5-4-3-2-1…START!!  Model Rocketry is exciting, spectacular, safe and surprisingly easy to get started in. Typically, rockets are made from a thin-walled cardboard tube, fitted with a nosecone, fins and a motor tube. Want some more details?  …time for a few definitions:
Model Rocket ~ made from a cardboard body tube; plastic or balsa nosecone; 3 or 4 fins at the back and a tube to hold the model rocket motor, is all that is required.

Body Tubes & Nosecones ~ normally obtained from a hobby shop, or from a specialist supplier.

Model Rocket Motor ~ Come in packs of three, normally made by Estes Industries, in the USA. The ‘power’ – technically termed Specific Impulse – is measured in Newton seconds (Ns) and a wide range of sizes is available to boost model rockets of all shapes and sizes. Specific Impulse is the Area under a Time – Thrust curve. An easy to understand alphabetic system is used to classify motors, eg.
A = 2.5Ns       B = 5Ns          C = 10Ns       D = 20Ns etc…
Some Model Rocket Motors deliver their thrust in a short whoosh, others emit a long gentle blow. The former are best for dumpy, heavy rockets; the latter for slinky, light birds. There is a Delay Grain, a slow burning charge, which allows the rocket to coast on to apogee and this in turn, fires the Ejection Charge, which blows off the rocket’s nosecone and ejects the parachute, or streamer for a gentle descent. Motors are lit by electrical Igniters included in the same pack. NB. Model Rocket Motors are always ‘over the counter’ products and not made at home on the kitchen table!

Recovery Systems ~ normally a polythene parachute, or plastic/paper streamer, is employed to lower the rocket and spent motor safely to the ground, ready for another mission!  A length of stretchy elastic – the Shockline – is normally used to cushion the opening shock of the parachute and holds everything together.  How big should a parachute be?!? ..how small is the field; how windy is it; how heavy is the rocket. Normally err on the small side for best recovery prospects and consider using a streamer on small rockets.

Simple Launcher ~ most model rockets are launched from rigid steel wire rod, 10 or12 swg in diameter. This is held in a stable base that can be secured to the ground to avoid toppling over.

Electric Launch System ~ Model Rockets are not fired by lighting the blue touchpaper!  BMFA’s Model Rocketry Safety Code states that an electrical launch system – normally 6 or 12 volt – must be used. 5 metres of wire with crocodile clips to attach to the igniter in the motor is normally sufficient. A removable Safety Key must be incorporated into the launch system, which is only inserted in the latter stages of 5-4-3-2-1…START!  These launchers are available commercially, or can be made as a project.

     That is basically all that is needed to start. The diagrams illustrate what the subject is about, more than any words here. Good reading material includes:

• The Model Rocketry Handbook  21st Century Edition        by Stuart Lodge
  ISBN 1-85486-229-4           Special Interest Model Books

• Model Rocketry-Space Modelling by Stuart Lodge
  ISBN 1 900371 06 5            Traplet Publications

In addition to being fun, Model Rockets – or Space Models – have a great potential for use in the education of young people, across the spectrum of subjects, not just Science. A few specifics are listed below:

• Mathematics ~ use of trigonometry in the determination of Model Rocket altitudes. Linked to this is the making of rudimentary theodolites using protractors and rulers.
• Design and Technology ~ design, building and flying of simple model rockets, launchers, theodolites et al. Excellent projects to teach, develop and hone a student’s practical skills.
• Chemistry and Biology ~ the burning of a model rocket motor’s propellant – normally Blackpowder – can be used to illustrate Oxidation. More advanced, is the effect of propellant constitution on burning rate eg. Sulphur if used in Blackpowder to slow the process. Model Rockets have been employed to sample pollution around industrial sites.

Biology?!?  In years past, the full-size Space Program liked to send live animals into Space. Needless to say, the launching of any living creature must not be attempted, as the acceleration of a Model Rocket – at the very least – would cause severe stress and likely injury or death.

• Physics ~ always needs some Fizz!!  Physical concepts may be successfully illustrated by the use of Model Rockets. Let’s look at Newton’s Laws:

• Law of Inertia – a body at rest, will remain at rest; a body in motion will remain in motion with constant velocity, unless acted upon by an external force.

This may be illustrated by the launch profile of a typical Model Rocket and can encompass energy, aerodynamics – including the effects of wind – and gravity.

• Law of Accelleration – a change in a body’s motion is proportional to the magnitude of any externally applied force and in the direction of any applied force.

Once more, a launch profile is a relevant teaching aid. As the Model Rocket’s propellant burns out, the velocity decays as aerodynamic drag and gravity take effect.

• Law of Reaction – every force is opposed by an equal and oppositely directed force.

This is the principle of the Model Rocket Motor, rockets are not blown along by the smoke coming out of the back, but by a reaction force against the remaining unburned propellant.

Projects for more advanced students include Rocket Stability – the calculation of a rocket’s aerodynamic Centre of Pressure and relating this to the Centre of Gravity location, the effects of nosecone shape, rockets dimensions/mass etc. The above shows just a few of the educational concepts that may be illustrated by the use of Model Rockets.  Just a couple more things need checking out and you’re away!

Risk Assessment ~ Activities such as boosting Model Rockets in schools always need a Risk Assessment undertaking. A specimen is to be found appended and covers most eventualities.

Splashdown!!  ~ and that’s about all you need to get started.  The local hobbyshop is often a good place to source supplies. Better still, specialist dealers like Rockets & Things have an impressive range and act as consultants throughout the initial stages. Check out:
www.rocketsandthings.com

Further help may be obtained from:
Southern England Rocket Flyers (SERFs). ................email  johnharvey1@onetel.com
British Space Modelling Alliance (‘Alliance)..............email  stuart.lodge1@ntlworld.com
United Kingdom Rocketry Association (UKRA)...........web     www.ukra.org.uk
Black Knights .............................................................. email  mark_perman@blackknights.org.uk
                                                                                                dgrb@blueyonder.co.uk

SACL
31 March 2008