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Students' Experiments To Fly By Glider To the Edge of Space
techmage writes: In 2002 Steve Fossett and Einar Enevoldson set the altitude record for a glider climbing to 42,000 feet in the Perlan I. This year the Perlan II glider will attempt to reach over 90,000 feet. Carried aboard will be be 10 science experiments from students participating in a Teachers in Space contest. Some of these experiments push the boundaries of what can be done at the K-12 level. This news article has a lot more detail on what these kids are sending.
To the edge of space! To the edge of space!
Teach metric while at it, eh.
I can't see from the article or the wonkypedia page where they expect to get enough speed from to retain that sort of altitude. They mention carried aloft by air currents (mountain waves). Err , even assuming those currents will get you to 90K feet (I doubt it) they're not going to get you to the 200-300 knots (heavier U-2 need to do 370 but it was "only" at 70K feet) you'll need to maintain that altitude without them guys. So unless by "gliding" they simply mean falling fast from height until they hit another updraft then to me this seems a bit of a non starter.
For those struggling to understand the title:
Glider to fly students' experiments to the edge of space.
90000 feet doesn't even scratch it. 90000 meters would qualify but 90000 feet? Lame. Students, stop thinking of space and start considering your future seriously: you will probably live a nomadic hunter-gatherer lifestyle if you're reasonably lucky. Some of you may be employed as servants of the Ruling Elite and those will have a chance of a more or less fulfilling life as long as they deem you useful. For the rest of you a bleak life of poverty awaits, cut short by violence, illness or hunger. Class dismissed. Please sign the forms for the eversleep pills those of you already in possess of the parental consent.
I'm a licensed pilot. If I was preparing to fly a glider twice as high as the previous record, I'm not sure I would want anything on my plane not 100% required for my flight. The first concern is weight. The second concern is that I really don't need anything extra to worry about. There are already enough risks involved. I'm not an expert on the flight envelops for gliders at this kind of altitude, but I'm going to guess that the plane will be at the knife edge between stalling and over speed. Gliders at 10,000 feet on a hot summer day get bounced around. A lot. They have shoulder straps for a reason. Storms have been known to remove their wings. Where there is powerful rising air, falling air can't be too far away. At 70, 80, 90,000 feet, a plane with huge, long wings might struggle to deal with the air currents.
An unmanned balloon can hit 90,000 feet and carry a small payload. There are other ways to get these experiments to the edge of space.
Well, we've had a nice conversation, and nobody is mentioning the obvious question: what is the racial makeup of these students that are having their experiments carried aloft? I see one in Georgia, a historically African-American state, and Puerto Rico, Latino, but the rest look as lily-white as the X Games. How did Slashdot miss this angle of the story? News for nerds, remember? Stuff that matters.
And the really easy one - what kind of shirt was the spokesman wearing when he made the announcement? This kind of fashion news trumps any kind of scientific achievement, as we know from empirical evidence.
Shutting down free speech with violence isn't fighting fascism. It IS fascism!
"Whoosh"
Now take our glider to 90.000 feet. At that altitude, assuming standard atmosphere, the temperature is -49 C. Speed of sound is 583 knots. Your minimum true airspeed for sustained flight would be 111 knots or 10 indicated. At 90,000 feet, 111 Knots is Mach 0.19 which is greater than your maximum Mach number of 0.16. This theoretical glider cannot maintain level flight at 90.000 feet.
Solving this problem requires an airframe with a very large ratio between minimum and maximum airspeeds. Most conventional airplanes have a ratio of about three to one. Our example had a ratio of 11 to 1. This is where the U-2 reaches its limit and am told the min and max speed are very close at high altitude. The SR-71 solved this problem by increasing the maximum speed, but the tradeoff is a greater minumum airspeed due to the increased weight. It is critical that the tradeoff leads to a greater ratio of max to min airspeeds.
Doing it at the other end, reducing the minimum airspeed, would be much more challenging, because you would need to design a structure that can fly at very low speeds, but still have the aerodynamic stiffness and strength to be safe at higher speeds up to around Mach 0.2. It might be possible, but is definately not easy. I'm not aware of any manned fixed-wing aircraft that can fly as slowly as 10 knots and still have maximum speeds in the 100 kts range.
Critical mach number can be a problem in conventional sailplanes when they get above about 20,000 feet. The pilot needs to be aware that flutter will begin at lower indicated airspeeds than the red line on his airspeed indicator. I would leave 90.000 feet to either a U-2 or an unmanned model airplane. I do not think it is practical in an amateur-built experimental glider attempt to fly that high. But I am sure somebody will attempt it.
I was like "Fabulous!"
I'm not an aeronautics expert but isn't there a huge risk of snapping the wings off the glider? When you get close to space there's not much air which means the glider will essentially reach freefall and hit terminal velocity. The real problem is when it re-enters atmosphere you go from no wind resistance to wind resistance that shock could rip the glider apart. Hope they have an expert on their project. The "safest" way is to try to nose dive the glider until it reaches enough atmosphere for the wings to generate lift and then to pull up carefully?