Balloon, Mark 8 - "Operation Maru"

This mission will use a military surplus ML-541A/AM balloon, further refining our estimate of that envelope's burst diameter and characteristics. It will include a Peach3 tracker and two 808 #16 cameras. One will point to the horizon and the other up toward the balloon. We will add some stabilizing bars to the payload to attempt to improve video quality.

• July 26, 2015. 11:00 AM EST: - Launch

Payload recovered!

The balloon burst early in turbulence, after the payload bounced up and struck it. The moment was captured on video. The stabilizing bars worked nicely to clean up the video.

1. Test the ML-541A/AM balloon, refine estimate of 5.8m burst diameter.
2. Launch with two 808 #16 cameras with (2) L91 batteries shared by both cameras.
3. Find a way to stabilize the payload container for better video.

This is the tracker plus AAA battery weight. Note this was actually from a different launch configuration, but the same idea. For THIS launch, we did not secure the battery to the tracker, and the string was not present.

This is the two cameras (in parallel) together from a pair of AA batteries in series.

This is how the payload looks with both cameras active.

This image is the internals of the payload before we chose to add the second camera. It shows the general placement of the tracker and first camera.

Here is the payload box with stabilizing bars and parachute installed.

Notes:

1. The predictor does not have 1220g balloons, so we used a 1200, added 20g to the payload weight, and specified an explicit burst diameter based on estimations from previous launches.
2. Descent rate based on Launch 7 with a similar payload box.

1. Launch: Hojo/KD2EAT

Using volume of a sphere for 76.3 cu ft

• Volume of a sphere
  • v = 85.3 (per predictor)
  • v = 4/3 pi r**3
• Solving for r, the radius:
  • r = cube root(3v /4pi)
  • r = 2.73 feet
• The circumference of the sphere is pi*d
  • c = pi * 2 * r
  • c = 17.158

We called it 17' 1 7/8“ circumference.

Expected pounds of gas to use:

PSI = volume / .0265 PSI = 85.3 / .0265 PSI = 3218 PSI drop in tank.

Balloon burst early after striking the payload in turbulence.

Given that the payload bounced and hit the payload, it seems the tether was too short. For this launch we had:

Lowest observed temperature was -27.6c on the descent at 9774 meters (32,066 ft).

Temperature at apogee (16,707m = 54,819 ft) was -18.4c.

The upward facing camera failed shortly before landing. I believe it was a thermal problem that we observed in ground testing. It most likely overheated as the payload got to near normal external temperatures. The horizontal camera worked flawlessly through the launch and landing.

Recovery was trivial. It was on the ground beside a driveway. Once getting a beacon from the payload as we drove by it, we were able to drive right to it, and heard the beeper on the payload as we approached.

1. We need a longer string between payload and balloon to avoid the payload striking it.
2. We need to assure there are no pointy bits on the payload, in case it DOES strike the balloon.
3. It was a cloudy day on launch. The video wasn't very interesting until we got above the clouds.
4. We need to work out the thermal problems with the cameras. Perhaps a heat sink will help.