologies in space. Each company will launch its respective demonstration in either 2024 or 2025, conducting multiple tests using liquid hydrogen to validate the technologies and processes.

To improve gauging, NASA has developed Radio Frequency Mass Gauges (RFMG) that use radio waves to accurately measure the amount of fluid in a spacecraft's tank during low-gravity or low-thrust conditions. This technology has been successfully tested on the ground, in sub-orbital flights, and on the International Space Station. It will also be tested on the Moon during an upcoming Commercial Lunar Payload Services flight with Intuitive Machines. After this demonstration, NASA will continue to develop and scale the technology for improved spacecraft and lander operations.

Reducing Boiloff with Cryocoolers

Another technique to reduce boiloff is using cryocoolers, which act as heat exchangers for large propellant tanks when combined with innovative insulation systems. NASA is currently working with industry partners, such as Creare, to test high-capacity cryocooler systems that pump a fluid through tubes on the tank to keep it cool. The agency plans to scale this technology for larger tank sizes to meet mission requirements before conducting future flight demonstrations.

Liquefying Gaseous Oxygen for In-Situ Resource Utilization

Moreover, NASA is developing a system to liquefy gaseous oxygen on the lunar or Martian surface, which can be used to refuel landers with propellant produced in situ. This process involves cooling oxygen to a critical temperature (at least minus 297 degrees Fahrenheit), causing it to condense from a gas to a liquid. Initial development and testing have shown that NASA can efficiently do this, and the team is currently scaling the technology for relevant tank sizes and quantities for future operations.

Advancing Space Exploration with Efficient Cryogenic Fluid Management

In the end, NASA's efforts to develop and test efficient, lightweight, and cost-effective CFM systems are crucial for the success of the agency's ambitious missions to the Moon, Mars, and beyond.

Ann Castro
Ann Castro Author
Ann Castro carries a total of 7 years experience in the healthcare domain. She owns a Master’s of Medicine Degree. She bagged numerous awards by contributing in the medical field with her ground-breaking notions. Ann has developed her own style of working and known for accuracy in her work. She loves trekking. She visits new places whenever she gets free time.