Short range targeting...

[Phil Hobbs]

Martin Brown wrote:

On 26/12/2021 07:30, Rick C wrote:
On Saturday, December 25, 2021 at 10:01:03 PM UTC-5, Jasen Betts wrote:
On 2021-12-26, Don Y <blocked...@foo.invalid> wrote:
I want to \"hit\" a fixed spot with a physical object over
relatively short distances (< ~20 ft).
Accelerating a significant mass would likely prove to
be a challenge so \"lobbing\" the object seems more
practical. It would also *seem* to be more tolerant
of aiming issues than something HOPING to travel in a
straight line (like a bullet).

So, conceptually, a tube (\"barrel\") to guide the
initial segment of flight and some sort of mechanism
to propel the object from the tube.
mini trebuchet

+ 1

Yes. They are great fun. There is a bloke near me who has scale model
fully operational trebuchet able to lob a water melon about 200m!

It is very impressive and apart from the beam quite compact. When things
return to normal I might try and catch up with him again to film it in
action. He does charity gigs with it from time to time in normal summers
- needs a *lot* of space. (and careful crowd control down range)

This is the biggest one I have seen online and representative of the
sort of design that would work. Camera work is pretty good too:

https://www.youtube.com/watch?v=UdGqggET0o4

See you and raise you:

https://www.youtube.com/watch?v=M1iPxY3FYNE

At Warwick Castle there\'s a copy of Edward 1\'s Warwolf.

Here\'s a similar example;

https://www.youtube.com/watch?v=4_iIfZH33MA

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Don Y]

On 12/26/2021 1:15 PM, ke...@kjwdesigns.com wrote:

On Sunday, 26 December 2021 at 00:41:17 UTC-8, Don Y wrote:
...

How about this for some inspiration?

https://www.youtube.com/watch?v=sZm9ZEpvolw

<https://www.youtube.com/watch?v=EC5mLx6_8FI>

Unfortunately, I suspect considerably more than my $600K budget!

 

[Dean Hoffman]

On Sunday, December 26, 2021 at 6:01:36 PM UTC-6, Don Y wrote:

On 12/26/2021 1:15 PM, ke...@kjwdesigns.com wrote:
On Sunday, 26 December 2021 at 00:41:17 UTC-8, Don Y wrote:
...

How about this for some inspiration?

https://www.youtube.com/watch?v=sZm9ZEpvolw
https://www.youtube.com/watch?v=EC5mLx6_8FI

Unfortunately, I suspect considerably more than my $600K budget!

NASA spent 10 Billion dollars on this thing.
<https://thefederalist.com/2021/12/22/nasa-to-launch-telescope-stronger-than-hubble-that-can-see-back-in-time/>
Over budget and behind schedule, of course.
<https://www.cbsnews.com/live-updates/james-webb-space-telescope-launch-12-25-2021/>

 

[Don Y]

On 12/26/2021 6:05 PM, Dean Hoffman wrote:

On Sunday, December 26, 2021 at 6:01:36 PM UTC-6, Don Y wrote:
On 12/26/2021 1:15 PM, ke...@kjwdesigns.com wrote:
On Sunday, 26 December 2021 at 00:41:17 UTC-8, Don Y wrote:
...

How about this for some inspiration?

https://www.youtube.com/watch?v=sZm9ZEpvolw
https://www.youtube.com/watch?v=EC5mLx6_8FI

Unfortunately, I suspect considerably more than my $600K budget!

NASA spent 10 Billion dollars on this thing.
nasa-to-launch-telescope-stronger-than-hubble-that-can-see-back-in-time

------------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^

Maybe they can use it to sort out where their cost overruns were?

Over budget and behind schedule, of course.
https://www.cbsnews.com/live-updates/james-webb-space-telescope-launch-12-25-2021/

 

[David Eather]

On 26/12/2021 10:47 am, Don Y wrote:

I want to \"hit\" a fixed spot with a physical object over
relatively short distances (< ~20 ft).

This must not present a danger to nearby bystanders (in the
event of a \"misfire\").  \"Weapons\" are out of the question.

And, the object must be of sufficient size to be clearly
visible in transit.  This also suggests a low transit
velocity.

I figure I need a bit of mass to ensure aerodynamic
effects don\'t bugger the calculations.  E.g., a softball
would be better than a softball-sized hollow ball
which might exhibit more nonlinear behaviors as it
transits from projectile to ballistic motion.

The target is (effectively) a \"spot on the floor\".
I.e., not a vertical \"hoop\" to pass through (like
goalposts in soccer).

Accelerating a significant mass would likely prove to
be a challenge so \"lobbing\" the object seems more
practical.  It would also *seem* to be more tolerant
of aiming issues than something HOPING to travel in a
straight line (like a bullet).

So, conceptually, a tube (\"barrel\") to guide the
initial segment of flight and some sort of mechanism
to propel the object from the tube.

Pneumatic, hydraulic, mechanical, etc.

Will the control over the propulsive force be the tougher
challenge or the precise aiming of the launch tube?

[You are given (r,theta) to target and no feedback as
to proximity of strike -- unless a direct strike.  The
target -- or launcher -- will move after each attempt]

Of course, \"you\" is a machine...

A nerf gun.

 

[Anthony William Sloman]

On Sunday, December 26, 2021 at 12:55:39 PM UTC+11, dean...@gmail.com wrote:
> On Saturday, December 25, 2021 at 6:47:51 PM UTC-6, Don Y wrote:

<snip>

> > And, the object must be of sufficient size to be clearly visible in transit. This also suggests a low transit velocity.

When I was an undergraduate people did drop paper bags full of water on people passing below.

A longer range variants of this was rubber party balloons full of water.

We launched few from a ten foot long catapult - lots of rubber bands in series and in parallel - with a leather bucket to cope with the acceleration forces. The water-filled balloon contracted away from the leather bucket as the acceleration fell away.

I figure I need a bit of mass to ensure aerodynamic
effects don\'t bugger the calculations. E.g., a softball
would be better than a softball-sized hollow ball
which might exhibit more nonlinear behaviors as it
transits from projectile to ballistic motion.

The water filled balloon has a fairly stable shape - after a bit of initial sloshing around.

Accelerating a significant mass would likely prove to
be a challenge so \"lobbing\" the object seems more
practical. It would also *seem* to be more tolerant
of aiming issues than something HOPING to travel in a
straight line (like a bullet).

Everything travels along a parabolic path. Air resistance does eat into the momentum and velocity, but not that much.

--
Bill Sloman, Sydney

 

[Don Y]

On 12/27/2021 1:03 AM, David Eather wrote:

[You are given (r,theta) to target and no feedback as
to proximity of strike -- unless a direct strike. The
target -- or launcher -- will move after each attempt]

Of course, \"you\" is a machine...

A nerf gun.

I don\'t know how consistent their range is (given that the
\"ammo\" is likely very consistent).

And, adjusting range would obviously have to be done
entirely by tweeking elevation. Would such lightweight
ammo behave differently the higher it is lofted?
(cross currents, etc.)

Think about how \"nonlinearly\" (poor choice of word as
all flight is nonlinear) a whiffle ball reacts.

Some of the larger \"guns\" would solve the reloading problem
(for reasonably bounded values of \"ammo needed\")

And, discharged ammo would be relatively easy to \"clean up\"
(e.g., a large blower!) and would likely not be as lively
(bouncing) after touchdown.

 

[whit3rd]

On Sunday, December 26, 2021 at 6:51:58 AM UTC-8, Don Y wrote:

On 12/26/2021 5:45 AM, Clive Arthur wrote:

Snowballs.
Snowballs would be excellent! But, I\'m not sure how easy it
would be to make a machine that could form them, ...

OK, then, marshmallows. Spring and air piston to make
a puff of air pressure, and a mortar tube sized to the One True Size
of that white confection.

 

[Don Y]

On 12/27/2021 3:12 PM, whit3rd wrote:

On Sunday, December 26, 2021 at 6:51:58 AM UTC-8, Don Y wrote:
On 12/26/2021 5:45 AM, Clive Arthur wrote:

Snowballs.
Snowballs would be excellent! But, I\'m not sure how easy it
would be to make a machine that could form them, ...

OK, then, marshmallows.

*That* is a possibility! They used to (?) make (toy) \"marshmallow guns\".
So, clearly, you can propel a marshmallow over *some* distance. I\'m
not sure if 20 ft would be in that realm.

I can\'t imagine them being very \"lively\" when it comes to bouncing
(esp if lofted high). And, unlike beanbags, they\'d be pretty easily
compressed/run over/etc. so litter wouldn\'t be an immediate concern.

Also, I\'m not sure how much \"tumbling\" would impact repeatability.
Or, if there\'s enough entropy in the mechanical system to ensure a
specific amount of tumbling.

Spring and air piston to make
a puff of air pressure, and a mortar tube sized to the One True Size
of that white confection.

I know of at least two sizes. The larger would likely be more visible
(I wonder if they can be dyed?) but the smaller may be more predictable
projectiles.

I guess I\'ll have to put marshmallows on my shopping list (what a
disgusting confection!)

 

[Clive Arthur]

On 28/12/2021 01:52, Don Y wrote:

On 12/27/2021 3:12 PM, whit3rd wrote:
On Sunday, December 26, 2021 at 6:51:58 AM UTC-8, Don Y wrote:
On 12/26/2021 5:45 AM, Clive Arthur wrote:

Snowballs.
Snowballs would be excellent! But, I\'m not sure how easy it
would be to make a machine that could form them, ...

OK, then, marshmallows.

*That* is a possibility!  They used to (?) make (toy) \"marshmallow guns\".
So, clearly, you can propel a marshmallow over *some* distance.  I\'m
not sure if 20 ft would be in that realm.

I can\'t imagine them being very \"lively\" when it comes to bouncing
(esp if lofted high).  And, unlike beanbags, they\'d be pretty easily
compressed/run over/etc. so litter wouldn\'t be an immediate concern.

<snip>

Sorbo rubber balls don\'t bounce much and are fairly dense. It\'s
possible they\'re called something else in the US.

--
Cheers
Clive

 

[Don Y]

On 12/28/2021 10:22 AM, Clive Arthur wrote:

On 28/12/2021 01:52, Don Y wrote:
On 12/27/2021 3:12 PM, whit3rd wrote:
On Sunday, December 26, 2021 at 6:51:58 AM UTC-8, Don Y wrote:
On 12/26/2021 5:45 AM, Clive Arthur wrote:

Snowballs.
Snowballs would be excellent! But, I\'m not sure how easy it
would be to make a machine that could form them, ...

OK, then, marshmallows.

*That* is a possibility! They used to (?) make (toy) \"marshmallow guns\".
So, clearly, you can propel a marshmallow over *some* distance. I\'m
not sure if 20 ft would be in that realm.

I can\'t imagine them being very \"lively\" when it comes to bouncing
(esp if lofted high). And, unlike beanbags, they\'d be pretty easily
compressed/run over/etc. so litter wouldn\'t be an immediate concern.


snip

Sorbo rubber balls don\'t bounce much and are fairly dense. It\'s possible
they\'re called something else in the US.

I think the win with the marshmallows is that they don\'t put up much
resistance when it comes to retaining their shape. So, any \"litter\"
would likely just be squashed (unless there was a significant amount
concentrated in one area).

Anything solid would need to be easily \"deflected\" from its resting
place.

I\'ve got marshmallows on my shopping list when I next venture out.
Having never been a fan of them as a confection, my memory/impressions
of them isn\'t very detailed -- other than general size/shape/squishiness.

I also see lots of \"marshmallow shooters\" when I do a web search
so that suggests there must be *some* repeatability to their use
as a projectile (though I imagine they are intended to hit an
upright target so any force greater than that which would be
required to reach the target would be treated as equivalent to that
minimum force).