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High-power rocketry is a hobby similar to model rocketry. The major difference is that higher impulse range motors are used. The National Fire Protection Association (NFPA) definition of a high-power rocket is one that has a total weight of more than 1500 grams and contains a motor or motors containing more than 62.5 grams of propellant or rated at more than 160 Newton-seconds of total impulse.
High-power rockets are defined as rockets flown using commercially-available motors ranging from H to O class. In the U.S., the NFPA1122 standard dictates guidelines for model rocketry, while NFPA1127 is specific to high-power rockets. In most U.S. states NFPA1122 has been adopted as part of the legal code. A smaller number of states use NFPA1127.
The Tripoli Rocketry Association and the National Association of Rocketry are the major sanctioning bodies for the hobby in the USA, providing member certifications, and criteria for general safety guidelines.
In Australia, there are two nationwide HPR organizations. The Australian Rocketry Association has ten clubs with launch sites in the Australian Capital Territory, South Australia, Western Australia, Queensland, and Victoria. The Tripoli Rocketry Association has four prefectures in Australia, with launch sites in Victoria, New South Wales, Queensland and Western Australia.
In Canada, the Canadian Association of Rocketry - L'Association Canadienne De Fuséologie is appointed as regulator for the hobby.
In New Zealand, the controlling body for rocketry is the New Zealand Rocketry Association or NZRA
In South Africa, the controlling body for rocketry is SAASA, the South African Amateur Space Administration.
In the UK the British Model Flying Association or BMFA is the governing body with United Kingdom Rocketry Association or UKRA acting as the High Power Association for Motor flights classed as H and above.
Unlike model rocketry, certification is required by the governing organizations in order for individuals to fly high powered rockets. The certification system is standardized across the hobby and governing organizations. There are three levels of certification, each allowing the user to fly successively larger motors. In the USA (TRA and NAR):
Level 1: H, I
Level 2: J, K, L
Level 3: M, N, O and beyond
Note: In Canada, the Canadian Association of Rocketry  has an additional step to Level 4, which is equivalent to the US Level 3. Level 1 is H motor, Level 2 is I motor and CAR Level 3 and 4 is the same as U.S. Level 2 and 3, respectively. Due to a change by the Board of Directors upon recommendation from the RSO Committee, all hybrids are considered High Power.
In order to gain certification an individual needs to demonstrate his ability to fly a rocket within the given power range of the level he is seeking successfully. For example, if an individual desires to gain a Level 1 certification he must successfully fly a H-I motor in an appropriately sized rocket. This is also true for Level 2 and 3 certification with the added requirements that, for Level 2 a test be successfully passed and for Level 3 the build be documented and overseen by an individual that is already of Level 3 certification. These requirements vary slightly between NAR and Tripoli, but are very close in both organizations.
The UKRA offer a certification programme in the UK similar to the USA. The process is very similar to that of the USA.
Level 1 : H, I
Level 2 : J, K, L
Level 3 : M, N, O
Range Safety Officer (RSO)
The requirements for level 1 certification are a successful test flight with a level 1 size motor in front of a UKRA certified RSO.
A level 2 certificate requires a successful test flight with a level 2 sized motor witnessed by an RSO. The candidate also has to pass a multiple choice written exam set by the UKRA.
A level 3 candidate has to submit a detailed written report on their rocket to the UKRA Safety and Technical Committee, who will also examine the rocket prior to launch. After the written report has been approved and the rocket inspected, the candidate must then complete a successful test flight to obtain his level 3 certification.
Any UKRA member can apply to be a Range Safety Officer. The candidate must pass the level 2 written exam and pass an interview. An RSO can be either a Model Rocket RSO, Level 1 RSO, Level 2 RSO or Level 3 RSO, depending on the certification level he holds. The RSO can only act at launches involving rockets of his level of certification or lower.
Third party indemnity insurance is only provided by the British Model Flying Association (BMFA) and is included as part of the membership package. High Power Rocket fliers must hold the appropriate certificate for the size of motor that they are flying, and abide by the UKRA safety rules, for insurance to be valid.
The UKRA recognise the certification from the following National Organisations, who also recognise the UKRA certifications.
High-power rocket designs can vary widely as do anticipated altitudes and performance but altitudes of 10,000 ft and velocities in the supersonic ranges are not uncommon. A combination of (often) larger mass and higher apogees may require sophisticated recovery systems. High-power rockets are frequently flown with sophisticated electronic devices used for recording flight data (altitude, velocity, acceleration/deceleration, G-forces) and for deploying recovery methods or devices.
High-power rockets are constructed from materials such as phenolic resin, fiberglass, carbon fiber, and other composite materials and plastics. Motor casings are normally machined aluminium with ablative phenolic or paper liners and are reloadable, i.e. can be used multiple times.
High-power rockets are predominantly powered by commercially-available APCP-based motors or nitrous oxide-based hybrid motors. Experimental Propulsion is also the source of propulsion for many high-power rockets.
Motors for High-Power Rocketry are "H" and above. The lettered naming system is a standard in the hobby in which successive letters double the delivered impulse of the previous letter. Each letter also has a range of impulses under which a given motor can be classified.
Black powder motors, typically manufacturered by companies such as Estes and Quest are classed as fireworks, and subject to few purchase restrictions in the UK, the main restriction being the purchaser must be over 18 years old. The motors are available up to class D in the UK and only suitable for low power model rockets.
Ammonium Perchlorate is classed as an explosive by the UK Health and Safety Executive, so Ammonium Perchlorate Composite Propellant (AP) motors formerly required the purchaser to have an Explosives Licence and Recipient Competent Authority Transfer Document (RCA). A Registered Store Certificate was also required if the purchaser wanted to store the motors rather than purchase them at the flying event and use them immediately.
The UKRA has negotiated an exemption so that model rocket fliers can obtain some AP motors in limited quantities without the need for an explosives licence. Since the 4th December, 2007, model rocketeers have been able to purchase AP motors with a net weight less than 1 kg of propellant without an Explosives Licence. They can also store motors up to a total net weight of 5 kg without needing an Explosives Licence or Registered Store Certificate. They will still require an RCA document. This can be obtained from the UK HSE by writing an appropriate letter to them requesting an exemption for model rocket motors. This document is currently issued free of charge, although this may change.
A motor with 1 kg of propellant is a K impulse motor, so model rocketeers can now fly level 2 models without the need for an explosives license, however an RCA is still required. This relaxation in the regulations has made mid and high power rocketry much more accessible in the UK.
In model rocketry, a parachute, streamer or other recovery device or method deploys at apogee, but high-power rockets may employ more complex recovery systems since altitudes can be much higher than their counterparts. In a high-power rocket, an altimeter or electronic timer may deploy a drogue parachute (which stabilizes the rocket in descent) or a controlled freefall (where the fore and aft sections are merely separated by a tether or umbilical cord, often made of tubular nylon). These recovery events can be brought about by small explosive charges (black powder or Pyrodex) or pressurized gasses (e.g., CO2). At an altitude predetermined by the hobbyist, an altimeter deploys a main parachute that slows the rocket to a safe recovery speed. The most common varieties of altimeter use accelerometers, barometric sensors or a combination of both.