And the blog in Catalan (see photos) http://teslabs.com/meteotek08/

http://www.flickr.com/photos/meteotek08/3337008176/in/set-72...

If they put a pressure release valve on it (one designed to work by relative pressure differences, not absolute, and I think most are anyway), how high could you get?

I'm guessing to the point where the difference in mass between the helium inside the balloon and the air outside is not enough to loft the camera. But with a light camera that has to be just about outer space, no?

Edit: And despite the risk, I think they should use hydrogen. If I'm not mistaken, it's 1/4th the mass of helium. I don't know how much higher that will take them though, but it has to make some difference.

(And it is atomic mass that matters, but you have to count the mass of each gas particle. In an ideal gas, gas density is the same for most any gas.)

I wonder if it will make much difference though, I think air pressure falls off exponentially, so a doubling of buoyancy won't go far.

But, it's probably much much more expensive (I'm guessing 10x more), so probably not practical for students.

EDIT: http://en.wikipedia.org/wiki/Rockoon

"At over 100,000ft the balloon lost its inflation and the equipment was returned to the earth.

"We travelled 10km to find the sensors and photographic card, which was still emitting its signal, even though it had been exposed to the most extreme conditions."

I launched about 50 balloons of varying inflation levels and groups (i.e. 1,2, and 3 balloons) and attached ribbons to them and tied laminated index cards with a numeric-ID and my email address.

I ended up getting a few responses and I believe one of the single balloons traveled over 76 miles before setting down in someone's backyard. The average was something like 50 miles, and that was on a warm night with <5mph wind.

We launched thousands of baloons with index cards, once a year, in primary school but I never received a reply from any of mine.

It's definitely fun though!

From http://vpizza.org/~jmeehan/balloon/:

Part 101 of the FAA Regulations covers balloons, kites and rockets. The first section of Part 101 spells out exactly which kinds of devices the rest of Part 101 applies to. Regarding "unmanned free balloons," Part 101 applies if the balloon:

  (i) Carries a payload package that weighs more than four pounds and has
  a weight/size ratio of more than three ounces per square inch on any 
  surface of the package, determined by dividing the total weight in ounces 
  of the payload package by the area in square inches of its smallest surface;

  (ii) Carries a payload package that weighs more than six pounds;

  (iii) Carries a payload, of two or more packages, that weighs more than
  12 pounds; or

  (iv) Uses a rope or other device for suspension of the payload that 
  requires an impact force of more than 50 pounds to separate the 
  suspended payload from the balloon.

people do this all of the time -- its a neat experiment for kids of any age

EDIT: It's even more fun with a lawn chair and a person in it http://en.wikipedia.org/wiki/Larry_Walters

'He was immediately arrested by waiting members of the Long Beach Police Department; when asked by a reporter why he had done it, Walters replied, "A man can't just sit around."'

What a quote!

I especially like the part (not sure if it was mentioned in the Wiki article) where commercial airliners were reporting a man in a lawn chair at 15,000 feet. I would have loved to be eavesdropping on some of those cockpit discussions. Hey Bob! Say! Is that a man in a lawn chair over there next to that cloud? Whah?

If I'm not mistaken, they've started an annual race or something in his name.

hahahaha

This is a story with a sad ending. I wonder why he did it?

Looks like it was the 'Nam.

Note I said online map, not Google Earth which is a desktop application. (Although it's still true for Google Earth.) Also note I said aerial rather than satellite, and Russia rather than e.g. San Francisco. It amazes me that such a simple sentence has been misunderstood on all three points. A sign of the changing times?

Oblig. Hack: Quite often I want to refer back to a particular phrase or word in a book, and I have a devil of a time finding it. At times I've methodically re-read 10 or 20 pages in failing to find it. I've wished I could just google the damn book.

I can. By using Google Books or Amazon's search facility. I mention this here, because I wanted to use an expression of Gladwell's in Outliers, about someone "customizing their environment", and then saying " "customize" -- using Lareau's wonderful term" on page 105. I'd misremembered it as "lovely euphemism".