Table of Contents

Balloon, Mark 6 - "Operation Tardar Sauce"

Overview

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.

Timeline

Mission Summary

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.

Mission Objectives

  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.

Mission Parameters

Balloon ML-541A/AM military surplus balloon, readily available on ebay
Lifting Gas Helium
Payload Peach1 Tracker, Peach3 Tracker, Micro camera
Payload container Plastic bottle and bubble wrap
Max Payoad Weight 150g
Flight Time 130 min
Cutdown Balloon Burst
Recovery 12“ Parachute
Tracking Peach1 HAB tracker, Peach3 HAB tracker
Telemetry GPS and temperature data.

Balloon and payload Weight Budget

Item Weight (grams)
Tracker1 + Counterpoise 19
Tracker1 Battery - (1) AAA Ultimate Lithium 8
808 Camera 1 19
Camera Battery - (1) 600ma LiPo 16
Payload container 27
Parachute + guyline 17
Peach3 Tracker, antenna, battery, packaging 46
Buzzer + CR2032 Battery 8
Balloon 1400
Balloon attachment (tape) 10
Total (goal: 1550) 1560

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 $30
Peach1 Tracker $150
Peach3 Tracker $150
Packaging, Parachute $10
Total $281

Balloon Prediction Input

Predictor http://predict.habhub.org/
Payload Mass 350g
Balloon Mass 1200g Kaymont
Total Mass 1550g
Target Ascent Rate 4.5 m/s
Descent Rate 8.5 m/s
Gas Helium
Burst Diameter 6.5m
Start Location Lyons, New York

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.

Balloon Prediction Output

Burst Altitude 30157 m
Ascent Rate 4.83 m/s
Neck Lift 1089 g
Launch Volume 78.7 cu ft
Flight Range 84.3 km
Flight Time 131 min

*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.

Chase Cars

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

Launch and Recovery

Balloon fill

Using volume of a sphere for 78.7 cu ft

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.

Launch

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

The Flight

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.

Actual track vs projected track

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.

Predicted Actual
Burst Altitude 30,157m 25,453m
Ascent Rate 4.83 m/s 4.31 m/s
Descent Rate 8.5 m/s 7.07 m/s
Flight Range 84.3 km 49.54 km
Flight Time 131min 157 min

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!

Payload

Temperature

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.

Camera

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.

Recovery

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!

Lessons Learned

  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.