Re: [UKHAS] Re: Hyowee 800g floater?

[Mark Jessop]

The prediction for Friday looks very dangerous with a 4.4m/s ascent rate:
http://habhub.org/predict/#!/uuid=65936621ce5c4ae8f1f2f772075d11cf749fe8e5

I'd seriously suggest adding more gas, and raise the ascent rate to say,
6 or 7m/s:
http://habhub.org/predict/#!/uuid=7608787356cccf526790bd16161ad2293996e253

It'll cap your altitude, but it's better to have not go as high and get
the payload back, than go very high and drop your payload in the sea.

- Mark

On 10/01/13 5:33 PM, Trevor Cousins wrote:
> I got the date wronf on that url but the parameters are the important
> thing.
>
> TC
> --
>
>

[Anthony Stirk]

Hi Trevor,

Personally I would use a smaller balloon if you have it and lots of gas as Darkside said. Sub 5m/s ascent rates *may* float ( with the 1600g balloons its very probable). The Hwoyee balloons are a little inconsistent on burst altitude we've had a 1000g balloon with a similar weight payload get to just shy of 40km.  

I'd concur with Darkside and suggest a minimum of 6m/s ascent for this one. 

Anthony

On Thu, Jan 10, 2013 at 6:55 AM, Trevor Cousins <trevor_...@yahoo.com> wrote:

I have a launch tomorrow morning (Friday) with one of these balloons. I would LIKE to launch with these conditions (4.4m/s, 2800L, 1200g)

http://habhub.org/predict/#!/uuid=e441a46307b8f927eb9d0ee65ab1d890e82e8633

From your experience would anyone expect that to be a bad idea. Denmark is small so I absolutely do not want to float!

Thanks,

Trevor Cousins

--
 
 

[David Akerman]

I'll concur with both of them.  4.4 risks a float.  I've had a 1200 hit 40km with even with a slightly higher ascent rate albeit that was H2.  40km with that prediction ends up in the sea.

Given the distance of the flight, and how close the sea is, I'l be going for 6m/s minimum, which reduces the distance travelled and time in the air.

Dave

--
 
 

[Anthony Stirk]

It may float. It may not float. Even with a boat sea landings may result in loss of payload as it can be quite hard to find them once they are in the sea. Anyway you have the advice, good luck on Friday.

Anthony

On Thu, Jan 10, 2013 at 8:21 AM, Trevor Cousins <trevor_...@yahoo.com> wrote:

My reasoning is rendered a bit void because of the short distance I have to the coast - I have no choice but to go for at least a 5m/s rate.

Here's the question though: if I DID have enough distance to get to 30km alt with this payload and this balloon would I be in danger of floating?

If we did land in the sea that's sort of ok because the national guard have a boat in the area waiting for  call from us!

TC

--
 
 

[Steve Aerospace]

The 4.4m/sec 09:00 lunch tomorrow (http://habhub.org/predict/#!/uuid=5da14ecb5116a94807112880f2c08b529f0a05d8) is way,way too close to the coast. Its quite a long flight path I'd be giving the sea a wide birth - especially along the general direction of travel.

Certainly the Hwoyee balloons often achieve significantly more than their predicted burst height but I don't know of any 800s (or even 1000s) that have shown any indication of floating? (esp. with 1200g payload) can anyone recall a flight?

If you are filling the balloon outside you can easily get the neck lift measurement wrong (especially if this is a first time) - if in doubt add more gas.

Steve

--
 
 

Steve Randall

Random Engineering Ltd

st...@randomaerospace.com

+44 7802 242135

[David Akerman]

I mis-read the OP and thought he was flying a 1200.  AFAIK no-one has been near a float with an 800.  This may however be because people choose them in order to get a short flight so they're paired with reasonably high ascent rates.

Whatever the balloon/payload, with that path I'd be wanting a nice short flight, so as Steve says chuck in plenty of gas.

Dave

--
 
 

[MikeB]

I  agree with Anthony that it will be difficult to locate the payload in the sea, especially if not flat calm. A technique that I used with small drift buoys was to equip them with a mast-mount flash tube that's  activated at dusk. These can be seen after dark at ranges of a few miles from even small recovery ships. 

MikeB

[Costyn van Dongen]

Congrats to you and your team on a very nice flight. And yes, it was exciting if it was going to get wet or not. :)

Internet access was spotty in the chase cars I understand? Otherwise it's quite useful to have the tracker page on a laptop in the car, this saves from having to give directions through the phone. :)

We were curious if you got a correct fix from the GSM/GPS unit at all after landing? The coordinates you gave to Rolf on the phone were quite off.

Cheers and thanks for a fun friday afternoon. :)

Costyn.

[Steve Aerospace]

Looking at the flight data the Ascent rate averaged 4.5m/sec and the sea level descent rate was 6.1m/sec.

A curve fit of those values to actual data :- http://imagebin.org/242588

It looks like the peak altitude string was corrupted as it was being sent.  Burst was probably at about 29100+. Which is pretty much on the money for the burst calculator for Helium.  What neck lift did you fill to?

Given the close fit to the numbers the landing spot was about 30Km off from the day before prediction: 

http://habhub.org/predict/#!/uuid=5da14ecb5116a94807112880f2c08b529f0a05d8

Did anyone do a prediction closer to the launch time?

Steve

On 12 Jan 2013, at 09:10, Trevor Cousins wrote:

Hi Geoff, do you have that as a kmz, csv etc?

TC

On Friday, January 11, 2013 9:16:59 PM UTC+1, Geoff Mather wrote:

Thanks for an interesting flight Trevor!  below is a link to what SKYHAB saw at the burst!
http://www.360cities.net/image/skyhab-20130111-skals-jutland-denmark?override_cache=true#40.80,67.80,110.0

--
 
 

[David Akerman]

Trevor,

The easiest mistake to make is to measure the neck lift when the wind isn't still.  You said on IRC that the wind pushed the balloon to 30 degrees from vertical, and that's *plenty* enough wind to mess up the measurement.  The wind will lift the balloon and you really need to wait for any gusts to stop so you can be sure it's the balloon doing all the lifting.

My second flight landed 10 miles offshore due to this error.

Dave

On 12 January 2013 14:29, Trevor Cousins <trevor_...@yahoo.com> wrote:

Hi Steve, I did a prediction at about 9-10 UT yesterday. It said a neck lift of about 2500g. the package inc string was 1225 g I think. The pipe connector to the ballon was about 300g. I tied a bucket of water with a total mass of 2100g to the pipe and filled until the balloon lifted it - so it should have been lifting 2500g. e continued with the helium for maybe 2 mins just to be sure.

I did a prediction at 9ish UT yesterday, just before the flight and it is here...http://habhub.org/predict/#!/uuid=65a2440396f7999cf28714a6e17d91d91cacc5db The landing point is 7km from the actual!

I put in a descent rate of 6.8m/s based on a 32" parachute.

So maybe my measurements were not wonkey.

TC

--
 
 

[Steve Aerospace]

Oh - I thought that it had been filled inside that nice barn shown on GE - like Dave says - getting an accurate value of lift outside in wind is difficult.  

Trevor the link you gave (http://habhub.org/predict/#!/uuid=65a2440396f7999cf28714a6e17d91d91cacc5db) was an in flight prediction - must have been made about 12:00UTC?

Steve

[David Akerman]

It may have been inside - dunno.  A few of us asked if it was an outside fill on IRC during the flight and looking back I can't see an answer.

Dave

--
 
 

[Costyn van Dongen]

Trevor said on the livestream that they'd started filling inside but then went outside as it wouldn't fit through the doors otherwise. They filled it next to the building so I imagine there could have been turbulence and updrafts there affecting measurements.

Cheers,

Costyn. 

--