Empirical Earth · Space, Satellites & the Edges of the Map

Rockets work in a vacuum — better than in air

The claim

“Rockets can’t work in space — there’s nothing to push against.”

What is measured

A rocket moves by throwing propellant backwards and recoiling forwards, by Newton’s third law, which needs no air. Vacuum removes drag and back-pressure, so rockets work better in space than in the atmosphere, just as their vacuum-tuned upper stages are designed to.

What would show this is wrong

a rocket engine that loses thrust in a vacuum chamber compared with open air, or any measured violation of momentum conservation, neither of which has ever been observed.

Sources

  1. How a rocket produces thrust (Newton’s third law). A rocket accelerates by expelling propellant mass; the reaction force (Newton’s third law, conservation of momentum) drives it forward, wit link
  2. Specific impulse in vacuum, and the 1920/1969 New York Times episode. A rocket engine’s specific impulse is higher in vacuum than at sea level (e.g. the SSME, ~366 s vs ~452 s). In 1920 the link
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