quantities without the need for an explosives licence. Since 4 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 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. Recovery 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. See also Model rocket Amateur rocketry Sounding rocket Friends of Amateur Rocketry Delft Aerospace Rocket Engineering UCLA Rocket Project External links Argentina Asociacion de Coheteria Experimental y Modelista de Argentina (officially incorporated society). Australia Australian Rocketry Association Inc Australian Model Rocket Society Inc. Tripoli Rocketry Association prefectures Tripoli Australia - Victoria Tripoli Queensland - Queensland Tripoli Western Australia - Western Australia Tripoli NSW - New South Wales Canada Canadian Association of Rocketry - L'Association Canadienne De Fuséonautique France Tripoli France Germany / Austria / Switzerland Interessengemeinschaft Modellraketen (IMR) Netherlands Tripoli the Netherlands New Zealand New Zealand Rocketry Association (NZRA) Norway Norwegian Experimental Amateur Rocketry South Africa SAASA Spain Tripoli Spain High Power Rocketry United Kingdom United