According to a new study by UC Riverside, a chemical used in electric vehicle batteries can also provide us with carbon-free fuel for spaceflight.
In addition to reducing emissions, this chemical also has a number of advantages over other types of rocket fuel: higher energy, lower costs and no requirements for frozen storage.
The chemical, ammonia borane, is currently used to store hydrogen in fuel cells that power electric vehicles. UCR researchers now understand how this combination of boron and hydrogen can release enough energy to launch rockets and satellites.
“We were the first to demonstrate that in addition to electric vehicles, ammonia borane can be used to launch missiles in the right conditions,” said Pritvis Biswas, a UCR chemical engineer and the first author of the new study. Their demonstration is now published in Journal of Physical Chemistry C.
The most commonly used rocket fuel is based on hydrocarbons and is known to have many negative effects on the environment. They can poison the soil for decades, cause cancer, and cause acid rain, ozone holes, and greenhouse gases such as carbon dioxide.
On the contrary, after burning ammonia-borane releases benign compounds of boron oxide and water. “It’s much less harmful to the environment,” Biswas said.
Compared to hydrocarbon fuels, ammonia-borane also emits more energy, which can potentially lead to cost savings because less is required for the same flight.
To release energy from the fuel and ensure combustion, catalysts and oxidants are added, which provide additional oxygen to the fuel. Catalysts are often used in fuel cells for this purpose. They increase the rate of combustion, but they also remain in the same form both before and after the reaction.
“Spaceships require a lot of energy in a short period of time, so using a catalyst is not ideal because it doesn’t help you get the energy you need. It’s like dead weight in your gas tank,” said Pankaj Guildial of the University of Maryland PhD Chemistry student and co-author. research, now working at UCR.
The inherent chemistry of the decomposition of ammonia collects prevents the release of its total energy when reacted with most oxidants. However, researchers have found an oxidant that alters the mechanisms of decomposition and oxidation of this fuel, leading to the extraction of its total energy.
“This is similar to the use of catalytic converters for complete combustion of hydrocarbon fuels,” said the Guild. “Here we were able to create a more complete combustion of chemicals and increase the energy of the whole reaction, using the chemistry of the oxidant itself, without the need for a catalyst.”
In addition to creating unwanted by-products, some rocket fuels also require storage at sub-zero temperatures. “NASA used liquid hydrogen, which has a very low density,” said the Guild. “Therefore, maintenance requires a lot of space as well as cryogenic conditions.”
On the contrary, this fuel is stable at room temperature and resistant to high temperatures. In this study, researchers created very small, nanosized ammonium-borane particles that can break down within a month in a very humid environment.
The research team is now studying the method of aging ammonium borane particles of different sizes in different media. They are also developing methods to encapsulate fuel particles in a protective coating to increase their stability in wet conditions.
The study was led by Michael R. Zachary, a professor of chemical engineering at UCR, and was funded by the U.S. Defense Threat Reduction Agency program as well as the Office of Naval Research. The agency has allocated funds to produce cleaner and more efficient fuel for flights.
The quantum chemistry calculations needed to support the experimental observations in this study were performed in collaboration with UCR materials scientists Hyuna Kwon and Brian M. Wong.
“We have identified the fundamental chemistry that provides this combination of fuel and oxidant,” Biswas said. “Now we are looking forward to how it works on a large scale.”