The X-59 jet is Nasa and Lockheed Martin's joint offering, which the pair hope will retire the deafening sonic boom that is usually associated with supersonic aircraft.
NASA has completed the engine ground tests on its supersonic jet, which is expected to take to skies later this year.
But Nasa and Lockheed say the research jet won't have a troublesome sonic boom when it eventually flies.
“We have successfully progressed through our engine ground tests as we planned,” said Raymond Castner, X-59 propulsion lead at NASA’s Glenn Research Center, in an agency release.
“We expect the X-59 sonic thump to be as low as about 75 perceived loudness decibels,” Larry Cliatt, sub-project manager for the Quesst acoustic validation phase, said in an update last year.
