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A model rocket is a small rocket designed to reach low altitudes (e.g., for a model) and be recovered by a variety of means.
According to the United States National Association of Rocketry (NAR)'s Safety Code, model rockets are constructed out of lightweight and non metallic parts. The materials are typically paper, cardboard, balsa wood or plastic. The code also provides guidelines for motor use, launch site selection, launch methods, launcher placement, recovery system design and deployment and more. Since the early 1960s, a copy of the Model Rocket Safety Code has been provided with most model rocket kits and motors. Despite its inherent association with extremely flammable substances and objects with a pointed tip traveling at high speeds, model rocketry historically has proven to be a very safe hobby and has been credited as a significant source of inspiration for children who have eventually become and .
The first American model rocket company was Model Missiles Incorporated (MMI), in Denver, Colorado, opened by Stine and others. Stine had model rocket engines made by a local fireworks company recommended by Carlisle, but reliability and delivery problems forced Stine to approach others. Stine eventually approached Vernon Estes, the son of a local fireworks maker. Estes founded Estes Industries in 1958 in Denver, Colorado and developed a high-speed automated machine for manufacturing solid model rocket motors for MMI. The machine, nicknamed "Mabel", made low-cost motors with great reliability, and did so in quantities much greater than Stine needed. Stine's business faltered and this enabled Estes to market the motors separately. Subsequently, he began marketing model rocket kits in 1960, and eventually, Estes dominated the market. Estes moved his company to Penrose, Colorado in 1961. Estes Industries was acquired by Damon Industries in 1970. It continues to operate in Penrose today.
Competitors like Centuri and Cox came and went in America during the 1960s, 1970s, and 1980s, but Estes continued to control the American market, offering discounts to schools and clubs like Boy Scouts of America to help grow the hobby. In recent years, companies like Quest Aerospace have taken a small portion of the market, but Estes continues to be the main source of rockets, motors, and launch equipment for the low- to medium-power rocketry hobby today. Estes produces and sells black powder rocket motors.
Since the advent of high-power rocketry, which began in the mid-1980s with the availability of G- through J-class motors (each letter designation has up to twice the energy of the one before), a number of companies have shared the market for larger and more powerful rockets. By the early 1990s, Aerotech Consumer Aerospace, LOC/Precision, and Public Missiles Limited (PML) had taken up leadership positions, while a host of engine manufacturers provided ever larger motors, and at much higher costs. Companies like Aerotech, Vulcan, and Kosdon were widely popular at launches during this time as high-power rockets routinely broke Mach number and reached heights over . In a span of about five years, the largest regularly made production motors available reached N, which had the equivalent power of over 1,000 D engines combined, and could lift rockets weighing with ease. Custom motor builders continue to operate on the periphery of the market today, often creating propellants that produce colored flame (red, blue, and green being common), black smoke and sparking combinations, as well as occasionally building enormous motors of P, Q, and even R class for special projects such as extreme-altitude attempts over .
High-power motor reliability was a significant issue in the late 1980s and early 1990s, with catastrophic engine failures occurring relatively frequently (est. 1 in 20) in motors of L class or higher. At costs exceeding $300 per motor, the need to find a cheaper and more reliable alternative was apparent. Reloadable motor designs (metal sleeves with screwed-on end caps and filled with cast propellant slugs) were introduced by Aerotech and became very popular over the span of a few years. These metal containers needed only to be cleaned and refilled with propellant and a few throw-away components after each launch. The cost of a "reload" was typically half of a comparable single use motor. While catastrophes at take-off (CATOs) still occur occasionally with reloadable motors (mostly due to poor assembly techniques by the user), the reliability of launches has risen significantly.
It is possible to change the thrust profile of solid-propellant motors by selecting different propellant designs. Since thrust is proportional to burning surface area, propellant slugs can be shaped to produce very high thrust for a second or two, or to have a lower thrust that continues for an extended time. Depending on the weight of the rocket and the maximum speed threshold of the airframe and fins, appropriate motor choices can be used to maximize performance and the chance of successful recovery.
Aerotech, Cesaroni, Rouse-Tech, Loki and others have standardized around a set of common reload sizes such that customers have great flexibility in their hardware and reload selections, while there continues to be an avid group of custom engine builders who create unique designs and occasionally offer them for sale.
A primary motivation for the development of the hobby in the 1950s and 1960s was to enable young people to make flying rocket models without having to construct the dangerous motor units or directly handle explosive .
The NAR and the TRA successfully sued the US Bureau of Alcohol, Tobacco, Firearms and Explosives(BATFE) over the classification of Ammonium Perchlorate Composite Propellant (APCP), the most commonly used propellant in high-power rocket motors, as an explosive. The March 13, 2009 decision by DC District court judge Reggie Walton removed APCP from the list of regulated explosives, essentially eliminating BATFE regulation of hobby rocketry.
| Anatomy of a basic black-powder model rocket motor. A typical motor is about long. 1. Nozzle 2. Case 3. Propellant 4. Delay charge 5. Ejection charge 6. End cap]] |
Most small model rocket motors are single-use engines, with cardboard bodies and lightweight molded clay nozzles, ranging in impulse class from fractional A to G. Model rockets generally use commercially manufactured black-powder motors. These motors are tested and certified by the National Association of Rocketry, the Tripoli Rocketry Association (TRA) or the Canadian Association of Rocketry (CAR). Black-powder motors come in impulse ranges from 1/8A to F.
[[File:G64 rocket motor components.jpg|thumb|left|300px|alt=G64-10W Reload| The components of a motor made by Aerotech Consumer Aerospace for a 29/40-120 casing.
1. Motor Casing
2. Aft Closure
3. Forward Closure
4. Propellant Liner
5. Propellant Grains (C-Slot Geometry)
6. Delay Insulator
7. Delay Grain and Delay Spacer
8. Black Powder Ejection Charge
9. Delay O-Ring
10 & 11. Forward and Aft O-Rings
12. Forward Insulator
13. Nozzle
14. Electric Igniter]]
The physically largest black-powder model rocket motors are typically F-class, as black powder is very brittle. If a large black-powder motor is the upper stage motor of a rocket that exceeds the maximum recommended takeoff weight, or is dropped or exposed to many heating/cooling cycles (e.g., in a closed vehicle exposed to high heat or a storage area with inconsistent temperature control), the propellant charge may develop hairline fractures. These fractures increase the surface area of the propellant, so that when the motor is ignited, the propellant burns much faster and produces greater than normal internal chamber pressure inside the engine. This pressure may exceed the strength of the paper case and cause the motor to burst. A bursting motor can cause damage to the model rocket ranging from a simple ruptured motor tube or body tube to the violent ejection (and occasionally ignition) of the recovery system.
Therefore, rocket motors with power ratings higher than D to F customarily use composite propellants made of ammonium perchlorate, aluminium powder, and a rubbery binder substance contained in a hard plastic case. This type of propellant is similar to that used in the solid rocket boosters of the Space Shuttle and is not as fragile as black powder, increasing motor reliability and resistance to fractures in the propellant. These motors range in impulse from size A to O. Composite motors produce more impulse per unit weight (specific impulse) than do black-powder motors.
Reloadable composite-propellant motors are also available. These are commercially produced motors requiring the user to assemble propellant grains, and washers (to contain the expanding gases), delay charge and into special non-shattering aluminum motor casings with screw-on or snap-in ends (closures). The advantage of a reloadable motor is the cost: firstly, because the main casing is reusable, reloads cost significantly less than single-use motors of the same impulse. Secondly, assembly of larger composite engines is labor-intensive and difficult to automate; off-loading this task on the consumer results in a cost savings. Reloadable motors are available from D through O class.
Motors are electrically ignited with an electric match consisting of a short length of pyrogen-coated nichrome, copper, or aluminum bridgewire pushed into the nozzle and held in place with flameproof wadding, a rubber band, a plastic plug or masking tape. On top of the propellant is a tracking delay charge, which produces smoke but in essence no thrust, as the rocket slows down and arcs over. When the delay charge has burned through, it ignites an ejection charge, which is used to deploy the recovery system.
Model rocket motors mostly don't offer any sort of thrust vectoring, instead just relying on fins at the base to keep the vehicle aerodynamically stable. Some rockets do however have thrust vectoring control (TVC) by gimbaling the motor itself rather than the nozzle. This is done on some rockets built by many model rocket builders, such as Joe Barnard of BPS.space.,
| 0.313-0.625 N·s |
| 0.626-1.25 N·s |
| 1.26-2.50 N·s |
| 2.51-5.0 N·s |
| 5.01-10 N·s |
| 10.01-20 N·s |
| 20.01-40 N·s |
| 40.01-80 N·s |
| 80.01-160 N·s |
Figures from tests of Estes rocket motors are used in the following examples of rocket motor performance.
For miniature black powder rocket motors (13 mm diameter), the maximum thrust is between 5 and 12 N, the total impulse is between .5 and 2.2 Ns, and the burn time is between .25 and 1 second. For Estes ‘regular size’ rocket motors (18 mm diameter), there are three classes: A, B, and C. The A class 18 mm motors have a maximum thrust between 9.5 and 9.75 N, a total impulse between 2.1 and 2.3 Ns, and a burn time between .5 and .75 seconds. The B class 18 mm motors have a maximum thrust between 12.15 and 12.75 N, a total impulse between 4.2 and 4.35 Ns, and a burn time between .85 and 1 second. The C class 18mm motors have a maximum thrust from 14 – 14.15 N, a total impulse between 8.8 and 9 Ns, and a burn time between 1.85 and 2 seconds.
There are also 3 classes included in Estes large (24 mm diameter) rocket motors: C, D, and E. The C class 24 mm motors have a maximum thrust between 21.6 and 21.75 N, a total impulse of between 8.8 and 9 Ns, and a burn time between .8 and .85 seconds. The D class 24 mm motors have a maximum thrust between 29.7 and 29.8 N, a total impulse between 16.7 and 16.85 Ns, and a burn time between 1.6 and 1.7 seconds. The E class 24 mm motors have a maximum thrust between 19.4 and 19.5 N, a total impulse between 28.45 and 28.6 Ns, and a burn time between 3 and 3.1 seconds. Estes has also released a line of 29mm black powder E and F motors. The 29mm E produces 33.4 Newton-seconds of total impulse over a 2.1 second burn, and the F produces 49.6 Newton-seconds over a 3.45 second burn.
Several independent sources have published measurements showing that Estes model rocket engines often fail to meet their published thrust specifications.Penn, Kim and William V. Slaton, Measuring Model Rocket Engine Thrust Curves, The Physics Teacher – December 2010 – Volume 48, Issue 9, pp. 591. An Investigation into the Combustion and Performance of Small Solid-Propellant Rocket Motors M.G. Carter. University of New South Wales at the Australian Defence Force Academy. 2008. Measuring thrust and predicting trajectory in model rocketry M. Courtney and A. Courtney. Cornell University Library. 2009.
The Quest Micro Maxx engines are the smallest at a diameter of 6mm. The company Apogee Components made 10.5mm micro motors, however, those were discontinued in 2001. Estes manufactures size "T" (Tiny) motors that are 13 mm in diameter by 45 mm long from 1/4A through A class, while standard A, B and C motors are 18 mm in diameter by 70 mm long. C, D, and E class black-powder motors are also available; they are 24 mm in diameter and either 70 (C and D motors) or 95 mm long (E motors). Estes also produces a line of 29mm diameter by 114mm length E and F class black powder motors. Larger composite propellant motors, such as F and G single-use motors, are also 29mm in diameter. High-power motors (usually reloadable) are available in 29mm, 38mm, 54mm, 75mm, and 98mm diameters.
For instance, a B6-4 motor from Estes-Cox Corporation has a total impulse rating of 5.0 N-s. A C6-3 motor from Quest Aerospace has a total impulse of 8.5 N-s.National Association of Rocketry web site:
A "P" indicates that the motor is "plugged". In this case, there is no ejection charge, but a cap is in place. A plugged motor is used in rockets that do not need to deploy a standard recovery system such as small rockets that tumble or R/C glider rockets. Plugged motors are also used in larger rockets, where electronic altimeters or timers are used to trigger the deployment of the recovery system.
Composite motors usually have a letter or combination of letters after the delay length, indicating which of the manufacturer's different propellant formulations (resulting in colored flames or smoke) is used in that particular motor.
An Aerotech reload designed for a 29-millimeter-diameter case with a maximum total impulse of 60 newton-seconds carries the designation 29/60 in addition to its impulse specification.
However, Cesaroni Technology Incorporated (CTI) motors use a different designation. They first have "Pro" followed by a number representing the diameter of the motor in millimeters, for example, a Pro38 motor is a 38mm diameter motor. After this, there is a new string of characters such that the impulse in is first, followed by the motor classification, the average thrust in newtons, followed by a dash, and the delay time in seconds. For example, a Pro29 110G250-14 is a G-motor with 110 Ns of impulse, 250 N of thrust, and a 14-second delay.
Some rockets (typically long thin rockets) are the proper proportions to safely glide to Earth tail-first. These are termed 'backsliders'.
The first commercially available system was the Estes CAMROC in 1965. This system used a 1.5 inch round film negative held in a large pill-shaped camera body with the lens facing forwards. It would take a single photograph after apogee as the rocket deployed its parachute. The hobbyist would then send the negatives back to Estes for developing and printing.
The second system was also released by Estes in 1970. Created by Mike Dorfler, the CINEROC held 20 seconds of Super 8mm film that ran at 30 fps, making for a slow-motion effect. Like the CAMROC negatives, these special movie cartridges needed to be shipped back to Estes to be processed.
In 1979, Estes released the Astrocam 110, the first single frame camera rocket that took multiple single shot pictures (one per flight) using standard Kodak 110 cartridge film. Unlike its CAMROC predecessor, it could use color film, and did not require sending the film back to Estes for processing. It did require asking the processor to 'flip' the negative before printing, as the camera used a mirror to take its pictures. Otherwise, you were directed to hold prints up to a mirror to see them in the correct attitude. Through the 1980s and into the early 2000s, the Astrocam 110 was revised and updated, originally as a kit where you built the camera, which became one with a pre-built camera, then an Almost Ready to Fly model such as the Astrocam RTF and finally the renamed Snapshot RTF. By the mid 2000s, these models had been retired, as the first digital video cameras started to appear on the market. With Kodak ending 110 film production, only specialty film producers make the ASA400 film needed for these cameras, such as the Austrian based Lomography Company.
In 2005 the Oracle Video Rocket, and in 2007 the AstroVision digital/video camera were released by Estes. Both systems were capable of recording a flight from start to finish, but required downloading after each flight, as expandable memory had not been incorporated into them. The AstroVision did have a snapshot mode, so it could do more than a single flight and take multiple pictures, but movie mode was a single take before needing to be attached to a laptop. Both models were discontinued by 2010. A major reason for this was the advent of the 'Key-Fob camera' - many of which were more powerful, lighter and easier to attach to any rocket, and did not need a specific model to do so, and had expandable memory in the form of Mini SD cards, and were much less expensive. These devices also have the advantage of rechargeable batteries, and since they were built on the same plug-and-play technology Flash Drives use, do not need any extra drivers installed into a computer for them to work. In 2020, Estes brought out a new Key-Fob based camera, which now bears the Astrocam name. As of 2024, two versions can be found - a full rocket kit whose nose cone has a mount for the fob, and the Universal Astrocam, which has the fob along with a holding mount that allows for the camera to ride other models.
In the area of higher powered rocketry, there are also experimental homemade rockets that include onboard video cameras, with multiple methods for shooting videos. One is to transmit a signal down to a receiver, like in the BoosterVision series of cameras. The second method for this is to record it on board and be downloaded after recovery, the method employed by the Estes cameras listed above. (Some experimenters use the Aiptek PenCam Mega for this, the lowest power usable with this method is a C or D Motor).
Rocket modelers often experiment with rocket sizes, shapes, payloads, multistage rockets, and recovery methods. Some rocketeers build scale models of larger rockets, space launchers, or missiles.
High-power rockets are propelled by larger motors ranging from class H to class O, and/or weigh more than 3.3 lbs or 1,500 at liftoff. Their motors are almost always reloadable rather than single-use, in order to reduce cost. Recovery and/or multi-stage ignition may be initiated by small on-board computers, which use an altimeter or accelerometer for detecting when to ignite engines or deploy parachutes.
High-power model rockets can carry large payloads, including cameras and instrumentation such as GPS units.
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