Dual Deploy Recovery Why do dual deploy? What you need Mandatory - - PowerPoint PPT Presentation

Dual Deploy Recovery

Why do dual deploy?

What you need

Mandatory

• Altimeter
• Wiring
• Battery and holder
• Switch
• Black powder/pressurant
• Recovery devices

Optional/Configuration-dependent

• Redundant systems
• Charge wells
• Shear pins
• Parachute management devices
• Wire nuts
• Miscellaneous hardware

Popular Altimeters

• Cost-effective

– ADEPT products – MissileWorks products (RRC line, etc) – PerfectFlite products (StratoLogger, etc) – Recording-only (no deployment capabilities)

• Extra Features

– Raven 3 – Altus Metrum products

• DIY

– Eggtimer, Eggtimer TRS

ADEPT22

• Cost: $45
• Dimensions: 2.8”x0.9”x0.6”
• Max Altitude: 25,000 ft
• Weight: 12 g
• Programming: 7 presets
• Outputs: 2
• Data: Altitude buzzer tone
• Memory: 1 flight
• Sensors: Barometric

DDC22

• Cost: $35
• Dimensions: 2.8”x0.9”x0.6”
• Max Altitude: 100,000 ft
• Weight: 12 g
• Programming: 7 presets
• Outputs: 2
• Data: None
• Memory: 1 flight
• Sensors: Barometric

MissileWorks RRC3

• Cost: $70
• Dimensions: 3.9”x0.93”x0.5”
• Max Altitude: 40,000 ft
• Weight: 17 g
• Programming: USB
• Outputs: 3
• Data: Buzzer tone, USB
• Memory: 15 flights
• Sensors: Barometric

PerfectFlite StratoLoggerCF

• Cost: $55
• Dimensions: 2”x0.84”x0.5”
• Max Altitude: 100,000 ft
• Weight: 11 g
• Programming: FTDI
• Outputs: 2
• Data: Buzzer tone, FTDI
• Memory: 16 flights
• Sensors: Barometric

Eggtimer

• Cost: $35
• Dimensions: 3.9”x1”
• Max Altitude: 30,000 ft
• Weight: 20 g
• Programming: USB or LCD
• Outputs: 2
• Data: Buzzer tone, LCD, USB
• Memory: 32 flights
• Sensors: Barometric

Featherweight Raven 3

• Cost: $155
• Dimensions: 1.8”x0.8”x0.55”
• Max Altitude: 100,000 ft
• Weight: 7 g
• Programming: USB
• Outputs: 4
• Data: Buzzer tone, USB
• Memory: 5 flights
• Sensors: Barometric, accel

Altus Metrum TeleMetrum

• Cost: $300*
• Dimensions: 2.75”x1”x0.56”
• Max Altitude: 100,000 ft
• Weight: 18 g
• Programming: USB
• Outputs: 2
• Data: Buzzer tone, USB
• Memory: 8 flights
• Sensors: Barometric, accel

Altus Metrum TeleMega

• Cost: $400*
• Dimensions: 3.25”x1.25”x0.56”
• Max Altitude: 100,000 ft
• Weight: 25 g
• Programming: USB
• Outputs: 6
• Data: Buzzer tone, USB
• Memory: 4 flights
• Sensors: Barometric, accel

Mach Delay

• Sharp rise in pressure across a shock wave falsely

simulates rocket descent (pressure increasing as altitude drops)

• Modern altimeters have built in filters to prevent

accidental ejection at supersonic/locally supersonic speeds

• Old altimeters would have timers that could prevent

ejection in these scenarios

Switches

• Any electronics must be armed at the pad with the rocket

in a vertical position on the rail (HPR Safety Code)

– Precaution in case charges go off prematurely

• Switches prevent disassembly and reassembly at pad
• Avionics must be turned on and verified as armed before

installing an igniter into the motor

• At least one switch per system required
• Should be rated for current (~2 A) and voltage (~9 VDC)

Key Switches

• Vary in prices, but expect to

spend $5 or more each

• Externally accessed, mounted

by the wall of the airframe

• Some have traditional keys;
• thers have flathead “key”
• Note voltage and current

ratings

• May require soldering

Screw Switches

• Relatively cheap
• Small form factor, weight
• Easy to mount internally
• May be difficult to access to

turn avionics on/off

– Multiple revolutions may be required to actuate

• Any screwdriver acts as a key
• Rated for voltages, currents

Magnetic Switches

• Tend to be moderately

expensive

• Turn on and off by waving a

magnet over switch

• Does not require any

protruding switch

– Minimizes drag of vehicle – Easy to use since no key needs to be inserted

• Soldering may be required

Twisted Wires

• Simplest, cheapest method of arming electronics
• Two wires protrude from the airframe, but are not shorted

until ready to arm electronics

• Exposed ends of wires twisted together and taped to

complete the circuit

• Tape to external airframe

– Prevents wires from coming undone – Allows easy access to disarm electronics safely

Pressurization Systems

• Just like motor ejection charge in traditional rocketry

deployment

• Black powder (or black powder substitute such as

Pyrodex) is most common

• Cold gases can be used, and there are commercially

available solutions

• Mechanical systems theoretically possible, though

generally infeasible for HPR

How much powder?

m"# (grams) = C , D. , L

• C: coefficient based on

pressure

– 0.002 = 5 psi – 0.004 = 10 psi – 0.006 = 15 psi – 0.0072 = 18 psi – 0.008 = 20 psi

• D: airframe diameter (in)
• L: length of parachute bay (in)

Black Powder – Wrapped Charges

• Simple implementation, but cannot be directed
• Create 5”x5” sheet of tape (non-static) sticky side up
• Place igniter head in center of the tape sheet with leads

extending out

• Measure correct amount of powder and pour into center
• f the tape sheet (onto igniter head)

Black Powder – Charge Wells

• Containment system for black

powder charges and igniters

• Can use PVC caps or

commercially available charge wells

– Commercial solutions are sized to fit specific powder mass

• Relatively cheap
• Easy to mount on a bulkhead
• Directs ejection charge

CO2 Systems

• No hot gases, residues

– Good for altimeters and electronics – Does not burn parachutes and cords

• Significantly more expensive

than black powder systems

• CO2 bottle pre-measured
• Bulky, heavy, and requires

small amount of black powder

Parachute Sizing

Drogue

• Size parachute for descent rate of

50-100 ft/s

• Too slow of a descent eliminates

the benefit of dual deploy

• Too fast risks rocket damage

(zippering, etc) at main parachute deployment

• Typically drogue chutes are 18”

(lightweight rockets) to 36” (heavy) Main Parachute

• Size as you normally would for
• ptimal landing speed
• Generally 2-4 times larger than

drogue parachute Diameter = 2 v5678 2W ρπC<

Parachute Management

• Easiest way to manage parachutes is to keep in separate

compartments (classical approach)

• Sometimes advantageous or necessary to keep

parachutes in same compartment, but still use dual deploy

• Devices exist to prevent main parachute inflation until

prescribed time/altitude

Deployment Bags

• Protects the parachute from

the ejection charge

• Prevents large “jerk” when the

parachute inflates

• Allows the parachute to move

away from the rocket before it

• pens
• Bag must be appropriately

sized for parachute

• Utilizes a pilot parachute

Tender Descender

• Allows both parachutes to be

packed in same compartment, but allows for delay in deployment of main parachute

• Ties down main until ejection

charge releases the restraint

• Moderately expensive ($59+)
• Comes in three sizes based
• n weight/forces

Cable Cutters

• Allows both parachutes to be

packed in same compartment, but allows for delay in deployment of main parachute

• Ties down main until ejection

charge releases the restraint

• Moderately expensive ($30)
• Very small body
• Relies on expendable cables

Implementation of Dual Deploy

• Set drogue parachute to be deployed at apogee

– Detected barometrically, with accelerometer, or with timer

• Set main parachute to be deployed at specific altitude or

time

– Detected barometrically or with timer – Popular settings are between 500 ft and 1000 ft

• Parachutes that take longer to inflate may be set to

deploy at higher altitudes for safety/reliability

• Deploy at lower altitudes on small fields

Avionics Bays

• Popular implementation is to

convert a coupler into a sealed avionics bay

– Add 1”+ of airframe as a key band and shoulder

• Should be easily accessible

from both sides

– Do not glue into airframe!

• May want to use threaded

rods as structural stiffener

Avionics Bays

Bulkheads

• At least one bulkhead should be

removable so electronics can be removed

• Mount charge wells and U-bolts/eye

bolts to each bulkhead

• To accommodate igniters, install

terminal blocks or small holes to thread igniters through

– No large holes so gases don’t affect electronics

Interior components

• All altimeters, batteries,

miscellaneous electronics mounted

• n sled

– May use threaded rods or puzzle locks to hold sled in position throughout flight

• For externally mounted switches,

use wire nuts to connect switches to electronics (for easier installation and removal)

• Use screws, tape, and zip ties to

hold components in place

Venting

• Barometric sensors must be

exposed to outside environment

• No obstacles above vent
• Can use almost any number

– Never use just two – One possible, not recommended

• One 1/4 inch diameter vent hole

(or equivalent area) per 100 in3

• f volume in the altimeter bay
• Between 1/32” and 1/2”
• At least four body diameters

below nosecone junction

• Evenly spaced around key band

Basic Wiring Guide

How to Pack Your Parachutes

Drogue chute near CG Main chute near nosecone

Considerations for Shock Cord

• No such thing as “too much shock cord”
• Longer segments recommended for drogue

– Large masses on both ends of shock cord – Despite parachute sizes, drogue deployment forces typically exceed main deployment forces

• Like for single deploy, 20+ ft of shock cord recommended

– More for heavier rockets or larger ejection charges

Shear Pins

• Keep rocket together when it

should be in one piece, but allow it to separate on ejection

• Typically #2 nylon screws

– Break very easily under shearing force between airframe components

• Use plastic, fiberglass, etc

reinforcement on cardboard parts to prevent tearing

• Number required depends on

amount of black powder used

Rivets

• Use removable rivets to hold

together components that should not separate in flight

• Require significantly more

shearing force to break than shear pins

• Use depending on how you

configure your parachute ejection