As the four amateur astronauts head into space, the voice of Sarah Gillis will guide them into orbit.

Ms. Gillis is the lead space operations engineer for SpaceX, and her job includes training the astronauts on all safety aspects and operations of the flight.

Before takeoff, Ms. Gillis wished the crew good luck and a godspeed.

“It has been an absolute honor to prepare you for this historic flight,” she said.

In the Netflix documentary “Countdown: Inspiration4 Mission to Space,” Jared Isaacman, the mission’s commander paying for the trip, described her role as the equivalent of the “CapCom” on a NASA mission. That’s short for “Capsule Communication,” traditionally an astronaut on the ground who speaks with the crew in the spacecraft.

“The burden of ‘Will we execute well or not?’ will really fall on her,” Mr. Isaacman said in the documentary.

Ms. Gillis has been working for months with Mr. Isaacman and the other three astronauts to ensure they’re fully prepared for their trip, down to such details as how to operate a fire extinguisher on the flight.

“There’s two hats that you have to wear to be successful at that,” she said in the documentary. “One is the operational hat, where you need to understand exactly what actions you need to take to keep them safe. On the other aspect, I care very deeply about every single one of these people now.”

Ms. Gillis graduated from the University of Colorado Boulder with an engineering degree. In the Netflix documentary she said she was encouraged to pursue engineering by a high school mentor who was a former astronaut.

Ms. Gillis is also a classically trained violinist who started to learn how to play when she was 2 from her mother, a professional violinist.

“She certainly did not raise me to be an engineer,” she said.

This is not the first crew of astronauts riding in a SpaceX Crew Dragon capsule. In April, Ms. Gillis helped guide NASA’s Crew-2 mission to the International Space Station.

The flight was not without incident, as she had to warn the crew that a piece of space debris was about to come too close to their spacecraft for comfort. The crew was getting ready to go to sleep when she told them to perform a number of safety procedures, including putting their spacesuits back on.

The flight continued to the space station without incident and later analysis showed that it had been a false alarm, and no debris actually passed near the spacecraft.