High altitude balloon payload, from Sable-3 discussion Options

[dvandorn]

...think of this more of Ranger rather than Mariner...

Hmmm... maybe not the best choice in concepts, there, karma-wise, Doug...

-the other Doug

[ugordan]

Well... considering the fact that Voyagers 1 and 2 were originally to be Mariners (though I have no idea if they would have been Mariners 11 and 12 or not), we *almost* got a second successful pair-launch out of the program!

I'm wondering... had they been indeed called Mariners, would they have both launched successfully or would Vgr 1's Titan booster for example decide to underperform some more?

[AndyG]

Is there an issue with expanded polystyrene at very low pressures? Or is the plastic part of the matrix mechanically strong enough to withstand the expansion of the embedded gas?

Andy, also looking at envelope materials for high altitude balloons - not the rubberised standard Met ones.

[djellison]

Is there an issue with expanded polystyrene at very low pressures?

Tens of thousands of met balloons have gone to 100k+ without any trouble of that nature - as well as probably dozens of amateur projects. They all use polystyrene or similar materials.
oug

[djellison]

Status update :

Proposal :
<2kg payload - on the order of 20 x 20 x 30 cm external + extras.
VHF APRS GPS for realtime tracking
Multiple internal cameras for mosaicing Horizon-to-Nadir view
External camera on independant power supply using WAM or Fisheye lens for self portraiture
Standalone system for tracking via SMS / GPRS

On order:
36 inch chute ( suitable for up to 2kg )
Microtrack 300, GPS and VHF antenna.
10 x (cheap lot off Ebay) 31x21x24cm external, 26x16x17cm internal polystyrene boxes
Wide angle mirrors ( circular and rectangular )
Literature study so I can pass the Fundamental radio licence course to allow broadcast by the Microtrack.

On offer:
Independance Backup System from Helvick in form of Smartphone with camera and GPS

Investigating:
Balloon
Gas (both kind of important)
Power supply
Groundstation
Gondola cameras - powershots with intervalometer, or other cameras with a shutter-release via a timing circuit. Will multiple cameras carry keep their intervalometers in sync if set off together - or will a timing circuit be needed - and if so, is it worth tying that into the GMC (even though I said I wanted that to be independent)


Future options for later flights:
Data logging of GPS Lat/Long/Alt, Pres, Temp, Accel ( nice science to tie in to Huygens with accel data) other params.

[volcanopele]

I would seriously look at the design of Huygens as the best analog for this project. It sounds like the camera system is designed to be akin to the Huygens camera system, with three cameras imaging from nadir to horizon. For mosaicking purposes, look at the design of Huygens and how it spun so that full 360 degree mosaics would be possible. of course, make sure it is designed to spin in the correct direction.

[djellison]

I was having similar thoughts, how controlled can we have the rotation (up the hill or down) - because looking at other similar projects, the imagery seems very very chaotic.

Doug

[nprev]

Weight distribution would also be very important for platform stability; you might have to use some soft lead weights to at least get a three-point balance, bottom heavy (thinking of 1/2 oz fishing sinkers...)

Spin's a little harder. I guess some fins to offer wind resistance might help, but wouldn't do much good at peak altitude...

[djellison]

The problem isn't a million miles from MER terminal decent. It's not chute-backshell-lander but it's envelope-chute-gondola.

I'm reminded of this : http://www.jpl.nasa.gov/news/features.cfm?feature=1449

[jamescanvin]

I don't think controlling the rotation is going to be possible, certainly not to the level required to guarantee that we get 100% coverage.

iirc Huygens was designed to spin just to make sure all the images didn't point in the same direction, not to have a controlled sweep to pan the camera. Looking at images from other balloons it doesn't look like forcing the balloon/parachute to rotate will be a necessary, it looks like quite a wild ride.

Lets just concentrate on taking as many shots as possible, it looks to me that we won't have to be too lucky to get good 360 coverage and we have plenty of talent here to fill in any small gaps in the data.

James

[djellison]

Discovered the FM transmitter may be a no-no in the UK

OO - no - 144.800 is good for APRS in the UK Sweet.

Grrrrrrrr

[ngunn]

Doug - I wanted to reply to your paragraph about options for future flights but when I click on 'reply' to your post that part seems to be missed off the quote. Anyhow, you know what I'm going to say - "What, no stereo? " I think this is a significant, attainable, genuinely scientific objective given that weather phenomena are complex four-dimensional things. It could have practical applications not just on Titan but for Venus and the giant planets too. I can see why the first flight should be as simple as possible though.

On the cost issue - would there be some way for us 'spectators' to chip in a little, perhaps anonymously?

[djellison]

For stereo to work - you either have to have a very long baseline within one payload ( which is a near impossibility given the limitations of size and mass ) - or two simultaneous balloons pointing in the same place, at the same time, at the same altitude ( a near impossibility given the limitations of chaos).

Clouds are usually fuzzy, roughly defined, dynamic objects - I can't imagine that getting stereo imagery of them would be particularly valuable anyway. They're not like a rock. If someone can explain to me how it could be done and why it should be done, then why not....but I struggle to see a means or a purpose at the moment.

You are right however - the first launch ( and indeed I would have thought the first few launches ) are intentionally simple and as far as possible, with redundant systems. i.e VHF GPS, and GPRS/SMS GPS, GMC and onboard cameras etc etc.

And I've got to get a Radio license

Doug

[ngunn]

OK this is getting off topic and I won't keep on about it here, beyond this one post. Understanding the detailed dynamics of atmospheres is surely a major target for planetary exploration. Clouds may be fuzzier than rocks but they can sometimes take quite crisp forms, on scales of just a few metres in some cases. They act as visible tracers of air movements and markers of humidity levels as well as possible compositional gradients of gaseous and suspended liquids and solids. In short they are most worthy imaging targets. I envisage possibly a cluster of mini-balloons descending through a planetary atmosphere each taking pictures in perhaps three different directions. Even with random separate orientations and spins there could be enough dual 'hits' to generate a 3D movie of the atmospheric goings-on. I think this would be an exciting thing to do and could be done with simple 'Ellison' balloons. Getting even one lucky stereo hit with just two of the things in Earth's atmosphere would demonstrate the potential and would perhaps be a technical first.

all this aside I wish you every success with the exciting stuff you are planning.

[AndyG]

Thirty Thousand Metres Via A Plastic Bag

The above is a Flash tool for helping develop high altitude balloons. Briefly: the Met balloons are made of some rubbery compound which stretches under reduced pressure until the point at which they burst. With a given quantity of lifting gas in them, the approximate altitude for the burst can be calculated beforehand. Much more Romantic, and Golden-Age-Of-Ballooningy, are the light plastic/Mylar balloons that are part-filled with lifting gas, and gain sphericality at altitude. These are truly bouyant - with the right parameters, they'll find a level of no-lift, no-sink - which makes them ideal for higher altitudes and longer durations. Naturally UMSF engineers could employ a timer to cut loose the Earth-Return Package from such a balloon and achieve higher altitudes than otherwise.

On to the tool...

There's four yellow sliders, one for altitude, three for the balloon. Set the desired balloon parameters first. Radius is the desired balloon radius, Density is envelope density (970kg/m3 seems to be ok for most commercial polyethylenes) and Thickness governs the quality of the envelope, measured in gauges, as shown below:

Gauge Sort-of-Thing
70 Light Duty Rubbish bags - (those bags which literally are rubbish when they burst after putting hardly anything in)
150 Heavy Duty Rubbish bags
200 Refuse Sacks
800 Heavy Construction Film

Setting the three balloon sliders produces a number of results for the balloon. Most important are the volume and envelope mass.

Now move the altitude slider - as the height increases, the figures for Hydrogen and Helium's excess lift drops. Once the excess lift, for a chosen gas, falls below the payload mass, that's the maximum altitude achievable. At this point, the Hydrogen and Helium required figures make sense - these are the mass and volume of the chosen lifting gas required at sea level.

Example: Radius - 5m, Density - 970kg/m3, Thickness - 70 gauge. Max Helium altitude with 2kg payload = 30500m, 31100m with Hydrogen (so not worth the bother for the added risk?)

Max altitude for same balloon with a 100kg Doug payload (generously including thermal gear and some oxygen) ~14000m.

Enjoy!

Andy