Highland's AP Physics Students Design, Build and Test Their Own Solid Fuel Ramjet Engine

A cooperative effort between Highland School, University of Virginia, Aerojet Rocketdyne, and the US Army

In addition to his role at Aerojet Rocketdyne, Dr. Pat Hewitt teaches Highland’s AP Physics class. The year-long class requires a complimentary lab project and each year, Dr. Hewitt helps the class choose a unique and relevant project. A fortunate combination of circumstances combined to provide an amazing experience for the students while creating a unique opportunity for Aerojet Rocketdyne to develop a new capability that could prove valuable to future customers.

Students Design and Build a Solid Fuel RamJet Engine

The Solid Fuel RamJet (SFRJ) shown below is an airbreathing engine that uses gases from a burning solid fuel grain for power during flight. There are a number of military applications emerging and the engineers at Aerojet Rocketdyne are currently active in related research and development.

To complement that effort, Dr. Hewitt developed an ambitious lab project for his students. The challenge he presented them was to design, fabricate, and test their own Solid Fuel RamJet engine. As a first step, class teams were established in the areas of Program Management, Hardware, Fuel, Analysis, and Instrumentation. These teams then generated a program plan, a GANTT schedule, and an overall project budget.

A Low-Cost Hardware Solution Was Proposed

A low cost hardware approach was proposed that would make use of readily available items like stainless steel tubing joined with clamps and phenolic tubes for case insulation and fuel grain cartridges. They even created their fuel using a KitchenAid mixer!

Next, detailed drawings were prepared by hand – a topic covered in a unique “Engineering Boot Camp” held at the beginning of the school year. Then, students presented the drawings to Precision Machine Works, a machine shop located in Culpeper. The team at Precision Machine Works graciously fabricated nozzle components and a section to interface with the test facility at Aerojet Rocketdyne per class drawings.

Students Earn Opportunity to Work with University of Virginia Engineering Professor

Additionally, students had the opportunity to work with Dr. Rita Schnipke, a University of Virginia professor, who teaches a fluids engineering class. While Highland students were working on their project, Dr. Schnipke approached the engineering team at AeroJet Rocketdyne for ideas on a design project for Sam Carr, a student at UVA.

Dr. Hewitt provided the air inlet dimensions of the Highland students' project to Sam and his team at UVA. Dr. Hewitt suggested that they model a swirl assembly to potentially assist with mixing and combustion. Then, Highland students adapted their Solid Fuel RamJet to accept the swirl assembly designed by the team at University of Virginia. The insert is scheduled to be 3-D printed from Inconel steel in May and be available for later testing.

Testing and Creating the Solid Fuel Mixture

Back in Warrenton, the fuel team researched prior work and chose a formula using Hydroxy-Terminated Polybutadiene (HTPB), polystyrene and carbon black. After help from Dr. Eric Olson, Highland's AP Chemistry teacher, on mixture fractions, a successful small-scale checkout mix was made. That test batch was then followed by a full-scale mix made in a KitchenAid mixer.

Once the mixture was complete, the fuel was poured into a phenolic tube and spun using an electric motor and belt/pulley system until it cured and formed a solid cylindrical fuel grain. Then, the fuel grain was cut to length to fit in the SFRJ hardware.

Once the fuel was complete, students delivered the assembled test hardware was Aerojet Rocketdyne's facility in Orange County for testing. This is a facility that provides heated air to the engine to simulate performance in flight and an ignition source to initiate fuel combustion. The US Army Aviation and Missile Research Development and Engineering Center (AMRDEC) is developing advanced SFRJ fuels and contracted with AR for engine preliminary design and fuel testing at the Orange facility. The Highland fuel grain served to check out the hardware and test procedure prior to performing testing for the Army.

Test Readiness Review is Final Step Before 'Launch'

A test readiness review presentation was given to Aerojet Rocketdyne test and technology personnel by the class. The presentation covered testing plans, hardware design, and safety considerations. As a result the SFRJ engine was cleared for test.

The motor was tested April 27, 2017 at conditions simulating supersonic flight. The fuel grain was ignited and burned for approximately 10 seconds as planned. The test data indicated that the engine operation was pretty much flawless, clearing the way for subsequent Army fuel work. With the lab complete, thirteen potential aerospace engineers ended up with a satisfying taste of the industry, and some pretty good lab grades to boot!

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Highland School

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