water rockets
DESCRIPTION
Water rockets are propelled by water. In this presentation we highlight the details and procedures aimed at successful fabrication of a double stage water rocket.TRANSCRIPT
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 ,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
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
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
FBD of water rocket
The water rocket is subjected to following forces in air:• Gravitational• Thrust• Drag
Equation of motion:
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
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