Re: OT: Repeatably lobbing "projectiles"

On 11/23/2024 1:49 PM, Liz Tuddenham wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
 

On 11/23/2024 3:50 AM, Liz Tuddenham wrote:

[...]

Another possibility is a variant on a pea-shooter that has a steady jet
of compressed air entering a long tubular barrel through a port in the
side.  A continuous line of 'peas' is slowly pushed up the barrel and as
each one passes the port, it is accelerated by the air stream.  You only
need to control* the air steam continuously, there is no need to
micro-mange each pulse.

>
Now that's a "different" approach!  But, the air exiting the barrel doesn't
create a vacuum that drags "unwilling" peas into it?  Or, is the space
"behind" the peas closed, limiting any displacing air from being drawn
in prematurely?

 If we are allowed to specify the shape of a projectile (within limits) a
ball-shaped projectile may look like the obvious choice, but it is not
particularly aerodynamic and may have errors induced by erratic
turbulence  I would suggest that the projectiles could be tear-drop
shaped to give them the best aerodynamics, with slightly spiralled tail
fins that engage with rifling in the barrel to spin stabilise it in
flight.

Do you think that would actually be significant on such a small scale?
"Rifling" in a gun barrel seems to be an improvement to maintain
controlled flight over REALLY LONG distances and at high muzzle velocities.

If you don't want it to bounce on arrival and would rather not use hard
solid material which might cause damage, you could use a shaped
thinwalled polythene bag full of sloppy semi-liquid that would be firm
enough to take up the spin but would cause the bag to burst on impact.

OK.  I had assumed "water" just because it "flows" once the bag has ruptured.
(the ruptured bags represent minimal litter and the water will
eventually evaporate.  Think about what a golf driving range looks like
to get a feel for the "litter" created by unretrieved projectiles)

In flight, semi-liquid droplets tend to take up the shape of a teardrop
naturally, so the bag need not be particularly stiff, but it would need
some sort of hoop around its point of largest diameter to ensure that it
sealed well in the barrel.  The fins could extend from the hoop
backwards along the body to rigidise it and impart the spin.

What if there was a "plunger" that provided the seal, with the "payload"
sitting ON the plunger, while loaded?  E.g., like a linear catapult.

The barrel needs to have multiple ports around the circumference where
the air is injected, supplied by a 'manifold' in the form of a collar
surrounding the barrel.  At least two projectiles would have to be
waiting in the barrel, they could be pushed forward by a positive
displacement plunger so as to drive the hoop of the first one past the
air ports, the second one acting to block the barel and prevent the
escape of air backwards.

Could a "gate" behind the ONE projectile not serve the purpose of the
second?  Or, the plunger I mentioned, above?

The plunger would then be moved backwards and another projectile
introduced into the space through a slot in the side of the barrel.
There is no need for a sealed 'breech' as the second projectile acts as
a breech block.  That sort of loading mechanism lends itself to
automation or even gravity feed from a vertical magazine.