Here is a picture of a 189-foot high building, with a pretty impressive shell exploding right behind it, suggesting that this particular shell exploded at c. 180 feet. However, that is undoubtedly an optical illusion - doubtless the shell was launched further away from the observer to give the illusion of it exploding right behind the building.
In general, about how high up does yer average show-quality (as opposed to backyard) fireworks shell actually go?
And on the subject of show-quality fireworks, how much does one of those shells actually cost? ISTR reading somewhere that Walt Disney World will provide a couple with their own private fireworks show, to follow their Disney wedding, for a mere $15,000. According to my WAG estimate of 500 shells in a 10-minute show, that works out to … math … $30 each, which seems ridiculously low, considering that the biggest backyard fireworks sell for about $100 per.
They are paying for the timing and design that goes into it, and probably some of the cost offsets insurance payments.
this place sells fireworks: Lotus Fireworks - House Assortments
A pack of six mortars will run about $40 and up. Sometimes they are not as big or fly as high as a professional show, but at a guess go about 150 feet high. Please note I am pulling that number out of my ass.
Our town puts on a professional show every year, which costs about $10,000. I tried to count how many individual fireworks there were last year, and it was surprisingly difficult (lots of things happening at once). My best guess was around 300 to 400, which meshes pretty well with what you estimated: around $30 a pop.
The bulk of the rockets blow at around 1,000 to 1,500 feet.
One would bet that they have their own in house pyrotechnic department. And as they have a fireworks show every night (possibly multiple shows), they make a LOT of shells. They also have no “middleman” to add on a profit like in the retailer’s case.
FWIW, all of the firework stores in NH run year-round “Buy one, get one free” deals, so that gives me a good indication of the profit margins on fireworks.
I know this doesn’t answer the OP but…
I’m struggling to find a decent picture, but anyone who’s seen the Hong Kong fireworks will believe, as I do, that the big ones go very, very high indeed.
The tallest building in HK is 2IFC, which is 1,362 feet high. The crysanthemum bursts at Chinese New Year in 2005, were way above all the buildings, and to my eye (though of course I could be experiencing perspective issues), had a diameter of roughly the height of the building. I’m thinking the best part of 2/3 of a mile, if not more.
:rolleyes: 
Not precise, but I remember when we were at Niagara Falls, they shot fireworks off from down by the river, and they exploded pretty much at eye level. (It was pretty neat, watching fireworks and not having to look overhead!)
Seeing as the falls are about 190 feet tall, the shells had to go at least that high.
Here’s a small picture of what I’m talking about. The building with the triangular top is Central Plaza, Wanchai (where I used to have an office), which is 1,227 feet high. Those fireworks are much higher than that.
I’d assume they were launched from a barge in the water in front of the buildings. Think you have major perspective distortion there.
Yeah, they are, and that picture certainly doesn’t do justice to the larger bursts - I admit I have misrepresented that picture.
I guess you have to be there to appreciate the scale. Also, the harbor is pretty slim at that point, yet the gap between seeing the airburst and hearing the ‘boom’ was at least a second, if not more.
One second makes it about 350 metres away.
The minimum lift height, depends on the effect in the shell, which is controlled by the size of the break charge in the shell.
A tight Peony or Chrysanthemum shell needs less lift than a more open Dahlia or Spider shell, while a multi-break shell (typically, a large shell with many small shells inside it) needs greater still. This all depends not only on the size of the shell but also on the size of the stars, bees, crossettes, or other effects in the shell. The larger the effect, the higher the shell needs to be lifted, so that the effect burns out well before it reaches the ground. Also, the larger the break charge is the further the effects will be thrown from the burst.
The maximum lift height, depends on the lift charge and maintaining a safety zone.
You can put any size lift charge under any size mortar shell, within limits. Too big a lift charge can rupture the shell, causing it to burst in the mortar tube (or worse, rupture the tube), AKA a flowerpot. Too small a lift charge and the shell can burst shortly after leaving the mortar, scattering its effects all over the ground, AKA a muzzle break (this is a classic cause of display disasters where electrical ignition is not being used).
IIRC the rule of thumb is to have a safety zone that’s twice (or even 3 times) the distance of your maximum lift height from the mortar rack. (so if you maximum lift is 100 feet then your safety zone would be 200 or 300 feet). Or,The National Fire Protection Association’s NFPA 1123 Code for the Outdoor Display of Fireworks (2006 Edition online here), minimum safe distances with no wind; for vertical mortars 70 feet per inch of mortar diameter, angled mortars 50 feet per inch of mortar diameter.whichever is greater.
Strangely there don’t seem to be any guidelines based on the intended lift height, only the size of the mortar, but it’s pretty safe to assume that the lift will never be greater than ⅓ to ½ the minimum safe distance. Big reason for this, portable mortar racks are usually deep boxes (½ to ¾ of the length of the mortar tube) filled with sand. If a flowerpot occurred in a badly maintained box, blowing out the wall of the box and knocking over the other tubes or anything else changes the angle of a tube, there is the potential that a mortar tube could end up being aimed directly at the spectators. Seeing the burst is cool, being inside the burst ain’t!
Bear in mind that the higher you launch a shell the bigger it needs to be to get the same visual effect. Even if you can safely lift a 10" shell to 350’ it might look like a 5" shell at 175’ with the only difference being neck strain! There are reasons to do that though, a visually large, complex shell might look better at a distance. So you’d aim the mortar tube away from the spectators and lift the shell to a height that maintains the visual angle of the display. This technique also lets you get different visual effects from the same sized shell, or superimpose a small shell over a larger one creating an effect similar to a Petal.
RE jjimm’s Chrysanthemum bursts at Chinese New Year. Wiki has Japanese multi-breaks up to 48" 
. That would suggest a 2,400 to 3,360 foot safe zone, SoS 1130 ft/s, so it would be easy to get a two or three second gap between seeing the burst and hearing it.
CMC +fnord!
Green Man/amateur pyro. Here’s a great site, Pyroguide, if any of the above leaves ya scratching your head (and ya didn’t click on the links!).
Damn - sounds like we located an expert!
