Huge Balloon Lofts New Telescope 85
Science Daily is reporting that a new solar telescope has been launched via an enormous balloon filled with helium. Dubbed project "Sunrise" the National Center for Atmospheric Research (NCAR), NASA, Germany's Max Planck Institute for Solar Physics, Spain's Astrophysics Institute of the Canary Islands, and the Swedish Space Corporation all partnered to launch the balloon in order to view never before see features of the Sun. "The project may usher in a new generation of balloon-borne scientific missions that cost less than sending instruments into space. Scientists also can test an instrument on a balloon before making a commitment to launch it on a rocket. The balloon, with its gondola of scientific instruments, was launched successfully on the morning of October 3 from the Columbia Scientific Balloon Facility in Fort Sumner, New Mexico. It flew for about 10 hours, capturing stable images of the solar surface and additional data from the various instruments of the sophisticated payload. The gondola then separated from the balloon and descended with a parachute, landing safely in a field outside Dalhart, Texas."
Not a scientific flight -- only a checkout flight (Score:5, Interesting)
Strangely enough, some the components of sunlight at 120,000 feet altitude are not well known. Some interesting ultraviolet lines (the "h" and "k" lines from Magnesium) are thought to be visible there, that are not visible on the ground -- but nobody has yet characterized the ultraviolet absorption spectrum from the very upper layers of the stratosphere and from the mesosphere. Most telescopes that have flown so high were rocketing through on their way to space, rather than floating under a balloon. So this first flight was both to test the pointing (and other flight control) systems, and to double check that some desired wavelengths are present and usable at the target altitude.
Even the test flight of SUNRISE was a real accomplishment: it is far from the ideal of small, cheap, lightweight, quick-and-dirty payloads under scientific balloons, and is run more like a space mission both in terms of payload complexity and in terms of team management. The team is multinational and the payload is subject to rigorous engineering and testing.
The balloon flight environment is in some ways more harsh than the vacuum of space: payloads are subjected to wild temperature swings on climbout, and the thermal environment is not nearly as controllable as it is in empty space. On the other hand, launch and flight are very gentle compared to unmanned space shots.
Re:Poor Images (Score:4, Interesting)
helium - the only use-once element (Score:4, Interesting)
There are renewable resources (trees, etc.) and non-renewable resources (oil, etc.). But at least the raw elements of these resources stay around on Earth, and can conceivably be used again in the future for something else. In essense, the elemental composition of the earth has remained mostly constant for the past few billion years; it's only the molecules that the elements are bound up in and where that changes over time. Put it this way, if humans die off tomorrow, there'll be plenty of new oil for the insect overlords that evolve in a billion years, because the raw material for the oil is still churning around in the Earth's biological and geological systems.
But helium... well, helium is special. It has two interesting properties. Firstly, it is a very light element. Hydrogen and helium are so light that as individual atoms they freely escape the Earth's gravitational system and leak out into space. That means forever. Secondly, it is completely inert. It does not and cannot bind to any other molecule to weigh it down. This is in contrast to hydrogen, which is almost always bound up in a molecule of some sort. Thus, helium is the ONLY element that, when released into the atmosphere, will eventually leak out into space and be lost to the Earth forever. The only reason we have helium on Earth now is because a bunch of it is trapped in sand particles (that's where we mine it from). But once we mine it and use it, it's gone. And I mean gone gone. Deep space gone. Helium is the second-most abundant element in the universe (and the sun has a lot of it), but unless it's available on Earth, that fact is completely useless to us. We can't make new helium, other than through nuclear fusion of two hydrogen atoms. And that's not a manufacturing process we (or the future insect overlords) are ever going to undertake.
And this is all a great shame, too, since helium, being the lightest inert gas, is incredibly useful. I can't help but think that in a few hundred years (yes, I realize that it's probably that far away) humans will be kicking themselves for having blown helium in such great quantities in complete disregard for the fact that it could never, for the rest of humanity and beyond, be used again.
Think about that the next time you order a dozen helium balloons for your kid's next birthday party!
Re:Poor Images (Score:3, Interesting)
First off, you need a parabolic mirror. The natural shape for inflatables is ellipsoid, not a parabola. That's a problem. The natural shape for a tensioned structure hanging is a catenary curve, also not a paraboloid. However, if its mass is insignificant in comparison to a uniform force applied to it, the natural shape is indeed a parabola. That is, to say, you can make inflatable parabolic mirrors by using a thin, metallized film under as much tension as possible within a glass ring (glass is typically used because of its low thermal expansion). If a pressure differential is applied across the membrane, you get a parabolic mirror.
Now, make two sides to this: one side loose, transparent polyethylene (like "ghost balloons"). Polyethylene since it doesn't absorb infrared well at all. The other side is the tight metallized film mirror. The whole device is inflated with helium. An L3CCD is mounted on a series of actuators on the other side to allow for automatic collimation. Ducted fans are mounted to the exterior on dampened booms to reduce vibration. A radio subsystem, battery bank, and laptop are integrated as payload. The craft, flying in the mid/upper stratosphere, would encounter essentially no turbulence; the stratosphere is dynamically stable. Almost all of the atmosphere would be beneath, so the seeing limit would be miniscule. The primary could be positively gigantic. All of the components except for the electronics and the helium would be dirt cheap. By not being in orbit (as NASA's experiment with inflatable telescopes), there would be no micrometeorite impacts and skin oscillations from changes in solar heating would be minimal (LEO spacecraft experience frequent day/night cycles)
Re:helium - the only use-once element (Score:3, Interesting)
I thought helium came up with Texas oil. Not all oil, but US oil was particularly rich in it. In the 1930's the US did not like exporting the stuff as you could fill zeppelins with it. That's why the British filled the R101, and the Germans filled the Hindenberg with hydrogen. In the UK, we used to collect all the helium we could from low-termperature experiments, stuff it into cylinders, and send it back for re-liquefaction. In the US, they just let it boil away at the time.
At the time, I was told that something like 1/3 of the helium in known oil reserves has gone, and that was 20 years ago. Probably there is more in sand, and other places, but it will cost more to get out. I saw the picture of the balloon and thought that was a lot of helium we won't be seeing again. You could re-compress the helium to make the balloon descend, but I expect a lot will have diffused through the skin. It does that. That's why rubber helium balloons go flat.
Actually, now we know more about electrical safety, and not to paint our zepplins in thermite, hydrogen is a lot less scary. I am not sure how greenhouse-ish it is as I expect it keeps on rising like helium. But you can always burn it when it vents.