Rocket motors

There are 3 types of motor used in rocketry.

  • BP motors - Black powder or BP, uses ordinary gunpowder like the stuff used in fireworks
  • AP motor - Ammonium perchlorate-based mixture, generally known as an AP motor
  • Hybrid motor - normally using nitrous oxide as the oxidiser and plastic as the fuel.

Our motors

Here at the University, we have a range of motors available. As well as the black powder motors, which are all single-use, we have Cesaroni Pro38 one-grain (G impulse), two-grain (H) and five-grain (J) cases, plus a Congreve I case, all 38mm diameter.

We also have a micro-hybrid (D impulse, working on nitrous oxide capsules), Sky Ripper G-69 and H-78, RATT I-80 (all 29mm) and a Pentamax J/K 54mm set, plus a Sky Ripper 38mm J on order, all hybrids. We have a RATT Works L/M combination hybrid motor on order for Level 3 flights.

We are therefore able to fly on every impulse up to K (over 1280 Ns), and when the RATT arrives will have motors for L and M as well. Motors of H and I impulse require Level 1 certification, J, K and L require Level 2. M impulse and above requires Level 3.

rocket motors 

Bottom to top: Pentamax K hybrid motor (54mm diameter), Sky Ripper G hybrid
(29mm diameter), D12 BP motor (24mm diameter), Pro38-G AP case (38mm diameter)

Motor costs

Apart from the smallest model rockets, all amateur rocketry is quite expensive. A BP motor ranges from around £1 for an A to about £6 for an E motor, AP motors range from around 20-25 pounds for a G reload plus 20-30 pounds for the case to almost 300 pounds per launch for an M reload plus 200 pounds for the case.

Hybrid motors cost around 35 pounds for a G motor, plus six pounds per reload plus perhaps a couple of pounds for the nitrous oxide. An M-class motor costs around 300-400 pounds to buy, and each reload varies from 60-100 pounds. Nitrous oxide for this size motor would be 15-20 pounds per flight.

In addition, the ground-support equipment for a hybrid motor costs around 500-600 pounds, more if gaseous oxygen is needed. Apart from the BP motors, the motor is the item you most want to get back, so it is common to attach the parachute to the motor or motor mount - it's also the strongest part of the rocket. If you were wondering what the eye bolt on the front of the Pentamax was for, now you know...