It’s time to seriously explore developing and deploying space-based interceptors, which would give the United States several advantages and improve the effectiveness of its missile defense architecture.

First, space-based interceptors would provide the ability to intercept an incoming enemy missile early in its trajectory, before it could release decoys and countermeasures meant to confuse missile defenses; second, they can fill gaps with our terrestrially-based missile defense and create depth of fire to protect population centers and other critical assets; third, they can augment our current defenses by thinning an enemy salvo in the midcourse phase of flight before it begins its descent towards its target; lastly, a space-based missile intercept layer will change an adversary’s behavior by limiting their choices of launch points and timing as well as flight trajectories which can play into the remainder of the missile defense system’s capabilities.

The concept has been around for decades, with varying degrees of support and criticism. Like any other new program, there are challenges to deploying a space-based interceptor (SBI) layer. But none of those challenges are insurmountable nor should they preclude the Pentagon from urgently undertaking the necessary steps to move towards deployment including architectural studies, proof-of-concept demonstrations, operational concept development, technical-risk-reduction activities, cost assessments, and acquisition-strategy planning. It is technically doable for the United States to deploy a test bed in the next several years to test the feasibility of concepts for intercepting various kinds of missile threats, and, based on the conclusions of that test bed, the U.S. can make decisions about when to deploy and how to expand and adapt it as the threats towards the United States develop.

Most experts, even those who oppose SBI, agree that it can be done. The United States validated technical feasibility in the 1990s and technology has only gotten better and more effective since then. Those who oppose it argue that it should not be done. One of the main criticisms of SBIs is that the concept is simply “cost-prohibitive.” Opponents of SBI often cite the highest cost estimates, in the hundreds of billions of dollars, which understandably causes sticker shock, which seems to be the point of providing those higher numbers. But two years ago, one of the authors of this piece (Ms. Heinrichs) wrote a report for Hudson Institute on SBIs guided by the wisdom and experience of a senior review group, which was comprised of individuals who have direct knowledge about satellite launch costs and are very familiar with the current technologies the country can use to adapt for the purposes of lightweight interceptors. One of the study’s reviewers was the other author of this piece (Lt. Gen. Obering). He and several other group members strongly disagree with the high figures often cited. The disagreements are rooted in several assumptions including those of satellite launch costs, the type of architecture that will be required based on the kinds of threats the United States will prioritize first, and the way life-cycle costs are calculated.

Among the reviewers is Michael Griffin, now defense undersecretary for research and engineering. In August, Undersecretary Griffin told reporters that the “idea of space-based interceptors has been in some ways the victim of unrealistically high, uninformed cost estimates” and naively judged “to cost much more than I believe that they would cost if one actually got down to business.” More recently, he provided back-of-the-envelope calculations for a space-based layer that would cost in the range of tens of billions of dollars, as opposed to hundreds. (Video: “If I use as a reasonable number based on experience — $20,000 per kilogram delivered to low orbit — and if I were to say that I would be content with a layer of 1,000 interceptors, which seems to me like a lot, and each of them weighs a metric ton…then the entire cost of that would be $20 billion.”) Even if that just includes launch costs, the total cost for development, production, and deployment wouldn’t land us anywhere near the sky-high numbers often cited by critics. Development would be far lower than skeptics imagine, thanks to the maturity of existing relevant capabilities. Again, there is no real way to know with greater accuracy until we take the concept seriously and move forward with architectural designs and cost assessments.

Another point of departure over cost is over the contention that a credible system would need many thousands of interceptor satellites and as such would cause the cost to balloon. But the aim of an initial space-based interceptor layer would not be to defend everywhere on the planet from any launch originating from anywhere on the planet, an aim that would require many more satellites. The United States, based on policy goals and priorities for defending specific areas and assets from known and pressing threats, can deploy an initial and tailored architecture with 1,000 or fewer SBIs. To settle the cost arguments, the Pentagon needs to get started in earnest with the right studies and initial test bed for proof of concepts.

After cost, the other frequent criticism of SBI is that it would be “destabilizing” and cause peers to build up their offensive forces to get around the new defensive measures. This is misguided. We have entered a new missile age where adversaries are heavily investing in missiles to exploit U.S. vulnerabilities in order to coerce, blackmail, and threaten U.S. freedom of navigation and to limit U.S. response options in the event U.S. adversaries attack U.S. allies. There is no evidence that the absence of SBIs has dissuaded adversaries from investing in missiles in quantity and sophistication; to the contrary, where there is a thinner layer of defense capability, there is evidence U.S. adversaries are seeking to exploit those holes. In response to what U.S. adversaries are doing, the United States should shore up its defensive systems. This would bolster U.S. deterrence, which is not merely comprised of nuclear and conventional weapons threatening punishment. Missile defense provides deterrence by denial and promises to limit the damage a potential act of aggression could cause, increasing the credibility of the U.S. deterrent. A more reliable missile dense architecture including current sea and land-based defensive systems, complemented by a space-based layer, would increase the credibility of U.S. deterrence and defense and would therefore increase stability, not decrease it.

The possibility that the United States could begin serious work on an SBI layer is more likely now than at any other time in recent history. This is because of the confluence of two main factors. First, Congress has been steadily leading the way in pushing for this development. Sen. John Kyl, R-Arizona, has been making the right policy arguments for missile defense in space, and pushing for Congressional funding for preliminary concept studies. He retired in 2013 but recently returned to the Senate to replace the late John McCain, and his return could portend a renewed cooperative effort to push for SBI. Sens. Tom Cotton, R-Arkansas, and Ted Cruz, R-Texas, have each supported the concept; the latter wrote a passage of the 2019 National Defense Authorization Act that requires the Pentagon, for the first time, to get started on an SBI layer.

The second factor is the president’s public statements supporting missile defense, generally, and the Trump administration’s focus on great-power competition. On the latter point, its National Defense Strategy expressed the determination to achieve and maintain U.S. strategic superiority over its adversaries, rather than parity. Having an SBI layer would improve America’s ability to do this very thing.

The first priority of the United States must always be its national security. Defending ourselves in space and from space must be a part of our military going forward. We have the technology, resources and talent; we just need the will to make it a reality.