US aerospace and defense giant Boeing and Norwegian defense and aerospace company Nammo have successfully tested a ramjet-powered artillery projectile. Announced on Tuesday, the test took place on June 28 at the Norwegian test center in Andøya.
A ramjet is a structurally simple form of jet engine, with no moving parts; such an engine consists of an inlet, a combustion chamber (with a fuel injector and a flame holder) and a nozzle. To operate, a ramjet must already be in forward motion, as it is this motion that forces air into its inlet. The inlet slows the air, converting dynamic pressure (from velocity) to higher static pressure. In the combustion chamber, the fuel is mixed with air and ignited. The exhaust gases resulting from this combustion then exit through a nozzle, shaped to accelerate the flow of these gases. This exhaust flow being faster than the external air flow around the engine, it generates thrust. (In a ramjet, combustion and exhaust flow always have subsonic velocity.)
With the projectile tested by Boeing and Nammo, the artillery gun discharge provided the initial forward velocity that allowed the ramjet to operate. The test involved a 155mm caliber Boeing ramjet projectile fired from a “barrel” (as Boeing described the gun). During the test, the ramjet successfully ignited and the projectile demonstrated stability in flight, while the engine combustion process was “well controlled”.
“We believe the Boeing Ramjet 155, with continued technology maturation and testing, can help the U.S. military meet its long-range sniper modernization priorities,” said Vice President and General Manager of Boeing Phantom Works. Steve Nordlund. “This successful test is proof that we are making great progress.”
“This is a historic moment for Nammo,” Nammo CEO stressed. Morton Brandtzog. “The test results demonstrate that ramjets are viable and can fundamentally change the future of artillery. We have great confidence in the ramjet concept. The test – with every aspect of firing from the gun, to the projectile body, ailerons and trajectory working perfectly – represents a true technological breakthrough in artillery and a major success for Boeing, Nammo and the US military.
The two companies began development of the ramjet projectile in mid-2019, funded under Phase I of the US Army’s XM1155 program. Last year, they received a Phase II technology development contract.
The US military is looking for long-range guided artillery projectiles, to be able to hit targets much deeper behind an enemy’s front line than conventional artillery can, but not as far as possible using surface-to-surface missiles (which the US military already has and is having new types developed, for future deployment). The 155 mm ramjet projectile is considered a hybrid between a shell and a missile. The current war in Ukraine has dramatically highlighted the enormous importance of long-range but precision artillery, rocket and missile fire.