Requirements for a successful balloon mission
The ultimate use of the XK07 kit is to fly the kit attached to am untethered balloon.
This second part of Phase 1 involves moving your experiments away from the school and also launching the WeatherSats with large party balloons. These launches are designed to attain an altitude of 5km or 16,000ft to ensure no interference with air traffic. To ensure that we can collect our data during the balloon mission, we need a radio with the satellite to send the data and a Ground Station to retrieve the data. The GPS will give us data about our position as we move about, and we can begin tracking how weather conditions change as we move about our town and county.
Plan your flight
Once you are ready to decide for a day to fly your balloon, make the necessary research to figure out which exact day is launch day.
- Get the long lead items (more about each item later):
- Other antennas
- Check the weather. Rain, or any precipitation, is definitely not recommended:
- It ways down the balloon and payload and therefore could require more helium or even a bigger balloon.
- It could cover some of the sensor and give misleading readings.
- It could prematurely destroy some of the xChips - electronics and water just don't go well together.
- Next up is to identify the flight path. Cambridge University Spaceflight has developed a High Altitude Balloon (HAB) flight path prediction tool you can use for that.
- Use this tool to estimate the flight path and - more importantly - the expected landing zone.
- The tool requires an accent and decent rate and a balloon burst altitude. An accent rate of 5 m/s is a good start. And a decent rate is based on choice of parachute, more about that later.
- The burst altitude is more tricky. The best option is to run the simulation with various altitude, say 5,6,7,8,9,10,11,12 km. We find that the balloon always fly higher than anticipated, simply because filling the helium into a large balloon is a scary exercise, and one tent to stop too early. That will result in the balloon having a lower accent rate, but a higher burst altitude. Read more here: HAB burst altitude. You can also use one of these two calculators (they are meant for HAB (high altitude balloon mission - 100000ft+/30000m+)):
- Remember to save your different simulation and also save the .KML file for later. The tool will not work back in time, so you can't later compare your actual flight with your predicted flight if you don't save the prediction, both by taking a screenshot, but also download the KML file, which opens directly in Google Earth.
- You are now ready to set a date for your flight. Because of weather prediction, too far into the future can make it more uncertain, but make sure you have enough time to ready your mission. It is advisable to simulate a flight first by flying the kit tethered to a balloon. That give you a better idea about what to expect on the day. It also allows you to gather some data that you can work on both from the SD-Card and the downlinked data on the dashboard.
- Expect to work with this over several days. Even though the xChips is easily assembled and the hardware equation is taken out of the picture, the rest of the preparation is still a considerably task.
Preparing the XK07 kit
Getting Started XK07 will take you through all the preparation of the kit: the assembly, the flashing, the configuration of the kit. Here is a couple of important pointers:
- You can have a satellite either with CW01 core OR with a CS11 core. We recommend the CS11 core with a SD Card.
- If you choose the CS11, get a SD Card not exceeding 32 Gb, which is formatted to FAT32. Don't worry - all SD Card are formatted like that out of the box, this is only important if you are reusing a SD card from another project.
- Once the SD card is inserted into the CS11 and assembled with the rest of the kit, you can test the circuit by attaching a OD01 (OLED display) temporarily to the satellite. You will get an error message on the OD01, if the SD card is not properly formatted.
- Make sure you have loaded the SD card with the 2 files described in Getting Started XK07, the .bin and the .txt file.
- While you are testing your satellite, you don't need to use the PB04 with batteries. You can simply attach an IP01 or another power xChip - just keep the PB04 turned off, no reason to remove it. That allows you to do long term testing and data gathering, without battery change interruption.
- As mentioned earlier, prior to your flight, you can attach an OD01 to see other status messages. Even on flight day, it is alright to have a OD01 inserted into the kit and remove it just before letting go of the balloon. No need to power cycle - just unplug.
- Once the kit has started and if correctly configured, it is now looking for GPS data. The attached SN01/GNSS (the GPS) only uses GPS data, not GLONASS/BEIDOU/GALILEO. The SN01 have no battery, so at each power cycle the GPS Almanac is lost. That means the GPS has to regain position from scratch, which takes longer time than for example the GPS on your smartphone. It also needs more open sky. You can use a tool like this GPS view or any of the many similar iOS or Android tools, to view the sky overhead. You could be in a situation where fewer than normal GPS satellites are operational, that will require you to move to another open area just until you get the initial position. You can see the status of the GPS on the OD01.
- Once SN01/GPS data is ready, you are ready to fly - or initially, just to receive data, so you know what to expect.
Preparing the rest
- Helium: There is a big difference between the party helium you get in the pink or baby blue cylinders at Target/Walmart/etc. and the science or medical grade helium you get in large K cylinders. The party helium is not pure, it contains nitrogen and air as well, giving it less of a lift in comparison to pure helium. The burst altitude is also lower. Here is more about Helium.
- If you get a high pressure cylinder, you also need a regulator. The smaller pink/baby blue cylinders are low pressure and you can fill directly from the cylinder.
- Balloon: You need to lift around 100 grams/3.5 ounces in payload. To that you need to add the balloon and the parachute. Typically a 24" or even better a 36" balloon is perfect for such a balloon mission, no need to go for a high altitude balloon. You used to be able to get them in party stores, but craft stores are more likely to carry them. Take a look at the above mentioned balloon calculators.
- Parachute: The best place to find parachutes is places that sells hoppy rockets. You should aim at land at 3 m/s or less. Assuming a payload, parachute and remaining balloon after burst all weighs around 200g or less, you need around 75cm in diameter parachute. You can do the exact calculation here (remember to put your calculated decent rate into the above flight path prediction simulator):
- Antennas: Antenna Calculator
- Batteries: Lot of AA batteries will operate fine with the kit - at normal temperature. But if your balloon reaches high enough, your circuit will feel the cold and easily hit -50ºC (-58ºF). The best type of batteries for such low temperature is lithium (not rechargeable lithium-ion batteries), these are non-rechargeable. More here from one supplier Energizer.
- Fishline: This is to tether the balloon to your kit. Weave the fishline through the various holes in your kit, to give it an extra chance of sticking together as it flies.
- Cable ties: Cable ties are the easiest way to close the balloon once filled with helium. Tie the tether to the cable tie before filling the balloon. Also use the cable tie to secure the batteries to the battery holder. Alternatively some duct tape will do.
- Tools: You are probably not launching from your work place, so bring a pair of scissors and other tools your helium tank might need.
Make sure you comply with the local regulations of your country/state.