SpudFiles

MrCrowley wrote:Since I don't have long between finishing university for the semester and the estimated launch date, I've been thinking about every minor detail of the launch to insure I account for it.

A very important/critical detail for a successful test firing that you have not shown or mentioned yet is where the MiniBoys center of gravity is.

Load it up with your talcum powder/chalk and then determine the balancing point. Measure that point to the nose tip.

32 mm or less would be optimal!

Just thought i'd mention, if the projectile lands in the sand it will get lost for sure. I was sitting in a beach chair (at the beach) and simply dropped my wedding ring right next to me. Figured i'd just lean down and pick it up, and I did, but it took about 20 minutes to find the friggin thing.
Will you be able to chrony the projectile?

You could go buy a cheap knock off metal detector for 50 or so US dollars. I had one capable of finding a spoon about 2 feet deep. Miniboy could probably be found up to 3 or so feet deep. At that shallow of an angle It shouldn't go very deep at all.

Mr.Tallahassee wrote:At that shallow of an angle It shouldn't go very deep at all.

I bet it would go pretty deep. Think of the penetration depth of its namesake

You'd probably go insane from all the other metal items on a beach before you find it though.

Or you could dish out a lot of money for a metal detector with a radar style screen, one of those would find anything. and yes they do exist, a family friend has one and when I was small I used to go around on the beach digging up bits of washed up ship.

I will point out that the optimal angle is more like 45-40 degrees. More like 45 because of the low Cd.

ramses wrote:I will point out that the optimal angle is more like 45-40 degrees. More like 45 because of the low Cd.

45 degrees in a vacuum.

In the real world however, spin stabilised projectiles tend to achieve maximum range below that angle, while finned projectiles go above it.

[url=http://www.frfrogspad.com/miscellb.htm]fr frog[/url] about the 120mm US APFSDS round wrote:The extreme range of the M829A2 is close to 70 miles when fired at 55 degrees elevation.

I think there is a more elegant solution to projectile recovery.

That's actually a good idea

jackssmirkingrevenge wrote:

ramses wrote:I will point out that the optimal angle is more like 45-40 degrees. More like 45 because of the low Cd.

45 degrees in a vacuum.

In the real world however, spin stabilised projectiles tend to achieve maximum range below that angle, while finned projectiles go above it.

[url=http://www.frfrogspad.com/miscellb.htm]fr frog[/url] about the 120mm US APFSDS round wrote:The extreme range of the M829A2 is close to 70 miles when fired at 55 degrees elevation.

I agree. The angles I used were from horisontal. Obviously, its less than 45 (more horisontal). I think your referece measured from the vertical for some reason.


As a sidenote, my friend's dad is a super arrogant engineer. He refuses to accept that 45 degrees is only optimal in vacuume (he thinks it applies in atmosphere as well). He also has mentally replaced F=A*P with F=P/A in his head. Any suggestions on how to break through with him? I've tried dimensional analysis for F=AP, but it's not working

Also, he keeps arguing that analog computers are superior to digital ones. And that wankel engines are more efficient than piston engines.

[/rant]

He may have a point with Wankel engines, but they're an engineering nightmare. I say just use hydrogen fuel cells, efficiency blows away combustion engines.

If he's that convinced... I fear there is no hope.

Jack's reference measured from the horizontal. An M892A2 round has a high enough muzzle speed and low enough drag that it goes high enough for the reduced air density to make a difference. A similarly extreme example of the effect can be seen in the Paris Gun of WW1.

Your friend's dad is not an engineer if he's incapable of such basic dimensional analysis, or the intuitive understanding of low-altitude trajectories. I suggest euthanasia.

Fnord wrote:I think there is a more elegant solution to projectile recovery.

Haha I like it

Similar ideas had been discussed but we never got as far as writing on a .jpg image


On another note, what about making a solenoid inside the projectile and trying to pick up the location via interference? Considering the solenoid would be quite small, inside a metal casing and buried several feet under sand I highly doubt this idea is even remotely feasible .

That should do the trick! Pick up the frequency on a handheld radio and there it is. 8)

ramses wrote:As a sidenote, my friend's dad is a super arrogant engineer. ]

What KIND of engineer? Sanitation engineer perhaps?