The U.S. Navy took the first step to reintroducing to the fleet an old-but-much-needed technology when it successfully tested a solid-fuel ramjet engine at Naval Air Warfare Center Weapons Division (NAWCWD) in China Lake, California.
As threats emerge that require an ability to strike targets from farther out to sea than ever before, the Navy is revisiting the solid-fuel ramjet—an air-breathing engine that can propel a missile up to three times the distance and at higher speeds than a standard solid rocket motor.
In a traditional rocket motor, oxidizer can make up roughly 90 percent of the rocket’s propellant, Walker said. Meanwhile, a ramjet engine—a technology first conceived in Europe in the 1910s—uses its vehicle’s forward motion to draw in oxygen from the surrounding atmosphere, allowing more room for fuel and making it four-to-five times more fuel efficient than a solid rocket motor, he said.
Larger fuel stores also allow a ramjet to sustain high speed during flight, making it harder to shoot down than a solid rocket motor, which exhausts its fuel shortly after launch and then rapidly slows down, he said.
Though most ramjets are liquid fuel, which generally burns more efficiently, solid fuel can be packed more densely, meaning a solid-fuel rocket can typically fly farther, Walker said.
“We are consistently seeing that solid fuel ramjets will fly about three times the distance as a solid rocket motor of the same size,” Walker said.