The U.S. Air Force agency that manages the service’s nuclear arsenal has started research on enabling technology for an intercontinental-range hypersonic glide vehicle, according to a document that was briefly published in error on a public website.
Although the document shows that a U.S. nuclear weapons agency is researching hypersonic glide vehicle (HGV) technology, senior Defense Department officials say there has been no change to a policy that “strictly” limits the emerging class of hypersonic gliders and cruise missiles to non-nuclear warheads.
- The Pentagon remains committed to non-nuclear role for hypersonics
- The Air Force removed the document from a public website
A request for information (RFI) published on Aug. 12 by the Air Force Nuclear Weapons Center asks companies to submit ideas across seven categories of potential upgrades for ICBMs designed with a “modular open architecture.” The Air Force often describes the future Ground-Based Strategic Deterrent (GBSD) ICBM as featuring a “modular systems architecture,” in contrast with the aging Minuteman III, which does not.
Among the seven items on the upgrade list, the Air Force called for a new “thermal protection system that can support [a] hypersonic glide to ICBM ranges,” according to the RFI, which is no longer publicly available on the government’s procurement website.
The RFI may have disclosed information that the Air Force’s nuclear weapons buyers had not intended to be made public.
Each of the seven items listed in the RFI’s “scope of effort” for ICBM upgrades included a prefix designation of “U/FOUO,” a military marking for information that is unclassified but for official use only. Although not technically a classified secret, information marked as “FOUO” is usually withheld from the general public. The RFI was removed from Beta.sam.gov on Aug. 17 after Aviation Week inquired about the document with the Air Force and the Office of the Secretary of Defense.
The Defense Department has three different operational prototypes for HGVs in development now: the Air Force’s AGM-183A Air-Launched Rapid Response Weapon, the Army’s Long-Range Hypersonic Weapon and the Navy’s Intermediate-Range Conventional Prompt Strike. Once fired from an aircraft, a ground-launcher or submarine, all three are designed to strike targets with conventional warheads at intermediate range, which is defined as 1,500-3,000 nm by The Department of Defense Dictionary of Military and Associated Terms.
But the Pentagon has no acknowledged plan to develop an HGV with a range beyond 3,000 nm and maintains a policy that “strictly” prohibits arming any such weapon—regardless of range—with nuclear warheads. The two most senior staffers leading the hypersonic weapons portfolio reiterated that policy during a press conference on March 2.
“Our entire hypersonic portfolio is based on delivering conventional warheads,” said Mike White, assistant director of defense research and engineering for hypersonic weapons.
“Right,” agreed Mark Lewis, the director of defense research and engineering for modernization programs. “Strictly conventional.”
The Pentagon has not changed the policy since March 2, said Lt. Col. Robert Carver, a spokesman for Lewis’ office.
“[The Defense Department] is not developing nuclear-capable hypersonic weapons,” Carver wrote in an email. “There are common technology needs between the nuclear enterprise and hypersonic systems. Particularly in the area of high-temperature materials, we typically collaborate on the development of advanced dual-use materials technology. I will reiterate that our entire hypersonic program portfolio continues to be based on delivering conventional effects only.”
The threshold requirements for the initial version of the GBSD entering service in 2030 do not include an HGV for the reentry system, said Lt. Gen. Richard Clark, the Air Force’s deputy chief of staff for strategic deterrence and nuclear integration. However, Clark, who spoke during an Aug. 19 webinar hosted by the Mitchell Institute, noted that the GBSD is designed with a flexible architecture, allowing future variants to add new capabilities easily.
“GBSD does have an open architecture,” Clark said. “It gives us an ability to incorporate emerging technologies or technologies we need to counter whatever threats we face in the future. If we decide down the road that there’s a particular technology that needs to be incorporated, we will be able to do that.”
Although the Pentagon upholds the conventional-only policy for hypersonic gliders and scramjet-powered cruise missiles, the source of the RFI raises questions, says James Acton, co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace.
“The fact that [this RFI] is coming from the Nuclear Weapons Center, it makes it sound an awful lot like this would at least be nuclear-armed or conceivably dual-capable,” says Acton.
Although the RFI confirms research is underway, the Defense Department still has no acknowledged plans to proceed from basic research into the acquisition phase of an ICBM-range hypersonic glider, whether carrying a conventional or nuclear warhead. If the thermal-protection system technology is limited only to research, the RFI by the Air Force’s nuclear weapons organization may not violate the Pentagon’s policy, which may apply only to fielded weapons.
“[The Defense Department] does a lot of research on a lot of different things, and the vast majority of these programs never turns into an acquisition,” says Acton. “It could turn into something, but sophisticated observers recognize that it may not.”
The Pentagon’s conventional-only policy for maneuvering hypersonic weapons stands apart from other countries in the field. Russia, for example, has deployed the nuclear-armed Avangard HGV on the SS-19 ICBM. In February, the head of U.S. Northern Command, Gen. Terrence O’Shaughnessy, said in written testimony submitted to Congress that “China is testing a [nuclear-armed] intercontinental-range hypersonic glide vehicle, which is designed to fly at high speeds and low altitudes, complicating our ability to provide precise warning.”
The Pentagon has never had an announced weapons development program for a conventional- or nuclear-armed intercontinental-range HGV but has experimented with air-launched gliders. DARPA’s Hypersonic Test Vehicle 2 program attempted to demonstrate a range of 4,170 nm, but each experimental glider in two tests staged in 2010 and 2011 failed about 9 min. into a planned 30-min. hypersonic glide.
The leading edges of an intercontinental-range HGV could be exposed to temperatures as high as 7,000K (12,000F) on reentry, then endure a prolonged glide phase compared with an intermediate-range system, says Christopher Combs, who researches hypersonic aerodynamics as an assistant professor at the University of Texas, San Antonio.
“The bottom line is it’s just crazy temperatures,” says Combs. “They’re not dealing with space shuttle or Apollo [capsule] temperatures, but it’s still really hot.”
The rescinded RFI, meanwhile, also may provide a rare glimpse into the Air Force’s plans for the new ICBM developed under the GBSD program.
Apart from the thermal protection system for a hypersonic glider, the scope of effort in the RFI sought industry input on a variety of topics, including the following:
- Fusing data from lower-fidelity onboard sensors to improve guidance, navigation and control
- New navigation aids to correct inertial measurement unit drift on long time of flight missions
- A lighter, smaller and more efficient “future fuze” that also could “accept inputs from external subsystems”
- Radiation hardening techniques for advanced microelectronics such as a system on a chip or system in package
- Improved computer hardware and software, including artificial intelligence algorithms
- A more secure architecture and better security sensors for ICBM ground facilities.
The Air Force plans to award the contract to Northrop Grumman by the end of the month to launch the engineering and manufacturing development contract for the GBSD. Northrop remained the sole bidder for the program to deliver more than 600 new ICBMs to the Air Force after a Boeing-led team withdrew from the competition last year.
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