Everything You Need to Know to Start
Making Fireworks Rockets
By Ned Gorski
This is Your Audience
This is a Big Honkin' Fireworks Rocket
This is Your Audience on Fireworks Rockets!
RocketsObviously, in this introduction to rockets, we won't be discussing military rockets, which have a long and rich history. Neither will we be discussing rockets designed for space exploration, which we'll leave to NASA.
But leaving those aside, there is a wide variety of rocketry that folks can and do explore for purely recreational purposes. Such rockets include model rockets, amateur rockets, high-powered rockets, and fireworks rockets. The purpose of this article is to discuss fireworks rockets. However, in order to distinguish fireworks rockets from the other types, we will briefly mention and define each of these.
The following rocketry classifications and descriptions come from Wikipedia:
- Model rocketry: "A model rocket is a small rocket capable of being launched by anybody, to generally low altitudes (usually to around 100-500 m (300-1500 ft) for a 30 g (1 oz.) model) and recovered by a variety of means."
- "Amateur rocketry, sometimes known as amateur experimental rocketry or experimental rocketry is a hobby in which participants experiment with fuels and make their own rocket motors, launching a wide variety of types and sizes of rockets. Amateur rocketeers have been responsible for significant research into hybrid rocket motors, and have built and flown a variety of solid, liquid, and hybrid propellant motors."
Launch of an Amateur Rocket
- "High-power rocketry is a hobby similar to model rocketry, with the major difference being that higher impulse range (i.e., more powerful) motors are used. The National Fire Protection Association (NFPA) definition of a high-power rocket is one which has a total weight of more than 1500 grams and contains a motor or motors containing more than 62.5 grams of propellant or more than 160 Newton-seconds."
A High-Power Rocket Being Readied for Launch
In his 1947 book Pyrotechnics, George Weingart uses the term "Sky Rockets" to refer to fireworks rockets.
From Wikipedia: "A skyrocket is a type of firework that uses a solid (fuel) rocket motor to rise quickly into the sky. At the apex of its ascent, it is usual for a variety of effects (stars, bangs, crackles, etc.) to be emitted. Skyrockets use various stabilization techniques to ensure the flight follows a predictable course, often a long stick attached to the side of the motor, but also including spin-stabilization or fins."
Launch of a Large Fireworks Rocket by Dan Thames,
2-Inch Whistle Motor, 10-Inch Ball Shell Heading
Photo by Mark Stallings
Fireworks Rockets In-DepthExcept for the project on homemade Estes®-type rocket motors, mentioned above, the focus of this article and at Skylighter is on fireworks rockets. The description of fireworks rockets will be expanded upon in this section.
The purpose of fireworks rockets is entertainment. The rocket motor is often designed to provide an entertaining visual and/or audible effect, such as a long glittering or spark tail, or a loud ascending whistle.
Additionally, often the rocket motor is fitted with a "heading," which creates a traditional fireworks display--for example, a loud report, a shell burst of stars, or a display of other types of fireworks inserts--at the end of the rocket's powered flight.
Anatomy of a Fireworks Rocket
Cross Section of a Typical Fireworks Rocket
The diagram above shows the elements of a typical fireworks rocket. The top of the rocket is on the right, and the bottom of the rocket is on the left.
This rocket has three main components.
The rocket motor consists of the paper tube (case), which has a clay nozzle built into the bottom of it to direct the rocket exhaust. It is packed with fuel to provide thrust ("thrust fuel") and a delay ("delay fuel") after the thrust fuel is exhausted. The top of the tube is partially closed by a clay bulkhead which has a "passfire" hole built into it.
The second component is the rocket stick, which is attached to the side of the rocket motor and extends to the left. The rocket stick provides stabilization to the rocket at lift-off and in flight.
Finally, attached to the top of the rocket motor is the heading containing stars and burst. The heading is responsible for the fireworks display seen in the sky as the rocket reaches the top of its climb.
The functions of these various components will be explained in greater detail below.
Size Does MatterFireworks rockets range in size from the smallest of bottle rockets up through the monster rocket shown in the photo above.
Although it might not seem so at first glance, there is a very big difference between, say, a 3/8-inch ID "magnum" bottle rocket and a 1/2-inch ID rocket motor. Calculating the cross-sectional areas of the two sizes of motor-tubes, and also the total volumes of the tubes, the fact is that a 1/2-inch motor is between 2 and 2.5 times as large (in terms of volume) as a 3/8-inch ID motor. This is easy to see in the next photo.
Homemade Fireworks Rockets
The large skyrockets you can buy at your local fireworks store typically have 1/2-inch ID motors. A 1/2-inch black-powder motor can carry a heading of between 1 and 2 ounces into the air. That's the same weight as a spherical or cylindrical, festival-ball-sized, aerial fireworks shell.
The handmade rockets shown above are very nice, real rockets. Yet they are small enough to be suitable for flight in almost any area where rockets from the fireworks store could safely be displayed.
Moving up to 3/4-inch ID motors from the 1/2-inch ID ones yields another 2 to 3 times increase in motor volume. So, inside diameter alone is not a good indicator of how much larger one rocket motor is than another.
Half-inch, black-powder rockets are a great place to start, and I, personally, enjoy the heck out of making them to this day. They are small enough that they can be made quickly and don't use huge amounts of materials. But they are large enough to really be impressive. They provide that black-powder-rocket "whoosh" as they launch, and they're able to carry a nice payload of stars or other garnitures into the air.
These rockets allow plenty of opportunity to gain experience while enjoying experimentation, research and development, and plain old fireworking fun. You can lift headings the size of consumer fireworks reloadable/artillery shells far into the air with these nice rocket motors. Since they do not require the use of loud black powder lift charges, they are much quieter than mortar-fired shells. And, as opposed to a simple mortar-launched aerial shell, the rocket heading is preceded by the nice rocket-motor "tail" display on the way skyward.
Finally, after the heading displays, there is no heavy fallout falling back to the ground.
Traditional Fireworks Rocket Size NomenclatureHalf-inch ID rocket motors are traditionally called 4-ounce motors. Quarter-pounder rockets? What does that mean? Well, the answer is, not much.
It's a relatively long and complicated story which Barry Bush relates in detail in the fireworks chapter of Pyrotechnics by Alexander Hardt. Over the past several hundred years, an evolution occurred in the nomenclature used to describe rockets. That resulted in 1/2-inch ID rockets being referred to as "4-ounce" rockets in the US. Similar terminology is used to describe other sizes of rockets (see table below).
These designations have nothing to do with the actual weight of the rocket motors, their payload carrying capacity, or their thrust. They are simply arbitrary, meaningless designations which can be difficult to remember at times, and which really only pertain to black-powder rockets. As a result, many rocketeers simply refer to their rockets by the motor's ID nowadays.
But old habits and traditions are not quick to die, so here is a table of the traditional black-powder rocket designations used in the US, and the corresponding motor ID's and common tube-lengths (may vary slightly from one maker to another):
Rocket Motor Sizes and Designations
|9 inches or longer
You can see from the table that the length of the tube is approximately 10 times the tube's ID. This can vary a little from one maker to another, though.
On the small end, there are 1/4-inch ID and 3/8-inch ID "bottle rocket" tubes and tooling available as well, and we could call these "1-ounce" and "2-ounce" motors.
Turbo-Pyro 3/8-Inch-ID "Magnum Bottle Rocket"
On the large end, some rocketeers, with the necessary space to fly them, make larger fireworks rockets too, sometimes referring to them as "30-pound" or "60-pound" motors.
30 and 60-Pound Fireworks Rockets
Photo by Tom Calderwood
Types of Fuel Used in Fireworks RocketsThe traditional fuel for fireworks rockets is black powder, and it is still used extensively. Black powder produces that characteristic "whooshing" sound, and long tail of charcoal sparks that most fireworks enthusiasts associate with fireworks rockets.
Launch of a 3/4-Inch Black-Powder Rocket
But perhaps the biggest advancement in fireworks rocketry in the past 50 years has been the development of different fuels, other than the traditional black-powder fuel.
"Whistle fuel" is used in whistling rockets, and also in conjunction with other types of fuel as a powerful booster.
Launch of a 3/4-Inch Whistle Rocket, with Report
"Strobe" fuel, used with a whistle-fuel booster, produces one of the most striking visual, and especially audible, effects of any fireworks rocket. A brightly flashing tail is accompanied by loud "popping." It almost sounds like an incoming helicopter.
3/4-Inch Strobe Rocket Taking Off
Rockets with brilliantly colored tails can be made by using color-producing fuels. Such rockets often use whistle fuel as a booster.
Powerful "hybrid fuels" can be made by mixing granulated black-powder fuel with granulated whistle fuel, and pressing that fuel mixture in motor tubes.
Other fuels such as zinc-sulfur fuel, and "sugar" or "candy" fuel--to mention only a couple--have also been developed. So you can see that starting with just the rocket motor, there is plenty of room for creativity and experimentation with fireworks rockets.
Overview of Fireworks Rocket Construction MethodsRocket tooling, made up of a spindle and rammers (or "drifts"), is used to form the rocket nozzle and form the hollow-cored fuel charge inside the rocket tube.
Two Different Sets of 1/2-Inch Black-Powder Rocket Motor Tooling
Cross-Section of a Cored Black-Powder Motor
In a traditionally made black-powder rocket motor the hard clay nozzle is formed by ramming powdered clay into the bottom of the tube. This is done using the tooling, a mallet and a sturdy ramming post for a base. The spindle forms the central hole in the nozzle.
The fuel in a fireworks rocket must also be compacted into a solid mass (called a "grain") in order to ensure that burning of the fuel proceeds in a controlled fashion. This process is called "consolidation." In the case of our black-powder rocket, fuel consolidation is also achieved using the tooling, mallet and ramming post. The fuel, made of potassium nitrate, charcoal, and sulfur, is rammed into the paper tube above the nozzle in a series of small "increments" to ensure consistency.
A clay bulkhead with a passfire hole is rammed on top of the finished fuel grain, and finally, a heading is added at the top end of the rocket.
The motor in the diagram above would be classified as a "black-powder fueled, nozzled, core-burner" motor.
An "end-burner" motor would be made in a very similar fashion, but with a very short spindle which only penetrates through the rammed nozzle. The fuel grain of an end-burner black-powder motor has no core going up into the center of its fuel grain.
A Short Spindle for End-burner Motors (with fuse inserted in it)
Nozzled versus Nozzleless MotorsWhereas the above mentioned motors have clay nozzles, there are black-powder motors which do not use a clay nozzle. These "nozzleless black-powder" motors have a more powerful black-powder fuel consolidated around a core-forming spindle, without any clay nozzle at the bottom end.
The whistle and strobe motors shown in the previous sections do not use clay nozzles either. They typically do have a core formed up into their fuel grain.
Methods of Consolidating Rocket FuelAs mentioned above, traditional black-powder motor construction employs hand ramming with a mallet and a solid ramming post.
Tools for Hand-Ramming Rocket Motors
But more sensitive fuels like whistle or strobe composition should not be subjected to the shock associated with ramming. Also it is sometimes desirable to achieve higher densities of compaction. In these cases, mechanical or hydraulic presses are used to press increments of the fuel into the paper tubes.
A Modified 1-Ton Arbor Press for Pressing Rocket Motors
A Homemade Hydraulic Fireworks Press
Means of Stabilizing a RocketAt the time of launch and during its flight, a rocket must be stabilized to keep it headed in the desired direction, usually straight upwards. There are three different ways to stabilize a rocket:
- Stick stabilization, as shown in the photos above of rocket motors with sticks attached to them.
- Fin stabilization, as shown in the photos above of the various rocket with fins on the rocket bodies.
- Spin stabilization, as employed in a type of fireworks rocket called a "stinger missile." In these rockets, prior to launch, the rocket motor is spun by exhaust gasses emitting from a tangential spin-hole in the side of the motor-tube.
Spin-Up and Launch of a Spin-Stabilized Stinger Missile
Rocket Heading TypesAnd, finally, after the rocket motor lifts the rocket skyward and has done its job, a heading that has been installed on the motor's top can display. This can be as simple as a report, or as complex as the 10-inch ball shell on the large rocket shown earlier in this article.
A simple star, or small cluster of them, can be taped to the top of the rocket motor, and they will signify when the rocket's powered flight is completed.
A "bag shell" heading can be constructed of a few turns of kraft paper on the motor's end, filled with black-powder burst charge and a handful of stars.
Or, any complex aerial ball shell or cylinder shell imaginable can be installed on the rocket motor to create a complex aerial fireworks display at the top of the rocket's flight.
Summary of A Rocket's NomenclatureCombining all these variables will yield a particular rocket's complete description, which will include:
- The size of the rocket: motor-tube ID.
- The type of fuel or fuels used in the rocket motor's construction, along with a description of the desired tail effect.
- The type of fuel consolidation used when making the motor: hand rammed or pressed.
- Whether the motor has a nozzle or not: nozzled or nozzleless.
- Whether the fuel grain has a core in it or not: cored (or core-burner) or end-burner.
- Method of rocket stabilization: stick, finned, or spin-stabilized (stinger).
- Type of heading installed on the rocket, and its intended effects.