It’s All Coming Back To Me Now

This is the flight of CLOUD3, the main aim being to take photographs and video from “near space”. It was my 3rd such flight – the first of which (CLOUD1) was partially successful, and the second of which (CLOUD2) landed in the sea. As you will see, 1 + 2 = 3 as CLOUD3 combined both of those attributes, becoming probably my most exciting launch yet.

The flight also carried a second, test payload, using a new radio transmitter so we could compare how well that performed with the older one.

Planning

Planning started in December with an application to the CAA for flight permission. The initial planned date was for 29th January, but as that date approached the prediction showed that any launch, regardless of how I adjusted the path with more or less helium, different sized parachute or payload or balloon, would end up ditched in the English Channel. So I postponed the launch for the following weekend. Predictions for the Sunday were poor again, but those for Saturday 4th February were not bad. As the day got closer the prediction changed a little, and I did have to delay the launch by a few hours to have the best chance of landing inland rather than close to or near the sea.

A couple of days prior to the initial launch date I started work on a new tracker using a different radio transmitter to the usual one. This new device has several advantages over the old one but hadn’t been tested in a high altitude flight, so its performance was to some extent an unknown. Compared to the older device it is less than half the price, weighs a lot less (important for very light payloads), can be used for receiving as well as transmitting, and can be programmed to different frequencies (very useful if there are 2 or more flights at the same time). Another feature is that the transmitted power can be programmed. UK flights are limited to 10mW but some of our flights leave UK airspace and may usefully increase the transmitted power to make it easier to track them from a long distance.

With the delay I had time to complete that new tracker and build a small payload for it, meaning I could attach it to the same weather balloon, below the main payload. It increased the weight a little and with the amount of helium I’d purchased that did make the flight a bit marginal on lift, meaning the flight would travel a bit further than otherwise. As we shall see that was another factor in what happened.

Here are the two payloads – Little and Large.


Launch Day

The day’s weather was changeable, with the best launch opportunity being about 1pm.  We had 3 helpers arriving at about 11:30am – Ed and David from the #highaltitude IRC group, and a friend Rhona who also helped on my first launch.  Bacon Butties were served with tea as I checked the latest prediction and showed everyone the payloads to be launched.  We then packed the chase car and drove down the road to the launch site.

Very quickly I realised I’d left a couple of things behind.  It’s a good job my launch site is so close to my home!  This time I managed to leave the balloon …..!

With that minor hiccup resolved, Rhona and I set up about inflating the balloon …

… while Ed and David tied the payload train together.

Just visible on the right side of the large payload there’s a photograph of Julie’s father, Bryan. We shared several interests including photography, computers and space. He died in 2004 from a heart attack, long before I started this hobby.  Bryan’s surname was Cloud, so when I started the hobby I named the payloads after him. For CLOUD3 I decided to put his picture on the outside so he could, in spirit at least, fly along for the ride.

We used up all the helium we had, because the faster the ascent the lower the chance of a wet landing. By then Ed and David had the payload chain ready, so I took the top of that and tied to the balloon neck. At one point whilst putting a final tie-wrap around the doubled-over balloon neck, the balloon slipped from my grasp and flew upwards very quickly. I didn’t panic as I knew the string was tied down (but, worryingly, I can’t now remember what to!). After seeing the balloon stop I looked over at Ed who, having seen balloons lost in this way before, had a wonderful “Oh no not again!” look on his face!

Launch

Once we let the balloon up (deliberately this time) for launch, the wind pulled it over at a sharp angle.

So we definitely needed to move over to the large playing field next to our small preparation patch, and it looked like we would need to do a running launch. After an initial problem with a stuck access gate, we walked over to the far end of the field to launch. In retrospect, if we’d not walked so far then the landing spot might have been a lot better for us (but more on that later)!

I took the main payload whilst my neighbour Richard took the little pink test payload. The plan was for us to run together but looking at the photo below I’m not sure anyone told Richard the complete plan! He has more than a passing resemblance to Tom Hanks, so this looks like a scene from “Catch Me If You Can”!

 

We watched the balloon set off north and then turned around to head south-east, all as predicted.  We were about to set off after packing the chase car, but the engine wouldn’t start!  A combination of an 8-year-old (at least) battery and me leaving the tracking kit running meant there wasn’t enough juice to start the engine.  So we stopped David and Ed in their car before they left.  We tried a push-start but that didn’t work, so we fetched the jump cable from the boot and connected up to David’s car.  Success!  So we left a bit late and I didn’t expect us to be very close to the payload when it eventually landed.

Chase

I sat in the back of the chase car, with a PC doing the tracking (uploading the balloon and car position to a live map).  I also had a netbook for online chat, and Rhona was in the front with the live map running on a tablet whilst Julie did the driving.

 

The prediction was for the payload to land in Sussex, somewhere NE of Ditchling Beacon.  The plan was to get onto the M4 east, then take the M25 south and M23 south towards Brighton, then turn off to wherever the live prediction then said the landing was most likely.  In doing so we allowed the balloon to get further away from us initially as it was heading south whilst we headed east, but then we’d start to catch up as we turned south and hit turned east in the jet stream.  All of this worked out as planned except that the ascent rate was about 5 metres per second instead of the 6 I’d hoped for, so the turning point was further south than planned.  Further south means perilously close to the sea, and the live prediction told us to expect a wet landing.  I had my hopes pinned on the relatively small parachute bringing it down quicker than the prediction said.

Initially I had my receiver tuned in to the CLOUD transmissions, but those were a bit weaker than I expected considering the balloon wasn’t a long distance away.  I believe the antenna was still bent a little when launched, and may have been snagged at launch by the lines going to the test payload.  Next time I’ll cover that with a tube for protection.  Anyway, I switched to the test payload (callsign BUZZ) and got a much better signal there.

The burst prediction was for an altitude of 30km, but the actual burst was at 28km.  The live prediction software then showed a landing point a little way off the coast near Brighton, settling on a point near Shoreham-by-sea.  So we aimed that way in the chase car, and were within a few miles when the payload splashed down.  We lost signal from BUZZ when it was 671 metres up because of the hills and houses in between.

As we got closer I still couldn’t get a signal from BUZZ so I switched back to CLOUD and was delighted to see the familiar 2 lines on the screen meaning that it was still transmitting (something).  As we got within a mile of the beach the signal got much stronger and I started to get decoded telemetry, showing that it was about 500 metres out to sea and still with a good GPS signal.

So we parked up in the street within sight of the beach.  Rhona and I walked down to the shore but couldn’t see the payload bobbing about.  What we did notice though was a nice strong onshore wind, so there was hope that the payload would be blown ashore.  Back in the car, I saw the Ed had posted that it was 15 minutes after low tide, so we had the tide helping us too.  After a short while there was a clear line on the live map showing the payload moving … directly towards us!  So not only did it look like it would come ashore of its own accord, but that we wouldn’t even need to move the car to retrieve it!

The Wait

The rate at which the payload was floating in meant that we had over an hour to wait, so we drove off to get some Fish & Chips.

Recovery

Back to the road near the beach, Rhona and Julie eat their supper but I was still a bit to anxious about the well-being of my two payloads which I was watching getting closer and closer on the screen. After a while I thought they were probably close enough to see. Here’s a screenshot showing the payload and its path down to sea and along towards the beach, with the car in close attendance. The actual flight path was further out to sea and then back on the incoming wind, but we don’t have data for that part of the flight.

At that point the telemetry stopped dead, so Julie and I rushed to the beach to see what had happened. Julie spotted the large payload washed up, with the small payload, parachute and remains of the balloon still attached.

The main payload had tipped over on the beach, allowing sea water to get to the electronics on the inside of the lid. Salt water kills powered electronics very quickly, hence the transmission stopped soon after it beached. The SD memory cards however were dry and working, and I managed to wait till I got home to try them. I then found that the camera had stopped during descent (because I hadn’t cleared the card out before launch so it filled up) and the I’d clumsily stopped the video recorder before launch. So that’s two more things to get right next time.

I didn’t realise at the time, but we were being watched by other enthusiasts and friends who had discovered a local webcam! Here’s an image showing the bright torch I was using to search for the payload:

Photos

The photos show that there were 2 cloud layers. Here’s a photo of our village, including our house, taken on the initial ascent.

And one as the balloon approached the lower layer of cloud:

and a view down to the ground through that layer:

You can also see the upper cloud layer in that one. I also got some nice “sunset” shots through the cloud layers:

And finally, pictures from near 28km, where the only cloud was CLOUD3!

For more photos see my flickr set.

This entry was posted in Uncategorized, Weather Balloon. Bookmark the permalink.

2 Responses to It’s All Coming Back To Me Now

  1. Steven says:

    As a fellow enthusiast here in the States, I think what you are doing is simply amazing. The amount of work you do as a hobbyist seems incredible. I work on weather balloon payload systems for Auburn University and have recently been trying to put together a live predictor for our team (need to put that aerospace degree to good use). I noticed you are using a live predictor as well and was wondering which one you are using. Is there anything you really like or dislike about it? Any suggestions on how to make it better? This is a new endeavor of mine so I’m curious what I can do upfront to make things easier. Also, if you have any data dumps of GPS that you are willing to share, I’m always looking to validate my code. Wish you the best of luck in any upcoming launches!

    • David Akerman says:

      I use the prediction software written by CUSF (Cambridge University SpaceFlight group). I run it before the flight so I know roughly where the payload will land, so I can decide whether to postpone or not, and whether to adjust the flight or not. During the flight the predictor updates a live prediction from the balloon position and flight parameters (i.e. expected burst altitude).

      I believe the code for the predictor is public domain. Your best bet if you want to know more about it is to ask on the #highaltitude IRC channel. There’s usually someone on there who can answer questions or at least point you in the right direction.

      For GPS testing I just wrote a program that generated a complete flight of NMEA strings. Here in the UK the key test is to make sure it all works when flights cross the prime meridian. My flights typically start west of that and end up east, so it’s important the code handles the transition! For the USA you won’t have that problem (unless you go for a transatlantic flight, which has been done!) but you will need to make sure the code is OK for other meridians and also circles of latitude.

Leave a Reply

Your email address will not be published.