Ramjet 155 (XM1155)

The Boeing-Nammo Ramjet 155 (US Army program designation XM1155) is a solid-fuel ramjet-propelled 155mm artillery projectile intended to give NATO-standard howitzers stand-off ranges far beyond current rocket-assisted and base-bleed rounds. The projectile is launched conventionally from the gun tube, with the ramjet engine's air intake compressing incoming air purely from the round's own forward motion once it reaches supersonic speed, sustaining high-velocity flight over extended distances after the initial gun-launch boost. Early-2026 testing from a 155mm/58-caliber Extended Range Cannon Artillery (ERCA) system at Yuma Proving Ground set a new US Army record for the longest indirect-fire artillery test and validated stable ramjet ignition and combustion; Nammo's CEO stated the program has cleared its major development hurdles and that production is viable within a relatively short timeframe. Nammo and Boeing have publicly discussed adding a Joint Direct Attack Munition (JDAM)-derived guidance package in the next test phase to give the round precision accuracy against both stationary and moving targets. Independent industry reporting has cited figures around 150 kilometers for the projectile's eventual range, but that figure is not yet an official US Army specification and is not treated as confirmed here; the round remains in the demonstration/development phase and has not been fielded.