Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: CliffordK on 12/02/2013 20:25:34
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Would a winged bullet travel further than one without wings?
One could design a bullet with spring loaded hinged wings, so that as soon as it left the barrel, the wings would deploy. Possibly including a slow time/velocity dependent deployment of the wings to maintain constant lift. Assuming no spin, could one use a passive system to keep it vertical?
So, would the engineless winged bullet travel further than an ordinary bullet? Wind resistance and drag would be greater, but lift would be greater too.
Of course, for a bullet, impact velocity is vital, but let's ignore that for the moment.
The other issue, of course, is accuracy, and I have no doubt that minimizing the profile in the air improves accuracy, so if the goal is to hit a target, passive wings may make the trajectory far less predictable.
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the rotation is evidently a very significant factor ...
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Yeah, I understood the rifling keeps rotating so that it behaves like a gyroscope and doesn't start tumbling in flight. That way the pointy end stays facing forward and reduces drag.
However, at slow enough speeds, wings clearly help: imagine throwing a toy airplane carrying a bullet as a payload as opposed to just throwing the bullet. My guess would be the transition happens as soon as the wings cause turbulence, which would cause significant drag and destabilize the flight.
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It exists, for instance
http://www.sauvestre.com/?lang=en
This sort of amunition is uses with shotgun in order to stabilize the trajectory.
With riffle, it is obviously impossible and unecessary, because of the natural rotation of the projectile.
An alternative, for shotguns, are the Breneke slug ammunitions : they give a rotation to the bullet.
http://www.brenneke-munition.de/cms/flinte.html?&L=1
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A tail (like an arrow) would sufficiently stabilize the flight to prevent tumbling. Of course it would add drag which the spin would not.
The tails on the shotgun slugs are for flight stabilization, not for lift.
Perhaps the key would not be to deploy the wings at the end of the barrel, but to detect "level", and deploy them at the vertex of a parabolic flight.
Turbulence, of course, might be a problem. I looked up double pointed bullets, and only found a 1906 article (http://query.nytimes.com/gst/abstract.html?res=F60E16F7355A17738DDDAA0894D1405B868CF1D3). Apparently the design didn't catch on.
Anyway, one would have to consider the effect of turbulence, varying velocity, and drag.
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US Navy developped wingled projectiles for the Mk45 5'' navy gun : the ERGM (Extended Range Guided Munition). See this.
http://en.wikipedia.org/wiki/Extended_Range_Guided_Munition
This projectile was not actually a shell but a missile with a rocket propulsor and a guidance system.
After launch from the gun barrel, wing fins were deployed and the propulsor was started.
AFAIK, the project was canceled due to fiability issues with the deployement of the fins.
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Don't know much about aerodynamics, but would it make a difference to shape the bullet asymmetrically in order to aid lift? Kind of like a cross-section of what I believe the wings of a plane are. Obviously wouldn't work in a spin-driven system but if you could align the bullet in the right position to begin with, it may do well.
Also, what about a bullet with a miniature propeller on the front?
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Cruise missiles, of course, are an extension of the idea, rocket powered, and able to at least moderately change direction with precise targeting. Usually launched at jet aircraft speeds.
Propeller? only at slow speeds.
I guess I was initially thinking of this with respect to the question of firing a projectile from a gun into space, and HARP (http://www.thenakedscientists.com/forum/index.php?topic=44594.0). The question came up about the optimal angle for maximum altitude (vertical), and horizontal distance (somewhere near 45°).
Anyway, I was wondering if one could use aerodynamic lift to either extend the vertical range, the horizontal range, or to increase the horizontal velocity at the maximum altitude.
The answer is obviously complicated. I could imagine shooting a hang glider to 100 miles altitude, then deploying the hang glider. It might be able to fly for thousands of miles before returning to Earth.