Boron as rocket fuel has been a tough nut to crack.
Rocket scientists in China are working to develop a boron-powered supersonic missile that can fly like a commercial airliner and then swim in the water to act as a torpedo, South China Morning Post.
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Boron is a highly reactive light element that reacts equally well with water as it does with air to release vast amounts of heat. The U.S. Air Force experimented with boron in the 1950s to increase the power of its supersonic bombers. However, the project was shelved since ignited boron is hard to control and also forms a layer of debris that impacts rocket performance.