The class is going to be a High Altitude Balloon class. The kids are going to be designing a payload that is going to be attached to a 600g helium balloon. The payload is going to be released and the balloon and payload should make 80,000+ feet. At that time, the balloon will pop and the payload will come back to earth via a parachute if all goes well.
The payload will consist of a digital camera, a high altitude tracking device, RTrak-HAB, that will keep track of altitude, longitude, latitude and outside air temp, direction of travel and speed. The camera will be taking pictures every minute of what it sees as it makes it journey into the Stratosphere. This RTRak-HAB will be sending this data back to earth every minute via short wave. The tracking device will be programmed with our contact HAM radio call sign. Students in chase cars will be tracking the payload using the data packets being sent out by a RTrak-HAB device. The packets will be received using a laptop and a VHF radio. Once the payload comes back to earth, the students will be able to retrieve the payload based on the last coordinates sent from the payload. They will then be able to compare the pictures with the altitude packets that were sent back and will be able to see what it looked like from that altitude and what the air temp was at that altitude. The students will also be able to use the data logged to create a 3D google map image of the total flight.
It is a pretty high tech project and there are a lot of variables to make the whole thing work. It is hard to type and explain the whole project. There are many parts to make it work. We are hoping to do this once or twice a year with other kids and we are hoping we can get some science classrooms involved in the future. We can see the science classroom designing some experiments that could be placed in the payload and then the data could be retrieved once the payload touches back on dry ground.
We are a class of 7th and 8th graders at Forestview Middle School in North Central Minnesota. The class consists of 13 students and 4 instructors. The students in the class had to apply to get in into the class. We meet every Wednesday from 3:15-4:30. You can meet the team here.
Here is a link to the prediction software used to predict when to launch. The software will give you a flight path based on the latest weather models. The prediction site will only forecast about 96 hours out. All the known variables are in metric so you must know your metric conversions. Here is the link. http://habhub.org/predict/
This was the easiest part of the project. We needed to figure out what the weight of the payload was going to be and from there decide on the overall size of the balloon. Our payload was going to come in right at about 2 pounds. As a result, we went with a Kaymont 600 gram sounding balloon. We were able to purchase this balloon from Amazon.com for about 60 bucks. We also purchased a 1200g balloon and hope be using them this year to carry a stacked payload.
This is were things got interesting. We ended up using roughly 60-85 cubic feet of helium. We ended up using three quarters of a tank to lift at 3.5 pound payload. The balloon ended up having 1.5 pounds of free lift. This gave us an accent rate of about 1200-1400 feet every 90 seconds.
We used a Canon PowerShot SX230 HS digital camera. The camera was equiped with a 4GB SD card. The 4GB card had room for 1500 pictures. More than enough if taking a pixture every minute. We downloaded the camera hack from http://mighty-hoernsche.de/. The CHDK software allows you to edit the cameras functions. This is important since you want the camera to take a picture every minute. You can find the CHDK software for a variety of cameras. Check to see if the one you want to use is on the list.
After we had the CHDK software on the SD card, we had to place a file named "interval.bas" in the directory named scripts. This scripted allow us to set the time limit at one minute and it also allowed us to turn off the LCD screen so we could save batteries. Thanks to the Led Zeppelin project for this script.
We did find that you had to make the SD card bootable. Since we were on a Macintosh we had to download this little piece of software to help with that process. The software was named SDMInst. We did find that we could not make the software work if the SD card was bigger than 4GB. Also, after you make the card bootable and you place both the script and the CHDK firmware on the card, make sure you lock the card. The camera will still be able to write the images to the card.
Here is the interval.bas script we used.
Here is another great website we used to help answer some of our questions. CHDK Forums. Full of porting threads for Canon cameras.
We used a GoPro Hero. The camera was equiped with a 32GB SD card. We had the camera set up to capture video at 1080i. The camera worked great but did develop some condensation issues at higher altitudes. We need to figure this out. We did see that GoPro does make some moisture wicks you can place in the case to help absorb the condensation. They are called Anti-Fog inserts.
We are using a new device called a HOBO unit made by OnSet. This device has the ability to have various weather sensing equipment attached to it. It has a built in flash drive that captures the equipment readouts. Once the payload is back on Earth, you can attach the HOBO unit to a computer and download the collected data. The data is Excel friendly and can make some neat charts and graphs. We are running a outside temp sensor, an accelerometer and a solar panel.
We attached a 4' parachute which we purchased from Rocketman. These parachutes are available in a variety of sizes. I'm sure he has one that would fit your needs.
The students are working on designing a payload that will be launched into the stratosphere via a helium filled, 600g weather balloon. The payload will be made out of 2 inch pink insulation that will be glued together. The students will then carve out the inside of the payload so they can place a camera, a GPS sending unit and other instruments that will be used to track various weather data.
We are using two devices to help track our payload. The first device we added was a RTrak-HAB - High Altitude APRS Tracker Payload. These devices are made by RPC Electronics. This is the device that will send a packet back to earth containing the payloads altitude, longitude, latitude, outside temp, heading, and speed. These packets will be received by a HAM radio in a chase car.
We also were fortunate to be given a PocketFinder to help track our payload once it returned to Earth. These devices worked great and the best part is that have a cool iPad APP that the kids can use on their smart phones. A super nice back up for our APRS tracking device.
You should familiarize yourself with regs that apply to unmanned balloons. Avoid controlled airspace, and keep your payload under 4 lbs. Disclaimer: We are not an authority on this. You are responsible for anything bad that happens. You must follow all rules and regs if you want to do this. We did.