Final Report
December 12, 2003
Empty Space Inc.
Michael Gainey
Brian Taylor
Miranda Mesloh
Katherine Schreiber
Corina Allen
Brett Anderson
Design
Our design structure was completely made out of foam core. It was twelve centimeters by ten centimeters by ten centimeters. The three features on the outside were the Elastic Memory Composite hinge, the bolts to fasten the rope and rod, and finally the temperature probe which was enclosed by a small plastic tube. We also had three layers on insulation on the outside along with a United States flag and our contact information. Upon opening the satellite, the first subsystem you would see is the cell phone. These components were placed at the top for easy access on launch day. Below the phone system were the two timing circuits. We had one circuit to operate the camera to take images every three minutes. The second timer was a cascading timer we created to start hinge deployment after sixty minutes. The HOBO, which was located below the battery pack for the timing circuits, measured temperatures both internally and externally. Our heaters were at the bottom next to the camera. Finally, at the bottom of our satellite was the camera. It was insulated separately to help prevent heat loss from the lens openings in the foam core structure. One last additional structural component is the metal rod which went through the center of our satellite to attach our Balloon satellite to the string.
Our first experiment was the cell phone. We planned on testing vertical range of cell phone technology and its durability up to thirty kilometers. This is done using digital recordings from cell phone transmissions between our satellite and one of our own cell phones. Our next experiment was the deployment of the Elastic Memory Composite hinge used to take split-view images and pictures along the horizon. To do this we have a single bladed hinge attached to the outside of our satellite using epoxy, which is insulated by four layers of a space/emergency blanket.
RFP Compliancy
We were compliant with most of the items required. We got images back of the Earth by using our split-view mirror. As described previously, we allowed for a HOBO, temperature cable, foam core design,two experiments, a flight string,a max weight of less than 800 grams, and no live payloads. Most importantly, no one was injured. As we will discuss later, we were able to calculate ascent and descent rates for the majority of the flight. Finally, we completed our final presentation, and this is our final report.
There were only two areas where we were not able to comply with our requirements. The first problem was keeping our internal satellite temperature above zero degrees Celsius. Unlike other groups, we did not put our HOBO directly next to our heater to accomplish this. As described later in this report, we determined that our insulation was just not strong enough. One of the reasons for this, which was out of our control, is the fact that we stayed in the Tropopause for an extended period of time. This extended exposure caused led to conditions much more extreme than we had anticipated.
The second failure to comply was in imaging the balloon during flight. We do not necessarily consider this a complete non-compliance due to the fact that we got perfect ground images. Also,the split-view images for the balloon seemed always overexposed. Furthermore, our satellite was at the bottom of the string, causing our satellite to whip around immensely, which also could have affected our images aimed at the balloon.
Budget
Mass:
MASS BUDGET #1: Predicted Mass (11/03/03)
SATELLITE PART / MASS (g) / BALANCE (from 500g)EMC Hinge / 3.9 / 496.1
Mirror / 8.1 / 488.0
Camera / 118.8 / 369.2
HOBO / 25.6 / 343.6
HOBO Temp. Cable / 9.3 / 334.3
Timing Circuit #1 / 28.7 / 305.6
Timing Circuit Battery Pack / 24.4 / 281.2
Timing Circuit #2 / 29.2 / 252.0
Recording Controller / 35.7 / 216.3
Digital Recorder / 25.0 / 191.3
Camera Film / 11.8 / 179.5
Camera Battery / 12.0 / 167.5
Resistor #1 / 6.2 / 161.3
Resistor #2 / 6.3 / 155.0
AAA Battery (Controller power) / 9.0 / 146.0
AAA Battery (Controller power) / 9.0 / 137.0
AAA Battery (Recorder power) / 11.3 / 125.7
AAA Battery (Recorder power) / 11.3 / 114.4
9V Battery (Hinge power) / 38.5 / 75.9
9V Battery (Hinge power) / 38.2 / 37.7
TOTAL / 462.3
Phone / - / -
Phone Battery / - / -
Structure / - / -
Timing Circuit #2 power / - / -
Insulation / - / -
Tape / - / -
Flag sticker / - / -
Our initial mass budget had our satellite weighing in at 462.3 g out of a potential 500g. After this weigh-in at the time of the pre-launch readiness review, the group began to feel nervous as the total mass only left us with 37.7g and we had yet to mass the phone, phone battery, structure, second timing circuit power source, insulation, any tape used, and the flag sticker. While items such as the flag sticker would surely be nominal, the phone and phone battery were a real concern and rightly so. The phone and battery ended up weighing in at a hefty 77.3g, 39.6g over what was left of our mass budget.
Below is our final mass budget and final parts used in the satellite. For this table, the balance is cumulative, adding the mass totals as parts are added.
MASS BUDGET #2: Final
SATELLITE PART / MASS (g) / BALANCEStructure + hinge + mirror + insulation + flag sticker / 147 / 147
HOBO + temp. cable / 34.9 / 181.9
Phone + battery / 77.3 / 259.2
Recorder + batteries / 35.9 / 295.1
Recorder controller + batteries / 43.2 / 338.3
2 Timing circuits + 1 battery pack / 96.2 / 434.5
Camera + battery / 130.9 / 565.4
Camera film / 11.2 / 576.6
Heaters / 38.9 / 615.5
Hinge batteries / 79.3 / 694.8
Heater batteries / 76.1 / 770.9
Aluminum tape / 3.7 / 774.6
TOTAL / 774.6
Clearly, the final satellite ended up weighing considerably more than our initial measurements and predictions. The heaviest components were definitely the batteries, which came as a surprise, especially since the group did not foresee requiring so many.
Finance:
One requirement of the satellite project was the group’s expenditures not exceed $200. Given this restriction, the initial budget was pretty well organized and thought out. It contained parts such as rechargeable batteries that could be re-used. As a result, the group was left with $36.42 at the end of the predicted/initial budget.
FINANCIAL BUDGET #1: (11/03/03)
Item / Cost / BalanceMirror, insulation material / 8.28 / 8.28
Digital recorder / 59.99 / 68.27
2 9-V batteries / 21.98 / 90.25
4 AAA batteries / 12.59 / 102.84
Recorder controller / 21.99 / 124.83
Radio Shack tax / 8.75 / 133.58
Phone and plan / 30.00 / 163.58
TOTAL / 163.58 / 163.58
The $36.42 remaining at the end of the initial budget ended up being used for testing, new film, and film development. The group is glad to have had this extra money, and to have landed just under the cost limit.
FINANCIAL BUDGET #2: Final
Item / Cost / BalanceMirror, insulation material / 8.28 / 8.28
Recorder (Radio Shack) / 59.99 / 68.27
2 9-V batteries (Radio Shack) / 21.98 / 90.25
4 AAA batteries (Radio Shack) / 12.59 / 102.84
Recorder Controller (Radio Shack) / 21.99 / 124.83
Radio Shack Tax / 8.75 / 133.58
Verizon Plan and Phone / 30.00 / 163.58
Resistors / 1.82 / 165.40
Dry Ice / 3.76 / 169.16
Dry Ice / 2.89 / 172.05
Electrical Wire / 3.21 / 175.26
New Film / 8.06 / 183.32
Film Development / 15.26 / 198.58
Results & Analysis
Our main results were from our HOBO temperature cable. The actual data is presented in the charts above. As you can see, temperature decreases proportionally with increasing altitude. At the highest point you can see several oscillations in the elevation of the satellite. This is also apparent in the rise and fall of the temperature during that same time period.
Due to the truncated length of our flight, we opened our satellite two hours after launch. At this time we discovered that our heaters were still functioning. As you can see above, however, the HOBO data shows that the temperature decreased dramatically inside the satellite during flight. This leads us to believe that the problem lay with the poor insulation, not with the heaters.
Shown below is a graph created from the data gathered aboard the GPS tracking system attached to our satellite, which we will compare to a graph explained on the next page.
In order to fill the requirements set forth by the RFP, we had to find a way to keep track of the speed of the rise and fall of our satellite, without using the GPS device’s data. To do this, we made use of the other information we were already required to obtain, the temperature. We used a fairly accurate approximation for the change in temperature compared to the change in altitude: a drop of 1° Celsius for every rise of 100 meters. Thus all we had to do was find the change in temperature per unit of time (we chose 1 minute), divide that number by the numbers of seconds in your unit (60 for us), and multiply that by -100 to get the velocity in m/s. The results are shown below.
The first thing someone who knew about this flight should recognize is that this data’s time period is shorter than that of the flight. This came about because an unexpected complication on launch day, what is called a temperature inversion. Because of the conditions on the morning of launch, the temperature actually rose with altitude for a period of time. When the temperature began to drop again, about 15 minutes into the flight, we could then successfully use our approximation. The same phenomenon was encountered on the way down, cutting off the accuracy of our data a few minutes short of landing. Other than this unforeseen complication, our data looks entirely credible. We average a velocity of around 12,000meters per hour (after conversions), which makes perfect sense since we rose close to 12,000 meters in close to an hour.
Conclusions
Our conclusions are based around one failureone partial success of our experimental subsystems. On the morning of the launch we activated the phone subsystem. By calling the phone from our own cell phone on the ground we got an initial connection prior to sealing the satellite up for launch. Once the satellite was air borne we were unable to get a connection with our phone. Prior to launch, we tested the phone inside the satellite to establish that the metal insulation would not cause interference. We believe that one possible failure was due to the extreme forces and motions which possibly caused a loose connection or short. Another possible cause of failure is the buttons on the face of the phone, which could easily have been pushed in such a way as to render the phone’s auto-answer useless. Once we landed and opened our satellite we saw that the phone lights were on so we know that power was not the problem with the phone system.
Our conclusion concerning the camera system is our camera must have fallen below its operating temperature. Our camera took 21 images with the last image at 8:58 in the morning. According to our HOBO data and the altitude information, our last image was taken right before our lowest internal temperature point. Once our satellite had landed on the ground and we got back to campus we tested all of our batteries in search of sources of failures. We found the camera battery was not dead and therefore the camera failure was not due to a power problem.
Number of Photo out of 22 / Time of Photo / Distance from Edge of Mirror to Edge of Photo10 / 8:24 / 4.6
11 / 8:27 / 4.5
12 / 8:30 / 4.5
13 / 8:33 / 4.6
14 / 8:36 / 4.6
15 / 8:39 / 4.6
16 / 8:42 / 4.6
17 / 8:45 / 4.5
18 / 8:49 / 4.7
19 / 8:52 / 5.0
20 / 8:55 / 5.0
21 / 8:58 / 5.1
Our most exciting conclusions came when we studied closely the last five pictures taken by our camera. As you can see in the chart, during the last few pictures, the edge of the mirror moved a full half-centimeter across the view of the camera. This is exactly the time in which the hinge was to deploy. Although the hinge moved slightly throughout the flight due to the forces being exerted on it by the movement of the satellite, there is no other place in our pictures with such marked and steady change as these last few. We believe this is enough evidence to prove that our system for powering the hinge worked well; the malfunction came after the hinge had partially deployed.
There are many possibilities as to why this occurred. We have a few facts, and a few ideas, to explain the reason for the hinge not deploying fully. We know for a fact that the satellite was hanging at the coldest temperatures of the flight during the time in which it began to deploy. This would possibly slow down the deployment, as did our decision, due to weight constraints, to power the hinge with eighteen volts as opposed to the full twenty-seven. We believe the hinge still would have deployed, had not there been another factor to affect its deployment.
Upon opening the satellite back on the ground, we found that one of the snaps connecting the two nine volt batteries to the hinge had come loose during the flight. This could be due to either an unfortunate bump against components nearby, or a difference in thermal contraction between the snap and the battery. Either way, we know for certain that the snap came free sometime between launch and landing. Although this one side was unattached, the other side of the snap was still fastened securely to the battery. This meant that the circuit could very well have been fluttering on and off throughout most of the portion of the flight in which the one side had come free.
There are a few possibilities as to what happened to cause the hinge to cease its deployment. After about five to seven minutes in which the hinge had been slowly heating, partially deploying, either the battery could have come free, or the batteries might have frozen and quit working, due to the colder than expected temperatures that our satellite reached. Another possibility is that the hinge was at too extreme a temperature for a full thirty minutes. After this length of time, the timing circuit turned off the power to the hinge, ending deployment. Due to the fact that our camera froze up just after a change became evident, the hinge might have kept deploying slightly longer than the camera photographed, and then cut out for one of the previously mentioned reasons. Although the hinge did not deploy completely, it did move enough for one of our teammates to remark upon its movement when it was back on the ground, although we all dismissed this as wishful thinking until seeing the pictures.
Our last conclusion we have arrived at is that our structural design was solid and sound. It stayed intact during launch, flight, and landing. There was no damage at all to any of our outer satellite or to any of our structural design.
Lessons Learned
Organizing and building a satellite is much more difficult then expected. From the electronics to the structures, each subsystem took more time and effort than first expected. Along these lines, scheduling is important. We realized that we should have padded our schedule to allow for needed changes, modifications, last minute bugs, and for more testing. Speaking of testing, we thought we had done plenty of testing on the subsystem level, but we realize we should have done more at the macro level. We did three cold tests, but we learned the day before launch that we should have used about eight or nine pounds of dry ice instead of only one pound of dry ice. This is knowledge that we did not have previously to do proper testing.
We discovered it is necessary to secure internal components tightly or else your equipment will get thrown around. We realized that this was the cause of at least half of our problems and failures.
Experiments should not be so complicated and costly that you cannot fully understand them nor test them properly. We ran into this problem with the cell phone. Obviously we are not cell phone creators, designers, or engineers and we did not completely understand all the little complications of a cell phone to test it. Also we had limited minutes and so it would have been very costly to do extensive testing.
Message to the Next Semester
Start early. Everything will be harder, take longer, and be more expensive than you think. Test, test, and test. Make sure you do plenty of tests on both a subsystem level and a macro level to make sure each system works and they all work together as a satellite. Do not buy rechargeable batteries. Yes they may be able to be recharged, but they do not charge fully after many uses and they are not reliable for testing or launch use. Buy lithium batteries, they are lighter, have more capacity, and are definitely worth it if you can afford them. Use plenty of insulation; go overboard on the space/emergency blanket. It is better to go overboard then to freeze your satellite. Split mirrors are the best for getting both the ground and balloon images; two birds with one stone. Talk to Tim May, take him presents on a weekly basis, bake him cookies, he WILL become your best friend for electronics. Make sure you secure your components very well inside your satellite before you seal it at launch.