President Trump revealed an ambitious plan Tuesday to build what he calls the "golden dome" to shield U.S. missile strikes.

"Once the golden dome is fully built, even if it is launched from other aspects of the world, even if they are launched from space, it will be able to intercept missiles," Trump told the Oval Office reporter.

Trump's budget and the project's schedule are ambitious. He told reporters he hopes to do this “before my term ends.” The president said the system would cost about $175 billion and start building $25 billion in next year's budget.

A key part of Trump's plan is to place missile-sensing and breaking through the missile satellites simultaneously into orbit above Earth. The constellation may involve thousands of small satellites that are able to attack missiles the moment it is launched from a submarine or silo.

Such a huge satellite network would have been unimaginable a few years ago, but now at least theoretically. Elon Musk's company SpaceX has been using low-cost rockets to launch an Internet transmission satellite called Starlink. SpaceX said the Starlink system currently has about 7,000 satellites in orbit, a proportion that can be compared to most estimates that are limited space-based missile defense capabilities required.

"The overall efforts of the Golden Dome have long been long overdue," said Tom Karako, director of the Missile Defense Program at the Center for Strategic and International Studies. Karako acknowledged that space-based incoming missiles was an "evil difficult problem", but he said the reality is that the next war could be partially fighting above the Earth's atmosphere. Given this reality, he believes that Golden Dome's capabilities will provide the United States with strong defense capabilities and can also be used in anti-satellite warfare if needed.

"It's necessary to compete with a lot of things in space," he said.

Space-based missile defense has been a dream for politicians for decades. In 1983, Ronald Reagan announced a plan to intercept missiles from the then Soviet Union.

"I know it's a difficult task, something that can't be accomplished until the end of this century," Reagan said at the time. "It's going to take years, probably decades of efforts in many ways."

Finally, the Soviet Union collapsed, and could be achieved before anything close to Reagan's vision, but missile defenses have made progress. The U.S. Patriot missile has worked for decades to intercept shorter missiles, and the U.S. now has several systems that can intercept medium-range and intermediate ballistic missiles. It also has a small number of interceptors that can hit ice bomb ix bombs in the middle of flight. This capability is directed to North Korea's nuclear upstarts.

Other countries, namely Israel and Ukraine, have used missile defense measures in recent years to protect themselves from attacks.

However, intercepting intercontinental ballistic missiles is still a more difficult problem. ICBMs fired from the depths of the enemy and screamed back to Earth at hypersonic speeds, making them nearly impossible to hit at the end of the flight. They can also deploy baits that can trick interceptors. The best time to hit them is because they are only launched from silos, but doing so requires a very fast response to the space interceptor. Thousands of interceptors must be fired to ensure they are exceeded above the missile when launched.

In fact, it is far from obvious whether the technology has reached it.

The orbital system will be complex, expensive, and ultimately vulnerable to counterattacks, said Laura Grego, a physicist at the group's skeptical coalition of scientists who are involved in missile defense development. Grego said networks like Golden Dome could be defeated by clustering to overwhelm the system or attack the satellite itself. The United States has recently accused Russia of studying how to put nuclear warheads in orbit. Such a warhead can eliminate most of any gold dome system in space.

And the threats facing the United States are more diverse than ever. The latest report from the Defense Intelligence Agency shows that the Golden Dome must also compete with new and emerging threats such as cruise missiles, hypersonic missiles that can skip the edge of space and weapons called fractional orbital bombing systems that can be launched that can be activated, glided in a portion of the earth and then attacked from any direction.

The total price of the Golden Dome is far from certain. The president said it could be completed for $175 billion in three years, but the latest estimate from the Congressional Budget Office has put costs between $161.1-54.2 billion in two decades. In addition, Senator Tim Sheehy of R-Mont, who is leading the "Golden Dome Caucus" Space News.

Given the potentially high costs, Greg hopes Congress will take a closer look before giving the Trump administration’s funding pursuit system. “The road to missile defense is full of plans that start and give up years later,” Greg said. “I want to ask a tricky question before you get on that path.”