How Repurposed Global Hawks Will Hugely Accelerate Hypersonic Testing

Dozens of orphaned RQ-4s will become RangeHawks under the SkyRange program to create a massively flexible, high-tempo test range complex.

byEmma Helfrich|
SkyRange RQ-4 RangeHawk


In August of this year, it was finally confirmed that retired Block 20 and Block 30 RQ-4 Global Hawks belonging to the U.S. Air Force would be reconfigured as RangeHawks under the SkyRange hypersonic weapon testing infrastructure program. However, details regarding how exactly these modified RQ-4s were expected to work under the program remained limited. Now, with additional information from the U.S. Defense Department's Test and Resource Management Center, or TRMC, we have a deeper understanding of how exactly RangeHawk will perform, and, if it works as intended, it could usher in a new era of U.S. hypersonic development. 

The fate of decommissioned RQ-4 Global Hawks first began to come to light last year when Northrop Grumman announced that it would be repurposing four of the Air Force’s retired Block 20 high-flying intelligence-gathering drones to serve the Pentagon’s SkyRange program. The RQ-4s then made their way to the Grand Sky commercial testing facility across the runway from Grand Forks Air Force Base in North Dakota where they would be refitted with new electronics needed to achieve the SkyRange mission: using high and far-flying semi-autonomous unmanned aircraft to track hypersonic capabilities during flight tests over expansive distances. 

An image was released by the U.S. Air Force two years ago showing a NASA RQ-4 Global Hawk, U.S. civil registration code N874NA, after receiving modifications to support the Sky Range program. Credit: U.S. Air Force

“In support of the SkyRange initiative, Block 20 and 30 RQ-4B Global Hawk aircraft will be reconfigured into RangeHawks and provide high altitude, long endurance [HALE] airborne range services including collecting telemetry and monitoring the system-under-test during test flights,” said Brian Peck, director of the TRMC’s RQ-4 RangeHawk programs, to The War Zone. “Northrop Grumman will integrate advanced payloads to equip the RangeHawks with the capability to support the testing of hypersonic vehicles and other long-range weapons.”

SkyRange is one initiative among the ever-growing breadth and volume of U.S. military hypersonic programs, both classified and unclassified, as there are other, more sensitive initiatives being kept under wraps. Research and development efforts into hypersonic testing have been a point of investment at the Pentagon for years now, and the Defense Department just recently asked for about $5 billion for hypersonic system development in the Fiscal Year 2023 budget request. Even if that figure is to be approved by Congress later this fall, it wouldn’t change the complicated logistical aspects of hypersonic testing that have for so long now bogged down advancements in that area for the United States. In fact, it would exacerbate it.

Rendering on an X-51A Waverider hypersonic weapon. Powered by a Pratt & Whitney Rocketdyne SJY61 scramjet engine, it is designed to ride on its own shockwaves and accelerate to about Mach 6. Credit: U.S. Air Force

In short, SkyRange doesn't just give retired RQ-4s a second chance at life, it also provides the infrastructure that will help push the United States farther along in the global hypersonic race.

Up until now, the Defense Department had been restricted in the number and location of hypersonic tests it can carry out each year because of the aging fleet of ships it uses as its primary data collection assets to track the capabilities while in flight. Missile-tracking instrumentation ships like SS Pacific Tracker, MV Pacific Collector, and USAV Worthy are all among those that have been used.

The vessels are deployed to specific testing corridors in ocean waters below a hypersonic vehicle's flight trajectory, where the ships then track and record valuable flight test data using their intelligence-gathering sensors, including powerful radars. Each ship can be positioned under different points in the vehicle's flight path so that continuous or near-continuous monitoring of its flight can occur. Some can also be bunched close together to better observe certain phases of a test flight from different angles even using disparate sensors.

Only four to six hypersonic tests are allotted to the Defense Department each year due to the significant amount of time and resources that it takes to deploy and position the vessels across the Pacific Ocean. Not only that but even just sailing the ships can incur significant costs and potentially alert adversaries — with ample time to respond — to domestic hypersonic testing events. While manned aircraft, such as the Missile Defense Agency's Gulfstream business jets, specially equipped P-3 Orions, and NASA's WB-57, as well as ground-based sensors, have been helpful and supplementary assets during hypersonic tests, ships have nonetheless become a particularly limiting factor. 

That’s where the RangeHawks come in. 

A briefing slide showing the typical array of air, sea, and ground bases sensors used to collect data during the two tests of the Hypersonic Technology Vehicle 2 (HTV-2) in 2010 and 2011, respectively. Credit: U.S. Air Force

“As an unmanned system, RangeHawks will be able to get much closer to the [hypersonic] system under test, flying within the flight safety evacuation areas (where manned systems are not permitted during the test flights),” said George Rumford, acting director and principal deputy for the TRMC, to The War Zone. “Being closer to the actual flight path enables RangeHawks to collect significantly higher quality data than traditional test support ships. Compared to ships, the primary data collection assets supporting long-range flight tests today, RangeHawks will also enable shorter turnaround times between tests.”

“It’s the combination of range, endurance, and advanced payload capacity that makes RangeHawk the most suitable uncrewed aircraft to support testing the emerging class of hypersonic weapons,” Peck said. “RangeHawk provides persistent time-on-station closer to the flight path of the system under test and the agility to adapt to the dynamics of a testing environment.” 

A briefing slide from 2018 showing various efforts the Air Force was conducting at the time to improve hypersonic flight test capabilities. Credit: U.S. Air Force

The RQ-4 Global Hawk was a logical choice to become the future RangeHawk not only because of retirement timelines but also considering each system’s current capabilities. Block 20 RQ-4s were originally fielded only as imagery intelligence (IMINT) platforms, but four were later converted into communications relay platforms, referred to as EQ-4s, that feature a Battlefield Airborne Communication Node (BACN) payload. These are the four Block 20 Global Hawks that Northrop Grumman first began retrofitting for SkyRange last year. All Block 30 RQ-4s were fielded as multi-intelligence platforms carrying electro-optical/infrared (EO/IR), synthetic aperture radar (SAR), and high- and low-band signal intelligence (SIGINT) sensors.

A Block 30/40 RQ-4 offers a maximum take-off weight of 32,250 pounds, part of which is made up of the 17,300 pounds of fuel it can carry and the 3,000-pound payload capacity that it also boasts. The RQ-4 can fly at a speed of up to 310 knots and reach a staggering range of 12,300 nautical miles. On top of that, the drone can fly for over 34 hours and reach a lofty flight ceiling of 60,000 feet. While the Global Hawks will certainly be receiving new technologies throughout their transformations into RangeHawks, it isn’t clear if the RQ-4’s original performance specifications will be affected negatively, positively, or at all as a result of the conversion process.

An RQ-4 Global Hawk soars through the sky to record intelligence, surveillance, and reconnaissance data. Credit: U.S. Air Force

Reconfiguring the retired RQ-4s with the necessary sensors and avionics for their new RangeHawk role will be achieved through a partnership between the TRMC and Northrop Grumman, the latter of which manufactured the Global Hawk system. The TRMC and Northrop Grumman together have previous experience in modifying retired RQ-4s to be used in scientific and flight test research, as both have already been working alongside NASA for years using one Block 2 and two Block 10 RQ-4s.

The overarching goal is for RangeHawks to offer a far more flexible and quickly adaptable tracking option for hypersonic tests, especially long-range ones where tracking would be needed across several hundreds of miles. Leveraging the RQ-4's high-altitude loitering abilities and long line-of-sight, RangeHawks can be spaced out over these vast distances while still maintaining continuous tracking of the test asset.

NASA’s Global Hawk being prepared at Armstrong to monitor and take scientific measurements of Hurricane Matthew in 2016.
Credit: NASA photo by Lauren Hughes

“RangeHawks will be positioned at key waypoints underneath the planned flight path of a hypersonic system to collect performance data,” said Rumford. “The number of RangeHawks in the air to support a test event depends on the test complexity and data collection requirements. The primary sensors will be telemetry collectors establishing a data link with the hypersonic system in flight.”

An X-43A hypersonic research aircraft and its modified Pegasus booster rocket accelerate after launch from NASA's B-52B launch aircraft over the Pacific Ocean. Credit: NASA photo by Carla Thomas

In terms of where RangeHawks will be kept, it is clear that all Block 20 and Block 30 RQ-4s will at the very least be housed at the Grand Sky facility per an announcement released by Sen. John Hoeven’s (R-N.D.) office, which has been working directly with the Air Force to solidify North Dakota’s relationship with the SkyRange program. However, current reports dictate that the TRMC is still only working with the four Block 20 RQ-4s that were ordered last year even though it has already received the transfer of all 20 Block 30 types. 

Rumford did confirm to The War Zone that Grand Sky will be home base for the RangeHawks and revealed that building additional facilities to augment the existing ones is “under consideration.” He also added that “all twenty Block 30 Global Hawks will be retrofitted into RangeHawks for test mission support.”

Entrance to the Grand Sky testing facility in North Dakota where all retired Block 20 and Block 30 RQ-4 Global Hawks will be housed. Credit: Grand Sky

It is unclear how many Block 20 RQ-4s beyond the four that have already been retrofitted will have new life breathed into them as RangeHawks, but Peck noted that “planning is underway for reconfiguring former RQ-4B Global Hawks into RangeHawks, and we do not yet have details about future operations and the final operational fleet size.” It's also possible some of the Block 20s will be used as spare part donors for the active RangeHawk aircraft.

In a photo released by Northrop Grumman taken during an event at Grand Sky, which is included below, a presentation board can be seen to the right of the podium that clearly states “24 aircraft [are] to become RangeHawks.” If SkyRange has already reconfigured four Block 20 RQ-4s into RangeHawks and plans to do the same with all 20 Block 30 RQ-4s, then the graphic would suggest that no additional Block 20 types will be undergoing the RangeHawk transformation. Although, that board could have been designed solely for event optics considering that it conflicts with Peck's uncertainty about the final fleet size.

U.S. Sen. John Hoeven (R-N.D.) welcomes the TRMC to the Grand Sky testing facility in North Dakota. A RangeHawk can be seen in the background. Credit: Northrop Grumman

Even though Grand Sky will act as RangeHawk headquarters, Rumford said that “the RangeHawks will be deployed everywhere we need additional test data collection capabilities, predominantly over the Pacific Ocean and the Atlantic Ocean.” This means that the RangeHawks could self-deploy to key areas on a single round-trip flight, or they could travel to forward-operating locations closer to where hypersonic tests are being held, which would allow for far greater hypersonic testing agility compared to the program’s current dependence on ships.

Retired Global Hawks lining the ramp at Grand Sky. The Grand Sky facility is attached to the runway at Grand Forks AFB but is used by contractors for taking advantage of the unique airspace set aside for unmanned operations in the region. PHOTO © 2022 PLANET LABS INC. ALL RIGHTS RESERVED. REPRINTED BY PERMISSION

When speaking to the defense news outlet C4ISRNet in a recent interview, Rumford explained that it can take 21 days for a ship to be positioned and outfitted for a hypersonic flight test. In comparison, he said that a RangeHawk could be ready in just hours. 

"That means if they want to test in the Pacific, we can go test in the Pacific. If they want to test in the Atlantic, we can test in the Atlantic,” Rumford said to C4ISRNet. “We can go to where they need to go, which is very different than where it is today …  You can’t just reposition a bunch of ships from the Pacific over to the Atlantic in a timely fashion."

With the flexibility that RangeHawks are projected to provide, Rumford also told C4ISRNet that he hopes to develop a hypersonic testing infrastructure that would support one demonstration per week. He explained that SkyRange is aiming to one day reach a quota of 50 tests a year. While that is certainly an ambitious metric compared to the current state of hypersonic testing in the United States, properly modified RQ-4s have the potential to make it a reality.

The four retired Air Force Block 20 Global Hawks that Northrop Grumman retrofitted for the SkyRange program. Credit: Northrop Grumman

According to C4ISRNet, Northrop Grumman and the TRMC are hoping to have the first batch of RangeHawks reconfigured and ready for testing sometime in 2024, and both entities are reportedly in negotiations about how many that initial lot will consist of. Rumford mentioned to the outlet that the retrofitting process takes several months for just a singular RQ-4 to become a RangeHawk, primarily because it requires a full system overhaul to ensure that its installed sensors and data links are capable of looking up in the direction of the hypersonic vehicle's flight path.

"This involves repositioning onboard avionics and installing new sensors and instrumentation suites that can track a hypersonic vehicle flying overhead," read the C4ISRNet article. "Rumford noted that TRMC has a separate contract with instrumentation providers to perform those installations."

The SkyRange program is apparently also keeping a close eye on the Air Force’s plans to retire its younger Block 40 RQ-4s in 2027. If that transfer is to be successful, the RangeHawk fleet could increase by nine. Even the Air Force’s retired MQ-9 Reapers are on the TRMC’s watchlist, which has been on the table since at least 2019 and lines up with the Air Force’s desires to scale back its MQ-9 operations in recent years.

The Air Force is still looking to halt purchases of MQ-9 Reaper drones and is seeking to transfer 100 of its some 300 existing examples to "another government organization" that it would not disclose. Rumford told C4ISRNet that the TRMC is now in talks with General Atomics, who builds the MQ-9, about the ways in which the system could be reconfigured to best serve SkyRange’s mission, but it’s unclear if those discussions are related to the Air Force’s MQ-9 plans.

An MQ-9 Reaper sits on the 361 Expeditionary Attack Squadron flightline at an undisclosed location, Aug. 6, 2022. Credit: U.S. Air Force photo by Tech. Sgt. Jim Bentley

In one of the most recent developments for the program, Stratolaunch, which owns the giant Roc aircraft and is now specializing in testing high-speed aircraft technologies, announced that it would be partnering with SkyRange to "demonstrate capability of its airborne test assets by tracking the first Talon-A hypersonic flight." Talon-A, which you can read about in detail in this past War Zone feature, is the company's reusable unmanned hypersonic test vehicle that is designed with modular payload spaces meant to support the intended flight demonstration activities.

The planned test, which Stratolaunch says will be the first for Talon-A, doesn't yet have an assigned date but is being advertised as a way to showcase how both SkyRange systems and the Talon-A vehicle will work under evaluative conditions. Carried by the Roc mothership, Talon can also forward deploy to different areas and fly out to remote launch locations, making it a uniquely attractive pairing with SkyRange.

Rendering of Stratolaunch's Roc launching Talon. Credit: Stratolaunch
Stratolaunch's Talon-A separation test vehicle, TA-0, mated to Roc carrier aircraft for the first time. Credit: Stratolaunch

SkyRange is also in the process of studying how satellites could be used to help ameliorate the lack of hypersonic testing infrastructure in the United States, and Rumford told C4ISRNet that the TRMC will be working with the Space Development Agency over the next few years to prototype this concept. He noted that he hopes to have a satellite support strategy developed by 2025. This capability would likely be a secondary benefit to the new remote sensing layers that Space Force will be deploying to track hypersonic threats operationally. Using those same cutting-edge orbital sensors to help with hypersonic testing would also help sharpen and validate their own capabilities. You can read a complete explainer on how this tracking constellation will work in this past War Zone feature.

In 2020, the Space Development Agency awarded L3Harris and SpaceX a $342 million contract to build out Tranche 0 of a missile tracking layer for the National Defense Space Architecture. Credit: Defense Department

All told, the possibilities for the RangeHawks and the SkyRange concept they will support is exciting and the entire enterprise could grow larger and more capable over time. These could include extending into a broader realm of flight tests, as well. Rumford said that “the driving requirement for RangeHawks is hypersonic test support, but the unmanned platform and sensor technology is capable of supporting long-range test events requiring additional test data collection for the Department and other Government agencies.”

Regardless, SkyRange may not be the 'sexiest' element of the rapidly evolving U.S. hypersonic ecosystem, but it could very well turn out to be one of the most critical.

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