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Ballooning into Space
flyboy writes: "Two ballooners are going to attempt to get to 132,000 feet in a helium balloon named QinetiQ1. They are going to do this wearing spacesuits and sit in what looks like armchairs in an open gondola. From that altitude the sky is black and you look down on whole countries in one go. It looks like they might actually do it as well, since they have some serious backing, they are sponsored and supported by the former DERA, who have lots of experience in all things aeronautic."
Yeah, it's an Aussie who claims with a straight face that it's a scientific experiment, not a stunt. (Of course, he's already sold the rights to a television producer..."Pay no attention to that man behind the curtain, Dorothy.")
Anyway, here is the story.
Here is at least one of NASA's pages about balloons.
There's an ad for suborbital space flights starting December 1, 2001. Price, $98,000. This has to be an old, bogus site; it's supposed to use the Vela "Space Cruiser", which was never built.
Nice, but 132000 feet is only 25 miles, just half of what USAF awards astronaut wings for (50 miles, and some X-15 pilots earned them). Even less than half of the 100 km that the International Aeronautical Federation considers the edge of space.
Still, it sounds like a fun ride!
-- Alastair
I think you are right, but your analogy isn't really fair. One reason you can't see the Empire State building from the Sears tower is that Earth is in the way. (Earth is roughly spherical, remember?).
The other problem with viewing objects near the surface of Earth is that when you look horizontally, you are looking through relatively dirty air. The problem is much less severe when looking up, because the air rapidly clears and thins as you ascend.
What we need to know is how bright is this thing going to be and what angle does it subtend from 600 miles away? A bright object can subtend a small angle (think supernova) and be visible, and an object which subtends a large angle can be dim, yet still be seen. I believe the moon and sun subtend about 30 minutes of arc, so I imagine anything that subtends, say, half a minute of arc would be considered visible (this is a guess) although if there were poor contrast (i.e., if the object is sky-colored), this wouldn't hold true.
At 600 miles, 0.5 minute of arc is approximately 460 feet. I couldn't read the article so I have no idea how big this baloon is, but I doubt it is 460 feet in any dimension. So to be visible at 600 miles, I think it would have to be bright (e.g., if it were low in the eastern horizon while the sun was setting, it might be quite bright.)
MM
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It depends on the distance to the earth's center of mass. Double the distance from the center of the earth, and you'll quarter your effective weight. Since the radius of the earth is roughly 3960 miles, and these guys are planning on going to about 26 miles up, they're going to weigh 98% of what they do on earth.
Talk about ultra slim-fast. Not much of an effect, really.
Claimed to be the size of a coupla jetliners at altitude...might meet that 460 foot minimum.
Writers imply. Readers infer.
http://www.jpaerospace.com/advanced.html
gigantino.tv - Heavy but weighs nothing.
Awfully, awfully high. The radius of the earth is, what, 4000 miles.
Force due to gravity varies inversely with the square of the distance.
So what's the difference in gravitational force from being at sea level, 4000 miles from the center of the earth, to 132000 feet, 4025 miles from the center of the earth?
4000^2 / 4025^2 gives me around 98%. So I'd weigh a few pounds less at that altitude.
To weigh only half as much, you'd have to be about 1700 miles above the surface, or about 9 million feet.
Earth big.
Of course, by the time you get 250,000 miles away (like the moon) you'd feel less than 0.03% as much gravity from earth.
And keep in mind that all of this assumes you are STATIONARY in relation to a point on the earth's surface. If you're orbiting, you don't feel gravity.
- Peter
INsigNIFICANT
This does not really strike me as a major aeronautical achievement.
Col. Kittinger did a 102,800ft rise in a balloon back in the early 60s (Project "Man high"). The thing that makes this ballon trip unforgettable to history (at least for me and at least until somebody pushes the limit) is the fact that he opened up the gondola he was hanging in to throw himself out into the hands of gravity for 18 1/2 miles.
You can read up on it here and here
+++ath0
Horizontal is in quotes above because it's not quite the right word. More properly, it's a velocity vector normal (or perpendicular) to the acceleration vector. Since the direction of the acceleration vector keeps changing as the position of the vehicle changes, the velocity vector keeps changing too -- as it must; there's an acceleration acting on it. The equations to compute the initial velocity needed to keep a vehicle in orbit at a particular altitude are not complex.
This is exactly the same physics that keeps the Earth orbiting the Sun and the Moon orbiting the Earth, just on a smaller scale.
The writers of Star Trek never understood how this worked. In TOS there were a number of episodes where the engines had been damaged or sabotaged and the orbit was somehow rapidly decaying. Only a moron would have put them into such a low orbit that it needed constant thrust from the engines to maintain it in the first place.
"Weightlessness" is also achievable by falling at the same acceleration imposed by the force of gravity. For the Earth, that's about 9.8 m/sec^2. Astronauts train at weightlessness for brief periods by doing just that -- they get into a specially modified cargo plane, fly up as high as it will go, then pull into a steep dive. They float around inside the plane just as they would on orbit for as long as the dive lasts.
The balloon will never be travelling anywhere near fast enought for any of this to occur.
And the brethren went away edified.
This could be done with a small stabilizing chute. It was used in the legendary Kittinger jump (Project Excelsior). This guy was jumping from 19 1/2 miles up, and 16seconds from jump time a small stabilizer chute would automatically open to stop spinning. Tests with Dummys back then have shown that an aerodynamically unstable object like a human can easily hit 200rpm in free fall. 140rpm for a minute are considered fatal.
Oh, and if you are tired, remember it will be short nap - 19 miles are crossed in less than 14 minutes.
+++ath0
For the real scoop...
Go to the Sun (UK) newspapar.
The article is here...
Packed with insightful scientific observarions such as:
"Their vast balloon -- 400 times bigger than normal ones -- should be visible from the ground as it ascends."
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