| A reloadable motor is a motor designed to be | | | | grains, a delay grain, and a cardboard liner. |
| used multiple time by inserting new | | | | The propellant grains are inserted into the |
| propellant and replacing other expendable | | | | liner. The delay grain is ignited when the |
| components. A reloadable motor usually | | | | motor ignites and burns slowly. When it burns |
| consists of an aluminum tube (a special | | | | through, the motor ejection charge, if used, |
| aluminum alloy) and closures to hold the | | | | is ignited. When the recovery system is |
| nozzle on one end and to seal the other end. | | | | deployed through motor ejection, black powder |
| Some manufacturers have the closures screw | | | | is installed in the forward closure's |
| into the motor case. Others use other | | | | "ejection well". The delay grain goes inside |
| techniques to secure the closures, like a | | | | the forward closure. |
| snap ring. | | | | |
| | | | APS motor forward closure APS Forward Closure |
| Pictured is a Dr. Rocket/Aerotech reloadable | | | | |
| motor. On the left is the aft closure, which | | | | This is the forward (top) closure, showing |
| closes the rear of the motor and holds in the | | | | the ejection charge well. |
| nozzle, the motor case and on the right the | | | | |
| forward (top) closure. (Dr. Rocket is a | | | | Black powder is placed into the well, and |
| licensed manufacturer of Aerotech's motor | | | | cover with some masking tape to hold it in, |
| technology.) | | | | when motor ejection is used to deploy the |
| | | | parachute. A small hole is in the bottom of |
| The aft closure is slightly larger than the | | | | the well so that the black powder is in |
| case. When the motor is inserted into the | | | | contact with the top of the delay grain. When |
| motor mount tube the lip keeps the motor from | | | | the delay grain burns through the black |
| moving up through the motor mount tube and | | | | powder is ignited. |
| rocket when thrusting. | | | | |
| | | | When an electronic mechanism, such as |
| Motor cases are available in different | | | | altimeter, is used to activate the ejection |
| diameters and lengths to allow for propellant | | | | charge, a plugged forward closure may be used |
| kits of different size and total energy. | | | | if offered by the motor manufacturer. A |
| | | | plugged closure is like the pictured one but |
| A propellant reload kit contains one or more | | | | the top is solid, having no ejection well or |
| propellant grains, and other components that | | | | hole. |
| are replaced each time the motor is used. | | | | |
| Most motors use one or more silicone O-rings | | | | APS delay installed |
| that must be replaced each time the motor is | | | | |
| used. Some manufacturers use a plastic nozzle | | | | This picture shows an APS forward closure |
| that must be replaced for each motor use. | | | | with the delay grain inserted into its |
| Others use a graphite nozzle that is usually | | | | chamber. |
| good for about 20 flights before replacement | | | | |
| is needed. | | | | The motor must be ignited from the top, not |
| | | | near the nozzle. The igniter must be fully |
| AeroTech RMSâ„¢ Reload Kit H123 Reload | | | | inserted into the motor. |
| Kit | | | | |
| | | | Motors must be cleaned between uses. |
| AeroTech/Dr. Rocket | | | | Insufficient cleaning, or reusing old parts |
| | | | can result in hot gas leakage and motor and |
| This is an AeroTech reloadable motor reload | | | | rocket destruction. Motors can be field |
| kit, which can be used with either an | | | | cleaned using foil wrapped, wetted towels |
| AeroTech RMSâ„¢ or Dr. Rocket reloadable | | | | which are sold under several brand names in |
| motor. | | | | grocery and other stores. |
| | | | |
| This particular kit, an H-123, contains two | | | | The silicone O-rings must have a light coat |
| individual propellant grains, a cardboard | | | | of lubricant ("grease") applied to them when |
| motor case liner, rubber O-rings, a | | | | they are installed. The lubricant allows the |
| single-use plastic nozzle, a delay grain and | | | | closures to slide over the rings without |
| components, and assorted seals. | | | | crimping or tearing them when the closures |
| | | | are installed and tightened. Following the |
| The propellant grains are inserted into the | | | | manufacturer's instructions. The O-rings |
| liner, and the liner is then inserted into | | | | should have only a light coating - just |
| the motor case. | | | | enought to give them a sheen. Too much |
| | | | lubricant can result in motor failure. Too |
| APS reloadable motor showing components APS | | | | much lubricant on O-rings near the forward |
| Motor | | | | closure, where the ejection delay grain is |
| | | | located, can result in failure of the delay |
| Advanced Propulsion Systems | | | | grain to ignite if the lubricant gets on the |
| | | | faces of the grain. (Dirty hands can also |
| Shown here is an Advanced Propulsion Systems | | | | cause the delay grain to become contaminated |
| (APS) reloadable motor. The motor consists of | | | | with lubricant.) If the delay grain fails to |
| a case, forward closure, aft closure (next to | | | | burn and motor ejection is used to deploy the |
| the nozzle) and graphite nozzle. The nozzle | | | | recovery system the rocket will crash and |
| can be used for about 20 flights before | | | | crumple, hopefully not damaging any person or |
| replacement. | | | | other property. |
| | | | |
| APS reloadable motor reload kit APS Reload | | | | The particular type of lubricant used |
| | | | (petroleum jelly, grease with Teflon, etc.) |
| An APS reloadable motor reload kit is shown | | | | is not nearly as important as the correct |
| here. It contains an O-ring, three propellant | | | | application of the lubricant. |