United States Naval Air Propulsion Center (NAPC)

This place holds a special meaning for me. I’ve visited several times, determined to explore every corner and uncover its secrets. But no matter how hard I tried, I never quite managed to see it all.

The main front building, the one closest to the road? Never got inside. The massive cooling building in the back with its giant fans and smaller outbuildings? Missed that, too. And then there was the tank farm—a cluster of 22 rusty tanks tucked away in the upper right corner of the property. For some reason, no one ever took pictures of those tanks, even though they sat quietly in the shadows. I only noticed them recently, flipping through my old research notes. That’s when it hit me: I’d never taken the path that led there, too hesitant to get close to the Trenton-Mercer Airport’s fence line. I wasn’t here to get in trouble. I was here for the peaceful, empty buildings, not to risk getting caught wandering near airport grounds.

Still, being there felt like stepping back in time. Walking those halls, I could almost feel the presence of the people who once worked here, pushing the boundaries of jet propulsion and mechanical engineering. It was humbling to imagine the innovation that had happened within those walls.

The only other “locals” I encountered were deer. They’d dart away at the slightest sound, disappearing into the trees as I wandered the grounds. Their nervous energy contrasted with the stillness of the place, a site now quietly holding onto its past.

The blue cooling system building. Just beyond this building were the huge cooling fans, but I was thwarted by heavy brush and vines with a quickening of dying sunlight. 

When the station closed on September 30, 1998, a range of facilities on the property were transferred or repurposed. These included five administration and office buildings spanning about 59,000 square feet, alongside five laboratory spaces offering an impressive 141,967 square feet for research. Eight additional structures provided around 40,450 square feet of covered storage.

The site’s centerpiece was its thirteen testing facilities, covering a massive 317,514 square feet—the largest portion of the property. Two off-site structures supported operations: a meter house on Scotch Road with a capacity of 100 kV and a 0.8-mile easement and a Delaware River non-potable water pumping station connected by a 2.2-mile easement.

Fuel storage was another key feature, with 22 tanks, each holding about 25,000 gallons, linked by 0.4 miles of underground pipeline. A steam plant, once capable of producing 120,000 pounds of steam per hour, also existed but may have been demolished after the property’s closure—the exact timing remains unclear.

In total, the property included 463 acres of permanent easement rights to support aircraft ascent and landing at Mercer County Airport, reflecting the scale and complexity of the station’s operations during its peak.

During World War II, the demand for cutting-edge aviation technology led to the establishment of the Eastern Aircraft Division of General Motors in Trenton, New Jersey. Beginning operations on January 2, 1942, this division played a crucial role in producing the TBF Avenger, a torpedo aircraft essential for wartime efforts. The pace was remarkable—the first aircraft was delivered by November of that year, and within just 13 months, the division had built an impressive 1,000 aircraft.

After the war, the need for more advanced testing facilities for turbine engines became apparent. In 1942, the Bureau of Aeronautics' Power Plant Design Division began studying the limitations of existing setups for testing large internal combustion turbines under simulated altitude conditions. By 1944, it was clear that a new, specialized facility was necessary. Trenton, already home to a government-owned site, was chosen as the location for what would become the Naval Air Turbine Test Station (NATTS).

NATTS officially began operations in July 1951, with full-scale engine testing starting in 1956. Over the next two decades, the facility expanded its capabilities and infrastructure, emerging as a leader in jet engine testing. It introduced groundbreaking technologies, including advanced data systems and chambers designed to simulate extreme environmental conditions, pushing the boundaries of aviation innovation.

By the 1970s, the mission at the Naval Air Turbine Test Station (NATTS) evolved to meet the growing needs of both military and civilian aviation. The facility expanded its focus, taking on testing for turboprop engines and eventually exploring unmanned aerial vehicles (UAVs). During this period, NATTS consolidated operations with the Aeronautical Engine Lab (AEL) in Philadelphia, greatly enhancing its capabilities and influence in the aerospace field.

I loved the various piping on this upper floor. A real eye-pleaser.

The 1980s brought further advancements with the addition of new test cells and cutting-edge digital control rooms. These upgrades made NATTS a state-of-the-art facility capable of handling the demands of newer, more advanced engines and systems. This period solidified its reputation as a key player in the development of naval aviation technology.

The story of NATTS, later known as the Naval Air Propulsion Center (NAPC), came to an end in 1998 following decisions made under the Base Realignment and Closure (BRAC) process. The closure led to 700 workers losing their jobs, with most relocated to facilities in Maryland and Tennessee.  

While its doors may have closed, the legacy of NATTS/NAPC lives on. Its pioneering work in jet and turboprop engine testing shaped the future of both military and commercial aviation, leaving an indelible mark on the industry after nearly five decades of groundbreaking innovation.

The testing chamber building. Everyone specifically came here for this room unlike no other. 

This section had so much potential for some fire portraits. Alas, I was running solo dolo. 

It's one of my favorite shots from here. If only I had lined up the shot properly for the upper half.

The pipeworks remind me of the lower portion of the Fusion Paperboard plant.

These large pipes were definitely a scrapper's wet dream.

So many large cast pipes were running through this building that I never went upstairs to check out the rest of this section. 

Sources:

1. n.a. (2024, April 23). (Demolition of Naval Air Propulsion Base in Ewing underway). The Trentonian.

2. n.a. (n.d.). (Naval Air Propulsion Center (NAPC) - Trenton, NJ). Cold War History.

3. n.a. (2024, April 23). (KRE Group Joins Ewing Township Officials to Begin Long-awaited Redevelopment of Former Naval Air Propulsion Center). Ewing Township.

4. Perry, J. (2024, May 1). (Ewing’s former naval facility comes down as redevelopment gets underway). NJBIZ.