HUNTSVILLE, Ala. — The U.S. Missile Defense Agency is “not averse” to developing and fielding space-based missile defense interceptors, its director, Gen. Samuel Greaves, said Aug. 8 at the Space and Missile Defense Symposium.

While it has appeared, in a way, like Congress has been pushing the development of space-based missile defense interceptors on an unenthusiastic MDA, Greaves stressed that the capability was part of many discussions within the MDA and the Pentagon.

“We are developing options to pursue that capability if the nation decides that is what we should be doing,” Greaves said. “Congress has already written some language that would push us, direct us, guide us in that area, so it’s part of the overall suite of activities we are pursuing as part of our portfolio.”

But Greaves added that should not take away from the agency’s current priorities. “The liability of the systems we have got in place today, we cannot take our eyes off of that; expanding our capacity and capability, developing our sensor suite and dealing with the advanced threat.”

In the fiscal 2019 National Defense Authorization Act, Congress mandates the development of the intercept layer for which it pushed in FY18. In that same fiscal year, the language requirement was contingent on what could be directed in the Missile Defense Review. This time, the legislation states the intercept layer will be developed, whether the review directs the activity or not.

A space-based interceptor, if deployed, would go after ballistic missiles in the boost phase or in the post-boost phase of flight before the re-entry vehicle has deployed, or it could go after a deployed re-entry vehicle, Michael Griffin, the undersecretary of defense for research and engineering, told reporters at the symposium.

What it can’t do is reasonably go after hypersonic threats, he explained, “because hypersonic threats that we have seen to date are flying at altitudes low enough within the atmosphere. So effectively your space-based interceptor would have to itself be a re-entry vehicle; you would have to survive re-entry in order to go after the hypersonic target, and that may not be a bridge too far, but it’s a pretty far away bridge.”

For Griffin, however, a space-based interceptor going after ballistic missiles, especially in the boost phase of flight, is “a relatively easy technological challenge,” he said. “The difficulty we have had in the past is centered around policy. It has not been the policy of the United States to deploy such systems.”

And while a space-based intercept layer is something that has been studied for decades, the lack of its actual development may have been “a victim of unrealistically high, uninformed cost estimates,” Griffin said.

“I have made my own preliminary cost estimates on what systems would cost, and I can’t figure out a way to make them cost as much as some of the numbers I’ve seen tossed around the media,” he said. “I have seen such estimates,” that have been in the tens of billions of dollars range, “and I don’t believe them to be well-founded.”

The MDA has been asked to look at a potential space-based interceptor, Keith Englander, the agency’s director of engineering, said during an Aug. 8 presentation at the symposium. “That is in the study phase, and then we will report out on that, and the department will make a determination on whether they want to invest in that or not,” he said.