Table of Contents

Balloon, Mark 8 - "Operation Maru"

Overview

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.

Timeline

Mission Summary

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.

Mission Objectives

  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.

Mission Parameters

Balloon ML-541A/AM military surplus balloon, readily available on ebay
Lifting Gas Helium
Payload Peach3 Tracker, 808 #16 Micro camera
Payload container Foam box with stabilizing bars extending from it.
Max Payoad Weight 200g
Flight Time Under 180 min
Cutdown Balloon Burst
Recovery Small drogue chute
Tracking Peach3 HAB tracker
Telemetry GPS and temperature data.

Balloon and payload Weight Budget

Item Weight (grams)
Tracker + Counterpoise 12
Tracker Battery - (1) L92 AAA Ultimate Lithium 9
#16 808 Camera w/SanDisk 16G SDHC I, Class 4 10
#16 808 Camera w/SanDisk 16G SDHC I, Class 10 10
Camera Battery - (2) L9 AAA Ultimate Lithium 33
Payload container 105
Guylines + Chute 14
Beeper + Battery 8
Balloon 1,220
Balloon attachment (Final string and tape) 40
Total (goal: 1400) 1461

Final Package

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.

Budget

Recoverable

Item Estimated Cost
(2) Mini camera & SD card $100
Peach3 Tracker $60
Packaging $10
Total $170

Consumables

Item Estimated Cost
ML-541A/AM military surplus balloon $40
Helium (80 cu ft cylinder) $71
Total $111

Balloon Prediction Input

Predictor http://predict.habhub.org/
Payload Mass 261g
Balloon Mass 1200g Kaymont
Total Mass 1461g
Target Ascent Rate 5.0 m/s
Descent Rate 9.8 m/s
Gas Helium
Burst Diameter 5.8m
Start Location Seneca Castle, New York

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.

Balloon Prediction Output

Burst Altitude 27,103m
Ascent Rate 5.52 m/s
Neck Lift 1280 g
Launch Volume 85.3 cu ft
Flight Range 65.2 km
Time to burst 82 min
Flight Time 102 min

Chase Cars

  1. Launch: Hojo/KD2EAT

Launch and Recovery

Balloon fill

Using volume of a sphere for 76.3 cu ft

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.

Launch

The Flight

Actual track vs projected track

Predicted Actual
Burst Altitude 27,103m 16,707
Ascent Rate 5.52 m/s 4.9 m/s
Time to burst 01:22:00 00:57:00
Descent Rate 9.8 m/s 9.3 m/s
Time to descend (predictor) 00:20:00 00:29:54
Time to descend (altitude / descent rate) 00:50:11 00:29:54
Flight Range 65.2 km 85.7 km
Flight Time 01:42:00 01:27:04

Balloon burst early after striking the payload in turbulence.

Payload

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

Balloon to chute top 7' 10”
Chute top to chute gather 1' 10“
Chute gather to payload gather 3' 8”
Total: 13' 4“

Temperature

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.

Camera

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

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.

Lessons Learned

  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.