High altitude balloon payload, from Sable-3 discussion Options

[jamescanvin]

Great info AndyG.

Looking at some of the other folk who have done stuff like this, 30 - 35km seems to be reasonable.

Surely we've got to be aiming for the 32km 'Mars surface pressure' mark.

J

[djellison]

At that level it's a little bit about luck - but I'd say the 30km, 100kft, 10% air pressure, mars air pressure type level is a sensible ultimate goal. Maybe not first time around - but eventually.

Doug

[ustrax]

Hey Doug...what do you think of this first approach to a possible name anf badge for the project?...

On following opportunities we could follow this policy and use our beloved ones names...I'm sure each launch would have a distinct personality...

[jamescanvin]

I think that a 2 camera approach is a very good idea. I'm torn between having them pointed in such a way that stitched panoramas are possible versus having them pointed so that we optimize the probability of getting a wider range of individual shots.

Hopefully even with just one camera some nice panoramas will be possible.

Some quick tests:

Nova - images taken 15 seconds apart - altitude change 300ft - altitude 100,000ft


Even at low altitudes and with large time intervals this can still be done.
SABLE-3 - images taken 1 minute apart - altitude change 800ft - altitude (above ground) 10,000ft


If we had two cameras I'd vote for one pointing horizontally and one pointed down at 45 degrees and turned 90 degrees 'portrait', which should give maximum coverage.

It may take a while to sort through the images but with a couple of cameras like this firing quite frequently some pretty spectacular stuff should be possible.

James

[nprev]

Nice logo, ustrax!

Just a general engineering note based on AndyG's terrific table: need to determine an optimum rate of climb (ideally, maximized) in order to minimize thermal effects on the electronics, unless the payload will be environmentally controlled. Major trade-off in all areas is, of course, that more payload weight equals less achievable altitude...

[djellison]

Payload wouldn't be thermally 'controlled' per.se - but something like a foam (there's 3cm thick foil covered foam available at my DIY store) cube which would thermally insulate it from the cold - and then the electronics inside would hopefully keep it fairly warm simply by using up the Whr's.

I knew someone would start thinking of logo's and names before we got too far

Doug

[jamescanvin]

One more stitching test using the SABLE-3 images. These images are fully 6 minutes and 6,400ft apart and still stitch nicely. With two cameras taking pictures 15 seconds apart and we could have 50 images within this time frame, nice.



James

EDIT: just came across this page of records for this sort of thing - http://showcase.netins.net/web/wallio/ARHABrecords.htm

[ustrax]

You know how this guys are Doug...

Seing those images I can't avoid to think about something I already made reference here, I would L-O-V-E to see some video footage with sound...what are the major constraints for something of that nature?...

[djellison]

Storage, Volume, Mass, Power, Money If you can find a small digital camera that can take movies of approx 2 hours onto SD card etc, and last that long on the battery, that's small enough (10 x 10 x 3 cm sort of size) and light enough (<300g) - then maybe. While movies are cool - I think I'd rather have mega-pixel stills than a lower res movie ( although both would be cool.)


Real time video transmission is possible but typically not further than 5km with the transmisison power allowed by the radio spectrum laws.

[nprev]

Payload wouldn't be thermally 'controlled' per.se - but something like a foam (there's 3cm thick foil covered foam available at my DIY store) cube which would thermally insulate it from the cold...

Doug

Yeah, that'd help. Main concern here is electrical connectors. Probably a good idea to seal them with ScotchGard or RTV, which in addition to adding another insulation layer to minimize thermal contraction/expansion would also prevent moisture intrusion/condensation.

[scalbers]

Hi - this link has a nice high altitude photo from the Edge Of Space Sciences balloon group:

http://www.eoss.org/ansrecap/ar_030/recap13.htm

[Juramike]

One possibility might be to put all the batteries in a custom battery harness which is itself inside a small thermos. That should keep them from getting too cold during the trip up. The downside will be making sure that all the connections are nice and tight.

Yet another possibility would be to put a small "box" of solar panels around any package. At least one of the panels would be pointed towards the sun and delivering power. But then you gotta deal with transformers, etc.

-Mike

[JRehling]

[...]

[djellison]

Actually - the altitude will be limited by the envelope which seem to always burst at 80-110kft

Doug

[nprev]

Good point, Doug. However, ascent velocity is still contrained by payload weight, so it's still a significant consideration. For recovery purposes, seems like you want to get up & down as rapidly as possible in order to limit your touchdown CEP.