Model Rockets

All About Rocket Models – History of Rocket Models

All about rocket models

Rocket models, also known as low-power rockets, are a small type of rocket designed to reach low altitudes (usually around 100–500 m for a 30 g model) and saved by various methods.

According to the United States National Agency for Rocketry (NAR) Safety Regulations, model rockets are made of paper, wood, plastic, and other light materials. The regulation also includes motor use, launch site selection, launch methods, placement of the launch pad, design, and opening of the rescue system as well as other rules. Since the early 1960s, the text of the Model Rocket Safety Regulation has been prepared thanks to many model rocket kits and engines. Despite the combination of highly flammable substances and high-speed pointed objects inherent in nature, model rocketry has historically been proven to be a very safe hobby and has been credited for being an important inspiration for future scientists and engineers.


History of Rocket Models

In the early thirteenth century, the Chinese turned black powder-operated objects, which were formerly used only for entertainment, into weapons of war. These primitive rockets of the Chinese, called ‘fire arrows’, were fired from a kind of launchpad in the form of a slingshot. There was a hole at one end of a closed pipe filled with black powder for the release of hot gases resulting from burning. In addition, these rockets had a long stick that served as a balance and guidance system. Advances in rocket design, albeit on paper, were made only a few centuries later. In 1591, Belgian Jean Beavie identified multi-stage rockets and made their drawings as an important idea. The multi-staging practice, which was the placing of two or more fuel cells on top of each other and the gradual firing, provided a practical solution to the problem of getting rid of the rocket’s gravity. While many small rockets were produced after years of research and trials, the first modern model rocket and, more importantly, the model rocket engine was designed in 1954 by Orville Carlisle, a licensed pyrotechnic specialist, and model airplane enthusiast brother Robert. In fact, they designed the engine and rocket to use in Robert’s flight-based lessons with rocket power. But, Orville later read the article on Popular Mechanics magazine by G. Harry Stine, about the safety problems experienced by young people trying to build their own rocket engines. With the launch of Sputnik, many young people often faced sad results when trying to build their own rocket engines. Some of these attempts have been dramatized in the movie October Dream. Carlisles thought that the engine design they realized was a safe way for a new hobby and could be marketed, and some examples in January 1957. He sent it to Stine. Stine, a shotgun security officer at the White Sands Missile Range, designed a safety manual for this activity based on his experience in the shooting area, after making and flying the models.

The first American model rocket company was Model Missiles Incorporated (MMI), opened in Denver, Colorado by Stine and others. The rocket models owned by Stine were made by a local firework company whose engines were recommended by Carlisle. But reliability and delivery issues forced Stine to get in touch with others. Stine eventually reached Vernon Estes, the son of a local firework manufacturer. Estes founded Estes Industries in 1958 in Denver, Colorado, and developed a high-speed automatic machine for MMI to manufacture solid fuel model rocket engines. The machine, nicknamed “Mabel”, produced low-cost engines with higher reliability than the need for Stine. Stine’s business paused, and this made Estes stand alone in the engine market. Later, in 1960, rocket models began to market as kits, and Estes dominated the market over time. Estes moved his company to Penrose, Colorado in 1961. Estes Industries was acquired by Damon Industries in 1970. The company continues its operations at Penrose today.

Although rivals such as Centuri and Cox were established and closed in America in the 1960s, 1970s, and 1980s, Estes continued to control the American market by offering discounts to schools and schools such as the Boy Scouts of America to help hobbies develop. In recent years, companies like Quest Aerospace have taken a small portion of the market, but Estes remains the main source of rockets, engines, and launch equipment for low and medium-power rocketry today. Estes produces and sells Rocket Engines.

In the mid-1980s, since the arrival of high-power rocketry, that is, from class G to class J (each letter indicates that the energy of the previous letter has twice the energy), several companies shared the market for larger and more powerful rockets. In the early 1990s, Aerotech Consumer Aerospace, LOC / Precision, and Public Missiles Limited (PML) took the leadership position, although many engine manufacturers have consistently provided larger and much higher costs. Companies such as Aerotech, Vulcan, and Kosdon have become very popular during launch during this time, as their high-power rockets have always broken Mach 1 and reached altitudes above 3,000 m. Over a period of nearly five years, the largest engine ever produced reached the N class. Class N engine is equal to the power of more than 1,000 combined D engines and can easily air rockets weighing 50 kg. Special bespoke engine makers continue to work outside of today’s market, often creating propelling fuels that combine colored flame (common colors such as red, blue, and green), black smoke, and spark, as well as special projects involving extreme altitude experiments sometimes over 17,000 meters, P, Q and they even make very large R-class engines.

The reliability of high-power motors was a major problem in the late 1980s and early 1990s due to catastrophic engine failures that frequently occur in class L or higher engines. With costs over $ 300 per engine, it became clear that it was necessary to find a cheaper and more reliable remedy. Refillable engine designs introduced by Aerotech (metal casings filled with propellant grains screwed in the front-rear covers and screwed-in propellants) have been very popular within a few years. These metal containers should only be cleaned and filled with propellant and a few discarded parts after each launch. The cost of “refilling” is usually half the size of a single-use engine. Although catastrophe (CATOs) due to refillable engines still occurs occasionally (mostly due to poor assembly techniques applied by the user), the reliability of the launchers has increased significantly.

It is possible to change the thrust profile of solid propellant engines by selecting different propellant designs. Since the thrust force is proportional to the burning surface area, the propellant pellets can be shaped to produce a very high thrust force for a few seconds or to have a low thrust for an extended period of time. Depending on the weight of the rocket and the maximum speed threshold of the hull and fins, appropriate engine selections can be used to maximize performance and the chance of successful recovery.

Aerotech, Cesaroni, Rouse-Tech, Loki, and other companies have standardized refillable engine sizes around a common group. As long as there are customers who want great flexibility in their hardware and refill options, there will always be an ambitious group of custom-made engine makers that create unique designs and sometimes offer them for sale.

Engines of Rocket Models

Most engines of small rocket models are single-use engines, whose bodies are made of cardboard and light clay with molded nozzles, gradually ranging from A to G. In rocket models, a commercially produced black powder rocket engine is used. These engines are tested and approved by the National Association of Rocketry, Tripoli Rocketry Association (TRA), or the Canadian Association of Rocketry (CAR). Although the driving force range of black powder motors is between 1 / 8A and E, several F black powder motors have also been built.

Because the black powder is very fragile, physically very large black powder model rocket engines are usually up to E-class. If a large black powder engine falls to the ground or is exposed to hot/cold cycles many times (eg exposed to high temperatures in a closed vehicle), propellant fractures may occur in the propellant. Since these fractures increase the surface area of ​​the propellant when the engine is ignited, the propellant burns much faster and greater pressure is created inside the engine than the normal internal combustion chamber pressure. This pressure may exceed the durability of the paper envelope and cause the engine to explode. An exploding engine can cause damage from a simple engine pipe tear to the model rocket or a violent rushing (and sometimes ignition) of the rescue system in the hull pipe.

Therefore, composite propellants made of ammonium perchlorate, potassium nitrate, aluminum powder, and a rubbery binder content in a hard plastic envelope are used in rocket motors with a power level higher than D and E. This type of propellant, similar to that used in the solid fuel support engines of the space shuttle, is not as fragile as black powder but increases engine reliability and resistance to propellant fuel breakage. The driving force of these engines varies between D and O. Composite engines produce more propulsion per unit weight (specific propulsion) than black powder motors.

Model rocket engine

Anatomy of a simple model rocket engine. A typical engine is about 7 cm. long.
1. Nozzle;
2. Envelope;
3. Propellant;
4. Delay powder;
5. Launching powder;
6. Top cover

Refillable composite propellant engines are also available. Installation of propellant grains, o-rings, and washers (for controlling expanded gases) and retarding grain and launch powder into commercially designed aluminum engine envelopes with the screwed or special plug-in (sealed cover) ends, commercially required by the user. it is produced. The advantage of the refillable engine is its cost: First, the main envelope is reusable, so the cost of the refillable engine is significantly less than that of the same driving force single-use engines. Secondly, the assembly of large composite engines is labor-intensive and difficult to automate; the fact that this work is taken over the customer results in a decrease in cost. Refillable engines are available from D to O class.

Engines are ignited by electrical energy. This firing occurs by pushing the electric match consisting of a short pyrogen-coated nichrome, copper or aluminum bridged wire into the nozzle and fixing it in place with non-combustible paper, rubber band, plastic plug or masking tape. On the propellant, there is a tracking delay powder which is essentially non-thrust but generates smoke while the rocket slows down and the bow-shaped flight path it draws. When the delay powder completely burns, it fires the launch powder used to open the rescue system.

Motor classification

Model rocket engines manufactured by companies such as Estes Industries and Quest Aerospace are stamped with a code (such as A10-3T or B6-4) that specifies a lot about the engine.

The smallest motor is 6 mm. Quest Micro Maxx engines. Although Apogee Components produced 10.5 mm micro motors, it stopped production in 2001. While Estes produces standard A, B, and C motors with a diameter of 18mm and a length of 70mm, it also produces mini-size motors with a diameter of 13mm and a length of 45mm. Also, there are bigger black powder motors of C, D, and E class; These 24 mm diameter motors are either 70 (C and D motors) or 95 mm (E motors) in length. Some disposable motors such as F and G are 29 mm in diameter. High power motors (usually refillable) are available in 38mm, 54mm, 75mm, and 98mm diameter.

First letter

The letter at the beginning of the code indicates the engine’s total driving force range (usually measured in newton-seconds). Each letter in consecutive alphabetical order has twice the force of the previous letter. This does not mean that the total propulsion force of a “C” engine is twice the total propulsion force of a “B” engine. While “B” engines are in the range of 2.51-5.0 N-s, C engines are only in the range of 5.01-10.0 N-s. Also, “¼A” and “½A” symbols are used. For more detailed information on letter codes, see. Model rocket engine classification.

For example, the total propulsion force of a B6-4 engine manufactured by Estes-Cox Corporation is 5.0 N-s. The total thrust of a C6-3 engine produced by Quest Aerospace is 8.5 N-s. d.

First figure

The number after the letter indicates the average thrust of the engine in newton units. It can be used to launch a heavier model, as a higher thrust force will cause higher take-off acceleration. Within the same letter class, a higher average thrust also refers to a shorter burning time (eg, if a B6 engine does not burn for as long as a B4 engine burns, the initial thrust force will be greater than a B4 engine). Engines with different first digits in the same letter class are generally based on rockets of different weights. For example, in order for rockets to reach high altitudes, a light rocket needs to have a lower initial thrust and a longer burning time, while a heavy rocket must have more initial thrust to be separated from the launch pad.

Last number

The last figure is the delay time in seconds between the end of the push phase and the firing of the launch powder. Black powder motors, the last digit of which ends with zero, do not have lag time or launch powder. The absence of a delay element and top cover in these engines allows for forwarding the burning and burning of the material to ignite an upper stage engine. For this reason, such engines are generally used as first stage engines in multi-stage rockets.

The code “P” indicates that the engine is “plugged”. In this case, there is a top cap, even if there is no launching powder. It is used in rockets that do not need a standard rescue system, such as a plug-in engine, small rollers, or R / C glider rockets. Plug motors are also used in large rockets using electronic altimeters or timers used to activate the rescue system.

Composite engines usually have a letter or combination of letters indicating that different propulsion fuel formulations (producing colored flame or smoke) are used in the engine of that manufacturer after the delay time.

Refillable engines

Aerotech Refillable engine shells. From left to right: 24/40, 29 / 40-120, 29/60, 29/100, 29/180, 29/240
Refillable rocket engines are defined in the same way as the disposable model rocket engines described above. However, refillable rocket motor casings have additional impressions in the form of diameter/propulsion, which will define both the diameter and the maximum total propulsion force. After that, there are a number of letters indicating the propellant type. However, not all companies that produce refillable engine systems use the same notation for their engines.

An Aerotech consumer aerospace refillable rocket engine designed to suit the maximum total thrust force of 60 newton-second 29-millimeter-diameter sleeves has 29/60 marking in addition to the thrust definition.

However, Cesaroni Technology Incorporated (CTI) uses a different coding in its engines. In these engines, there is a number that represents the diameter of the motor in millimeters, followed by “Pro”. For example, the Pro38 engine is a 38mm diameter engine. After that, there is a new character sequence. In this form of arrangement, first the driving force in newtons-seconds, followed by the motor classification, the average driving force in newton, finally the dash and the delay time in seconds. For example, the Pro29 110G250-14 is a G engine with a propulsion force of 110 Ns, a push force of 250 N, and a delay time of 14 seconds.

  Class Total Driving Force (Metric Standard)
1/4A 0.313-0.625 N•s
1/2A 0.626-1.25 N•s
A 1.26-2.50 N•s
B 2.51-5.0 N•s
C 5.01-10 N•s
D 10.01-20 N•s
E 20.01-40 N•s
F 40.01-80 N•s
G 80.01-160 N•s
Model Rocket Motors

Rocket engines

From the left,
13mm A10-0T,
18mm C6-7,
24mm D12-5,
24mm E9-4,
29mm G40-10.

Model Rocket Motor Cases

Aerotech Refillable engine shells.

From left to right:
29 / 40-120,


The driving force of a model engine (thrust-area under the time curve) is used to determine the class of the engine. The motors are divided into classes from 1 / 4A to 0 and beyond, covering a driving force range from 0 to 40 Ns (Newton * seconds). Black powder rocket engines are usually only produced up to class E. The upper limit of each class is twice the upper limit of the previous class. In “Model Rocketry” rockets only G and lower power engines are used. [18] Rockets using engines with greater thrust are considered high power rockets.

The values ​​obtained from Estes rocket engines are used in the table motor performance examples on the side.

For mini black powder rocket engines (13 mm diameter), the maximum thrust force is 5 – 12 N, the total thrust force is 0.5 – 2.2 Ns and the burning time is 0.25 – 1 second. For ‘normal size’ Estes rocket engines (18 mm diameter), there are three classes: A, B and C. The maximum thrust force of Class A engines with a diameter of 18 mm is 9.5 – 9.75 N, the total thrust force is 2.1 – 2.3 Ns and the burning time is 0.5 – It is between 0.75 seconds. 18 mm. The maximum thrust force of Class B motors in diameter is 12.15 – 12.75 N, the total thrust force is 4.2 – 4.35 Ns and the burning time is between 0.85 – 1 second. The maximum thrust force of Class C engines with a diameter of 18 mm is 14 – 14.15 N, the total thrust force is 8.8 – 9 Ns and the burning time is 1.85 – 2 seconds.

In addition, Estes’ large (24 mm diameter) rocket engines have 3 classes: C, D, and E. The maximum thrust force of Class C engines with a diameter of 24 mm is 21.6 – 21.75 N, the total thrust force is 8.8 – 9 Ns and the burning time is 0.8 – 0.85. between seconds. The maximum thrust force of Class D engines with a diameter of 24 mm is 29.7 – 29.8 N, the total thrust force is 16.7 – 16.85 Ns and the burning time is 1.6 – 1.7 seconds. The maximum thrust force of Class E engines with a diameter of 24 mm is 19.4 – 19.5 N, the total thrust force is 28.45 – 28.6 Ns and the burning time is 3 – 3.1 seconds.

Several independent sources have published measurements that show that Estes model rocket engines do not meet the thrust characteristics that they often release.

Model rocket recovery methods

The model and high-power rockets are designed to be safely rescued and fly over and over again. The most common recovery methods are parachute and lane recovery methods. The parachute is usually thrown out by the engine’s launch powder along with the nose cone. The parachute attached to the nose cone is pulled out by the nose cone and the rocket makes a soft landing.

Featherweight recovery

The simplest approach in this rescue method, which is suitable only for the smallest rockets, is to allow the rocket to fall back to earth after firing the engine launch powder. This rescue, which is slightly different from the somersault, is based on disrupting some system balances to prevent the rocket from entering the ballistic trajectory on the way back to earth.

Tumble recovery

Another simple approach, which is suitable for small rockets or large rockets with a cross-sectional area, is that the rocket is rolled back to earth to fall backward. As it fell to the ground, it is not safe to use a tumble recovery method on any rocket that will enter the ballistic orbit in a stable manner. To prevent this, the launch gunpowder is used to shift the engine behind the rocket in some similar rockets. In this way, the center of gravity is moved behind the pressure center and the rocket becomes unstable.

Nose-shot recovery

Another very simple recovery technique used in the early models of the 1950s and sometimes in modern examples is nose-to-head recovery. The engine’s launching powder disengages the nose cone of the rocket (usually attached to the body by a shock cord made of rubber, Kevlar rope, or other types of cord), disrupting the rocket’s aerodynamic profile. This causes increased drift and reduces the rocket’s flight speed to a safe speed for landing. Nose-throw recovery is only suitable for very light rockets.

Parachute / strip

Although the parachute/lane approach is often used in small model rockets, it can also be used with large rocket models, taking into account the size of the parachute depending on the size of the rocket. The force generated by the engine’s throwing powder is used in opening the parachute or throwing the strip out. The parachute is attached to the trunk by parachute ropes either directly or indirectly by a shock cord to the nose cone attached to the trunk. Usually, a piece or a ball of fireproof paper or material is placed inside the body before the parachute or ribbon. This allows the launch powder to launch fireproof material, parachute, and nose cone without damaging the rescue equipment. Air resistance slows the rocket’s fall. Recovery results in a smooth, controlled, and soft landing.

Glider recovery

In glider rescue, the launch powder either opens a wing profile (wing) or separates a glider from the engine. If done properly, the rocket/glider will go into a spiral glide and return safely to the ground. In some cases, radio-controlled rocket gliders are brought back to the ground in many ways by a pilot, such as the flight of R / C model aircraft.

Helicopter rescue

Launching gunpowder, in one of several methods, opens helicopter-shaped pals, and the rocket lands on the ground, descending back by autorotation. Helicopter rescue usually occurs when the recoil of the engine creates pressure and the nose cone is thrown out. In this section, there are rubber bands connected to the nose cone and three or more pads. Rubber bands pull the pallets out of the rocket body. Paller provides enough drift for a soft landing. Some rockets use fins as well as the blades. In this type of rocket, it throws a pipe throwing gunpowder with dislocated tabs outside the rocket that holds the fins in place during the launch of the rocket. Then, the tab releases the rubber band – after the fins appear, the helicopter rotates around its axis until it takes the position.

Using a device

Aerial photography

Cameras and camcorders can be launched with rockets to take pictures and images during flight. Astrocam, Snapshot film camera, Oracle, or the latest model Astrovision digital cameras (all of them are Estes) or model rockets equipped with their home-made counterparts can be used to take aerial photographs.

These aerial photographs can be taken in a variety of ways. Passive methods such as string pulled by mechanized timers or flaps that respond to wind resistance can be used. Microprocessor controllers can also be used. However, the rocket’s speed and motion can cause blurry photos. Very fast and variable lighting conditions occurring at rocket points from the ground to the sky can also have an impact on video quality. Video frames can also be combined to create panoramas. The model rocket cameras must be protected from the impact of the ground, as parachute systems may be prone to failure or malfunction.

In addition, short digital videos can be recorded with rockets. There are two models, Astrovision and Oracle, which are widely used in the market and both are produced by Estes. Astrocam can also capture three digital still images with a higher resolution than the video, shooting 4 seconds of video during the flight (16 seconds in its introduction, actually playing and playing 4 seconds of video). B4-4, B6-4, and C6-5 engines are used in the Astrovision rocket. Although Oracle is a more expensive option, it can attract most or all of the flight and recovery. Generally, “D” engines are used in this rocket. It is longer than the Oracle Astrovision rocket and is better known in the market. However, “key fob cameras” are also quite common and can be used on almost any rocket without significantly increasing drift.

There are also experimental homemade rockets that use two methods for video shooting and carry cameras on them.

Device placement and testing

Model rockets with electronic altimeters can report or record electronic data such as maximum speed, acceleration, and altitude. The two methods of determining these quantities are a) an accelerometer and a timer run backward as acceleration-speed and altitude b) to find the height, a barometer on the rocket with the timer (from the pressure difference in the ground and the pressure difference in the air) determines the duration of the velocity and acceleration measurements. works forward.

Rocket modelers often experiment with rocket sizes, shapes, loads they carry, multi-stage rockets, and rescue methods. Some rockets also make scale models of large rockets, spaceships, or missiles.

High power rocketry

Main article: High power rocketry

As with low power model rockets, high power rockets are made of light materials. Unlike model rockets, high-power rockets will typically experience a speed limit of Mach 1 (340 m / s) and 3,000 m. Strong materials such as fiberglass, composite materials, and aluminum are often required to withstand the high stresses created by the altitude on it. Due to the potential risk to other aircraft, contact with relevant authorities is usually required.

High power rockets operate with large engines from the H class to O class and weigh 1,500 grams or more at take-off. To reduce the cost of the flight, its engines are almost always refillable rather than disposable. Using an altimeter or accelerometer to determine when the engines fire or parachutes open, rescue, and/or multi-stage firing can be initiated by small on-board computers.

High power model rockets can carry large loads containing devices such as cameras and GPS units.

Differences from model rocketry

A high power rocket must meet at least one of the following criteria:

  • The weight of the rocket must be more than 1,500 grams.
  • The engine used must contain more than 125 grams of propellant.
  • The driving force of the engine used should be more than 160 Newton-seconds (class H or above) or, if a multi-stage engine is
  • used, the total impulse should be more than 320 Newton-seconds.
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