For the first time in decades, it seems the US may be falling behind its competitors in an increasingly important new arms race: the rush to develop hypersonic missiles.
As Russia continues to wage war in Ukraine, and tensions flare between China and Taiwan, experts say this new generation of weaponry could leave the US and its allies exposed.
"Basically, if somebody fired hypersonic weapons at the West today, we wouldn't know until it's too late that these weapons were on top of us," says University of Colorado Boulder's professor of aerospace engineering Iain Boyd.
The term hypersonic refers to a missile that travels at least five times the speed of sound, or around 5,600 kilometres per hour.
But professor Boyd told ABC News Daily it's not the speed of these new missiles alone that makes them dangerous.
In fact, the technology to fire weapons at hypersonic speeds has been around since the 1950s, and intercontinental ballistic missiles, which are capable of speeds of up to 24,000 kilometres per hour, have been in military arsenals for decades.
What makes the new generation of hypersonic missiles so valuable, Professor Boyd says, is their ability to manoeuvre and avoid detection.
"The old hypersonic systems that are still around, they're a little bit easier to defend against because the path that they follow is relatively easy to understand," he said.
"These new systems, they are what we call manoeuvrable.
"They can go from side to side, they can go up and down, and this makes it much more difficult to predict where they're going to go."
But not all experts believe the promise of hypersonic missiles will live up to reality.
"They fly high in the atmosphere, but they go in a different area where we are not used to looking. They're completely new to everybody and that's part of the challenge they present.”
Senior fellow at the Australian Strategic Policy Institute, Andrew Davies, says the missiles are harder to defend against, although he thinks they're being "over-hyped".
He believes the ability to change a missile's course mid-flight is limited.
"They can't manoeuvre abruptly, because at very high speeds you're limited to what sorts of movement you can do. It does complicate the job of the defence, though, which is an advantage."
Who's winning the global race?
While several countries including India, Australia, Japan, France and North Korea are investing in the technology, the main race for hypersonic capabilities is between superpowers: Russia, China and the United States.
In March this year, Russia claimed it had achieved a major milestone by launching two hypersonic Kinzhal missiles against Ukraine.
But experts are sceptical about exactly how significant its use was, with Professor Boyd explaining the missiles used are "relatively unsophisticated" old-generation hypersonic weapons.
"They're just a missile with a rocket on the back that made them go very fast," he said.
"They're still relying on where they were at the end of the Cold War. They haven't really advanced a lot."
A greater concern for the West, Professor Boyd says, is China, which he believes already has combat-ready next-generation hypersonic missiles.
Last year, it was reported China tested a nuclear-capable hypersonic missile that flew around the earth before speeding towards and hitting its target.
“If they were really able to hit their target with some accuracy that is quite impressive," Professor Boyd said pointing out the test may have been "posturing" by Beijing.
"So I think that China is really the international force to be reckoned with right now in terms of hypersonics.
"The US and none of the Western allies have that capability today, although there's a lot of efforts underway to get to that point."
The United States has a multi-billion-dollar hypersonic research program that successfully tested two Lockheed Martin missiles in late July.
But officials have said the missiles won't be operational until next year.
Despite this, ASPI's senior fellow Dr Andrew Davies believes the US is still ahead of China and Russia in the hypersonic race in one important class of hypersonics known as "air-breathing" missiles.
"Air-breathing missiles are even more manoeuvrable because they're operating within the atmosphere," he said.
"This would give the US a much more strategic advantage over other currently available hypersonic missiles."
Australia has also been working on hypersonic missiles and, with its recently developed AUKUS partnership with the US and UK, Dr Andrews believes should be well placed to adopt the technology.
"It potentially gives us the ability for medium and long-range strike which we haven't had in more than a decade, since the retirement of the F-111 fighters," he said.
How could they be used?
A potential conflict between China and the US over Taiwan is one situation where Professor Boyd says hypersonic missiles could offer a distinct advantage.
"If a hypersonic weapon — because it couldn't be defended against — could disable an aircraft carrier, that would have a very big impact in that very specific scenario," he said.
But China's ability to launch attacks against US aircraft carriers could actually reduce America's willingness to engage in that conflict.
"If the US Navy knew that their aircraft carriers were vulnerable to these hypersonic weapons, then they're unlikely to sail their aircraft carriers into an area right where they're vulnerable," he said.
"So China, in that situation, achieves this goal by not even firing any missiles."
How prepared should we be?
Professor Boyd points out that hypersonic weapons are "not the silver bullet that wins every single war" for any country that possesses them.
"They have very specific situations where they're tremendously valuable, but they're not like the atomic bombs in World War II where whoever got their bomb to go first was going to win the war," he said.
But he believes the ability of the missiles to carry nuclear weapons is definitely a concern.
"If you're sitting in the US and this hypersonic weapon gets fired from Russia and you've been told it could be either nuclear or non-nuclear, then what's your reaction?" he said.
"There's that kind of unsettling, destabilising element of where we are today with hypersonic weapons."
But Professor Boyd says he is less concerned about China using nuclear hypersonic weapons against the United States or its allies like Australia.
"You know, Russia is obviously a lot more unstable, so I think that is the area to be worried about," he says
"I guess I just hope that we don't get into a situation where Russia, or President (Vladimir) Putin, feels pushed into a corner and they have nothing to lose."
