UKHAS Wiki

UK High Altitude Society

User Tools

Site Tools


projects:jimbob:launch1

Launch 1

This page tracks Launch 1.

Bill of Materials

Tracker

Power

Energizer Ultimate Lithium AA and AAA's - purchased

$$BOB - Going to use 3 x AAA's for my first flight. $$PROM - 1 x AA Camera - 2 x AA Video Camera - 2 x AA

Photos Camera

Canon Power Shot A810

DP Review - Purchased

  • 28mm wide angle (wider than most)
  • 2 x AA Batteries
  • 171g inc Batteries, before weight reduction program :)
Canon CHDK

The Cannon Cameras can be controlled by a firmware extension called CHDK

The FAQ entry here to get the firmware version wouldn't work for me, so I took a picture and downloaded a program to extract it from the exif info (1.00D).

I then downloaded http://mighty-hoernsche.de/bins/a810-100d-1.1.0-2201-full_ALPHA.zip from http://mighty-hoernsche.de/ and installed it on a Bootable SD card using the method described here.

Finally I downloaded the example script for HAB use from here: http://blog.jgc.org/2010/09/gaga-1-2766-tedious-photographs-and-log.html. The script required several changes, some of the CHDK settings don't work, or work differently on the A810, and I added a line to turn the display back-light off to save power (no external AV socket control of back-light on the A810). The script is in my GitHub Repo with the tracker code.

SD Card

Each picture takes aprox 4Mb. With a 4Gb SD card that is ~1,000 pictures. A flight of up to 4 hours gives around 4 pictures a minute, or 15 seconds between pictures. With a 8Gb SD Card that is ~2,000 pictures. A flight of up to 4 hours gives around 8 pictures a minute, or 7 seconds between pictures.

Freezer Test

The script was told to delay 10 seconds between pictures, on a fresh set of Energizer L91 AA's and with an empty 8Gb SD card and then placed in the freezer, with a torch so that he camera was not struggling to focus in the dark.

The camera was removed over 7 hours later, and was still taking pictures. It took an average of 3 pictures per minute, starting at 13 to 15 seconds between pictures, ending at 25 to 27 seconds between pictures. The underlying additional delay (3 to 5 seconds) is due to an added delay from the backlight turn off code, and the time it takes to actually take a picture. The growing delay over time I can only guess - reducing battery voltage, reducing light from the torch, freezing over of the lens (so it took time to decide it couldn't focus)?

It took 1,256 pictures in total, using 2.5Gb of space, leaving 4.8Gb remaining. The batteries started at 3107mv and ended at 2174mv. The rate of reduction in voltage was growing in the log, showing that the batteries were nearing the end of their life at that temperature.

Video Camera

Mini DVR 808 #16 V2 -Lens D Car Key Chain Micro Camera - Purchased

16Bb Micro SD Card - Purchased

At 7Mbps with sound recording on, the camera used 1.95GB to record 35 mins of video before the battery was flat.

  • 3.5v x 0.2a = 0.7w/35 mins = 1.2w/hours power consumption
  • 1.4v x 2.0a = 2.8w * 2 cells = 5.6w/hours available from 2 x AA's
  • 5.6w / 1.2w = 4.6hours + the in built 35mins = 5 hours run time.
  • 1.95Gb / 35mins * 60mins = 3.35Gb per hour
  • 16Gb / 3.35Gb per hour = 4.7 hours recording space

I used the NR16 utility to upgrade the firmware to MOV 0.41, set the camera time, turn audio recording off and increase the data rate to 10Mbps.

I have purchase an external AA battery pack to provide the power required for a 3 to 4 hour flight.

Balloon

Looking at using a 500g balloon, requiring 1.29 cu m of Helium. Purchased from Random Engineering.

Detailed data is here: balloon_data

Enclosure

Poly Balls purchased (1 x hollow, 1 x solid) but they were not a good fit together and difficult to work with, so I went with a square poly box that I built up in layers.

Helium

2 options I am considering:

Cylinder Valve

Normal balloon filling valves are not ideal for our use but I have one cheap from ebay which I can use. Looking for one that has a tap and can have a pipe attached.

Balloon Filling Device

Made a hose pipe attached to a waste pipe type fitting, ie: fill_tube

Parachute

Sizing chart here - parachute_sizing_chart

The balloon_data 'keep it simple' table suggests 18โ€œ or 24โ€.

The drag formula reconed about 30โ€œ

One option for Chutes is here: http://www.randomengineering.co.uk/Random_Aerospace/Parachutes.html, I went direct to https://spherachutes.storesecured.com/.

Cord

http://www.randomengineering.co.uk/Random_Aerospace/Stuff.html - purchased

1.0mm Braided Nylon Cord - Breaking Strain 22.5Kg (220N) - weight approx. 0.6g per meter 22.5Kg is under the ICAO 230N (50lb) separation force limit Supplied in 18m lengths on card.

NOTAM

Applied for the NOTAM using the form here caa_notams

Weight

Total weight of the payload:

Primary payload - 500g all in (trying to reduce!)

Secondary payload - 60g all in

String & Parachute - 40g

Free Lift

500g Balloon, 600g payload all in, needs a neck lift of 1.23kg to achieve an ascent rate of 4.9m/s, which will give a burst altitude of 26,488 Meters, after 90 mins. It will need 1.7m3 of Helium.

My filling adapter, with 40cm of hose, weighs 0.35kg, therefore my additional neck weight to judge free lift for launch needs to be 1.23kg - 0.35kg = 0.88kg

I have 3.6m3 of helium in total, with a starting pressure of 3,000 PSI.

Launch Announcement

Launching from a site near Market Harborough (Leicestershire), NOTAM is in place.

Primary tracker: NTX based, $$BOB, 434.075Mhz, USB, RTTY, 600Hz Shift, ASCII-7, 50 Baud, Parity none, 2 Stop bits.

$$BOB, id, time, lat, lon, alt, sats, vinmv, temp_internal, temp_external.

Secondary Tracker: RFM22 based $$PROM, 434.175Mhz, USB, RTTY, 480Hz Shift, ASCII-7, 50 Baud, Parity none, 2 Stop bits.

$$PROM, id, time, lat, lon, alt, sats, vinmv, rfm_temp

Documentation is here: http://ukhas.org.uk/projects:jimbob

Burst predictors are linked from here: http://ukhas.org.uk/guides:balloon_data

Flight Path predictor is here: http://habhub.org/predict/ or an alternative here: http://weather.uwyo.edu/polar/balloon_traj.html

The Launch

And it overshot, less than 2 miles out to sea, after a journey of 140 miles, achieving an altitude of 29,611 meters, 97,148 feet :(

Outside air temperature went down to -42 deg C at 30,000 feet, but was back up to a relatively warm -26 C at the peak of 97,000 feet.

Achieved a peak speed in the air of 152km / hour whilst at 30,000 feet

http://www.facebook.com/photo.php?v=10151161387118660

http://www.facebook.com/media/set/?set=a.10151161412613660.442941.632433659&type=3

projects/jimbob/launch1.txt ยท Last modified: 2012/12/25 20:31 by kevwal