Table of Contents
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
- Test the ML-541A/AM balloon, refine estimate of 5.3m burst diameter.
- Launch with an 808 #16 camera, for better resolution.
- 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:
- 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.
- 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
- Launch: Hojo/KD2EAT and Jule/KD2FOU
- Chase1: Kevin/WB2EMS and Annette
- 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
- 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.
- 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.
- 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.
