New year's mission at NASA: repair new cracks on Discovery fuel tank - Christian Science Monitor

Newly discovered cracks in the space shuttle Discovery's external fuel tank will keep repair crews busy into the New Year's weekend as NASA eyes a Feb. 3 launch for the orbiter and its six-member crew.

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The small cracks, uncovered Thursday as technicians used X-ray devices to inspect the external tank, represent the latest bump along the road to launch. The cracks were found following a chain of inspections, repairs, and more inspections dating back to Discovery's scrubbed Nov. 5 liftoff.

That liftoff was canceled after unacceptably high levels of explosive hydrogen were detected outside a crucial fixture on the side of the tank. The fixture transfers excess gas that accumulates as the tank fills to a line that carries the hydrogen to a flare stack, where the excess gas is burned.

IN PICTURES: NASA's Space Shuttle

When technicians returned to the launching pad after the liquid hydrogen and liquid oxygen tanks had been emptied, they noticed cracks in the external tank's foam insulation at one of 108 "stringers" – long U-shaped aluminum ribs that reinforce a section of the tank's outer shell. This section, toward the top of the tank, spans a gap between the hydrogen and oxygen tanks inside.

Once technicians removed the cracked segment foam in anticipation of repairing it, they found that the stringer beneath the foam had cracked, too – shifting enough to fracture the foam. Subsequent inspections showed that a second, adjacent stringer hosted a small crack as well.

Although these cracks have appeared in past tanks and were successfully repaired, this incident was unusual because in the past, the cracks were caught far earlier in the shuttle program's inspection process, mission managers say.

As a result, they wanted to take the time needed to review the inspections on this tank to make sure the process hadn't broken down. And if it hadn't, they wanted to get a clear grasp of the causes that would trigger cracks at the last minute.

The problem appeared on the side of the tank facing the underside of the orbiter, where the shuttle's heat-shedding tiles and carbon-composite edged to the wings could be vulnerable to damage if a piece of foam broke loose and struck them.

In 2003, the shuttle Columbia broke up on reentry, killing its seven-member crew – an accident traced to chunks of foam striking the orbiter's thermal-protection system during ascent.

In this case, technicians were able to repair the stringers on the pad. On Dec. 15, controllers refilled the external tank to see if the repairs held up to the expansion and contraction the tank experiences as it undergoes the extreme temperature changes presented by ultra-cold liquid hydrogen and liquid oxygen.

But managers were uncertain if the problem extended to additional stringers on sides of the tank workers can't reach while the shuttle is on the pad. So on Dec. 21, Discovery headed back to the towering Vehicle Assembly Building for additional inspections.

The cracks technicians uncovered Thursday appeared to vindicate the decision to send Discovery back to the barn for an additional look. Officials say they could decide on Jan. 3 whether to return the orbiter to the pad after weekend repairs or keep Discovery in the Vehicle Assembly Building for additional modifications to the tank.

IN PICTURES: NASA's Space Shuttle

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'Ice volcano' identified on Titan - BBC News

14 December 2010 Last updated at 20:20 ET By Jonathan Amos Science correspondent, BBC News, San Francisco In this false colour image, greens denote volcanic material and blues are believed to be sands Scientists think they now have the best evidence yet for an ice volcano on Titan, the largest moon of Saturn.

The Cassini probe has spotted a 1,500m-high mountain with a deep pit in it, and what looks like a flow of material on the surrounding surface.

The new feature, which has been dubbed "The Rose", was seen with the probe's radar and infrared instruments.

Titan has long been speculated to have cryovolcanoes but its hazy atmosphere makes all observations very difficult.

Researchers are now wondering how active this mountain might be, and what sort of lava it could spew.

"Much of Titan's outer material is water-ice and ammonia, and so that's certainly one possible material that could melt at low temperatures and flow on the surface," explained Dr Randy Kirk, a Cassini radar team-member from the US Geological Survey (USGS).

"But there's a lot of organic material in the atmosphere, and deposited from the atmosphere, and maybe coming up from the interior in the form of these volcanoes. [This material could be] waxy or even plasticy," he told BBC News.

Dr Kirk was speaking here at the American Geophysical Union (AGU) Fall Meeting, the largest gathering of Earth scientists in the world.

There have been previous claims for ice volcanoes at Titan, but these have never won universal support. Scientists have continued to look however because it is considered an excellent candidate given its frigid conditions: the surface temperature is about minus 180 Celsius.

Dr Kirk and colleagues hope their new data will convince even their sternest critics that a positive identification has now finally been made.

The putative volcano is sited just south of Titan's equator in a sea of sand dunes referred to as Sotra Facula.

Titan's thick haze makes all observations at the moon extremely difficult

The radar instrument on Cassini is able to see through the moon's haze and establish the local topography - scientists can build a 3D model of the ground. The infrared instrument on the probe, on the other hand, can gather some information on the variation in composition of the surface materials. Taken together, Dr Kirk's team says, the two views put forward a compelling case.

"We've seen a mountain that has a crater in, that flows of material coming out and spreading across the surface at some time in the past; and in fact when we looked in more detail in 3D we found that there was more than one volcano in this area. And that's actually very common in volcanic areas of the Earth and other planets."

Jeffrey Kargel, a planetary scientist at the University of Arizona, Tucson, is not connected with the Cassini mission. He told the meeting The Rose was the most likely volcano he had yet seen on Titan.

He said that if the lavas were rich in hydrocarbons, they could have the look of softened asphalt, candle wax or even polyethylene.

"There are many unanswered questions and intriguing possibilities," he told reporters.

"Is Sotra the source of Titan's atmospheric methane? Is cryovolcanism still active at Sotra or elsewhere on Titan? What is the cryovolcanic substance? Is cryovolcanism there explosive or quietly effusive? Might cryo-lavas have dredged up indications of fossils or chemical remains of sub-surface life?"

The Cassini-Huygens mission is a co-operative project of Nasa, the European Space Agency (Esa) and the Italian space agency (Asi).

Jonathan.Amos-INTERNET@bbc.co.uk

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Google's Chrome OS: What Is It Good For? - BusinessWeek

By Om Malik

If Google expected a warm welcome for its Chrome OS and the new Cr-48 laptops it's currently giving away to select beta testers, it was wrong. The hardware has received a reception colder than Scrooge's heart. Folks at TechCrunch have given it a verbal lashing that would make a drill sergeant proud. For that past three days, I've been using the Cr-48. Here are my impressions.

The hardware:The boot-up is extremely fast and the log-on process is smooth and speedy, so long as one has a Google Mail account. (Google Apps ID doesn't quite work.) The screen is great, but the graphic capabilities are pretty limited. There is a single USB port and a flash memory card slot; frankly, having lived with the old MacBook Air with a single USB port, I don't see much of a problem. The trackpad is awful. I love the dedicated Search button and would love to see it on all computers. The laptop picked up most of the commonly used USB peripherals. Both a Logitech mouse and a Microsoft optical mouse worked just fine, without need for special discovery or driver installs.

The User Interface/Experience: The Interface is rough around the edges; what you see is essentially the Chrome Web browser. It takes too many cues from Microsoft Windows, which is understandable, considering that they are going after the mainstream and enterprise markets. The OS needs better font support and reminds me of some early Linux distributions. The user experience expects us to come to the idea of using browser tabs instead of apps—a weird notion, but not so strange if you have used the Chrome browser as your primary browser and are accustomed to cloud-based services. If you use Google Chat and Google Tasks, then you easily understand the idea of "Panels," a new feature inside Chrome OS that runs in small, easy-to-access panes at the bottom right of the browser. Even the best Web apps currently available at the Chrome Web Store are works-in-progress. The biggest challenge for Google's Chrome OS is going to be fighting against the many lifelong habits people have developed using a desktop OS.

The Cloud-Based Services: Despite being severely underpowered, one thing the device does very well is to let you use Google apps—especially Google Docs, Gmail, and other cloud services (from Google)—without problems. The YouTube experience is marginal at best. Netflix doesn't work. Most of your browser-based apps will work, but Adobe Flash on Chrome OS is like watching a toddler learn to crawl. It will be a long time before it reaches the maturity of Adobe on the Windows platform. Adobe has already stated that it plans to improve its integrated Flash performance in Chrome OS, essentially calling it a "work-in-progress."

Bottom line: Will I use Cr-48 or something like it as my primary computer? It would be tough for me to make Chrome OS my primary computing experience. I have a lifelong habit of using a full desktop operating system. That doesn't mean I won't keep an open mind, but for now it's a no-go for me. My more portable, 2.13 GHz MacBook Air is the machine I like. Even as I spend a lot of time inside the browser, I prefer a desktop with the Chrome browser and raw power. Plus my Mac has Silverlight, which lets me play Netflix and use third-party, native apps such as Reeder.

As Google stated very clearly, this particular device isn't going to be sold in the market; the company's partners are going to make the devices that consumers can buy. I hope they do a better job and come up with more attractive hardware.

The real story to focus on is the Chrome OS, what it really means, and whom it targets.

Google's growth has coincided with the shift to the Web. Google is a company that has been a believer in networked computing from its inception. Since 2004 an increasing amount of our focus and attention has been devoted to the browser and what we can do inside it. The so-called Web 2.0 concept helped enhance the inside-the-browser experience, slowly replacing the desktop as our primary focus of attention.

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