Unusual US flights may signal secret HACM hypersonic missile testing in Australia
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Unusual aerial activity involving a modified Gulfstream G550 jet from the U.S. Missile Defense Agency with an Australian P-8A maritime patrol aircraft over Australia’s Woomera Range Complex may indicate testing of the future Hypersonic Attack Cruise Missile (HACM).
The suspected operation highlights progress in developing high-speed precision strike capabilities designed to penetrate advanced air defenses and rapidly engage time-sensitive targets. The activity suggests ongoing test preparation or data collection under the SCIFiRE program, reinforcing efforts to accelerate hypersonic weapon readiness and strengthen U.S.-Australia interoperability in response to emerging peer threats.
Read also: How far have US hypersonic weapon programs currently progressed compared to initial deployment plans?
The Hypersonic Attack Cruise Missile, or HACM, is an air-launched hypersonic cruise missile developed to travel at speeds exceeding Mach 5 and potentially reaching Mach 8, placing it among the fastest weapons under development. (Picture source: Raytheon Missiles & Defense)
On March 23, 2026, The Nightly revealed that coordinated aerial movements and personnel deployments might indicate a possible U.S. testing of the Hypersonic Attack Cruise Missile (HACM) is underway at the Woomera Range Complex in South Australia, where officials from the Missile Defense Agency arrived shortly before sensitive operations began within the restricted zone. A high-altitude observatory aircraft linked to this agency transited from Hawaii through Guam and was tracked flying along the boundaries of the Woomera Protected Area, while an Australian P-8A Poseidon conducted parallel surveillance sorties in the same airspace.
These events occurred without prior announcement, and both U.S and Australian authorities declined to confirm whether a missile launch took place, maintaining the ambiguity. Hover, sources confirmed to The Nightly that the activity was linked with ongoing work under the SCIFiRE program, which targets the rapid development of an air-launched hypersonic cruise missile known as HACM. The timing and configuration of assets suggest test preparation or data collection linked to flight trials, as part of a broader effort to accelerate hypersonic capability development in response to Chinese and Russian counterparts already in testing or service.
Air activity over Woomera during the period was characterized by repeated passes of a modified Gulfstream G550 jet (tail number: N551HA) configured for intelligence and telemetry collection, operating at high altitude along the perimeter of the restricted range rather than directly overhead, a pattern consistent with monitoring of test trajectories or instrumentation calibration. The concurrent deployment of an RAAF P-8A Poseidon added maritime and overland surveillance coverage, suggesting coordinated data gathering across multiple domains. Flight tracking indicated persistent loitering behavior rather than transit operations, reinforcing the likelihood of ongoing test-related activity.
Government responses emphasized that U.S aircraft regularly operate in Australia under established agreements, but avoided addressing the specific mission profile observed. No notices or public warnings of missile launches were issued, consistent with controlled access and the remote location of the range. The absence of confirmation, combined with visible operational indicators, reflects standard practice for classified weapons testing, a pattern already observed in prior hypersonic-related activities at remote test sites. The Woomera Range Complex covers an area exceeding 120,000 square kilometers in remote South Australia, providing one of the largest overland weapons testing environments globally, with restricted airspace and controlled ground access extending across desert terrain.
Its isolation allows for long-range flight paths exceeding 1,000 kilometers without overflying populated areas, a requirement for hypersonic systems operating at speeds above Mach 5. The site includes radar tracking stations, telemetry receivers, and optical instrumentation capable of monitoring high-speed flight and collecting aerodynamic and thermal data. Woomera has supported decades of missile and aerospace testing, including joint U.S-Australia programs such as HIFiRE, which conducted multiple scramjet-related experiments reaching hypersonic velocities. The range’s infrastructure allows integration of airborne and ground-based sensors, enabling precise measurement of flight parameters. Limited global availability of comparable facilities has increased reliance on Woomera for hypersonic trials, due to both geographic advantages and longstanding bilateral defense arrangements.
The SCIFiRE program, initiated as a joint U.S-Australia effort, focuses on developing an operational air-launched hypersonic cruise missile (the HACM) within a compressed timeline, building on more than fifteen years of prior research into scramjet propulsion and related technologies. The program integrates work on supersonic combustion engines, advanced thermal protection systems, guidance sensors, and manufacturing techniques required for sustained hypersonic flight. It operates within the AUKUS Pillar 2 framework, which prioritizes advanced military technologies, including hypersonics, quantum systems, and autonomous capabilities. The objective is to produce a missile capable of sustained flight at hypersonic speed with maneuverability and precision targeting.
This effort responds to the deployment of multiple hypersonic systems by China and Russia, including boost-glide and scramjet-powered designs. SCIFiRE also enables shared testing infrastructure and data exchange between the two countries. The program is structured to transition from research to operational capability within a five-year prototyping cycle. The Hypersonic Attack Cruise Missile (HACM) is said to be a compact air-launched weapon capable of speeds exceeding Mach 5 and potentially reaching Mach 8, corresponding to velocities of up to 9,800 km/h, with an operational range of about 1,000 nautical miles or 1,900 kilometers. Unlike larger boost-glide systems, it is sized for carriage on tactical aircraft, including F-15E, F/A-18F, F-35A, EA-18G, and P-8A, enabling a wider deployment across air forces.
The HACM hypersonic missile is intended to engage high-value or time-sensitive targets with reduced reaction time due to its velocity and maneuverability. Its air-launched configuration allows dispersal across multiple aircraft types rather than reliance on dedicated launch systems. Current planning targets initial operational capability by fiscal year 2027, following rapid prototyping and limited flight testing. The design draws from earlier programs such as the Hypersonic Air-breathing Weapon Concept (HAWC), incorporating lessons learned from prior scramjet experiments.
The propulsion system of the HACM uses a two-stage sequence in which a solid rocket booster accelerates the missile to the required initial speed, typically above Mach 4, after which a scramjet engine ignites to sustain hypersonic cruise using atmospheric oxygen for combustion. This air-breathing configuration eliminates the need to carry oxidizer, reducing mass and enabling longer range compared to purely rocket-powered systems. The scramjet operates by compressing incoming air at supersonic speed, mixing it with fuel, and maintaining combustion within milliseconds as airflow passes through the engine. This enables sustained flight at high velocity while allowing trajectory adjustments during flight.
Compared to boost-glide systems such as ARRW or the land-based Dark Eagle, which follow ballistic arcs before gliding, the HACM maintains powered flight throughout its trajectory. However, like the SR-71 Blackbird, this approach requires managing extreme thermal loads, with surface temperatures reaching levels that demand advanced heat-resistant materials and active cooling techniques. Combustion stability and fuel-air mixing at high speed also remain key engineering constraints. Development of the HACM has encountered measurable delays, including a shift in the critical design review from early 2024 to September 2024, which compressed the available testing window before planned fielding.
As a result, the number of flight tests prior to operational decision has been reduced to five, limiting the volume of empirical data available for validation. The program operates under a rapid prototyping framework with a target of fielding an initial capability by fiscal year 2027, despite the reduced test schedule. Cost growth has been recorded, with total development expenditure approaching $2 billion, reflecting increased complexity and manufacturing challenges. Industrial considerations include scaling production capacity and ensuring compatibility with multiple aircraft types, which requires extensive integration work. However, the presence of advanced U.S systems and personnel on Australian territory has generated domestic debate regarding transparency and sovereignty, particularly in the absence of detailed disclosures about testing activities.
Written by Jérôme Brahy
Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.
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Unusual aerial activity involving a modified Gulfstream G550 jet from the U.S. Missile Defense Agency with an Australian P-8A maritime patrol aircraft over Australia’s Woomera Range Complex may indicate testing of the future Hypersonic Attack Cruise Missile (HACM).
The suspected operation highlights progress in developing high-speed precision strike capabilities designed to penetrate advanced air defenses and rapidly engage time-sensitive targets. The activity suggests ongoing test preparation or data collection under the SCIFiRE program, reinforcing efforts to accelerate hypersonic weapon readiness and strengthen U.S.-Australia interoperability in response to emerging peer threats.
The Hypersonic Attack Cruise Missile, or HACM, is an air-launched hypersonic cruise missile developed to travel at speeds exceeding Mach 5 and potentially reaching Mach 8, placing it among the fastest weapons under development. (Picture source: Raytheon Missiles & Defense)
On March 23, 2026, The Nightly revealed that coordinated aerial movements and personnel deployments might indicate a possible U.S. testing of the Hypersonic Attack Cruise Missile (HACM) is underway at the Woomera Range Complex in South Australia, where officials from the Missile Defense Agency arrived shortly before sensitive operations began within the restricted zone. A high-altitude observatory aircraft linked to this agency transited from Hawaii through Guam and was tracked flying along the boundaries of the Woomera Protected Area, while an Australian P-8A Poseidon conducted parallel surveillance sorties in the same airspace.
These events occurred without prior announcement, and both U.S and Australian authorities declined to confirm whether a missile launch took place, maintaining the ambiguity. Hover, sources confirmed to The Nightly that the activity was linked with ongoing work under the SCIFiRE program, which targets the rapid development of an air-launched hypersonic cruise missile known as HACM. The timing and configuration of assets suggest test preparation or data collection linked to flight trials, as part of a broader effort to accelerate hypersonic capability development in response to Chinese and Russian counterparts already in testing or service.
Air activity over Woomera during the period was characterized by repeated passes of a modified Gulfstream G550 jet (tail number: N551HA) configured for intelligence and telemetry collection, operating at high altitude along the perimeter of the restricted range rather than directly overhead, a pattern consistent with monitoring of test trajectories or instrumentation calibration. The concurrent deployment of an RAAF P-8A Poseidon added maritime and overland surveillance coverage, suggesting coordinated data gathering across multiple domains. Flight tracking indicated persistent loitering behavior rather than transit operations, reinforcing the likelihood of ongoing test-related activity.
Government responses emphasized that U.S aircraft regularly operate in Australia under established agreements, but avoided addressing the specific mission profile observed. No notices or public warnings of missile launches were issued, consistent with controlled access and the remote location of the range. The absence of confirmation, combined with visible operational indicators, reflects standard practice for classified weapons testing, a pattern already observed in prior hypersonic-related activities at remote test sites. The Woomera Range Complex covers an area exceeding 120,000 square kilometers in remote South Australia, providing one of the largest overland weapons testing environments globally, with restricted airspace and controlled ground access extending across desert terrain.
Its isolation allows for long-range flight paths exceeding 1,000 kilometers without overflying populated areas, a requirement for hypersonic systems operating at speeds above Mach 5. The site includes radar tracking stations, telemetry receivers, and optical instrumentation capable of monitoring high-speed flight and collecting aerodynamic and thermal data. Woomera has supported decades of missile and aerospace testing, including joint U.S-Australia programs such as HIFiRE, which conducted multiple scramjet-related experiments reaching hypersonic velocities. The range’s infrastructure allows integration of airborne and ground-based sensors, enabling precise measurement of flight parameters. Limited global availability of comparable facilities has increased reliance on Woomera for hypersonic trials, due to both geographic advantages and longstanding bilateral defense arrangements.
The SCIFiRE program, initiated as a joint U.S-Australia effort, focuses on developing an operational air-launched hypersonic cruise missile (the HACM) within a compressed timeline, building on more than fifteen years of prior research into scramjet propulsion and related technologies. The program integrates work on supersonic combustion engines, advanced thermal protection systems, guidance sensors, and manufacturing techniques required for sustained hypersonic flight. It operates within the AUKUS Pillar 2 framework, which prioritizes advanced military technologies, including hypersonics, quantum systems, and autonomous capabilities. The objective is to produce a missile capable of sustained flight at hypersonic speed with maneuverability and precision targeting.
This effort responds to the deployment of multiple hypersonic systems by China and Russia, including boost-glide and scramjet-powered designs. SCIFiRE also enables shared testing infrastructure and data exchange between the two countries. The program is structured to transition from research to operational capability within a five-year prototyping cycle. The Hypersonic Attack Cruise Missile (HACM) is said to be a compact air-launched weapon capable of speeds exceeding Mach 5 and potentially reaching Mach 8, corresponding to velocities of up to 9,800 km/h, with an operational range of about 1,000 nautical miles or 1,900 kilometers. Unlike larger boost-glide systems, it is sized for carriage on tactical aircraft, including F-15E, F/A-18F, F-35A, EA-18G, and P-8A, enabling a wider deployment across air forces.
The HACM hypersonic missile is intended to engage high-value or time-sensitive targets with reduced reaction time due to its velocity and maneuverability. Its air-launched configuration allows dispersal across multiple aircraft types rather than reliance on dedicated launch systems. Current planning targets initial operational capability by fiscal year 2027, following rapid prototyping and limited flight testing. The design draws from earlier programs such as the Hypersonic Air-breathing Weapon Concept (HAWC), incorporating lessons learned from prior scramjet experiments.
The propulsion system of the HACM uses a two-stage sequence in which a solid rocket booster accelerates the missile to the required initial speed, typically above Mach 4, after which a scramjet engine ignites to sustain hypersonic cruise using atmospheric oxygen for combustion. This air-breathing configuration eliminates the need to carry oxidizer, reducing mass and enabling longer range compared to purely rocket-powered systems. The scramjet operates by compressing incoming air at supersonic speed, mixing it with fuel, and maintaining combustion within milliseconds as airflow passes through the engine. This enables sustained flight at high velocity while allowing trajectory adjustments during flight.
Compared to boost-glide systems such as ARRW or the land-based Dark Eagle, which follow ballistic arcs before gliding, the HACM maintains powered flight throughout its trajectory. However, like the SR-71 Blackbird, this approach requires managing extreme thermal loads, with surface temperatures reaching levels that demand advanced heat-resistant materials and active cooling techniques. Combustion stability and fuel-air mixing at high speed also remain key engineering constraints. Development of the HACM has encountered measurable delays, including a shift in the critical design review from early 2024 to September 2024, which compressed the available testing window before planned fielding.
As a result, the number of flight tests prior to operational decision has been reduced to five, limiting the volume of empirical data available for validation. The program operates under a rapid prototyping framework with a target of fielding an initial capability by fiscal year 2027, despite the reduced test schedule. Cost growth has been recorded, with total development expenditure approaching $2 billion, reflecting increased complexity and manufacturing challenges. Industrial considerations include scaling production capacity and ensuring compatibility with multiple aircraft types, which requires extensive integration work. However, the presence of advanced U.S systems and personnel on Australian territory has generated domestic debate regarding transparency and sovereignty, particularly in the absence of detailed disclosures about testing activities.
Written by Jérôme Brahy
Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.
