Since the launch and unsuccessful recovery of Ozhab1, I’ve always planned to reattempt another launch. However time and more important tasks seem to get in the way. However 2018 brings on many new challenges., so why not throw the construction of Ozhab2 into the mix. Though I still hope Ozhab1 will be found (slim chance), I’ve certainly learnt a lot and had a lot of fun building, launching and tracking it.
Construction of Ozhab2 has now commenced with the 2m – VHF APRS module arriving a week ago. The module is the same Radiometrix HX-1 used in my previous launch and I was very happy with it.
For Ozhab2, I’m not trying to reinvent the wheel, so will base my tracker off the Trackunio project code for Arduino. I won’t be using the Trackunio Shield as that wouldn’t be as much fun,
APRS looks to be transmitting already, but I haven’t tested a decode yet. A little more to go yet.
Decided to use a Styrofoam Esky (Cooler, some people may call it) to house my payload. The small Esky usually stores up to 6 cans of soft drink so its not overly large. Its also very easy to cut through to make holes for the camera gear. I still need to work on the final attachment to the parachute as the esky comes pre-fitted with a rope tied lid. I will most likely replace the provided rope with my own and add an additional two points to provide more stability during the flight.
I started by cutting a hole for the Go Pro which will hopefully record a video of the flight. The other small hole is for what I think is the light sensor. I will need to make a few more adjustments to get the hole size right, as the Go Pro has a wide angles lens and I can still see the Esky in the shots.
I have also cut another hole in the bottom of the Esky to allow for a second camera. The 2nd camera is my cheap 1080P camera and will be set to take a still shot over 5 secs.
I am hoping that if I connect the cameras to an external battery that I will be able to extend the battery life. This seemed to work in my initial tests, but I am currently retesting to ensure I can get at least 3 hours of battery life.
I don’t really want to purchase a Go Pro Back pack battery if I don’t need to.
I will be placing some additional foam around the cameras to keep them in place, but have discovered that having the USB cables attached make it more difficult to get the foam to fit. More cutting and adjustment needed.
The camera’s seem to be locked in tight and I can shake the payload and they don’t budge.
The Go Pro looks good to go (except for battery life), its more a power-on and hit record, whilst my other camera seems to revert to some basic setup when I turn it on , so I have to reset everything to how I need it for the flight. During a recent test, I thought I was recording a still every 5 secs but instead it was videoing, it wouldn’t have been too bad provided the battery life lasted. So I’ll be researching to see if I can save the config somehow to save time and fiddling at launch.
One of the problems I am going to face when it comes to launch time, is exactly how much helium do I need to get the required lift. To much and the balloon will burst early and not reach a high altitude. Not enough and the balloon could just float aimlessly without ever bursting, and very likely land in the ocean.
You can use various calculators around the internet to get a rough idea, such as the habitat burst calculator. You enter the type of balloon and the altitude your attempting to reach and it will provide a ‘Neck Lift’. This is the weight the balloon should be able to left in order to take the payload to the aimed altitude.
When filling the balloon with helium you need to check how much force it is lifting, by either using some luggage scales , or attaching a weight such as a water filled bottle that is at the predetermined weight.
I purchased a small digital scale to assist with filling helium into the balloon.
I chose this particular model as it has a fairly secure handle that I could attach a rope into. Other models had a hand grip which would have been harder to tie down. I just need to be careful of the hook to ensure it doesn’t penetrate the balloon cutting my mission short.
I most probably will have some pre-filled bottles that are at the required weight as a backup, as its the first launch I don’t know how accurate the scale reading will be.