3 ms·

Smooth bore as far as I know. Even tank cannons are mostly smooth-bore these days. The problem with those graphs is that they are not optimizing propellant qu

by nickff 11y ago

Smooth bore as far as I know. Even tank cannons are mostly smooth-bore these days. The problem with those graphs is that they are not optimizing propellant quantity for each barrel length. Adding an axis for quantity of propellant shows that you get diminishing returns to increasing barrel length and propellant, but there is a limit to how much you can increase both without increasing the barrel's thickness (as well as the firing mechanism's strength). You also have to remember that a gun will require > Mach 25 to get to orbit, and air acts differently at that kind of speed (, and once past ~Mach 3).

arprocter 11y ago
Thanks for the insight - I guess it doesn't scale! Is there a reason the space gun would be at a 45 degree angle and not pointed vertically? I know the reason rocket launches happen as close to the equator as possible, but they still go straight upwards...
- nickff 11y ago
  Rockets only go up for a little while; most of the propellant is used to build up speed in the 'horizontal direction'. There have been some arguments that a strictly vertically-firing rocket would be best for going outside of Earth orbit, but the current strategy for all launches is to go up until outside the thickest part of the atmosphere, then go horizontal, to build up to orbital velocity.
  - arprocter 11y ago
    After reading about the end of of Project HARP - it seems like they intended to use the gun to fire a rocket, and after a certain altitude the engine would ignite to get into space.
    - nickff 11y ago
      Yes, and in the years since HARP, there have been a few rocket-assisted projectiles developed (though none which have been intended for space launch).[1] I should also mention that unless the projectile was fired at or above escape velocity (intended to leave the Earth's gravity well), it would require some onboard propulsion to 'circularize' its orbit (and avoid crashing back into the Earth on its first time around). [1] https://en.wikipedia.org/wiki/Rocket-assisted_projectile https://en.wikipedia.org/wiki/Rocket-assisted_projectile

by nickff 11y ago

arprocter 11y ago

Thanks for the insight - I guess it doesn't scale! Is there a reason the space gun would be at a 45 degree angle and not pointed vertically? I know the reason rocket launches happen as close to the equator as possible, but they still go straight upwards...

nickff 11y ago
Rockets only go up for a little while; most of the propellant is used to build up speed in the 'horizontal direction'. There have been some arguments that a strictly vertically-firing rocket would be best for going outside of Earth orbit, but the current strategy for all launches is to go up until outside the thickest part of the atmosphere, then go horizontal, to build up to orbital velocity.
- arprocter 11y ago
  After reading about the end of of Project HARP - it seems like they intended to use the gun to fire a rocket, and after a certain altitude the engine would ignite to get into space.
  - nickff 11y ago
    Yes, and in the years since HARP, there have been a few rocket-assisted projectiles developed (though none which have been intended for space launch).[1] I should also mention that unless the projectile was fired at or above escape velocity (intended to leave the Earth's gravity well), it would require some onboard propulsion to 'circularize' its orbit (and avoid crashing back into the Earth on its first time around). [1] https://en.wikipedia.org/wiki/Rocket-assisted_projectile https://en.wikipedia.org/wiki/Rocket-assisted_projectile