Re: [UKHAS] BABSHAB launch - Great Tew, Saturday 25th May-Monday 27th (exact date to be confirmed next week pending forecasts)

[Steve Aerospace]

Wow - the apogee GoPro shot is really impressive.  

Here are a few comments from me.

I don't think you can draw any under fill conclusions from a 32.6km predicted vs 33.5km burst altitude - thats easily within the range of normal burst distribution - particularly for non Totex balloons.  

As noted at least some of the improvement will be down to the light winds, slow ascent rate and really heavy payload.  Flights with a slow ascent rate show significantly less motion and the more massive the payload the less its subject to perturbations of the wind - not that I would recommend everyone rushes out and starts flying heavy payloads.

One thing that worried me about the flight was just how much it weighed - it must be several Kg??  If the landing speed was 8-9m/s vertically and about 8m/sec horizontally this puts the impact speed at 11m/sec (25mph) - which is really quite worrying for that weight of payload - particularly as the gyro arrangement all appeared to be outside of any impact protection.  I must confess sweating a bit during the descent as the predictor put the landing spot in Ledbury of some of the time. 

Still well done (all except the weight) - impressive results.

Steve

On 28 May 2013, at 15:21, richard....@gmail.com wrote:

All,

 

Firstly a big thanks to all of the early risers helping me to track BABSHAB last Sunday. We had 52 people tracking it at various points during the day which meant that I have a full complete and uninterrupted set of decodes from the flight which is fantastic. I had a couple of calls helping me in to locate it which were also really helpful. Thankyou.

 

Successes

 

1.    1.   The stabilisation gimbal worked pretty much as planned. On the launch videos here http://www.flickr.com/photos/91049302@N00/8859148610/ (external) and here http://www.flickr.com/photos/91049302@N00/8858583752/ (on capsule) you can see that it helps smooth the motion of the capsule within 30 or so seconds. After that it stayed nice and stable. None of the still photos have got any more than 10 degrees of tilt on them, and only around 1 in 15 have any form of blur. Given that there are 1,500 of them that’s a good result (although I can’t claim it was anything other than a very still day either)

2.     2.   Mounting the gyro batteries outside in the cold worked as planned. They were active on the way up (when the capsule needs stabilising), stopped working at the top of the flight (when you don’t need them), and started up again when the capsule came back down and warmed up (you can hear them starting up one by one in the descent videos). One was still going when I found the capsule 5 hours after launch.

3.     3.  Mounting a bearing in between the parachute/balloon and the capsule was a real success from a video perspective. The gopro struggles with rapid changes of light and dark (which is what you obviously get up there when the capsule is spinning) and having a bearing in there really helps to eliminate that. Compare and contrast the video from the last flight http://www.flickr.com/photos/91049302@N00/7155797215/in/set-72157629918448066 with the bearing mounted one here http://www.flickr.com/photos/91049302@N00/8845053028/  - exactly the same camera but very different results. Whereas the gimbal is reasonably complex to implement on a flight, the bearing is really really easy and could be a decent low cost addition to quite a few flights I would imagine. Get in touch if you want to investigate this with me, it would be pretty easy for me to put a fairly standard CAD file together that could be printed out at a low cost to be added to most flights.

4.     4.  3D-printed cage and carbon fibre worked well to protect the camera and electronics. There was no failure of any of the plastic components until the capsule hit the ground despite it being exposed to very cold temperatures, and then only minor breakages – I’d got a bunch of tethers all over the package to keep everything together in case of failure but none of them were used. The package hit the ground pretty hard (8-9m/s) as the balloon had wrapped around the parachute, but the SLR was undamaged despite the payload being quite heavy relatively speaking. There was also zero ingress into any part of the payload despite it landing in a rocky field.

5.     5.  Magic Lantern (the SLR equivalent of CHDK) worked well. No reason why it shouldn’t if the camera was kept warm I guess, but was still an unknown before the flight and its now flown successfully on a hab.

6.      6.  Nothing dislodges heavy duty Velcro attached to extruded blue polystyrene. That stuff worked awesomely well keeping everything in the right place in the capsule.

 

Areas to improve

 

1.    1.   The ascent rate was biblically slow at an average of 2.6m/s, and anywhere between 1.4m/s and 4m/s on the way up. I had 1.3kg of free lift in the package, which according to the burst calculator should have been enough to get it up at 4.48m/s (maybe doing this to 2 decimal places is a little optimistic…..). As there was little wind at the launch site, it was pretty easy to get the dummy payload neutrally buoyant so I don’t think there was a large scale error on the filling. Burst altitude was 32.6km vs 33.5km forecast (which probably points to a slight overfilling?), but nothing that would point to such a low ascent rate. It was the first time to my knowledge that such a heavy payload had been lifted by such a large payload amongst the group on here, so it may be that there is some other factor at play here (I did think that air resistance on the larger balloon might be a factor here, but it didn’t speed up particularly in the upper atmosphere so I’ve discounted that now). Don’t really know on this one but the next time I’m jacking up the amount of helium I put in it.

 

2.    2.   I’d set the SLR up for a photo every 6 seconds which equated to a 2.5 hour flight to fill up the 64Gb card. This was a bit greedy, and slapped me in the face when the flight took over 3.5 hours to get up there as I don’t have a photo at the highest point. I should have either got a 128Gb card or dialled down the photo frequency to 10 seconds to give myself at least 50% margin for flight time error.

 

3.   3.    My recovery skills were a bit naïve. I assumed pretty much everywhere in the UK would have some form of phone signal to use the TK102 as a backup in case I couldn’t get an accurate fix using the arduino tracker. Instead, great swathes of where we were searching didn’t have any phone signal, let alone mobile internet. Time to invest in better tracking equipment.

 

4.  4.     I’d bathed the arduino in 360 degree polystyrene and was pumping 6V in it. It was pretty warm when I found it. There was some signal drift upwards which suggests it getting warmer but it did stablise. At least on a similar package I’d maybe punch an internal hole and get some of that heat transferred to the rest of the inside of the capsule.

 

5.   5.    I probably go and need to talk to someone on the best settings for the SLR. I’d got it on auto white balance, auto iso etc. (and I still need to check on the spot metering) as I wasn’t confident of putting all my eggs in one basket in terms of unproven settings. However, the photos were generally over exposed which leads me to the conclusion that something wasn’t quite as optimally set as it should have been (although see below)

 

Luck

 

1.    1.   I was really, really lucky with still winds otherwise I would be testing the limits of my household insurance in terms of claiming for a lost camera. Initial predictions because of the slow ascent had the capsule landing anywhere from the Irish Sea to Ireland. In the event it came down only 10-15km further than expected, but that was more luck than anything.

 

2.    2.   I’d got triple redundancy on the trackers, with a TK-102 and a SPOT backing up the arduino. In the event the last text the TK-102 sent was when it was a few hundred metres up I reckon, so was useless in terms of finally finding the thing, and the arduino wasn’t great because I didn’t have a yagi and the area where it landed was quite hilly. The SPOT came through pretty well once I’d got internet so whilst I thought 3 different trackers was overkill before the flight, it did make things a little easier to find it.

 

If you can help

 

1.    3.   The photos from the SLR are “OK” and a little better than before, but not a spectacular improvement from when I shot last year with a compact and are, in general, a little over exposed. I shot in RAW so someone with the ability to manipulate those type of files effectively for balance, exposure etc. might be able to do something to correct for my setting errors. If you know what you are doing in terms of RAW manipulation, or know someone who does, or just simply want to play around with one and want a couple of RAW files to play around with email me richard_...@yahoo.co.uk

 

I'll post more photos and videos as I get some time to manipulate them, in the meantime there are a few others on my flickr site

Cheers

 

Babs

 

 

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Steve Randall

Random Engineering Ltd

st...@randomaerospace.com

+44 7802 242135

[Ed Moore]

That said, a lot of early UKHAS payloads, including most of ours, were much heavier than the average payload today - ~3kg was not uncommon. I don't recall there ever being an issue with unpredictability of ascent rate being correlated to mass, and we have plenty of data in the 4-5kg space and a couple of datapoints (>10kg, without wishing to cause too many heart palpitations) heavier than that. The ascent rates were always pretty much as expected.

However, we did go to some lengths to ensure good chute design, and yes 8-9m/s vertical rate is quite a lot more KE than you'd want. We included things like pyro cutaway of the balloon after burst to stop tangling, and in the case of the heaviest payloads, split them into two lighter parts to land separately under their own parachutes. This is all detailed in my ukhas talk from 2011 if anyone is interested.

We did also have an uplink to initiate cutdown, and real-time prediction in car (not via the website, local and standalone) showing all the landing sites should nothing work (ballistic reentry), everything work nominally, just the reserve chute deploy, and other permutations. Then we could initiate cutdown when we were happy that all the predicted landing spots for each case were somewhere safe (having done a few test flights to confirm the predictor was reliable and our chute performed as designed on lighter payloads).

I'd *always* look at mass minimisation first and foremost, but where someone is trying something interesting and new that happens to be 4kg, I'd sooner have discussions about engineering and strategic ways of minimising the risk of a heavier payload rather than just discouraging it on the basis that it weighs more than a powershot and and arduino in a box. That's not to say light stuff isn't interesting (e.g. pico is great) but there's a lot more to do in near space than bleep, and we surely have enough wonky pictures of black sky (or something on a stick infront of it) by now. Surely?

Ed

[Steve Aerospace]

I'd agree with pretty much everything you say Ed.  The more risky the payload the more effort that needs to go into mitigating those risks. 

I'm getting fed up with people flying increasingly stupid stuff to the edge of space (and that includes my own commercial work).  I find it frustrating that marketing folk can't by now come up with something a little more original - but I've always taken the view that I'd rather fly it myself than let someone less experienced have a high profile cock up.  

I read this blog the other day: http://astroengine.com/2012/01/29/put-the-weather-balloon-back-in-the-box/ and it completly resonated with me.

I got fed up with seeing yet another set of near space photos and video about 5 years ago.  I've not flown a camera for myself since before then (but plenty for commercial work).  Occasionally someone comes up with something new (like stabilisation) or an interesting shot - but otherwise I don't see the point of repeating what other people have done so many times before.

Steve G8KHW.

[Steve Daniels]

Have been asked by a local radio club and scout group about doing a balloon flight.

This is likely to be a one off, so not much point getting the kit to program a pic etc.

Mostly just need a small balloon, parachute and obviously a UK legal tracking system. Not aiming for an altitude or distance, just the scouts having fun launching a balloon, and finding it, or at least getting it back.

So really after a price and someone who can supply.

 

I live under a main air route so probably not launching from here, not sure about that, will need to check. BHD DVOR is about 2 miles from me.

 

Any help appreciated

 

Steve Daniels

Amateur Radio Callsign G6UIM

APRSISCE/32 Beta tester and WIKI editor http://aprsisce.wikidot.com