WASHINGTON — The U.S. Army is slowing its pursuit of a future ballistic missile interceptor to replace the Patriot family of missiles, but it is continuing to conduct research on a less expensive, more capable replacement in preparation to field a new missile down the road.

There’s no question a new interceptor — one that will have to keep up with higher performing radars and launchers — will be needed, Army officials told Defense News earlier this month. But the timing on when the Army plans to pursue a new missile has slipped by a year, according to a review of the service’s fiscal 2020 and fiscal 2021 budget request justification documents.

The Army laid out a plan in its FY20 budget request to spend $232.9 million for the program over the following five years.

The service planned to kick off the program in FY20, using $8 million to start a competitive selection of a future interceptor for its Integrated Air and Missile Defense System, the replacement for the Patriot air-and-missile defense system.

The service would conduct an analysis of alternatives in FY20 and planned to use other transaction authorities — a special contracting mechanism — to work on competitive concept developments.

The Army was due to make a materiel development decision in the second quarter of FY20, and would then take a year to conduct an analysis of alternatives. Then, the service would work on concepts over a two-and-a-half-year period, ending in the beginning of FY23. A competitive request for proposals would drop midway through FY22 with a competitive downselect in the second quarter of FY23, when the Army would also reach a technology maturation decision point.

But at the time of the plan, the service hadn’t chosen a future radar for its IAMD system and it has yet to field its Integrated Battle Command System, which is the brains of IAMD. IBCS has been delayed over the years, but is progressing through a limited user test. The service expects for it to reach initial operational capability in FY22.

The Army has since picked Raytheon to build prototypes for a new Lower-Tier Air-and-Missile Defense Sensor, or LTAMDS, to replace the Patriot radar, which the company also produces.

Now, according to Army FY21 budget documents, the service has pushed its plans by a year and has budgeted less than $40 million from FY21 through FY25 for the effort. The documents show the Army spent just $2 million in FY20 on the program and will spend roughly $8 million a year across the five year plan.

If the service follows its FY21 through FY25 plan as laid out in budget documents, it will make a materiel development decision in the second quarter of FY21 and kick off an analysis of alternatives, one that will be complete in the second quarter of FY22.

A request for proposals would be released in the first quarter of FY23 followed by a competitive downselect to a single vendor in the third quarter of FY24 and entry into a technology maturation phase.

Yet, Army officials didn’t clearly lay out a timeline to move forward on the program when pressed.

“We just made the full-rate production decision just in the last year or two,” on Patriot Advanced Capability-3 Missile Segment Enhancement missiles or PAC-3 MSE — the latest variant of the interceptor — said Brig. Gen. Brian Gibson, who is in charge of Army air-and-missile defense modernization. Gibson spoke to Defense News in its Space and Missile Defense Symposium Debrief Aug. 5.

“So even though it feels like they’ve been out there a long time, in some cases, the oldest ones have,” Gibson said, “we’ve just, as a department, made full-rate decisions in our recent past.”

Additionally, he argued, the Army is still working through what its future IAMD system will deliver and there are still undetermined factors at play that need to be figured out before the service could proceed on a new interceptor program.

“Part of those discussions, and the why on the timing ... are influenced by several factors,” Gibson said. “One of those is, in the past, our Patriot system, our radars, limited our missile performance. Our missiles were more capable than what our radars could allow them to perform.”

With a new LTAMDS sensor, “we take that constraint away in the future,” Gibson noted. He added that how LTAMDS performs will also “inform the speed and the necessity for how quickly we should pull forward, if we do the next missile.”

“But at some point,” he added, “threats evolve and those things so there’s absolutely going to be a need to develop a new missile.”

Gibson stressed that cost is going to play an important part in how the service chooses its next interceptor. Current missiles are roughly $3 million each and have been used to take out exponentially less expensive targets like $100 commercially purchased drones.

At the same time, Gibson said, “our missiles in the future have to evolve to greater altitudes, greater speed, greater maneuverability and the combination of those three things depend a whole lot on what sensors see and when they see it, but it also depends on the physical kinematics and design of our missiles. They need to operate in concert.”

And IBCS could provide a way to totally decouple launchers and radars on a battlefield and connect best sensors to best shooters to carry out defensive missions that no longer require a radar and a launcher to be co-located, according to Gibson. This means launchers could be positioned away from a radar and that could drive range considerations and other capabilities needed in a new interceptor.

Another factor will be how threats evolve in the coming years, he added.

Maj. Gen. Robert Rasch, the Army’s program executive officer for missiles and space, argued, in a separate media engagement Aug. 5, that evolving threats may be the biggest driver for when and how a future interceptor is pursued.

For now, the Army is keeping the effort in the early research phase “of what’s the art of the possible,” Gibson said.