Mars Rover CDR

Rensselaer Rocket Society

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Presentation Outline

• Introduction, William He
• Systems Overview, William He
• Rocket Design, Alex Rishty
• Rocket Recovery System, Keith Beadle
• Motor Selection, Alex Rishty
• Rover Design, Kaylee La Spisa
• Rover Electronics, Alex Wu
• Testing, Ethan Wilens

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Team Organization

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Acronyms

• ARD = Arduino
• PLA = Polylactic Acid
• CONOPS = Concept of Operations
• CAD = Computer Aided Design
• TTA = time to appogee
• NAR = National Association of Rocketry
• HPR = High Power Rocketry
• CRMRC = Champlain Region Model Rocket Club
• UTS = ultimate tensile strength
• ABS = acrylonitrile butadiene styrene

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System Overview

William He

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Mission Summary

Overview of System Requirements:

1. Rocket and rover must launch to at least 1000 feet and deploy Mars Rover
2. Rover must be able to overcome cut corn stalks which can be as tall as one foot
3. Rover must be fully contained in the rocket before being deployed
4. Rover must return to the ground safely
5. Rover must be designed to withstand the forces associated with rocket ejection and landing
6. Rover must take a picture and transmit to a ground station
7. Rover must detach parachutes after landing
8. Rover must travel 3 feet
9. Rover must collect between 5 and 25 grams of dirt
10. Travel must be done within 10 minutes (time starts at time of landing)
11. Dirt collection must be done within 5 minutes

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System Requirement Summary

Rocket

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System Requirement Summary

Rover

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System Requirement Summary

Controller

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Changes since PDR

• Fastener Locations Changed
• Rover Chassis and Drive Base Extended
• Screws 3D printed

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System Level Design

• Rocket is 5.5” cardboard tubing with a I600
• Rover is driven with screws to move across dirt

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System Concept of Operations

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Rocket Design

Alex Rishty

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Rocket Changes since PDR

No changes were made

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Design of Rocket

• Describe overall rocket design
• Length: 88 in
• Airframe Diameter: 5.540 in
• Mass:
• With I600: 4254 g
• With J500: 4291 g

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• Center of Gravity
• With I600: 48.18 in. from nose tip
• With J500: 48.47 in. from nose tip

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• Center of Pressure:
• 63.95 in. from nose tip
• Center of pressure is the same for both motors
• 3 trapezoidal fins
• 30 cm root cord
• 16cm tip cord
• 13 cm height

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Nose Cone

Nose Cone Chute

Rover

Rover and Main Chutes

Electronics Bay

Piston

Drogue Chute

Motor

Fins

Rocket Airframe

• Lengths of various sections of airframe
• Booster Airframe: 24 in.
• Switch Band: 1 in.
• Payload Bay: 42 in.
• Airframe Diameter: 5.54 in. outer, 5.38 in. inner
• Airframe Materials
• LOC Precision Tubing, cardboard, 2-56 nylon shear pins
• Nose Cone
• Length: 21 in.
• Diameter: 5.5 in.
• Shape: Tangent ogive
• Material: Polypropylene
• Motor Mount
• 38mm diameter
• 16 in length
• Steel Z-clips will be used to retain the motor

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Rocket Materials

• List of materials used:
• Airframe material - Brown Craft Paper
• Motor mount material - Phenolic board
• Fin material - Birch Plywood
• Nose cone material - Polypropylene
• Type of adhesives used - Wood Glue and JB Weld
• Rail button source and material - nylon buttons for 1515 rail. Each secured with an 8-32 machine screw through the airframe.

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Rocket Recovery System

Keith Beadle

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Rocket Recovery System

• Parachute selection
• Rocket: 60” main chute, 24” Nose Cone, with a 24” drogue chute
• Rover: 1x 44” chute
• Parachute selection was determined by hand and then adapted for parachute sizes and budgetary restrictions.
• Drouge Protected by 18in square Nomex Blanket
• Main Parachute and Rover Parachute protected by piston

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• Drift distance assumes 20 mph winds

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Rocket Recovery System

• Harness
• Shock cords
• 9/16” tubular nylon - 1500 lb test - 25’
• Linkages
• ¼” quick links - 1400 lb test
• Each main parachute attachment
• End of harnesses
• Attachment points, eyebolts, fender washers, etc. and their mounting methods
• ¼”-20 forged eye bolts - 500 lb test
• Attached to each end of electronics bay
• Nose cone parachute is directly attached to slots in nose cone
• Main parachute will quick link to the recovery harness
• Feeds through the pison bulkhead and tied to the forward eyebolt of the electronics bay
• Drogue will quick link to the recovery harness
• Tied to the back eyebolt of the electronics bay

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Rocket Recovery System

Deployment Method

• 1 Stratologger CF Altimeter will be used as primary (scoring)
• 1 RRC2+ Altimeter will be used as backup
• Main parachute release mechanism - piston
• Motor ejection
• Primary motor
• I600 -14 second delay
• Secondary motor
• J500 - 14 second delay

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Altimeter Bay Layout

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Rocket Recovery Electronics

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• Volume
• Main - 454 in³
• Drouge - 148 in³
• Ejection Charge - Black Powder - fired with e-matches
• Main Primary - 3.5 g
• Main Backup - 4 g
• Drogue Primary - 1.25 g
• Drogue Backup - 1.5 g
• Motor - 1.5 g
• Each section will be secured with sheer pins
• Shear Pins: 3 2-56 nylon screws
• Three at each section
• Each less than 50 lbs shear strength
• Sep. strength at 15 PSI is greater than 350 lbs

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Ejection Charge Safety and Arming

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Ejection Charge Installation - After all other prep phases but prior to check-in

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1. Measure an appropriate mass of 4f BP into a charge well (Each well is labeled)
2. Install 2 redundant E-Matches into charge well
3. Plug E-Matches into appropriate labeled terminal block
4. Seal the charge well with tape
5. Repeat for each charge

Arming on the pad - Prior to inserting motor igniter

• Turn switch to power on backup altimeter
• Verify that backup altimeter is powered on and functioning correctly
• Turn switch to power on primary altimeter
• Verify that primary altimeter is powered on and functioning correctly

General Safety Considerations

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• BP will be stored in a climate-controlled environment away from any potential sources of ignition
• All ejection charge installation shall only be performed by properly certified personnel over the age of 18
• After ejection charges have been installed, no personnel will pass the rocket in such a location as to be in the path of any section of the rocket should the charges be inadvertently activated
• Altimeters will only be armed when the rocket is vertical on the launch pad

Disarming After a Scrub

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• Turn off all altimeters, verify all altimeters are powered off
• Remove electronics bay and pour out each ejection charge

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Motor Selection

Alex Rishty

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Primary Motor Selection

• Primary Motor: I600R
• Manufacturer: Aerotech Consumer Aerospace
• Certifying Organization: Tripoli Rocket Association
• Casing: 38/720
• Avg Thrust to Weight Ratio: 12.7:1
• Expected Apogee: 1771 ft
• Expected Max Velocity: 492 ft/s
• Expected Max Acceleration: 514 ft/s²
• Expected Minimum stability: 2.31 Caliper
• Time to Apogee: 10.24s

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Primary Motor Simulations

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Primary Motor Stability Graphs

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Backup Motor Selection

• Primary Motor: J500G
• Manufacturer: Aerotech Consumer Aerospace
• Certifying Organization: Tripoli Rocket Association
• Casing: 38/720
• Avg Thrust to Weight Ratio: 10.6:1
• Expected Apogee: 2054 ft
• Expected Max Velocity: 428 ft/s
• Expected Max Acceleration: 497 ft/s²
• Expected Minimum stability: 2.18 Caliper
• Time to Apogee: 10.96s

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Backup Motor Simulations

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Backup Motor Stability Graphs

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Rover Design

Kaylee La Spisa

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Rover Changes Since PDR

• Fastener Location Changes
• Rover Chassis & Drive Base was extended 2 in (Fig.#1)
• 3D printing method for screws (Fig.#2)

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Fig.#1

Fig.#2

2” Addition

Rover Design Overview

Major Components:

1. Chassis

2. Drive Base

3. Collection Mechanism

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Chassis/Main Frame

Drive Base

Collection Mechanism

Rover Design Overview Cont.

Rover Dimensions:

Folded - 11.24” long, 4.57” wide, 5.05” deep

Expanded - 11.24” long, 7.12” wide, 4.01” deep

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Rocket Inner Diameter

State #1 - Folded:

Pre-Apex Ejection

State #2 - Expanded: Post-Apex Ejection and Nichrome Wire Burnout

Rover Mechanics

• Mechanical design description of rover
• A main frame constructed of composite aluminum was utilized as the electronics bay and the supporting structure for the drive base (Drive screws & Drive Base Arms)
• Drive Base Arms support the rotating augers through two ⅜’’ bearings as well as the driving servos. The arms themselves are supported by the Chassis by two brass reverse-loaded spring hinges, of which allow the arms to expand outwards.

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Reverse-Loaded Spring Hinges

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• Electronics will be secured to the base plate of the chassis/main frame via small plastic screws & epoxy for specific components.

Rover Locomotion

• Screw Drive
• 2x Continuous Motors (RB-Nex-40) counter-rotating auger-like columns with helical flanges
• Flanges apply continuous leverage from vehicle to ground eliciting forward locomotion

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Rover Materials

Types of Materials Utilized

• Durabond Aluminum Composite Paneling (Aluminum faces with a polyethylene core)
• Polylactic Acid (PLA)
• Nylon brackets

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Soil Sampling Mechanism Design

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• Components:
• 3D-Printed PLA Scoop
• 2x MG996R TowerPro servos
• Composite Durabond frame
• 3D-Printed PLA Servo Bracket
• Mechanism
• Scoop arm with two degrees of freedom, actuated
• Mechanism folds into cavity on underside of rover

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Servos

Servo Bracket

Scoop

Frame

Soil Sampling Mechanism Cont.

During Launch:

During launch, mechanism is pressed flat against the

underside of the rover frame in order to allow screw arms to

fold inward. This allows the rover to be stowed for launch.

During Operation:

During operation, the mechanism remains pressed against the bottom of the rover until the rover receives the signal to collect a dirt sample.

Soil Retainment

The inside of the scoop picture (in blue) will have flanges adhered with velcro,upon assumed successful soil collection, the scoop will press into the underside of the rover to opposing velcro- at this point the scoop/soil will be contained.

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Rover Descent Control

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• Nichrome wire releases Rover drive base from its

folded arrangement

• A 44” chute will be used to slow the Rover
• Projected descent rate of 12.1 ft/s
• Drift distance assuming 20mph winds: 1230ft
• Four eyebolts connect robot to parachute via nichrome wire
• Shorted nichrome wires cuts parachute once the rover has landed

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Overview: Once the rover has ejected from the rocket body,

nichrome wire holding the articulating drive flanges in position

will burn out some seconds after descent has begun to avoid

parachute entanglement. Once the rover altimier reads a

altitude change of 0, another set of nichrome wire will burn out

releasing the parachute apparatus. From here, the rover will

begin ground operations.

Rover Mass

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Total Estimated Rover Mass:

1318.19 grams

or approximately 1.32 kg

Total Allowed Rover Mass:

2000 grams

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Allowed-Estimated=

Margin of -681.81grams

Rover Electronics

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Rover Electronics (cont.)

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Rover Radio

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FInal Radio Selection: HC-06 Bluetooth Module

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FInal Antenna Selection: N/A

Antenna is unessential to operation of rover:

• Controller will be operated significantly less than 5m away from rover at all times
• HC-06 module includes a built-in antenna

Rover Power

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FInal Battery Selection: 7.2v NiMh Battery Pack with 9v Alkaline Battery

• Implementation
• 7.2v NiMh negative wired into ground bus on servo powerhub, which is grounded to ARD Nano (see slide 43 or 47)
• 7.2v NiMh positive wired into normally closed terminal in Featherwing relay with relay common terminal wired to positive bus on servo powerhub
• 9v battery feeds into a step down transformer and is stepped down to 5v, which powers Raspberry Pi Zero and ARD Nano in series.
• Capacities
• 7.2v NiMh: 2200 mAh
• 9v Alkaline: 500 mAh
• Mounting
• 7.2v NiMh: fully encased in a plastic cage screwed into the rover frame
• 9v Alkaline: fully encased in plastic container and secured with glue within the rover frame
• Protection circuits:
• Capacitors across positive and negative leads on servo powerhub to prevent voltage fluctuations as a result of heavy loads. Ensures Raspberry Pi and ARD run smoothly.

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Rover Power Distribution

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Power Distribution Methods

• Stepdown Transformer: The stepdown transformer converts a 9v 500mAh battery into a 5v, 900mAh power source, fit for use with the Raspberry Pi which in turn powers the Arduino in series.
• Featherwing Relay: Controls the 7.2v NiMh’s connection with the servo powerhub to reduce risk of shorts during maintenance, start up, and shut down.
• Servo Powerhub: Splits 7.2v NiMh power supply in parallel among four servos, using bridging capacitors to prevent voltage fluctuations.

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Rover Power Budget

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Battery: 9v Alkaline Battery

Capacity: 6.3 Wh

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Estimated life of 9 v Alkaline Battery: 3.87 hours

Rover Power Budget cont.

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Battery: 7.2v NiMh

Capacity: 15.84 Wh

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Estimated life of 7.2 v NiMh: 1.38 hours

*Assuming servos are at maximum load

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**Assuming only two servos will be active at any given time, so total current draw is estimated to be 1600 mAh (extra 200 mAh accounting for idle state).

Rover Camera

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FInal Camera Selection: Raspberry Pi IR-CUT Camera

• Description
• 1080p camera designed for interfacing with Raspberry Pi platforms
• 5MP resolution
• Built in photoresistor for automatic adjustments
• Mounting
• Camera is mounted through a hole on the bottom of the rover frame.
• Movement of the camera is necessary because it is already aimed directly at where the dirt is collected, and the rover does not move during dirt collection.
• Interface
• Raspberry Pi MIPI (Mobile Industry Processor Interface) CS1-2 (Camera Serial Interface Type-2)
• Efficiently handles large amounts of data
• Data storage
• Four images are taken and immediately written to Raspberry Pi Zeros onboard sd card
• Saved under filename that is composed of a numerical identifier (like ‘0’ or ‘1’) concatenated with “.jpg”

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Rover Software Design

Software Environments:

• ARD Nano: C++
• Raspberry Pi Zero: Python

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Rover Payload Integration

• Payload bay sits in main body above electronics bay
• Measured ejection charges underneath piston
• Piston sitting on screws above it, when charges exploded, the piston pushes payload and parachutes out

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• Rover sits in compacted state in rocket body.
• When ejected, rover nichrome wire begins to short, keeps rover from expanding in rocket

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Nose Cone

Nose Cone Chute (24”)

Rover

Rover (44”) and Main (60”) Chutes

Piston

Hand Controller Description

Final Controller Selection: Android Phone w/ Custom Stylus Apparatus

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Controller type: Commercial software with custom interface

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• User Interface Design
• An android phone with a Bluetooth remote controller application inserted in a plastic case with two, stylus-tipped levers
• When user presses on a lever, the stylus will hit the touchscreen of the phone, sending Bluetooth data to the rover
• Custom interface accommodates for gloved hands
• Radio Type
• Bluetooth transceiver, built in which Android Phone
• Operation range: 5 m
• Android App: Arduino Bluetooth Controller
• Publisher: SA TECH
• Publish date: 2019

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Hand Controller Software

Software Environments: Android Studio (Java)

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Testing, Testing, 1, 2, 3

Ethan Wilens

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Rover Subsystem Testing

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Intent:

1. To verify functionality of the driving mechanisms, (screw test, motor test)
2. To verify the mechanics of the scooping mechanism
3. To verify the reliability of the electronics
4. To verify servo torque

Testing:

• Isolated test on legitimacy of propulsion by screws, by looking at velocity and direction
• Digging test for scoop by checking correct motion and timeage
• Testing on how electronics respond to different power sources and power demand
• Testing torque of servos to accurately program them

Rover Integration Testing

Intent:

1. To verify that each of the subsystems can be operation without any or little effect on the operation of the other subsystems.

Testing:

• Isolated test on legitimacy of propulsion by screws, by looking at velocity and direction
• Digging test for scoop by checking correct motion and timeage
• Testing on how electronics respond to different power sources and power demand
• Testing torque of servos to accurately program them

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Rover Functional Testing

Intent:

1. To verify the ability to dig the correct amount of dirt
2. To verify the ability for rover to drive the correct distance
3. To verify the ability to take pictures and transmit them
4. To verify the ability to survive a proper landing with parachute

Testing:

• Testing on multiple soils and depths with the use of the whole rover
• Testing for capability to choose distances for rover drive on different soils
• Testing on camera capture and transmission
• Testing parachute descent and release using rover

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Rocket Ground Testing

1. To verify calculated ejection charge amounts.
2. To verify that all shear pins properly shear on ejection.
3. To verify that the recovery devices and rover will properly deploy from the rocket on ejection.

Testing:

• Use primary ejection charge sizing, flight-packed parachutes, and dummy payload
• Activate ejection charges in the order that they will activate in flight

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Rocket Flight Testing

Intent:

1. To verify rocket and subsystem performance using the primary motor.
2. To gather data on flight via avionics package.
3. To verify performance of recovery system.

Testing:

• Motor selection: I600R
• Payload: Dummy payload mass (passive recording altimeter only) for first flight; fully active payload for second flight
• Flight test date: January/February (Pending)
• Launch site: Vermont, CRMRC

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Flight Operations

Rover Prep

• Turn rover electronics on
• Fold articulating flanges and tie nichrome wire around snugly
• Slide rover into designated rover bay.

Rocket Prep

• Fold and protect parachutes
• Insert piston and main parachute
• Insert rover parachute and rover
• Attach nose cone w/ shear pins
• Ejection charge prep (see slide 23)
• Attach electronics bay (to booster w/ shear pins, to payload w/ 8-32 machine screws)
• Build motor (per instructions - set ejection charge to TTA + 2 seconds)
• Install motor, motor retention (NOT igniter)

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Launch

• RSO check-in
• Upright on the pad
• Powerup electronics (see slide 23)
• Install igniter
• Retreat to safe distance, continuity check
• Verify rover is operational
• Launch

Recovery and Safing

• Power off all altimeters and rover components
• Check to make sure ejection charges have fired (follow slide 23 safing procedures if not)
• Field pack parachutes, return to prep area
• Clean motor casing
• Check rocket for damage

Program Schedule

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Component and Service

Schedule

• 6 I600G motors
• Ordered from Balsa Machining Services
• Rover parts to be cut on CNC Router
• On the first cut, the cnc scaled down the entire file
• Currently troubleshooting
• All other components have already been obtained
• No external services were required

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Program Budget

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Summary

• Rover prototyping and construction has begun
• Rover Electronics completed
• Rocket construction is mostly complete

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