Friday, 11 January 2013

Flight pictures

Project summary
An 800g weather balloon sent to just over 29km with 2 cameras, 2 GSM GPS's and 1 radio communication box. Tracking thoughout the whole flight and chase cars for retrieval of the packages. The navy "home guard" were on standby in case of a sea landing.  In the pictures below you can see the story in reverse order. We start with the payload about to land near the E20 motorway - the chase cars were waiting about 200m from the predicted landing site after a 120km flight.

Thanks to the UK High Altitude Society for the use of their software and their advice during the flight.

Here is a 15 min video summary of the flight.

You can see more of the project on Aars Avis....

Overview of the flight communicatiuons

The parachute, camera box and radio box just before landing and see from the lead chase car

The balloon bursting

The radio box flying about in the 150km/h descend.

Tuesday, 8 January 2013

Launch day

The balloon will be sent up at 11am on Friday 11th January. It will be sent from the grounds of Skals Efterskole. It will land at about 13.00 near Esbjerg.

Here is the video from the landing site / chase car (live from approx 13.15)

Tuesday, 1 January 2013

Can a balloon travel to space?

No, it cannot!

Balloons rise because if Archimedes' principle. The upward force is equal to the weight force of the amount of gas that is displaced. Air at ground level has a density of about 1kg per cubic meter. So a 1 cubic meter balloon has an upthrust of 10N (1kg force as some people call it).

The downward force is the weight of the balloon, the helium, string, payload, etc. Maybe that is 0.7kg or 7N.

So our total upward force for a 1 cubic meter balloon is 10-7=3N

As the balloon rises the atmospheric pressure decreases and the balloon gets bigger. It starts off maybe 1m diameter but at 30km it may be 6m diameter (the volume 200 times greater than when it started). It expanded 200 times because the atmosphere is 200 times less dense. Because the balloon rubber is very thin it does not compress the helium very much. Because of this the Archimedes calculation we did at gound level works all the way up - the balloons rises at about the same rate all the way.

But back now to the original question - can a balloon go to space? No it can't. To have buoyancy the ballon needs air to displace. The altitude limit depnds on how flexible the balloon rubber is - more stretchy means more height, but only if there is still some air!

Sunday, 30 December 2012

Launch weather. Vejret når vi opsende ballonen.

Updated 4th January. High pressure is forecast for next week. Easterly winds are often cloud free.

The high level winds, the winds that carry the balloon the greatest distance, are in the right direction but maybe start to turn towards to the east at the weekend.

If we miss the launch next week we hope the high pressure will stay with us over the weekend and into the week starting 14th January.

Watch this space!

Saturday, 29 December 2012

Real time data. Radio tracking

Below the main payload (where the cameras are) there will be a radio transmitter, gps and a flight computer (an Arduino) This box will transmit gps data and will enable us to monitor the balloon's position thoughout the flight.

Under den hoved pakke (hvor kameraet er) der vil være en radio sender, gps og computer (Arduino). Denne kasse vil sende gps data og mener vi kan følge ballonen gennem hele fljvningen. 

Wednesday, 26 December 2012

GoPro Hero2 lens fogging

It turns out that keeping the inside of the case, particularly where the lens is, clear of ice is not so simple. Earlier in this article I put the camera in the freezer to test "anti-fog" inserts, which are probably silica gel things that absorb water vapour from the air. They appear to work.

The problem is though that at low pressures these anti fog inserts give up all their moisture, maybe even moisture they had before they were put into the camera. So they end up being a SOURCE of vapour!

Here is the HD camera after nearly 3 hours in the freezer at -20C. On the flight it will spend about 2 hours below -20 and some of the time down to -70C. Think about it though - the air is 1/12 of the density up at 30km so does it matter so much? Is the -20C freezer test too harsh?

It is now 3 days later and I have obtained some of the incredibly expensive anti fog inserts. I slid 3 into the case under the same conditions as 3 days ago and put the camera in the freezer. This time there was no fog. So they work.

To be absolutely sure that the video is fog free the air (with the moisture) will be replaced on launch day with another gas - helium or carbon dioxide.

Tuesday, 25 December 2012

Camera, parachute and balloon

Below you can see the start of the main payload.

Duct tape and polystyrene! It has to be light and it has to float.
There will be two cameras. One will point horizontally and the other will point vertically downwards. Pictured here are the cameras, the balloon (in the bag at the back) and the parachute.

Der vil være to kameraer. En vil pege horisontalt og anden vil pege ned til jorden. Denne billede her viser kameraerne, ballonen (i posen) og faldskærmen.

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