Introduction to rockets and model rocketr y

1. Introduction to rockets and model rocketry 3……2……1……Blastoff

2. This session with cover… • Uses of rockets • Principles behind rockets • What is a model rocket • Motors • Construction tips/why do we need to sand ? • Kits verses scratch build • Sourcing materials • Video examples

3. Uses … • Military – Blowing stuff up…No…no…no not allowed here. • Space – Yes…yes…yes dreams are made of this, however not possible for us …YET. • Scientific Research – Science is awesome. Why would we not propel awesome to Mach 5. • Hobby/Entertainment – Who would not be entertained ?

4. Principles of rocket • An object at rest or in constant motion will stay at rest or in motion unless acted upon by a force • F = ma • Every action has an opposite and equal reaction A resultant force must be exerted on a rocket for it to lift off from a launch pad (first law). The amount of thrust produced by a rocket engine will be determined by the mass of rocket fuel burnt and how fast the gas escapes the rocket (second law). The reaction, or motion, of the rocket is equal to and in the opposite direction of the action, or thrust, from the engine (third law).

5. What is a model rocket http://www.youtube.com/watch?v=86tTsPi0FPc

6. Parts Fins • Fins are crucial to a rocket as they provide a restoring force when a rocket moves off course, therefore keeping it stable and flying straight up. • This is done by providing a moment around the CG which counteracts the moment from the aerodynamic forces which act at the CP • Fins can be bought from rocket website however geometries are limited. • Buying balsa sheets then cutting them out is the best way to make custom fins. • You will need a fin template (http://www.robhouse.co.uk/rocksim/ ) to cut accurately around and you want all your fins to be identical

7. Parts Fins • Alignment – it is important your fins are all aligned and at the right distance from each other. • For scratching building I recommend making a alignment guide e.g. rolling paper round your body tube, printing one out etc • Also when your fins are glued on it is recommended to add fin fillets, this again increase strength, aerodynamics and aesthetics

8. Parts Motor mount • Motor mount hold your motor in place • Centering ring and engine block are the most crucial parts • Motors mount can be made removable, therefore interchangeable • Cluster motors can be made canted • Centering rings are best bought with their corresponding body tube. However it is possible to make your own • Model rockets come with an engine hook to stop the motor falling out and in high powered rocketry a retention system is used instead

9. Parts Shock cord • These attach your parachute and nose cone to the body plus absorb a lot of the energy when the nose pops off a avoid the nose cone or parachute detaching from the rocket. • For model rockets this is normally Kevlar cord attached to an elastic cord. • Pretty easy to get from a shop. • Make sure you attach them properly and glue all knots so they cannot come undone.

10. Parts Glue • Your model rocket is solely held together by this magical substance • Most material in model rocketry are paper based or wood so craft glue and wood glue are sufficient • However always use as directed, allowing for proper gluing time, so do not rush. • Be careful with application, too much glue adds weight and makes a rocket messy • Use the right glue at the right time. Super glue sometime is not that super

11. Parts Parachute • This amazing device returns your hard work back to earth in a relatively safe manor, the alternative is not desirable. • Size depends on weight and descent rate but 12-15 inches in diameter should do. • When attaching your parachute ensure the strings are not tangled and attachments are strong. • Always use wadding when launching, to avoid your parachute being burnt

12. Parts Launch lug • Crucial item, this is what connects your rocket to the launch pad • Do not forget it which a lot of people do. If you are using a D motor your launch lug should be a 5mm(1/4”) launch lug and below can use 3mm(1/8)” launch lugs.

13. Parts • Any magical parts of a model or high powered rocket that have mystified you before ?

14. Motors http://www.estesrockets.com/media//catalogs/Estes_2013_Catalog2.pdf

16. Motors • Class Total Impulse Total Impulse • I 320.01-640 N·s 71.93-143.83 lbf·s • J 640.01-1280 N·s 143.84-287.65 lbf·s • K 1,280.01-2,560 N·s 287.66-575.3 lbf·s • L 2,560.01-5,120 N·s 575.31-1150.6 lbf·s • M 5,120.01-10,240 N·s 1150.61-2301.2 lbf·s • N 10,240.01-20,480 N·s 2301.21-4602.4 lbf·s • O 20,480.01-40,960 N·s 4602.41-9204.8 lbf·s • Class Total Impulse Total Impulse • (Metric Standard) (Imperial Standard) • A 1.26-2.50 N·s 0.29-0.56 lbf·s • B 2.51-5.0 N·s 0.57-1.12 lbf·s • C 5.01-10 N·s 1.13-2.24 lbf·s • D 10.01-20 N·s 2.25-4.48 lbf·s • E 20.01-40 N·s 4.49-8.96 lbf·s • F 40.01-80 N·s 8.97-17.92 lbf·s • G 80.01-160 N·s 17.93-35.96 lbf·s • H 160.01-320 N·s 35.97-71.92 lbf·s

17. Types… • Sports rockets – Just for fun • Cluster rockets – Two or more engines at once • Multistage – Two or more rockets used one after the other in flight • High performance/ Competition

18. Types… • Cluster - Rockets that have more than one motor burning simultaneously. • The benefit of this is having smaller, cheaper and more easier to develop thrusters, which can the provide a larger take off thrust of a bigger engine. Clustering is suitable for when you need more thrust at liftoff to launch larger or heavier rockets. • This total liftoff thrust/impulse is equal to the sum of the thrust/impulse of your constituent motors, • Example: If you used two engines in cluster this would be equivalent to a motor that is twice as powerful but burns just as long.

19. Types… • Example: Two B6 in cluster vs Single C6 • So this would produce the same power as a C6 but in half the time therefore this would actually be equivalent to a C12 engine which does not exist. Which add a level of versatility. Consequently you could also lift double the maximum weight of a B6 or C6 with this configuration.

20. Types… • Important things when designing a cluster rockets is building you rocket strong to handle this extra power as you can effectively get the thrust of a high-powered engine with the right configuration. • Also how you design your motor mount to hold all these engines.http://www.rocketshoppe.com/info/Engine_Clusters.pdf • It is important that the thrust must be evenly balanced around the centerline of the rocket. If there is more thrust on one side your rocket will veer off course and become unstable. Additionally making the engines as close to the centerline as possible, therefore if one motor fails the rocket will not loop dangerously near the ground. • https://www.youtube.com/watch?v=-ZzpPY4gMkQ

21. Types… • Cluster

22. Types… • Multistage – Rockets that use more than one engine which in succession. • The benefit of this is to achieve a high altitude because each stage is jettison so the last stage is very light and can coast for a long time. • There are two ways to stage a rocket, direct and indirect staging. • Direct staging is used for black powered motors, the lower stage engines ignites the upper stage. This is relatively simple process and design once you understand how the staging works and ensure your rocket is stable http://www.apogeerockets.com/Tech/How_2-Stage_Rockets_Work

23. Types… • Composite motors (High powered motors) require indirect staging, where there is a device onboard the rocket that will ignite the upper stage at a chosen time. This is because composite motor ignite from the top of the stack and not the bottom like a black powered motor. • Therefore additional electronics are required on board, this will consist generally consist of a timer and battery, these can fortunately be bought, then if you are feeling brave you could design one yourself. • What starts the timer ? Typically two simple methods are used, pull pin and g-switch. • Pull pin is simpler and cheaper however g-switch is safer and more reliable.

24. Types… • However there are altimeters that can also do this, plus flight computer packages which can fire the rocket only once if meets certain requirement (tilt) for added redundancies and safety. • I recommend someone adventurous or decent at programming could make an Arduino or Raspberry Pie based system which could do this. • http://youtu.be/PLS8sFNJOz4?t=2m40s

25. Types… • Performance/Competition rockets- Rockets that are designed to a specific high performance target. • Most commonly these are optimized for speed or altitude, also more speed does not necessarily mean more altitude so there are different aspects to optimise for both • These rockets normally take careful consideration when being designed and built to perform to their best to achieve a target.

26. What else do you need…. • Launch Pad (this guides you rocket) • Launch controller • Building equipment e.g. sand paper, glues, hobby knives etc • Location, ideally a rocketry club

27. Construction Tips • I cannot go through the whole of how to construct a rocket in such a short time, but apogee rockets, an American rocket supplier has a YouTube channel with many videos on construction. • http://www.youtube.com/user/apogeerockets • http://www.youtube.com/watch?v=5w0LJ7Hw72w

28. Construction Tips Sand till you have no fingers • Drag of a rocket is a big factor which will affect the performance of any rocket. • Drag compromises of two components, skin friction drag and pressure drag. Pressure drag is to do with how air moves around the rocket. • Skin friction drag comes from the boundary layer which is attached to the rockets surface, so a smoother rocket means less skin friction • Also it makes your rocket look better

29. Construction Tips Sand till you have no fingers • Sanding should be done in stages using a coarse grit progressively using finer grits. • A good range of grits to use are 240, 360, 600, 1200. However this will depend on the material you sand.

30. Construction Tips Before applying glue • Model rockets are held together by glue. So insuring the best possible strength of you bonds it crucial. • So one glue might not be best for everything, this will depend on what your are gluing to what. • Before gluing it is recommended to lightly sand the contact areas, this reveals clean untouched material plus give materials a larger surface area. • The grater the surface are for a given area the stronger your bond will be.

31. Construction Tips Built in Fins • Mainly for Mid/High powered rockets fins are built in. • What this means is that the fins actually go through the body tube, this increases the strength of the bond to the body tube.

32. Construction Tips Fin fillets • These are used to increase the strength of your fins • They also provide better aerodynamic behavior at the root edge of your fins. • Normally made from glue or putty which is then sanded or covered by filler then sanded

33. Construction Tips Finish • You are not finished till you have a finish • Finishing your rocket again is not just for making it look nice but if you do it right, your rocket will be smooth the sail through the air. • Before finishing sand your rocket thoroughly by using filler and sanding it down repeatedly. • Once this is done choose a colour scheme and paint, glossy has a decent finish.

34. Kits verses scratch build • A model rocket kit comes with all the parts you need to construct a certain rocket • Example: Magnum Hornet

35. Kits verses scratch build • Scratch built rockets are designed and built from scratch, normally with an aim or some sort of design challenge. This is your starting point. • Producing a design on a rocketry CAD software helps with analyzing stability and simulation, plus visualisation.

36. Kits verses scratch build Scratch build considerations • Is my design stable and safe • Does it meet my specification • Can I get all the materials I need • Construction • Cost • Recovery

37. Kits verses scratch build Pros of Kits • All the parts are provided • Model have been tested and proved to work well • Normally cheaper than buying individual parts • Shorter time scale • CAD files readily available • Easiest and recommended for beginners Pros of scratch build • Design to a certain specification • Designs are only limited by your resources, so they can be as crazy as you want. • Your own creation and unique • Greater understanding of rocketry

38. Materials Common materials. • Cardboard – Body tube • Glassine – Body tube • Quantum tubing - Body tube • Fiber glass - Fins, Body tubes, nosecones • Carbon Fiber, Body tubes, fins • Plywood, Internal structures • Plastic – Nose cones • Metal – Nose cone tip (dangerous), bolts and hooks etc • Other – Light, strong and suitable for their use

39. Sourcing Materials • Sourcing materials can be quite problematic as places to get rocket specific items are few and far apart in the UK. • First you need to know what you want to buy, this can be from your design. It is also a good idea to split what you need into rocket specific items and items readily available: • Rocket specific • Fins (Balsa, Plywood) • Body tube ( Strengthen Cardboard) • Nose cone • Motor mount • Parachute

40. Sourcing Materials • Readily Available items • Fins (Balsa, Plywood) • Body tube ( Strengthen Cardboard) • Shock cords/Nylon/Kevlar • Hooks Once you have that we need to go shopping.

41. Sourcing Materials • There are two main places to go. www.rocketandthings.com www.modelrockets.co.uk • However they do have a limited amount of stock and order items from America etc only a few times a year. • So you may find you need to order from both to get al your parts or neither has them. • In this case send an email to make sure, the try finding alternative sources, there are a few in Europe e.g. http://www.rebelrocketry.com/shop/index.php

42. Videos • http://www.youtube.com/watch?v=_e-sevUOpec • http://www.youtube.com/watch?v=z7fLpKt56Jk • http://www.youtube.com/watch?v=rfnDEryI3Dk • http://www.youtube.com/watch?v=5LL_W2FdEFA&feature=plcp

43. Research, Links and information • Shops http://www.modelrockets.co.uk/shop/index.php http://www.rocketsandthings.com/ http://www.estesrockets.com/ http://www.rebelrocketry.com/shop/index.php • Websites http://www.ukra.org.uk/ http://www.apogeerockets.com/ http://howtobuildmodelrockets.20m.com/index.html

44. References • http://web.mit.edu/16.00/www/aec/rocket.html • http://blog.siriusrocketry.com/2013/07/chris-michielssons-model-rocket.html • http://www.stormthecastle.com/model-rockets/the-estes-hi-flyer-rocket-part-2.htm • http://blog.siriusrocketry.com/2013/07/chris-michielssons-model-rocket.html