Encyclopedia Astronautica
Newton's Orbital Cannon

Newton's Cannon
British gun-launched orbital launch vehicle. Isaac Newton discussed the use of a cannon to attain orbit in 1687 in his Principia Mathematica - the very book that defined classical physics and provided the theoretical basis for space travel and rocketry. Newton used the following 'thought experiment' to explain the principle of orbits around the earth (see illustration):

Imagine a mountain so high that its peak is above the atmosphere of the earth. Imagine on top of that mountain a cannon, that fires horizontally. As more and more charge is used with each shot, the speed of the cannonball will be grater, and the projectile will impact the ground farther and farther from the mountain. Finally, at a certain speed, the cannonball will not hit the ground at all. It will fall toward the circular earth just as fast as the earth curves away from it. In the absence of drag from the atmosphere, it will continue forever in an orbit around the earth.

This was the first and best explanation of what an orbit is. An object in orbit is weightless not because 'it is beyond the earth's gravity' but because it is in 'free-fall' - just like a skydiver. The difference is that it has enough horizontal speed never to hit the ground.

Although Newton did not intend this to be a practical proposal, the example was certainly known to all who would later dream of the 'shot into infinity'....

Status: Design 1687.

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See also
  • Gun-launched Artillery dominated military ballistics from the earliest use of gunpowder. In 1865 Jules Verne could only realistically consider a cannon for a moon launch in his influential novel. Even after the rocket established its primacy as a method of accessing space, Canadian Gerald Bull began a life-long struggle to use guns for cheap access to space. His successes could not generate funding to continue. Others since then have pursued the technology, convinced it was the only way for low-cost delivery of payloads to orbit. More...

  • Ley, Willy, Rockets Missiles and Men in Space, Viking Press, New York, 1968.

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