NASA's Space Launch System (SLS) rocket, also known as the most powerful rocket ever made is nearing completion. Recently, NASA performed a test fire of its controller or "brains," the RS-25 engine.

The brain is responsible for the operation of the engine and the communications with the SLS rocket. The new Engine Controller Unit-2 (ECU-2) was recently installed on the RS-25 development engine No. 0528. The new controller was test fired for 500 seconds at the A-1 Test Stand at Stennis Space Center. Once the controller passed the certification it will then be installed on one of the four flight engines. The engines will power the maiden flight of the SLS and the Orion spacecraft.

The brains or controllers were tests fired last March 23. Engineers conducted a hot-fire engine test. The tests are in preparation for the scheduled 2018 launch of the SLS rocket with the Orion EM-1 space capsule. The part of the SLS engine is called the brain due to its capabilities.

"The controller manages the engine by regulating the thrust and fuel mixture ratio and monitors the engine's health and status - much like the computer in your car," a NASA official said in a statement.

However, it is still a long way to the completion of the assembly of the SLS. According to NASA, there are two more engine controllers scheduled for testing this year. The fourth engine will have to wait for the "green run" on the B-2 Test Stand to be tested. The last test will involve firing all the engines at once mimicking an actual mission launch.

"This is important - and exciting - step in our return to deep space missions," Stennis Director Rick Gilbrech said in a press release. "With every test of flight hardware, we get closer and closer to launching humans deeper into space than we ever have traveled before."

Interestingly, the engines of the SLS rocket are former space shuttle main engine produced by Aerojet Rocketdyne. The engines, when activated all together can produce 2 million pounds of thrust and can operate with two solid rocket boosters to power the SLS launch.