MOORESTOWN, N.J. — Just west of the New Jersey Turnpike in Philadelphia’s suburbs, a latticework of steel is stretching skyward, preparing to support a prototype missile-defense radar so tall it required a local zoning variance. But even that won’t be high enough for Pentagon planners who think the real future of sensing is in orbit.

On a steamy August morning, a bright yellow crane hoisted beams to a small crew of workers, just about the only ones visible beyond a chainlink security fence. Only two weeks into the construction, the frame of this building was already several dozen feet high.

“We’re on a very aggressive schedule because we have to get the capability fielded by 2020,” said Carmen Valentino, the man in charge of the project for Lockheed Martin.

The latest piece of the Pentagon shield built to protect the United States from long-range ballistic missiles, the building will house the prototype Long-Range Discrimination Radar, which Lockheed Martin executives say will track enemy missiles more precisely than today’s sensors. Tests in New Jersey will help shape an even larger missile tracking radar being built in Alaska at Clear Air Force Station, a military outpost near the Arctic Circle that has watched for incoming ICBMs since the late 1950s.

Company executives here won’t say whose missiles the radar is built to track, but it’s no secret the radar in Alaska will face southwest, directly at North Korea, which has been test-firing rockets at an unprecedented pace this year.

“The number of tests has exceeded any previous year and we’re only seven months or eight months into it,” Vice Adm. James Syring, the director of the Missile Defense Agency said during a presentation at the Space and Missile Defense Symposium in Huntsville, Alabama, earlier this month.

Most concerning to the admiral was the June test of a Musudan, an intermediate-range missile that might be able to reach Guam, more than 2,100 miles away.

“The game has been escalated,” Syring said. “You couple this with what they’ve done with nuclear testing … and now you begin to understand the foundation for the decision we made as a country … to deploy a THAAD battery to the [Korean] peninsula.”

He also lamented North Korea’s mobile missile launchers, which the intelligence community has a difficult time spotting, and a recent test-launch from a submarine.

“Another game changer, what they did in demonstration, successfully ejecting a submarine-launched ballistic missile in April,” Syring said. “You think about the challenges that that will bring to our system from indications and warning and what we must overcome if that development continues to progress and succeed.”

Only six countries have submarines that can launch ballistic missiles operationally; North Korea would be No. 7. A missile sub would allow North Korea to maneuver beyond the field of view of fixed radars like the new one being built in Alaska.

That, plus the efforts by several militaries to develop superfast hypersonic missiles, have U.S. planners envisioning missile detectors in orbit.

“From a missile defense standpoint, we have to develop a future operational space layer,” Syring said. “Given where the threat is going, with hypersonics and more capability development with ICBMs and so forth, this persistent tracking and discrimination capability from space is a must.”

The Missile Defense Agency is eyeing $400 million “to develop and test” a space-based sensor. It has already started work on something called “space-based kill assessment”: satellites that will determine if a missile is successfully intercepted in space. The Missile Defense Agency wants to use these satellites shoot down test over the Pacific Ocean. The project involves putting small payloads on commercial satellites.

“I think it’s a vitally important, but yet understated, step on where we’re going to space,” Syring said.

And the payloads, he said, do not need to cost tens of billions of dollars like many Pentagon satellite projects.

“Space does not have to be expensive,” he said. “I challenge you to think on what can be done commercially, with commercial partners and in more rapid fashion.”

For now, ground radars like the one taking shape in New Jersey will be a bridge to the future.

The prototype radar will stand 73 feet tall, so high Lockheed needed a variance from the local government to build it. But that’s nothing compared to the radar in Alaska, which will have two 3,000 square-foot gallium nitride arrays that will watch North Korea.

“It will provide the advanced discrimination and search and discrimination capability for the [Ballistic Missile Defense System] that it doesn’t have today for long-range threat scenarios,” Valentino, the vice president of naval radar and future systems for Lockheed, said.

In other words, the radar will be able to tell the difference between ICBMs and decoys faster than existing radars. Getting tracking information sooner will make the missile interceptors more effective, he said. The radar will be able to see thousands of kilometers, “several times” farther than mobile radars that the Pentagon has sent to Japan to watch for North Korean missiles.

The radar in Alaska is just one in a series of improvements to the U.S. missile shield that the Obama administration has said are necessary to protect the U.S. from North Korean rockets.

Even though Lockheed is not slated to finish building the new Alaska radar until 2020, the Pentagon is already looking adding more ground radars and satellites that could track long-range missiles.

At the missile defense conference in Huntsville, Syring displayed a briefing slide that listed new “notional” Pacific and Atlantic radars. The radars are options for potential future requirements and are not funded projects.

“LRDR goes a long way to closing the ‘midcourse gap’ in the Pacific,” said Tom Karako, a missile defense expert at the Center for Strategic and International Studies. “While S-band [radar] is not as high frequency as an X-band, and while the Clear location does not have the reach of a radar on Shemya Island, it’s nevertheless an important step.”

Shemya is the tip of Alaska, 1,500 miles southwest of Clear Air Force Station and much closer to North Korea from where the Long-Range Discrimination Radar will reside. Midcourse intercept refers to shooting down a missile in the middle of its flight when it is outside the atmosphere.

Karako views the notional Pacific radar as an additional means to close the current “gap” in midcourse tracking and discrimination over the Pacific ocean.

“We won’t ever be able to completely close the midcourse gap and radically improve birth-to-death tracking and discrimination until we return to low-Earth orbit, infrared satellites,” Karako said. “That’s where they need to go.”