A Falcon 9 launched 140 payloads on its latest dedicated rideshare mission Nov. 28, ranging from European government spacecraft to a private astronomy satellite.
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The Baiknour pad used for the launch of the latest crew to the ISS has sustained damage, raising questions about its ability to support upcoming missions to the station.
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W-5 is the newest spacecraft in the company’s “W-Series” of free-flying reentry vehicles designed to orbit Earth, conduct on-orbit processing and return space-made materials.
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SAN FRANCISCO – Italy’s D-Orbit sent satellites and hosted payloads into orbit Nov. 26 aboard two ION orbital transfer vehicles launched on SpaceX’s Transporter-15 rideshare. Italy’s first optical intersatellite link (OISL) mission was onboard the IONs alongside payloads from Spire, Spaceium, Pale Blue, Finland’s Aalto University, Planetek and StardustMe. “With these two missions, we cross […]
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China’s space administration has published a policy blueprint aimed at accelerating development of commercial space and embedding it within its broader national space ambitions.
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A new heat engine driven by the temperature difference between Earth’s surface and outer space has been developed by Tristan Deppe and Jeremy Munday at the University of California Davis. In an outdoor trial, the duo showed how their engine could offer a reliable source of renewable energy at night.
While solar cells do a great job of converting the Sun’s energy into electricity, they have one major drawback, as Munday explains: “Lack of power generation at night means that we either need storage, which is expensive, or other forms of energy, which often come from fossil fuel sources.”
One solution is to exploit the fact that the Earth’s surface absorbs heat from the Sun during the day and then radiates some of that energy into space at night. While space has a temperature of around −270° C, the average temperature of Earth’s surface is a balmy 15° C. Together, these two heat reservoirs provide the essential ingredients of a heat engine, which is a device that extracts mechanical work as thermal energy flows from a heat source to a heat sink.
“At first glance, these two entities appear too far apart to be connected through an engine. However, by radiatively coupling one side of the engine to space, we can achieve the needed temperature difference to drive the engine,” Munday explains.
For the concept to work, the engine must radiate the energy it extracts from the Earth within the atmospheric transparency window. This is a narrow band of infrared wavelengths that pass directly into outer space without being absorbed by the atmosphere.
To demonstrate this concept, Deppe and Munday created a Stirling engine, which operates through the cyclical expansion and contraction of an enclosed gas as it moves between hot and cold ends. In their setup, the ends were aligned vertically, with a pair of plates connecting each end to the corresponding heat reservoir.
For the hot end, an aluminium mount was pressed into soil, transferring the Earth’s ambient heat to the engine’s bottom plate. At the cold end, the researchers attached a black-coated plate that emitted an upward stream of infrared radiation within the transparency window.
In a series of outdoor experiments performed throughout the year, this setup maintained a temperature difference greater than 10° C between the two plates during most months. This was enough to extract more than 400 mW per square metre of mechanical power throughout the night.
“We were able to generate enough power to run a mechanical fan, which could be used for air circulation in greenhouses or residential buildings,” Munday describes. “We also configured the device to produce both mechanical and electrical power simultaneously, which adds to the flexibility of its operation.”
With this promising early demonstration, the researchers now predict that future improvements could enable the system to extract as much as 6 W per square metre under the same conditions. If rolled out commercially, the heat engine could help reduce the reliance of solar power on night-time energy storage – potentially opening a new route to cutting carbon emissions.
The research has described in Science Advances.
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A new microscale version of the flumes that are commonly used to reproduce wave behaviour in the laboratory will make it far easier to study nonlinear hydrodynamics. The device consists of a layer of superfluid helium just a few atoms thick on a silicon chip, and its developers at the University of Queensland, Australia, say it could help us better understand phenomena ranging from oceans and hurricanes to weather and climate.
“The physics of nonlinear hydrodynamics is extremely hard to model because of instabilities that ultimately grow into turbulence,” explains study leader Warwick Bowen of Queensland’s Quantum Optics Laboratory. “It is also very hard to study in experiments since these often require hundreds-of-metre-long wave flumes.”
While such flumes are good for studying shallow-water dynamics like tsunamis and rogue waves, Bowen notes that they struggle to access many of the complex wave behaviours, such as turbulence, found in nature.
The team say that the geometrical structure of the new wave-on-a-chip device can be designed at will using lithographic techniques and built in a matter of days. Superfluid helium placed on its surface can then be controlled optomechanically. Thanks to these innovations, the researchers were able to experimentally measure nonlinear hydrodynamics millions of times faster than would be possible using traditional flumes. They could also “amplify” the nonlinearities of complex behaviours, making them orders of magnitude stronger than is possible in even the largest wave flumes.
“This promises to change the way we do nonlinear hydrodynamics, with the potential to discover new equations that better explain the complex physics behind it,” Bowen says. “Such a technique could be used widely to improve our ability to predict both natural and engineered hydrodynamic behaviours.”
So far, the team has measured several effects, including wave steepening, shock fronts and solitary wave fission thanks to the chip. While these nonlinear behaviours had been predicted in superfluids, they had never been directly observed there until now.
The Quantum Optics Laboratory researchers have been studying superfluid helium for over a decade. A key feature of this quantum liquid is that it flows without resistance, similar to the way electrons move without resistance in a superconductor. “We realized that this behaviour could be exploited in experimental studies of nonlinear hydrodynamics because it allows waves to be generated in a very shallow depth – even down to just a few atoms deep,” Bowen explains.
In conventional fluids, Bowen continues, resistance to motion becomes hugely important at small scales, and ultimately limits the nonlinear strengths accessible in traditional flume-based testing rigs. “Moving from the tens-of-centimetre depths of these flumes to tens-of-nanometres, we realized that superfluid helium could allow us to achieve many orders of magnitude stronger nonlinearities – comparable to the largest flows in the ocean – while also greatly increasing measurement speeds. It was this potential that attracted us to the project.”
The experiments were far from simple, however. To do them, the researchers needed to cryogenically cool the system to near absolute zero temperatures. They also needed to fabricate exceptionally thin superfluid helium films that interact very weakly with light, as well as optical devices with structures smaller than a micron. Combining all these components required what Bowen describes as “something of a hero experiment”, with important contributions coming from the team’s co-leader, Christopher Baker, and Walter Wasserman, who was then a PhD student in the group. The wave dynamics themselves, Bowen adds, were “exceptionally complex” and were analysed by Matthew Reeves, the first author of a Science paper describing the device.
As well as the applications areas mentioned earlier, the team say the new work, which is supported by the US Defense Advanced Research Project Agency’s APAQuS Program, could also advance our understanding of strongly-interacting quantum structures that are difficult to model theoretically. “Superfluid helium is a classic example of such a system,” explains Bowen, “and our measurements represent the most precise measurements of wave physics in these. Other applications may be found in quantum technologies, where the flow of superfluid helium could – somewhat speculatively – replace superconducting electron flow in future quantum computing architectures.”
The researchers now plan to use the device and machine learning techniques to search for new hydrodynamics equations.
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BREMEN – The European Space Agency’s Human and Robotic Exploration (HRE) program fell short of its budget request at the ministerial, with member nations agreeing to contribute 2.98 billion euros ($3.08 billion), accounting for roughly 70% of the 3.77 billion euro ask. ESA set its overall budget at 22.1 billion euros — a significant increase […]
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A Soyuz spacecraft delivered two Russian cosmonauts and one American astronaut to the International Space Station Nov. 27 for an eight-month stay.
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ESA member states are contributing more than 22 billion euros for the next three years, very close to its overall goal but with some programs faring better than others.
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An effect first observed decades ago by Nobel laureate Arthur Ashkin has been used to fine tune the electrical charge on objects held in optical tweezers. Developed by an international team led by Scott Waitukaitis of the Institute of Science and Technology Austria, the new technique could improve our understanding of aerosols and clouds.
Optical tweezers use focused laser beams to trap and manipulate small objects about 100 nm to 1 micron in size. Their precision and versatility have made them a staple across fields from quantum optics to biochemistry.
Ashkin shared the 2018 Nobel prize for inventing optical tweezers and in the 1970s he noticed that trapped objects can be electrically charged by the laser light. “However, his paper didn’t get much attention, and the observation has essentially gone ignored,” explains Waitukaitis.
Waitukaitis’ team rediscovered the effect while using optical tweezers to study how charges build up in the ice crystals accumulating inside clouds. In their experiment, micron-sized silica spheres stood in for the ice, but Ashkin’s charging effect got in their way.
“Our goal has always been to study charged particles in air in the context of atmospheric physics – in lightning initiation or aerosols, for example,” Waitukaitis recalls. “We never intended for the laser to charge the particle, and at first we were a bit bummed out that it did so.”
Their next thought was that they had discovered a new and potentially useful phenomenon. “Out of due diligence we of course did a deep dive into the literature to be sure that no one had seen it, and that’s when we found the old paper from Ashkin, “ says Waitukaitis.
In 1976, Ashkin described how optically trapped objects become charged through a nonlinear process whereby electrons absorb two photons simultaneously. These electrons can acquire enough energy to escape the object, leaving it with a positive charge.
Yet beyond this insight, Ashkin “wasn’t able to make much sense of the effect,” Waitukaitis explains. “I have the feeling he found it an interesting curiosity and then moved on.”
To study the effect in more detail, the team modified their optical tweezers setup so its two copper lens holders doubled as electrodes, allowing them to apply an electric field along the axis of the confining, opposite-facing laser beams. If the silica sphere became charged, this field would cause it to shake, scattering a portion of the laser light back towards each lens.
The researchers picked off this portion of the scattered light using a beam splitter, then diverted it to a photodiode, allowing them to track the sphere’s position. Finally, they converted the measured amplitude of the shaking particle into a real-time charge measurement. This allowed them to track the relationship between the sphere’s charge and the laser’s tuneable intensity.
Their measurements confirmed Ashkin’s 1976 hypothesis that electrons on optically-trapped objects undergo two-photon absorption, allowing them to escape. Waitukaitis and colleagues improved on this model and showed how the charge on a trapped object can be controlled precisely by simply adjusting the laser’s intensity.
As for the team’s original research goal, the effect has actually been very useful for studying the behaviour of charged aerosols.
“We can get [an object] so charged that it shoots off little ‘microdischarges’ from its surface due to breakdown of the air around it, involving just a few or tens of electron charges at a time,” Waitukaitis says. “This is going to be really cool for studying electrostatic phenomena in the context of particles in the atmosphere.“
The study is described in Physical Review Letters.
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Earlier this autumn I had the pleasure of visiting the Perimeter Institute for Theoretical Physics in Waterloo Canada – where I interviewed four physicists about their research. This is the second of those conversations to appear on the podcast – and it is with Bianca Dittrich, whose research focuses on quantum gravity.
Albert Einstein’s general theory of relativity does a great job at explaining gravity but it is thought to be incomplete because it is incompatible with quantum mechanics. This is an important shortcoming because quantum mechanics is widely considered to be one of science’s most successful theories.
Developing a theory of quantum gravity is a crucial goal in physics, but it is proving to be extremely difficult. In this episode, Dittrich explains some of the challenges and talks about ways forward – including her current research on spin foams. We also chat about the intersection of quantum gravity and condensed matter physics; and the difficulties of testing theories against observational data.
IOP Publishing’s new Progress In Series: Research Highlights website offers quick, accessible summaries of top papers from leading journals like Reports on Progress in Physics and Progress in Energy. Whether you’re short on time or just want the essentials, these highlights help you expand your knowledge of leading topics.
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