Friday, September 30, 2011

World's Best Place to Launch a Satellite


The best place to launch a satellite into geostationary orbit is from a launch site near the equator, to take advantage of the rotation of the Earth. But satellites are also launched from the equator into other orbits.
A geostationary orbit is about 36,000 kilometres from the surface of the Earth. In it, a satellite appears to hover over a fixed point on Earth, a location ideal for communications satellites and for some Earth observation satellites.

The easiest way to attain the right speed for orbiting a geostationary satellite is to launch it along the equator in the direction of the Earth’s rotation. The launcher then gets a boost from the Earth which, at the equator, moves at a speed of 1675 kilometres per hour. Thus the rocket can do its job with less propellant.

Space on board a launcher is limited. The load carried divides between the useful payload (satellites) and the propellant. The greater the payload capacity, the lower the cost for orbiting each satellite. First, the launcher orients itself in the satellite’s orbit, and then it releases the satellite. Thereafter, the satellite stays in its orbit, which it can adjust as needed using small on-board thrusters.

French Guyana is a good site for launching satellites into the equatorial plane. Here, ESA’s powerful Ariane 5 rockets are launched. The Ariane 5 has a load capacity of up to eight tons, enough to orbit the heaviest satellites.

Other orbits
If a satellite is to be launched into a polar orbit (orbiting pole to pole, instead of around the equator), its launch rocket gets little or no help from the Earth’s rotation. In theory, such a satellite may be launched from anywhere on Earth. But a rocket launch base is expensive, so it’s actually cheaper to have a base at the equator to meet all launch needs.

French Guyana is vital for the European space industry, and its launch area is called "the spaceport".


Sunday, September 25, 2011

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Wednesday, September 21, 2011

How to Quit Smoking? World's Best Advice For Teen Age Boys


For teenagers struggling to quit smoking, a new study has some advice. To break the habit, try breaking a sweat.
It showed that teenage boys who took part in a smoking cessation program and combined it with exercise were several times less likely to continue smoking than those who received only traditional anti-smoking advice. Exercise did not have a comparable effect on teenage girls; researchers aren’t sure why. But the research is among the first to show that an exercise plan for teenage smokers can help them kick two bad habits at once, smoking and inactivity, which often go hand in hand.
For young smokers, breaking the habit before adulthood can be particularly crucial. Studies show that starting as a teenager makes it much more difficult to quit later on. About 80 percent of adult smokers began their habit before turning 18. Yet every day, 3,500 teenagers light their first cigarette.
The new study, published this week in the journal Pediatrics, took place in a state with one of the worst teen tobacco problems, West Virginia, where roughly a third of all high school students are smokers. Previous studies have shown that in adults, exercise — even if it’s just a walk around the block or lifting some weights — can help curb smoking by easing withdrawal symptomsand controlling cravings when people are confronted with cigarettes and other strong cues. Since West Virginia also suffers high rates of teenage obesity, the researchers wanted to see what effect exercise could have in combating two major health threats.
“It seemed logical to address these two together,” said Kimberly Horn, a professor of community medicine at West Virginia University and the lead author of the paper. “Exercise is known to mediate factors that often co-occur with smoking cessation, like increased stress levels, weight gain, withdrawal and cravings.”
To find out, the researchers recruited 233 smokers ages 14 to 19 at West Virginia high schools, and randomly assigned each to one of three groups. Some students received a single smoking-cessation session. A second group went through a 10-week anti-smoking program called Not on Tobacco, or NOT. And those in the third group went through the NOT program and were given pedometers and counseling on starting an exercise plan, which they could then schedule on their own time.
After three months, the study found that only 5 percent of the students who got the single anti-smoking session had quit smoking. But almost twice as many who went through the 10-week program had quit. When exercise was added to the mix, the effect on boys was remarkable: 24 percent of male students in the exercise group quit smoking, while only about 8 percent in the 10-week program that did not encourage exercise had stopped. They were also more likely to have stayed away from cigarettes after six months as well. The teenage girls in the exercise group, though, were no more likely to have quit smoking than those who received only counseling on quitting smoking.
“The kids in this study were pretty hard-core smokers,” Dr. Horn said. “They smoked about a half pack a day during the week and up to a pack a day on weekends. They were pretty addicted, and most started when they were about 11 years old.”
The data did not explain why a gender divide would exist, but Dr. Horn speculated that a few things could be responsible. Teenage boys are generally more enthusiastic about engaging in vigorous exercise, and are “more confident in their ability to be physically active,” Dr. Horn said, while physical activity levels typically plummet as teenage girls get older.
“It’s puzzling to us; it was a surprise finding,” she said. “I think we also need to look at issues of self-confidence. It could be the girls started with some stronger fitness barriers to overcome than boys.”
Nonetheless, the results over all were encouraging, since getting teenagers to give up smoking — or change any potentially harmful habits — can be notoriously difficult.
“One of the important things to point out is that oftentimes people believe that kids aren’t interested in quitting smoking,” she said. “I think this demonstrates that kids can quit, they’re interested in quitting and they can be successful, given the right tools.”