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Air pollution linked to almost a million stillbirths a year
Tue, 29 Nov 2022 16:00:52 GMT
First global analysis follows discovery of toxic pollution particles in lungs and brains of foetuses
Almost a million stillbirths a year can be attributed to air pollution, according to the first global study.
The research estimated that almost half of stillbirths could be linked to exposure to pollution particles smaller than 2.5 microns (PM2.5), mostly produced from the burning of fossil fuels.
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This is a guest post in recognition of the 75th anniversary of the invention of the transistor. It is adapted from an essay in the July 2022 IEEE Electron Device Society Newsletter. The views expressed here are solely those of the author and do not represent positions of IEEE Spectrum or the IEEE.
On the 75th anniversary of the invention of the transistor, a device to which I have devoted my entire career, I’d like to answer two questions: Does the world need better transistors? And if so, what will they be like?
I would argue, that yes, we are going to need new transistors, and I think we have some hints today of what they will be like. Whether we’ll have the will and economic ability to make them is the question.
I believe the transistor is and will remain key to grappling with the impacts of global warming. With its potential for societal, economic, and personal upheaval, climate change calls for tools that give us humans orders-of-magnitude more capability.
Semiconductors can raise the abilities of humanity like no other technology. Almost by definition, all technologies increase human abilities. But for most of them, natural resources and energy constrains make orders-of magnitude improvements questionable. Transistor-enabled technology is a unique exception for the following reasons.
How we’ll continue to improve transistor technology is relatively clear in the short term, but it gets murkier the farther out you go from today. In the near term, you can glimpse the transistor’s future by looking at its recent past.
The basic planar (2D) MOSFET structure remained unchanged from 1960 until around 2010, when it became impossible to further increase transistor density and decrease the device’s power consumption. My lab at the University of California, Berkeley, saw that point coming more than a decade earlier. We reported the invention of the FinFET, the planar transistor’s successor, in 1999. FinFET, the first 3D MOSFET, changed the flat and wide transistor structure to a tall and narrow one. The benefit is better performance in a smaller footprint, much like the benefit of multistory buildings over single-story ones in a crowded city.
The FinFET is also what’s called a thin-body MOSFET, a concept that continues to guide the development of new devices. It arose from the insight that current will not leak through a transistor within several nanometers of the silicon surface because the surface potential there is well controlled by the gate voltage. FinFETs take this thin-body concept to heart. The device’s body is the vertical silicon fin, which is covered by oxide insulator and gate metal, leaving no silicon outside the range of strong gate control. FinFETs reduced leakage current by orders of magnitude and lowered transistor operating voltage. It also pointed toward the path for further improvement: reducing the body thickness even more.
The fin of the FinFET has become thinner and taller with each new technology node. But this progress has now become too difficult to maintain. So industry is adopting a new 3D thin-body CMOS structure, called gate-all-around (GAA). Here, a stack of ribbons of semiconductor make up the thin body.
Each evolution of the MOSFET structure has been aimed at producing better control over charge in the silicon by the gate [pink]. Dielectric [yellow] prevents charge from moving from the gate into the silicon body [blue].
The 3D thin-body trend will continue from these 3D transistors to 3D-stacked transistors, 3D monolithic circuits, and multichip packaging. In some cases, this 3D trend has already reached great heights. For instance, the regularity of the charge-trap memory-transistor array allowed NAND flash memory to be the first IC to transition from 2D circuits to 3D circuits. Since the first report of 3D NAND by Toshiba in 2007, the number of stacked layers has grown from 4 to beyond 200.
Monolithic 3D logic ICs will likely start modestly, with stacking the two transistors of a CMOS inverter to reduce all logic gates’ footprints [see “3D-Stacked CMOS Takes Moore’s Law to New Heights”]. But the number of stacks may grow. Other paths to 3D ICs may employ the transfer or deposition of additional layers of semiconductor films, such as silicon, silicon germanium, or indium gallium arsenide onto a silicon wafer.
The thin-body trend might meet its ultimate endpoint in 2D semiconductors, whose thickness is measured in atoms. Molybdenum disulfide molecules, for example, are both naturally thin and relatively large, forming a 2D semiconductor that may be no more than three atoms wide yet have very good semiconductor properties. In 2016, engineers in California and Texas used a film of the 2D-semiconductor molecule molybdenum disulfide and a carbon nanotube to demonstrate a MOSFET with a critical dimension: a gate length just 1 nanometer across. Even with a gate as short as 1 nm, the transistor leakage current was only 10 nanoamperes per millimeter, comparable with today’s best production transistor.
“The progress of transistor technology has not been even or smooth.”
One can imagine that in the distant future, the entire transistor may be prefabricated as a single molecule. These prefabricated building blocks might be brought to their precise locations in an IC through a process called directed-self-assembly (DSA). To understand DSA, it may be helpful to recall that a COVID virus uses its spikes to find and chemically dock itself onto an exact spot at the surface of particular human cells. In DSA, the docking spots, the “spikes,” and the transistor cargo are all carefully designed and manufactured. The initial docking spots may be created with lithography on a substrate, but additional docking spots may be brought in as cargo in subsequent steps. Some of the cargo may be removed by heat or other means if they are needed only during the fabrication process but not in the final product.
Besides making transistors smaller, we’ll have to keep reducing their power consumption. Here we could see an order-of-magnitude reduction through the use of what are called negative-capacitance field-effect transistors (NCFET). These require the insertion of a nanometer-thin layer of ferroelectric material, such as hafnium zirconium oxide, in the MOSFET’s gate stack. Because the ferroelectric contains its own internal electric field, it takes less energy to switch the device on or off. An additional advantage of the thin ferroelectric is the possible use of the ferroelectric’s capacity to store a bit as the state of its electric field, thereby integrating memory and computing in the same device.
The author [left] received the U.S. National Medal of Technology and Innovation from President Barack Obama [right] in 2016.
Kevin Dietsch/UPI/Alamy
To some degree the devices I’ve described arose out of existing trends. But future transistors may have very different materials, structures, and operating mechanisms from those of today’s transistor. For example, the nanoelectromechanical switch is a return to the mechanical relays of decades past rather than an extension of the transistor. Rather than relying on the physics of semiconductors, it uses only metals, dielectrics, and the force between closely spaced conductors with different voltages applied to them.
All these examples have been demonstrated with experiments years ago. However, bringing them to production will require much more time and effort than previous breakthroughs in semiconductor technology.
Will we be able to achieve these feats? Some lessons from the past indicate that we could.
The first lesson is that the progress of transistor technology has not been even or smooth. Around 1980, the rising power consumption per chip reached a painful level. The adoption of CMOS, replacing NMOS and bipolar technologies—and later, the gradual reduction of operation voltage from 5 volts to 1—gave the industry 30 years of more or less straightforward progress. But again, power became an issue. Between 2000 and 2010, the heat generated per square centimeter of IC was projected by thoughtful researchers to soon reach that of the nuclear-reactor core. The adoption of 3D thin-body FinFET and multicore processor architectures averted the crisis and ushered in another period of relatively smooth progress.
The history of transistor technology may be described as climbing one mountain after another. Only when we got to the top of one were we able see the vista beyond and map a route to climb the next taller and steeper mountain.
The second lesson is that the core strength of the semiconductor industry—nanofabrication—is formidable. History proves that, given sufficient time and economic incentives, the industry has been able to turn any idea into reality, as long as that idea does not violate scientific laws.
But will the industry have sufficient time and economic incentives to continue climbing taller and steeper mountains and keep raising humanity’s abilities?
It’s a fair question. Even as the fab industry’s resources grow, the mountains of technology development grow even faster. A time may come when no one fab company can reach the top of the mountain to see the path ahead. What happens then?
The revenue of all semiconductor fabs (both independent and those, like Intel, that are integrated companies) is about one-third of the semiconductor industry revenue. But fabs make up just 2 percent of the combined revenues of the IT, telecommunications, and consumer-electronics industries that semiconductor technology enables. Yet the fab industry bears most of the growing burden of discovering, producing, and marketing new transistors and nanofabrication technologies. That needs to change.
For the industry to survive, the relatively meager resources of the fab industry must be prioritized in favor of fab building and shareholder needs over scientific exploration. While the fab industry is lengthening its research time horizon, it needs others to take on the burden too. Humanity’s long-term problem-solving abilities deserve targeted public support. The industry needs the help of very-long-term exploratory research, publicly funded, in a Bell Labs–like setting or by university researchers with career-long timelines and wider and deeper knowledge in physics, chemistry, biology, and algorithms than corporate research currently allows. This way, humanity will continue to find new transistors and gain the abilities it will need to face the challenges in the centuries ahead.
Move could help restore drying lake, a former resort destination that has deteriorated into an environmental crisis amid drought
The US government said on Monday it will spend up to $250m over four years to help mitigate an environmental health disaster that has been brewing in California’s Salton Sea for nearly two decades.
The inland lake, which is fed by agricultural runoff and wastewater, has slowly been shrinking, exposing a powdery shoreline laced with arsenic, selenium and DDT. Dust from the drying lake has wafted into surrounding communities, exacerbating pollution and consequently respiratory conditions in one of California’s poorest and most environmentally burdened regions.
Continue reading...Racing to wean itself off Russian gas supplies, Germany is set to buy 2m tonnes of liquid gas from Gulf state
German firms have signed a 15-year deal to buy 2m tonnes of liquid gas from Qatar, sending out mixed signals over the priority Germany places on human rights in the Gulf and its commitment to a carbon neutral energy supply.
The deal was announced by state-owned Qatar Energy and deliveries will start from 2026. The gas will be sold by Qatar to the US company ConocoPhillips, which will then deliver it to the LNG terminal in Brunsbüttel, Qatar’s energy minister said in the capital, Doha.
Continue reading...Huge subsidies for US-based low-carbon manufacturers are posing big problems for EU leaders
In a slick General Motors advert aired during last year’s Super Bowl, the actor and comedian Will Ferrell took patriotic umbrage at Norway’s ability to sell more electric vehicles per capita than the US. “Norway’s beating us at EVs!”, Ferrell lamented, before promoting GM’s latest battery technology to the watching millions.
Almost two years on, the angst is being felt on the other side of the Atlantic. Following on from President Joe Biden’s “Buy America” rules for infrastructure, his Inflation Reduction Act (IRA) will deliver, from January, almost $370bn worth of subsidies and tax breaks to US-based companies involved in the transition to a low-carbon economy. Around $50bn will come in the form of tax credits to persuade Americans to buy electric vehicles made in North America (Canada and Mexico were included in the deal after initially being left out).
Continue reading...Readers on how years of poor Tory leadership mean there is no end in sight to the chronic shortage of homes
John Harris dissects key aspects of the housing “crisis” in a typically thoughtful and powerful way (The Tories are tearing themselves apart over housing – but this is another crisis of their own making, 27 November). But on the way he displays a crucial misunderstanding. There is no presumption in favour of development in the planning system; it’s a presumption in favour of sustainable development – something with which surely no one could disagree? This is an egregious example of the Tory use of sophistry that has made a massive contribution to the issue that Harris so ably describes. Far from being an objective, science-based definition, it is in reality a circular argument that the government inserted in the national planning guidance.
In effect, “sustainable” is what the government, Humpty Dumpty-like, says it is. The assessment of major housing proposals, which so often go to appeal, is comically perfunctory, the overriding criterion being the supply of new housing, however and wherever built. Many people participate in this charade. We have been building in unsustainability – carbon emissions, destruction of habitat, poor health and unaffordability – throughout the last 12 years. The cost of retrofitting will be astronomical. We need the houses we need. Campaigners cannot morally deny that, but development must be based on sound sustainability principles and by applying rigorous tests that are available but are never used effectively.
Continue reading...Free allowances ‘in direct contradiction with the polluter pays principle’, WWF report says
Big polluting industries have been given almost €100bn (£86bn) in free carbon permits by the EU in the last nine years, according to an analysis by the WWF. The free allowances are “in direct contradiction with the polluter pays principle”, the group said.
Free pollution permits worth €98.5bn were given to energy-intensive sectors including steel, cement, chemicals and aviation from 2013-21. This is more than the €88.5bn that the EU’s emissions trading scheme (ETS) charged polluters, mostly coal and gas power stations, for their CO2 emissions.
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Mounting evidence of dirty tricks against prospective MPs can’t be dismissed as leftwing sour grapes. We were promised a ‘broad church’
Britain will almost certainly have a Labour government in two years’ time: you have the Tories’ unprecedented self-immolation to thank for that. Debating, then, how Rishi Sunak’s successors will govern is a democratic imperative. To some of Keir Starmer’s more zealous supporters, scrutinising the opposition is an act of treachery that simply makes a Tory government more likely. Welcome to “Schrödinger’s left”: where the left of the party is simultaneously so irrelevant and toxic that it must be marginalised, but so powerful it can help determine the result of general elections.
In his pitch for the Labour leadership, Starmer promised that under his watch the party would be a “broad church”, and that he would restore trust in Labour through “unity”. To underline that this wasn’t just empty rhetoric, he said that the selection of Labour candidates “needs to be more democratic and we should end NEC impositions of candidates. Local party members should select their candidates for every election.” To paraphrase Karl Marx, all that is a Starmer promise melts into air: but this particular issue has political consequences that go far beyond internal Labour politics.
Continue reading...Vanua Levu is being overrun by invasive vines – and the increasing number of natural disasters, brought on by climate change, is only making things worse
In Vanua Levu, the second largest island of Fiji, every contour drips with green. The landscape is impossibly lush and verdant. But upon closer inspection, it’s evident that nearly everything is shrouded in vines.
There are several vine species in Fiji, one of which is the invasive kudzu, introduced by US troops in the second world war as living camouflage for Allied equipment. But, as botanist Judith Sumner, writes: “under tropical Pacific conditions kudzu quickly became an invasive species with a growth rate that aggressively outpaced native Fijian flora.”
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The Big Picture features technology through the lens of photographers.
Every month, IEEE Spectrum selects the most stunning technology images recently captured by photographers around the world. We choose images that reflect an important advance, or a trend, or that are just mesmerizing to look at. We feature all images on our site, and one also appears on our monthly print edition.
Enjoy the latest images, and if you have suggestions, leave a comment below.
An old saw regarding the multitude of dashed hopes about fusion energy’s promise goes “Fusion is 30 years away—and it always will be.” After decades of researchers predicting that fusion was just around the corner, a team at the UK Atomic Energy Authority (which hosts the Joint European Torus [JET] plasma physics experiment) did something that suggests scientists are homing in on exactly which corner that is. In February 2022, the JET experimenters induced the single greatest sustained energy pulse ever created by humans. It had twice the energy of the previous record-setting blast, triggered a quarter century earlier. A doubling every 25 years is far behind the pace of the microchip improvements described by Moore’s Law. But that hasn’t dampened enthusiasm over an alternative energy source that could make fossil fuels and their effect on the environment relics of a bygone era. In the foreground of the picture is a trainee learning how to use the systems involved in accomplishing the feat.
Leon Neal/Getty Images
What has two wings, can reach a person stranded in a disaster zone, and doubles as a source of precious calories when no other food is available? This drone, designed and built by a team of researchers at the Swiss Federal Institute of Technology Lausanne (EPFL), has wings made entirely of laser-cut rice cakes held together with “glue” made from gelatin. The EPFL group says it plans to keep refining the edible aircraft to improve its aeronautics and enhance its nutritional profile.
EPFL
Creating the quantum mechanical state of entanglement (in which paired atoms influence each other from across vast distances) has heretofore been reminiscent of the story of Noah’s ark. The tried-and-true method for entangling photons (by shining light through a nonlinear crystal) puts them in this state two by two, the way the animals are said to have boarded the ark. The ambition of quantum researchers has been to expand these connections from pairs to parties. And it seems they’ve figured out how to reliably entangle multiple photons in a complicated web, using half-millimeter-thick metasurfaces covered with forests of microscopic pillars. This, say experts, will not only greatly simplify the setup needed for quantum technology but also help support more-complex quantum applications.
Craig Fritz
In a world obsessed with miniaturization, it’s almost shocking when, every now and then, a big deal is made of something, er, big. That is certainly the case with the new camera being built for the Vera C. Rubin Observatory in Chile. When the camera is delivered and set up in May 2023, its 1.57-meter-wide lens will make it the world’s largest device for taking snapshots. The gargantuan point-and-shoot instrument will capture images of a swath of the sky seven times the width of the moon.
Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory
When we’re carrying out our quotidian activities, most of us rarely stop to think about what marvels of engineering our arms and hands are. But for those who have lost the use of a limb—or, like Britt Young, the woman pictured here, were born without one—there’s hardly ever a day when the challenges of navigating a two-handed world are not in the forefront of their thoughts. In Young’s October 2022 IEEE Spectrum cover story, she discusses these challenges, as well as how the bionic-hand technology intended to come to the rescue falls short of designers’ and users’ expectations.
Gabriela Hasbun. Makeup: Maria Nguyen for Mac Cosmetics; Hair: Joan Laqui for Living Proof
As climate change edges from crisis to emergency, the aviation sector looks set to miss its 2050 goal of net-zero emissions. In the five years preceding the pandemic, the top four U.S. airlines—American, Delta, Southwest, and United—saw a 15 percent increase in the use of jet fuel. Despite continual improvements in engine efficiencies, that number is projected to keep rising.
A glimmer of hope, however, comes from solar fuels. For the first time, scientists and engineers at the Swiss Federal Institute of Technology (ETH) in Zurich have reported a successful demonstration of an integrated fuel-production plant for solar kerosene. Using concentrated solar energy, they were able to produce kerosene from water vapor and carbon dioxide directly from air. Fuel thus produced is a drop-in alternative to fossil-derived fuels and can be used with existing storage and distribution infrastructures, and engines.
Fuels derived from synthesis gas (or syngas)—an intermediate product that is a specific mixture of carbon monoxide and hydrogen—is a known alternative to conventional, fossil-derived fuels. Syngas is produced by Fischer-Tropsch (FT) synthesis, in which chemical reactions convert carbon monoxide and water vapor into hydrocarbons. The team of researchers at ETH found that a solar-driven thermochemical method to split water and carbon dioxide using a metal oxide redox cycle can produce renewable syngas. They demonstrated the process in a rooftop solar refinery at the ETH Machine Laboratory in 2019.
Reticulated porous structure made of ceria used in the solar reactor to thermochemically split CO2 and H2O and produce syngas, a specific mixture of H2 and CO.ETH Zurich
The current pilot-scale solar tower plant was set up at the IMDEA Energy Institute in Spain. It scales up the solar reactor of the 2019 experiment by a factor of 10, says Aldo Steinfeld, an engineering professor at ETH who led the study. The fuel plant brings together three subsystems—the solar tower concentrating facility, solar reactor, and gas-to-liquid unit.
First, a heliostat field made of mirrors that rotate to follow the sun concentrates solar irradiation into a reactor mounted on top of the tower. The reactor is a cavity receiver lined with reticulated porous ceramic structures made of ceria (or cerium(IV) oxide). Within the reactor, the concentrated sunlight creates a high-temperature environment of about 1,500 °C which is hot enough to split captured carbon dioxide and water from the atmosphere to produce syngas. Finally, the syngas is processed to kerosene in the gas-to-liquid unit. A centralized control room operates the whole system.
Fuel produced using this method closes the fuel carbon cycle as it only produces as much carbon dioxide as has gone into its manufacture. “The present pilot fuel plant is still a demonstration facility for research purposes,” says Steinfeld, “but it is a fully integrated plant and uses a solar-tower configuration at a scale that is relevant for industrial implementation.”
“The solar reactor produced syngas with selectivity, purity, and quality suitable for FT synthesis,” the authors noted in their paper. They also reported good material stability for multiple consecutive cycles. They observed a value of 4.1 percent solar-to-syngas energy efficiency, which Steinfeld says is a record value for thermochemical fuel production, even though better efficiencies are required to make the technology economically competitive.
A heliostat field concentrates solar radiation onto a solar reactor mounted on top of the solar tower. The solar reactor cosplits water and carbon dioxide and produces a mixture of molecular hydrogen and carbon monoxide, which in turn is processed to drop-in fuels such as kerosene.ETH Zurich
“The measured value of energy conversion efficiency was obtained without any implementation of heat recovery,” he says. The heat rejected during the redox cycle of the reactor accounted for more than 50 percent of the solar-energy input. “This fraction can be partially recovered via thermocline heat storage. Thermodynamic analyses indicate that sensible heat recovery could potentially boost the energy efficiency to values exceeding 20 percent.”
To do so, more work is needed to optimize the ceramic structures lining the reactor, something the ETH team is actively working on, by looking at 3D-printed structures for improved volumetric radiative absorption. “In addition, alternative material compositions, that is, perovskites or aluminates, may yield improved redox capacity, and consequently higher specific fuel output per mass of redox material,” Steinfeld adds.
The next challenge for the researchers, he says, is the scale-up of their technology for higher solar-radiative power inputs, possibly using an array of solar cavity-receiver modules on top of the solar tower.
To bring solar kerosene into the market, Steinfeld envisages a quota-based system. “Airlines and airports would be required to have a minimum share of sustainable aviation fuels in the total volume of jet fuel that they put in their aircraft,” he says. This is possible as solar kerosene can be mixed with fossil-based kerosene. This would start out small, as little as 1 or 2 percent, which would raise the total fuel costs at first, though minimally—adding “only a few euros to the cost of a typical flight,” as Steinfeld puts it
Meanwhile, rising quotas would lead to investment, and to falling costs, eventually replacing fossil-derived kerosene with solar kerosene. “By the time solar jet fuel reaches 10 to 15 percent of the total jet-fuel volume, we ought to see the costs for solar kerosene nearing those of fossil-derived kerosene,” he adds.
However, we may not have to wait too long for flights to operate solely on solar fuel. A commercial spin-off of Steinfeld’s laboratory, Synhelion, is working on commissioning the first industrial-scale solar fuel plant in 2023. The company has also collaborated with the airline SWISS to conduct a flight solely using its solar kerosene.
The 100th anniversary of the invention of the transistor will happen in 2047. What will transistors be like then? Will they even be the critical computing element they are today? IEEE Spectrum asked experts from around the world for their predictions.
Expect transistors to be even more varied than they are now, says one expert. Just as processors have evolved from CPUs to include GPUs, network processors, AI accelerators, and other specialized computing chips, transistors will evolve to fit a variety of purposes. “Device technology will become application domain–specific in the same way that computing architecture has become application domain–specific,” says H.-S. Philip Wong, an IEEE Fellow, professor of electrical engineering at Stanford University, and former vice president of corporate research at TSMC.
Despite the variety, the fundamental operating principle—the field effect that switches transistors on and off—will likely remain the same, suggests Suman Datta, an IEEE Fellow, professor of electrical and computer at Georgia Tech, and director of the multi-university nanotech research center ASCENT. This device will likely have minimum critical dimensions of 1 nanometer or less, enabling device densities of 10 trillion per square centimeter, says Tsu-Jae King Liu, an IEEE Fellow, dean of the college of engineering at the University of California, Berkeley, and a member of Intel’s board of directors.
"It is safe to assume that the transistor or switch architectures of 2047 have already been demonstrated on a lab scale"—Sri Samavedam
Experts seem to agree that the transistor of 2047 will need new materials and probably a stacked or 3D architecture, expanding on the planned complementary field-effect transistor (CFET, or 3D-stacked CMOS). [For more on the CFET, see "Taking Moore's Law to New Heights."] And the transistor channel, which now runs parallel to the plane of the silicon, may need to become vertical in order to continue to increase in density, says Datta.
AMD senior fellow Richard Schultz, suggests that the main aim in developing these new devices will be power. “The focus will be on reducing power and the need for advanced cooling solutions,” he says. “Significant focus on devices that work at lower voltages is required.”
It’s hard to imagine a world where computing is not done with transistors, but, of course, vacuum tubes were once the digital switch of choice. Startup funding for quantum computing, which does not directly rely on transistors, reached US $1.4 billion in 2021, according to McKinsey & Co.
But advances in quantum computing won’t happen fast enough to challenge the transistor by 2047, experts in electron devices say. “Transistors will remain the most important computing element,” says Sayeef Salahuddin, an IEEE Fellow and professor of electrical engineering and computer science at the University of California, Berkeley. “Currently, even with an ideal quantum computer, the potential areas of application seem to be rather limited compared to classical computers.”
Sri Samavedam, senior vice president of CMOS technologies at the European chip R&D center Imec, agrees. “Transistors will still be very important computing elements for a majority of the general-purpose compute applications,” says Samavedam. “One cannot ignore the efficiencies realized from decades of continuous optimization of transistors.”
Twenty-five years is a long time, but in the world of semiconductor R&D, it’s not that long. “In this industry, it usually takes about 20 years from [demonstrating a concept] to introduction into manufacturing,” says Samavedam. “It is safe to assume that the transistor or switch architectures of 2047 have already been demonstrated on a lab scale” even if the materials involved won’t be exactly the same. King Liu, who demonstrated the modern FinFET about 25 years ago with colleagues at Berkeley, agrees.
But the idea that the transistor of 2047 is already sitting in a lab somewhere isn’t universally shared. Salahuddin, for one, doesn’t think it’s been invented yet. “But just like the FinFET in the 1990s, it is possible to make a reasonable prediction for the geometric structure” of future transistors, he says.
AMD’s Schultz says you can glimpse this structure in proposed 3D-stacked devices made of 2D semiconductors or carbon-based semiconductors. “Device materials that have not yet been invented could also be in scope in this time frame,” he adds.
Experts say that the heart of most devices, the transistor channel region, will still be silicon, or possibly silicon-germanium—which is already making inroads—or germanium. But in 2047 many chips may use semiconductors that are considered exotic today. These could include oxide semiconductors like indium gallium zinc oxide; 2D semiconductors, such as the metal dichalcogenide tungsten disulfide; and one-dimensional semiconductors, such as carbon nanotubes. Or even “others yet to be invented,” says Imec’s Samavedam.
"Transistors will remain the most important computing element"—Sayeef Salahuddin
Silicon-based chips may be integrated in the same package with chips that rely on newer materials, just as processor makers are today integrating chips using different silicon manufacturing technologies into the same package, notes IEEE Fellow Gabriel Loh, a senior fellow at AMD.
Which semiconductor material is at the heart of the device may not even be the central issue in 2047. “The choice of channel material will essentially be dictated by which material is the most compatible with many other materials that form other parts of the device,” says Salahuddin. And we know a lot about integrating materials with silicon.
Everywhere. No, seriously. Experts really do expect some amount of intelligence and sensing to creep into every aspect of our lives. That means devices will be attached to our bodies and implanted inside them; embedded in all kinds of infrastructure, including roads, walls, and houses; woven into our clothing; stuck to our food; swaying in the breeze in grain fields; watching just about every step in every supply chain; and doing many other things in places nobody has thought of yet.
Transistors will be “everywhere that needs computation, command and control, communications, data collection, storage and analysis, intelligence, sensing and actuation, interaction with humans, or an entrance portal to the virtual and mixed reality world,” sums up Stanford’s Wong.
This article appears in the December 2022 print issue as “The Transistor of 2047.”
With the deadly devastation fresh in the world’s mind, Pakistan pushed for damage funds with other frontline countries
In early September, after unprecedented rainfall had left a third of Pakistan under water, its climate change minister set out the country’s stall for Cop27. “We are on the frontline and intend to keep loss and damage and adapting to climate catastrophes at the core of our arguments and negotiations. There will be no moving away from that,” Sherry Rehman said.
Pakistan brought that resolve to the negotiations in Sharm el-Sheikh and, as president of the G77 plus China negotiating bloc, succeeded in keeping developing countries united on loss and damage – despite efforts by some rich countries to divide them. Its chief negotiator, Nabeel Munir, a career diplomat, was backed by a team of savvy veteran negotiators who had witnessed the devastation and suffering from the floods, which caused $30bn (£25bn) of damage and economic losses. Every day, Munir repeated the same message: “Loss and damage is not charity, it’s about climate justice.”
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“Energy and information are two basic currencies of organic and social systems,” the economics Nobelist Herb Simon once
observed. A new technology that alters the terms on which one or the other of these is available to a system can work on it the most profound changes.”
Electric vehicles at scale alter the terms of both basic currencies concurrently. Reliable, secure supplies of minerals and software are core elements for EVs, which represent a “shift from a fuel-intensive to a material-intensive energy system,” according to a report by the International Energy Agency (IEA). For example, the mineral requirements for an EV’s batteries and electric motors are six times that of an internal-combustion-engine (ICE) vehicle, which can increase the average weight of an EV by 340 kilograms (750 pounds). For something like the Ford Lightning, the weight can be more than twice that amount.
EVs also create a shift from an electromechanical-intensive to an information-intensive vehicle. EVs offer a virtual clean slate from which to accelerate the design of safe, software-defined vehicles, with computing and supporting electronics being the prime enabler of a vehicle’s features, functions, and value. Software also allows for the decoupling of the internal mechanical connections needed in an ICE vehicle, permitting an EV to be controlled remotely or autonomously. An added benefit is that the loss of the ICE power train not only reduces the components a vehicle requires but also frees up space for increased passenger comfort and storage.
The effects of Simon’s profound changes are readily apparent, forcing a 120-year-old industry to fundamentally reinvent itself. EVs require automakers to design new manufacturing processes and build plants to make both EVs and their batteries. Ramping up the battery supply chain is the automakers’ current “most challenging topic,” according to VW chief financial officer Arno Antlitz.
It can take five or more years to get a lithium mine up and going, but operations can start only after it has secured the required permits, a process that itself can take years.
These plants are also very expensive. Ford and its Korean battery supplier SK Innovation are spending US $5.6 billion to produce F-Series EVs and batteries in Stanton, Tenn., for example, while GM is spending $2 billion to produce its new Cadillac Lyriq EVs in Spring Hill, Tenn. As automakers expand their lines of EVs, tens of billions more will need to be invested in both manufacturing and battery plants. It is little wonder that Tesla CEO Elon Musk calls EV factories “gigantic money furnaces.”
Furthermore, Kristin Dziczek a policy analyst with the Federal Reserve Bank of Chicago adds, there are scores of new global EV competitors actively seeking to replace the legacy automakers. The “simplicity” of EVs in comparison with ICE vehicles allows these disruptors to compete virtually from scratch with legacy automakers, not only in the car market itself but for the material and labor inputs as well.
Another critical question is whether all the planned battery-plant output will support expected EV production demands. For instance, the United States will require 8 million EV batteries annually by 2030 if its target to make EVs half of all new-vehicle sales is met, with that number rising each year after. As IEA executive director Fatih Birol observes, “Today, the data shows a looming mismatch between the world’s strengthened climate ambitions and the availability of critical minerals that are essential to realizing those ambitions.”
This mismatch worries automakers. GM, Ford, Tesla, and others have moved to secure batteries through 2025, but it could be tricky after that. Rivian Automotive chief executive RJ Scaringe was recently quoted in the Wall Street Journal as saying that “90 to 95 percent of the (battery) supply chain does not exist,” and that the current semiconductor chip shortage is “a small appetizer to what we are about to feel on battery cells over the next two decades.”
The competition for securing raw materials, along with the increased consumer demand, has caused EV prices to spike. Ford has raised the price of the Lightning $6,000 to $8,500, and CEO Jim Farley bluntly states that in regard to material shortages in the foreseeable future, “I don’t think we should be confident in any other outcomes than an increase in prices.”
One critical area of resource competition is over the limited supply of software and systems engineers with the mechatronics and robotics expertise needed for EVs. Major automakers have moved aggressively to bring more software and systems-engineering expertise on board, rather than have it reside at their suppliers, as they have traditionally done. Automakers feel that if they’re not in control of the software, they’re not in control of their product.
Volvo’s CEO Jim Rowan stated earlier this year that increasing the computing power in EVs will be harder and more altering of the automotive industry than switching from ICE vehicles to EVs. This means that EV winners and losers will in great part be separated by their “relative strength in their cyberphysical systems engineering,” states Clemson’s Paredis.
Even for the large auto suppliers, the transition to EVs will not be an easy road. For instance, automakers are demanding these suppliers absorb more cost cuts because automakers are finding EVs so expensive to build. Not only do automakers want to bring cutting-edge software expertise in-house, they want greater inside expertise in critical EV supply-chain components, especially batteries.
Automakers, including Tesla, are all scrambling for battery talent, with bidding wars reportedly breaking out to acquire top candidates. With automakers planning to spend more than $13 billion to build at least 13 new EV battery plants in North America within the next five to seven years, experienced management and production-line talent will likely be in extremely short supply. Tesla’s Texas Gigafactory needs some 10,000 workers alone, for example. With at least 60 new battery plants planned to be in operation globally by 2030, and scores needed soon afterward, major battery makers are already highlighting their expected skill shortages.
The underlying reason for the worry: Supplying sufficient raw materials to existing and planned battery plants as well as to the manufacturers of other renewable energy sources and military systems—who are competing for the same materials—has several complications to overcome. Among them is the need for more mines to provide the metals required, which have spiked in price as demand has increased. For example, while demand for lithium is growing rapidly, investment in mines has significantly lagged the investment that has been aimed toward EVs and battery plants. It can take five or more years to get a lithium mine up and going, but operations can start only after it has secured the required permits, a process that itself can take years.
Mining the raw materials, of course, assumes that there is sufficient refining capability to process them, which, outside of China, is limited. This is especially true in the United States, which, according to a Biden Administration special supply-chain investigative report, has “limited raw material production capacity and virtually no processing capacity.” Consequently, the report states, the United States “exports the limited raw materials produced today to foreign markets.” For example, output from the only nickel mine in the United States, the Eagle mine in Minnesota, is sent to Canada for smelting.
“Energy and information are two basic currencies of organic and social systems. A new technology that alters the terms on which one or the other of these is available to a system can work on it the most profound changes.” —Herb Simon
One possible solution is to move away from lithium-ion batteries and nickel metal hydride batteries to other battery chemistries such as lithium-iron phosphate, lithium-ion phosphate, lithium-sulfur, lithium-metal, and sodium-ion, among many others, not to mention solid-state batteries, as a way to alleviate some of the material supply and cost problems. Tesla is moving toward the use of lithium-iron phosphate batteries, as is Ford for some of its vehicles. These batteries are cobalt free, which alleviates several sourcing issues.
Another solution may be recycling both EV batteries as well as the waste and rejects from battery manufacturing, which can run between 5 to 10 percent of production. Effective recycling of EV batteries “has the potential to reduce primary demand compared to total demand in 2040, by approximately 25 percent for lithium, 35 percent for cobalt and nickel, and 55 percent for copper,” according to a report by the University of Sidney’s Institute for Sustainable Futures.
While investments into creating EV battery recycling facilities have started, there is a looming question of whether there will be enough battery factory scrap and other lithium-ion battery waste for them to remain operational while they wait for sufficient numbers of batteries to make them profitable. Lithium-ion battery-pack recycling is very time-consuming and expensive, making mining lithium often cheaper than recycling it, for example. Recycling low or no-cobalt lithium batteries, which is the direction many automakers are taking, may also make it unprofitable to recycle them.
An additional concern is that EV batteries, once no longer useful for propelling the EV, have years of life left in them. They can be refurbished, rebuilt, and reused in EVs, or repurposed into storage devices for homes, businesses, or the grid. Whether it will make economic sense to do either at scale versus recycling them remains to be seen.
Howard Nusbaum, the administrator of the National Salvage Vehicle Reporting Program (NSVRP), succinctly puts it, “There is no recycling, and no EV-recycling industry, if there is no economic basis for one.”
In the next article in the series, we will look at whether the grid can handle tens of millions of EVs.
The global business landscape is constantly evolving. Digital transformation— compounded by the challenges of globalization, supply-chain stability, demographic shifts, and climate change—is pressuring companies and government agencies to innovate and safely deploy sustainable technologies.
As digital transformation continues, the pervasive growth of technology increasingly intersects with industry, government, and societal interests. Companies and organizations need access to technologies that can enhance efficiencies, productivity, and competitive advantage.
Governments seek influence over emerging technologies to preserve economic interests, advance global trade, and protect their citizens. Consumers are demanding more transparency regarding organizational motives, practices, and processes.
For those and other reasons, new types of stakeholders are seeking a voice in the technology standardization process.
The need is evidenced in the membership gains at the IEEE Standards Association. IEEE SA membership for organizations, also known as entity membership, has increased by more than 150 percent in the past six years. Academic institutions, government agencies, and other types of organizations now account for more than 30 percent of the member base.
Entity membership offers the ability to help shape technology development and ensure your organization’s interests are represented in the standards development process. Other benefits include balloting privileges, leadership eligibility, and networking opportunities.
IEEE SA welcomes different types of organizations because they bring varied perspectives and they voice concerns that need to be addressed during the standards development process. Engaging diverse viewpoints from companies of all sizes and types also helps to identify and address changing market needs.
From a geographic standpoint, IEEE SA welcomes participation from all regions of the world. Diverse perspectives and contributions to the development cycle enable innovation to be shared and realized by all stakeholders.
IEEE SA has introduced new industry-engagement programs such as open-source and industry-alliance offerings designed to speed innovation and adoption. In addition, industry participants have access to the full IEEE SA ecosystem of programs and services including technology incubation, pre-standardization work, standards development, and conformity assessment activities. Training and marketing tools support working groups at every stage of the process.
An increasing number of new standards projects from emerging technology areas have created a more robust and diversified portfolio of work. The technologies include artificial intelligence and machine learning, blockchain and distributed ledger technologies, quantum computing, cloud computing, the Internet of Things, smart cities, smart factories and online gaming. There is also more participation from the health care, automotive, and financial services sectors.
IEEE SA has grown and evolved its programs to address market needs, but its purpose has not changed. The organization is focused on empowering innovators to raise the world’s standards for the benefit of humanity.
Those innovators might be individuals or organizations looking to make a difference in the world, but it can be accomplished only when we all work together.
Learn more about IEEE SA membership for organizations and how your organization can play a key role in advancing future technologies.
A rocket built by Indian startup Skyroot has become the country’s first privately developed launch vehicle to reach space, following a successful maiden flight earlier today. The suborbital mission is a major milestone for India’s private space industry, say experts, though more needs to be done to nurture the fledgling sector.
The Vikram-S rocket, named after the founder of the Indian space program, Vikram Sarabhai, lifted off from the Indian Space Research Organization’s (ISRO) Satish Dhawan Space Centre, on India’s east coast, at 11:30 a.m. local time (1 a.m. eastern time). It reached a peak altitude of 89.5 kilometers (55.6 miles), crossing the 80-km line that NASA counts as the boundary of space, but falling just short of the 100 km recognized by the Fédération Aéronautique Internationale.
In the longer run, India’s space industry has ambitions of capturing a significant chunk of the global launch market.
Pawan Kumar Chandana, cofounder of the Hyderabad-based startup, says the success of the launch is a major victory for India’s nascent space industry, but the buildup to the mission was nerve-racking. “We were pretty confident on the vehicle, but, as you know, rockets are very notorious for failure,” he says. “Especially in the last 10 seconds of countdown, the heartbeat was racing up. But once the vehicle had crossed the launcher and then went into the stable trajectory, I think that was the moment of celebration.”
At just 6 meters (20 feet) long and weighing only around 550 kilograms (0.6 tonnes), the Vikram-S is not designed for commercial use. Today’s mission, called Prarambh, which means “the beginning” in Sanskrit, was designed to test key technologies that will be used to build the startup’s first orbital rocket, the Vikram I. The rocket will reportedly be capable of lofting as much as 480 kg up to an 500-km altitude and is slated for a maiden launch next October.
Skyroot cofounder Pawan Kumar Chandana standing in front of the Vikram-S rocket at the Satish Dhawan Space Centre, on the east coast of India.Skyroot
In particular, the mission has validated Skyroot’s decision to go with a novel all-carbon fiber structure to cut down on weight, says Chandana. It also allowed the company to test 3D-printed thrusters, which were used for spin stabilization in Vikram-S but will power the upper stages of its later rockets. Perhaps the most valuable lesson, though, says Chandana, was the complexity of interfacing Skyroot's vehicle with ISRO’s launch infrastructure. “You can manufacture the rocket, but launching it is a different ball game,” he says. “That was a great learning experience for us and will really help us accelerate our orbital vehicle.”
Skyroot is one of several Indian space startups looking to capitalize on recent efforts by the Indian government to liberalize its highly regulated space sector. Due to the dual-use nature of space technology, ISRO has historically had a government-sanctioned monopoly on most space activities, says Rajeswari Pillai Rajagopalan, director of the Centre for Security, Strategy and Technology at the Observer Research Foundation think tank, in New Delhi. While major Indian engineering players like Larsen & Toubro and Godrej Aerospace have long supplied ISRO with components and even entire space systems, the relationship has been one of a supplier and vendor, she says.
But in 2020, Finance Minister Nirmala Sitharaman announced a series of reforms to allow private players to build satellites and launch vehicles, carry out launches, and provide space-based services. The government also created the Indian National Space Promotion and Authorisation Centre (InSpace), a new agency designed to act as a link between ISRO and the private sector, and affirmed that private companies would be able to take advantage of ISRO’s facilities.
The first launch of a private rocket from an ISRO spaceport is a major milestone for the Indian space industry, says Rajagopalan. “This step itself is pretty crucial, and it’s encouraging to other companies who are looking at this with a lot of enthusiasm and excitement,” she says. But more needs to be done to realize the government’s promised reforms, she adds. The Space Activities Bill that is designed to enshrine the country’s space policy in legislation has been languishing in draft form for years, and without regulatory clarity, it’s hard for the private sector to justify significant investments. “These are big, bold statements, but these need to be translated into actual policy and regulatory mechanisms,” says Rajagopalan.
Skyroot’s launch undoubtedly signals the growing maturity of India’s space industry, says Saurabh Kapil, associate director in PwC’s space practice. “It’s a critical message to the Indian space ecosystem, that we can do it, we have the necessary skill set, we have those engineering capabilities, we have those manufacturing or industrialization capabilities,” he says.
The Vikram-S rocket blasting off from the Satish Dhawan Space Centre, on the east coast of India.Skyroot
However, crossing this technical milestone is only part of the challenge, he says. The industry also needs to demonstrate a clear market for the kind of launch vehicles that companies like Skyroot are building. While private players are showing interest in launching small satellites for applications like agriculture and infrastructure monitoring, he says, these companies will be able to build sustainable businesses only if they are allowed to compete for more lucrative government and defense-sector contacts.
In the longer run, though, India’s space industry has ambitions of capturing a significant chunk of the global launch market, says Kapil. ISRO has already developed a reputation for both reliability and low cost—its 2014 mission to Mars cost just US $74 million, one-ninth the cost of a NASA Mars mission launched the same week. That is likely to translate to India’s private space industry, too, thanks to a considerably lower cost of skilled labor, land, and materials compared with those of other spacefaring nations, says Kapil. “The optimism is definitely there that because we are low on cost and high on reliability, whoever wants to build and launch small satellites is largely going to come to India,” he says.
Collisions with birds are a serious problem for commercial aircraft, costing the industry billions of dollars and killing thousands of animals every year. New research shows that a robotic imitation of a peregrine falcon could be an effective way to keep them out of flight paths.
Worldwide, so-called birdstrikes are estimated to cost the civil aviation industry almost US $1.4 billion annually. Nearby habitats are often deliberately made unattractive to birds, but airports also rely on a variety of deterrents designed to scare them away, such as loud pyrotechnics or speakers that play distress calls from common species.
However, the effectiveness of these approaches tends to decrease over time, as the birds get desensitized by repeated exposure, says Charlotte Hemelrijk, a professor on the faculty of science and engineering at the University of Groningen, in the Netherlands. Live hawks or blinding lasers are also sometimes used to disperse flocks, she says, but this is controversial as it can harm the animals, and keeping and training falcons is not cheap.
“The birds don’t distinguish [RobotFalcon] from a real falcon, it seems.”
—Charlotte Hemelrijk, University of Groningen
In an effort to find a more practical and lasting solution, Hemelrijk and colleagues designed a robotic peregrine falcon that can be used to chase flocks away from airports. The device is the same size and shape as a real hawk, and its fiberglass and carbon-fiber body has been painted to mimic the markings of its real-life counterpart.
Rather than flapping like a bird, the RobotFalcon relies on two small battery-powered propellers on its wings, which allows it to travel at around 30 miles per hour for up to 15 minutes at a time. A human operator controls the machine remotely from a hawk’s-eye perspective via a camera perched above the robot’s head.
To see how effective the RobotFalcon was at scaring away birds, the researchers tested it against a conventional quadcopter drone over three months of field testing, near the Dutch city of Workum. They also compared their results to 15 years of data collected by the Royal Netherlands Air Force that assessed the effectiveness of conventional deterrence methods such as pyrotechnics and distress calls.
Flock-herding Falcon Drone Patrols Airport Flight Paths youtu.be
In a paper published in the Journal of the Royal Society Interface, the team showed that the RobotFalcon cleared fields of birds faster and more effectively than the drone. It also kept birds away from fields longer than distress calls, the most effective of the conventional approaches.
There was no evidence of birds getting habituated to the RobotFalcon over three months of testing, says Hemelrijk, and the researchers also found that the birds exhibited behavior patterns associated with escaping from predators much more frequently with the robot than with the drone. “The way of reacting to the RobotFalcon is very similar to the real falcon,” says Hemelrijk. “The birds don’t distinguish it from a real falcon, it seems.”
Other attempts to use hawk-imitating robots to disperse birds have had less promising results, though. Morgan Drabik-Hamshare, a research wildlife biologist at the DoA, and her colleagues published a paper in Scientific Reports last year that described how they pitted a robotic peregrine falcon with flapping wings against a quadcopter and a fixed-wing remote-controlled aircraft.
They found the robotic falcon was the least effective of the three at scaring away turkey vultures, with the quadcopter scaring the most birds off and the remote-controlled plane eliciting the quickest response. “Despite the predator silhouette, the vultures did not perceive the predator UAS [unmanned aircraft system] as a threat,” Drabik-Hamshare wrote in an email.
Zihao Wang, an associate lecturer at the University of Sydney, in Australia, who develops UAS for bird deterrence, says the RobotFalcon does seem to be effective at dispersing flocks. But he points out that its wingspan is nearly twice the diagonal length of the quadcopter it was compared with, which means it creates a much larger silhouette when viewed from the birds’ perspective. This means the birds could be reacting more to its size than its shape, and he would like to see the RobotFalcon compared with a similar size drone in the future.
The unique design also means the robot requires an experienced and specially trained operator, Wang adds, which could make it difficult to roll out widely. A potential solution could be to make the system autonomous, he says, but it’s unclear how easy this would be.
Hemelrijk says automating the RobotFalcon is probably not feasible, both due to strict regulations around the use of autonomous drones near airports as well as the sheer technical complexity. Their current operator is a falconer with significant experience in how hawks target their prey, she says, and creating an autonomous system that could recognize and target bird flocks in a similar way would be highly challenging.
But while the need for skilled operators is a limitation, Hemelrijk points out that most airports already have full-time staff dedicated to bird deterrence, who could be trained. And given the apparent lack of habituation and the ability to chase birds in a specific direction—so that they head away from runways—she thinks the robotic falcon could be a useful addition to their arsenal.
One by one, the grim scenarios climate scientists had outlined for the near future have been overtaken by events: extreme storms, droughts, floods and ice-sheet collapses whose sudden appearances have outstripped researchers’ worst predictions. Catastrophic climate change is happening more rapidly and with greater intensity than their grimmest warnings, it transpires.
With the 2022 global climate summit Cop 27 upon us, the Guardian looks back at how the climate crisis has affected communities around the world since the last meeting in Glasgow in 2021
Is natural gas renewable? Is it a fossil fuel? A casual google search for natural gas gives the impression that these questions are somehow up for debate. And while natural gas has helped reduce carbon emissions as it was widely adopted as a replacement for coal, it is now up against zero-emission energy such as wind and solar. So how did natural gas end up in the same bracket as renewables? Josh Toussaint-Strauss explores the lengths fossil fuel companies have gone to in order to try to convince consumers, voters and lawmakers that natural gas is somehow a clean energy source
Continue reading...Go at your own pace as you travel the path less followed – spend a morning foraging for lunch, learn to knit in Shetland or try aurora borealis hunting in Orkney this autumn and winter
Push those pedals on the Isles of Arran and Cumbrae
Get on your bike. Seriously, that’s the best way to see the small – yet accessible – island of Cumbrae, just off the Ayrshire coast near Largs. At only four miles long and two miles wide, anyone can enjoy a gentle cycle around this island. We say “anyone” because it’s completely flat, so there are no excuses, really. Sleep it off in one of Jack’s Alt-Stays’ eco-cabins, opening this autumn and, in return for your booking, the business will plant five trees to offset its carbon footprint.
Across the water on Arran, you can tour the island without pushing any pedals. Jump in one of Mogabout’s 4x4 trucks and be driven through forests and on to deserted beaches before pulling up at the Lagg Distillery for a well-earned dram.
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Planning for the return journey is an integral part of the preparations for a crewed Mars mission. Astronauts will require a total mass of about 50 tonnes of rocket propellent for the ascent vehicle that will lift them off the planet’s surface, including 31 tonnes of oxygen approximately. The less popular option is for crewed missions to carry the required oxygen themselves. But scientists are optimistic that it could instead be produced from the carbon dioxide–rich Martian atmosphere itself, using a system called MOXIE.
The Mars Oxygen ISRU (In-Situ Resource Utilization) Experiment is an 18-kilogram unit housed within the Perseverance rover on Mars. The unit is “the size of a toaster,” adds Jeffrey Hoffman, professor of aerospace engineering at MIT. Its job is to electrochemically break down carbon dioxide collected from the Martian atmosphere into oxygen and carbon monoxide. It also tests the purity of the oxygen.
Between February 2021, when it arrived on Mars aboard the Perseverance, and the end of the year, MOXIE has had several successful test runs. According to a review of the system by Hoffman and colleagues, published in Science Advances, it has demonstrated its ability to produce oxygen during both night and day, when temperatures can vary by over 100 ºC. The generation and purity rates of oxygen also meet requirements to produce rocket propellent and for breathing. The authors assert that a scaled-up version of MOXIE could produce the required oxygen for lift-off as well as for the astronauts to breathe.
Next question: How to power any oxygen-producing factories that NASA can land on Mars? Perhaps via NASA’s Kilopower fission reactors?
MOXIE is a first step toward a much larger and more complex system to support the human exploration of Mars. The researchers estimate a required generation rate of 2 to 3 kilograms per hour, compared with the current MOXIE rate of 6 to 8 grams per hour, to produce enough oxygen for lift-off for a crew arriving 26 months later. “So we’re talking about a system that’s a couple of hundred times bigger than MOXIE,” Hoffman says.
They calculate this rate accounting for eight months to get to Mars, followed by some time to set up the system. “We figure you'd probably have maybe 14 months to make all the oxygen.” Further, he says, the produced oxygen would have to be liquefied to be used a rocket propellant, something the current version of MOXIE doesn’t do.
MOXIE also currently faces several design constraints because, says Hoffman, a former astronaut, “our only ride to Mars was inside the Perseverance rover.” This limited the amount of power available to operate the unit, the amount of heat they could produce, the volume and the mass.
“MOXIE does not work nearly as efficiently as a stand-alone system that was specifically designed would,” says Hoffman. Most of the time, it’s turned off. “Every time we want to make oxygen, we have to heat it up to 800 ºC, so most of the energy goes into heating it up and running the compressor, whereas in a well-designed stand-alone system, most of the energy will go into the actual electrolysis, into actually producing the oxygen.”
However, there are still many kinks to iron out for the scaling-up process. To begin with, any oxygen-producing system will need lots of power. Hoffman thinks nuclear power is the most likely option, maybe NASA’s Kilopower fission reactors. The setup and the cabling would certainly be challenging, he says. “You’re going to have to launch to all of these nuclear reactors, and of course, they’re not going to be in exactly the same place as the [other] units,” he says. "So, robotically, you’re going to have to connect to the electrical cables to bring power to the oxygen-producing unit.”
Then there is the solid oxide electrolysis units, which Hoffman points out are carefully machined systems. Fortunately, the company that makes them, OxEon, has already designed, built, and tested a full-scale unit, a hundred times bigger than the one on MOXIE. “Several of those units would be required to produce oxygen at the quantities that we need,” Hoffman says.
He also adds that at present, there is no redundancy built into MOXIE. If any part fails, the whole system dies. “If you’re counting on a system to produce oxygen for rocket propellant and for breathing, you need very high reliability, which means you’re going to need quite a few redundant units.”
Moreover, the system has to be pretty much autonomous, Hoffman says. “It has to be able to monitor itself, run itself.” For testing purposes, every time MOXIE is powered up, there is plenty of time to plan. A full-scale MOXIE system, though, would have to run continuously, and for that it has to be able to adjust automatically to changes in the Mars atmosphere, which can vary by a factor of two over a year, and between nighttime and daytime temperature differences.
For a deep dive into the engineering behind the James Webb Space Telescope, see our collection of posts here.
“Build something that will absolutely, positively work.” This was the mandate from NASA for designing and building the James Webb Space Telescope—at 6.5 meters wide the largest space telescope in history. Last December, JWST launched famously and successfully to its observing station out beyond the moon. And now according to NASA, as soon as next week, the JWST will at long last begin releasing scientific images and data.
Mark Kahan, on JWST’s product integrity team, recalls NASA’s engineering challenge as a call to arms for a worldwide team of thousands that set out to create one of the most ambitious scientific instruments in human history. Kahan—chief electro-optical systems engineer at Mountain View, Calif.–based Synopsys—and many others in JWST’s “pit crew” (as he calls the team) drew hard lessons from three decades ago, having helped repair another world-class space telescope with a debilitating case of flawed optics. Of course the Hubble Space Telescope is in low Earth orbit, and so a special space-shuttle mission to install corrective optics ( as happened in 1993) was entirely possible.
Not so with the JWST.
The meticulous care NASA demanded of JWST’s designers is all the more a necessity because Webb is well out of reach of repair crews. Its mission is to study the infrared universe, and that requires shielding the telescope and its sensors from both the heat of sunlight and the infrared glow of Earth. A good place to do that without getting too far from Earth is an empty patch of interplanetary space 1.5 million kilometers away (well beyond the moon’s orbit) near a spot physicists call the second Lagrange point, or L2.
The pit crew’s job was “down at the detail level, error checking every critical aspect of the optical design,” says Kahan. Having learned the hard way from Hubble, the crew insisted that every measurement on Webb’s optics be made in at least two different ways that could be checked and cross-checked. Diagnostics were built into the process, Kahan says, so that “you could look at them to see what to kick” to resolve any discrepancies. Their work had to be done on the ground, but their tests had to assess how the telescope would work in deep space at cryogenic temperatures.
Superficially, Webb follows the design of all large reflecting telescopes. A big mirror collects light from stars, galaxies, nebulae, planets, comets, and other astronomical objects—and then focuses those photons onto a smaller secondary mirror that sends it to a third mirror that then ultimately directs the light to instruments that record images and spectra.
Webb’s 6.5-meter primary mirror is the first segmented mirror to be launched into space. All the optics had to be made on the ground at room temperature but were deployed in space and operated at 30 to 55 degrees above absolute zero. “We had to develop three new technologies” to make it work, says Lee D. Feinberg of the NASA Goddard Space Flight Center, the optical telescope element manager for Webb for the past 20 years.
The longest wavelengths that Hubble has to contend with were 2.5 micrometers, whereas Webb is built to observe infrared light that stretches to 28 μm in wavelength. Compared with Hubble, whose primary mirror is a circle of an area 4.5 square meters, “[Webb’s primary mirror] had to be 25 square meters,” says Feinberg. Webb also “needed segmented mirrors that were lightweight, and its mass was a huge consideration,” he adds. No single-component mirror that could provide the required resolution would have fit on the Ariane 5 rocket that launched JWST. That meant the mirror would have to be made in pieces, assembled, folded, secured to withstand the stress of launch, then unfolded and deployed in space to create a surface that was within tens of nanometers of the shape specified by the designers.
The James Webb Space Telescope [left] and the Hubble Space Telescope side by side—with Hubble’s 2.4-meter-diameter mirror versus Webb’s array of hexagonal mirrors making a 6.5-meter-diameter light-collecting area. NASA Goddard Space Flight Center
NASA and the U.S. Air Force, which has its own interests in large lightweight space mirrors for surveillance and focusing laser energy, teamed up to develop the technology. The two agencies narrowed eight submitted proposals down to two approaches for building JWST’s mirrors: one based on low-expansion glass made of a mixture of silicon and titanium dioxides similar to that used in Hubble and the other the light but highly toxic metal beryllium. The most crucial issue came down to how well the materials could withstand temperature changes from room temperature on the ground to around 50 K in space. Beryllium won because it could fully release stress after cooling without changing its shape, and it’s not vulnerable to the cracking that can occur in glass. The final beryllium mirror was a 6.5-meter array of 18 hexagonal beryllium mirrors, each weighing about 20 kilograms. The weight per unit area of JWST’s mirror was only 10 percent of that in Hubble. A 100-nanometer layer of pure gold makes the surface reflect 98 percent of incident light from JWST’s main observing band of 0.6 to 28.5 μm. “Pure silver has slightly higher reflectivity than pure gold, but gold is more robust,” says Feinberg. A thin layer of amorphous silica protects the metal film from surface damage.
In addition, a wavefront-sensing control system keeps mirror segment surfaces aligned to within tens of nanometers. Built on the ground, the system is expected to keep mirror alignment stabilized throughout the telescope’s operational life. A backplane kept at a temperature of 35 K holds all 2.4 tonnes of the telescope and instruments rock-steady to within 32 nm while maintaining them at cryogenic temperatures during observations.
The JWST backplane, the “spine” that supports the entire hexagonal mirror structure and carries more than 2,400 kg of hardware, is readied for assembly to the rest of the telescope. NASA/Chris Gunn
Hubble’s amazing, long-exposure images of distant galaxies are possible through the use of gyroscopes and reaction wheels. The gyroscopes are used to sense unwanted rotations, and reaction wheels are used to counteract them.
But the gyroscopes used on Hubble have had a bad track record and have had to be replaced repeatedly. Only three of Hubble’s six gyros remain operational today, and NASA has devised plans for operating with one or two gyros at reduced capability.
Hubble also includes reaction wheels and magnetic torquers, used to maintain its orientation when needed or to point at different parts of the sky.
Webb uses reaction wheels similarly to turn across the sky, but instead of using mechanical gyros to sense direction, it uses hemispherical resonator gyroscopes, which have no moving parts. Webb also has a small fine-steering mirror in the optical path, which can tilt over an angle of just 5 arc seconds. Those very fine adjustments of the light path into the instruments keep the telescope on target. “It’s a really wonderful way to go,” says Feinberg, adding that it compensates for small amounts of jitter without having to move the whole 6-tonne observatory.
Other optics distribute light from the fine-steering mirror among four instruments, two of which can observe simultaneously. Three instruments have sensors that observe wavelengths of 0.6 to 5 μm, which astronomers call the near-infrared. The fourth, called the Mid-InfraRed Instrument (MIRI), observes what astronomers call the mid-infrared spectrum, from 5 to 28.5 μm. Different instruments are needed because sensors and optics have limited wavelength ranges. (Optical engineers may blanch slightly at astronomers’ definitions of what constitutes the near- and mid-infrared wavelength ranges. These two groups simply have differing conventions for labeling the various regimes of the infrared spectrum.)
Mid-infrared wavelengths are crucial for observing young stars and planetary systems and the earliest galaxies, but they also pose some of the biggest engineering challenges. Namely, everything on Earth and planets out to Jupiter glow in the mid-infrared. So for JWST to observe distant astronomical objects, it must avoid recording extraneous mid-infrared noise from all the various sources inside the solar system. “I have spent my whole career building instruments for wavelengths of 5 μm and longer,” says MIRI instrument scientist Alistair Glasse of the Royal Observatory, in Edinburgh. “We’re always struggling against thermal background.”
Mountaintop telescopes can see the near-infrared, but observing the mid-infrared sky requires telescopes in space. However, the thermal radiation from Earth and its atmosphere can cloud their view, and so can the telescopes themselves unless they are cooled far below room temperature. An ample supply of liquid helium and an orbit far from Earth allowed the Spitzer Space Telescope’s primary observing mission to last for five years, but once the last of the cryogenic fluid evaporated in 2009, its observations were limited to wavelengths shorter than 5 μm.
Webb has an elaborate solar shield to block sunlight, and an orbit 1.5 million km from Earth that can keep the telescope to below 55 K, but that’s not good enough for low-noise observations at wavelengths longer than 5 μm. The near-infrared instruments operate at 40 K to minimize thermal noise. But for observations out to 28.5 μm, MIRI uses a specially developed closed-cycle, helium cryocooler to keep MIRI cooled below 7 K. “We want to have sensitivity limited by the shot noise of astronomical sources,” says Glasse. (Shot noise occurs when optical or electrical signals are so feeble that each photon or electron constitutes a detectable peak.) That will make MIRI 1,000 times as sensitive in the mid-infrared as Spitzer.
Another challenge is the limited transparency of optical materials in the mid-infrared. “We use reflective optics wherever possible,” says Glasse, but they also pose problems, he adds. “Thermal contraction is a big deal,” he says, because the instrument was made at room temperature but is used at 7 K. To keep thermal changes uniform throughout MIRI, they made the whole structure of gold-coated aluminum lest other metals cause warping.
Detectors are another problem. Webb’s near-infrared sensors use mercury cadmium telluride photodetectors with a resolution of 2,048 x 2,048 pixels. This resolution is widely used at wavelengths below 5 μm, but sensing at MIRI’s longer wavelengths required exotic detectors that are limited to offering only 1,024 x 1,024 pixels.
Glasse says commissioning “has gone incredibly well.” Although some stray light has been detected, he says, “we are fully expecting to meet all our science goals.”
The near-infrared detectors and optical materials used for observing at wavelengths shorter than 5 μm are much more mature than those for the mid-infrared, so the Near-Infrared Camera (NIRCam) does double duty by both recording images and aligning all the optics in the whole telescope. That alignment was the trickiest part of building the instrument, says NIRCam principal investigator Marcia Rieke of the University of Arizona.
Alignment means getting all the light collected by the primary mirror to get to the right place in the final image. That’s crucial for Webb, because it has 18 separate segments that have to overlay their images perfectly in the final image, and because all those segments were built on the ground at room temperature but operate at cryogenic temperatures in space at zero gravity. When NASA recorded a test image of a single star after Webb first opened its primary mirror, it showed 18 separate bright spots, one from each segment. When alignment was completed on 11 March, the image from NIRcam showed a single star with six spikes caused by diffraction.
Even when performing instrumental calibration tasks, JWST couldn’t help but showcase its stunning sensitivity to the infrared sky. The central star is what telescope technicians used to align JWST’s mirrors. But notice the distant galaxies and stars that photobombed the image too!NASA/STScI
Building a separate alignment system would have added to both the weight and cost of Webb, Rieke realized, and in the original 1995 plan for the telescope she proposed designing NIRCam so it could align the telescope optics once it was up in space as well as record images. “The only real compromise was that it required NIRCam to have exquisite image quality,” says Rieke, wryly. From a scientific point, she adds, using the instrument to align the telescope optics “is great because you know you’re going to have good image quality and it’s going to be aligned with you.” Alignment might be just a tiny bit off for other instruments. In the end, it took a team at Lockheed Martin to develop the computational tools to account for all the elements of thermal expansion.
Escalating costs and delays had troubled Webb for years. But for Feinberg, “commissioning has been a magical five months.” It began with the sight of sunlight hitting the mirrors. The segmented mirror deployed smoothly, and after the near-infrared cameras cooled, the mirrors focused one star into 18 spots, then aligned them to put the spots on top of each other. “Everything had to work to get it to [focus] that well,” he says. It’s been an intense time, but for Feinberg, a veteran of the Hubble repair mission, commissioning Webb was “a piece of cake.”
NASA announced that between May 23rd and 25th, one segment of the primary mirror had been dinged by a micrometeorite bigger than the agency had expected when it analyzed the potential results of such impacts. “Things do degrade over time,” Feinberg said. But he added that Webb had been engineered to minimize damage, and NASA said the event had not affected Webb’s operation schedule.
Corrections 26-28 July 2022: The story was updated a) to reflect the fact that the Lagrange point L2 where Webb now orbits is not that of the "Earth-moon system" (as the story had originally reported) but rather the Earth-sun system
and b) to correct misstatements in the original posting about Webb's hardware for controlling its orientation.
Corrections 12 Aug. 2022: Alistair Glasse's name was incorrectly spelled in a previous version of this story, as was NIRCam (which we'd spelled as NIRcam); Webb's tertiary mirror (we'd originally reported only its primary and secondary mirrors) was also called out in this version.
This article appears in the September 2022 print issue as “Inside the Universe Machine.”
A recent United Nations provision has banned the use of mercury in spacecraft propellant. Although no private company has actually used mercury propellant in a launched spacecraft, the possibility was alarming enough—and the dangers extreme enough—that the ban was enacted just a few years after one U.S.-based startup began toying with the idea. Had the company gone through with its intention to sell mercury propellant thrusters to some of the companies building massive satellite constellations over the coming decade, it would have resulted in Earth’s upper atmosphere being laced with mercury.
Mercury is a neurotoxin. It’s also bio-accumulative, which means it’s absorbed by the body at a faster rate than the body can remove it. The most common way to get mercury poisoning is through eating contaminated seafood. “It’s pretty nasty,” says Michael Bender, the international coordinator of the Zero Mercury Working Group (ZMWG). “Which is why this is one of the very few instances where the governments of the world came together pretty much unanimously and ratified a treaty.”
Bender is referring to the 2013 Minamata Convention on Mercury, a U.N. treaty named for a city in Japan whose residents suffered from mercury poisoning from a nearby chemical factory for decades. Because mercury pollutants easily find their way into the oceans and the atmosphere, it’s virtually impossible for one country to prevent mercury poisoning within its borders. “Mercury—it’s an intercontinental pollutant,” Bender says. “So it required a global treaty.”
Today, the only remaining permitted uses for mercury are in fluorescent lighting and dental amalgams, and even those are being phased out. Mercury is otherwise found as a by-product of other processes, such as the burning of coal. But then a company hit on the idea to use it as a spacecraft propellant.
In 2018, an employee at Apollo Fusion approached the Public Employees for Environmental Responsibility (PEER), a nonprofit that investigates environmental misconduct in the United States. The employee—who has remained anonymous—alleged that the Mountain View, Calif.–based space startup was planning to build and sell thrusters that used mercury propellant to multiple companies building low Earth orbit (LEO) satellite constellations.
Four industry insiders ultimately confirmed that Apollo Fusion was building thrusters that utilized mercury propellant. Apollo Fusion, which was acquired by rocket manufacturing startup Astra in June 2021, insisted that the composition of its propellant mixture should be considered confidential information. The company withdrew its plans for a mercury propellant in April 2021. Astra declined to respond to a request for comment for this story.
Apollo Fusion wasn’t the first to consider using mercury as a propellant. NASA originally tested it in the 1960s and 1970s with two Space Electric Propulsion Tests (SERT), one of which was sent into orbit in 1970. Although the tests demonstrated mercury’s effectiveness as a propellant, the same concerns over the element’s toxicity that have seen it banned in many other industries halted its use by the space agency as well.
“I think it just sort of fell off a lot of folks’ radars,” says Kevin Bell, the staff counsel for PEER. “And then somebody just resurrected the research on it and said, ‘Hey, other than the environmental impact, this was a pretty good idea.’ It would give you a competitive advantage in what I imagine is a pretty tight, competitive market.”
That’s presumably why Apollo Fusion was keen on using it in their thrusters. Apollo Fusion as a startup emerged more or less simultaneously with the rise of massive LEO constellations that use hundreds or thousands of satellites in orbits below 2,000 kilometers to provide continual low-latency coverage. Finding a slightly cheaper, more efficient propellant for one large geostationary satellite doesn’t move the needle much. But doing the same for thousands of satellites that need to be replaced every several years? That’s a much more noticeable discount.
Were it not for mercury’s extreme toxicity, it would actually make an extremely attractive propellant. Apollo Fusion wanted to use a type of ion thruster called a Hall-effect thruster. Ion thrusters strip electrons from the atoms that make up a liquid or gaseous propellant, and then an electric field pushes the resultant ions away from the spacecraft, generating a modest thrust in the opposite direction. The physics of rocket engines means that the performance of these engines increases with the mass of the ion that you can accelerate.
Mercury is heavier than either xenon or krypton, the most commonly used propellants, meaning more thrust per expelled ion. It’s also liquid at room temperature, making it efficient to store and use. And it’s cheap—there’s not a lot of competition with anyone looking to buy mercury.
Bender says that ZMWG, alongside PEER, caught wind of Apollo Fusion marketing its mercury-based thrusters to at least three companies deploying LEO constellations—One Web, Planet Labs, and SpaceX. Planet Labs, an Earth-imaging company, has at least 200 CubeSats in low Earth orbit. One Web and SpaceX, both wireless-communication providers, have many more. One Web plans to have nearly 650 satellites in orbit by the end of 2022. SpaceX already has nearly 1,500 active satellites aloft in its Starlink constellation, with an eye toward deploying as many as 30,000 satellites before its constellation is complete. Other constellations, like Amazon’s Kuiper constellation, are also planning to deploy thousands of satellites.
In 2019, a group of researchers in Italy and the United States estimated how much of the mercury used in spacecraft propellant might find its way back into Earth’s atmosphere. They figured that a hypothetical LEO constellation of 2,000 satellites, each carrying 100 kilograms of propellant, would emit 20 tonnes of mercury every year over the course of a 10-year life span. Three quarters of that mercury, the researchers suggested, would eventually wind up in the oceans.
That amounts to 1 percent of global mercury emissions from a constellation only a fraction of the size of the one planned by SpaceX alone. And if multiple constellations adopted the technology, they would represent a significant percentage of global mercury emissions—especially, the researchers warned, as other uses of mercury are phased out as planned in the years ahead.
Fortunately, it’s unlikely that any mercury propellant thrusters will even get off the ground. Prior to the fourth meeting of the Minamata Convention, Canada, the European Union, and Norway highlighted the dangers of mercury propellant, alongside ZMWG. The provision to ban mercury usage in satellites was passed on 26 March 2022.
The question now is enforcement. “Obviously, there aren’t any U.N. peacekeepers going into space to shoot down” mercury-based satellites, says Bell. But the 137 countries, including the United States, who are party to the convention have pledged to adhere to its provisions—including the propellant ban.
The United States is notable in that list because as Bender explains, it did not ratify the Minamata Convention via the U.S. Senate but instead deposited with the U.N. an instrument of acceptance. In a 7 November 2013 statement (about one month after the original Minamata Convention was adopted), the U.S. State Department said the country would be able to fulfill its obligations “under existing legislative and regulatory authority.”
Bender says the difference is “weedy” but that this appears to mean that the U.S. government has agreed to adhere to the Minamata Convention’s provisions because it already has similar laws on the books. Except there is still no existing U.S. law or regulation banning mercury propellant. For Bender, that creates some uncertainty around compliance when the provision goes into force in 2025.
Still, with a U.S. company being the first startup to toy with mercury propellant, it might be ideal to have a stronger U.S. ratification of the Minamata Convention before another company hits on the same idea. “There will always be market incentives to cut corners and do something more dangerously,” Bell says.
Update 19 April 2022: In an email, a spokesperson for Astra stated that the company's propulsion system, the Astra Spacecraft Engine, does not use mercury. The spokesperson also stated that Astra has no plans to use mercury propellant and that the company does not have anything in orbit that uses mercury.
Updated 20 April 2022 to clarify that Apollo Fusion was building thrusters that used mercury, not that they had actually used them.
SEMrush and Ahrefs are among the most popular tools in the SEO industry. Both companies have been in business for years and have thousands of customers per month.
If you're a professional SEO or trying to do digital marketing on your own, at some point you'll likely consider using a tool to help with your efforts. Ahrefs and SEMrush are two names that will likely appear on your shortlist.
In this guide, I'm going to help you learn more about these SEO tools and how to choose the one that's best for your purposes.
What is SEMrush?
SEMrush is a popular SEO tool with a wide range of features—it's the leading competitor research service for online marketers. SEMrush's SEO Keyword Magic tool offers over 20 billion Google-approved keywords, which are constantly updated and it's the largest keyword database.
The program was developed in 2007 as SeoQuake is a small Firefox extension
Features
Ahrefs is a leading SEO platform that offers a set of tools to grow your search traffic, research your competitors, and monitor your niche. The company was founded in 2010, and it has become a popular choice among SEO tools. Ahrefs has a keyword index of over 10.3 billion keywords and offers accurate and extensive backlink data updated every 15-30 minutes and it is the world's most extensive backlink index database.
Features
Direct Comparisons: Ahrefs vs SEMrush
Now that you know a little more about each tool, let's take a look at how they compare. I'll analyze each tool to see how they differ in interfaces, keyword research resources, rank tracking, and competitor analysis.
User Interface
Ahrefs and SEMrush both offer comprehensive information and quick metrics regarding your website's SEO performance. However, Ahrefs takes a bit more of a hands-on approach to getting your account fully set up, whereas SEMrush's simpler dashboard can give you access to the data you need quickly.
In this section, we provide a brief overview of the elements found on each dashboard and highlight the ease with which you can complete tasks.
AHREFS
The Ahrefs dashboard is less cluttered than that of SEMrush, and its primary menu is at the very top of the page, with a search bar designed only for entering URLs.
Additional features of the Ahrefs platform include:
SEMRUSH
When you log into the SEMrush Tool, you will find four main modules. These include information about your domains, organic keyword analysis, ad keyword, and site traffic.
You'll also find some other options like
Both Ahrefs and SEMrush have user-friendly dashboards, but Ahrefs is less cluttered and easier to navigate. On the other hand, SEMrush offers dozens of extra tools, including access to customer support resources.
When deciding on which dashboard to use, consider what you value in the user interface, and test out both.
If you're looking to track your website's search engine ranking, rank tracking features can help. You can also use them to monitor your competitors.
Let's take a look at Ahrefs vs. SEMrush to see which tool does a better job.
The Ahrefs Rank Tracker is simpler to use. Just type in the domain name and keywords you want to analyze, and it spits out a report showing you the search engine results page (SERP) ranking for each keyword you enter.
Rank Tracker looks at the ranking performance of keywords and compares them with the top rankings for those keywords. Ahrefs also offers:
You'll see metrics that help you understand your visibility, traffic, average position, and keyword difficulty.
It gives you an idea of whether a keyword would be profitable to target or not.
SEMRush offers a tool called Position Tracking. This tool is a project tool—you must set it up as a new project. Below are a few of the most popular features of the SEMrush Position Tracking tool:
All subscribers are given regular data updates and mobile search rankings upon subscribing
The platform provides opportunities to track several SERP features, including Local tracking.
Intuitive reports allow you to track statistics for the pages on your website, as well as the keywords used in those pages.
Identify pages that may be competing with each other using the Cannibalization report.
Ahrefs is a more user-friendly option. It takes seconds to enter a domain name and keywords. From there, you can quickly decide whether to proceed with that keyword or figure out how to rank better for other keywords.
SEMrush allows you to check your mobile rankings and ranking updates daily, which is something Ahrefs does not offer. SEMrush also offers social media rankings, a tool you won't find within the Ahrefs platform. Both are good which one do you like let me know in the comment.
Keyword research is closely related to rank tracking, but it's used for deciding which keywords you plan on using for future content rather than those you use now.
When it comes to SEO, keyword research is the most important thing to consider when comparing the two platforms.
The Ahrefs Keyword Explorer provides you with thousands of keyword ideas and filters search results based on the chosen search engine.
Ahrefs supports several features, including:
SEMrush's Keyword Magic Tool has over 20 billion keywords for Google. You can type in any keyword you want, and a list of suggested keywords will appear.
The Keyword Magic Tool also lets you to:
Both of these tools offer keyword research features and allow users to break down complicated tasks into something that can be understood by beginners and advanced users alike.
If you're interested in keyword suggestions, SEMrush appears to have more keyword suggestions than Ahrefs does. It also continues to add new features, like the Keyword Gap tool and SERP Questions recommendations.
Both platforms offer competitor analysis tools, eliminating the need to come up with keywords off the top of your head. Each tool is useful for finding keywords that will be useful for your competition so you know they will be valuable to you.
Ahrefs' domain comparison tool lets you compare up to five websites (your website and four competitors) side-by-side.it also shows you how your site is ranked against others with metrics such as backlinks, domain ratings, and more.
Use the Competing Domains section to see a list of your most direct competitors, and explore how many keywords matches your competitors have.
To find more information about your competitor, you can look at the Site Explorer and Content Explorer tools and type in their URL instead of yours.
SEMrush provides a variety of insights into your competitors' marketing tactics. The platform enables you to research your competitors effectively. It also offers several resources for competitor analysis including:
Traffic Analytics helps you identify where your audience comes from, how they engage with your site, what devices visitors use to view your site, and how your audiences overlap with other websites.
SEMrush's Organic Research examines your website's major competitors and shows their organic search rankings, keywords they are ranking for, and even if they are ranking for any (SERP) features and more.
The Market Explorer search field allows you to type in a domain and lists websites or articles similar to what you entered. Market Explorer also allows users to perform in-depth data analytics on These companies and markets.
SEMrush wins here because it has more tools dedicated to competitor analysis than Ahrefs. However, Ahrefs offers a lot of functionality in this area, too. It takes a combination of both tools to gain an advantage over your competition.
When it comes to keyword data research, you will become confused about which one to choose.
Consider choosing Ahrefs if you
Consider SEMrush if you:
Both tools are great. Choose the one which meets your requirements and if you have any experience using either Ahrefs or SEMrush let me know in the comment section which works well for you.
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