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Posted: 12 Apr 2015 03:23 PM PDT
Excerpt from space.com
This article was originally published on The Conversation. The publication contributed this article to Space.com's Expert Voices: Op-Ed & Insights.
There’s real pressure on the aviation industry to introduce faster, cheaper and greener aircraft, while maintaining the high safety standards demanded of airlines worldwide.
Airlines carry more than three billion passengers each year, which presents an enormous challenge not only for aircraft manufacturers but for the civil aviation infrastructure that makes this extraordinary annual mass-migration possible. Many airports are close to or already at capacity. The International Air Transport Association (IATA) has estimated that, without intervention, many global airports – including major hubs such as London Heathrow, Amsterdam Schiphol, Beijing and Dubai – will have run out of runway or terminal capacity by 2020.
If in-flight refuelling seems implausible, it’s worth remembering that it was first trialed in the 1920s, and the military has continued to develop the ever since. The appeal is partly to reduce the aircraft’s weight on take-off, allowing it to carry additional payload, and partly to extend its flight range. Notably, during the Falklands War in 1982 RAF Vulcan bombers used in-flight refuelling to stage what was at the time the longest bombing mission ever, flying 8,000 miles non-stop from Ascension Island in the South Atlantic to the Falklands and back.
Reducing take-off weight could offer many benefits for civilian aircraft too. Without the need to carry so much fuel the aircraft can be smaller, which means less noise on take-off and landing and shorter runways. This opens up the network of smaller regional airports as new potential sites for long-haul routes, relieving pressure on the major hubs that are straining at the seams.
There are environmental benefits too, as a smaller, lighter aircraft requires less fuel to reach its destination. Our initial estimates from air traffic simulations demonstrate that it’s possible to reduce fuel burn by up to 11% over today’s technology by simply replacing existing global long-haul flight routes with specifically designed 250-seater aircraft with a range of 6,000nm after one refuelling – roughly the distance from London to . This saving could potentially grow to 23% with further efficiencies, all while carrying the same number of passengers the same distance as is possible with the current aircraft fleet, and despite the additional fuel burn of the tanker aircraft.
However, this is not the whole picture – in-flight refuelling will require the aerial equivalent of petrol stations in order to deliver keep passenger aircraft in the sky. With so much traffic it simply wouldn’t be possible to refuel any aircraft any time, anywhere it was needed. The location of these refuelling zones, coupled with the flight distance between the origin and destination airports can greatly affect the potential benefits achievable, possibly pulling flights away from their shortest route, and even making refuelling on some routes impossible – if for example the deviation to the nearest refuelling zone meant burning as much fuel as would have been saved.
Safety and automationAs with all new concepts – particularly those that involve bringing one aircraft packed with people and another full of fuel into close proximity during flight – it’s quite right to ask whether this is safe. To try and answer this question, the Dutch National Aerospace Laboratory and German Aerospace Centre used their flight simulators to test the automated in-flight refuelling flight control system developed as part of the Recreate project.
One simulator replicated the manoeuvre from the point of view of the tanker equipped with an in-flight refuelling boom, the other simulated the aircraft being refuelled mid-flight. Critical test situations such as engine failure, high air turbulence and gusts of wind were simulated with real flight crews to assess the potential danger to the operation. The results were encouraging, demonstrating that the manoeuvre doesn’t place an excessive workload on the pilots, and that the concept is viable from a human as well as a technical perspective.
So far we’ve demonstrated the potential aerial refuelling holds for civilian aviation, but putting it into practice would still pose challenges. Refuelling hubs would need to be established worldwide, shared between airlines. There would need to be fundamental changes to airline training, alongside a wider public acceptance of this departure from traditional flight operations.
However, it does demonstrate that, in addition to all the high-tech work going into designing new aircraft, new materials, new engines and new fuels, the technology we already have offers solutions to the long-term problems of ferrying billions of passengers by air .
Posted: 12 Apr 2015 03:15 PM PDT
Excerpt from dailygalaxy.com
Certain types of supernovae, or exploding stars, are more diverse than previously thought, a University of Arizona-led team of astronomers has discovered. The results, reported in two papers published in the Astrophysical Journal, have implications for big cosmological questions, such as how fast the universe has been expanding since the Big Bang. Most importantly, the findings hint at the possibility that the acceleration of the expansion of the universe might not be quite as fast as textbooks say.
The team, led by UA astronomer Peter A. Milne, discovered that type Ia supernovae, which have been considered so uniform that cosmologists have used them as cosmic "beacons" to plumb the depths of the universe, actually fall into different populations. The findings are analogous to sampling a selection of 100-watt light bulbs at the hardware store and discovering that they vary in brightness.
"We found that the differences are not random, but lead to separating Ia supernovae into two groups, where the group that is in the minority near us are in the majority at large distances -- and thus when the universe was younger," said Milne, an associate astronomer with the UA's Department of Astronomy and Steward Observatory. "There are different populations out there, and they have not been recognized. The big assumption has been that as you go from near to far, type Ia supernovae are the same. That doesn't appear to be the case."
The discovery casts new light on the currently accepted view of the universe expanding at a faster and faster rate, pulled apart by a poorly understood force called dark energy. This view is based on observations that resulted in the 2011 Nobel Prize for Physics awarded to three scientists, including UA alumnus Brian P. Schmidt.
The Nobel laureates discovered independently that many supernovae appeared fainter than predicted because they had moved farther away from Earth than they should have done if the universe expanded at the same rate. This indicated that the rate at which stars and galaxies move away from each other is increasing; in other words, something has been pushing the universe apart faster and faster.
"The idea behind this reasoning," Milne explained, "is that type Ia supernovae happen to be the same brightness -- they all end up pretty similar when they explode. Once people knew why, they started using them as mileposts for the far side of the universe.
"The faraway supernovae should be like the ones nearby because they look like them, but because they're fainter than expected, it led people to conclude they're farther away than expected, and this in turn has led to the conclusion that the universe is expanding faster than it did in the past."
Milne and his co-authors -- Ryan J. Foley of the University of Illinois at Urbana-Champaign, Peter J. Brown at Texas A&M University and Gautham Narayan of the National Optical Astronomy Observatory, or NOAO, in Tucson -- observed a large sample of type Ia supernovae in ultraviolet and visible light. For their study, they combined observations made by the Hubble Space Telescope with those made by NASA's Swift satellite.
The data collected with Swift were crucial because the differences between the populations -- slight shifts toward the red or the blue spectrum -- are subtle in visible light, which had been used to detect type Ia supernovae previously, but became obvious only through Swift's dedicated follow-up observations in the ultraviolet.
"These are great results," said Neil Gehrels, principal investigator of the Swift satellite, who co-authored the first paper. "I am delighted that Swift has provided such important observations, which have been made toward a science goal that is completely independent of the primary mission. It demonstrates the flexibility of our satellite to respond to new phenomena swiftly."
"The realization that there were two groups of type Ia supernovae started with Swift data," Milne said. "Then we went through other datasets to see if we see the same. And we found the trend to be present in all the other datasets.
"As you're going back in time, we see a change in the supernovae population," he added. "The explosion has something different about it, something that doesn't jump out at you when you look at it in optical light, but we see it in the ultraviolet.
"Since nobody realized that before, all these supernovae were thrown in the same barrel. But if you were to look at 10 of them nearby, those 10 are going to be redder on average than a sample of 10 faraway supernovae."
The authors conclude that some of the reported acceleration of the universe can be explained by color differences between the two groups of supernovae, leaving less acceleration than initially reported. This would, in turn, require less dark energy than currently assumed.
That same galaxy in a NASA Swift image below is shown, with bars indicating the location of supernova SN 2011fe. The Swift image is a false-color image with UV emission blue and optical emission red.
"We're proposing that our data suggest there might be less dark energy than textbook knowledge, but we can't put a number on it," Milne said. "Until our paper, the two populations of supernovae were treated as the same population. To get that final answer, you need to do all that work again, separately for the red and for the blue population."
The authors pointed out that more data have to be collected before scientists can understand the impact on current measures of dark energy. Scientists and instruments in Arizona will play important roles in these studies, according to Milne. These include projects led by NOAO; the Large Synoptic Survey Telescope, or LSST, whose primary mirror was produced at the UA; and a camera built by the UA's Imaging Technology Lab for the Super-LOTIS telescope on Kitt Peak southwest of Tucson. Super-LOTIS is a robotic telescope that will use the new camera to follow up on gamma-ray bursts -- the "muzzle flash" of a supernova -- detected by Swift.
Posted: 12 Apr 2015 03:15 PM PDT
Excerpt from earthsky.org
Since 1975, when Hawking showed that black holes evaporate from our universe, physicists have tried to explain what happens to a black hole’s information.
What happens to the information that goes into a black hole? Is it irretrievably lost? Does it gradually or suddenly leak out? Is it stored somehow? Physicists have puzzled for decades over what they call the information loss paradox in black holes. A new study by physicists at University at Buffalo – published in March, 2015 in the journal in Physical Review Letters – shows that information going into a black hole is not lost at all.
Instead, these researchers say, it’s possible for an observer standing outside of a black hole to recover information about what lies within.
Dejan Stojkovic, associate professor of physics at the University at Buffalo, did the research with his student Anshul Saini as co-author. Stojkovic said in a statement:
According to our work, information isn’t lost once it enters a black hole. It doesn’t just disappear.What sort of information are we talking about? In principle, any information drawn into a black hole has an unknown future, according to modern physics. That information could include, for example, the characteristics of the object that formed the black hole to begin with, and characteristics of all matter and energy drawn inside.
Stojkovic says his research “marks a significant step” toward solving the information loss paradox, a problem that has plagued physics for almost 40 years, since Stephen Hawking first proposed that black holes could radiate energy and evaporate over time, disappearing from the universe and taking their information with them.
Disappearing information is a problem for physicists because it’s a violation of quantum mechanics, which states that information must be conserved.
According to modern physics, any information related to an astronaut entering a black hole – for example, height, weight, hair color – may be lost. This notion is known as the ‘information loss paradox’ of black holes because it violates quantum mechanics. Artist’s concept via Nature.
In the 1970s, [Stephen] Hawking proposed that black holes were capable of radiating particles, and that the energy lost through this process would cause the black holes to shrink and eventually disappear. Hawking further concluded that the particles emitted by a black hole would provide no clues about what lay inside, meaning that any information held within a black hole would be completely lost once the entity evaporated.
Though Hawking later said he was wrong and that information could escape from black holes, the subject of whether and how it’s possible to recover information from a black hole has remained a topic of debate.
Stojkovic and Saini’s new paper helps to clarify the story.Stojkovic added:
These correlations were often ignored in related calculations since they were thought to be small and not capable of making a significant difference.
Artist’s impression of a black hole, via Icarus
Bottom line: Since 1975, when Stephen Hawking and Jacob Bekenstein showed that black holes should slowly radiate away energy and ultimately disappear from the universe, physicists have tried to explain what happens to information inside a black hole. Dejan Stojkovic and Anshul Saini, both of University at Buffalo, just published a new study that contains specific calculations showing that information within a black hole is not lost.
Posted: 12 Apr 2015 02:56 PM PDT
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