Balloon, Mark 7 - "Operation Colonel Meow"

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 an 808 #16 camera, which should provide better resolution than the previous launch. We will add some fins to the payload container, hoping to stabilize it in flight for better camera imagery.

Timeline

  • April 18, 2015. 01:00 PM EST: - Launch

Mission Summary

Recovered!!

The tracker had an undetected issue with the Low Pass Filter on the antenna. We lost contact with the balloon at 5,000 feet. The flight flew to completion and appears to have exceeded our altitude predictions. The payload landed in a field in Freeville, NY, about 12 miles past the anticipated landing area and was returned to us by the farm owner there, 11 days later.

Mission Objectives

  1. Test the ML-541A/AM balloon, refine estimate of 5.3m burst diameter.
  2. Launch with an 808 #16 camera, for better resolution.
  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
Max Payoad Weight 150g
Flight Time Under 180 min
Cutdown Balloon Burst
Recovery Payload free fall
Tracking Peach3 HAB tracker
Telemetry GPS and temperature data.

Balloon and payload Weight Budget

Item Weight (grams)
Tracker + Counterpoise 19
Tracker Battery - (1) L92 AAA Ultimate Lithium 8
#16 808 Camera w/SanDisk 16G SDHC I, Class 4 19
Camera Battery - (2) L92 AAA Ultimate Lithium 16
Payload container 30
Guylines 6
Balloon 1250
Balloon attachment (Final string and tape) 12
Total (goal: 1550) 1360

Final Package

Budget

Item Estimated Cost
ML-541A/AM military surplus balloon $40
Helium or Hydrogen (80 cu ft cylinder) $66
Mini camera & SD card $58
Peach3 Tracker $60
Packaging $10
Total $234

Balloon Prediction Input

Predictor http://predict.habhub.org/
Payload Mass 160g
Balloon Mass 1200g Kaymont
Total Mass 1360g
Target Ascent Rate 4.8 m/s
Descent Rate 10.0 m/s
Gas Helium
Burst Diameter 5.3m
Start Location Holley, New York

Notes:

  1. The predictor does not have 1250g balloons, so we used a 1200, added 50g from the payload weight, and specified an explicit burst diameter based on estimations from previous launches.
  2. Descent rate based on Olean launch with a similar payload box. Their payload broke completely free of the balloon and fell at 12.1 m/s. Our previous bottle launch fell at 7.2 m/s. Estimate 10.0 m/s, assuming that some of the balloon will remain after burst and provide wind resistance.

Balloon Prediction Output

Burst Altitude 25,952m
Ascent Rate 5.26 m/s
Neck Lift 1018 g
Launch Volume 76.3 cu ft
Flight Range 139.1 km
Flight Time 104 min

Chase Cars

  1. Launch: Hojo/KD2EAT and Jule/KD2FOU
  2. Chase1: Kevin/WB2EMS and Annette
  3. Chase2: Jon/KC2WAC and Tayyar

Launch and Recovery

Balloon fill

Using volume of a sphere for 76.3 cu ft

  • Volume of a sphere
    • v = 76.3 (per predictor)
    • v = 4/3 pi r**3
  • Solving for r, the radius:
    • r = cube root(3v /4pi)
    • r = 2.63 feet
  • The circumference of the sphere is pi*d
    • c = pi * 2 * r
    • c = 16.53

We called it 16' 6 3/8“ circumference.

Expected pounds of gas to use:

PSI = volume / .0265 PSI = 76.3 / .0265 PSI = 2879 PSI drop in tank.

Launch

The Flight

Actual track vs projected track

Predicted Actual Revised prediction
Burst Altitude 25,952m 27,909m (est) 27,910
Ascent Rate 5.26 m/s 5.26 m/s (assumed) 5.26
Time to burst 01:22:00 01:27:12 01:28:00
Descent Rate 10 m/s 9.34 m/s 9.34 m/s
Time to descend (predictor) 00:22:00 00:49:47 00:24:00
Time to descend (actual) 00:43:15 00:49:47 00:49:48
Flight Range 139.1 km 163.88 km unknown
Flight Time 02:05:15 02:16:59 02:17:48

Third column represents a revised prediction assuming 5.8m burst diameter (vs 5.3 assumed prior to launch). This seemed to match the flight times and landing location pretty well.

Payload

The payload was secured to the balloon via strings piercing the foam box and looping underneath. At burst, the strings on one side of the payload box tore right through the foam, ripping the end off the box.

In future missions, we should use some kind of reinforcement along with the string to protect the foam box.

The foam box as made somewhat wider than necessary to try and reduce the spinning of the payload. This worked well. Adding longer bars sticking out the sides might add further stabilization.

Temperature

No data available.

Camera

The camera worked flawlessly, capturing the entirety of the flight. Total battery life with two AAA L92 ultimate lithiums was 02:55:35.

Recovery

Landed in a field. Recovered by a farmer who contacted us based on the name tag on the payload.

Lessons Learned

  1. The output power of the tracker should be tested prior to launch to assume it works at range. This has been added to our tracker build checklist.
  2. The payload container should be reinforced where the strings attach so that they do not tear the payload box open. One of the Olean launches had a similar issue.
  3. A longer payload box stabilized the imagery quite a bit. For the next launch, we should try some long but light bars sticking out the side, increasing the moment of inertia.
Last modified:: 2015/07/18 08:30