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Colorado Space Grant Consortium

GATEWAY TO SPACE FALL 2010

DESIGN DOCUMENT

Lightning Rod

Written by: Christopher Bennett, Matthew Dickinson, Jesse Ellison, Matthew Holmes,

Trevor Luke, Sushia Rahimizadeh, Alex Shelanski

November 4th, 2010Revision D

Revision Log

Revision Description DateA/B Conceptual and Preliminary Design Review 10/5/10C Critical Design Review 11/2/10D Final Review 12/4/10

Gateway to Space ASEN 2500 Fall 2010

Table of Contents

1.0 Mission Overview……………………………………………..………………………….....42.0 Requirements Flow Down……………………………….……………………………...…..53.0 Design………………………………………………………………………………..……...64.0 Management…………………………………………………………………………..……155.0 Budget…………………………………………………………………………………..….176.0 Test Plan and Results…………………………………………………………………..…..187.0 Expected Results………………………………………………………………………..….218.0 Launch and Recovery…………………………………………………………………..….229.0 Data Analysis and Results……………………………………………………………..…..2310.0 Ready for Flight……………………………………………………………..……………..2611.0 Conclusions and Lessons Learned…………………………………………………………2612.0 Message to Next Semester…………………………………………………………………27

Team Lightning Rod of 27 October 4th, 2010


1.0 Mission Overview

1.1 Statement The mission of Team Lightning Rod is to send Zeus, a cubic balloon satellite built from foam core and equipped with two electromagnetic generators, to an altitude of thirty kilometers and harness the vibrational and rotational energy experienced during its ascent and descent. A microcontroller shall measure the amount of energy the electromagnetic generators produce. By analyzing the data collected, Team Lightning Rod shall determine if future spacecraft will be able to utilize energy generated by vibrational and rotational motion as additional alternative energy sources.

1.2 Goal and Background

The goal of this mission was to determine if vibrational and rotational energy can be harnessed as supplemental energy sources for future spacecraft. If this mission was successful, future spacecraft would be able to utilize these additional sources of energy, thereby providing their projects with increased security and protection from complications due to power failure. One of the most common reasons for balloon satellite failure is power loss (C Koehler, 2010, personal communication, September.) Most satellites rely on stored battery power and solar energy to power their systems. Batteries are not ideal because they do not last infinitely and can only be recharged when solar panels receive direct sunlight. When batteries are subjected to cold temperatures, they lose their charge. Solar panels limit the spacecraft because they must be large enough to provide energy. Also, solar panels are fragile and break easily when the satellite encounters debris or atmospheric turbulence. Solar panels are particularly vulnerable when the rectangular body of the solar panel extends out from the satellite and is narrowly attached to the structure. Because satellites are limited in their ability to power systems, energy supply is the satellites most important system. If power fails, all other systems fail. Thus, additional sources of power are greatly needed. The energy harnessed from vibrations and rotations is not expected to be enough to fully power all satellite systems. Nonetheless, it would prolong the life of a satellite and prevent mission failure.

The idea of generating power from vibrations was researched by students at the University of Southampton in England. The students developed a micro scale vibrational generator that was capable of powering wireless sensors. Although the design was only experimented on an air compressor, they stated in a journal that was submitted to the Journal of Micromechanics and Microengineering that they believe similar and suitable vibrations could be found in airplanes as well. In a book called Energy Harvesting Technologies by Shashank Priya and D. J. Inman, it was also discussed that there is an observed increase in power generation as generators increase in size. The generator developed by team Lighting Rod was subjected to an environment comparable to airplanes and the environment during flight. Also, its design is larger than the design developed at the University of Southampton, and thus more efficient. Therefore, it was anticipated that the vibrational generator developed would produce more power than the University of Southhampton’s.



By testing two generators that harvest the energy from rotational and vibrational motion, Team Lightning Rod analysed the efficiency of the designs and determine if either design could be used to generate energy for future spacecraft. Research can be found on similar instruments that were developed for the purpose of non-aerospace applications, which shall serve as the basis for the initial developments for the rotational generator. Students at the Imperial College in London also developed an energy harvester for powering wireless sensors using the rotations of the harvester's environment to create a dynamic magnetic field. As they stated in a paper titled Wireless Sensor Node Using a Rotational Energy Harvester with Adaptive Power Conversion, they sought a compliment to vibrational energy harvesting technology in order to maximize the potential of a given mechanical system's ability to gather energy. Their design consists of a mass atop a rotational disk that is offset from the center. Team Lightning Rod chose to arrange their magnets uniformly on the outer edges of the disc for the purpose of maintaining higher rotational speeds.

Team Lightning Rod expects that this project will enable an alternative energy source for future spacecraft by utilizing generators to capture kinetic energy. The team expects that the rotational generator will produce the largest amount of energy as the satellite is expected to rotate more than vibrate.

2.0 Requirements Flow Down

The requirements flow down is designed to portray how the requirements relate to the objectives and the goal. The goal is derived from the mission statement. The level 0 requirements are the mission objectives. The mission objectives are derived exactly from the goal and mission requirements presented by Space Grant. Each objective has several requirements underneath it that explain how it will accomplish the objective. The requirements are considered level 1 requirements on the flow chart. In the chart, the name of the objective or requirement is in the left column, the middle column has the specific objective or requirement, and the far right column shows where that specific goal or requirement is referenced.

The goal of Team Lightning Rod was to send a balloon satellite equipped with two electromagnetic generators to an altitude of thirty kilometers to determine if the kinetic energy from vibrational and rotational motion can be harnessed as supplemental energy source for future spacecraft.

Objective Mission Objectives Level 0 ReferenceO1 Fly a satellite to 30 km Goal (G)O2 Keep the internal temperature of the satellite above -10 degrees Celsius Goal (G)O3 Keep the overall weight of the satellite below 1200 g Goal (G)O4 Fly a Cannon Camera and the HOBO datalogger on the satellite Goal (G)O5 Capture and store vibrational energy using the vibrating electromagnetic generator Goal (G)O6 Capture and store rotational energy using the rotating electromagnetic generator Goal (G)O7 Compare the results of the rotational generator and the vibrational generator to see

which one is most effectiveGoal (G)

Requirements Objective 1 Requirements Level 1 ReferenceO1.R1 Satellite Zeus shall be attached to a helium weather balloon that shall carry it up to

30 km.O1



O1.R2 Satellite Zeus shall be attached to the balloon on a piece of rope that shall run directly through the center of the satellite.

O1

O1.R3 Satellite Zeus shall be kept stable on the rope by using washers and clips. O1

Requirements Objective 2 Requirements Level 1 ReferenceO2.R1 Satellite Zeus shall be kept above -10 degrees by using an electric heater that shall

be created by Team Lightning Rod and shall be powered using 9V batteries.O2

O2.R2 Satellite Zeus shall have ½ inch foam insulation to keep the Satellite above -10 degrees Celsius

O2

O2.R3 Satellite Zeus shall also have no holes to contain the heat in the satellite. O2Requirements Objective 3 Requirements Level 1 ReferenceO3.R1 Satellite Zeus shall be less than 1200 grams by keeping a very meticulous budget

that keeps track of the weight of every piece of equipment that shall be on the satellite.

O3

Requirements Objective 4 Requirements Level 1 ReferenceO4.R1 Satellite Zeus shall fly the Cannon camera to capture photos of near space. O4O4.R2 The camera on Satellite Zeus shall be programmed ahead of time so that it shall

work independently of all other electronics during the flight.O4

O4.R3 The HOBO datalogger shall be a standalone item in the satellite that shall record the internal temperature, external temperature, and relative pressure as measured by the sensors.

O4

O4.R4 The HOBO datalogger information shall then be used to determine the satellites position at certain times during the ascent and descent of the satellite.

O4

Requirements Objective 5 Requirements Level 1 ReferenceO5.R1 The electromagnetic generator shall have magnets that vibrate across a copper coil

as the satellite vibrates, thus producing an electric current.O5

O5.R2 The created energy shall then be held in a capacitor. O5O5.R3 The amount of energy in the capacitor shall be constantly measured and recorded

by the data storage device on the microcontroller.O5

Requirements Objective 6 Requirements Level 1 ReferenceO6.R1 The electromagnetic generator shall have magnets that rotate across copper coils

as the satellite rotates around the flight string, thus producing an electric current.O6

O6.R2 The generator energy shall be held in a capacitor. O6O6.R3 The amount of energy in the capacitor shall be constantly measured and recorded

by the data storage device on the microcontroller.O6

Requirements Objective 7 Requirements Level 1 ReferenceO7.R1 After Satellite Zeus is retrieved, the data from the two generators shall be uploaded

onto a computer for analysis.O7

O7.R2 The data results shall be documented as a function of time and also in reference to the information retrieved by the HOBO datalogger so that the best results at the relative moments of the flight shall be known.

O7

3.0 Design

3.1 Concept

Utilizing principles defined by modern electromagnetic theory, two generators on-board Zeus were designed to produce electricity derived from the mechanical oscillations of eight



neodymium magnets near a fixed copper coil per generator. The vibrations move the magnets, inducing a magnetic flux across the copper coil, as described by Faraday's Law. The magnetic flux across the copper coil drives a current. The force on the charges from the magnetic field shall oppose the change in magnetic flux and drive the current in the coil, according to Lenz's law.

Satellite Zeus featured two electromagnetic generators. One harnessed energy from vibrational motion, the other captured energy from rotational motion. Each is connected to a separate electrical load that is monitored by a microcontroller. The load seen by the generators was in the form of a capacitor bank. The bank has a limited capacity, so the microcontroller was to monitor and empty it when it was halfway filled. Each time the bank was emptied the micro-controller would register the dump. This data shall be used to calculate the total energy created. There are four components that were considered in the model design of the vibrational generator: a magnetic field, a coil, a vibrating mechanism, and an electric circuit (or load). A coil made of copper is fixed to the frame of the spacecraft and is inside a set of semi-freely oscillating magnets. There are two sets of magnets, two square neodymium magnets of alternating polarity for each set, each placed near one side of the copper coil. The vibrating mechanism, in the form of spring metal, supports the bidirectional movement of the magnets, which together creates a magnetic flux when experiencing acceleration from force. The ends of the coil are connected to a circuit capable of accumulating the energy generated, as well as manipulating the current as desired to support the objectives of the experiment. The rotational generator was designed considering the same electric laws, but has a different method of creating the moving magnetic flux. There are two copper coils fixed to the body of the satellite. Sitting above the coils is a free spinning disk with eight equally spaced neodymium magnets. The disk rotates freely about an aluminum pole over the copper coils, creating the moving flux that then drives a current in the coils. The coils are connected in parallel and then to an electrical load identical to that used by the vibrational generator.

For the duration of the flight, energy shall be harvested from the local environment via the generators and stored into a custom designed capacitor bank. Diodes regulate the direction of a dynamic current flow produced by the generator. A full-wave rectifier was implemented in order to ensure a single output polarity, as well as a direct current instead of an alternating current. A full-wave bridge rectifier was used instead of a half-wave rectifier because it is more efficient. The rectifier was designed with 4 diodes arranged in a “diode bridge” configuration that feeds the load. The load is a single capacitor bank for each generator. A capacitor bank was constructed by connecting ten tantalum capacitors is parallel. This construction technique is known as multi miniature capacitor bank, or MMC bank. A MMC bank was chosen partly because of the robustness of tantalum capacitor. Due to the fact that the MMC shall be subject to low pressure and extreme temperature, it was built to withstand a large amount of abuse. The other factor that determined the construction technique was the low capacitance of tantalums for their cost. Many small capacitors in parallel are much more cost effective when compared to a single high capacitance tantalum capacitor. To solve the issue of the generators possibly over charging the MMC and damaging it, the voltage shall be constantly monitored. When the MMC bank is half-filled, the bank shall be shorted and the energy stored shall be dumped. When this occurs, the microcontroller shall make note within the data timeline. A relay will be used to short out the MMC and dump the energy.



The data associated with the generator shall be continuously recorded for the duration of the flight and stored on a separate data storage device. The information that is stored onto the micro-controller shall include the data from all of the sensors accept for temperature and humidity. Team Lightning Rod shall analyze the temperature and humidity data using the HOBO’s “Boxcar” program and shall analyze the generator data using Matlab and Excel as these programs are best suited for disseminating this information. The team shall also match data from both the HOBO and Microcontroller Data Storage on a single timeline and determine any existing correlations. These correlations may include: energy output during ascension, energy output during burst, and energy output during the subsequent fall.

3.2 Math to Design

In designing our generators, four goals were realized in order to achieve maximum power generation. The dimensions of the coils, the optimal load resistance, the power generated by the vibrating generator, and the power generated by the rotating generator were the goals emphasized in the design of the generator system.

The fundamental principle that defined the goals of the dimensions of the coils and the design of the circuit load was maximizing the electromagnetic force which in turn means maximizing the electromagnetic damping of the system since the two values are directly proportional. In order to increase the electromagnet damping, Dem, the following equation was considered:

whereRL is the equivalent resistance of the load, RC is the resistance of the coil, the term jω LC is

the impedance of the coil/inductor, N is the number of turns in the coil, and dφdx is the flux

linkage gradient. The goal for the coils was to achieve a high number of turns to increase the voltage while achieving a short coil length in to decrease the coil resistance and increase power. This involved a higher fill factor of the coils, and winding the coil as tight and as orthogonal as possible. In order to achieve optimal dimensions of the coils that both increased number of turns N and decreased RC, the equation

was utilized. ri is the inner radius of the coil, ro is the outer radius, and LW is the wire length. To minimize the denominator to be as low as possible without reducing the area of the side of the coil (needed to satisfy a high value for the magnetic flux), the inner radius ri was minized while ro remainded constant for a given length of coil.

The achieve the optimal load resistance, the following equation was calculated to be the desired resistance of the load of the circuit:



where DP is parasitic damping.The goal for the vibrating generator was to maximize the flux density and optimize the resonant frequency of the beam after the masses was fixed onto it. The equation that was calculated to determine desired values for these factors is given by;

where Y is the base amplitude of the beam (determined by the environment), m is the mass on the beam, B is the flux density, l is the length of a coil side, and ωF is the resonant frequency. The majority of the factors included in the equation were determined previously. Flux density B was increased by obtaining high strength magnets, maintaining a 90 degree angle between the magnets and the coils, and increasing the area and number of turns per coil. The most important and influential factor in the power generated is the resonant frequency ωF. It was determined that the optimal ωF is achieved when it is equal to the frequency of the environment, so that parasitic damping is minimized. Since the vibration frequency of the environment was yet to be known at the time of the generator design, the frequency of the beam was adjusted to 50 Hz by modifying the length of the beam.

The goal of the rotating generator was to make it capable of rotating as freely as possible, since the power output is determined by the frequency of rotations and inversely proportional to RL which was previously optimized.

3.3 Plan

Team Lightning Rod ordered many of its necessary hardware components from the following places:

Magnets4less.com Neodymium magnets

McMaster.com Spring Steel

McGuckins Machine Screws Aluminum Tape Aluminum Tube Aluminum Flat Plate Bearing Nuts 9V Batteries

Mouser.com LDO Regulator Data Storage device

SwitchesProvided by ITLL

Plexi-Glass 30 ga. Copper Wire

Provided by SpaceGrant Aluminum tape Anti-abrasion washers Canon Camera Foam Core Sheets Heater HOBO Hot Glue

SparkFun.com Microcontroller Accelerometers



Development board*Cost and part number are shown in the budget

Team Lightning Rod cut the plexi-glass and formed the basic structure of the two generators. After creating the structures of the generators, the plexi-glass was attached to the machined spring steel using machine screws. The magnets then were attached on the end of the spring steel, and the copper wire was placed between the magnets. This was the vibration generator for Zeus. Similarly to the vibration generator, plexi-glass for the rotational generator was cut and magnets were fixed into their respective locations using hot glue. A bearing insured that the generator was free to turn the plexi-glass housing the magnets together. The generators were then tested to make sure that the conceptual design worked. The next system that was created was be the structure of Zeus. To begin constructing the structure, Team Lightning Rod cut foam core into the 2-dimensional cube pattern. Then, the 2-dimensional cube pattern was transformed into a 3-dimensional cube. The holes for the string attachment were cut and the string attachment was added to the cube through two washers, a tube, and the paper clips. Testing of the cube’s durability then ensued with the Whip Test, Drop Test, and Kick Test. Once the structure was known to have a durable design, Team Lightning Rod assembled all electronics according to the functional block diagram. Finally, the constructed project was tested with a Cold Test and a vibration test to make sure that everything was insulated and working properly. The Team then made necessary changes, placed contact information and an American flag on Zeus, and launched it.

3.4 Diagrams and Drawings



3D Isometric View

Rotational Generator First Revision


14 cm


Vibrational Generator First Revision


15.7 cm

Bearing

Magnets

Coils not shown (they’re attached to the structure)


Unfolded View


Spring Steel

Coil

Magnets


2D Unfolded with Dimensions



4.0 Management

Team Lightning Rod was managed by Trevor Luke. Each member held a vital role in the project and all members contributed to construction and finalization of the satellite Zeus and its components. Each team member was assigned a formal role and assistant duties to ensure that not only one person is working on each aspect of the satellite. Finalization of Zeus is estimated to occur two weeks before launch. All of the roles of team members are detailed in the charts given below:

4.1 Organizational Chart

NAME TITLE ADDITIONAL RESPONSIBILITIESJESSE ELLISON ELECTRONICS HEAD DRAFTING/DESIGNMATT HOLMES BUDGET HEAD PROGRAMMING ASSISTANT/

DOCUMENTATIONMATHEW DICKINSON

STRUCTURE CO-HEAD TESTING ASSISTANT

CHRIS BENNETT STRUCTURE CO-HEAD PRESENTATION COLLABORATORTREVOR LUKE TEAM LEADER TEAM SCHEDULING/ COMMUNICATIONS/

DOCUMENTATION

ALEX LOUIS TESTING HEAD FILMSUSHIANS RAHIMIZADEH

PROGRAMMING HEAD MISSION DESIGN

ALL ALL TEAM MEMBERS WILL ASSIST IN EVERY ASPECT OF THE PROJECT.

4.2 Flow Chart



4.3 Schedule

Complete proposal and presentation and submit online Due 9/16 by 7:00 amFill out order form and order hardware 9/23 at 11:30Team meeting 10/4 at 3:00Cut out generator structures 10/4Wrap copper coils 10/4Write presentation Due 10/5 by 7:00Team meeting 10/5 at 3:00 pmTest structure 10/5 to 10/8Assemble magnets and spring steel for vibrational generator 10/5Complete construction of vibrational and rotational generators 10/8Team meeting 10/10 at 2:00 pmTest and adjust generator design to optimize voltage 10/10Assemble and wire satellite 10/10 to 10/15Complete the wiring of satellite 10/16Team meeting 10/17 at 2:00 pmProgram satellite hardware 10/17 to 10/22Final Construction Completed 10/23Team meeting 10/24 at 2:00pmFinal Testing 10/24 to 10/29Project Finished 10/30Buffer Week 10/31 to 11/5Finish Critical Design Review 11/2Launch 11/6Write final presentation 11/30Finish Analysis and Final Report 12/4Team video due 12/4

4.4 Time Limitations

Throughout the development of satellite Zeus, Team Lightning Rod had many time limitations. First of all, the team had to develop its own generators. Originally, the team thought that this process would happen quickly, but they eventually realized that it was a long process. There were several potential designs that all proved to be unsuccessful. Some of the reasons for this were weight limitations, and functional failures. Then, the team also faced time limitations with the structure, as the design was originally much too large. Team Lightning Rod had to develop two prototype testing structures before developing the final structure used as the satellite. The final time limitation faced by Team Lightning Rod was the largest and most difficult: the programming of the micro-controller. It was realized two weeks before launch that the planned program would have inefficient space and thus needed to be renovated. To accomplish this, the team decided to attempt interfacing an SD card with the PIC microcontroller. The final parts to allow for this interfaced did not arrive until the Tuesday before launch, so the team could not begin programming until then. Once the programming began, the team realized that the task was much too complicated to accomplish within four days. Unfortunately, this time limitation was too much for the team, and the team therefore had to resort to plan B: recharging AA batteries.



5.0 Budget

** Team Lightning Rod talked to Professor Koehler and increased the weight restriction to 1200 grams for Satellite Zeus



6.0 Test Plan and Results

6.1 Whip Test

Team Lightning Rod did a whip test by attaching a prototype of the satellite to a string, the same type as the one used on launch day, and swung it around in circles. This tested both the ability of the structure to endure the whipping motion after burst as well as the structure’s ability to maintain a good hold onto the flight rope. In order to replicate the actual scenario, Team Lightning Rod filled the balloon satellite structure with objects in the appropriate locations to duplicate the weight of the actual equipment inside. Team Lightning Rod’s structure passed this test easily as the balloon sat retained a firm hold on the flight string and there was no damage whatsoever to the structure itself.

6.2 Drop Test

Team Lightning Rod also did a series of drops from varying height. This test was accomplished by dropping the structure from different heights in order to find its weak points. The satellite was weighted with objects to make it weigh about the same as the final satellite. The reason for this test was mainly to ensure that the balloon sat and the data within would not get destroyed upon landing. To ensure the safety of others while performing this test, the team made sure that nobody was in the vicinity of impact when dropping the balloon satellite. As this was the last structure test to be performed on that prototype, the balloon sat was tested until there was noticeable damage. After six tests a seal broke, probably due to the fact that the rock broke loose of the tape holding it down and smashed into the corner. Team Lightning Rod still judged this test as a success because the balloon sat only has to endure only one impact upon landing. The break can be seen in the picture below.



6.3 Generator Test

Team Lightning Rod tested the functional capabilities of both the vibrational and the rotational generator by creating a generator test. To accomplish this test, Team Lightning Rod attached the generators to an oscilloscope and manipulated the generators accordingly. For example the rotational generator was rotated and the vibrational generator was vibrated. Then, the oscilloscope read the energy output of both generators. It was determined after this test, that both generators were fully functional. The rotational generator produced an average of .1 V per second, and the vibrational generator produced an average of .045 V per second.

-0.20 0.00 0.20 0.40 0.60 0.80 1.00

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

Rotational Generator

Time (seconds)

Volts

Pro

duce

d

-0.40 -0.20 0.00 0.20 0.40 0.60 0.80 1.00

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Vibrational Generator

Time (seconds)

Volts

Pro

duce

d

6.4 Flight Simulation Test



Another test that was done by Team Lightning Rod was the flight simulation test. This test had two parts; first, the box was laid on the table with one side left open so that the team could see that the generators were performing correctly under the expected flight conditions (spun and wobbled it). The next stage of this test was to hang the fully sealed box over the edge of the table to see if it were balanced and if it would spin and shake as the team hoped it would. This was probably the most important test done because, although Team Lightning Rod had already tested and proved that the generators would work under vibration and rotation, they had not yet determined whether or not the flight would produce such vibration and rotation. The structure passed this test because the team was able to see that both generators were enduring enough motion to produce a discernable amount of energy.

6.5 Cold Test

Team Lightning Rod tested the ability of its structure to withstand cold temperatures. The structure was placed inside a Styrofoam cooler with five lbs. of dry ice. The test ran two hours. During the test, the Hobo was turned on, as well as the Camera and the Micro-controller. The purpose of the test was to see if all of the electronics, stayed on, and continued to work after the two hours of exposure to extremely cold temperatures. The total flight time of the satellite will be approximately two hours, thus the electronics only need to function in a cold environment for that time period. This test was successful because all of the electronics were still working after the two hours of the cold test.



4:48 PM 5:16 PM 5:45 PM 6:14 PM 6:43 PM 7:12 PM 7:40 PM0

5

10

15

20

25

30

35

40 Cold Test Data

Time

Degr

ees C

Coldest Temperature: .72

6.6 Imaging Test

Lastly, for the imaging test, the team turned on the camera to see if it would continuously take pictures. The test lasted 30 minutes and the camera worked perfectly, taking a picture every 20 seconds for the full 30 minutes that it was turned on.

7.0 Expected Results

Team Lightning Rod expected to have a very large amount of data to interpret results from. First, it was expected that the vibrational generator would generate at a measurable amount of energy (at least 1 mV) with each pass across the coil. The data acquired would be matched to that of an external accelerometer, which was attached to the magnets on the vibrational generator. The energy produced would be compared to the motion of the generator to validate how much energy is produced during the flight. Team Lightning Rod expected that the satellite would rotate more than it would vibrate. Thus, Team Lightning Rod predicted the rotational generator to produce slightly more energy than the vibrational generator. The generators would fill a capacitor bank with a charge, and the micro-controller shall measure the change in energy stored each time it checks the capacitor bank. The voltages on the capacitor banks for each of the generators would be measured by the microcontroller twenty times a second. The capacitor bank would be shorted out when it is approximately half full in order to ensure that the microcontroller measures accurate data. The capacitor bank shall be shorted out directly after a measurement is taken by the micro-controller so that data isn’t lost during the time it takes the capacitor to short out. The data measured by the micro-controller would be stored on an SD card. This would enable easy access to the data. After recovery, the SD card shall be retrieved and uploaded by a computer. The data would be analyzed using Excel and Matlab. Team Lightning Rod would condense the data to calculate the total energy produced and the efficiency of the generators. It was expected



that the results to look similar to the rotational and vibrational tests over a much longer time period (around 2 hours).

Team Lightning Rod expected that there would be an increase in the energy generated when the balloon passes through the more turbulent parts of the atmosphere. It is expected that the vibrational generator will generate a peak amount of energy just after burst. The performance of the generators should be semi-impervious to environmental factors. The change in temperature could have an effect on the energy output of the generators. When the temperature is at its lowest, there could be a slight increase in temperature output due to a decrease in the resistance of the copper wire in the coils. Thus less energy is lost to heat.

8.0 Launch and Recovery

Team Lightning Rod had some last minute complications, and therefore, had to modify its flight plan accordingly. The problem originally started when team members Jesse and Sushia realized that the code they were typing to record the data, and that we had used for testing was not going to work in flight, as the microcontroller did not have enough memory. In the week leading up to launch, they then proceeded to attempt interfacing our PIC microcontroller with and SD card so that there would be enough memory during flight to record the amount of energy being produced by each separate generator. They spent countless hours in the computer lab attempting to accomplish this task. When the time came to turn in Satellite Zeus, there was still no functional program even though Jesse and Sushia had worked for 24 hours straight on the program. The team then coordinated with Professor Koehler to create a deal allowing them to keep the satellite overnight so that the code could continue to be worked on. Sushia and Jesse then proceeded to work on the program for another 18 hours. Sadly, when it came time to depart for launch the program was still dysfunctional. Team Lightning Rod had to think quickly of alternate means of recording the energy produced by the generators. The team knew that the generators produced energy due to the various tests they had run, but they needed to find a way to prove that it produced energy during flight. They came up with an idea to use the generators to charge rechargeable AA batteries. Jesse ran to his room really quickly to grab the batteries, and the entire team proceeded to ride to the launch site in Trevor and Chris’ vehicles. En route to the launch site, Jesse wired the batteries up to a line of resistors to drain as much stored energy as possible. During the forty minute ride, the batteries continued to drain while the team did some quick renovations to Satellite Zeus. Since the original plan was to run everything through the microcontroller, and the microcontroller was not working, the team had to alter some wiring and move components around to make room for the new battery pack. When Team Lightning Rod arrived to the launch site, they met with Professor Koehler to attach the satellite to the flight string. Then, they used a voltmeter to measure the voltage of the battery pack so that they would have a baseline. Next, they attached the battery pack to the interior of the satellite with aluminum tape and sealed the satellite.

For launch, Jesse was chosen to hold and release the satellite and Trevor volunteered to release the GPS system. As the countdown ended, Jesse gently cradled the satellite, moved with it, and released it to be carried up by the helium balloon. Trevor had to run along with the GPS system to prevent it from hitting the ground. The team then all gathered together and watched the balloon ascend. After the other balloon was launched, the entire team rode in Chris and Trevor’s



vehicles for the chase. As the balloon ascended it proceeded southeast towards the town of Evens, Colorado. As the team drove east, the balloon continued southeast, and it was briefly within DIA airspace. Then, the satellite abruptly shifted direction to a northwest heading back towards the city of Greeley. The team was able to park on a county road and watch the balloon burst only slightly East of Greeley. The balloon then fell going almost directly east and only slightly south, where the satellite chasers were able to watch the satellites land in a pasture. After the group obtained permission to enter the land, the whole class marched through the pasture, and over a small stream to find the satellites strewn along the ground.When Team Lightning Rod came upon their satellite, they began to check the box. The structure had maintained little damage, and the camera had died and shut off. Once the all clear was given, Team Lightning Rod opened the satellite to a scene of complete destruction. The battery pack had fallen off during flight and the rotational generator was almost completely destroyed. It was assumed that the test was a failure, but the team used the voltmeter to measure the battery pack. The battery pack showed a slight net decrease in energy, and the team thought they had failed completely. Luckily, Trevor insisted that the batteries be tested individually. When the batteries were tested individually, it was discovered that a battery had been negatively charged, and the three others had all gained energy. Team Lightning Rod then took the satellite home, and began to evaluate the energy information, pictures, and HOBO information. The team did not end up with the ideal results originally planned for, but they did manage to prove that their generators produced energy during flight. Now, the team is in the process of fixing their design and code to prepare for a re-flight in the spring.

9.0 Data Analysis and Results

When Team Lightning Rod recovered their satellite, the first order of business was to record the data received. The data recovery method utilized was that of charging batteries with the power created by the Vibrational and Rotational generators. In order to prevent loss of voltage and thus data corruption, team Lightning Rod read the voltages on the individual batteries as soon as we were able to open our satellite. The initial charge on the battery pack before flight was 3.84 V. We connected the common ground of the generators to a center tap in the battery pack with the positive outputs of the generators connected to both poles of the battery pack. After documenting the initial charge, we added the center tap. In this process the battery that was connected to the positive output of the rotational generator was put back into the battery pack backwards. This was purely accidental but in the end turned out to be a benefit. In the new configuration, the battery connected to the rotational generator would not experience a reverse current flow. When we read the overall battery pack voltage after landing, we were not aware that this battery had been reversed. The final pack voltage was read at 2.59 V. When the batteries were measured individually two of the voltages recorded were negative. The next day the batteries were measured again and found to have the same magnitude of voltage but positive. The total voltage was 4.02 V. To try and explain the reversal of polarity of the batteries, Team Lightning Rod ran a reverse charge test. A battery of the same type that was used on the flight was connected to a current source backwards. The voltage was monitored as the battery drained. The battery did reach a charge of -.19 V but as soon as the current source was removed the battery returned to a charge of .83 V. This showed that the batteries are not able to retain a negative charge. Assuming that all the batteries were in reality in a state of positive charge, having the battery connected to the rotational generator installed backwards accounts for the discrepancies in the measured total



battery pack voltage. From this it was determined that the battery connected to the rotational generator was installed backwards and the polarity was due to human error.

Due to an error in placing the ground connection in the battery pack, three batteries were connected to the Vibrational generator and only one battery was connected to the Rotational generator. On landing, it was found that the energy storage battery pack had come loose from its mounting and destroyed the Rotational generator. We recreated the situation by re-attaching the battery pack to its mounting spot using the same method as on the flight. The satellite was then shaken moderately and the battery pack fell after only thirty seconds. From this failure and a large likelihood that the Rotational generator was jammed when the satellite was closed we concluded that the total battery pack voltage increase was due entirely to the Vibrational generator. This translates into an increase of .18 volts. The batteries used have a capacity of 2450mAh giving a total capacity of 7350mAh. This quantity can be used along with the voltage increase to provide a total energy value. This value is 1232 mWH or 1.323 Watt-Hours. In joules this is 4762.8J. Given a total flight time of around 8100 seconds the average power output by the Vibrational generator was .588 W.

To determine how the Vibrational generator compared to commercial photovoltaic cells the cost per dollar was calculated. For a small business to build the Vibrational generator it would cost $11.93 per Watt. However, in mass production it is estimated that the cost of materials would be reduced to one tenth that of internet order parts. This equates to $1.10 per Watt. The cheapest photovoltaic cells are $2.30 per Watt. This shows that harnessing the Vibrational energy of any environment would be more cost effective that using solar power.


Attempting to negatively charge the battery

Battery Connection Schematic


Finally, Team Lightning Rod had to evaluate the temperature and relative humidity data from the flight. After recovering the satellite, the HOBO was plugged into a computer and the results uploaded from flight. The team then proceeded to transpose the data into a graph. It was determined from evaluating the data that the team briefly dropped under the required temperature for flight, as the satellite reached -12 degrees Celsius for about six minutes directly after burst. Because the internal and external temperatures at this moment were almost identical, the team thought that as the satellite was falling, the cold air was entering the satellite directly through the camera hole. This would allow the cold air to hit the HOBO internal temperature sensor almost directly, thus explaining the almost equal temperatures. It was also determined that neither the temperature nor the relative humidity had any effect on the data.

Temperature

Humidity



10.0 Ready for flight

Work has been done to ready the payload for re-flight. Both generators have been reconstructed, and the set of 4 rechargeable batteries have been removed since it was determined that they were the cause of the broken generators. Testing was done to verify that the source of this malfunction of the generators to indeed be the rechargeable batteries that came loose during flight and interfered with the rotating generation, causing it and the vibrating generator to break. In a vibe test with the payload that included the rechargeable batteries as they were attached to the box during launch, it was observed that the batteries came loose in the satellite. After the generators were rebuilt, the payload underwent another vibe test, which proved successful without the rechargeable batteries. To verify an output, an oscilloscope probed the ends of the coils from the generators to produce a voltage waveform similar to the waveform produced before the flight. To ensure that no internal parts will loosen during flight, hot glue will be applied to every single part and component that poses the danger of detachment from the structure of the satellite.

The design of the structure of the satellite proved to be worthy of re-flight since it performed as expected during the experiment. The HOBO datalogger, as well as every other component of the payload beside the rechargeable batteries, will be used again in the case of another flight.

To measure the voltage output of the generators, the original PIC 18f4520 micro-controller will be used instead of the rechargeable batteries to provide more accurate data during in-flight monitoring of the generators and the forces acted upon the payload. The code that will be programmed onto the micro-controller will be altered to enable the storage of data onto an SD card to allow for the necessary amount of data storage. The payload will be activated by a single switch that will power up the micro-controller. It is projected that every part of the payload will remain in its current condition for more than 6 months.

11.0 Conclusions and Lessons Learned

Both of Team Lightning Rod’s generators produced energy on ground. The vibrational generator was successful and produced energy during the actual flight. It produced a total of 4.6728 kJ of energy during flight; however, Team Lightning Rod was unable to collect any data regarding when the generator was gathering the most energy due to the programming failure. The rotational generator faced complications and failed during flight, thus producing no detectable energy. The team discovered that the battery pack, which was taped to the central axle at the last minute, would have fallen almost immediately after launch. The rotational generator had four magnets break off when the battery pack fell onto it. Team Lightning Rod believes that the rotational generator became stuck against the sides of the satellite when the satellite was assembled, preventing it from rotating and generating power.

The members of Team Lightning Rod learned many lessons about engineering during this project. Engineers must understand what data needs to be collected and start programming as soon as they can because it is one of the most important and challenging parts of any project. They learned that they needed to manage their time better and maintain a strict schedule. The team needed to have more buffers for failure to avoid a critical time crunch at the deadline. Even simple experiments have unforeseen challenges. They learned that designing their own



components takes up valuable time. Team Lightning Rod learned to utilize their resources, especially people, to aid them in their experiment.

12.0 Message to Next Semester

Building a BalloonSat is a lot more work than one anticipates. There are many unexpected problems that arise during construction of a satellite. Schedule to finish a few weeks ahead of time to leave space for troubleshooting. It is a miracle if you don’t encounter some problem with your satellite, so anticipate and allot time accordingly. Also, never underestimate the amount of time needed for software. Programming can be a killer and without the ability to collect data, your experiment could be worthless. Start all aspects of design on your satellite right away so that you are able to properly allocate your time and efforts. When making “homemade” parts, never put off their construction until later when you could build them now. They will always need modification and the earlier you can assess what needs to be changed, the better. A good approach to getting things done is to divide into smaller teams within your team. Using this strategy, you can assign certain aspects of the project to each smaller team to make sure that they get done. Finally, this class is extremely time consuming. If you are not dedicated, then transfer out. You will need to devote about ten hours per week to this class and your team can’t afford members who are not pulling their own weight. It is a wild and stressful ride, but you will have a blast doing it.


spacegrant.colorado.edu · web view, a cubic balloon satellite built from foam core and equipped...

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