Anduril and Raytheon test new rocket motor as US works to restore air-to-air superiority

Adversaries are building air-to-air capabilities designed to out-range the US and strike at key enabler aircraft. They can now engage targets from hundreds of kilometres away and the US is working to regain a range advantage. This Anduril and Raytheon announcement indicates that improved rocket motor design could be part of the solution. 

Anduril and Raytheon have successfully tested a new solid rocket motor with a Highly Loaded Grain (HLG) configuration, which translates “directly into extended range and greater tactical advantage for U.S. and allied warfighters,” an October 7 press release states.

The tests were conducted in partnership with Raytheon’s Advanced Technology business and the Air Force Research Laboratory Munitions Directorate, and validated the design. Anduril’s press release adds that the HLG has been developed and built by the company using technology from Naval Air Weapons Station China Lake. This is a US Navy facility in the Mojave Desert that is used for testing and evaluation. 

The HLG configuration for the rocket motor means that the amount of propellant loaded into the motor is increased relative to the inert mass – things like the nozzles, casing etc. that do not contribute to propulsion. This increases the volumetric efficiency of the rocket motor and its total impulse – the amount of thrust it delivers once lit. In a nutshell, this should enable the missile powered by the rocket motor to fly further. 

The development was supported by “crucial technical expertise and oversight” from Raytheon throughout. Raytheon is understood to have filed a patent in 2022 that states, “HLG/BRE [Highly Loaded Grain/Burn Rate Enhancer] motors are susceptible to unpredictable performance variations due to inconsistencies in the orientation of the BRE-wires. The present disclosure solves these inconsistencies.” 

The following disclosure describes how a rocket motor includes an inert rod carrying a wire. The wire is designed to control the burn rate of the rocket motor to maximise and optimise its performance. The Raytheon patent appears to describe an improved methodology for wrapping the wire around the inert rod. Raytheon has also worked on extending the range of the AMRAAM family, with a recent test reportedly hitting a target at greater range than the USAF has ever achieved. 

Anduril and the rocket motor market

Anduril procured Adranos, a solid rocket motor company in 2023, and has since secured a $14.3 million investment from the US government designed to recapitalise rocket motor production in the US. This is combined with Anduril’s own $75 million investment in new production techniques and the design of a new 120 mm (4.75 inch) rocket motor under a contract from the US Army. The aim of the contract is to design a new rocket motor that will increase the number of rockets carried by an M142 HIMARS while retaining the range and lethality of the existing rockets.

Past announcements indicate that Anduril is working with a type of fuel called ALITEC. ALITEC uses an aluminum-lithium alloy fuel, which is similar to a traditional aluminium powder based fuel except that the lithium can increase the energy output and improve burn efficiency. It is also extremely light, meaning that it can potentially add energy density without dramatically increasing weight.

Anduril is not the only company in the HLG space. A US Gov website covering contracts provides an overview of several contracts between 2020 relating to the development of HLG rocket motors for air defence interceptors that are summarised below. 

• December 2020: Corvid Technologies and Aerojet-Rocketdyne contracted to develop a “highly loaded grain (HLG) rocket motor that will exceed the total impulse of the current baseline motor by a minimum of 20%.”
• December 2020: Triton contracted to demonstrate the feasibility of nanoenergetic additives for HLG rocket motors to further increase their capabilities. 
• July 2022: Advanced Cooling Technologies, Sierra Engineering and Software, and Pennsylvania State University contracted by the Missile Defence Agency to develop “highly loaded solid rocket motor packed with high density energetic materials capable of producing a vacuum specific impulse of at least 280 seconds and a 20% increase in total impulse.” This followed an earlier research and development contract from 2020. 
• September 2022: Exquadrum contracted to integrate technologies developed under a 2020 contract into a “a high-performance rocket motor to serve as a missile defense interceptor upper stage.”

This indicates that the subject of HLG rocket motors has been live for some time and that the US DoD has invested in elements of its supply chain that can support continued development, and hopefully some competition. 

Calibre comment: Gilding the lily? 

Russia and China have air-to-air weapons with ranges up to 350 km based on various estimates. Russia’s R-37M has been used operationally in Ukraine, fired from Su-35s and is credited with a successful kill against a jet at ‘technically impressive ranges.’ It is thought to be capable of hitting targets out to 200 km, weighs slightly more than 500 kg and is four metres long. China’s PL-17 is believed to have a range of 400 km and a length of six metres, while the earlier PL-15 is four metres long and weighs 230 kg. The AIM-120 family, by contrast, weighs just 161 kg at a length of 3.65 metres. 

So, the question here is what does the US want to engage at longer ranges from the air? If, like Russia and China, the goal is large high value aircraft like tankers an AWACS, then it is probably ok to simply use a bigger missile with a larger motor. This appears to be the route taken by the PL-17. If, however, the goal is very long-range engagements against manoeuvring targets, then development of enhanced rocket motors that fit within the current space and design constraints of US aircraft does make a lot of sense. The US keenly feels the “tyranny of distance” in the Indo-Pacific, and has multiple projects underway to try and mitigate the impact that has. Longer range rocket motors for air-to-air missiles are likely on the roadmap too. 

By Sam Cranny-Evans, published on October 9, 2025. The lead image shows an F/A-18 Hornet with Marine Fighter Attack Squadron (VMFA) 323, MAG-11, 3rd Marine Aircraft Wing (MAW), carrying ten AIM-120 and two AIM-9X Air-to-Air missiles. The AIM-120 is an effective air-to-air missile, but adversary developments are beginning to out-range it. Credit: US Marine Corps photo by Sgt. Dominic Romero.