OrbitalHub

Wikipedia dicit:

The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33 percent of their pre-1975 values. The ozone hole occurs during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container. Within this polar vortex, over 50 percent of the lower stratospheric ozone is destroyed during the Antarctic spring.

As explained above, the primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds (PSCs).

These polar stratospheric clouds form during winter, in the extreme cold. Polar winters are dark, consisting of three months without solar radiation (sunlight). The lack of sunlight contributes to a decrease in temperature and the polar vortex traps and chills the air. Temperatures hover around or below −80 °C. These low temperatures form cloud particles. There are three types of PSC clouds—nitric acid trihydrate clouds, slowly cooling water-ice clouds, and rapid cooling water-ice (nacreous) clouds—provide surfaces for chemical reactions whose products will, in the spring lead to ozone destruction.

The photochemical processes involved are complex but well understood. The key observation is that, ordinarily, most of the chlorine in the stratosphere resides in “reservoir” compounds, primarily chlorine nitrate (ClONO₂) as well as stable end products such as HCl. The formation of end products essentially removes Cl from the ozone depletion process. The former sequester Cl, which can be later made available via absorption of light at shorter wavelengths than 400 nm. During the Antarctic winter and spring, however, reactions on the surface of the polar stratospheric cloud particles convert these “reservoir” compounds into reactive free radicals (Cl and ClO). Denitrification is the process by which the clouds remove NO₂ from the stratosphere by converting it to nitric acid in PSC particles, which then are lost by sedimentation. This prevents newly formed ClO from being converted back into ClONO₂.

The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring. During winter, even though PSCs are at their most abundant, there is no light over the pole to drive chemical reactions. During the spring, however, sunlight returns and provides energy to drive photochemical reactions and melt the polar stratospheric clouds, releasing considerable ClO, which drives the hole mechanism. Further warming temperatures near the end of spring break up the vortex around mid-December. As warm, ozone and NO₂-rich air flows in from lower latitudes, the PSCs are destroyed, the enhanced ozone depletion process shuts down, and the ozone hole closes.

Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas-phase reactions, which occurs primarily in the upper stratosphere.

Video credit: NASA’s Ames Research Center/Bishop’s University /Jason Rowe

NASA dicit:

This sonification turns the orbits of a new seven-planet system, discovered by NASA’s retired Kepler space telescope, into sound. It begins at the center of the system with the innermost orbit and builds toward the outermost, introducing each orbit with a new sound that plays once per rotation around the central Sun-like star. It then focuses on two specific orbits in resonance, which creates a beating sound with the inner rotating twice in the same period as the outer rotates three times. Next, only the three outer-most planets are singled out as an orbital resonance chain before blending all seven together again. This is the first planetary system in which each planet bathed in more radiant heat from their host star per area than any in our solar system.

Video credit: NASA’s Ames Research Center/Bishop’s University /Jason Rowe

Wikipedia dicit:

The Surface Water and Ocean Topography (SWOT) mission is a satellite altimeter jointly developed and operated by NASA and CNES, the French space agency, in partnership with the Canadian Space Agency (CSA) and UK Space Agency (UKSA). The objectives of the mission are to make the first global survey of the Earth’s surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time.

While past satellite missions like the Jason series altimeters (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3) have provided variation in river and lake water surface elevations at select locations, SWOT will provide the first truly global observations of changing water levels, stream slopes, and inundation extents in rivers, lakes, and floodplains. In the world’s oceans, SWOT will observe ocean circulation at unprecedented scales of 15–25 km (9.3–15.5 mi), approximately an order of magnitude finer than current satellites. Because it uses wide-swath altimetry technology, SWOT will almost completely observe the world’s oceans and freshwater bodies with repeated high-resolution elevation measurements, allowing observations of variations.

Video credit: NASA Jet Propulsion Laboratory

NASA dicit:

The Lunar Lab and Regolith Testbed currently houses two large indoor “sandboxes” filled with tons of simulated lunar dust. With both testbeds, most areas on the Moon can be simulated with a high degree of accuracy.

The facility’s first sandbox measures approximately 13 feet by 13 feet by 1.5 feet (4 meters by 4 meters by 0.5 meter) and is filled with eight tons of Johnson Space Center One simulant (JSC-1A) – making it the world’s largest collection of the material. The JSC-1A simulant mimics the Moon’s mare basins and is dark grey in color.

The facility was recently upgraded to include a second, larger testbed, filled with more than 20 tons of Lunar Highlands Simulant-1 (LHS-1), which is light grey to simulate the lunar highlands. It measures 62 feet by 13 feet by 1 foot (19 meters by 4 meters by 0.3 meter), and can be reconfigured to be a smaller, but deeper, testbed.

Sometimes researchers painstakingly shape the dust with hand tools to recreate, as accurately as possible, features astronauts and rovers are likely to encounter. These include tiny pits and small craters measuring as small as a couple feet to a few yards across. It may also mean placing small rocks and other debris to resemble actual places observed by Moon-orbiting spacecraft.

One feature that makes the Testbed truly unique, is a set of bright, high-power lights that simulate the Sun’s glaring rays as they are cast across the lunar landscape. Researchers can accurately recreate lighting conditions that are relevant to locations on the Moon’s poles and across a range of lunar times – past, present, or future.

Established in 2009 by NASA’s Centennial Challenges Program as the Lunar Regolith Testbed in the NASA Research Park at Ames, the facility was created through a partnership between the then-called NASA Lunar Science Institute (now the agency’s Solar System Exploration Research Virtual Institute) and the California Space Authority. Since then, it’s been used year-round by researchers seeking a high-fidelity environment to test hardware designs intended for the lunar surface, including projects within the agency’s Advanced Exploration Systems and Game Changing Development technology programs.

Video credit: NASA’s Ames Research Center

Wikipedia dicit:

The Space Launch System (SLS) is an American super heavy-lift expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis Moon landing program, SLS is designed to launch the crewed Orion spacecraft on a trans-lunar trajectory. The first SLS launch was the uncrewed Artemis 1, which took place on 16 November 2022.

Development of SLS began in 2011, as a replacement for the retired Space Shuttle as well as the cancelled Ares I and Ares V launch vehicles. As a Shuttle-derived vehicle, the SLS reuses hardware from the Shuttle program, including the solid rocket boosters and RS-25 first stage engines. A Congressionally mandated late 2016 launch was delayed by nearly 6 years.

All Space Launch System flights are launched from Launch Complex 39B at the Kennedy Space Center in Florida. The first three SLS flights use the Block 1 configuration, comprising a core stage, extended Space Shuttle boosters developed for Ares I and the ICPS upper stage. An improved Block 1B configuration, with the Exploration Upper Stage, is planned to debut on the fourth flight; a further improved Block 2 configuration featuring new solid rocket boosters is planned to debut on the ninth flight. After the launch of Artemis 4, NASA plans to transfer production and launch operations of SLS to Deep Space Transport LLC, a joint venture between Boeing and Northrop Grumman.

Video credit: NASA’s Marshall Space Flight Center

Wikipedia dicit:

A nuclear thermal rocket (NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket. In an NTR, a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor and then expands through a rocket nozzle to create thrust. The external nuclear heat source theoretically allows a higher effective exhaust velocity and is expected to double or triple payload capacity compared to chemical propellants that store energy internally.

NTRs have been proposed as a spacecraft propulsion technology, with the earliest ground tests occurring in 1955. The United States maintained an NTR development program through 1973 when it was shut down for various reasons, for example to focus on Space Shuttle development. Although more than ten reactors of varying power output have been built and tested, as of 2023, no nuclear thermal rocket has flown.

Whereas all early applications for nuclear thermal rocket propulsion used fission processes, research in the 2010s has moved to fusion approaches. The Direct Fusion Drive project at the Princeton Plasma Physics Laboratory is one such example, although “energy-positive fusion has remained elusive”. In 2019, the U.S. Congress approved US$125 million in development funding for nuclear thermal propulsion rockets.

In May 2022 DARPA issued an RFP for the next phase of their Demonstration Rocket for Agile Cislunar Operations (DRACO) nuclear thermal engine program. This follows on their selection, in 2021, of an early engine design by General Atomics and two spacecraft concepts from Blue Origin and Lockheed Martin. The next phases of the program will focus on the design, development, fabrication, and assembly of a nuclear thermal rocket engine. In July 2023, Lockheed Martin was awarded the contract to build the spacecraft and BWX Technologies (BWXT) will develop the nuclear reactor. A launch is expected in 2027.

Video credit: Lockheed Martin