And we have lift-off! Well, not yet, but we are closer than we were before.
The final, spectacular test for the Space Launch System's (SLS) booster took place in Utah on Tuesday (local time).
It's the largest, most powerful booster developed yet and will later be used to propel humans to Mars.
During the test, flames shot out of the booster three times faster than the speed of sound, reaching more than 33000degC.
It was testing how the booster functioned when the motor was running at the lower end of the propellant temperature range, at just 4degC.
(NASA / Bill Ingalls)
In 2015 they had tested how higher temperatures affected the propellant, at 32degC.
The two-minute test produced enough energy to power more than 92,000 homes for a day, if it was converted to electric power.
William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate at NASA Headquarters, says the test shows "real progress".
"Seeing this test today, and experiencing the sound and feel of approximately 3.6 million pounds of thrust, helps us appreciate the progress we're making to advance human exploration and open new frontiers for science and technology missions in deep space."
Now that this test has been successfully completed, engineers will analyse the data ahead of an unmanned trek with the Orion spacecraft in 2018.
NASA says it's on track to get humans to Mars in the 2030s.