The OpFires Project will use throttleable rocket motors on hypersonic missiles to achieve varying ranges in flight; therefore, OpFires can hit targets within the range envelope up to 1,000 miles (1,609 kilometers). At Mach 5+, the OpFires’ warhead can fly 1,000 miles in approximately 20 minutes.
Typically, once ignited, rocket motors burn tremendous amounts of fuel that is converted into energy to fly a certain distance at full thrust. However, to hit a target closer than the maximum range distance of the missile would require the missile to slow down or “throttle” its engine thrust to adjust for course corrections in its flight trajectory. Slowing down with unburnt fuel, equating to unexpended weight onboard, adds aerodynamic stress to the missile body casing if performed incorrectly and that might cause the missile to break apart in flight, especially at hypersonic speeds. Nonetheless, throttling the engine is necessary or else the missile might overshoot the target if the rocket motor cannot adjust its thrust levels, and that is what makes the DARPA/Lockheed Martin OpFires medium-range hypersonic missiles unique because throttling a rocket motor effectively is a difficult engineering challenge.
The U.S. Navy’s Conventional Prompt Strike (CPS) and the U.S. Army’s Long-Range hypersonic Weapon (LRHW) also use thrust-vectoring rocket motors to throttle the thrust and allow for long-range maneuvering in flight.
These hypersonic missiles fit within the U.S. Army’s Long Range Precision Fires (LRPF) strategy of differing ranges for U.S. 155mm extended-range artillery shells and for various precision missiles as outlined by Breaking Defense. The same media outlet also discusses the OpFires Project with its unique throttleable rocket motor.
While DARPA and Lockheed Martin are developing OpFires mainly for the U.S. Army, the U.S. Marine Corps (USMC) might also take an interest because the USMC also has a 5-axle 10×10 truck that is very similar to the cross-country U.S. Army’s Palletized Load System (PLS) tractor.
US Army and USMC interest in OpFires
Is the U.S. Army interested in OpFires that DARPA is developing? Naval News asked DARPA on if the OpFires is an official Program of Record with the U.S. Army and received a reply via email on 4 November, 2021.
“We [DARPA] feel it would be inappropriate [to] speak on behalf of the [U.S.] Army with regard to their future [OpFires] plans regarding this ground-launched medium-range hypersonic weapon.
“I can note, however, just this summer we successfully completed full-scale static test firing of a second stage propulsion system that provides a solid-fuel `throttleable’ rocket motor, which can be turned off before burning through all of its fuel, allowing a missile to hit targets located anywhere within a medium-range continuum. This capability, combined with the booster’s volumetric efficiency, will help advance the development of hypersonic missiles that can literally adjust on the fly.
“Data from this and subsequent tests is being used to complete detailed design of the booster that are part of missile fabrication, assembly, and flight testing in the OpFires project’s Phase 3b, currently underway.”
Jared Adams, Chief of Communications, DARPA
Naval News also asked the U.S. Army’s Program Executive Office (PEO) for Missiles and Space for comment on OpFires. The Public Affairs PEO spokesperson forwarded the inquiry to the hypersonics Department and Naval News received no comment before publishing.
Naval News also asked the U.S. Marine Corps on if they’re interested in the DARPA OpFires program and the USMC Public Affairs spokesperson generally stated that the U.S. Marines may be interested in what the U.S. Army does with the DARPA OpFires program. Naval News interprets the Marines’ comment similar to DARPA’s comment in that the U.S. Army and U.S. Marines do not want to prematurely commit to OpFires just yet, pending on testing and development progress with DARPA.
The graphics of the OpFires PLS and LVSR do not appear to show the OpFires launcher assembly being able to rotate, but with a throttleable rocket motor, the hypersonic missile should in theory, be able to course-correct, maneuver and steer in any direction to fly to targets to the side or behind the OpFires launcher. Does the PLS and LVSR have to steer towards the direction of the threat, meaning that the hypersonic missiles can only fire and fly forward?
Without confirming on if the OpFires missile can veer to the sides or make a U-turn mid-course to fly behind the elevated launcher, DARPA simply stated that, “OpFires is maneuverable, and the extinguishable propellant technology allows the operational system to hold a broad kinematic footprint of targets at risk.”
Naval News comments
Naval News will speculatively for discussion purposes analyze the DARPA OpFires benefits to the U.S. Army and to the U.S. Marines if they do decide to adopt OpFires as an official Program of Record as depicted on the 5-axle 10×10 wheeled PLS and LVSR truck graphics.
OpFires Increases Tactical Hypersonic Missile Capability
Three main issues affect the current longer-range U.S. Navy’s Conventional Prompt Strike (CPS) and the U.S. Army’s Long-Range Hypersonic Weapon (LRHW) missiles.
One is “tactical mobility.” CPS and LRHW both require one 45.5-feet long M870A3 trailer and a 34 feet (10.4 meter) M983A4 tractor to tow two CPS or LRHW hypersonic missiles per trailer. This tractor-trailer combination can be bulky, unwieldly, and not as mobile and deployable as an independent self-contained all-wheel drive cross-country truck with hypersonic missiles on its back and no trailer to tow because free-wheeling trailers can get stuck in terrain or jackknife. Thus, long trailers are often limited to even terrain and roads and require large ground clearings to fire their missiles. Furthermore, seen as a “Strategic asset,” CPS and LRHW might be deployed in major conflicts, not regional crisis or everyday patrols and deterrent missions.
Second is “logistics spacing.” The CPS and LRHW tractor-semi trailer Transporter Erector Launcher (TEL) combination is roughly 80 feet long, or too long to fit aboard a U.S. Navy’s Landing Craft Air Cushion (LCAC) or Surface to Shore Connector (SSC) hovercraft for transport to the beach. The CPS and LRHW can fit inside and/or on the Navy’s Light Amphibious Warship (LAW) and Landing Craft Utility (LCU), slow and smaller transport crafts with speeds of around 11-14 knots compared to the LCAC and SSC hovercrafts with speeds of 40+ knots. The ability to deploy CPS and LRHW requires larger cargo aircraft and vessels than one 10×10 wheeled truck. Being mounted on trailers, they often assume parked firing positions, having to find a space large enough to accommodate the 80-foot-long system to fire two 34.5” (2.87 feet or 0.87 meters) diameter hypersonic missiles. Reload times aren’t short and easy as the entire missile canister needs to be replaced on the trailer with a large crane.
Third is cost. The CPS and LRHW fly at ranges of over 1,725 miles (2,776 kilometers) and are larger, expensive, rare, and often used against the most important strategic targets. Both missiles use a Common Hypersonic Glide Body (CHGB) warhead that separates from the missile body and flies down on the target at speeds in excess of Mach 5, destroying the target with kinetic force alone.
OpFires remedies the first issue of tactical mobility with the Army PLS or USMC LVSR 5-axle 10×10 wheeled truck that excels in cross-country mobility and has a better turning radius than a trailer. OpFires is self-contained, and as the top graphic shows, the three missiles fit on a rail assembly system that can be loaded onto the back of a 5-axle truck. The entire missile assembly system can be removed for reloading or for converting the PLS and LVSR back into a logistics vehicle. The PLS and LVSR often have an armored cab and could also have rooftop weapons for self-defense.
This outdated graphic below shows seven LVSRs in a U.S. Marine Expeditionary Unit (MEU). The AAVs are being replaced by Amphibious Combat Vehicles (ACV), the AV-8Bs by F-35Bs, and all four M1A1 Abrams tanks have since been divested in a MEU. Theoretically, if four more LVSRs were added to replace the four divested M1A1 tanks in the MEU, the USMC can hypothetically have 11 LVSRs with three hypersonic missiles each, equating to 33 medium-range ready-to-fire hypersonic missiles in a single standard deployment MEU. Since OpFires is a detachable rail rack off the back of the LVSRs, more than 11 OpFires medium-range hypersonic missile system assemblies can be aboard a MEU.
According to the MAGTF graphic, 30 MTVRs are carried aboard a MEU, and while the MTVRs come in many variants, one can assume that some of them are the MTVR Mark 27 and Mark 28 Extended Cargo Trucks (20-foot body) or the Mark 37 HIMARS Resupply Vehicle, meaning that these MTVRs can in theory carry more OpFires missile containers or the entire three-missile erector launch assembly for the LVSR and reload them in the field, theoretically meaning more than 33 missiles on 11 LVSRs. Such a MTVR logistics capability would be advantageous for the Marine Corps as the LVSR Transporter Erector Launchers (TELs) would not have to return to a forward staging base (FSB) or the amphibious ship to resupply with OpFires medium-range hypersonic missiles, but instead have the MTVRs drive to their locations to resupply and rearm for true “Shoot and Scoot” Long-Range Precision Fires (LRPF) capabilities. The MEU’s LCACs, LCUs, and KC-130J cargo aircraft also provide logistics support to OpFires and the Marines’ LRPF tactical mobility capabilities that may also include CPS trailers and NMESIS Naval Strike Missiles depending on the situation.
The MEU graphic also appears to show two wheeled cranes (Engineers) that can unload and replace the entire OpFires assembly or replace individual fired hypersonic missile containers on the LVSRs.
To address the second issue of “logistics spacing,” at 36.02 feet (10.98 meters) long and 8.16 feet (2.49 meters) wide, the USMC’s LVSR will fit aboard the 67-foot cargo area deck of the LCAC and SSC hovercrafts. The U.S. Army’s PLS shares about the same dimensions, give or take a foot and a few inches, compared to the Marines’ LVSR.
Finally, OpFires addresses cost as the entire unit is self-contained and removable and being smaller, should cost less than the strategic Marines’ CPS and the Army’s LRHW missiles.
OpFires Usage and Benefits to the U.S. Marine Corps and to the U.S. Navy
With over a 1,000-mile range, OpFires’ medium-range hypersonic missiles are intended to penetrate Anti-Access/Area Denial (A2AD) situations with warheads that dive down on targets such as Surface to Air Missile (SAM) vehicles and sites, Anti-Ship missile vehicles and sites, mobile missile launchers, shore-based communications and sensors, radar sites, artillery sites, and fixed structures that threaten a naval strike and amphibious force. OpFires would offer a huge tactical mobility capability and benefit for the USMC and the U.S. Navy if OpFires can be launched from ships at sea such as from the open-deck LUSV. Thus, outside or near the edge of the adversary’s Weapons Engagement Zone, the U.S. Navy and the USMC can attack land and shore-based targets from a standoff distance before the shorter-ranged fighter/bombers flying off of aircraft carriers enter the scene. OpFires will increase the LRPF distance of the naval force for the Combat Commander, providing a game changing force multiplier instead of waiting for the toted U.S. Army’s 1,000-mile cannon with extended-range GPS shells that may or may not come into fruition.