U.S. Hypersonic Defense Plan Emerges, But Not Cash

Steve Trimble

A U.S. hypersonic defense system has evolved from wide-open concept studies two years ago into a densely layered architecture populated by requirements for a new generation of space-based sensors and ground-based interceptors.

Over the next two years, the first elements of the Defense Department's newly defined hypersonic defense architecture could advance into operational reality if all the pieces can overcome various challenges, including the Pentagon's so far ambiguous commitment to long-term funding.

• Space-based hypersonic tracking is possible in 2023
• New sea-based interceptor will possibly be ready by mid-2020s
• Pentagon seeks Congressional add-ons to finance plan

The Space Development Agency (SDA), with assistance from the Missile Defense Agency (MDA) and the Defense Advanced Research Projects Agency (DARPA), next year will start launching satellites into orbit with new forms of tracking technology optimized to perform the challenging task of remotely targeting hypersonic missiles as they maneuver in the atmosphere hundreds of miles below.

At the same time, the MDA and DARPA will soon begin demonstrating a new class of kinetic and nonkinetic interceptor technologies. In addition to solving the guidance and thermal challenges posed by hypersonic flight, this new class of missile defense weapons must be guidable by satellites potentially perched far over the horizon, not by sensors integrally linked on the ground to their launching systems.

Pentagon officials began conceiving a hypersonic defense architecture a year after launching multiple offensive weapons programs in 2017, seeking to close gaps in the ballistic defense system that missiles now fielded by adversaries are designed to exploit.

With the ability to maneuver hundreds of miles off a ballistic trajectory, hypersonic glide vehicles (HGVs) and cruise missiles are designed to evade the MDA's network of stationary ground-based and slow-moving sea-based radars dotted around the globe. By gliding or powering through the atmosphere against the warm background of Earth, the same missiles appear 10-15 times less luminous during the midcourse phase than the boost-phase, exoatmospheric objects that the MDA designed the Space-Based Infrared System (SBIRS) satellites to detect, according to Michael Griffin, the undersecretary of defense for research and engineering.

Closing those gaps will require serious investment. Despite plans to infuse more than $10 billion to field at least three different rocket-boosted HGVs by 2025 as offensive weapons, the Pentagon's financial commitment to field a defensive capability is not as clear.

The MDA, for example, submitted a fiscal 2020 budget request in February 2019 that included around $157 million in hypersonic defense. A month later, the agency submitted an unfunded-priorities list to Congress, asking for another $720 million for hypersonic interceptors and tracking sensors. Congress met the MDA more than halfway, adding $400 million to the final appropriations bill.

A similar shortfall then appeared in the MDA's fiscal 2021 budget request. The agency included $207 million for hypersonic defense but asked Congress to chip in another $224 million on top of the budgeted amount, according to a March report by the Center for Strategic and International Studies' (CSIS) Missile Defense Project.

Moreover, the Defense Department's long-range forecast for hypersonic defense spending shows an ambiguous commitment at best. The MDA plans to launch a competition to select a Regional Glide-Phase Weapon System (RGPWS) in fiscal 2021 but only if Congress approves the additional $224 million identified in the unfunded priorities list. At the same time, the new SDA plans to start demonstrating MDA's Hypersonic Ballistic Tracking and Surveillance System (HBTSS) alongside the SDA's own tracking layer in orbit.

But the unclassified version of the Future Years Defense Program, which details the Defense Department's five-year spending forecast, shows declining support for hypersonic defense after next year. If Congress approves the extra $224 million for MDA, hypersonic defense spending would peak at around $450 million next year, then average about $112 million annually from fiscal 2022 to 2025, according to the CSIS data. The implication seems clear: Despite the MDA's public commitment to a hypersonic defense system, the agency prefers to finance the development mainly by annual congressional add-ons.

Although the MDA's long-term funding plan for hypersonic defense is limited, the potential threats are no longer speculative. In December, the Russian government announced it had achieved operational status for the Avangard, a nuclear-tipped HGV launched by a modernized SS-19 intercontinental ballistic missile.

Two months earlier, Gen. Paul Selva, then-vice chairman of the Joint Chiefs of Staff, explained the implications of an adversary with a nuclear-armed HGV: Imagine if NATO attempted to blunt a move by Moscow to occupy a Baltic state, and Russian strategic forces responded by threatening to launch an Avangard missile. The now-retired general warned that a single Avangard could arc over the Arctic Ocean, and as it reached the northern tip of Hudson Bay, Canada, could change course. It could then veer to target the U.S. East Coast or strike the West Coast, Selva says. U.S. forces currently have no ability to deter or defend against such a capability.

To solve that problem, a new space-based tracking system is needed. The Pentagon's existing satellites are either looking for a more luminous signal than that of an HGV or a hypersonic cruise missile or are using a very narrow field-of-view sensor to minimize background clutter, says SDA Director Derek Tournear, who spoke with Aviation Week during a June 4 webinar.

The first attempt to solve that problem is scheduled for launch in fiscal 2024. Forty satellites in SDA's Tranche 1 constellation in low Earth orbit carry sensor payloads for tracking hypersonic missiles. Unlike the SBIRS or other space-based capabilities, the sensors will neither have a narrow field of view nor be optimized for tracking only during the boost or exoatmospheric phases of a missile's trajectory. Instead, the spacecraft in Tranche 1 will carry a wide-field-of-view infrared sensor.

“However, the jury is still out on whether [the sensors] will be able to form a track that is high enough quality to actually give you that fire control solution so that you can fire [interceptors] on [a] remote [track],” Tournear says.

The backup to the SDA sensor will be demonstrated under MDA's HBTSS program. The MDA is developing what Tournear calls a medium-field-of-view system, which falls between the narrow-field-of-view format of existing satellites and the SDA's wide-field-of-view design for Tranche 1. Ideally, the SDA's wide-field-of-view sensors will detect an HGV or a cruise missile and pass the data in orbit to the HBTSS sensors, which will then develop a target-quality track. That data will be passed down to interceptor batteries on the ground.

Modified interceptors, such as Terminal High-Altitude Area Defense, will augment new kinetic and non-kinetic options to shoot down hypersonic missiles. Credit: Missile Defense Agency

Within a few years, the SDA will find out how the concept works. By the end of 2022, eight Tranche 0 satellites equipped with the SDA's wide-field-of-view sensors should be in low Earth orbit. A year later, the MDA plans to launch two satellites into low Earth orbit with medium-field-of-view sensors. The Tranche 0 constellation—aided by 20 communications-relay and data-processing “transport” satellites—will provide a limited operational capability and validate that the sensors work as designed.

The next step comes in 2024, when the SDA plans to launch the 40 satellites in the Tranche 1 constellation. “We would have, in essence, regional persistence of [infrared satellites] over any area of the globe that we choose,” Tournear says. There is a catch, however. The launch of the Tranche 1 satellites in 2024 fall within the five-year spending plan but so far remain unfunded.

Shortly after the scheduled Tranche 1 layer is activated, the MDA plans to field RGPWS, the new interceptor optimized for HGVs. If Congress adds the funding, RGPWS could be fielded as early as the “mid-2020s” with the Navy's Mk. 41 vertical launch systems on ships and submarines, followed later by air- and land-launched versions. The design requirements for RGPWS are classified, but it's possible the interceptor may benefit from an ongoing DARPA program. Glide Breaker, which includes Aerojet Rocketdyne as a supplier, seeks to demonstrate a “critical enabling technology” for a hypersonic defense missile. The MDA also plans to demonstrate an “extreme power” microwave weapon against “very long-range” missile threats within two years.

At the same time, the MDA is adapting existing point defenses against atmospheric threats. Lockheed Martin is studying improved versions of the Terminal High-Altitude Area Defense system, called “Dart,” and of the Patriot, called “Valkyrie.” In addition to the extreme power microwave, Raytheon also is studying a new variant of the SM-3 called Hawk.

Editor's note: The article has been updated to correctly identify the names of the hypersonic defense concepts under study for THAAD and Patriot.

https://aviationweek.com/defense-space/missile-defense-weapons/us-hypersonic-defense-plan-emerges-not-cash