Green Thruster (IMAGE) Utah State University Caption USU researchers have developed a 'green' thruster propellant made of printed ABS plastic. The small motors are safer to use because they do not use conventional liquid rocket fuels. Credit USU Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.