At about 3 a.m. Halloween morning, senior Pentagon officials gathered around television monitors to watch the live feed of a high-stakes, experimental weapon test—the launch from Hawaii of a hypersonic glide vehicle, a pointy contraption carrying the hopes of U.S. military leaders to beat China and Russia in the race to field a new class of ultra-fast missiles.

On screen was a three-stage rocket sitting on a launch pad at the Kauai Test Facility. It shot into the warm night, in its nosecone a one-of-a-kind, exquisite prototype weapon three years in the making.

Somewhere near the edge of the atmosphere, the booster separated and released the so-called “Advanced Hypersonic Weapon,” which then screamed for 3,800 kilometers at speeds at least five times the speed of sound—actual velocities and trajectory remain classified—to a military test range in the Marshall Islands.

Vice Adm. Terry Benedict, the Navy official overseeing the test, two days later publicly declared the event “very successful.”

Officially dubbed Flight Experiment-1, the test was a milestone achievement for a Pentagon technology development project in the works since 2008 with the aim of giving the president the option to hit high-value, time-sensitive targets anywhere in the world within an hour. It’s known as Conventional Prompt Strike.

One Test, $160 Million

The Halloween test was of a modified version of the Advanced Hypersonic Weapon (AHW) that successfully flew the same route in 2011 in the Conventional Prompt Strike program’s only other successful flight test to date.

The AHW is what’s called a boost-glide weapon. It’s shares some characteristics in common with a standard ballistic missile, which pierces the atmosphere and then flies a high arc through space before reentry. The AHW, on the other hand, separates from its rocket near space and then flies a flatter trajectory, gliding unpowered at speeds of at least Mach 5 to its destination.

The glide path should keep the AHW from being confused with a nuclear missile. But pushing the envelope of scientific achievement and carries technical risk and a hefty price tag.

For instance, the cost for the recent flight test was about $160 million. "These tests are very expensive," said Dyke Weatherington, principal director of space, strategic and intelligence systems in the Pentagon's acquisition directorate, which oversees the Conventional Prompt Strike program.

The land-based test was to assess a glider design scaled down to fit in a submarine launch tube. The two maritime candidate platforms, according to Benedict, are the small fleet of Ohio -class submarines armed only with conventional weapons and attack submarines the Navy will begin building in 2019 with vertical-launch silos.

“That's a monumental achievement,” Benedict, director of the Strategic Systems Programs office, said of the effort to shrink an original Army-designed hypersonic glider to fit in a sub.

Because of their speed—hypersonic weapons travel at least one mile per second—their maneuverability, and their low altitude, these fledgling new weapons promise to penetrate even the most sophisticated air- and missile defense systems.

Did China Leap Ahead?

The potential for delivering a game-changing capability is prompting a number of nations to pursue hypersonic technologies. The recent U.S. hypersonic success comes as China and Russia are, according to press reports and concerns of some in Congress, actively working to develop a similar ultra-fast weapon, conducting as many as three flight tests a year of the DF-FZ and 3K22 Tsirkon systems, respectively.

James Acton, senior fellow at the Carnegie Endowment for International Peace and expert in hypersonic weapons development, noted the U.S. has now twice demonstrated experimental hypersonic boost-glide payloads from Hawaii to the Reagan Test Site on Kwajalein Atoll in the Marshall Islands, a range significantly greater than the 2,100 kilometer distance China has reportedly been testing.

“So I remain skeptical of the 'China has leaped ahead of the U.S. in hypersonics' narrative,” Acton tweeted on Nov. 3.

The Conventional Prompt Strike program—which has cost $1 billion to date and seeks another $1.2 billion through 2022—is limited to research, development, testing and evaluation. At the urging of lawmakers impatient for the Defense Department to field a hypersonic strike capability as soon as possible, the Pentagon now plans in 2020 to make a formal decision to establish an acquisition program of record.

And last month, House and Senate lawmakers agreed to a new requirement for the program, that—if enacted in the 2018 defense policy bill—would establish a new objective: to field an “early operational” hypersonic strike capability by 2022.

For now, Pentagon officials say they’re encouraged.

"What I can tell you at this [unclassified] level is we matured a number of the technologies that have relevance in associating capabilities in what a warfighter might need in a future operational capability," Weatherington said in a Nov. 2 interview at the Pentagon.

"We are assessing the results of the test," he said. "Generally, I will say, we were mostly satisfied with the results." He declined to say how fast the glider traveled or anything about its trajectory, but noted the payload took less than 30 minutes to reach its target.

"The specific flight objectives are classified, and the department is assessing the data to discern if we met those flight objectives," Weatherington said.

In 2015, however, the Office of the Secretary of Defense previewed to lawmakers objectives for Flight Experiment-1, promising the test would include a first-ever live warhead integration on a hypersonic boost-glider, demonstrate flight control software improvements, higher G-loads while maneuvering, advanced avionics, miniaturization of subsystems and improved guidance algorithms.

Did the Defense Department integrate a warhead on the hypersonic glider in the Halloween test?

"I have no comment," Weatherington said.

Acton said assessing DOD's claims of test success requires knowing the goals, in particular—since the Pentagon aims to use non-nuclear warheads—accuracy against the test target. “You need accuracy on the order of a few meters,” Acton said.

80-Year-Old Promise

The promise of a hypersonic boost glide weapon dates back to the 1930s, when it was conceptualized by Eugen Sanger, an Austrian engineer, according to Acton. After World War II, both the United States and the Soviet Union invested in boost-glide program to explore the capability. Still, roughly 80 years later, no nation has yet deployed such a system.

“The long pole in the tent today is a heat-management challenge,” Acton said. “These gliders are designed to stay in the atmosphere for very long periods of time. And at those high speeds they are getting exceptionally hot from friction with the atmosphere. How you manage that heat is a huge challenge. It is in no small part a materials science challenge. You need materials capable of withstanding the heat, of not falling apart, of being light enough and something you can actually manufacture in the right shape to withstand the aerodynamic forces.”

Weathington declined to discuss thermal challenges associated with the AHW prototype flown last month. However, he said in general the boost-glide payloads DOD is exploring are designed to travel in the atmosphere for tens of minutes. “That's a long time to heat-soak a vehicle compared to a typical ballistic reentry vehicle, which, from the time it reenters the atmosphere and hits the ground, is 20 to 30 seconds,” the senior Pentagon official said. “The thermal protection system has to be much more complex. Assessing the performance of that thermal protection system is one of the sensitive areas of this program.”

In a sign the Pentagon has faith in its hypersonic glider design, the Conventional Prompt Strike program is now turning its attention to developing a new hypersonic booster that could be the workhorse of an operational system.

Can They Be Stopped?

While the Pentagon may be closing in on technologies for a potential offensive hypersonic weapon, it is in the early stages of sorting out the other half of the equation: how to defend against hypersonic threats.

In June, the Defense Intelligence Ballistic Missile Analysis Committee in collaboration with the Air Force's National Air and Space Intelligence Center for the first time identified hypersonic glide vehicles—being developed by Russia and China to penetrate U.S. ballistic missile defenses—as an “emerging threat.”

That followed an Air Force advisory panel commissioned to explore options for defending against hypersonic weapons, which last year concluded that no "silver bullets" were in the development pipeline to defeat this new class of threats. Instead, the panelists argued, the best defense may be a new offense: the U.S. military's own credible, hypersonic weapon.

Still, the Missile Defense Agency in May secured last-minute funding from Congress to immediately launch three classified projects to address the "emergency warfighting readiness requirement" of ensuring the Ballistic Missile Defense System can deal with hypersonic weapons. And in June the agency proposed a new Hypersonic Defense program, outlining a nearly $600 million, five-year plan to begin identifying technology solutions to counter these ultra-high-speed threats.