Artist's rendering of a hypersonic air-breathing missile.

Artist's rendering of a hypersonic air-breathing missile. DARPA

Hypersonics Test Shows the US Is Catching Up in the New Missile Race

But questions remain about costs and priorities remain.

Last week’s successful demonstration of a hypersonic glide vehicle is a “step in the right direction” in closing the research and testing gap between the United States and rivals Russia and China, a top Air Force technologist said this week. But the United States still has ground to cover in deploying highly maneuverable hypersonic weapons and defenses against them, Brig. Gen. John M. Olson, the Mobilization Assistant to the Chief of Space Operations and the Air Force’s acting Chief Technology and Innovation officer, told Defense One during a State of the Air Force panel on Tuesday.

Last week, Olson’s service and the Defense Advanced Research Projects Agency conducted a free flight test of its Hypersonic Air-breathing Weapon Concept, or HAWC, which dropped from a jet and lit off its supersonic combustion ramjet. 

“The engine compressed incoming air mixed with its hydrocarbon fuel and began igniting that fast-moving airflow mixture, propelling the cruiser at a speed greater than Mach 5 (five times the speed of sound,” DARPA said in a statement this week

“As a nation, we’ve taken a substantive early lead and turned that into a national effort to get back caught up and drive forward across the industrial base and the services,” Olson said, referring to the rapid progress China and Russia have made in deploying highly maneuverable hypersonic weapons. “From the perspective of proliferation, the Chinese and the Russians both have invested significant amounts and made significant progress in this arena.” 

This week’s test shows why “it's important that we continue to drive forward rapid learning, continue to build the industrial base strength,” he said.

The Army and Navy have their own high-priority hypersonic-weapons efforts. But an arguably larger challenge is defending against such weapons, which unlike conventional ICBMs, can shift trajectory in flight. 

The Pentagon’s Space Development Agency, or SDA, is rushing to launch a constellation of low-earth-orbit satellites that will use infrared beams and other means to track advanced missiles as they dodge and weave through the atmosphere. In August, a supply flight carried instruments to the International Space Station that will soon allow the agency to test new infrared imagery gear for these satellites, whose first designs were approved this month and whose launches are to begin in 2023.

But not all defense watchers believe the Pentagon’s hypersonics fixation is appropriate. “Hypersonics have been a bit overhyped thus far,” Stacie Pettyjohn, who directs the Defense Program at the Center for a New American Security, said atTuesday’s event.

Pettyjohn noted  Air Force Secretary Frank Kendall’s  statement that his service still needs to figure out what exactly it wants to do with hypersonics. 

“I haven’t seen different ideas for how they make a significant difference for the operational concepts thrown about for a potential conflict against China or Russia,” said Pettyjohn. “There seems to be a little bit of a sense that ‘China and Russia are developing them, so we have to catch up’.” 

She called that the wrong approach. “The U.S. has finite resources and we don’t need to match them missile for missile and capability for capability,” she said.

China and Russia are more likely to rely on asymmetric approaches against the United States: cyber operations or even conventional ballistic missiles against which the United States also lacks a good defense. 

“I’m not sold that the hypersonics race is the area where we should be putting most of our resources,” she said.  

From Missile Tracking to Space Clouds

Missile tracking is not all that those satellites will do. They could serve as a sort of mesh-network computer cloud in space. Derek Tourner, the Director of SDA, on Monday’s State of the Space Force panel said that the agency will be able to conduct experiments on actual data processing in space as part of a partnership with DARPA and the agency’s “Pit Boss” program, which seeks to outfit satellites with a unique “battle management” computer.  That experimentation will begin in 52 weeks, with the launch of the Agency’s tranche zero satellite layer. 

As Tourner explained, satellites are highly constrained in how much processing can take place aboard the satellite and that’s especially true as satellites become smaller. 

In space, he said, you are “limited by the amount of power you can collect from the sun and that’s going to drive your mass... that sets a limit on how much power you can have. Satellites we are looking at are all around 3 to 4 hundred kilogram class,” he said. There’s also the question of where to put the excess heat from the computational process, and no, you can’t just use a fan, like you have on your laptop, to push it into the vacuum of space. “You have to put big thermal radiators and wait for radiation to take the heat away,” that process takes a long time. 

In short, processing in space is very inefficient compared to ground-based processing. But if you can figure out how to do it, it has advantages, especially in terms of collecting and disseminating critical data and information faster. “You’re no longer reliant on any special nodes on the ground, not reliant on any ground communication that's a vulnerability and you are able to do all of that in space in near real-time as quickly as possible,” said Tourner.

The good news is that the hardware constraints you face in space are partially made up by the ease of instantaneous high-bandwidth data transfer using laser-based communication, also called optical crosslinks. “That allows you to overcome those physical limits with dumping heat and the amount of power because you spread that out,” he said. 

It’s a matter of tasking some satellites with watching and communicating and then using laser-based communication to send the data to other satellites that are part of the constellation to do that processing work. “Not all those satellites will be involved in your communication at any time. The satellites on the other side of the globe aren’t as involved can be more involved in the processing.” 

Said Tourner, computing processing will always be more efficient on the ground but “will you be able to do good enough processing? I think the answer is yes.”