DemoSat IV: RedRoverSat University of Colorado at Boulder Jaime Catchen, Chris Homolac, Emily Walters August 9, 2006

2 Mission Statement & Goals: RedRoverSat is an autonomous rover designed to measure wind speed and direction and the moisture of the soil at its landing site. This research hopes to be beneficial to understanding the objectives of the Astrobiology Field Laboratory. Launch Thermal system heats payload Payload lands C&DH senses landing After rover senses landing, rover detaches from flight line Rover moves four times in a pre- programmed path and stops for one minute to run experiments and record data Recovery Mission Timeline

3 Benefits to NASA: Students working on the design of autonomous payloads with moving parts The rover will perform experiments similar to those that will be part of the Astrobiology Field Laboratory

4 Project Management: Project start date: May 22, 2006 Science Chris Homolac – Wind Jenny O’Brien – Wind Emily Walters – Soil C&DH Jaime Catchen Chris Homolac Leon Slavkin Structures Rebekah Hanson Leon Slavkin Emily Walters Power/Thermal Chris Homolac Project Management Jaime Catchen

5 Design: Structure

6 Design: C&DH Atmega32 — — 32 Kb programmable flash, 1 Kb EEPROM — — 32 I/O pins — — 8 analog inputs — — Software in C programming language H-bridge Motor control

7 Design: Landing Sensors Accelerometer checks stability of the rover every 30 seconds for 5 min. Temperature and/or Pressure Sensors confirm that rover is not at high altitude. Safety Timer ensures that rover does eventually deploy, no single point of failure. Safety Timer If >30 Minutes Accelerometer If Stable for 5 min Control Timer 2:15 hours Temperature Sensor If >16 C Pressure Sensor If > 83 kPa Detach From Flight Line No Yes No

8 – – Soil probe measures the voltage across the two metals – – Driven by servo Design: Science Wind Soil NiCr Wire Panel for Wire 1 Panel for Wire 2 Servo mount

9 Design: Power & Thermal Power – –Lithium Polymer [11.1V 2100 mAh] n n Heaters/Main systems – –Lithium 9V Battery n n Deployment Nichrome Thermal –Series of (6) 5W 4 Ω Ceramic Resistors –Foam/Aluminum tape insulation –Thermostat Control Lithium Polymer Power Supply with insulation and heaters Lithium 9V Battery/ Resistance Heater

10 Design: Budgets Total Cost $ Total Mass 1658 g Thermal

11 Testing TestResults Subsystem CheckAll subsystems met requirements Rover path testRover can maneuver around obstacles Data logging testScience data was stored to EEPROM Drop testMild damage to Aluminum Frame Whip testNo damage to structure or nichrome circuit Full mission test (x2)Rover’s thermal subsystem kept components at required temperatures, Nichrome tried to melt line, servos deployed

12 Results Recovery Both wheels came off during landing Flight line Nichrome was broken Flight line torn Servos tried to deploy science experiments in proper orientation Soil probe bent, wind panel bent Wind Nichrome broken Post Flight No data stored to EEPROM Battery discharged to 8v H-bridge, battery, right motor, heaters, servos, AVR still in working order Motor gears stripped Wheel Hub Motor Shaft

13 Improvements and Lessons Learned Improvements to the Design Put wheels inside frame Write a byte to EEPROM periodically throughout flight code Put experiments inside structure or make rover a vessel for any experiment Mechanical detachment mechanism instead of Nichrome Lessons Learned No test like the actual flight Dealing with unpredictability of flight circumstances and landing site

DemoSat IV: Questions? University of Colorado at Boulder