Fire acts differently in space than on Earth. Sandra Olson, an aerospace engineer at NASA's Glenn Research Center, demonstrates just how differently in her art. This artwork is comprised of multiple overlays of three separate microgravity flame images. Each image is of flame spread over cellulose paper in a spacecraft ventilation flow in microgravity. The different colors represent different chemical reactions within the flame. NASA
A rocket engine is fired during a test at the Marshall Space Flight Center in Huntsville, Alabama as part of a series of 14 hot-fire tests of a 50,000-pound thrust RS-88 rocket engine. The engine is being designed and built by the Rocketdyne Propulsion & Power unit of The Boeing Company. NASA
Resembling an aerial fireworks explosion, this dramatic NASA Hubble Space Telescope picture of the energetic star WR124 reveals it is surrounded by hot clumps of gas being ejected into space at speeds of over 100,000 miles per hour. Also remarkable are vast arcs of glowing gas around the star, which are resolved into filamentary, chaotic substructures, yet with no overall global shell structure. Yves Grosdidier/Anthony Moffat/Universitie de Montreal/Gilles Joncas/Universite Laval/Agnes Acker/Observatoire de Strasbourg/NASA
Viewed from the Banana River Viewing Site at NASA's Kennedy Space Center in Florida, space shuttle Discovery arcs through a cloud-brushed sky, lighted by the trail of fire after launch on the STS-128 mission in 2009. NASA/Ben Cooper
This photograph of the transition from ignition to flame under external radiation was taken during a test by the Japan Microgravity Center. NASA/Glenn Research Center Collection
This 50-light-year-wide view of the central region of the Carina Nebula where a maelstrom of star birth — and death — is taking place. This image is a mosaic of the Carina Nebula assembled from 48 frames taken with Hubble's Advanced Camera for Surveys. NASA/ESA/N. Smith/University of California/Berkeley
NASA crew members participate in firefighting and fire training exercises in JSC Fire Training Pit across from the Gilruth Center Bldg 207. Commander Robert L. Gibson sprays blaze with fire extinguisher as instructor coaches him. NASA
A test of a J-33 jet engine with its tail removed to study flame propagation of ignition is seen in 1948. NASA
The Hubble Space Telescope observes the the fire and fury of stellar birth by observing star jets in the Orion Nebula. NASA
Nearly enveloped by the smoke after ignition, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad in 2007 to begin its 1.7-billion-mile journey through the inner solar system to study a pair of asteroids. NASA/Sandra Joseph & Rafael Hernandez
This photograph shows a candle flame burning over time in microgravity, it shows pieces of wax or soot moving through the flame about 25 seconds after ignition. NASA
Billows of smoke and steam infused with the fiery light from space shuttle Endeavour's launch on the STS-127 mission fill NASA Kennedy Space Center's Launch Pad 39A on July 15, 2009. NASA/Sandra Joseph, Kevin O'Connell
This image from NASA's Spitzer Space Telescope shows Cassiopeia A in infrared light. The faint, blue glow surrounding the dead star is material that was energized by a shock wave, called the forward shock, which was created when the star blew up. NASA/JPL-Caltech/L.Rudnick (Univ. of Minn.)
The Soyuz TMA-01M rocket launched from the Baikonur Cosmodrome in Kazakhstan on Friday, Oct. 8, carrying Expedition 25 Soyuz Commander Alexander Kaleri of Russia, NASA Flight Engineer Scott J. Kelly and Russian Flight Engineer Oleg Skripochka to the International Space Station. NASA/Carla Cioffi
Just before sunset, Space Shuttle Endeavour lifts off Launch Pad 39B on mission STS-108. At left can be seen one of the six 12-foot-high rainbirds circling the Shuttle on the mobile launcher platform. Part of the sound suppression system, when solid rocket booster ignition and liftoff occur, a torrent of water flows onto the MLP from the rainbirds. NASA
The first X-43A hypersonic research aircraft and its modified Pegasus booster rocket were carried aloft by NASA's NB-52B carrier aircraft from Dryden Flight Research Center at Edwards Air Force Base, Calif., on June 2, 2001 for the first of three high-speed free flight attempts. About an hour and 15 minutes later the Pegasus booster was released from the B-52 to accelerate the X-43A to its intended speed of Mach 7. NASA Dryden Flight Research Center
The five F-1 engines of the Apollo/Saturn V space vehicle's first stage leaves a trail of flame in the sky after liftoff. The launch of the Apollo 6 unmanned space mission occurred on April 4, 1968. These views of the Apollo 6 launch were taken from a chase plane. NASA
Chandra's image of N63A shows material heated to about ten million degrees Celsius by a shock wave generated by the supernova explosion. The fluffy crescent-shaped X-ray features that appear around the edge of the remnant are thought to be fragments of high-speed matter shot out from the star when it exploded, like shrapnel from a bomb. NASA/CXC/Rutgers/J.Warren et al.
Space shuttle Discovery roars off Launch Pad 39A on the STS-119 mission atop twin towers of fire that light up the sky after sunset at NASA's Kennedy Space Center in Florida. Liftoff was on March 15, 2009. NASA
Marshall Space Flight Center's rocket development has always included component testing. Pictured here is a Cell 114-B burn stack. The C114-B is part of the gas generators used to test heat exchanges for the F-1 engine. On the initial firing of the C114-B the spark ignition would not light. The rocket propellant mixed with the liquid oxygen gelled creating a bomb. After several attempts at ignition, the spark ignited and blew up the stand. NASA
The airstrikes have targeted at least nine of Yemen's 21 provinces and have prevented the Houthis from reaching Aden, the former capital of the once-independent south.
ByAhmed Al-Haj, Associated Press
Saudi-led naval forces imposed a blockade on Yemen's ports as coalition airstrikes on Monday repelled an advance on the southern port city of Aden by Shiite rebels and forces loyal to a former president.