Combs died Tuesday in the Alvord Desert in southeastern Oregon, according to the sheriff's office in Harney County. She was 39 years old.
"She was a brilliant master builder, engineer, driver, manufacturer, and science communicator, and she struggled every day to encourage others by her amazing example," said Adam Savage, a former employee. Moderator of the TV show "Mythbusters".
Combs appeared in several episodes of the series, while presenter Kari Byron was on maternity leave. She also appeared as a presenter in shows like All Girls Garage and Overhaulin.
On Tuesday, she tried to drive faster when she crashed.
"At around 4:00 pm on August 27, 2019, the Harney County 911 Center received a call reporting that a jet car was trying to break a speed record over land in the Alvord Desert , crashed and led to a death, "said the sheriff's office.
Valerie Thompson, the first woman to exceed 300 miles per hour on a motorcycle and the world's "Fastest Woman on Two Wheels" expressed mourning on Twitter and posted photos of both together.
"With a heavy heart, I share the news that Jessi Combs passed away yesterday when she tried to break a speed record," she wrote. "I also had a chance to try that record, but it was not my turn … that's the hit for me, Godspeed, Jessi Combs."