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It
•
•
•
has three important parts
Descent control system
Material Selection
Egg protection
CanSat 2013 PDR: Team 1276 (Garuda)
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DESCENT CONTROL SYSTEM
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DESCENT CONTROL
• Most important part of CanSat
• Need: To bring the descent rate to a value such that
components are not affected by final impact with
ground
• Devices : Drag or Lift Generating
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Descent Rate Calculations
Formula used for calculating the terminal velocity
2W
Vt 
Cd A
Where
Vt= Terminal Velocity
W= Payload
Cd= Coefficient of Drag (1.5 for round and hemisphere)
ρ =Density of Air (It varies from 600m to ground level)
A= Equivalent area of Parachute or cluster of them
((π*d2)/4)
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DESCENT RATE CONTROL :
Our Design
• Objective: To reach the descent rate of 20 +/- 1m/s
• Procedure:
 Determination of basic dimensions and attributes of
parachute through preliminary calculations
 Determination of material’s coefficient of drag.It can be
determined through Ansys Fluent analysis.
 Experimentation to determine actual descent rate
• Problems encountered:
 It is not possible to find heights to test the parachute
 More the height, more is the drift; hard to relocate
parachute
 Difficult to find out terminal velocity
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Descent Control Strategy Trade &
Selection : Our Method
 DRAG MECHANISM SELECTION
Drag Mechanism
Benefits
Problems
Decision
Parachute(without
spill hole)
Large coefficient of drag
Drifting, Oscillations
Not to be used
Parachute(with spill hole)
Reduced drifting and
oscillations, Lesser
material and weight
Descent rate has
increased
Selected
Streamers
Faster recovery,
Heavier, Occupies larger
Reduced Drifting, Lesser
volume
drag
Not to be used
Paraglide
Descent control methods
include drag and lift
Drift need to be there to
enable it to control
descent via lift
Not to be used
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
Descent Control Strategy Trade &
Selection : Our Method
MATERIAL SELECTION
Material
Ripstop nylon
Mylar
Flex
Retired Hot air balloon
Benefits
Problems
Decision
Slightly expensive
To be used
Not easily available
Can’t be used
Alternative to Mylar
Heavy and more porous
Not to be used
Alternative to ripstop
nylon as it will be less
expensive
Fewer colour options,
Need to be washed
several times to get the
smell of the gas out,
need to be replaced after
certain time of usage
Can’t be used
Lower porosity, Dyed in
many colours, Easily
available
Thin, Light,
Cd=0.14(approx.)
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Descent Control Strategy Trade &
Selection : Our Method
 PARACHUTE SHAPE SELECTION
Shape
Payload
Dimension
Descent rate
Decision
Round
710g
10cm
42.83m/s
Selected
Square
710g
10cm
53.53m/s
Not to be
selected
Hexagon
710g
10cm
47.06m/s
Can be
considered
FINAL DECISION: Round shape is selected be because it provides minimum descent rate
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Container Descent Control Strategy
Trade & Selection
Color Selection
•
•
Parachutes are ordered from FruityChutes.com which provide varied color
parachutes
Colored parachute is preferred because of its ease in detection
Shock Force Survival & DCS Connection
•
Parachute is connected to envelope via strings that can take up shock of sufficient
magnitude
Pre Flight review testability
•
•
•
Plumb line with very low weight as compared to payload
Length of string to be very long
Calculate the descent rate by simple formula-
Velocity =
Plumb Line Length
Time
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OTHER DRAG DEVICES
• UMBRELLA DESIGN
– Compressed Air Transport (Lift Providing Mechanism)
 Air is highly compressed(about 20atm) and flows through nozzles to provide
upper thrust
 Air need to be compressed at very high pressure
 Container material not easily available and will lead to increase in weight
 Experiments showed that air compressed at 6 atm in 4L container with 3 nozzles
provided thrust for just 5-6 seconds
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Material Selection
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Material selection for the payload
Material Selection
Requirement:
• It should be light in weight
• Easily available in nearby market
• Easy to manufacture
• Material Properties
How to select the material
• Using data base software like CES
• Test its properties on FEM software
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Problem Statement
Propose a descent control system for a payload of 800gms with these
requirements:
• It should have an initial size of 250X130mm containing all the
components for descent control.
• During flight, it can expand to any dimension.
• At the ground, it should have a velocity of around 8-10m/s to ensure the
safe landing of the payload.
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