In many ways, the development of cryogenic fuel is facilitating a new era of space exploration.
While space travel has always been synonymous with innovation, developments linked to cryogenic liquids for space propulsion are currently highlighted for their central role in taking humans beyond the final frontier.
Briefly put, the term cryogenic fuel implies the use of fuels that are in a liquid state at extremely low temperatures. This provides the possibility of employing elements with high energy efficiency (mainly liquid hydrogen and oxygen), opening the door to increasingly longer space trips that also have a lower environmental impact.
In this article, we’ll focus on reviewing the functioning of the potential of cryogenic gas in space travel, explaining its advantages and the main challenges involved in its use, such as the development of storage systems for extreme temperatures.
What is cryogenic fuel?
The term cryogenic fuel refers to fuels that, due to their characteristics, must be stored at temperatures below -150°C in order to remain in a liquid state.
These compounds are highly valued for offering a high energy density, that is, for being able to generate a significant amount of energy in relation to their mass. Thus, cryogenic fuels are emerging as a key resource for launching and propelling rockets, especially as part of long-range missions.
Find out our project: Cryogenic tank for the aerospace sector: Cryospain facilitates new steps for liquid hydrogen
What are the essential cryogenic gasses for space propulsion?
Regarding space propulsion, the most commonly used cryogenic fuels today are liquid hydrogen and liquid oxygen, which have already been used in rockets such as the Saturn V or the SLS.
- Liquid hydrogen (LH2) requires a storage temperature of ~ -253°C to remain in its liquid form. It is mainly used as a fuel in high-performance engines. Due to its characteristics, it requires complex cryogenic storage systems, with large, perfectly insulated tanks.
- Liquid oxygen (LOX) requires storage temperatures of ~ -183°C, and is mainly used as an oxidizer in engines, as it is capable of providing high reactivity and is easy to produce and use. Again, a specific storage system is required to ensure its insulation to prevent evaporation.
Both of these elements are stored at extremely low temperatures thanks to cryogenic equipment, which is capable of keeping them in a liquid state and taking advantage of their propulsion capacities.
Combined, hydrogen and liquid oxygen generate hydrolox, a highly efficient cryogenic fuel that also facilitates the development of “clean” space missions, since its combustion only produces water vapor as a byproduct.
Cryogenic liquids in rocket engines
Hydrogen in its liquid form is responsible for feeding the engines of space rockets.
In fact, it is the combustion of oxygen and hydrogen that propels the rocket during the first ten minutes of flight, being key to the success of any space mission.
The process takes place as follows: during the first two minutes of a rocket’s takeoff, the thrust is provided by solid propellant boosters. These side boosters provide 90% of the power needed for takeoff. After this initial period, the main cryogenic stage takes over. This stage consists of two tanks: a hydrogen tank and an oxygen tank.
Furthermore, due to their high performance, cryogenic fuels are also used for upper stage propulsion systems in rockets, as in the case of the Artemis III Interim Cryogenic Propulsion Stage (ICPS).
As such, the use of liquid hydrogen is currently irreplaceable for space propulsion due to its ability to considerably reduce the mass and volume of launchers. Its development is also key to unraveling the challenges for the advancement of the green hydrogen economy, including the design of increasingly efficient cryogenic hydrogen tanks.
This is the case of projects such as the cryogenic tank for the aerospace sector developed by Cryospain capable of meeting fuel demands in rocket launches and large-scale engine tests.
Keep learning: Liquid Oxygen for standardized rocket launch bases: Cryospain’s 2023 space project
Advantages of cryogenic fuel for space exploration
High energy efficiency and performance
Cryogenic fuel has proven its capacity to offer high specific efficiency (thrust generated per unit of fuel), which allows for better performance and greater load capacity compared to other alternatives.
Sustainability and future readiness
The combustion of hydrogen and oxygen does not produce pollutants, so its use as cryogenic fuel stands out to allow sustainable interspace travel. In this sense, it is vital that efforts continue to be made to achieve a hydrogen production process that minimizes its carbon footprint.
In turn, both elements are abundant both on Earth and in space, enhancing their potential to continue advancing in the future of space exploration.
Challenges in storing and handling cryogenic fuel
Cryogenic liquids storage and cryogenic engine requirements
The main technical challenge of cryogenic liquids is the need to design extremely advanced storage systems in terms of thermal insulation and pressure control to avoid evaporation losses.
The reality is that the infrastructure for the production, storage and transport of cryogenic fuels is currently expensive, and their handling requires a high level of specialization. Therefore, improving the efficiency of these cryogenic storage and transport systems will be key to making this technology more affordable and viable for longer space missions.
Decisions regarding the choice of materials play a prominent role in this development. Today, diverse initiatives are emerging looking to find materials that are compatible with the fuels, have high resistance, be light, economically and environmentally viable, and not present problems in terms of thermal expansion or permeability.
Cryogenic applications for fuel management
Extreme temperature and leak management in tanks is another key issue for the creation of cryogenic fuel tanks. In this regard, hydrogen has a molecular diameter prone to leaks, and a concentration of only 4% of this element represents a fire hazard.
This characteristic points to leak management and tank resistance as another of the key challenges for the advancement of cryogenic fuel both in space propulsion and in other potential applications, such as aeronautics.
Cryogenic applications in current and future space missions
Cryogenics is the science dedicated to studying the effects and applications of extremely low temperatures. As such, there are various cryogenic applications that play a fundamental role in various areas of space exploration:
Cryogenic engine technology in modern rockets
As seen throughout the article, space propulsion using cryogenic fuels represents one of the main strategies capable of sending missions to outer space today.
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Current research also indicates that the role of cryogenics for space propulsion will continue to be fundamental. This is perfectly illustrated by the growing interest in the exploration of Mars and other long-range missions to deep space, which involve scenarios in which cryogenic fuels are emerging as one of the most viable options.
Innovations in cryogenic applications for long-term missions
But cryogenic applications for space innovation go beyond the development of fuels. As such, some of the areas in which cryogenics is allowing progress in space research include:
- Development of cryogenic electronic components. These are electronic components that, at cryogenic temperatures, improve their thermal and electrical conductivity and that will be key to improving the efficiency of missions today and in the future.
- Use of vacuum technology to simulate space-like conditions. A crucial step to evaluate the performance of components and systems and ensure that they are reliable under real conditions.
- Satellite thermal management systems. Here, cryogenic science is offering important insights to facilitate the development of future space-science tools that will be key in areas such as high-sensitivity astronomical measurements.
Cryospain: experts in cryogenic solutions for the aerospace sector
Cryospain‘s commitment to advancing cryogenic engineering positions us as key allies for the development of cryogenic storage systems and skids tailored to the most ambitious developments of the current space race.
A capacity that has proven to be key in some of our most recent projects for the aerospace sector:
- Development of a cryogenic tank for liquid hydrogen in Germany. A state-of-the-art project in which we have incorporated cutting-edge systems such as a multi-layer insulation system combined with vacuum insulation to minimise heat transfer and capabilities to meet fuel demands in rocket launches and large-scale engine tests.
- A project linked to liquid oxygen for rocket launch bases. Here, we were in charge of building two skids for the supply of liquid oxygen as part of French startup SpaceDreams’ project, involved in the creation of cutting-edge mobile and standardised rocket launch bases. A project in which our capacity to develop customised cryogenic pump skids has been key.
At Cryospain, we are thus at the forefront of facilitating the use of cryogenic fuels, enabling their safe and reliable storage and use in today’s most cutting-edge projects. Want to learn more? Get in touch with us and talk to our team.
