Re: OT: Repeatably lobbing "projectiles"

On 11/24/2024 12:43 PM, Liz Tuddenham wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
 

On 11/24/2024 7:36 AM, Liz Tuddenham wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
>
[...]

Couldn't the plunger be "polystyrene cup shaped" so it stays behind
for reuse, automatically?

>
No - because the cup has to be in contact with the projectile to
maintain its shape while it is accelerated up the barrel.  That means
the air pressure must be behind the cup.

>
I don't understand.  What's the difference between the cup BEING
the top of the plunger (which has air pressure behind it) and
leaving the barrel WITH the projectile?

 The plunger has to stay behind the air inlet so as to block the back end
of the barrel.

But the surface on which the "propelling pressure" acts need not be the
same surface that is acting as the cup.  They just have to be "one"
in terms of acting in concert.
E.g., imagine a propelling cylinder containing plunger and *sealed*
chamber (that develops the propulsive force).  Extend this outward
(in the direction the projectile will follow) as a perforated (or
slotted) tube -- the walls of which act to stabilize the projectile
OR PROJECTILE-IN-A-CUP.
Air can enter behind the cup as it is traveling outward.  The sizes
of the perforations/slots is determined by THOSE needs; the remaining
material (not perforated) addresses the needs of stabilizing the cup.
The actual plunger can still operate in a "sealed" chamber.
When the plunger reaches its end-of-stroke, the *cup* is still
constrained by the walls of the perforated tube IN WHICH IT
TRAVELS.  Yet, the projectile is free to leave it.
And, when the plunger is withdrawn, the cup "attachment" withdraws
(into its "slotted home") with it for reuse.
I.e., imagine the plunger was as "thick" (along the axis of travel)
as the total range of motion.  So, the end that is in contact with
the projectile need not be within the "active" portion of the
plunger's travel.
Am I *still* missing something??