Critical Design Review

Mission Objective “To collect data from a custom radiation sensor in a high altitude environment”

Design Team MEEECS Laurie Smoot (EE) Tiffany Heetderks (EE) Rachael Luhr (CS) Stephani Schielke (CS) Katie Schipf (ME) Elizabeth Clem (MET) Advisors Dr. Brock LaMeres – Electrical and Computer Engineering Angela Des Jardins – Montana Space Grant Consortium Hunter Lloyd – Computer Science Robb Larson – Mechanical and Industrial Engineering Sponsor NASA

Risk Analysis Potential Risks: 1.) Parachute fails to deploy 2.) Parachute becomes tangled 3.) Equipment becomes too cold 4.) Sensor receives no strikes 5.) Power System fails, data lost 6.) Batteries shake loose 7.) Loose connections 8.) Code fails 9.) Lid becomes loose

System Architecture Arduino Mega 2560 Adafruit Data Logger Shield Wide-Temp SD card DC/DC Converter- part #CC6-0503SF-E Energizer Advanced Lithium Batteries ComputerElectricalMechanical 1” Polyiso Foam Fiberglass fabric & Resin

Computer Program Flowchart

So far…. Using a function generator, we were able to capture and count pulses coming in on an external interrupt pin Computer

Cont…. We also have the Real Time Clock running with accurate time stamps. In this example, it prints every three seconds Computer

Cont…. This is an example of initializing, writing to, and reading the SD card Computer

Test Plans Computer Subsystem Speed Test: Find out how fast we can write to the SD card Figure out how much space each data entry takes up bits + timestamp minimum Compare writing data in a.csv file and a.txt file Expected Results: To be able to write to the SD card: fast enough with sufficient accuracy Trials: ∞ until it works Computer

Test Plans Computer Subsystem Cold Test: After the ME’s have completed their cold test, we will run the computer system inside the box in the cold lab to ensure functionality in target environment After determining the system functions, we will write to the SD card to check the speeds To minimize use of cold lab, we will run with the EE’s trial Expected Results: Ability for computer system to run with outside temperature of -60°C Get data on write speeds to the SD card at target temperatures Trials: 1 Computer

Test Plans Computer Subsystem Interface Test: Connect all 32 inputs of the sensor to the computer Test the interrupts and fully integrate the sensor with the microcontroller board Expected Results: To accurately read data from all 32 sensor inputs Trials: ≥2 Computer

Test Plans Computer Subsystem Monitoring Test: Get the Real Time Clock (RTC) running correctly within the Timer/Counter ISR( ) Use the RTC for timestamps to monitor the power system Expected Results: Get an accurate timestamp in case of power system failure Trials: ∞ until it works Computer

Further Developments While waiting for launch, we will develop a program to read data retrieved from the SD card If using.csv, we can easily transfer the data to a spreadsheet If using.txt, we will develop a script to convert the data into useful format Computer

Bill of Materials Computer

Assembly - Electrical Electrical

Assembly - Electrical DC/DC Converter Schematic: Electrical 51k

Test Plans Electrical Subsystem Burnout Test Test Plan: Power radiation sensor and computer system by batteries Test lifetime of batteries Check for overheating of the DC/DC converters Expected Result: Batteries should power entire system for 4 hours DC/DC converters should not overheat Trials: 3 Electrical

Test Plans Electrical Subsystem Impact Test Test Plan: Place batteries in their holders and drop the payload from the roof of Cobleigh Hall This test will allow us to observe the durability of the battery box and the connections made by the batteries after impact Expected Results: The batteries should remain in the battery boxes with all batteries making solid connections Trials: 1 Electrical

Test Plans Electrical Subsystem Cold Room Test Test Plan: Place payload in cold lab at -60 C for 45 minutes allowing the computer system to monitor voltages throughout test Expected Result: Verify correct voltages are produced at appropriate outputs Number of Tests: 1 Electrical

DC Burn In Test Assembly Electrical

DC Burn In Test Analysis Electrical

DC Burn In Test Analysis Cont. Electrical

Bill of Materials - Electrical Electrical

Thermal Effects of Radiation: G = 1353 W/m 2 αGαG ρGρG Q space = εσA s (T box 4 - T space 4 ) Q earth = εσA b (T box 4 - T earth 4 ) Q power Thermal Properties of Fiberglass Fabric: Reflectivity (ρ) = 0.15 Absorbtivity (α) =0.85 Emmisivity (ε) = 0.85 Stephan Boltzman (σ) = x [W/m 2 K 4 ] Area of sides (A s )= m 2 Area of bottom (A b )= m 2 Q power = 3.5 W Q space = 4.46 W Q earth = W αG + Q power = 4*Q space + Q earth + 6*Q cond/conv Thermal Analysis Mechanical

Thermal Analysis Cont. Thermal Effects of Conduction/Convection: R convection R fiberglass R polyiso T∞T∞ T∞T∞ T out T in Thermal Properties and Calculations: Q cond/conv = A total (T in – T ∞ )/ R total Q cond/conv = 2.88 W Total heat transfer Area (A total ) = m 2 R total = R convection + R fiberglass + R polyiso R fiberglass = [m 2 K/W] R polyiso = [m 2 K/W] R convection = (0.1 – 0.86) [m 2 K/W] T in =[ (Q cond/conv * R total )/ A total ] + T ∞ T ∞ = (216 – 280) K αG + Q power = 4*Q space + Q earth + 6*Q cond/conv T in Mechanical

Thermal Analysis Cont. Mechanical

Thermal Analysis Cont. Internal Temperature Range of the Payload: Altitude Range: 5,000 – 100,000 ft External Temperature Range: -60 C – 10 C T in =[ (Q cond/conv * R total )/ A total ] + T ∞ Mechanical

Force Analysis Constants: Gravitational Acceleration: g=9.807 m/sec 2 Projected Area of Payload: A= m 2 Stopping Distance: s=0.025 m (high fall) s=0.01 m (low fall) Mass of Payload: m=1.236 kg Density of air: ρ= kg/m 3 Drag Coefficient-for a rectangular box: C d =2.1 Final Velocity: v f =0 m/sec Equations: Terminal Velocity: v t =√(2*m*g)/(ρ*A*C d ) Drag Equation: D=(1/2)*C d *ρ*v 2 *A Acceleration Equation (accounting for drag): a d =(m*g-D)/m Velocity from Drop Height: v=√2*a d *h Deceleration Upon Impact: a i =v i 2 /(2*s) G-Force: g f =a i /g Mechanical

Force Analysis Cont. HASP Requirement Terminal Velocity ***Cobleigh Roof Drop Avg. Descent Rate (BOREALIS) Calculation for highest test drop height Impact Velocity (m/sec) 3.13 * * **Height (meters) * *3.5 Deceleration at Impact (m/sec 2 ) ,5227,2292,9033,432 G-force (g’s) * *Starting point-other calculations made from these numbers **Drop height required to gain given velocity or G-force (HASP) ***Measured from southeast parking lot Mechanical One-dimensional (vertical) calculations for g-force:

Force Analysis Cont. Comparison of G-force’s from Various Drop Levels: Mechanical

Drop Test Analysis The following was obtained for a drop test analysis of the payload system: A DAQ system programmed to LabView in order to view results. An accelerometer connected to a power source capable of measuring +/- 250g with an operating voltage output max of 5V. The accelerometer functioned on 3 axis (x, y, z) in order to determine horizontal and vertical force to obtain an average overall impact force. A cable length of 5+ meters in order to achieve height for the drop test. Mechanical

Drop Test Analysis Procedure of the Drop Test: Payload was weighted to imitate the actual mass with the equipment ~1.24 kg. Accelerometer was duct-taped to the inside of the payload and extra foam placed inside to ensure stability of the device. The accelerometer was tested and calibrated for accuracy of results. 7 trials were performs starting at 0.5 meters and increasing to 3.5 meters. From the data, graphs were obtained, and observations recorded of the increasing measure of g-force upon impact. Mechanical

Drop Test Results Mechanical Data was recorded by the DAQ system by the change in voltage as the accelerometer experienced sudden changes in acceleration. Conversion from voltage to g-force: Each channel of the accelerometer (corresponding to x-y-z axis) recorded the output voltage relative to 2.5 V 2.5 V=0g point (5 V power source) Calibration from accelerometer data sheet is 8 mV/g Resultant (R) = √a 2 +b 2 +c 2 G=R/(8mV/g) Graph of raw DAQ data G-force upon impact for each axis

Drop Test Results After drop testing up to 3.5 meters, minimal damage was observed. Corners of payload was beginning to show wear, but no failure occurred. Average velocity of BOREALIS descent results in a lower g-force than when payload dropped from 3.5 meters, so our box will survive! Mechanical

Test Plans Mechanical Subsystem Force: Drop Test Test Plan: Test #1: Drop payload from height of 3.5 meters with stand-in equipment inside Specifically batteries and battery case (not sensor and computer system). Test #2: Drop payload from roof of Cobleigh Hall. Expected Result: #1: Check to make sure all equipment was stabilized in payload. #2: Velocity from roof drop is close to terminal velocity so this will provide an idea of whether the payload will survive if the parachute does not deploy. Trials: #1: Make any adjustments that are needed and repeat test until certain all equipment will be safe for landing. Mechanical

Test Plans Mechanical Subsystem Temperature Test Plan: Place payload in cold lab at -60 ° C for 45 minutes with a thermocouple inside Check the internal temperature at the completion of the test Expected Result: When ascending, the coldest air temperature the payload will pass through is -60 C and it will be in that temperature zone for about 30 minutes (45 min. test for a buffer). Our calculations show that the internal temperature should not drop lower than -40 ° C, which is the lower temperature limit for the electrical and computer operating systems. Variance from our calculations could result due to different atmospheric conditions. Trials: 1 Mechanical

Test Plans Mechanical Subsystem Radiation Test Plan: Flash radiation source on lid of box, with sensor inside. Expected Result: Radiation should not be obstructed and data should be logged. Trials: As many as necessary to ensure radiation strikes. If no strikes occur, design of lid will be altered. Mechanical

Payload Assembly External: The Payload is assembled from 6 separate Polyiso foam pieces to form the box frame. Two (2) sides 165 x mm Two (2) sides 115 x mm One (1) base 165 x 165 mm One (1) lid 165 x 165 mm All components are 25 mm thick unless otherwise specified Each section is glued together using gorilla glue, then fiberglass fabric is painted on using resin thinned with acetone. Four (4) loops of webbing will be glued to the box previous to fiberglass and resin to hook onto BOREALIS carabineers. Duct tape is used to secure the top of the box to the base. Mechanical

Payload Assembly Internal: Internal electrical and computer system is stacked vertically using proto-boards and connector pins. The computer system connects by a ribbon cable to the proto- boards. Extra foam scraps will be positioned in the extra space of the box in order to secure any loose parts. Mechanical

Bill of Materials Mechanical

Total Budget: Computer: $ Electrical: $ Mechanical: $76.34 TOTAL: $ $51.58 under budget!

THANK YOU!