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From: <bp@www.zefox.net>
Newsgroups: sci.electronics.design
Subject: Re: OT: Repeatably lobbing "projectiles"
Date: Fri, 22 Nov 2024 04:24:25 -0000 (UTC)
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Don Y <blockedofcourse@foo.invalid> wrote:
> On 11/21/2024 5:52 PM, bp@www.zefox.net wrote:
>> Don Y <blockedofcourse@foo.invalid> wrote:
>>>
>>> Ideally, I would like the mass to STOP at the destination (not bounce
>>> or roll away) but that's a secondary goal.
>> 
>> Apologies if I missed it, but what are the masses and accelerations in play?
> 
> The masses are negotiable.  As is the acceleration (as long as you
> can overcome gravity).
> 
Per projectile? All the same? Are they fragile? Same aerodynamics,
or variable?  Grams per cc, or cc's per gram? 

> The goal is to PLACE a "thing" (projectile) at a specific location
> relative to the launcher.  And, to have it reach that location
> with minimal interaction with anything located between the launcher
> and destination.

What's the permissible error in position and landing speed?

> 
> E.g., If something was located immediately adjacent to the
> launcher, the projectile's path should go OVER the obstacle
> and not expect to be able to pass THROUGH it.
>
That's a mortar or howitzer. 
 
> Imagine using a nerf gun to lob those little sponge balls
> up, over obstacles -- but, being able to precisely control
> the range so they land where planned (no farther nor shorter)

Now you're talking projectiles dominated by aerodynamic drag.
Does your launcher need to take air movement into account?

> But, to do so completely under automation, without any human
> intervention.

Are you thinking of something like 
https://en.wikipedia.org/wiki/Girardoni_air_rifle
? 

One could build a version to launch Nerf balls. Note that it
used a hammer to operate the gas valve and compensate at least
partly for pressure changes. You'd want a very low pressure
for 20 feet. Perhaps you want a toned-down potato cannon (I
think that was mentioned previously by someone).

hth,

bob prohaska