It travels at more than five times the speed of sound, more than a mile per second, below U.S. missile defenses. It can carry conventional or nuclear weapons, able to reach anywhere in the world in three hours or less, and both China and Russia are developing them, as is the U.S.

The scary weapon of the near future is what's known as a hypersonic glide vehicle, sometimes called a "wave rider," because its aerodynamics allow the winged projectile to skip along the atmosphere, or glide on a smooth, flat trajectory after being launched via missile.

And the description most applied to them by U.S. military commanders is "game changer."

"Hypersonic glide vehicles are threats both Russia and China are building now," said Gen. John Hyten, head of U.S. Strategic Command, in recent testimony before the Senate. "They are very, very significant in terms of our ability to see them and provide warning."

Hyten, who oversees the U.S. nuclear arsenal and is responsible for providing the president with options in the event of nuclear war, is concerned about the ability of the unpowered gliders to deliver nuclear weapons, with little time for a considered response.

But since Russia already has an arsenal of nuclear-tipped ICBMs sufficient to obliterate the U.S., hypersonic gliders don't actually tip the "balance of terror," experts say.

"I would argue in the case of Russia, very long-range nuclear-armed gliders would actually just reinforce the status quo, would not create a new threat," said James Acton, senior fellow with the Carnegie Endowment for International Peace.

"As scary as that sounds, Russia already has the ability to annihilate the United States with nuclear weapons, and there is nothing we can do about that."

But non-nuclear hypersonic gliders could give adversaries such as China or Russia, who now don't match up well against America's high-tech military, a way to level the playing field.

Adm. Harry Harris, head of U.S. Pacific Command, also worries about the threat hypersonic weapons would pose to ships that might have only minutes to respond to a lightning-quick strike from an adversary.

"I'm concerned about Chinese and Russian hypersonic weapons development, and I expressed those concerns in the right places," Harris told Congress last month.

"What we can do is to develop our own hypersonic weapons and improve our defenses against theirs," Harris told a House subcommittee before cautioning that a more detailed discussion of the threat would require a closed session.

The U.S. is in fact developing not just hypersonic weapons but also systems to counter them.

The Trump administration, in its fiscal 2018 budget submission to Congress last month, requested $75 million for "hypersonic defense" as part of $7.9 billion overall funding plan for missile defenses.

But critics in Congress complain that's a mere $379 million over last year's request from former President Barack Obama and well below the annual $9 billion funding level planned by the Bush administration.

"These weapons present an entirely new capability we must counter as they are specifically designed to exploit the gaps and the seams in our existing missile defense architecture, thus defeating the systems we currently have in place," said Rep. Trent Franks, R-Ariz, on the floor of the House in March.

Franks, a member of the House Armed Services Committee, is concerned the threat from high-speed maneuvering weapons is figuratively flying below the radar.

"The threat has outpaced us," Franks said. "These new weapons are capable of traveling more than a mile per second and fly at flat or nonballistic trajectories to prevent our missile defense systems from tracking them."

So far most of the U.S. effort to develop a remarkably fast weapons platform has been in the research phase.

The Pentagon's Defense Advanced Research Projects Agency just green-lighted advanced design work for Boeing's XS-1 experimental space plane, which DARPA calls "an entirely new class of hypersonic aircraft that would bolster national security by providing short-notice, low-cost access to space."

Lockheed Martin's fabled Skunk Works is working on an unmanned version of the legendary SR-71 Blackbird, which would fly at speeds up to Mach 6, or six times the speed of sound, and could be operational by 2030 at a cost of about $1 billion, according to the company.

The idea is that the SR-72, dubbed "Son of Blackbird," would fly so fast that an adversary would have no time to react or hide.

"Hypersonic aircraft, coupled with hypersonic missiles, could penetrate denied airspace and strike at nearly any location across a continent in less than an hour," said Brad Leland, Lockheed Martin hypersonics program manager, in a promotional blurb on the company's website.

"Speed is the next aviation advancement to counter emerging threats in the next several decades. The technology would be a game changer in theater, similar to how stealth is changing the battle space today."

The Pentagon is also focused on countering that game-changing dynamic, and one possibility would be to meet incoming hypersonic missiles with a fusillade of outgoing hypersonic artillery, such as the U.S. Navy's electromagnetic rail gun, a Mach 6 cannon that the Navy claims can hit targets more than 100 miles away with pinpoint accuracy.

And when it comes to protecting ships at sea, naval forces already equipped with missile defenses may have an advantage because eventually any hypersonic weapon targeting the ship comes in range of defensive systems, said Bryan Clark, senior fellow with the Center for Strategic and Budgetary Assessments.

"The fact that the hypersonic weapon is going Mach 5 or beyond is somewhat mitigated by the fact that it has to eventually arrive at your location," Clark told a congressional committee in March.

"So, some of these missile defense capabilities that might be very difficult to use in defense of somebody else are somewhat effective when you're dealing with you getting shot at yourself," he said.

Still, Clark said, sometimes the best defense is a good offense.

"If we're worried about the threat coming from Russia or China, there's no reason why we wouldn't be able to develop our own hypersonic threat, whether it's air-launched or potentially even surface-launched, ship-launched," Clark said.

But Acton, who wrote Silver Bullet?, a 2013 book on hypersonic weapons, argues the threat is still at least a decade away.

"I would say where we are with gliders is about where we were with cyber weapons, 20 or 25 years ago, Acton said. "People were starting to understand there was a threat there, and it took the threat a while to emerge, but that threat did emerge and it became very significant."

Acton said cyber warfare will likely be a much bigger game changer for years to come.

"I very much doubt gliders will have as big implications for international security as cyber weapons, but it's at that stage where multiple countries are engaged in their development."