DARPA’s Common Aero Vehicle and submunitions, circa late 1990s. (Image: discontinued National Security Space Roadmap website)

WASHINGTON: The ongoing drips and drabs of unclear information leaking from the Pentagon about this summer’s Chinese hypersonic test are raising red flags for physicists and experts, who are questioning whether claims about the results of the test stand up to scrutiny.

The new detail regarding a possible launch or simple release of either a missile or some kind of countermeasure over the South China Sea was first reported on Sunday by the Financial Times (FT), which was the outlet that also originally reported on the launch. This most recent claim, if accurate, would represent a leap in capability — and one that firmly remains in the future concepts basket at the Pentagon.

“From a general standpoint, deploying something at hypersonic speeds, is really, really, really, really hard,” said Mark Lewis, executive director of the National Defense Industrial Association’s Emerging Technologies Institute and an expert on hypersonics. “And if anyone were to do that, that would be super impressive.”

But the “if” in that statement is doing a lot of heavy lifting, and given the lack of publicly available data, it’s unclear exactly when, or if, clarity will truly emerge.

Question One: Is It Possible? 

The basic question at hand with regard to the new report is: could China have successfully launched a submunition from a hypersonic glide vehicle (HGV) while it was screaming through the atmosphere at Mach 5-plus? And the answer is, perhaps.

There is a historical analog, of sorts. Two decades ago DARPA worked on a project [PDF]  known as the Common Aero Vehicle (CAV), which included a suborbital, hypersonic glide vehicle (HGV) that could deliver conventional weapons anywhere in the world within two hours.

DARPA could never get the system to work right, however, due to a number of design problems that ran into the laws of physics, Lewis said. The effort was eventually killed in 2004 by Congress, less due to its technological problems and more out of political concerns that it was strategically destabilizing.

One key issue for deploying submunitions from HGVs is that when two vehicles are moving at above Mach 1, several scientists explained, the two objects create shock waves that can interfere and cause the submunition to bounce back into its parent vehicle, destroying both.

This actually happened, according to the Global Security website, in a 1966 test of an air-breathing drone, called the D-21 Tagboard, launched from a supersonic jet (the precursor of the SR-71). The test resulted in a crash that killed one of the jet pilots and caused legendary Lockheed Martin engineer Kelly Johnson to terminate the program.

To avoid that problem, the CAV was designed to dramatically slow down. And, it is possible that this is exactly what the Chinese HGV did too, several scientists said.

“A vehicle like a CAV would lose speed as it glided at low altitudes since it is not powered. You could imagine having the [Chinese] payload be a smaller vehicle that did carry propellant so that it would gain speed and be going fast enough to out-maneuver defenses. It might be released when the CAV had slowed to non-hypersonic speeds,” explained David Wright, a theoretical condensed matter physicist affiliated with MIT’s Laboratory for Nuclear Security and Policy, in an email.

And it is possible to overcome the shock wave problem, said one industry expert in the field, and the US actually has data on this so-called wake effect from its years of experience with the Space Shuttle.

“A hypersonic object interacting with the rarified atmosphere creates an area of low pressure directly adjacent to the hull of the object,” the industry expert said. “Clever design of surfaces could create an area of low pressure large enough for a submunition to be deployed away from the primary vehicle.” Such a system would have “a low probability of recontact.”

Question Two: Is It Likely?

So, it may be technically possible to do what the FT reported China accomplished. But did it happen? Many experts are skeptical, both due to the technological concerns and confusion about the details.

Part of the problem for public domain analysts is that the Defense Department continues to be vague about what the US government knows regarding the test, except to frantically ring the alarm bells about China moving ahead of the US on hypersonic weapons research. And when they do speak, they seem to hint at something other than what was described this week.

For instance, in a Nov. 16 interview with CBS just prior to his retirement as vice chief of the Joint Chiefs of Staff, Gen. John Hyten seemed to confirm that the July 27 test instead involved — as Air Force Secretary Frank Kendall suggested in August — a Fractional Bombardment System (FOBS). FOBS was a Soviet-era orbital system that carried nuclear weapons; the twist with the Chinese system is that it carries a hypersonic glide vehicle (HGV).

While of some concern, such a hybrid FOBS-HGV system wouldn’t represent a major scientific breakthrough, nor would it create any more challenges for US missile defense systems than they already have with countering Russia’s giant arsenal or even China’s (currently) much smaller one.

“They launched a long-range missile,” Hyten told CBS. “It went around the world, dropped off a hypersonic glide vehicle that glided all the way back to China, that impacted a target in China.” When pressed on whether the HGV hit the target, Hyten responded: “Close enough.”

In response to a request for comment following the FT report, a Space Force spokesperson said: “Everything we have on that event was relayed by Gen. Hyten on CBS before he retired.”

Another insider also pointed to Hyten’s interview, saying that the FT report was “confused.” The source noted that “unless there was a major new development in the last few weeks,” the report of a submunition is almost certainly “wrong.”

That thread has been picked up by a number of outside technical experts, who point out the FT reports have used technical terms meaning different things somewhat interchangeably.

“Last week they described this more like a hypersonic missile. The story keeps changing,” Jessica West, of Canada’s Project Ploughshares, said in an email. “We really need to have better access to orbital data. The he-said, she-said merry go round is not productive when it comes to monitoring potentially dangerous activities in space.”

For example, Sunday’s FT report stated: “Pentagon scientists were caught off guard by the advance, which allowed the hypersonic glide vehicle, a manoeuvrable spacecraft that can carry a nuclear warhead, to fire a separate missile mid-flight in the atmosphere over the South China Sea, according to people familiar with the intelligence.” Further, the report quoted DARPA scientists as “unsure” how Chinese scientists managed to deploy the “countermeasure” from a vehicle moving at hypersonic speed.

First of all, a countermeasure isn’t a missile and that difference matters.

Further, an HGV usually refers to a vehicle that doesn’t actually go into orbit, but barely breaks the outer atmosphere before gliding back down and using its wings to maneuver as it moves. Some HGVs actually skip along the boundary between the atmosphere and space to maintain momentum, but do not actually achieve a full orbit — just as an intercontinental ballistic missile or a FOBS does not achieve a full orbit.

A spaceplane on the other hand — such as the US Space Shuttle of the X-37B, and what the Chinese Foreign Ministry claims was tested rather than a weapon system — goes up on a rocket booster and then hangs out in orbit for a while before using thrusters to re-enter the atmosphere. Spaceplanes are blunt nosed to help slow them down as they glide down to a runway for a soft landing, Lewis explained. By contrast, most HGVs are designed with sharp nose cones to reduce drag, he said.

“I haven’t been able to figure out whether they were trying to land on a runway or not. If it was supposed to land on a runway and missed, then it looks like a reusable space vehicle—no reason to land gently then detonate a nuclear weapon,” said Laura Grego, an astrophysicist at MIT. “If the glider itself is supposed to be a conventional weapon, it would be trying to hit the ground hard, and either way, in a conflict these will be one-way trips.”

On the other hand, if the HGV crash-landed by mistake, “I think it could go either way, since they may have been primarily testing the maneuvering part of the system and they still could work on the landing gently part,” Grego said in an email.

Victoria Samson, head of Secure World Foundation’s Washington Office, noted that there are a lot of questions about public reports regarding the Chinese test, noting that “calling it ‘breaking the laws of physics’ does not lead to rational scrutiny.”

Both Grego and Samson noted that while US officials keep saying that the HGV is nuclear capable, the Pentagon has released no information on how officials have determined that. Samson — whose organization publishes an annual study on Global Counterspace Capabilities —  further stressed that up to now, China is known only to have been testing a conventional HGV, the DF-ZF.

Wright added that there is some reason to be concerned that part of the issue also is that those worried about the lack of progress and investment by DoD in hypersonic weapons are hyping both Russian and Chinese progress as a way to spur more funding. (This phenomena is not without historical precedent, as well known by anyone old enough to have read a version of the Pentagon’s now defunct Soviet Military Power brochure.)

“I have been told by others following the debate on these issues that those in the US who want to pursue hypersonic weapons have been really playing up the Russian and Chinese ‘lead’ in the field as a motivating factor,” he said. “The Pentagon may have been surprised that China would conduct a test like this (although China has been open about trying to counter US defenses), but it could not have been surprised about the technology it used.”