Balloon, Mark 6 - "Operation Tardar Sauce"

This mission will use a military surplus ML-541A/AM balloon, and try to achieve 100,000 ft. It will include a Peach1 tracker as well as a newer model Peach3 tracker, which we will test in harsher conditions outside of the insulated payload package. The trackers will each be beaconing once per minute, 30 seconds apart. We'll again include an 808 Key Fob camera.

• August 7, 2014. 10:00am EST: - Launch

Success!

The balloon burst at approximately 83,000 feet. It was recovered successfully. Unfortunately, the 808 camera did not work. The SD card was faulty, so we did not get in-flight video.

1. Test the ML-541A/AM balloon.
2. Test the Peach1 tracker to 100,000 feet.
3. Test the plastic bottle + bubble wrap packaging to 100,000 feet.
4. Test the Peach3 tracker, in a slightly insulated sleeve, outside the payload bottle.

Notes:

1. The predictor does not have 1400g balloons, so we used a 1200, added 200g from the payload weight, and specified an explicit burst diameter based on estimations from previous launches.
2. Descent rate calculated using Model Rocket Descent Rate Calculator. Total weight 200g. 12” hexagonal parachute. Note, the calculator estimated just under 6 m/s. However, experience shows that the balloon remnants often come down with the payload, speeding the descent. Rounded up to 8.5 m/s based on previous launch experience.

*Note: We're totally guessing on the burst diameter based on data from only two previous flights documented through links on eBay. This will be a learning experience.

1. Launch: Hojo/KD2EAT and Dave/KD2GBX
2. Chase1: Kevin/WB2EMS
3. Chase2: Jon/KC2WAC

Using volume of a sphere for 78.7 cu ft

• Volume of a sphere
  • v = 78.7 (per predictor)
  • v = 4/3 pi r**3
• Solving for r, the radius:
  • r = cube root(3v /4pi)
  • r = 2.66 feet
• The circumference of the sphere is pi*d
  • c = pi * 2 * r
  • c = 16.70

We called it 16' 8 1/2“ circumference.

Expected pounds of gas to use:

PSI = volume / .0265 PSI = 78.7 / .0265 PSI = 2970 PSI drop in tank.

We ended up just emptying a full 80cu ft tank into the balloon. It was just about exactly right.

The 808 camera in the payload did not function. It is suspected that a bad SD card led to the camera crashing moments after being turned on. Unfortunately, the activity lights on this camera both go off when the camera is filming, so it's impossible to tell “filming” from “off”. That's an unfortunate design with these cheap cameras.

This is an overlay of the prediction (Yellow) with the actual (Red). Note the balloon did not go as high, so it did not carry as far west in flight.

This is a map view, with data from both trackers overlayed. Though they were both attached to the balloon, there were minor differences in positions reported, and they beaconed at different times within each minute of flight.

Note, given that the balloon was overfilled at launch to nearly 6' in diameter (113 cu ft), the predictor indicates that the ascent rate should have been about 8.66m/s. This very closely matches our observed ascent rate of 8.57m/s. Let's hear it for science!

We had two temperature sensors on the launch. One tracker was inside the insulated plastic bottle with bubble wrap. The other was in a “cozy”, but otherwise exposed to the elements.

The tracker in the bottle reached a minimum temp of -6c.

The tracker more exposed to the elements reached a minimum temp of -50c.

Both trackers reached minimum temperatures on descent, after the balloon popped.

The 808 camera did not work on this flight. Subsequent testing after launch indicated that the SD card had a format error that was not immediately obvious with short tests. In subsequent launches we should do a full duration test of the camera / SD card prior to launch.

The balloon landed, of course, in a tree just a few feet from the edge of an open field. It was about 40-50 feet up.

After some searching, we found the land owner and got permission to cut the tree down and recover the payload. The land owner even provided the chainsaw!

1. One of the trackers had reboot issues. The software problem was found and resolved after launch. The data proved helpful in finding the issue.
2. Once again, the parachute got totally twisted in the remains of the balloon. For these very light payloads, we will probably fly without a parachute and just depend on the lightness of the payload and wind resistance to return the payload safely.
3. We had some better data as a result of this launch. Based on the data, it appears that the balloon burst at around 5.2m. We will continue to collect data.
4. The plastic bottle seems like a workable technology for keeping the payload warm enough that the camera and tracker function smoothly.