Twin stage water rocket. Detailed analysis and study of mechanisms involved. Indian Institute of Space Science and Technology

1. DESIGN OF TWO-STAGE WATER ROCKET
Team members
Ankit Sachan
Himanshu Kumar
Kartikey Sharma
Mayank Kumar
Shubham Maurya

2. OVERVIEW
 Study of physics and basic aerodynamics
 Proposing ideas on
 Launcher
 Staging mechanism
 Designing launcher
 Designing staging mechanism
 Drawings
 CATIA model
 Purchase of materials
 Fabrication
 Troubleshooting
 Launching

3. PROJECT TIMELINE
 22 June - Mayank comes
 24 June - Catia design of component starts
 26 June - Mayank meets Pankaj Priyadarshi Sir-
discussion on staging and Parachute deployment
 29 June - Shubham , Ankit and Himanshu comes
 30 June - literature discussion among groups
 1 July - Kartikey arrives
 3 July - aero club meeting

4.  4 July - first presentation on various aspect staging
and launcher
 6 July - second meeting - change of staging
mechanism due to non availability of materials.
 6 – 9 July - theoretical aspects of trajectory and
analysis
 9 July - the launch begins of first stage water rocket
 10 July - meeting with Pankaj, Suraj and Vinil sir
 12 July - Clarification of material purchase process
 15 July - fabrication starts

5. INTRODUCTION
 A water rocket is a bottle with
fuel as pressurized air with
water

6. DOUBLE STAGE WATER ROCKET
 Two water rockets joined by
a staging mechanism
 1st stage – Booster
 2nd stage – Sustainer
 Stage separation when 1st
stage finishes and pressure
becomes same as
atmospheric pressure

7. WHY STAGING?
 When we work on the complex mechanism of
staging obvious question arises, why do we need
staging?
 We do it owing to its numerous advantages over a
big single stage one
 Reduction of dead weight by jettisoning used stages
 Drag reduction by the initial phases

8. DYNAMICS OF WATER ROCKET
FBD of water rocket
The water rocket is subjected to following
forces in air:
•Gravitational
•Thrust
•Drag
Equation of motion:

9. AERODYNAMICS OF WATER ROCKET

10. PARAMETERS AFFECTING FLIGHT
 Nozzle Size
 The nozzle size in water rockets is measured by the
narrowest internal diameter .
 The internal diameter is important because it directly
relates to the mass flow rate out of the nozzle.
 Larger the nozzle the higher the thrust for a given
pressure. but reduces the time of thrust.
 Water is a incompressive fluid so question of
Converging-Diverging nozzle rules out

11.  Drag and stability
 Smoothening of surfaces and nose cone reduces drag
 Parabolic nosecone are most efficient in subsonic range
 Fins increase stability
 Amount of water
 The optimized amount of water is around 21-35 % of
empty volume of bottle depending on various factors
like:
 Weight
 Pressure
 Nozzle diameter

12. STAGING MECHANISM
 We explored different types of mechanism to
finalize it.
 Efficient stager is the one
 Separates the stages after full burn out of booster
 Lightweight
 Separates with booster
 Well stable at ground and first stage

13. Mechanism 1

14.  At the ground
 Pressure in both the chambers is same so there in no gauge
pressure trying to separate them.
 While air borne
 There will be gauge pressure developed but that will be
compensated the thrust provided by boasters
 Loading of the sustainer compresses the spring and
pushes the locking tabs inward and locks up the
sustainer
STABILITY & WORKING

15. STAGING
 After the burning of booster
 The system is in free fall
 no compressive forces on spring, it will pushing the component
assembly out so the locking tabs will be free to move outward.
 This will release sustainer and allows the pressure to further
separate the stages.

16. SPECIAL
 This mechanism uses normal reaction to balance
the force.
 In natural state pressure is trying separate stages.
 Totally separates with booster

17. Mechanism 2

18. STABILITY AND WORKING
 At the ground
 Spring is compressed under the weight of the sustainer
stage
 Pressure in both the chambers is same so there in no gauge
pressure trying to separate them.
 While air borne
 There will be gauge pressure but due intelligence of design
there are no vertical separating forces.
 The thrust compresses the spring further. In flight the
non return valve retains the pressure of the booster
stage.

19. STAGING
 Once the booster burns out the system is in free fall
condition
 Spring will not experience further compressive forces
 It will push the piston out. Once the piston reaches the
nozzle exit holes, the pressure will exert a direct force
on piston leading to final active separation of stages

20. MORE OF IT
 Resistive forces by O-rings should be less than the
weight of sustainer assembly as spring is simply
storing the PE and further used to separate
 Except of the spring no member is under strain
 One of the chamber is at atmospheric pressure
 there are no vertical separating forces when piston
and nozzle have matching condition.
 Only a part of mechanism separates off

21. SELECTION CRITERIA
 We chosen mechanism two considering following
 One crucial component GARDENA COLLER of
mechanism 1 was not available and fabrication was not
feasible owing to its structural complexity
 Mechanism 2 was relatively simple
 Easy to fabricate
 Low cost

22. FABRICATION CHALLENGES
 The first problem came in drilling blind holes in
nozzle and piston
 Drill bit was not available due to high aspect ratio
 Thermal expansion in nylon during drilling we
solved it with increased coolant rate
 Clearance for piston-nozzle movement
 To make groves on the piston for the O-rings which
prevents pressure leakage

23.  To drill a hole of 2 mm diameter for one-way valve.
 Joining two PET bottles for the two headed booster
 Using layered sealing
 Overcome the impact of collision on the nose cone
 We reinforced the nose cone to absorb the impulse
 Best aerodynamic shape is a paraboloid but due to
design constraints we used a hemi-spherical nose
cone which second comes.

24. CATIA™ MODELS OF STAGING MECHANISM
Bottom cross-section of piston
3D view of Piston
PISTON

25. NOZZLE
3D view of nozzle

26. REALIZED STAGING MECHANISM

27. LAUNCHER MECHANISMS
 Clark Cable-tie mechanism
 The zip ties clamp
the neck by moving
the collar up.
 Collars need to be brought
down manually to release
the rocket

28.  Pin release mechanism
Working
 The pin is metal plate that
holds the neck of bottle
while filling air
 Air flows from the hose
pipe through nozzle to
bottle
 After pressurization, pin
is released by pulling the
wires attached to it
Advantages
 We can release the pin at
a distance ensuring
safety against bursting

29. FEW TEST FLIGHTS
-AT ANGLE 50° WITH HORIZONTAL

30. VERTICAL LAUNCH
T=0.033 s T=0.067 s
T=0.1 s

31. ANALYSIS OF FLIGHT USING TRACKER™
#1

32. HEIGHT (m) vs. TIME (s) GRAPH
#1

33. #2.1

34. #2.2

35. #2.3

36. #2.4

37. #2.5

38. Position (m) vs. Time(s) graph
x vs. t
y vs. t

39. Velocity (m/s) vs. Time (s) graph
V vs. t
Vx vs. t
Vy vs. t

40. RECOVERY SYSTEMS
 Recovery is a mechanism to prevent the huge impact on
water rocket upon hitting the ground
 Two classification of recovery system
 Passive
 No moving parts
 Part of the rocket design
 E.g. nose cone cushioning
 Active
 Moving parts
 Activate at some point of time
 E.g. Glider, Parachute deployment, retro rockets, etc..

41. Pre-stowage
Arming
Start
Monitoring
Activation
Deployment
Post-flight maintenance
 Steps involved in a recovery system

42. DETAILS OF RECOVERY SYSTEM

43. DIFFERENT TYPES OF RECOVERY TECHNIQUES
 Parachute - The rocket uses a
parachute to increase drag to slow its
descent
 Streamer - The rocket uses a ribbon
instead of a parachute to create drag
 Glide - The rocket is equipped with
wings that generate lift and the
rocket glides to a soft landing
 Balloon - The rocket inflates a
balloon to either increase drag or
when combined with a lighter-than-
air gas, produce lift

44. CURRENT STATUS
 Design has been realized
 Troubleshooting is going on to fix:
 Leakage through contact surfaces
 Shearing of O-ring
 Frictional forces between piston
and nozzle
 Only nosecone cushioning method
has been tested so far and has
successfully mitigated the effect of
head on collision with ground.
 Theoretical aspects are yet to be
explored fully due to limitation of
our current knowledge on
 Fluid mechanics
 Aerodynamics
 Numerical analysis

45. REFERENCES
 Wikipedia
 www.aircommandrockets.com
 http://www.grc.nasa.gov/WWW/K-12/
 www.cabrillo.edu/~dbrown/tracker/
 http://antigravityresearch.com/
 http://www.uswaterrockets.com/

46. ACKNOWLEDGEMENT
 We would like to acknowledge the help provided by our
institute Indian Institute of Space Science and
Technology (IIST) to fulfill the requirements of the
project, and AeroClub to initiate Summer Projects in the
institute.
 We would like to express our special thanks of
gratitude to our project mentor Mr. Pankaj Priyadarshi.
We would also like to convey thanks to Dr. Sooraj sir
and Dr. Virghese who benefitted us with their experience
in the field of fabrication and troubleshooting.
 Last but not the least, we are very grateful to
Engineering workshop instructors and all the people
related to the project without whom we could not have
progressed this far.