The Dream Moves Closer

Image above: Sierra Nevada Corp. (SNC) Space Systems' Dream Chaser engineering test article before its 2012 captive-carry test. Image credit: SNC

Sierra Nevada Corporation’s (SNC) Space Systems Dream Chaser flight vehicle arrived at NASA’s Dryden Flight Research Center in Edwards, Calif., Wednesday to begin tests of its flight and runway landing systems.

The tests are part of pre-negotiated, paid-for-performance milestones with NASA’s Commercial Crew Program (CCP), which is facilitating U.S.-led companies’ development of spacecraft and rockets that can launch from American soil. The overall goal of CCP is to achieve safe, reliable and cost-effective U.S. human access to and from the International Space Station and low-Earth orbit.

Tests at Dryden will include tow, captive-carry and free-flight tests of the Dream Chaser. A truck will tow the craft down a runway to validate performance of the nose strut, brakes and tires. The captive-carry flights will further examine the loads it will encounter during flight as it is carried by an Erickson Skycrane helicopter. The free flight later this year will test Dream Chaser’s aerodynamics through landing.

Meanwhile, on the east coast, several NASA astronauts will be at the agency’s Langley Research Center in Hampton, Va., this week to fly simulations of a Dream Chaser approach and landing to help evaluate the spacecraft’s subsonic handling. The test will measure how well the spacecraft would handle in a number of different atmospheric conditions and assess its guidance and navigation performance.

“Unique public-private partnerships like the one between NASA and Sierra Nevada Corporation are creating an industry capable of building the next generation of rockets and spacecraft that will carry U.S. astronauts to the scientific proving ground of low-Earth orbit,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations in Washington. “NASA centers around the country paved the way for 50 years of American human spaceflight, and they’re actively working with our partners to test innovative commercial space systems that will continue to ensure American leadership in exploration and discovery.”

The Dream Chaser Space System is based on Langley’s Horizontal Lander HL-20 lifting body design concept. The design builds on years of analysis and wind tunnel testing by Langley engineers during the 1980s and 1990s. Langley and SNC joined forces six years ago to update the HL-20 design in the Dream Chaser orbital crew vehicle. In those years, SNC worked with the center to refine the spacecraft design. SNC will continue to test models in Langley wind tunnels. Langley researchers also helped develop a cockpit simulator at SNC’s facility in Louisville, Colo., and the flight simulations being assessed at the center.

NASA is partnered with SNC, Space Exploration Technologies (SpaceX) and The Boeing Company to meet CCP milestones for integrated crew transportation systems under the Commercial Crew Integrated Capability (CCiCap) initiative. Advances made by these companies under their funded Space Act Agreements ultimately are intended to lead to the availability of commercial human spaceflight services for government and commercial companies.

Image above: This is an artist's concept of SNC's Dream Chaser Space System. Image credit: NASA

While NASA works with U.S. industry partners to develop commercial spaceflight capabilities, the agency also is developing the Orion spacecraft and the Space Launch System (SLS), a crew capsule and heavy-lift rocket to provide an entirely new capability for human exploration. Designed to be flexible for launching spacecraft for crew and cargo missions, SLS and Orion will expand human presence beyond low-Earth orbit and enable new missions of exploration in the solar system.

 

 

 

Glaciers and Sea Level Rise

The Aletsch Glacier in Switzerland is the largest valley glacier in the Alps and it has been losing mass since the mid-19th century. A new study using data from two NASA satellites found that glaciers like this one lost an average of 571 trillion pounds of ice per year from 2003 to 2009, which contributed to about 30 percent of the total observed global sea level rise during the same period. Credit: Frank Paul, University of Zurich.

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A new study of glaciers worldwide using observations from two NASA satellites has helped resolve differences in estimates of how fast glaciers are disappearing and contributing to sea level rise.

The new research found glaciers outside of the Greenland and Antarctic ice sheets, repositories of 1 percent of all land ice, lost an average of 571 trillion pounds (259 trillion kilograms) of mass every year during the six-year study period, making the oceans rise 0.03 inches (0.7 mm) per year. This is equal to about 30 percent of the total observed global sea level rise during the same period and matches the combined contribution to sea level from the Greenland and Antarctica ice sheets.

The study compares traditional ground measurements to satellite data from NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) and Gravity Recovery and Climate Experiment (GRACE) missions to estimate ice loss for glaciers in all regions of the planet. The study period spans 2003 to 2009, the years when the two missions overlapped.

“For the first time, we have been able to very precisely constrain how much these glaciers as a whole are contributing to sea level rise,” said Alex Gardner, Earth scientist at Clark University in Worcester, Mass., and lead author of the study. “These smaller ice bodies are currently losing about as much mass as the ice sheets.”

 

 

 

 

The study was published Thursday in the journal Science.

ICESat, which stopped operating in 2009, measured glacier change http://www.flickr.com//photos/gsfc/sets/7215 7633503915602/show/through laser altimetry, which bounces lasers pulses off the ice surface to inform the satellite of changes in the height of the ice cover. ICESat’s successor, ICESat-2, is scheduled to launch in 2016. GRACE, still operational, detects variations in Earth’s gravity field resulting from changes in the planet’s mass distribution, including ice displacements.
The new research found all glacial regions lost mass from 2003 to 2009, with the biggest ice losses occurring in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. In contrast, Antarctica’s peripheral glaciers — small ice bodies not connected to the main ice sheet — contributed little to sea level rise during that period. The study builds on a 2012 study using only GRACE data that also found glacier ice loss was less than estimates derived from ground-based measurements.

Current estimates predict all the glaciers in the world contain enough water to raise sea level by as much as 24 inches (about 60 centimeters). In comparison, the entire Greenland ice sheet has the potential to contribute about 20 feet (about 6 meters) to sea level rise and the Antarctic ice sheet just less than 200 feet (about 60 meters).

“Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend to not worry about it,” said study co-author Tad Pfeffer, a glaciologist at the University of Colorado in Boulder. “But it’s like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there’s ice in those glaciers, it’s a major contributor to sea level rise.”

To make ground-based estimates of glacier mass changes, glaciologists perform on-site measurements along a line from a glacier’s summit to its edge. Scientists extrapolate these measurements to the entire glacier area and carry them out for several years to estimate the glacier’s overall mass change over time. While this type of measurement does well for small, individual glaciers, it tends to overestimate ice loss when the findings are extrapolated to larger regions, such as entire mountain ranges.

“Ground observations often can only be collected for the more accessible glaciers, where it turns out thinning is occurring more rapidly than the regional averages,” Gardner said. “That means when those measurements are used to estimate the mass change of the entire region, you end up with regional losses that are too great.”

GRACE does not have fine enough resolution and ICESat does not have sufficient sampling density to study small glaciers, but the two satellites’ estimates of mass change for large glaciered regions agree well, the study concluded.

“We now have a lot more data for the glacier-covered regions because of GRACE and ICESat,” said Gardner. “Without having these independent observations, there was no way to tell that the ground observations were biased.”

The research involved 16 researchers from 10 countries, with major contributions from Clark University, the University of Michigan, Scripps Institution of Oceanography in San Diego, Trent University in Ontario, the University of Colorado at Boulder and the University of Alaska Fairbanks.

 

Steve Cole
NASA Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov

María-José Viñas
NASA’s Goddard Space Flight Center, Greenbelt, Md.
301-614-5883
mj.vinas@nasa.gov

Black Hole Powered Jets Plow Into Galaxy

 

This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA’s Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF’s Very Large Array (pink).

This multi-wavelength view shows 4C+29.30, a galaxy located some 850 million light years from Earth. The radio emission comes from two jets of particles that are speeding at millions of miles per hour away from a supermassive black hole at the center of the galaxy. The estimated mass of the black hole is about 100 million times the mass of our Sun. The ends of the jets show larger areas of radio emission located outside the galaxy.

The X-ray data show a different aspect of this galaxy, tracing the location of hot gas. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could in turn, trigger more output to the radio jet.

Most of the low-energy X-rays from the vicinity of the black hole are absorbed by dust and gas, probably in the shape of a giant doughnut around the black hole. This doughnut, or torus blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole. The optical light seen in the image is from the stars in the galaxy.

The bright spots in X-ray and radio emission on the outer edges of the galaxy, near the ends of the jets, are caused by extremely high energy electrons following curved paths around magnetic field lines. They show where a jet generated by the black hole has plowed into clumps of material in the galaxy (mouse over the image for the location of these bright spots). Much of the energy of the jet goes into heating the gas in these clumps, and some of it goes into dragging cool gas along the direction of the jet. Both the heating and the dragging can limit the fuel supply for the supermassive black hole, leading to temporary starvation and stopping its growth. This feedback process is thought to cause the observed correlation between the mass of the supermassive black hole and the combined mass of the stars in the central region or bulge or a galaxy.

These results were reported in two different papers. The first, which concentrated on the effects of the jets on the galaxy, is available online and was published in the May 10, 2012 issue of The Astrophysical Journal. It is led by Aneta Siemiginowska from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA and the co-authors are Łukasz Stawarz, from the Institute of Space and Astronautical Science in Yoshinodai, Japan; Teddy Cheung from the National Academy of Sciences in Washington, DC; Thomas Aldcroft from CfA; Jill Bechtold from University of Arizona in Tucson, AZ; Douglas Burke from CfA; Daniel Evans from CfA; Joanna Holt from Leiden University in Leiden, The Netherlands; Marek Jamrozy from Jagiellonian University in Krakow, Poland; and Giulia Migliori from CfA. The second, which concentrated on the supermassive black hole, is available online and was published in the October 20, 2012 issue of The Astrophysical Journal. It is led by Malgorzata Sobolewska from CfA, and the co-authors are Aneta Siemiginowska, Giulia Migliori, Łukasz Stawarz, Marek Jamrozy, Daniel Evans, and Teddy Cheung.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/SAO/A. Siemiginowska et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA

 

.D. Harrington, 202-358-0321
Headquarters, Washington
j.d.harrington@nasa.gov

Janet Anderson, 256-544-0034
Marshall Space Flight Center, Huntsville, Ala.
janet.l.anderson@nasa.gov

Megan Watzke 617-496-7998
Chandra X-ray Center, Cambridge, Mass.
mwatzke@cfa.harvard.edu

NASA’s Gravity Probe B Confirms Two Einstein Space-Time Theories

Artist concept of Gravity Probe B orbiting the Earth to measure space-time, a four-dimensional description of the universe including height, width, length, and time. Image credit: NASA

NASA’s Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein’s general theory of relativity, which the spacecraft was designed to test.

The Gravity Probe B spacecraft launches from Vandenberg Air Force Base on April 20, 2004. Image credit: Stanford University

The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates. GP-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth.

 

NASA’s Marshall Space Flight Center in Huntsville, Ala., managed the Gravity Probe-B program for the agency. Stanford University, NASA’s prime contractor for the mission, conceived the experiment and was responsible for the design and integration of the science instrument, mission operations and data analysis. Lockheed Martin Corp. of Sunnyvale, CA designed, integrated and tested the space vehicle and some of its major payload components.

Credit:  NASA

Coming Home Tonight

Credit: NASA

Expedition 35 Commander Chris Hadfield, Soyuz Commander Roman Romanenko and Flight Engineer Tom Marshburn are set to return to Earth Monday night to wrap up 146 days in space and 144 days on the International Space Station.
The trio boarded their Soyuz TMA-07M spacecraft, closing the hatches between the two vehicles at 3:50 p.m. EDT. Undocking is scheduled at 7:08 p.m. A deorbit burn planned at 9:37 p.m. will set the Soyuz on track for a landing at 10:30 p.m.