At present he was the fastest human who ever lived. There was no engine rumble: the ship wasn’t under thrust. It had plenty of velocity from slingshotting past Jupiter and, later, Neptune.
Now, he was passing Sedna, relatively close for out here at any rate, and the computer was working the cameras hard. He’d have plenty to send back.
When that was done, a flip of the switch would turn on the new drive. Either the universe would collapse or he would find himself suddenly elsewhere. The longest leg of a trip of years, taking only seconds. If it worked.