President Donald Trump’s surprise announcement that the U.S. would pursue an Iron Dome-like national missile defense system has taken a page from Ronald Reagan’s “Star Wars” initiative of decades ago.

Like Reagan’s never-fulfilled plan for a system to “intercept and destroy strategic ballistic missiles before they reached our own soil or that of our allies,” Trump’s vision for “The Iron Dome for America” is both sweeping and challenging. It will face the same kinds of obstacles that confronted Reagan, who speculated in 1983 that it “may not be accomplished before the end of this century.”

Nonetheless, given the threats and opportunities created by revolutionary advances in technology and a rapidly shifting geopolitical landscape, the U.S. has no alternative but to embrace what is rapidly becoming an existential challenge. How can that be done?

The idea of an “Iron Dome” is designed to echo the highly effective Israeli-U.S. missile defense system that has defended the Israeli population for years. But Trump’s executive order tasks the Department of Defense with creating something vastly more complex than the current Israeli Iron Dome.

The new system will use a system-of-systems approach to stymie enemy ballistic missiles alongside defeating both hypersonic and cruise missiles. As with the Reagan system 40 years ago, it would emphasize a space-based system both for sensors (which already exist) and actual interceptors.

From a threat perspective, the timing is certainly right. Both China and Russia are building highly dangerous, destabilizing and deadly hypersonic cruise missiles for either conventional or nuclear strikes, traveling at many times the speed of sound, far faster than systems today.

They also have the ability to maneuver at speed, making them almost impossible to hit with current systems. The technical challenges are breathtaking. What are the chances of success? And what new systems might contribute to a successful Iron Dome that can truly protect America?

I know the world of air defense very well. Throughout my long Navy career, I served in the premier anti-air warfare warships in the world, the cruisers and destroyers equipped with the vaunted AEGIS air defense system (“shield” in Greek). What I learned is how difficult it is to design, build, train, and operate even a single air defense system on a dedicated ship with hundreds of hand-picked crewmembers in the relatively simple tactical environment of being at sea — with no surrounding civilian communities, infrastructure or collateral damage targets to consider.

Far later in my career, when I was the Supreme Allied Commander of NATO, I was involved in overseeing U.S.-Israeli military-to-military cooperation. I watched the Israelis, among the best in the world at air defense, struggle to operate a multi-layered complex system with vulnerable civilian populations in and around their major cities. In addition to their Iron Dome, they had to integrate longer-range systems (David’s Sling and Arrow) as well as react to satellite intelligence (much of it supplied by the U.S.).

So I have a healthy respect for what the Department of Defense and the prime defense contractors must take on to create an effective system to protect the entire United States from such a wide range of threats.

Three elements will be crucial to the success of a new Iron Dome.

First will be the ability to have space-based sensors and interceptors.

Without the true “God’s Eye” view of the entire air, sea, and land space below, effective defenses will be impossible. As with Reagan’s plan, such space-based systems will be challenged from an arms-control standpoint; other nations will rightly see them as destabilizing and escalatory. The space-based sensors are already largely in place. The real challenge, as was the case for “Star Wars,” will be basing effective interceptors in space.

A second crucial element will be artificial intelligence — the ability to use AI to knit together the space sensors and interceptors with land-based air defense systems (AEGIS ashore, Ground-Based Interceptors, and other current technologies).

Given the rapid advances in AI, this will probably be a reasonably good bet for success.

The third element that ultimately may be the most difficult to design, build and implement will be a new method of destroying incoming missiles: lasers.

The air defense community has pursued this chimera for decades. The frustration for air defenders is often having not enough defensive missiles — witness the U.S. Navy’s challenges in fighting relatively primitive Houthi missiles and drones off the coast of the Red Sea.

The promise of lasers is simple: High-powered beams of light are the means of destroying the enemy’s systems. You never run out of missiles and your system moves at the speed of light, far faster than a conventional defensive missile. But the technical challenges remain very high, despite some recent Navy success with the HELIOS system.

Lasers feel like they are the air defense weapon of the future … forever. This will be the most challenging of the three elements of the system and seems to be the furthest away. But a truly effective Iron Dome system is hard to imagine without a laser component, given the high-speed nature and possibilities of being overwhelmed and running out of conventional air defense missiles.

All of this will cost a huge amount of money. The DoD’s Missile Defense Agency will be in charge of responding to the president’s executive order. They have been directed to provide a comprehensive architecture within 60 days — which is really the speed of light in U.S. defense contracting terms. On Feb. 18 the first Iron Dome “Industry Day” will bring together defense firms to begin what will assuredly be a deeply challenging process.

The cost — certainly in the range of tens of billions of dollars annually — has the potential to crowd out other important defense spending. But that price tag must be weighed against the cost of the potential loss of American lives and treasure that an effective missile shield for the United States could prevent.

James Stavridis is a Bloomberg Opinion columnist, a retired U.S. Navy admiral, former supreme allied commander of NATO, and vice chairman of global affairs at the Carlyle Group.