Frequently Asked Questions

Q1. I'm interested in setting up a club in my local area. How do I do this?
A1. Thats great news. We need more rocket clubs in the UK.
Setting up a club is quite simple really - just follow the steps below.

  • Get a group of fellow rocketry enthusiasts together - usually three as a minimum.
  • Find a launch site suitable for the size of vehicle you wish to fly.
    You can check the UKRA safety code for advice on flying size dimensions.
    Annex A of the safety code also contains the Launch Site Guidelines.
  • Let us know what you've called yourself (so we can advertise your club if you want us to)
  • If you want to formalise your club there are a few extra steps you will have to complete in order to achieve this.
    • You will need to adopt a formal constitution
    • specify roles such as chair, club sec and treasurer.
    • carry out some risk assessments to ensure you will conduct your club affairs in a safe and responsible manner

Q2. What do all the numbers mean on a rocket motor?
A2. The labelling schemes on rocket motors vary by manufacturer, however there are common labelling systems found on Aerotech, Cesaroni (CTI) and Estes motors. Each label comprises an optional total impulse (in Newton Seconds), the motor class (the letter allocation), the average thrust, an optional fuel/grain type designation, a hyphen/dash and the delay.
Examples include the Aerotech E16W-7, the Cesaroni 108G57-12A and the Estes B6-4, each described below:

  • Total impulse: Present on Cesaroni motors, absent on most other motors, this number shows the total impulse (in Newton Seconds) for the motor. This number defines the motor class as below. The motor above has a total impulse of 108Ns.
  • Motor class: Present on all known motors this single letter designates the motor class as a result of the motor's total impulse. The table below shows the total impulse designations up to M class, beyond M class requires CAA approval for all flights:
    Class Minimum impulse (Newton Seconds) Maximum impulse (Newton Seconds) Notes
    A   2.5  
    B 2.5 5 For example: Estes B6-4
    C 5 10  
    D 10 20  
    E 20 40 For example: Aerotech E16W-7
    F 40 80  
    G 80 160 For example: Cesaroni 108G57-12A
    H 160 320 URKA Level 1 certification required
    I 320 640 URKA Level 1 certification required
    J 640 1280 URKA Level 2 certification required
    K 1280 2560 URKA Level 2 certification required
    L 2560 5120 URKA Level 2 certification required
    M 5120 10240 URKA Level 3 certification required
  • Average Thrust: Present on all known motors this number shows the average thrust (in Newtons) for the motor. For conventional flights (exceptions apply) it is recommended that the average thrust of the motor be between five and ten times the mass of the full flight weight of the rocket, meaning that the average acceleration under burn will be 5-10 times the acceleration due to gravity. Specific examples are:
    Motor Average Thrust (Newtons) Average Thrust (g=9.81) Minimum rocket mass (acceleration=10g) Maximum rocket mass (acceleration=5g)
    Estes B6-4 6 612 grammes 61.2 grammes 122 grammes
    Aerotech E16W-7 16 1.63 kg 163 grammes 326 grammes
    Cesaroni 108G57-12A 57 5.81 kg 581 grammes 1.16 kg
  • Propellant type: Present on some motors (mostly Aerotech) this designation shows the propellant type for the motor. The types are heavily vendor specific and usually affect the thrust characteristics, the burn colour and the amount of smoke generated.
  • Delay: Present on all known motors this number shows the delay from motor burnout to ejection. While some motors start the delay grain burning at motor ignition all vendors are consistent with the timing of the delay being from motor burnout. The 'A' after the Cesaroni motor delay indicates that the delay is adjustable using the Cesaroni Delay Adjustment Tool.

Q3. I'd like to make my own solid fuel rocket motor. Is this allowed?
A3. It is not legal for UK rocketeers to make their own solid rocket motors.
It is illegal to manufacture any amount of explosive material (ie. rocket propellant) in the UK without a licence from the Health and Safety Executive (HSE).

Q4. I'd like to make my own hybrid rocket motor. Is this allowed?
A4. It is legal for UK rocketeers to make their own hybrid rocket motors, however severe restrictions apply: The handling of compressed gases (particularly oxidisers such as oxygen and nitrous oxide) is both dangerous and restricted. Ensure that you have completed all relevant research, training and certifications prior to handling gases in the quantities appropriate to your use. Additionally launching rockets on self-built hybrid motors will fall under the UKRA experimental guidelines and require approval by the UKRA Safety and Technical committee prior to launch. For this reason you should be able to demonstrate consistently safe flight experience on commercial hybrid motors and unquestionable understanding of hybrid motor design, thrust characteristics and safe operation of these motors before UKRA S&T will consider approving the launch.