Discovery Launch on Track, NASA Says

Space shuttle Discovery got the green light to launch next week, but the vote was not unanimous.

NASA managers spent hours Tuesday debating whether to liftoff. It was all part of a standard flight review, but this one was different. Some safety workers recommended rolling Discovery back to the vehicle assembly building to replace three heat protection panels that have weakened.

NASA's chief engineer said that was enough to vote against launching. But overall, mission managers say the risk is not high enough to warrant a delay.

Liftoff is now set for next Tuesday at 11:38 in the morning. Keep it here on News 13 for continuing coverage.

NASA's senior managers cleared space shuttle Discovery for liftoff Tuesday, overruling a safety group that called for further studies and wing repairs, if necessary, before next week's launch.

The potential problem is with the critical thermal shielding on Discovery's wings. A new inspection method uncovered possible cracking just beneath the protective coating on three of the 44 panels that line the wings.

Engineers were evenly split on whether Discovery's flight to the international space station should be delayed, shuttle program manager Wayne Hale said. In the end, top managers concluded Tuesday night following an all-day meeting that repairs were not needed.

"There was a great deal of evidence presented today and the preponderance of evidence in my mind says that we have an acceptable risk to go fly. And let me make sure you understand that. I didn't say it's safe to go fly and I wouldn't say that. We have an acceptable risk to go fly," Hale said at a news conference.

The NASA Engineering and Safety Center - formed in the wake of the 2003 Columbia disaster - has been studying the issue since May and still does not understand why the protective coating on some of the wing panels is coming off.

It recommended additional testing, at the very least, before Discovery flies and favored replacing the three reinforced carbon panels in question. That work would have set the launch back by at least two months.

Columbia was destroyed during re-entry because of a hole in its wing.

Hale said part of what gave him confidence to proceed with the launch was the fact that two similar cases in orbit ended up being benign and the astronauts will have a repair kit in orbit for mending small damage.

In addition, "it appears that there is good analysis that says we could survive even if the worst thing happens to us during entry," he said.

The worst that could happen, said Ralph Roe, the safety center's director, is that some of the coating is lost off the front of a wing panel right before re-entry and the hot atmospheric gases burn through the entire panel.

Roe said his safety center could not get comfortable with all the uncertainties about whether the coating problem might worsen in space. The three panels in question on Discovery do not appear to have worsened over the past three flights, despite indications of possible cracks to the coating.

Engineers will continue to work to understand what is going on. "If the risk grows to an unacceptable level, we will take action," Hale said.

Unlike the sometimes brusque and hasty flight readiness reviews before the Columbia accident, "everybody got to ask questions, everybody got to give their understanding of it down to the working troop level," Hale said.

On the Net:

• NASA: http://spaceflight.nasa.gov

Technorati : NASA

Nano-Science and Technology in the International Technology Roadmap for Semiconductors

source :The International Technology Roadmap for Semiconductors (ITRS) continues to provide the most up to date view into the semiconductor industries technology requirements and potential solutions for those requirements.(1) As noted several years ago by Dan Hutcheson, the feature sizes for today's devices and interconnects placed the integrated circuit well into the world of Nanotechnology.(2) As ITRS states, the semiconductor industry will squeeze all the performance out of existing CMOS transistor technology in an effort to extend it for as long as possible. The ITRS teams are also looking into the future beyond CMOS. Nano Science and Technology pay critical roles in both CMOS extension and in "Beyond CMOS". The 2007 ITRS will have sections on both Emerging Research Materials and Emerging Research Devices. These sections describe potential new device technology and some of the materials that are being researched for use in these devices. In addition, the ITRS Metrology Roadmap has a section on measurement needs and methods for Emerging Research Materials and Devices.

The industry search for a new device to replace or augment the transistor requires significant amounts of research and development in universities, national laboratories, and industry itself. Some of the concepts being explored include using spin transport instead of charge transport, molecular electronics where changes in molecular configuration govern charge transport, excitonic devices. New materials such as graphene, carbon nanotubes, semiconductor nanowires, metal oxides, and quantum dots are under consideration as the materials that would be used to fabricate the device.

Underpinning both CMOS extension and beyond CMOS devices are new phenomena that manifest themselves only when materials are fabricated into nano-scale dimensions. As one can glean from experienced semiconductor technologists, shrinking dimensions has always brought on both new performance and new problems. Everything from materials strength to quantum confinement impact properties at nanoscale dimensions. In addition, the measurement process itself is subject to new physics at these length scales.

There are countless challenges facing characterization and metrology of nano-scale materials and devices. All areas from microscopy to spectroscopy must be advanced at a more rapid pace. Although improvements in microscopy, such as aberration corrected lens systems, have continued at unprecedented rates, electron microscopy of soft materials such as graphene and molecular electronics remain exceedingly difficult. The combination of experiment and modeling are required to accelerate progress. For example, simulation of TEM images both improve image interpretation and point to optimum imaging conditions. Theory is also necessary for interpretation of electron energy loss spectra. The ITRS is calling for measurements such as carrier spin with presently unachievable spatial localization of the information. Scanned probe methods including BEEM (ballistic electron emission microscopy)are providing new insights into materials properties such as spin transport. Recent work shows that nanoscale phenomena on optical properties such as quantum confinement provide a means of extending optical methods to smaller dimensions.(3) Measurements the detect defects in nanostructures such as graphene and correlate them to resultant properties are very important. Recent work at the National Institute of Standards and Technology showed how scanning tunneling microscopy can observed such phenomena.(4)

Another set of measurement needs is for uniformity of properties of nanoscale materials. For example, what is the average and range of the dimensions of an assembly of nanodots? Numerous properties need to be characterized for such arrays. How does one measure this uniformity at the precision required for volume manufacturing control? The semiconductor industry has faced these issue for many years.

So in December when the 2007 ITRS is released, the Emerging Research Materials, Emerging Research Devices, Metrology, and other sections of the ITRS will provide us with a very useful overview of how important the semiconductor industry finds Nano-Scale Science and Technology.

1. International Technology Roadmap for Semiconductors WEB-Site http://www.itrs.net

2. G. Dan Hutcheson. The first nanochips. Scientific American, pages 48-55, April 2004.

source

http://www.nanotech-now.com/columns/?article=124

Technorati : Nano-Science