Pentagon Examining Options for Space-Based Missile Interceptors
The Defense Department has been analyzing concepts for basing ballistic missile interceptors in space. Experts say deploying such a system would be technically feasible, but questions remain about its cost-effectiveness and strategic implications.
The idea of stationing interceptors in space was first seriously explored in the 1980s as part of former President Ronald Reagan’s strategic defense initiative, which was designed to thwart the Soviet Union’s nuclear arsenal. Known as Brilliant Pebbles, the project was canceled in the 1990s after the Cold War ended and the ballistic missile threat diminished.
But today, Russia and China are modernizing their nuclear forces. Meanwhile, North Korea and Iran continue to develop long-range missiles that could potentially hit the United States. While the U.S. military currently has a few dozen ground-based interceptors stationed at Fort Greely, Alaska, and Vandenberg Air Force Base, California, missile defense experts see value in deploying space-based interceptors to protect the homeland.
“Today there’s more of a political need than there has been in recent decades,” said Peter Hays, senior space policy analyst at Falcon Research supporting the principal Department of Defense space advisor staff.
In fiscal year 2016, the Missile Defense Agency conducted analyses of architecture alternatives for space-based missile interceptors. Lawmakers have directed defense officials to create a plan for developing one or more programs of record for a space-based ballistic missile intercept layer, including estimates of the appropriate identifiable costs of each potential program.
The existing Ground-based Midcourse Defense system, known as GMD, is designed to intercept long-range missiles during the midcourse phase of intercontinental flight above the Earth’s atmosphere. Space-based interceptors could be a game-changer by conducting boost-phase intercepts, experts said.
Boost-phase intercepts target ballistic missiles in the first few minutes of flight, before the missiles exit the atmosphere and individual warheads are deployed.
“If you want to do global boost-phase missile defense with current technology, there is one place where you can base those systems, and that is in space,” Hays said at a space security conference hosted by the Center for Strategic and International Studies.
Boost-phase defenses could provide several advantages over midcourse intercept systems, experts said.
“Engaging missiles while their engines are still burning holds the promise of preempting the deployment of post-boost vehicles, reentry vehicles and countermeasures, thereby avoiding the midcourse discrimination problem,” analysts from CSIS said in a recent report titled, “Missile Defense 2020: Next Steps for Defending the Homeland.”
During the boost phase, the missile remains in one piece and gives off a large plume, making it easier to identify and target, experts noted.
“The missile’s body is also weaker than the insulated and shielded reentry vehicle. Even a limited boost-phase layer could assist with ‘thinning the herd’ and disrupting structured attacks,” the report said.
Boost-phase defense also has the advantage of engaging a threat missile as far away from the U.S. homeland as possible, potentially over the enemy’s own territory, experts said.
“The earlier you can [engage], the more likelihood there is that you hit all the warheads in that vehicle, the more likely it is that it falls down back on the heads of the folks that launched it instead of your allies or yourself,” Hays said.
“The other great positional advantage is actually the velocity that you get from being on orbit. … This target is coming up to you in low-Earth orbit, so the distance to intercept becomes smaller and smaller [and] you get multiple shots at it,” he added.
Space-based interceptors would also have much better coverage than ground-based systems, experts said.
“Because a space-based system could defend against launches from virtually any location on Earth, there is no terrestrial equivalent for comparison,” CSIS analysts said in another report titled, “Implications of Ultra-Low Cost Access to Space.”
Pentagon officials have said that space is now a warfighting domain on par with air, land and sea. In that respect, space-based interceptors could potentially be used to target adversaries’ satellites, according to the report.
“The large amount of propellant each interceptor needs to de-orbit and maneuver into an oncoming missile could also be used to change its orbital trajectory to intercept another satellite,” it said.
Pentagon officials have been warning that Russia and China have tested and are developing technologies that could threaten U.S. space systems. A space-based interceptor could be employed to defend against enemy anti-satellite weapons, also known as ASATs, the report noted.
“A direct ascent ASAT weapon launched from the ground toward a satellite in [low-Earth orbit] would look much like a ballistic missile and therefore could be intercepted in the same way,” it said.
But relying on space-based interceptors has drawbacks, experts noted. In order to reach enemy missiles during boost phase before they burn out, the interceptor must be stationed in low-altitude orbits.
“In these orbits SBIs move rapidly with respect to the ground and cannot stay over any one location on Earth,” a fact sheet published by the Union of Concerned Scientists said. “Therefore, ensuring that at least one interceptor is within reach at all times of even a single missile launch site requires many SBIs in orbit.”
Several hundred space-based interceptors would need to be deployed to defend against a single missile from North Korea, it said. A constellation of many hundreds or thousands would be required to provide limited coverage against ballistic missiles launched from areas of concern, it asserted.
Such a system would be “enormously expensive” and would raise significant issues for crowding, debris mitigation and traffic management in space, it added.
Another key drawback to a space-based system is that once interceptors are used, a gap opens up in the constellation, the CSIS report said. “An adversary can exploit this by launching a salvo of missiles at once, effectively saturating the system in one location with more missiles than there are interceptors within range.”
Because defenders don’t know in advance when or where the salvo will be launched, doubling the number of missiles that could be intercepted would require doubling the size of the overall constellation, “a cost that scales in favor of the attacker,” it said.
Russia and China have tested anti-satellite weapons that could challenge the survivability of the interceptors, the CSIS report noted.
Hays said deploying a large, distributed architecture would mitigate that vulnerability. “We’re talking about thousands of these vehicles … so the vulnerability of each individual node probably doesn’t matter for the overall system operation.”
Still, Hays acknowledged the need for a layered defense system that would include terrestrial-based interceptor capabilities. “I would not want to rely just on a space-based layer,” he said. “But I also do believe that ... you get all kinds of positional and velocity advantages in space that are not possible in other domains.”
Developing and deploying such a system would be feasible from a technology perspective, experts said.
The kill vehicles could be relatively small, weighing about 50 kilograms which is roughly the size of the kill vehicle used in the existing GMD system, the CSIS report said. Space-based interceptors would need to be housed in a “garage” while on orbit for station keeping, communications and power, it added.
“It’s technically feasible,” Air Force Gen. John Hyten, commander of U.S. Strategic Command, told National Defense on the sidelines of a strategic deterrence conference in Arlington, Virginia. “Is it … practical? That’s the fundamental question because the expense is enormous [and] the command and control for that kind of capability is unbelievably complicated.
“It was technically possible 30 years ago but it wasn’t practical,” said Hyten, who served as chief of the engineering and acquisition division for space defense programs, and deputy for engineering in the strategic defense initiatives program office in the 1980s and early 1990s.
Hays said the technology required for such a system has continued to improve over time.
“The sensors, the computing power, the network needed to enable this type of capability have all proceeded forward rapidly and would only result in a cheaper, better system today than we would have had” decades ago, he said.
But basing interceptors or other weapons in space is not just a matter of having the right technology, it’s also a controversial political issue.
“It’s really more [about] political decisions and value decisions about where are the best investments to be made,” he said.
Todd Harrison, director of the aerospace security project at CSIS, said some policymakers flinch at the idea of deploying weapons in space.
“We do see a reluctance in people, especially in the space community, to be the one to break that taboo because you don’t know where it’s going to lead,” he said. “It’s kind of like the nuclear taboo — once someone breaks that and they use a nuclear weapon, then are the gloves off? Are other people… going to” use space-based weapons against U.S. space systems?
Cost is also an issue. CSIS estimates that the price tag for procuring and deploying 1,646 interceptors would cost $67 billion to $109 billion in constant 2017 dollars.
That does not include costs associated with research, development, test, evaluation, operations or sustainment.
Laura Greco, a senior scientist and space security analyst at the Union of Concerned Scientists, referencing a National Academy of Sciences report, said putting interceptors in space would cost 10 times as much as other basing options and more than $300 billion just to create an “austere capability.”
“I haven’t seen any revolutionary technology that would change this assessment,” she said.
James Miller, president of Adaptive Strategies and the former undersecretary of defense for policy, suggested that trying to develop a system to defeat Russia or China’s large missile arsenals could be a fool’s errand.
“I’m skeptical that we have the ability to defeat the advanced countermeasures of today, let alone those of tomorrow,” he said. “If we begin to pursue that … we’re going to throw more money at the qualitative side, and that could be a large hole if not an infinite hole” for investment especially if the number of interceptors involved were scaled up.
Rear Adm. Jon Hill, deputy director of the Missile Defense Agency, said it’s unclear when the Pentagon might be able to deploy a space-based interceptor architecture. “It really does come down to time and investment there, and with that we just don’t have the program of record for me to declare a timeline for weapons in space.”
For now, the main focus will be on developing and deploying a network of space-based sensors to better detect and track enemy missiles, he said.
Hays sees such an effort as a prelude to eventually deploying weapons in space.
As an analogy, he referenced the evolution of the United States’ aerial drone capabilities. They were initially used strictly for intelligence, surveillance and reconnaissance, but were later armed to conduct missile strikes.
“I think it falls in line of what the United States has done with things like a Predator where we said, ‘It’s nice to look at these [enemy locations] but it would be even nicer if we could schwack them while we’re looking at them,’” he said.
The Pentagon is undertaking a comprehensive ballistic missile defense review, also known as the BMDR, to map out the path ahead. That will include looking at interceptor options, said Walter Chai, director of space systems at the Missile Defense Agency.
“It’s really going to be up to the BMDR where we are maturity wise and policy wise,” he said.
Hyten said: “They will look at the entire [missile defense] enterprise. … I’m not going to share what’s in there. But they’ll look at the entire spectrum, make sure we’re doing the right things, going down the right path. And we’ll see where the administration comes out.”
The review is expected to be completed this fall.