What is a suborbital flight? An aerospace engineer explains

“Suborbital” is a term you will hear a lot like Sir Richard Branson flies aboard Virgin Galactic’s winged VSS Unity spacecraft and Jeff Bezos flies on board Blue Origin’s new Shepard vehicle touch the limit of space and experience a few minutes of weightlessness.

But what exactly is “suborbital”? Simply put, this means that even though these vehicles will cross the ill-defined limit of space, they won’t go fast enough to stay in space once there.

If a spaceship – or anything else, for that matter – hits a speed of 17,500 mph (28,000 km / h) or more, instead of falling to the ground, it will continually fall around the Earth. This continuous fall is what it means to be in orbit and this is how the satellites and the Moon stay above the Earth.

Anything that launches into space but does not have sufficient horizontal speed to stay in space – like these rockets – returns to Earth and therefore follows a suborbital path.

Why these suborbital flights are important

Although the two spacecraft launched in July 2021 will not reach orbit, the achievement of reaching space in a private spacecraft is a major milestone in human history. Those on board these and all future private sector suborbital flights will be in space for a few minutes, experience a few minutes of exhilarating weightlessness, and absolutely earn their astronaut wings.

A diagram showing the paths around the Earth.