Astronauts who rode the SpaceX Falcon 9 rocket into space say it was a “pure flying machine” compared to the space shuttle, Fox6 reported.

It is worth-mentioning that Doug Hurley and Bob Behnken piloted the first manned flight of the Falcon 9 on May 30.

These astronauts had previously been on two space shuttle missions, and they spoke of their surprise at how comparatively smooth the SpaceX launch was.

Hurley has told Spaceflight Now, “What I thought was really neat was how sensitive we were to the throttling of the Merlin engines. That was really neat.”

He added: “We didn’t even need to look at the speed. You could tell just by how the rocket felt, so it’s a very pure flying machine.”

According to him, the shuttle had solid rocket boosters that burned very rough for the first two-and-a-half minutes. But the first stage with Falcon 9 was the nine Merlin engines, he said, “It was a much smoother ride, obviously, because it was a liquid engine ascent.”

The second stage felt a bit rougher, after the smooth launch, said the astronauts.

Behnken said, “The biggest difference is just the dynamics that are involved, the vibration, the experiences that we felt actually riding a real rocket.”

According to the report, NASA is working with Boeing on its manned Starliner capsule, which is expected to launch early next year.