Next Generation Supersonic Passenger Aircraft

The 21st century will become the age of supersonic passenger aircraft.



Sooner or later, travelers will use supersonic passenger jets just as they use the jumbo jets of today. What can we do to make this happen sooner?


This article introduces the research now underway at JAXA to make supersonic travel a new option for the commercial traveler.
 
If we travel faster than sound, we'll get to where we're going sooner.
Large passenger aircrafts such as the B (Boeing) 747, what we fondly call "jumbo jets," take us to destinations all over Japan and the rest of the world. Though fast and convenient, jumbo jets still take many hours to reach distant lands such as the United States and Europe. Travelers have no choice but to sit and wait, with nowhere to move their bodies. If we could fly at much higher speeds, the hours of in-flight confinement would be drastically reduced. Flying would be far more convenient and comfortable.

But engineers run into problems when they try to design aircrafts that travel faster than sound. The jumbo jets today normally fly slightly slower than the speed of sound. If an aircraft flew faster than sound, the shock waves from the aircraft would reach the ground and cause strong noises like thunder called a "sonic boom". The sonic boom by an aircraft as big as a jumbo jet would have enough power to cause damage on the ground. The windows of buildings might even shatter.

Some people say that we don't need to develop the speed of airliners, which is now fast enough. But flying at higher speeds has various advantages besides those we've already described. One, for example, is the possibility of reducing the incidence of "Economy-class syndrome." Economy-class syndrome is a perilous physical condition caused by sitting for long hours in the same posture in an airline seat. Victims suffer a blood clot in their legs and often have difficulty breathing. If the clot moves higher in the bloodstream, into the lungs or heart, death may even result. The name of the syndrome is actually misleading, as passengers in business class and first class sometimes experience the same thing. Airplane passengers can reduce the risk of economy-class syndrome simply by standing up and stretching their legs every few hours. Even so, shorter flying times might eliminate the risks altogether.
 
Article from JAXA.
Hillary Maruwa Jan 29, 2010

Does Hot water cools faster than Cold water?

Determining whether or not hot water can freeze faster than cold water may seem like a no-brainer. After all, water freezes at 0 degrees Celsius. And wouldn’t water hot enough to kill E. coli bacteria (about 120 degrees Fahrenheit or 50 degrees Celsius) take a longer path than cooler water at a fall New England beach (about 60 degrees Fahrenheit or 15 degrees Celsius) towards a frigid future as ice? While a logical assumption, it turns out that hot water can freeze before cooler water under certain conditions.

This apparent quirk of nature is the "Mpemba effect," named after the Tanzanian high school student, Erasto Mpemba, who first observed it in 1963. The Mpemba effect occurs when two bodies of water with different temperatures are exposed to the same subzero surroundings and the hotter water freezes first. Mpemba’s observations confirmed the hunches of some of history’s most revered thinkers, such as Aristotle, Rene Descartes and Francis Bacon, who also thought that hot water froze faster than cold water.

Evaporation is the strongest candidate to explain the Mpemba effect. As hot water placed in an open container begins to cool, the overall mass decreases as some of the water evaporates. With less water to freeze, the process can take less time. But this doesn’t always work, especially when using closed containers that preventevaporated water from escaping.

And evaporation may not be the only reason the water can freeze more quickly. There may be less dissolved gas in the warmer water, which can reduce its ability to conduct heat, allowing it to cool faster. However, Polish physicists in the 1980s were unable to conclusively demonstrate this relationship.

A non-uniform temperature distribution in the water may also explain the Mpemba effect. Hot water rises to the top of a container before it escapes, displacing the cold water beneath it and creating a "hot top." This movement of hot water up and cold water down is called a convection current. These currents are a popular form of heat transfer in liquids and gases, occurring in the ocean and also in radiators that warm a chilly room. With the cooler water at the bottom, this uneven temperature distribution creates convection currents that accelerate the cooling process. Even with more ground to cover to freeze, the temperature of the hotter water can drop at a faster rate than the cooler water.

So the next time you refill your ice cube tray, try using warmer water. You might have ice cubes to cool your drink even sooner

From Live Science.

Hillary Maruwa Jan. 15, 2010

Half plant, half animal - Sea Slug.

A green sea slug appears to be part animal, part plant. It's the first critter discovered to produce the plant pigment chlorophyll.

The sneaky slugs seem to have stolen the genes that enable this skill from algae that they've eaten. With their contraband genes, the slugs can carry out Photosynthesis - the process plants use to convert sunlight into energy.

"They can make their energy-containing molecules without having to eat anything," said Sidney Pierce, a biologist at the University of South Florida in Tampa.

Pierce has been studying the unique creatures, officially called Elysia chlorotica, for about 20 years. He presented his most recent findings in Jan. 7 at the annual meeting of the Society for Integrative and Comparative Biology in Seattle. The finding was first reported by Science News.

"This is the first time that multicellar animals have been able to produce chlorophyll," Pierce told Live Science.

The sea slugs live in salt marshes in New England and Canada. In addition to burglarizing the genes needed to make the green pigment chlorophyll to convert sunlight into energy, just as plants do, eliminating the need to eat food to gain energy.

"We collect them and we keep them in aquarium for months," Pierce said. "As long as we shine a light on them for 12 hours a day, they can survive [without food]."

The researchers used a radioactive tracer to be sure that the slugs are actually producing the chlorophyll themselves, as opposed to just stealing the ready-made pigment from algae. In fact, the slugs incorporate the genetic material so well, they pass it on to further generations of slugs.

The babies of thieving slugs retain the ability to produce their own chlorophyll, though they can't carry out photosynthesis until they've eaten enough algae to steal the necessary chloroplasts, which they can't yet produce on their own.

The slugs accomplishment is quite a feat, and scientists aren't yet sure how the animals actually appropriate the genes they need.

"It certainly is possible that DNA from one species can get into another species, as these slugs have clearly shown," Pierce said. "But the mechanisms are still unknown."

Article from Live Science.

Hillary Maruwa Jan. 14, 2010.