by Kinsey Love

“Hybrid” is a common buzzword, evoking thoughts of fuel-efficient cars, carbon footprints, and green living. “Hybrid” is also frequently used in Stephen Whitmore’s senior design mechanical engineering class, but for a whole different reason.


Whitmore’s class designs and builds hybrid rockets that fly in competitions, but the class itself is also a hybrid. The class is unique in that it serves two purposes: a capstone course for undergraduates in the mechanical and aerospace engineering program, as well as the basis for USU’s rocket team, called Chimaera. This class style is a new concept to college engineering courses, and mechanical and aerospace engineering researcher Tony Whitmore hopes that his students’ success as rocket designers will lead to recognition for his team and the engineering program at Utah State.

Hybrids play an important role in Whitmore’s team because the students spend an entire year designing and building hybrid rockets, which combine a solid fuel with a liquid oxidizer. When these two fuels react, it creates a gas that propels the rocket forward. “This course provides the students with an opportunity to see their research come to life,” said Whitmore. “The data that they have been crunching for so long suddenly becomes real in the form of a rocket. Having a tangible product allows the students to see their data and research work, or fail for that matter.”


In the past, the team entered their rockets into the national University Student Launch Initiative (USLI) contest, a competition they won two years in a row (sidebar). The rocket that won last year’s USLI competition was powered by a conventional solid-propellant similar in composition to the propellant used for the large strap-on boosters used for space shuttles. The team found that working outdoors with very cold liquid nitrous-oxide oxidizer during Utah’s frigid winters was too difficult, so they opted for a switch to the solid propellant. Once the team settled on their choice of propellant, they were able to finalize their award-winning rocket. After they mastered sending a rocket one mile into the air and back down with exact precision, the team has now set their sights to new heights: the moon. This year, the Chimaera team is drawing from Whitmore’s research to design a centrifugal turbine jet engine that will be used to simulate a lunar landing.

Someday, whether through private ventures or government expeditions, humans will return to the moon. In order to do this, new, more high-tech equipment needs to be developed. This can only happen if proper training vehicles are developed for astronauts to practice, and this is where the Chimaera team comes in. Imagine a gyroscope with rockets holding the inner rings steady and propellers stabilizing the outer rings. This is the basic idea for the jet engine that the USU team will build to-scale, which will offset five-sixths of the gravity on the lander, and will use propellers to offset the remaining one-sixth of the gravity, since gravity on the moon is less than gravity on earth. After the rocket engine is designed and a prototype is built, the students will take it to testing grounds—here on earth, of course—and will fly it remotely to simulate a lunar landing.

The engine design that the Chimaera team is working on is based on Whitmore’s research on aerospike nozzles, or thrusters. “These thrusters are used to compensate for changes in altitude, but are much smaller than previous versions,” said Whitmore. Payloads sent into space that are non-human cost around $20,000 per pound, and human flights cost even more. Smaller payloads are easier to fly and cheaper to build. Because of this, the smaller aerospike nozzles have the potential to play a key role in future lunar missions. “When we work in any aerospace design, smaller equals cheaper, so the aerospike is a good model for the Chimeara team, or any aerospace engineer, to use.”

Aerospike nozzles, which use a series of “exhaust pipes” arranged around a bowl-shaped spike to simultaneously fire exhaust from an engine and serve as the propellant for a rocket, are smaller and less complex than their bell-nozzle counterpart, which uses one large bell-shaped “exhaust pipe” to direct the flow of gases from the engine and create a propellant (see above right). So far, aerospike nozzles have not been widely tested and, therefore, have not been incorporated into working rockets. Whitmore has received $750,000 in funding for research on this nozzle and is working to do more analytical and experimental work with them in order to show that they are ready to be included in propulsion systems. Part of this analysis is now being researched by the Chimaera rocket team.

Whitmore thoroughly enjoys rocket research and working with the Chimaera team. Before coming to Utah State University in 2005, he worked for NASA as a propulsion engineer for over 25 years. “I have set up my class to run like a systems engineering team at NASA,” said Whitmore. “The students oversee each other, beginning with a chief engineer and filtering down through a systems engineer and all of the smaller specialized teams. I am happy to see stereotypes dissolve in this system because our two lead engineers this year are women, and they are doing a great job.” With two USLI victories under his belt, Whitmore and his team have fun learning, designing, and working together. “In what other field do you get to tinker with and launch live rockets?”

The Chimaera team’s centrifugal turbine jet engine is funded through NASA’s Exploration Systems Mission Directorate (ESMD) program, and they plan to submit the end product to NASA upon completion. “The engineering students at USU and their work are so well-received all over the nation,” said Whitmore. “When it comes to rockets and aerospace, Utah is quickly becoming nationally recognized as a key player in the industry.”

whitBell copy

Linear aerospike rocket engine

whitAerospike copy

Normal bell nozzle rocket engine