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By NASA
Flight Engineer Joe Acaba works in the U.S. Destiny laboratory module on the International Space Station, setting up hardware for the Zero Boil-Off Tank (ZBOT) experiment. Joe Acaba Space missions rely on cryogenic fluids — extremely cold liquids like liquid hydrogen and oxygen — for both propulsion and life support systems. These fuels must be kept at ultra-low cryogenic temperatures to remain in liquid form; however, solar heating and other sources of heat increase the rate of evaporation of the liquid and cause the pressure in the storage tank to increase. Current storage methods require venting the cryogenic propellant to space to control the pressure in fuel tanks.
NASA’s Zero Boil-Off Tank Noncondensables (ZBOT-NC) experiment is the continuation of Zero Boil-Off studies gathering crucial data to optimize fuel storage systems for space missions. The experiment will launch aboard Northrop Grumman’s 23rd resupply mission to the International Space Station.
When Cold Fuel Gets Too Warm
Even with multilayer insulation, heat unavoidably seeps into cryogenic fuel tanks from surrounding structures and the space environment, causing an increase in the liquid temperature and an associated increase in the evaporation rate. In turn, the pressure inside the tank increases. This process is called “boil-off” and the increase in tank pressure is referred to as “self-pressurization.”
Venting excess gas to the environment or space when this process occurs is highly undesirable and becomes mission-critical on extended journeys. If crew members used current fuel storage methods for a years-long Mars expedition, all propellant might be lost to boil-off before the trip ends.
NASA’s ZBOT experiments are investigating active pressure control methods to eliminate wasteful fuel venting. Specifically, active control through the use of jet mixing and other techniques are being evaluated and tested in the ZBOT series of experiments.
The Pressure Control Problem
ZBOT-NC further studies how noncondensable gases (NCGs) affect fuel tank behavior when present in spacecraft systems. NCGs don’t turn into liquid under the tank’s operating conditions and can affect tank pressure.
The investigation, which is led out of Glenn Research Center, will operate inside the Microgravity Science Glovebox aboard the space station to gather data on how NCGs affect volatile liquid behavior in microgravity. It’s part of an effort to advance cryogenic fluid management technologies and help NASA better understand low-gravity fluid behavior.
Researchers will measure pressure and temperature as they study how these gases change evaporation and condensation rates. Previous studies indicate the gases create barriers that could reduce a tank’s ability to maintain proper pressure control — a potentially serious issue for extended space missions.
How this benefits space exploration
The research directly supports Mars missions and other long-duration space travel by helping engineers design more efficient fuel storage systems and future space depots. The findings may also benefit scientific instruments on space telescopes and probes that rely on cryogenic fluids to maintain the extremely low temperatures needed for operation.
How this benefits humanity
The investigation could improve tank design models for medical, industrial, and energy production applications that depend on long-term cryogenic storage on Earth.
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Zero Boil-Off Tank Noncondensables (ZBOT-NC)
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Biological & Physical Sciences Division
NASA’s Biological and Physical Sciences Division pioneers scientific discovery and enables exploration by using space environments to conduct investigations not possible on Earth. Studying biological and physical phenomenon under extreme conditions allows researchers to advance the fundamental scientific knowledge required to go farther and stay longer in space, while also benefitting life on Earth.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Dwarf planet Ceres is shown in these enhanced-color renderings that use images from NASA’s Dawn mission. New thermal and chemicals models that rely on the mission’s data indicate Ceres may have long ago had conditions suitable for life.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA The dwarf planet is cold now, but new research paints a picture of Ceres hosting a deep, long-lived energy source that may have maintained habitable conditions in the past.
New NASA research has found that Ceres may have had a lasting source of chemical energy: the right types of molecules needed to fuel some microbial metabolisms. Although there is no evidence that microorganisms ever existed on Ceres, the finding supports theories that this intriguing dwarf planet, which is the largest body in the main asteroid belt between Mars and Jupiter, may have once had conditions suitable to support single-celled lifeforms.
Science data from NASA’s Dawn mission, which ended in 2018, previously showed that the bright, reflective regions on Ceres’ surface are mostly made of salts left over from liquid that percolated up from underground. Later analysis in 2020 found that the source of this liquid was an enormous reservoir of brine, or salty water, below the surface. In other research, the Dawn mission also revealed evidence that Ceres has organic material in the form of carbon molecules — essential, though not sufficient on its own, to support microbial cells.
The presence of water and carbon molecules are two critical pieces of the habitability puzzle on Ceres. The new findings offer the third: a long-lasting source of chemical energy in Ceres’ ancient past that could have made it possible for microorganisms to survive. This result does not mean that Ceres had life, but rather, that there likely was “food” available should life have ever arisen on Ceres.
This illustration depicts the interior of dwarf planet Ceres, including the transfer of water and gases from the rocky core to a reservoir of salty water. Carbon dioxide and methane are among the molecules carrying chemical energy beneath Ceres’ surface.NASA/JPL-Caltech In the study, published in Science Advances on Aug. 20, the authors built thermal and chemical models mimicking the temperature and composition of Ceres’ interior over time. They found that 2.5 billion years or so ago, Ceres’ subsurface ocean may have had a steady supply of hot water containing dissolved gases traveling up from metamorphosed rocks in the rocky core. The heat came from the decay of radioactive elements within the dwarf planet’s rocky interior that occurred when Ceres was young — an internal process thought to be common in our solar system.
“On Earth, when hot water from deep underground mixes with the ocean, the result is often a buffet for microbes — a feast of chemical energy. So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past,” said Sam Courville, lead author of the study. Now based at Arizona State University in Tempe, he led the research while working as an intern at NASA’s Jet Propulsion Laboratory in Southern California, which also managed the Dawn mission.
Catching Chill
The Ceres we know today is unlikely to be habitable. It is cooler, with more ice and less water than in the past. There is currently insufficient heat from radioactive decay within Ceres to keep the water from freezing, and what liquid remains has become a concentrated brine.
The period when Ceres would most likely have been habitable was between a half-billion and 2 billion years after it formed (or about 2.5 billion to 4 billion years ago), when its rocky core reached its peak temperature. That’s when warm fluids would have been introduced into Ceres’ underground water.
The dwarf planet also doesn’t have the benefit of present-day internal heating generated by the push and pull of orbiting a large planet, like Saturn’s moon Enceladus and Jupiter’s moon Europa do. So Ceres’ greatest potential for habitability-fueling energy was in the past.
This result has implications for water-rich objects throughout the outer solar system, too. Many of the other icy moons and dwarf planets that are of similar size to Ceres (about 585 miles, or 940 kilometers, in diameter) and don’t have significant internal heating from the gravitational pull of planets could have also had a period of habitability in their past.
More About Dawn
A division of Caltech in Pasadena, JPL managed Dawn’s mission for NASA’s Science Mission Directorate in Washington. Dawn was a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. JPL was responsible for overall Dawn mission science. Northrop Grumman in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute were international partners on the mission team.
For a complete list of mission participants, visit:
https://solarsystem.nasa.gov/missions/dawn/overview/
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Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
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NASA Headquarters, Washington
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Last Updated Aug 20, 2025 Related Terms
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By NASA
NASA Glenn Research Center’s Thermal Energy Conversion Branch team and the University of Leicester’s Space Nuclear Power team pose for a photo at the center in Cleveland following a successful test in January 2025.Credit: NASA/Jef Janis To explore the unknown in deep space, millions of miles away from Earth, it’s crucial for spacecraft to have ample power. NASA’s radioisotope power systems (RPS) are a viable option for these missions and have been used for over 60 years, including for the agency’s Voyager spacecraft and Perseverance Mars rover. These nuclear batteries provide long-term electrical power for spacecraft and science instruments using heat produced by the natural radioactive decay of radioisotopes. Now, NASA is testing a new type of RPS heat source fuel that could become an additional option for future long-duration journeys to extreme environments.
Historically, the radioisotope plutonium-238 (plutonium oxide) has been NASA’s RPS heat source fuel of choice, but americium-241 has been a source of interest for the past two decades in Europe. In January, the Thermal Energy Conversion Branch at NASA’s Glenn Research Center in Cleveland and the University of Leicester, based in the United Kingdom, partnered through an agreement to put this new option to the test.
One method to generate electricity from radioisotope heat sources is the free-piston Stirling convertor. This is a heat engine that converts thermal energy into electrical energy. However, instead of a crankshaft to extract power, pistons float freely within the engine. It could operate for decades continuously without wear, as it does not have piston rings or rotating bearings that will eventually wear out. Thus, a Stirling convertor could generate more energy, allowing more time for exploration in deep space. Researchers from the University of Leicester — who have been leaders in the development of americium RPS and heater units for more than 15 years — and NASA worked to test the capabilities of a Stirling generator testbed powered by two electrically heated americium-241 heat source simulators.
“The concept started as just a design, and we took it all the way to the prototype level: something close to a flight version of the generator,” said Salvatore Oriti, mechanical engineer at Glenn. “The more impressive part is how quickly and inexpensively we got it done, only made possible by a great synergy between the NASA and University of Leicester teams. We were on the same wavelength and shared the same mindset.”
Salvatore Oriti, mechanical engineer in the Thermal Energy Conversion Branch at NASA’s Glenn Research Center in Cleveland, adjusts the Stirling testbed in preparation for testing at the center in January 2025.Credit: NASA/Jef Janis The university provided the heat source simulators and generator housing. The heat source simulator is the exact size and shape of their real americium-241 heat source, but it uses embedded electric heaters to create an equivalent amount of heat to simulate the decay of americium fuel and therefore drive generator operation. The Stirling Research Lab at Glenn provided the test station, Stirling convertor hardware, and support equipment.
“A particular highlight of this (testbed) design is that it is capable of withstanding a failed Stirling convertor without a loss of electrical power,” said Hannah Sargeant, research fellow at the University of Leicester. “This feature was demonstrated successfully in the test campaign and highlights the robustness and reliability of an Americium-Radioisotope Stirling Generator for potential future spaceflight missions, including long-duration missions that could operate for many decades.”
The test proved the viability of an americium-fueled Stirling RPS, and performance and efficiency targets were successfully met. As for what’s next, the Glenn team is pursuing the next version of the testbed that will be lower mass, higher fidelity, and undergo further environmental testing.
“I was very pleased with how smoothly everything went,” Oriti said of the test results. “Usually in my experience, you don’t accomplish everything you set out to, but we did that and more. We plan to continue that level of success in the future.”
For more information on NASA’s RPS programs, visit:
https://science.nasa.gov/rps
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4 Min Read Stay Cool: NASA Tests Innovative Technique for Super Cold Fuel Storage
The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Credits: NASA/Kathy Henkel In the vacuum of space, where temperatures can plunge to minus 455 degrees Fahrenheit, it might seem like keeping things cold would be easy. But the reality is more complex for preserving ultra-cold fluid propellants – or fuel – that can easily overheat from onboard systems, solar radiation, and spacecraft exhaust. The solution is a method called cryogenic fluid management, a suite of technologies that stores, transfers, and measures super cold fluids for the surface of the Moon, Mars, and future long-duration spaceflight missions.
Super cold, or cryogenic, fluids like liquid hydrogen and liquid oxygen are the most common propellants for space exploration. Despite its chilling environment, space has a “hot” effect on these propellants because of their low boiling points – about minus 424 degrees Fahrenheit for liquid hydrogen and about minus 298 for liquid oxygen – putting them at risk of boiloff.
In a first-of-its-kind demonstration, teams at NASA’s Marshall Space Flight Center in Huntsville, Alabama, are testing an innovative approach to achieve zero boiloff storage of liquid hydrogen using two stages of active cooling which could prevent the loss of valuable propellant.
“Technologies for reducing propellant loss must be implemented for successful long-duration missions to deep space like the Moon and Mars,” said Kathy Henkel, acting manager of NASA’s Cryogenic Fluid Management Portfolio Project, based at NASA Marshall. “Two-stage cooling prevents propellant loss and successfully allows for long-term storage of propellants whether in transit or on the surface of a planetary body.”
The new technique, known as “tube on tank” cooling, integrates two cryocoolers, or cooling devices, to keep propellant cold and thwart multiple heat sources. Helium, chilled to about minus 424 degrees Fahrenheit, circulates through tubes attached to the outer wall of the propellant tank.
NASA’s two-stage cooling testing setup sits in a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Tom Perrin The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama.NASA/Kathy Henkel The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Kathy Henkel The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Kathy Henkel Teams installed the propellant tank in a test stand at NASA Marshall in early June, and the 90-day test campaign is scheduled to conclude in September. The tank is wrapped in a multi-layer insulation blanket that includes a thin aluminum heat shield fitted between layers. A second set of tubes, carrying helium at about minus 298 Fahrenheit, is integrated into the shield. This intermediate cooling layer intercepts and rejects incoming heat before it reaches the tank, easing the heat load on the tube-on-tank system.
To prevent dangerous pressure buildup in the propellant tank in current spaceflight systems, boiloff vapors must be vented, resulting in the loss of valuable fuel. Eliminating such propellant losses is crucial to the success of NASA’s most ambitious missions, including future crewed journeys to Mars, which will require storing large amounts of cryogenic propellant in space for months or even years. So far, cryogenic fuels have only been used for missions lasting less than a week.
“To go to Mars and have a sustainable presence, you need to preserve cryogens for use as rocket or lander return propellant,” Henkel said. “Rockets currently control their propellant through margin, where larger tanks are designed to hold more propellant than what is needed for a mission. Propellant loss isn’t an issue with short trips because the loss is factored into this margin. But, human exploration missions to Mars or longer stays at the Moon will require a different approach because of the very large tanks that would be needed.”
The Cryogenic Fluid Management Portfolio Project is a cross-agency team based at NASA Marshall and the agency’s Glenn Research Center in Cleveland. The cryogenic portfolio’s work is under NASA’s Technology Demonstration Missions Program, part of NASA’s Space Technology Mission Directorate, and is comprised of more than 20 individual technology development activities.
Learn more about cryogenic fluid management:
https://go.nasa.gov/cfm
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Last Updated Jul 18, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
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A team from South Dakota State University with their project, “Soil Testing and Plant Leaf Extraction Drone,” took first place at the 2025 Gateways to Blue Skies Forum held May 20-21 in Palmdale, California. Advisor Todd Lechter, left, along with team members Nick Wolles, Keegan Visher, Nathan Kuehl and Laura Peterson, and graduate advisor Allea Klauenberg, right, accepted the award.NASA A team from South Dakota State University, with their project titled “Soil Testing and Plant Leaf Extraction Drone” took first place at the 2025 NASA Gateways to Blue Skies Competition, which challenged student teams to research aviation solutions to support U.S. agriculture.
The winning project proposed a drone-based soil and tissue sampling process that would automate a typically labor-intensive farming task. The South Dakota State team competed among eight finalists at the 2025 Blue Skies Forum May 20-21 in Palmdale, California, near NASA’s Armstrong Flight Research Center. Subject matter experts from NASA and industry served as judges.
“This competition challenges students to think creatively, explore new possibilities, and confront the emerging issues and opportunity spaces solvable through aviation platforms,” said Steven Holz, assistant project manager for University Innovation with NASA’s Aeronautics Research Mission Directorate and Blue Skies judge and co-chair. “They bring imaginative ideas, interesting insights, and an impressive level of dedication. It’s always an honor to work with the next generation of innovators participating in our competition.”
This competition challenges students to think creatively, explore new possibilities, and confront the emerging issues and opportunity spaces solvable through aviation platforms
Steven holz
Assistant Project Manager for University Innovation
The winning team members were awarded an opportunity to intern during the 2025-26 academic year at any of four aeronautics-focused NASA centers — Langley Research Center in Hampton, Virginia, Glenn Research Center in Cleveland, Ames Research Center in California’s Silicon Valley, or Armstrong Flight Research Center in Edwards, California.
“It’s been super-rewarding for our team to see how far we’ve come, especially with all these other amazing projects that we were competing against,” said Nathan Kuehl, team lead at South Dakota State University. “It wouldn’t have been possible without our graduate advisor, Allea Klauenberg, and advisor, Todd Lechter. We want to thank everybody that made this experience possible.”
Other awards included:
Second Place — University of Tulsa, CattleLog Cattle Management System Best Technical Paper — Boston University, PLAANT: Precision Land Analysis and Aerial Nitrogen Treatment Sponsored by NASA’s Aeronautics Research Mission Directorate, this year’s competition asked teams of university students to research new or improved aviation solutions to support agriculture that could be applied by 2035 or sooner. The goal of the competition, titled AgAir: Aviation Solutions for Agriculture, was to enhance production, efficiency, sustainability, and resilience to extreme weather.
At the forum, finalist teams presented concepts of aviation systems that could help the agriculture industry.Students had the opportunity to meet with NASA and industry experts, tour NASA Armstrong, and gain insight into the agency’s aviation mission.
U.S. agriculture provides food, fuel, and fiber to the nation and the world. However, the industry faces significant challenges. NASA Aeronautics is committed to supporting commercial, industrial, and governmental partners in advancing aviation systems to modernize agricultural capabilities.
The Gateways to Blue Skies competition is sponsored by NASA’s Aeronautics Research Mission Directorate’s University Innovation Project and is managed by the National Institute of Aerospace.
The National Institute of Aerospace has made available a livestream of the competition, as well as information about the finalists and their projects, and details about the 2025 competition.
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Last Updated May 22, 2025 EditorLillian GipsonContactRobert Margettarobert.j.margetta@nasa.gov Related Terms
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