Question about vacuum powered projectiles

[david brouh]

I'm writing a novel and wanted to research a possible weapon I came up with to make sure the physics are at least possible. However, I could not find anything on vacuum-based projectiles other than ping-pong balls, while this is interesting, but it doesn't answer my question on what would happen on a large scale.

is a vacuum force limited by the medium that is going to rush inside to fill it.
Is it even capable of firing something that weighs more than a ping-pong ball?
How much force can air exert when it enters a vacuum, is volume the most important factor or surface area of the projectile that the air will act upon.

Anyway, with my poor knowledge of physics, I imagined the weapon to be a cone shape (similar to a 747 nose cone), where the projectile is sitting in the curved part, then though matter manipulation (or whatever mechanism you like) the air is removed from the rest of the cone.

The flat part of the cone would be the weakest point in such a shape (I think) and would break first, this would force air behind the projectile and, either shoot the entire cone, or the cone would break and the projectile would shoot forth.

Anyway, that's the idea and the character can make a near perfect vacuum if it helps.

 

[BillTre]

Seems like a weak mechanism for powering movement, especially fast movement like would be expected of a projectile.
Seems like you would need a continual generation of vacuum for it to be very useful. Maybe that's the case. I don't know.
Could you point the vacuum forward and just suction up your victim when it gets there?
What would be the advantages and disadvantages of each?

 

[david brouh]

Seems like a weak mechanism for powering movement, especially fast movement like would be expected of a projectile.
Seems like you would need a continual generation of vacuum for it to be very useful. Maybe that's the case. I don't know.
Could you point the vacuum forward and just suction up your victim when it gets there?
What would be the advantages and disadvantages of each?

Then what would you suggest for a being who can manipulate matter at will? like what phenomenon would be the most destructive if you could do so

 

[Borek]

what would you suggest for a being who can manipulate matter at will?

If laws of physics don't hold, it can be anything you want. You are limited by your imagination only.

 

[stefan r]

I'm writing a novel and wanted to research a possible weapon I came up with to make sure the physics are at least possible. However, I could not find anything on vacuum-based projectiles other than ping-pong balls, while this is interesting, but it doesn't answer my question on what would happen on a large scale.

is a vacuum force limited by the medium that is going to rush inside to fill it.
Is it even capable of firing something that weighs more than a ping-pong ball?
How much force can air exert when it enters a vacuum, is volume the most important factor or surface area of the projectile that the air will act upon.

A vacuum does not move anything. Things move because of air pressure on the side opposite from the vacuum. Neither the common vacuum sweeper nor a tornado pick up anything. The atmosphere blows into the vacuum and debris gets pushed by the air.

At sea level atmospheric pressure is 1.01 x 10⁵ pa. Pascals(Pa) = N/m² = kg/(ms²) = J/m³

Dropping a projectile into a vacuum tube would be almost identical to blowing compressed air into a tube. The air compressor's tank would need to be set at 14.7 psi (1 atmosphere, or 101 kPa). A tube works better than a cone. BB guns and paintball guns have higher pressures.

...
Anyway, with my poor knowledge of physics, I imagined the weapon to be a cone shape (similar to a 747 nose cone), where the projectile is sitting in the curved part, then though matter manipulation (or whatever mechanism you like) the air is removed from the rest of the cone.

The flat part of the cone would be the weakest point in such a shape (I think) and would break first, this would force air behind the projectile and, either shoot the entire cone, or the cone would break and the projectile would shoot forth...

A 747 nose cone is designed to minimize the effect of air pressure.

Probably want a barrel. Projectiles shaped like bullets. Bullet shapes can vary.

If you are magically creating a vacuum you do not need any device. A vacuum in front of the projectile should move it faster because there no friction. Something flat like a Frisbee or a saw blade could take the full acceleration from air pressure on the flat side and then rotate before impact. Aiming would be hard if he was unable to sustain the vacuum at range.

...Anyway, that's the idea and the character can make a near perfect vacuum if it helps.

Why shoot a projectile? Remove air from lungs, pop eyeballs, freeze dry skin, or blow out eardrums. Launching the target would be more likely to do damage than lobbing a ball at them.

If your character can "make a near perfect vacuum" what happens to the air? Hard to believe you can make a vacuum without also being able to make compressed air.

Leverage can be a multiplier.

 

[david brouh]

A vacuum does not move anything. Things move because of air pressure on the side opposite from the vacuum. Neither the common vacuum sweeper nor a tornado pick up anything. The atmosphere blows into the vacuum and debris gets pushed by the air.

At sea level atmospheric pressure is 1.01 x 10⁵ pa. Pascals(Pa) = N/m² = kg/(ms²) = J/m³

Dropping a projectile into a vacuum tube would be almost identical to blowing compressed air into a tube. The air compressor's tank would need to be set at 14.7 psi (1 atmosphere, or 101 kPa). A tube works better than a cone. BB guns and paintball guns have higher pressures.
A 747 nose cone is designed to minimize the effect of air pressure.

Probably want a barrel. Projectiles shaped like bullets. Bullet shapes can vary.

If you are magically creating a vacuum you do not need any device. A vacuum in front of the projectile should move it faster because there no friction. Something flat like a Frisbee or a saw blade could take the full acceleration from air pressure on the flat side and then rotate before impact. Aiming would be hard if he was unable to sustain the vacuum at range. Why shoot a projectile? Remove air from lungs, pop eyeballs, freeze dry skin, or blow out eardrums. Launching the target would be more likely to do damage than lobbing a ball at them.

If your character can "make a near perfect vacuum" what happens to the air? Hard to believe you can make a vacuum without also being able to make compressed air.

Leverage can be a multiplier.

he can simply remove the air from the chamber remotely and the reason I don't affect the humans with the vacuum directly, is because magic is involved, if one character is using magic so can his enemies, so they are strengthened and would not be affected by a vacuum like a normal human would.
Anyway, the idea behind the question is for him to create a trap that can be activated by something else, this means he won't have to sit there using his abilities directly for every enemy.

 

[newjerseyrunner]

I'm very confused why you would want to use a vacuum to propel a projectile. As someone else said, the vacuum itself doesn't do anything, it's the air rushing to fill it that does work. This limited you by the surrounding air pressure. If the bullet has a square inch of surface area on the back side, removing the air in the barrel would only put 15 pounds of force on it. Granted, you could make the barrel really long, but it's much easier to go straight to 50,000 pounds by introducing an explosive.