Lifeboat Foundation

Axisymmetric reconnecting plasmoids are secondary magnetic islands, which are formed due to plasmoid instability. At high Lundquist number, the elongated current sheet becomes MHD unstable due to the plasmoid instability (Biskamp Reference Biskamp 1986; Tajima & Shibata Reference Tajima and Shibata 1997; Loureiro, Schekochihin & Cowley Reference Loureiro, Schekochihin and Cowley 2007; Bhattacharjee et al. Reference Bhattacharjee, Huang, Yang and Rogers 2009; Daughton et al. Reference Daughton, Roytershteyn, Albright, Karimabadi, Yin and Bowers 2009; Ebrahimi & Raman Reference Ebrahimi and Raman 2015; Comisso et al. Reference Comisso, Lingam, Huang and Bhattacharjee 2016), an example of spontaneous reconnection. The transition to plasmoid instability was shown to occur when the local Lundquist number $S = L V_A/\eta$ ( $V_A$ is the Alfven velocity based on the poloidal reconnecting magnetic field, $L$ is the current sheet length and $\eta$ is the magnetic diffusivity) exceeds a critical value (typically a few thousand). Our thruster concept is based on the formation of this elongated current sheet for triggering fast reconnection and plasmoid formation. Effects beyond MHD may also contribute to fast reconnection as the current sheet width ( $\delta _{\mathrm {sp}}$) becomes smaller than the two-fluid or kinetic scales (Cassak, Shay & Drake Reference Cassak, Shay and Drake 2005; Ji & Daughton Reference Ji and Daughton 2011). However, for thruster application we desire system-size MHD plasmoid formation (with radius ranging from a few to tens of centimetres), where kinetic effects become subdominant for low-temperature plasma (in the range of a few eV to a couple of tens of eV). Here, the MHD plasmoid-mediated reconnection occurs at high Lundquist number (about $10⁴$ and above), which is achieved at high magnetic field rather than low magnetic diffusivity (or high temperature). To form a single or multiple X-point reconnection site, oppositely directed biased magnetic field (in the range of 20–1000 G) is injected through a narrow gap in an annular device. We find that the plasmoid structures demonstrated in resistive (or extended) MHD simulations produce high exhaust velocity and thrust that scale favourably with applied magnetic field. It will be shown that the fluid-like magnetic plasmoid loops continuously depart the magnetic configuration about every $10 \ \mathrm {\mu } \textrm {s}$ with Alfvenic velocities in the range of 20 to $500\ \textrm {km}\ \textrm {s}^{-1}$, and the thrust does not ideally depend on the mass of the ion species of the plasma.

Figure 1 shows the main parts of the reconnecting plasmoid thruster in an annular configuration. Magnetic helicity injection starts with an initial injector poloidal field ( $B^{\mathrm {inj}}_P$, in blue, with radial, $R$, and vertical, $Z$, components), connecting the inner and outer biased plates in the injector region. Gas is injected and partially ionized by applying an injector voltage $V_{\mathrm {inj}}$ of a few hundred volts between the inner and outer plates (indicated by numbers 1 and 2), which also drives a current $I_{\mathrm {inj}}$ along the open magnetic field lines. Plasma and open field lines expand into the vessel when the Lorentz force $J_{\mathrm {pol}} \times B_{\phi }$ exceeds the field line tension of the injector poloidal field. The azimuthal ( $\phi$) field shown here, $B_{\phi }$, is generated through injector current ( $I_{\mathrm {inj}}$) alone (by applying $V_{\mathrm {inj}}$), or can be provided externally.

Prototype has proven 99% effective.

Conducting atom-optical experiments in space is interesting for fundamental physics and challenging due to different environment compared to ground. Here the authors report matter-wave interferometry in space using atomic BECs in a sounding rocket.

😃 From robotic people, dogs, it seems scientists are now pushing forward with robotic vines. 😃

This robot has applications to archaeology, space exploration, and search and rescue — with a simple elegant design inspired by a plant. Sign up to Morning Brew for free today: https://ve42.co/mb.

Continue reading “This Unstoppable Robot Could Save Your Life” »

NASA hopes to score a 21st-century Wright Brothers moment on Monday as it attempts to send a miniature helicopter buzzing over the surface of Mars in what would be the first powered, controlled flight of an aircraft on another planet.

Landmark achievements in science and technology can seem humble by conventional measurements. The Wright Brothers’ first controlled flight in the world of a motor-driven airplane, near Kitty Hawk, North Carolina, in 1903 covered just 120 feet (37 meters) in 12 seconds.

A modest debut is likewise in store for NASA’s twin-rotor, solar-powered helicopter Ingenuity.

Elon Musk’s SpaceX plans to send civilians into low-Earth orbit this year. Virgin Galactic is training space travellers. Companies aim to open hotels in space, and offer space day trips, within a few years. We assess the state of play in the nascent space tourism industry.

Massive solar storms in space can be picked up by iOS and Android smartphones, meaning billions of people have a personal geomagnetic storm detector — but the signals threaten to interfere with future location-based applications.

Hoping to get the public more involved in science, study author Sten F. Odenwald, an astronomer at the NASA Goddard Spaceflight Center, published a paper on the topic April 2 in Space Weather. It indicates that even through the unavoidable interference caused by other smartphone components, the phone’s built-in magnetometers can detect geomagnetic storms.

“Smartphones — at least theoretically — should be able to detect some of the strongest storms, pretty easily in fact,” Odenwald told The Academic Times. “Especially if you happen to live up in the northern latitudes — in Minnesota or in Canada, or places like that where it really rocks and rolls.”

This article is part of a series tracking the effects of the COVID-19 pandemic on major businesses and sectors. For other articles and earlier versions, go here.

A global shortage of semiconductors — chips that power massive data-centers, modern autos and countless digital devices — has roiled global manufacturing and is not expected to end soon. It isn’t a blanket problem, however, as different sectors within the chip industry will continue to be affected by the shortage in different ways.

As the industry entered 2020, high demand was expected in the mobile chip area because of the rollout of 5G devices. That path was turned on its head when COVID-19 became a global pandemic, driving millions, if not billions, of people into the safety of their homes to work, go to school, be entertained and to socialize.

Oxygen diatomic molecules have lone-pair electrons and magnetic moments. A high-pressure phase called epsilon oxygen is considered stable in a wide pressure range. This material exhibits the transition to metal at ∼100 GPa (1000, 000× atmospheric pressure). The change in the electronic structure involved in the transition under pressure is difficult to measure using conventional methods. In this study, the electronic structures of oxygen have been successfully measured with oxygen K-edge X-ray Raman scattering spectroscopy. We found a change in the spectra related to the metallization of oxygen. Another change in the electronic structure was also observed at ∼40 GPa. This is likely related to the semimetallic transition.

Electronic structures of dense solid oxygen have been investigated up to 140 GPa with oxygen K-edge X-ray Raman scattering spectroscopy with the help of ab initio calculations based on density functional theory with semilocal metageneralized gradient approximation and nonlocal van der Waals density functionals. The present study demonstrates that the transition energies (Pi*, Sigma*, and the continuum) increase with compression, and the slopes of the pressure dependences then change at 94 GPa. The change in the slopes indicates that the electronic structure changes at the metallic transition. The change in the Pi* and Sigma* bands implies metallic characteristics of dense solid oxygen not only in the crystal a–b plane but also parallel to the c axis. The pressure evolution of the spectra also changes at ∼40 GPa.