Rocket reloadable motors

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