Balloon, Mark 5 - "Operation Lil' Bub"

Overview

This balloon will use our new and improved “Peach1” tracker board and a small USB Key Fob camera.

Timeline

  • August 2, 2014. 10:30am EST: - Launch

Mission Summary

Success!

The balloon was launched on schedule with the tracker and camera operating. Though the tracker experienced a few reboots during flight, we were able to track the payload to the landing spot and retrieve it.

Mission Objectives

  1. Use our new Peach1 tracker board.
  2. Move the USB Key fob camera inside the pay load container to avoid thermal concerns.

Mission Parameters

Balloon Latex 150g
Lifting Gas Helium
Payload Tracker, Micro camera
Payload container Plastic bottle and bubble wrap
Max Payoad Weight 150g
Flight Time 45-90 min
Cutdown Balloon Burst
Recovery 12“ Parachute
Tracking Peach1 HAB tracker
Telemetry GPS and temperature data.

Balloon and payload Weight Budget

Item Weight (grams)
Batteries - (1) 300ma LiPo 9
Batteries - (1) AAA Ultimate Lithium 8
Payload container 25
Tracker + Counterpoise 19
Parachute + guyline 17
Balloon 150
Balloon attachment (tape) 10
Camera 1 19
Total (goal: 300) 257

Final Package

Budget

Item Estimated Cost
Latex Weather Balloon (150g) $25
Helium or Hydrogen (80 cu ft cylinder) $66
Mini camera & SD card $30
APRS Tracker $150
Packaging, Parachute $10
Total $281

Balloon Prediction Input

Predictor http://predict.habhub.org/
Payload Mass 100g
Balloon Mass 200g Kaymont
Total Mass 300g
Target Ascent Rate 6.0 m/s
Descent Rate 8.0 m/s
Gas Helium
Burst Diameter 2.4m
Start Location Trumansburg Fairgrounds, New York

Notes:

  1. The predictor does not have 150g balloons, so we used a 200, deducted 50g from the payload weight, and specified an explicit burst diameter based on manufacturer specs.
  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 m/s based on previous launch experience.

Balloon Prediction Output

Burst Altitude 10464 m
Ascent Rate 7.52 m/s
Neck Lift 1550 g
Launch Volume 60.2 cu ft
Flight Range 26.2 km
Flight Time 40 min

*Note: The balloon manufacturer claims 15,000m burst altitude. We are filling this balloon a LOT.

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 60.2 cu ft

  • Volume of a sphere
    • v = 60.2 (per predictor)
    • v = 4/3 pi r**3
  • Solving for r, the radius:
    • r = cube root(3v /4pi)
    • r = 2.43 feet
  • The circumference of the sphere is pi*d
    • c = pi * 2 * r
    • c = 15.27

We called it 15' 3“ circumference.

Expected pounds of gas to use:

PSI = volume / .0265 PSI = 60.2 / .0265 PSI = 2272 PSI drop in tank.

Launch

At the time of the fill, we put in more gas. The tanks were nearly empty, and we wanted a short flight, so we put in a fair bit more gas. The balloon diameter should have been about 4'8”. I'm 5'11“ and the balloon looked about as tall as me in this shot. Assuming a 6' diameter, we filled the balloon with about 113 cu ft of helium. It didn't seem to make the flight shorter, however. The balloon burst much higher than predicted.

The Flight

Watch it here:

Actual track vs projected track

Predicted Actual
Burst Altitude 10,464m 13,500m
Ascent Rate 7.52 m/s 8.57 m/s
Descent Rate 8.0 m/s 8.91 m/s
Flight Range 26.2 km 49.54 km
Flight Time 40 min 49 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

The payload temperature dropped to about -4c during the peak of the flight. This did not interfere with the tracker, though the battery voltage did drop considerably due to the temperature (from 1.64v to 1.38v). It rebounded as the temps came back up.

Camera

The 808 camera performed very well. Prior to flight, it was measured at using about 110ma while recording. We used a 300mah LiPo battery for the flight, and we had over 2 hours of video on the camera when retrieved. Each 10 minute block of video used approximately a gigabyte of space. The 16G SD card had just over 12G of footage on it.

Recovery

The balloon landed on the roof of a duplex. We fished it off with a few antenna whips duct taped onto an extensible pole saw.

Lessons Learned

  1. The tracker had some issues with reboots. They need to be resolved prior to the next flight.
  2. The 150g balloons apparently have quite a bit of variability in burst altitude! That was a surprise.
  3. Although the parachute predictor estimated a descent rate of about 6 m/s, we rounded up to 8 based on previous experience with the balloon remains interfering with the parachute function. The observed descent rate was 8.9 m/s. We could have rounded even higher.
    1. In future, we might want to use a larger chute than recommended to temper the descent rate, or find a means to jettison the balloon remains after burst.
Last modified:: 2014/08/09 08:38