International Space Agencies – Missions and Discoveries

What is Suborbital Flight?


From UPSC perspective, the following things are important :

Prelims level : Difference between Orbital and Suborbital Flight

Mains level : Space tourism


Virgin Group founder Richard Branson became the first billionaire to fly to the edge of space and back, riding aboard his own Virgin Galactic spacecraft in a suborbital flight.

What is Suborbital Flight?

  • When an object travels at a horizontal speed of about 28,000 km/hr or more, it goes into orbit once it is above the atmosphere.
  • Satellites need to reach that threshold speed in order to orbit Earth.
  • Such a satellite would be accelerating towards the Earth due to gravity, but its horizontal movement is fast enough to offset the downward motion so that it moves along a circular path.
  • Any object travelling slower than 28,000 km/hr must eventually return to Earth.
  • These are suborbital flights, because they will not be travelling fast enough to orbit Earth once they reach there.
  • Such a trip allows space travellers to experience a few minutes of “weightlessness”.

Analogical example

  • For an analogy, consider a cricket ball thrown into the air.
  • Given that no human hand can give it a speed of 28,000 km/hr (about 8 m/sec), the ball will fly in an arc until its entire kinetic energy is swapped with potential energy.
  • At that instant, it will lose its vertical motion momentarily, before returning to Earth under the influence of gravity.
  • A suborbital flight is like this cricket ball, but travelling fast enough to reach the “edge of space”, and yet without enough horizontal velocity to go into orbit.
  • If an object travels as fast as 40,000 km/hr, it will achieve escape velocity, and never return to Earth.

Why the buzz?

  • With Branson and Jeff Bezos kicking off private space flight, several companies are looking for customers wanting to go on suborbital or even orbital journeys.
  • At Branson’s Virgin Galactic, around 600 people have already paid deposits for tickets that are priced up to $250,000 (Rs 1.86 crore).
  • However, Bezos’s Blue Origin, which uses the reusable New Shepard rocket, is yet to announce commercialization plans, according to the BBC.
  • There is also excitement among scientists who want to use suborbital flights for microgravity research.
  • Such flights would be far less expensive than carrying experiments and people to the International Space Station.
  • Suborbital flights could also be an alternative to parabolic flights in airplanes that space agencies currently use to simulate zero gravity.

Safety concerns

  • The Branson flight comes seven years after his company’s first rocket, called Enterprise, crashed during a test flight, killing one of the pilots on board.
  • The other survived after parachuting out.
  • The current rocket is also not certified by the US Federal Aviation Administration, which is prohibited to do so by law until 2023.
  • This is because the US government does not want to burden companies like Virgin Atlantic with regulations during their “learning” period, when they can innovate by trying out different designs and procedures.
  • Passengers who go on such trips need to sign “informed consent” forms, similar to the ones before going for skydiving or bungee jumping.

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