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Wednesday, May 25, 2011

The Separation of SRB from ET

Hello everyone!

I just got a question from readers on "How long till booster separation" by my Formspring's inbox.

So, here is the answer :

Basically, NASA's space shuttle is consists of Orbiter, External Tank (ET) and Solid Rocket Boosters (SRBs).

I had post a few articles about space shuttle.
  • For more infos about the space shuttle, click here.
  • For more infos about the SRBs, click here.

The launching of the space shuttle needs help from the SRBs as they are solid rockets that provide most of the main force or thrust (71 percent) needed to lift the space shuttle off the launch pad. In addition, the SRBs support the entire weight of the space shuttle orbiter and external fuel tank on the launch pad.

After 2 minutes Space Shuttle is launch from it's launching pad (at T-0) , the SRBs will separates from shuttle (T+2 min).

At T+2min , SRBs separates from the orbiter and external fuel tank at an altitude of 28 miles (45 km). Main engines continue firing.
  1. Parachutes deploy from the SRBs.
  2. SRBs will land in the ocean about 140 miles (225 km) off the coast of Florida.
  3. Ships will recover the SRBs and tow them back to Cape Canaveral for processing and re-use.
This separation occurs after about 2 minutes of burn time of the reusable solid rocket motors, and firing of the booster separation motors takes less than a second. The Space Shuttle Solid Rocket Booster separation rocket motors must be used in conjunction with the release of the motors from the External Tank (ET).

At T +7.7 min - main engines throttled down to keep acceleration below 3g's so that the shuttle does not break apart.

T +8.5 min - main engines shut down.

T +9 min - ET separates from the orbiter. The ET will burn up upon re-entry.

The ET is made of aluminum and aluminum composite materials. It has two separate tanks inside,

  • the forward tank for oxygen
  • and the aft tank for hydrogen, separated by an intertank region.

Each tank has baffles to dampen the motion of fluid inside. Fluid flows from each tank through a 17-inch (43 cm) diameter feed line out of the ET through an umbilical line into the shuttle's main engines. Through these lines, oxygen can flow at a maximum rate of 17,600 gallons/min (66,600 l/min) and hydrogen can flow at a maximum rate of 47,400 gallons/min (179,000 l/min).

The ET is covered with a 1-inch (2.5 cm) thick layer of spray-on, polyisocyanurate foam insulation. The insulation keeps

  • the fuels cold,
  • protects the fuel from heat that builds up on the ET skin in flight,
  • and minimizes ice formation.
When Columbia launched in 2003, pieces of the insulating foam broke off the ET and damaged the left wing of the orbiter, which ultimately caused Columbia to break up upon re-entry.

T +10.5 min - OMS engines fire to place you in a low orbit.

T +45 min - OMS engines fire again to place you in a higher, circular orbit (about 250 miles/400 km).

Ok, this is a summarize form on how actually the space shuttle is launced. Now, I have a question for you. If you had read about the space shuttle before, you may answer my simple question ;).

Which of these shuttle's components (ET, SRBs and Orbiter) is not reusable?

If you knew the answer, let me know. =]

Tuesday, March 15, 2011

Earthquake at Japan have moved Earth's axis and shortened days

The March 11, magnitude 9.0 earthquake in Japan may have shortened the length of each Earth day and shifted its axis. But don't worry—you won't notice the difference.

Using a United States Geological Survey estimate for how the fault responsible for the earthquake slipped, research scientist Richard Gross of NASA's Jet Propulsion Laboratory, Pasadena, Calif., applied a complex model to perform a preliminary theoretical calculation of how the Japan earthquake—the fifth largest since 1900—affected Earth's rotation. His calculations indicate that by changing the distribution of Earth's mass, the Japanese earthquake should have caused Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds (a microsecond is one millionth of a second).

The calculations also show the Japan quake should have shifted the position of Earth's figure axis (the axis about which Earth's mass is balanced) by about 17 centimeters (6.5 inches), towards 133 degrees east longitude. Earth's figure axis should not be confused with its north-south axis; they are offset by about 10 meters (about 33 feet). This shift in Earth's figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth's axis in space—only external forces such as the gravitational attraction of the sun, moon and planets can do that.

Both calculations will likely change as data on the quake are further refined.

In comparison, following last year's magnitude 8.8 earthquake in Chile, Gross estimated the Chile quake should have shortened the length of day by about 1.26 microseconds and shifted Earth's figure axis by about 8 centimeters (3 inches). A similar calculation performed after the 2004 magnitude 9.1 Sumatran earthquake revealed it should have shortened the length of day by 6.8 microseconds and shifted Earth's figure axis by about 7 centimeters, or 2.76 inches. How an individual earthquake affects Earth's rotation depends on its size (magnitude), location and the details of how the fault slipped.

Gross said that, in theory, anything that redistributes Earth's mass will change Earth's rotation.

"Earth's rotation changes all the time as a result of not only earthquakes, but also the much larger effects of changes in atmospheric winds and oceanic currents," he said. "Over the course of a year, the length of the day increases and decreases by about a millisecond, or about 550 times larger than the change caused by the Japanese earthquake. The position of Earth's figure axis also changes all the time, by about 1 meter (3.3 feet) over the course of a year, or about six times more than the change that should have been caused by the Japan quake."

Gross said that while we can measure the effects of the atmosphere and ocean on Earth's rotation, the effects of earthquakes, at least up until now, have been too small to measure. The computed change in the length of day caused by earthquakes is much smaller than the accuracy with which scientists can currently measure changes in the length of the day. However, since the position of the figure axis can be measured to an accuracy of about 5 centimeters (2 inches), the estimated 17-centimeter shift in the figure axis from the Japan quake may actually be large enough to observe if scientists can adequately remove the larger effects of the atmosphere and ocean from the Earth rotation measurements. He and other scientists will be investigating this as more data become available.

Gross said the changes in Earth's rotation and figure axis caused by earthquakes should not have any impacts on our daily lives. "These changes in Earth's rotation are perfectly natural and happen all the time," he said. "People shouldn't worry about them."

Source : NASA

Tuesday, March 8, 2011

NASA scientists in row over 'alien microbes'

WASHINGTON (AFP) - – Top NASA scientists said there was no scientific evidence to support a colleague's claim that fossils of alien microbes born in outer space had been found in meteorites on Earth.

The US space agency formally distanced itself from the paper by NASA scientist Richard Hoover, whose findings were published Friday in the peer-reviewed Journal of Cosmology, which is available free online.

"That is a claim that Mr Hoover has been making for some years," said Carl Pilcher, director of NASA's Astrobiology Institute.

"I am not aware of any support from other meteorite researchers for this rather extraordinary claim that this evidence of microbes was present in the meteorite before the meteorite arrived on Earth and and was not the result of contamination after the meteorite arrived on Earth," he told AFP.

"The simplest explanation is that there are microbes in the meteorites; they are Earth microbes. In other words, they are contamination."

Pilcher said the meteorites that Hoover studied fell to Earth 100 to 200 years ago and have been heavily handled by humans, "so you would expect to find microbes in these meteorites."

Paul Hertz, chief scientist of NASA's Science Mission Directorate in Washington, also issued a statement saying NASA did not support Hoover's findings.

"While we value the free exchange of ideas, data and information as part of scientific and technical inquiry, NASA cannot stand behind or support a scientific claim unless it has been peer-reviewed or thoroughly examined by other qualified experts," Hertz said.

"NASA also was unaware of the recent submission of the paper to the Journal of Cosmology or of the paper's subsequent publication."

He noted that the paper did not complete the peer-review process after being submitted in 2007 to the International Journal of Astrobiology.

According to the study, Hoover sliced open fragments of several types of carbonaceous chondrite meteorites, which can contain relatively high levels of water and organic materials, and looked inside with a powerful microscope, Field Emission Scanning Electron Microscopy (FESEM).

He found bacteria-like creatures, calling them "indigenous fossils" that originated beyond Earth and were not introduced here after the meteorites landed.

Hoover "concludes these fossilized bacteria are not Earthly contaminants but are the fossilized remains of living organisms which lived in the parent bodies of these meteors, e.g. comets, moons and other astral bodies," said the study.

"The implications are that life is everywhere, and that life on Earth may have come from other planets."

The journal's editor-in-chief, Rudy Schild of the Harvard-Smithsonian Center for Astrophysics, hailed Hoover as a "highly respected scientist and astrobiologist with a prestigious record of accomplishment at NASA."

The publication invited experts to weigh in on Hoover's claim, and both sceptics and supporters began publishing their commentaries on the journal's website Monday.

"While the evidence clearly indicates that the meteorites was eons ago populated with bacterial life, whether the meteorites are of actual extra-terrestrial origin might debatable," wrote Patrick Godon of Villanova University in Pennsylvania.

Michael Engel of the University of Oklahoma wrote: "Given the importance of this finding, it is essential to continue to seek new criteria more robust than visual similarity to clarify the origin(s) of these remarkable structures."

The journal did not immediately respond to requests for comment.

Pilcher described Hoover as a "NASA employee" who works in a solar physics branch of a NASA lab in the southeastern state of Alabama.

"He clearly does some very interesting microscopy. The actual measurements on these meteorites are very nice measurements, but I am not aware of any other qualification that Mr Hoover has in analysis of meteorites or in astrobiology," Pilcher said.

A NASA-funded study in December suggested that a previously unknown form of bacterium, found deep in a California lake, could thrive on arsenic, adding a new element to what scientists have long considered the six building blocks of life.

That study drew hefty criticism, particularly after NASA touted the announcement as evidence of extraterrestrial life. Scientists are currently attempting to replicate those findings.

source : Yahoo! News

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