TWIN STAGE WATER
ROCKET
PROJECT TIMELINE
22 June - Mayank comes
24 June - Catia design of component starts
26 June - Mayank meets Pankaj Priyadarshi Sirdiscussion on staging and Parachute deployment
29 June - Shubham ,Sachan and Himanshu comes
30 June - literature discussion among groups
1 July - Kartikey arrives
3 July - aero club meeting
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
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
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
Mechanism 1
Stablility and working
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
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.
SPECIAL
This mechanism uses normal reaction to balance
the force.
In natural state pressure is trying separate stages.
Totally separates with booster
Mechanism 2
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.
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
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
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 fabrication
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
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
DYNAMICS OF WATER ROCKET
The water rocket is subjected to following
forces in air:
Gravitational
Thrust
Drag
Equation of motion:
FBD of water rocket
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
Drag co-efficient
Smoothness of the surface determines the amount of
drag forces due to air
Smoothening of leading and trailing edges of fin
Parabolic nosecone are most efficient in subsonic range
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
LAUNCHER
FEW TEST FLIGHT
CURRENT STATUS
Model has been realized
Troubleshooting is going on to fix:
Leakage through contact surfaces
Shearing of O-ring
Frictional forces between piston and nozzle
Theoretical aspects are yet to be explore totally,
due to limitation of our current knowledge on
Fluid mechanics
Aerodynamics
Numerical analysis
ACKNOWLEDGEMENTS
www.aircommandrockets.com
Wikipedia
