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How fast could a human-powered medieval projectile go?

Rules:

  • The weapon must be made of materials available in medieval times: wood, steel, catgut, bone, rope, etc. No modern composites or plastics.
  • Engineering must be done to tolerances achievable in medieval times.
  • Human muscle power must be the power source. No explosives, no fires, no battery piles.
  • Electricity-powered weapons like railguns or coilguns are not allowed. Magnets are not allowed.
  • It is allowed to store the human muscle power as elastic potential energy (e.g. a bow), kinetic energy (e.g. a flywheel), gravitational potential energy (e.g. a trebuchet), compressed air, or thermal storage. Other energy storage methods are not allowed.
  • If necessary, it is allowed to have many humans working together to power the weapon.
  • The design of weapon does not need to have been known to medieval engineers, as long as it uses medieval materials in conformance with these rules.
  • Speed of projectile is measured at time of release.

So, what are the upper limits for projectile speed? Can we get to 800 m/s, like a sniper bullet?

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    – L.Dutch ♦
    Jul 30, 2022 at 4:22

1 Answer 1

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Empirical evidence: the whip.

The crack of the whip happens when the whip tip reaches the speed of sound in air (about 330-340 m/s depending on air temperature). Massaging the equations seems to indicate that up to three times that is possible without needing special materials (crude springs have been available for a long time).

This means that a projectile speed of 1000 m/s is possible (or should I say, not impossible).

On the other hand, actually achieving this speed requires either luck, or knowledge or research - the means to investigate whether the speed is going up or down with different setups, and even the awareness that a higher speed is possible at all.

None of these things, except luck, were available in the Middle Ages.

The speed of such a projectile, detaching from the whip exactly at the time of the crack, would also probably rapidly fall off due to aerodynamic considerations (adding fins to it seems excessive. Again, it is not impossible).

Also, nothing has been said about aiming the projectile.

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