Raytheon is replacing the US Army's Patriot radar with the Lower Tier Air and Missile Defense Sensor. Some of the prototypes are undergoing testing with the army. (Raytheon)

The US Army is testing two of its new air-defence sensors at White Sands Missile Range (WSMR) in New Mexico, the service recently announced.

The Lower Tier Air and Missile Defense Sensor (LTAMDS) has begun contractor verification testing (CVT), the army's Program Executive Office Missiles and Space (PEO MS) announced on 18 May. The army envisions the radar as a key technology for air defence in Guam and as a replacement for the Phased Array Tracking Radar to Intercept on Target (Patriot), service officials said.

Raytheon Missiles and Defense won a USD383 million contract in 2019 to build six prototypes for the service. Joe DeAntona, Raytheon Missiles and Defense's vice-president of business development, told Janes in March 2023 that the service had begun some testing of the sensors.

A Khorramshahr-4 is test-launched on an unspecified date. (Iranian Defence Ministry/Handout/Anadolu Agency via Getty Images)

The Iranian military unveiled what was presented as a new, more accurate variant of the Khorramshahr, its most powerful ballistic missile, on 25 May.

Called the Khorramshahr-4 (Kheibar), the missile was displayed at an event attended by Defence Minister Amir Mohammad Reza Ashtiani and shown being launched from the missile testing facility in Semnan Province in a video and images.

The Iranian media reported that the new variant has a more advanced engine that uses hypergolic fuel, giving it a range of 2,000 km with a 1,500 kg warhead. Unlike other types of fuel/oxidiser combinations, the new propellant can be kept in tanks for years, shortening the preparation time for a launch to 12 minutes, making it a tactical weapon, it was claimed.

The new propellant also requires smaller tanks, reducing the Khorramshahr's motor section to about 13 m with the warhead adding about 4 m to the missile's length, it was reported. The airframe is also made of a stronger composite material.

Aerojet Rocketdyne provides solid rocket motor boosters and other products for ‘hypersonic' weapons. (Aerojet Rocketdyne artist concept)

The US Army is in the midst of a massive effort to ramp up its production capacity for artillery, but will still have to contend with supply chains for the fuel that powers the in-demand rockets. Ammonium perchlorate (AP) – an oxidiser used in solid rocket fuels – is a crucial ingredient but can be difficult to source.

The number of approved sources for AP increased in recent years, US Office of the Secretary of Defense (OSD) spokesperson Jeff Jurgensen told Janes on 17 May. This comes as the demand for rockets in Ukraine has increased, and concerns about the supply chains for energetics materials have risen, experts said.

Earlier there was only one Department of Defense (DoD)-approved source of grade 1 AP (AP1) in the US, according to a report from the DoD Office of Inspector General (DoD IG) published in July 2020. AP1 is used in weapons employed by the army's Guided Multiple Launch Rocket System (GMLRS), for example. DoD IG said AP1 is used in 16 weapons in total across the DoD.