Preparing for Balloon Launches

Introduction:

This week, the class prepared for the balloon launches we will be doing some weeks down the road. We are planning on using balloons to do both a mapping of campus and a high altitude balloon launch (HABL)We will be sending a digital camera up with the balloons and recording continuous shots or videos of the earth.  To ensure that everything goes smoothly with these two projects when the time comes, we had a lot of small tasks to complete over one three-hour class period. As a class, we had to construct rigs for the mapping and HABL balloons, test the parachute to ensure the camera will land safely, find the payload weights for the rigs, figure out how to keep the camera in continuous shot mode while up in the balloon, test the tracking device that will be used to find the balloon once it lands, and research how to fill the balloon and secure it to the rig later on.

Methods:

                Constructing the rigs:

                                Unfortunately, I was unable to participate much in the construction of the rigs, but I was able to speak with classmates and get the general idea for what we will be using. The designs for the two rigs are similar but differ in the way that they shield the camera. The mapping rig involves the top half of a two liter bottle to shield the camera. The camera will most likely be suspended by string within the bottle with the larger, open-ended side of the bottle facing down (Figure 1 and Figure 2). This way, the camera will be able to take photos of the campus unobstructed, but be blocked from any wind. For the HABL rig, we are using a Styrofoam bait warmer to shield the camera. Because the camera will be launched 90,000 to 110,000 feet into the atmosphere, the bait warmer is necessary to keep it from freezing.  There will also be several heating packs in the Styrofoam case. Another layer of Styrofoam insulation will be placed in the top of the case (I believe) as extra protection/heating for the camera as well. We are planning on cutting a hole through the case so that the camera will be able to record images of the Earth while still inside the case. Rubber bands are being implemented with both rigs to hold the button down for the continuous shot mode while it is in the air. The bottle and Styrofoam case will be attached by seven feet of rope to their respective balloons, though I am unsure of any further details in this part of the rig.

 

Figure 1: This is the basic design for the rig my class and I will use for our mapping balloon launch.

 

 

 

Figure 2: This is part of the rig that will be implemented with the mapping balloon launch. It also shows part of the design (the orange rubber bands) for the continuous shot which is discussed later.

 

Payload Weights:

                        The balloons have a specific payload weight that they can carry safely depending on their size. Therefore, we had to measure every item that will be included in the rigs and ensure that the balloon will be able to carry all the necessary equipment. We weighed items from carabiners to zip ties to the memory cards for the cameras and everything in between. We entered these weights into a spreadsheet in Excel and will add up all the equipment used in each rig for a total payload weight (Figure 3). For the mapping rig, we have already ordered a five and a half foot neoprene balloon.  It can carry a two pound payload and we made sure that we were within this two pound limit while constructing the rig. The HABL balloon will need to have a higher payload weight because the camera and bait warmer alone add up to about two pounds without any additional materials that are sure to be needed. Therefore, we decided on ordering a balloon that has a four pound payload weight maximum which should be more than sufficient for our HABL rig. It worked out nicely in a way because the balloon with the higher payload weight will also be able to travel higher into the atmosphere. Since the rigs are not entirely completed, we do not have exact weights for all the materials that will be included in the payload as of yet.

Figure 3: This list includes the description and weight of all the possible materials for our balloon launches. It is difficult to read, but it is clear that there were quite a few items to be weighed.

 

Parachute testing:

                        Another task that we had to complete in our class period was to test our parachute with a back-up rig. It is vitally important that our camera is able to safely land so that we can recover the footage (and also because cameras tend to be a bit expensive) from our launches. To test the parachute, we used a second, slightly smaller Styrofoam bait warmer in case something went awry, and tied it around the bait warmer(Figure 4). In order to simulate the weight of the equipment we will be using, we placed a full water bottle weighing exactly two pounds inside the bait warmer. We chose the two pound payload because it matched the payload for the balloon we already had (which we will be using for the mapping portion of the project), and had not yet determined the payload for our HABL launch.

 The next step was to throw the test rig and parachute from the highest point possible with a straight drop. Due to lack of access and high places in general, the best we could do was to throw the rig out of a fourth floor window in our science building (on the bright side we still got to throw stuff out of a really high window). After doing two test runs, the results were as good as we could hope for—the bait warmer was entirely intact after hitting the ground, and the water bottle was unharmed. I will discuss the accuracy issues with our test run in the Discussion section of this report.

Figure 4: This is the rig we used for the testing parachute launch with the back up bait warmer and the actual parachute that will be used in both the mapping launch and HABL.

 

Implementing continuous shot:

                        Perhaps the most important aspect of the entire project is ensuring that we will be able to remotely record imagery while the camera is in the air. To do this, we had to find a way to keep the camera in continuous shot mode for an extended period of time. The continuous shot mode will allow the camera to take pictures at a given length of time defined by the user. For example, we could set the camera to take a picture every three seconds until we bring it down to the ground. After the mapping launch, we will take these pictures and piece them together to form a single map. We were deciding between a one second and half a second time period, I believe, though I do not know our final choice.

 As far as we know, the best method of keeping the camera in continuous shot mode is by using rubber bands. Again, I did not participate much in this aspect of the project, so I do not have a full account. From my understanding, however, it was difficult to apply enough pressure on the continuous shot button for it to actually be in continuous shot mode. We tried using different types of rubber bands with varying length and width. It was also suggested that we tie a knot in the rubber band and place it over the button. I believe the best way to arrange the rubber bands was with two rubber bands wrapped around the camera with at least one holding a small pencil eraser over the continuous shot button (Figure 5).

Figure 5: This is the basic design my class and I are using to keep the camera in continuous shot mode while our camera is in the air during our balloon launches.

Implementation and testing of the tracking device:

                                In order to find the HABL balloon after it lands and follow its course as it travels through the atmosphere, we have to place a tracking device inside the bait warmer along with the camera. We are using a small, pocket-sized device that can be tracked online, though I am unsure of the brand. To test the device, we simply sent a student to walk around campus and followed them online to see where they had been. There were some issues with the battery life of the device, so we had to do this a couple times. We also wanted to test the longevity of the device, so a student volunteered to carry the tracking device with them for a couple of days (which fun for the professor to see I am sure). The tracking device was judged to be sufficient and will accompany the camera into the atmosphere.

                Filling the balloons and securing them to the rigs:

                                The filling of the balloons and securing them to the rigs will not be done until the day of the launch, but it is still important to set a strategy ahead of time. We found some instructions for this on the internet, but these seemed a bit odd and we deemed them inappropriate. Other online sources, http://www.sparkfun.com/tutorials/187 and http://www.toddfun.com/2011/02/20/high-altitude-balloon-launch-2/, used a 1 inch PVC pipe and some pipe fittings to fill the balloon, employing several zip ties to keep the balloon from floating away while being filled. Interestingly, one site stated that latex gloves should be used so as to keep oil from human hands from touching the balloon. Once the balloons are filled, it was suggested by these same sites to use zip ties to close up the bottom of the balloon. To secure the rig to the balloon we plan on using seven feet of braided rope, but I do not know how we are planning on securing the rope to the balloon. We are still unsure as to what method we will use to fill the balloon and will need to do more research.

 

Discussion:

                Although we accomplished quite a bit in our class period, there is still a lot left for us to do before we are prepared to launch our balloons. We have to finalize our rigs and make sure they will be within the payload limit of our balloons, and we have to find the best way to fill the balloon and attach the rig to the balloon. Students have been working with our professor outside of class to continue with these tasks, and we will hopefully have everything completed by the time of our launch.

I am also concerned about the accuracy of our parachute testing. Because we were only able to drop the rig from the fourth story of our building, it is possible that the parachute and rig will not hold up as well as it did in the test. The HABL will be going into near-space which is a far cry from a fourth story in a building. There will also be differences in wind strength and pattern that will play a factor in the safety of the descent. Another issue is the payload variance. We had a two pound water bottle inside our rig, but the HABL launch will surely have a higher payload than that.

Another interesting aspect of the HABL launch will be collecting the rig once it has landed. We will not be able to forecast how far the balloon will travel and where exactly it will land. It is possible that the rig will land on private property that we will not be able to access. I suppose we will have to rely on the kindness of our fellow Wisconsinites if this happens.

 

Conclusion:

                This project, though seemingly simple, is extremely complicated. It requires a lot of testing, critical thinking, and pudding around to find the best possible way to solve the issues with the launches. It becomes even more complicated when we bring the many different aspects of the launches together. Luckily we had many hands on board and were able to prepare mostly everything necessary. We have found the designs for our rigs for the most part, tested our parachute and pay loads, worked out a design for the continuous shot mode, and tested our tracking device. The mapping launch seems to have fewer variables than the HABL, but I am confident that both will go well.