Importation, Purchase, storage and use of HPR engines are restricted. To be able to use HPR Engines you will need an Explosives certificate, to be able to import, buy or  store you will need a Registered Explosives store Certificate, An Explosives Certificate and a RCA, for information on these see the page on certificates.

HPR engines are in general use a composite propellant, rather than the black powder propellant of model rockets, in most cases this is an ammonium Perchlorate oxidizer, Aluminum powder fuel and polybutediene rubber  binder holding it all together. This is the propellant mixture that the Shuttle Solid Rocket Booster's use. This mix offers three times the power of a black powder motor for the same weight of fuel, this gives the HPR engines a higher thrust to weight ratio allowing for significantly larger rockets to be flown. For more detail on propellant see the propellant types page. The How a HPR Engine Works page details  how a composite Aerotech motor works.

Where as the model rocket motors were from 1/4 A to D size offering up to 20N/M of thrust the HPR sizes currently available in the UK go up to M offering up to 6240N/M of thrust.

Most of the HPR motors available in the UK are made by Aerotech, These are available in two forms single use and reloadable (RMS), The RMS system utilises an aluminium casing into which the propellant is fitted. Aerotech casings are made by Dr Rocket, Dr Rocket also sells these casings with a few differences, Price (they are cheaper), Colour red instead of black, etched markings instead of a sticker that can get in the way if you have a tight engine mount. RMS engines work out to be cheaper after the initial outlay on casings than their single use counterpart. For further information on Aerotech engines see either the Aerotech or Dr Rocket web sites.