Undergrad Aerospace Student Helps Create Igniter for Hypersonic Jet Engine

March 29, 2010 — The technology required to power a hypersonic scramjet engine that can travel five times the speed of sound — meaning a flight from New York to Los Angeles would take 40 minutes — is in the hands of a University of Virginia undergraduate aerospace engineering student.

Ryan Johnson, a fourth-year student leader of the U.Va. Engineering School's hypersonic scramjet program, or "Hy-V," worked with engineers at Aerojet during his summer internship to create an igniter for a scramjet. Johnson, from Catlett, Va., is also completing his independent fourth-year thesis about the research and development of the igniter.

Now under testing in U.Va.'s Aerospace Research Laboratory, which houses a wind tunnel capable of simulating wind speeds up to Mach 5, the igniter will eventually be used in a scramjet flight test. For the flight test, a scramjet engine will be launched as a rocket's payload and will stream data to ground teams. The launch, scheduled for 2011 at the NASA-Wallops Flight Facility on Virginia's Eastern Shore, will allow researchers to compare flight-test data with data that has been collected in various scramjet wind-tunnel experiments around the United States.

With the entire flight test hinging on the success of the igniter, Johnson fully understands the gravity of the situation.

"If the igniter doesn't work, the scramjet doesn't work," Johnson said. "It all comes down to this. If it doesn't ignite, hydrogen will just be spilling out of the back of the engine."

The make-or-break challenge echoes the movie scene that launched Johnson's interest in aerospace engineering. In "Apollo 13," an executive directs a team of ground-based engineers to figure out how to instruct a space crew to repair a machine that converts carbon dioxide into breathable oxygen before the space crew suffocates.

"The crew had only a few hours to react, and in the end they were able to make a converter that saved the lives of the astronauts. I love that scene, and it has always inspired me," said Johnson, who said his passion was further encouraged by participating in a high school rocketry challenge.

The pending launch will be the culmination of research conducted by a team of faculty and students on the Hy-V team over the past four years. To carry out the project, the group is collaborating with the Virginia Space Grant Consortium, NASA, Virginia Tech, Aerojet, Alliant Techsystems Inc. and the U.S. Department of Defense. 

The rocket launch, Johnson's igniter and the wind-tunnel tests are all elements of a research project aimed toward development of a scramjet engine that could allow aircraft to fly five times the speed of sound – or 3,700 mph. This technology could one day be used to transport passengers or packages from New York to Los Angeles in just 40 minutes.

Speed is an obvious advantage of the technology, but hypersonic scramjets offer many benefits over traditional aerospace engines. While conventional rocket engines use oxygen stored in onboard tanks, the oxygen used by scramjets for combustion is taken from the atmosphere. The design would lead to smaller, safer, faster and less-expensive supersonic aircraft.

Because the air flowing through a scramjet must be moving faster than the speed of sound, however, a scramjet cannot take off without a staging engine. A rocket or a conventional jet engine must be used to accelerate the scramjet to a supersonic speed.

The flight test to be conducted in 2011 will use a Terrier Orion sounding rocket to carry the scramjet engine to an altitude of about 80,000 feet while moving at five times the speed of sound. Once the scramjet reaches the correct altitude and speed, the scramjet igniter will be triggered and the experiment will begin. While the engine burns, data will be relayed to the Hy-V team on the ground.

Research and development of the igniter began when Chris Goyne, research assistant professor of aerospace engineering and director of the Aerospace Research Laboratory, contacted Aerojet about finding an igniter for the scramjet launch. Johnson had just started his internship at Aerojet and was assigned to find the appropriate technology.

After reviewing several different igniter options for the launch, Johnson and Mark Friedlander (Aero '83), engineering director for Aerojet, realized that they would need to build their own igniter to meet the requirements of the pending scramjet launch. They needed an igniter that burned hotter and faster than what was available from other sources. 

At first glance, the device Johnson helped design looks like a large steel bolt. The hardware is cut from Grade 303-stainless steel and will hold the type of propellant used for much smaller model rockets available for purchase in a hobby store. The team will use an electrical initiator to provide a pulse of heat to light the igniter and start the combustion. 

Although Johnson led the research and development of the igniter, he couldn't have done it without the help of Aerojet engineers and his fellow Hy-V team members.

When Johnson first started work on the igniter, Aerojet engineers produced a computer model of the igniter in just a day. Friedlander supervised Johnson's work on the project, advising him throughout the process and securing necessary hardware such as the initiator. 

"Mark Friedlander and the Aerojet engineers in the ballistics division were there every step of the way," Johnson said. "They showed me not only how you should do things, but why."

At the Aerospace Research Laboratory, Ed Spencely, an experienced machinist, fabricated the igniter to precise specifications. Hy-V team members have been helping to test the igniter to make sure it burns properly under extreme pressure. Rigorous testing is crucial because the scramjet will need to operate under the acceleration of 20 Gs (A "G" is a unit of measure of acceleration due to gravity at the Earth's surface.)  For comparison, a NASCAR driver is under about 5 Gs of force through turns on the track. The scramjet also will be vibrating and spinning at five rotations per second.

Leading the scramjet igniter project has been a rewarding experience for Johnson. Throughout the process he's learned to apply his education and technical skills to a real-world design challenge.

"For this project, I've been able to use everything I have learned in the classroom and working at ARL for the past three years," Johnson said. "I'm honored to be trusted with this responsibility."

— By Zak Richards