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What is suborbital space flight? An engineer explains

  • Publish Date: Posted about 1 year ago
  • Author: James Kenealey
Two very rich men have been racing each other into space.

Sir Richard Branson came out the winner, beating his fellow billionaire and Amazon founder Jeff Bezos by just a few days. On 11th July 2021, Branson finally launched to the edge of space aboard his Virgin Galactic space plane and has thus become the first person to fly on a spacecraft of their own making. With Elon Musk planning to launch an all-civilian crew into orbit later this year, the billionaire space race looks to be the kick start the space tourism business needed.

VSS Unity launched from New Mexico, taking Branson and other passengers to an altitude of 85 kilometres above the Earth, a level known as ‘sub-orbital.’

What is suborbital spaceflight?

In simple terms, suborbital flights take passengers to the edge of space (itself a very broad and ill-defined area) but not at a speed that will allow them to remain in space once they get there. If a spacecraft reaches a speed of 17,500mph, rather than fall back down to Earth, the spacecraft will continuously fall ‘around the Earth’ – otherwise known as orbit. When a craft, much like the VSS Unity, cannot reach this velocity, its trajectory will bring it back down to Earth and hence will be suborbital.

John M. Horack, Neil Armstrong Chair and Professor of Mechanical and Aerospace Engineering at The Ohio State University, explains:

“Conceptually, the flights that Branson and Bezos will be on are not terribly different from a baseball thrown into the air. The faster you can throw the baseball upward, the higher it will go and the longer it will stay in the air. If you throw the ball with a bit of sideways velocity as well, it will go farther down-range.

Imagine throwing your baseball in an open field. As the ball rises, it slows down, as the kinetic energy inherent in its velocity is exchanged for potential energy in the form of increased altitude. Eventually the ball will reach its maximum height and then fall back to the ground.

Now imagine that you could throw the baseball fast enough to reach a height of perhaps 60 miles (97 km). Presto! The baseball has reached space. But when the ball reaches its maximum height, it will have zero vertical velocity and start to fall back to Earth.

The flight may take several minutes, and during most of that time the ball would experience near weightlessness – as will the newly minted astronauts aboard these spacecraft. Just like the hypothetical baseball, the astronauts will reach space but won’t enter orbit, so their flights will be suborbital.”

The billionaires are firing the starting pistol on a new era of space tourism, and it’s surely only a matter of time before the average citizen will be able to go a suborbital day trip.

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