On a steamy, unsettled summer afternoon in Mississippi, the first thing I saw as I approached the John C. Stennis Space Center was what looked like a NASA-branded toll booth. I felt like I was going into a theme park, but all the security reminders at the check-in desk in the visitor’s center told me otherwise.

I was here to visit Rolls-Royce’s jet-engine testing facility, one of just three such places. The property had originally been designed for NASA’s horizontal rocket tests, but it was decommissioned for that purpose and eventually leased to Rolls-Royce, which began operations there in 2007.

After checking in and driving through a labyrinth of empty roads as part of clearing security, I knew I was close when I saw this sign:

Before seeing any of the facility, I had to watch a safety video about foreign object debris (FOD). Honestly, it was a masterpiece. It had an ’80s slasher-flick aesthetic and FOD was characterized as a demon to be avoided at all costs. I wasn’t planning on using any tools or workplace machinery that might generate FOD, but it was reassuring to know that Rolls-Royce takes safety so seriously. I also had to don protective gear including these “clown shoes”, which turned my own footwear into steel-toed boots for the day.

According to Dan Lyon, general manager of the Stennis Outdoor Test Facility, the British company moved its engine tests here from a location outside of Derby, England, because the town was undergoing development that brought housing much closer to the test sites. The new neighbors quickly found the jet-engine blasts a nuisance and the company needed to find a more remote location for its tests.

In Mississippi, Rolls-Royce has already grown, adding a second test bed at the site in 2013. The company now conducts noise tests at Stennis, along with maturity and cycle tests on engine components like thrust reversers.

The arena used for noise tests is pictured below. Microphones there are protected by white pyramid-like housings, and are so sensitive that they can pick up the sound of a cricket chirping even while a test engine is operating at full power. In order to mitigate data anomalies, flat surfaces like lamp and fence posts are angled away from the mikes, which prevents sound wave reflections from affecting the results.

This device, known as the “golf ball,” is used during virtually every noise test. It’s mounted to the front of the engine undergoing testing and helps tamp down the wind, which can affect noise levels.

If necessary, Rolls-Royce can also simulate more wind than is naturally available using this wind generator.

Engine tests at Stennis have to happen in specific weather conditions. Too much wind, especially, can affect the data that’s captured during the test. But this device (the large cylinder/cone in the center of the picture), called an inlet flow conditioner, can help extend the weather envelope for testing.

While I was visiting the facility, unsettled weather triggered lightning warnings at regular intervals. Because Stennis is mostly outdoors, if lightning gets too close to the area, employees working on projects outside need to pause and take shelter.

The noise test bed was not in use during my visit but the maturity test bed was. In here, safe from any possible lightning strikes, the crew was working on resolving an oil leak issue with a test engine. Once that problem was solved, they’d go on testing the thrust reversers.

The wall you see next to the engine on the upper right and top center screens in this picture prevents the thrust-reversed airflow from being reingested by the engine, which could affect the data.

Before an engine can go out for testing, and again when the testing is wrapping up, it first has to be processed by the prep shop.

Here, it’s made ready for testing and then taken apart again when the testing is complete. Two engines were in the shop during my visit: a Trent 7000 for Airbus, which uses it on the A330neo, and a Trent 1000 for Boeing, which uses it on the 787.

Although the engine is supplied by Rolls-Royce, the external components, like the intake and the cowling, are provided by other manufacturers. Here, the inlet was supplied by Airbus and the cowling by Safran.

Boeing, too, provides its own parts, including the now-iconic scalloped cowling.

These engines are huge, by the way. For reference, here I am in front of one.

The facility runs essentially 24/7, since some of the tests have to happen overnight.

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Featured photo by Zach Wichter/The Points Guy

Correction: The story has been updated to reflect that Rolls-Royce leases the Stennis property from NASA, to correctly reference a piece of equipment called an inlet flow conditioner, which was previously referred to as an inlet flow container and to reflect that, while an XWB engine was undergoing maturity tests during the visit, a Trent 7000 engine was in the prep shop.