What is High Power Rocketry?

While model rocketry has been around for over forty years, high power rocketry (or HPR as it's sometimes called) is a relative newcomer to the scene. From its beginnings in the early eighties as an adult alternative to the smaller 1lb and under model rocket, it has become a recognized, safe addition to the hobby, approved and embraced by both the Tripoli Rocketry Association (the pioneers of HPR) and the National Association of Rocketry. As with model rocketry, safety codes have been written by both Tripoli and the NAR to help insure the continued safe enjoyment of the hobby.

A simple definition of a high power rocket would be any model that weighs more than 1500gm (3.3lbs) at lift-off and/or has a motor with more than 4.4oz of propellant. But there are many more differences that set these birds apart from their model rocket cousins and place their construction and flying squarely in the realm of adult hobbies:

Larger models require larger motors. While an F motor may get that 2lb model rocket off the ground, it won't do anything for one that weighs 5lbs. But larger rockets and motors, although as safe to store and handle as model rocket motors, require a higher degree of knowledge and maturity in their use. That's why G motors may only be purchased by people 18 years and older, and the purchase of H motors and above also require membership in and certification by either the NAR or TRA.

Larger models require stronger materials and construction methods. A model rocket with a thin cardboard tube and balsa fins glued together with yellow wood glue will fly just fine powered by a D motor, but would disintegrate under the power of a G motor or larger. High power models require thicker body tubes, model aircraft plywood or thick plastic fins, and stronger shock cord material just to name a few differences in materials. They also require stronger adhesives such as epoxies or cyanoacrylates, and advanced construction techniques like through-the-wall fin mounts.

Larger models, if flown carelessly, could be dangerous. Just as with a 1/4 scale radio controlled airplane, the larger weight and power of a high power rocket could cause damage or injury if constructed or flown stupidly or carelessly. While it could be argued that many adults can be careless and stupid, it's also obvious that the level of maturity required by the hobby automatically restricts it to adults. Requiring membership and certification helps to insure that those enjoying the hobby will be knowledgeable and responsible.

Larger models require special waivers from the FAA, as well as larger fields and stronger launch equipment to fly.

High power rockets are similar to model rockets in that they still have nose cones, body tubes, fins, motor mounts and recovery systems. Its just that all of these parts must be many times stronger and bigger then those in model rockets. Nose cones are often made of thick plastic or fiber-glass. Body tubes are made of thick cardboard, phenolic or fiber-glass. Fins are usually model aircraft plywood, plastic or fiber-glass.

Often, the larger sizes and altitudes of high power rockets require more advanced recovery systems that include electronic timers or altimeters and separate ejection charges. Many systems will deploy a drouge chute to slow the rocket just enough to be safe, but keep it near the launch site, and then eject a larger chute at a lower altitude to allow the rocket to land softly.

While many enjoy high power rockets just for the shear size and power, many others are in the hobby for the increased payload capacity that larger rockets allow. Probably the most popular payload is some type of camera, whether its still, movie or video. All have been and continue to be flown. Other popular payloads are data gathering devices such as computers with various sensors, altimeters, ect. Serious research can and has been done with high power rockets, although most fly payloads for their own enjoyment and education.

Rocket Motors

The designation for a specific motor looks like C6-3. In this example, the letter (C) represents the total impulse of the motor, the number (6) before the dash represents the average thrust in newtons, and the number (3) after the dash represents the delay from motor burnout to the firing of the ejection charge (a gas generator composition, usually black powder, designed to deploy the recovery system). So a C6-3 motor would have between 5.01 and 10 N·s of impulse, produce 6 N average thrust, and fire an ejection charge 3 seconds after burnout.

Class
Minimum Impulse
(N·s)

Maximum Impulse
(N·s)

A

1.26

2.50

B

2.51

5.00

C

5.01

10.00

D

10.01

20.00

E

20.01

40.00

F

40.01

80.00

G

80.01

160.00

H

160.01

320.00

I

320.01

640.00

J

640.01

1,280.00

K

1,280.01

2,560.00

L

2,560.01

5,120.00

M

5,120.01

10,240.00

N

10,240.01

20,480.00

O

20,480.01

40960.00

The letter-scale continues past class-O, beyond the domain of high-power rocketry. Motors and vehicles of such size and power are generally considered the domain of amateur rocketry. (In this context, the term amateur refers to the rocketeer's independence from an established commercial or government organization.)

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What is High Power Rocketry?

"Americans Flying Rockets Are Not Terrorists!"

"Americans Flying Rockets
Are Not Terrorists!"