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Thread: The space flight thread

  1. #31
    Verified VCDS User vreihen's Avatar
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    Space station welcomes 1st returning vehicle since shuttle

    Associated Press
    June 5, 2017

    CAPE CANAVERAL, Fla. (AP) — The International Space Station welcomed its first returning vehicle in years Monday — a SpaceX Dragon capsule making its second delivery.

    Space shuttle Atlantis was the last repeat visitor six years ago. It's now a museum relic at NASA's Kennedy Space Center.

    NASA astronaut Jack Fischer noted "the special significance" of SpaceX's recycling effort as soon as he caught the Dragon supply ship with the station's big robot arm.

    "That's right, it's flying its second mission," Fischer said. "We have a new generation of vehicles now led by commercial partners like SpaceX."

    SpaceX is working to reuse as many parts of its rockets and spacecraft as possible to slash launch costs. The California-based company launched its first recycled booster with a satellite in March; another will fly in a few weeks.

    The Dragon pulled up two days after launching from Florida. This same capsule dropped off a shipment in 2014. SpaceX refurbished it for an unprecedented second trip, keeping the hull, thrusters and most other parts but replacing the heat shield and parachutes.

    Until their retirement in 2011, NASA's shuttles made multiple flights to the space station.

    This new 6,000-pound shipment includes live lab animals: 40 mice, 400 adult fruit flies and 2,000 fruit fly eggs that should hatch any day. The mice are part of a bone loss study, while the flies are flying so researchers can study their hearts in weightlessness. Even more than mice and rats, the hearts of fruit flies are similar in many ways to the human heart, beating at about the same rate, for instance.

    Some of these animals will return to Earth aboard the Dragon in about a month.

    SpaceX officials anticipate using Dragon capsules as many as three times.

    "It's starting to feel kinda normal to reuse rockets. Good. That's how it is for cars & airplanes and how it should be for rockets," SpaceX founder and chief executive Elon Musk said via Twitter following Saturday's liftoff of the Dragon and landing of the Falcon rocket's first stage.

    Musk said the latest touchdown was "pretty much dead center" at the SpaceX landing zone at Cape Canaveral Air Force Station. Liftoff occurred next door at Kennedy Space Center.

    The Dragon is the only station supply ship capable of returning items, like science samples. On Sunday, an Orbital ATK cargo ship named in honor of the late John Glenn departed the station. It will remain in orbit a week before burning up in the atmosphere upon re-entry. Glenn, the first American to orbit the world, died in December at age 95.

    "Godspeed & fair winds S.S. John Glenn," Fischer wrote in a tweet.





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  3. #32
    NostraJackAss Jack@European_Parts's Avatar
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    The Tang Effect and Theorems

    Side-effects and the Tang Effect

    William Mitchell was a food scientist who invented the orange-flavored drink called Tang. He also invented other foods such as Cool Whip—an artificial type of whipped cream—and Pop Rocks—an “exploding” candy.
    Today I want to talk about theorems, proofs of theorems, and how they relate to Tang.
    There is an effect that I will call the Tang Effect. Sometimes a great endeavor creates a side-effect that becomes more important than the endeavor itself—that is the Tang Effect. In mathematics and theory some theorems solve long-standing open problems, while some do not. Most of the time the proof of a theorem uses methods that are already known, but the proof can still be clever and hard to discover. Some of the time, however, the proof of the theorem contains a method, a trick, a lemma, that is more important than the theorem itself. Importance is measured by how useful the method, trick, lemma is to other researchers—whether the method can be used to solve other problems.
    The urban legend is that Tang is a perfect example of the Tang Effect. It is not. The great endeavor was the early NASA space program, which eventually put men on the moon. The legend goes that Tang was one of the side-effects that NASA created as part of the US space program. Unfortunately this is not exactly correct. Tang existed before the space program. It is an orange powder that when added to water creates an orange flavored drink. Not my favorite cup of tea—I vastly prefer real OJ.

    What happened is that Tang had its sales skyrocket (OK, bad pun) when Tang was used on John Glenn’s Mercury flight and on subsequent Gemini missions. Apparently the water on board the space capsules was safe for the astronauts to drink, yet had an unpleasant flavor, so it was Tang to the rescue. Add a bit of the Tang powder to the water and the drink was quite palatable. One outcome, besides increased sales, was the belief that one of the side-effects of the space program was Tang. There are of course many valid and more-important space technology spinoffs, but still I like the name “Tang Effect,” so I hope that is okay.
    Let’s look at some mathematical examples of this effect.


    Szemerédi’s Theorem: Endre Szemerédi proved that for a given density and a , there exists an such that every subset of of size contains a -progression. That is, it contains integers and so that .
    are all in the set. This theorem was a breakthrough of the first magnitude, and is an amazing milestone in the theory of combinatorics. But I would argue, with all due respect, that the proof is more important than the result. I can think of no paper that uses this theorem to prove something—they must exist, but I am unaware of them. I do know of hundreds, if not thousands, of papers that use a key idea from the paper. This is of course the famous Szemerédi Regularity Lemma. This is a perfect example of the Tang effect.
    Wiles’ Theorem: Andrew Wiles proved, as we all know, that Fermat’s Last Theorem is actually a theorem. That
    for an odd prime implies that . This theorem solved a 350 year old problem, is again a breakthrough result, and is amazing. Again, with due respect, I believe that it too is an example of the Tang effect: the methods Wiles used are perhaps more important than the actual result that a particular Diophantine Equation has no solutions. His proof opened the door for number theorists to prove the full Taniyama-Shimura-Weil conjecture, among other things. Wiles “only” needed a special case of the conjecture in his proof.
    Recall what Carl Gauss said in reply to an attempt in 1816 to get him to work on Fermat’s Last Theorem:
    I confess that Fermat’s Theorem as an isolated proposition has very little interest for me, because I could easily lay down a multitude of such propositions, which one could neither prove nor dispose of.
    I have been told that one reason that Wiles was so excited to work on Fermat was precisely that it had been connected with the Taniyama-Shimura-Weil conjecture. This meant that even one solution to the equation would destroy the conjecture. It was no longer as Gauss said “an isolated proposition,” and so it was extremely important to find a proof. Moreover such a proof almost had to light up a whole area of number theory. Which it did.
    Turing’s Theorem: Alan Turing proved that the halting problem is undecidable. There is no uniform procedure—-that is, no algorithm that always halts and gives a yes/no answer—that can decide whether any computation will or will not halt. The result is again a breakthrough and an amazing achievement. But again, in my opinion, this is another example of the Tang effect: the theorem is less important than the proof. The proof introduced the notion of a Turing Machine, and the application of Cantor’s idea of diagonalization in computation theory. The first notion is the cornerstone of all modern complexity theory. Where would we be without this beautiful model of computation? The second is still the basis of lower bound efforts against uniform complexity classes, not to mention that it sometimes applies even to non-uniform circuit families.

    Finding The Tang

    One further comment is that in major new results, sometimes the proof does not make it easy to see the Tang effect, or even state the “tangy” new result clearly. The proof may have many lemmas, where parts—not all—are potential Tangs. Most of the lemmas may only useful for the proof at hand. So finding the Tang in a long complex argument may be difficult: it may not even exist. But the reward for discovering the “Tang” can be enormous, and can yield a powerful new tool that even the author(s) of the original proof may not have realized was there.

    Open Problems

    What are some other examples of the Tang effect in mathematics and theory?
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