A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion (hence ramjet), but whereas a ramjet decelerates the air to subsonic velocities before combustion, the airflow in a scramjet is supersonic throughout the entire engine. That allows the scramjet to operate efficiently at extremely high speeds.
Astrobiology, formerly known as exobiology, is an interdisciplinary scientific field concerned with the origins, early evolution, distribution, and future of life in the universe. Astrobiology considers the question of whether extraterrestrial life exists, and if it does, how humans can detect it.
Astrobiology makes use of molecular biology, biophysics, biochemistry, chemistry, astronomy, physical cosmology, exoplanetology and geology to investigate the possibility of life on other worlds and help recognize biospheres that might be different from that on Earth. The origin and early evolution of life is an inseparable part of the discipline of astrobiology. Astrobiology concerns itself with interpretation of existing scientific data, and although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories.
This interdisciplinary field encompasses research on the origin of planetary systems, origins of organic compounds in space, rock-water-carbon interactions, abiogenesis on Earth, planetary habitability, research on biosignatures for life detection, and studies on the potential for life to adapt to challenges on Earth and in outer space.
A near-Earth object (NEO) is any small Solar System body whose orbit brings it to proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO’s orbit crosses the Earth’s, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets.
There are over 20,000 known near-Earth asteroids (NEAs), over a hundred short-period near-Earth comets (NECs), and a number of solar-orbiting spacecraft and meteoroids large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. NEOs have become of increased interest since the 1980s because of greater awareness of the potential danger. Asteroids as small as 20 m can damage the local environment and populations. Larger asteroids penetrate the atmosphere to the surface of the Earth, producing craters if they impact a continent or tsunamis if they impact sea. Asteroid impact avoidance by deflection is possible in principle, and methods of mitigation are being researched.
Two scales, the Torino scale and the more complex Palermo scale, rate a risk based on how probable the orbit calculations of an identified NEO make an Earth impact and on how bad the consequences of such an impact would be. Some NEOs have had temporarily positive Torino or Palermo scale ratings after their discovery, but as of March 2018, more precise calculations based on longer observation arcs led in all cases to a reduction of the rating to or below 0.
Since 1998, the United States, the European Union, and other nations are scanning the sky for NEOs in an effort called Spaceguard. The initial US Congress mandate to NASA was to catalog at least 90% of NEOs that are at least 1 kilometre (0.62 mi) in diameter, which could cause a global catastrophe,and had been met by 2011. In later years, the survey effort has been expanded to smaller objects which have the potential for large-scale, though not global, damage.
In a generic brick building on the northwestern edge of NASA’s Goddard Space Flight Center campus in Greenbelt, Maryland, thousands of computers packed in racks the size of vending machines hum in a deafening chorus of data crunching. Day and night, they spit out five quadrillion calculations per second. Known collectively as the Discover supercomputer, these machines are tasked with running sophisticated climate models to predict Earth’s future climate.
But now, they’re also sussing out something much farther away: whether any of the more than 4,000 curiously weird planets beyond our solar system — or exoplanets — discovered in the past two decades could have the ingredients necessary to support life.
Video credit: NASA’s Goddard Space Flight Center/LK Ward (USRA): Lead Producer/Claire Andreoli (NASA/GSFC): Lead Public Affairs Officer/Lonnie Shekhtman (ADNET): Lead Writer/Alex Kekesi (GST): Lead Visualizer/Anthony DelGenio (NASA/GSFC GISS): Lead Scientist/Avi Mandell (NASA/GSFC): Lead Scientist/Michael J. Way (NASA/GSFC GISS): Scientist/Chris Smith (USRA): Animator/Aaron E. Lepsch (ADNET): Technical Support/Music: “Machine Learning” by Jon Cotton and Ben Niblett; “No Wave” by Julien Vignon; “The Missing Star” by Matthew Charles Gilbert Davidson; all from Universal Production Music
When a new NASA space telescope opens its eyes in the mid 2020s, it will peer at the universe through some of the most sophisticated sunglasses ever designed. This multi-layered technology, the coronagraph instrument, might more rightly be called “starglasses”: a system of masks, prisms, detectors and even self-flexing mirrors built to block out the glare from distant stars — and reveal the planets in orbit around them. Normally, that glare is overwhelming, blotting out any chance of seeing orbiting planets. The star’s photons — particles of light — swamp those from the planet when they hit the telescope.
WFIRST’s coronagraph just completed a major milestone: a preliminary design review by NASA. The instrument has met all design, schedule and budget requirements, and can now proceed to the next phase, b uilding hardware for flight. The WFIRST mission’s coronagraph is meant to demonstrate the power of increasingly advanced technology. As it captures light directly from large, gaseous exoplanets, and from disks of dust and gas surrounding other stars, it will point the way to the future: single pixel “images” of rocky planets the size of Earth. Then the light can be spread into a rainbow spectrum, revealing which gases are present in the planet’s atmosphere — perhaps oxygen, methane, carbon dioxide, and maybe even signs of life.
The two flexible mirrors inside the coronagraph are key components. As light that has traveled tens of light-years from an exoplanet enters the telescope, thousands of actuators move like pistons, changing the shape of the mirrors in real time. The flexing of these “deformable mirrors” compensates for tiny flaws and changes in the telescope’s optics. Changes on the mirrors’ surfaces are so precise they can compensate for errors smalle r than the width of a strand of DNA. These mirrors, in tandem with high-tech “masks,” another major advance, squelch the star’s diffraction as well – the bending of light waves around the edges of light-blocking elements inside the coronagraph.
The result: blinding starlight is sharply dimmed, and faintly glowing, previously hidden planets appear. The star-dimming technology also could bring the clearest-ever images of distant star systems’ formative years — when they are still swaddled in disks of dust and gas as infant planets take shape inside.
The instrument’s deformable mirrors and other advanced technology — known as “active wavefront control” — should mean a leap of 100 to 1,000 times the capability of previous coronagraphs.
Understanding how fire spreads and behaves in space is crucial for the safety of future astronauts and for understanding and controlling fire here on Earth.
The primary focus of microgravity combustion experiments has been related to either fire safety in space or better understanding of practical combustion on Earth and in space. The reduced gravity creates flames that look a lot different from the ones seen here on Earth: with the near absence of gravity on the space station, flames tend to be spherical. On Earth, hot gasses from the flame rise while gravity pulls cooler, denser air to the bottom of the flame. This creates both the shape of the flame, as well as a flickering effect. In microgravity, this flow doesn’t occur. This reduces the variables in combustion experiments, making them simpler and creating spherical shaped flames.
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