Day: September 15, 2023

As it rolls from one political crisis to another, it’s hard not to think of Britain as metaphorically crumbling. Now, it seems, significant pieces of the country are literally structurally unsound. More than 150 schools, colleges, and nurseries in England have been ordered to close parts of their buildings due to the looming threat of collapse—just days before the start of the new school year. Twenty-seven health care facilities are being urgently reviewed; seven hospitals need to be rebuilt. The cause of the panic is Reinforced Autoclaved Aerated Concrete, whose acronym “RAAC” has suddenly entered the British political vernacular.

RAAC differs from conventional concrete mainly in that it is filled with air bubbles instead of aggregates such as gravel. It’s lighter, easier to build with quickly, and cheaper than other forms of concrete. The air bubbles also provide good thermal insulation, meaning that buildings containing RAAC are easier to heat and cool. It was widely used in postwar Britain all the way up to the 1990s to cast panels for roofs, floors, and walls, and was particularly popular in the public sector, where it was used to rebuild schools, hospitals, and other infrastructure.

But anything cheap and fast comes at a price. RAAC, being less durable than standard concrete, gradually weakens, and the bubbles allow water to seep in. While the steel bars that support the RAAC panels are usually coated with waterproof layers, a lack of maintenance can cause these to corrode, further weakening the panels and causing them to break apart. The lifespan of a RAAC structure is only between 30 and 50 years. That vulnerability has been known about for years. But over the past month, it has taken on the momentum of a present crisis, as it becomes clear just how many important buildings and pieces of infrastructure are well past the end of their shelf life. In addition to schools and hospitals, RAAC issues have been found in theaters, housing blocks, council buildings, and even in London’s two biggest airports, Heathrow and Gatwick. It has created a multimillion-dollar headache for the British government, and further illustrates the cost of underinvestment in public goods and of relying on quick fixes for long-term needs.

“The problem with these panels is not so much the material itself. It’s the fact that they’ve been used well beyond their expiry date,” says Juan Sagaseta, a reader in structural robustness at the University of Surrey. “Unfortunately, spending on new buildings and opening new schools or hospitals is often viewed in our society as more glamorous than spending on maintaining the old ones.”

The issues around RAAC were first investigated in the 1990s by the Building Research Establishment (BRE), an organization initially established as a government agency that now operates as a social enterprise. At the time, the removal of roof panels from some buildings had raised concerns, although there had been no conclusive evidence of immediate safety risks. It wasn’t until 2018 that the Department of Education finally took action, after the ceiling of a primary school in Kent, in Southern England, suddenly collapsed. Fortunately, the incident happened on a Saturday and no one was injured. The school had been rebuilt in 1979 using RAAC after a fire. School authorities were sent questionnaires to try to establish whether or not they had RAAC in their buildings, but, Sagaseta says, they (understandably) often didn’t have the expertise or resources to identify the material. Finally, in the fall of 2022, the Department of Education sent out professional surveyors to classify RAAC constructions as “critical” or “noncritical.”

The sudden decision to close schools this summer was triggered by three cases of RAAC panels that were considered noncritical but later failed. The first incident involved a commercial building, the second a school in a different country, and the third an English school in late August. The 150 or so institutions now known to be at greatest risk represent a tiny fraction of the 22,000 state-owned schools, colleges, and nurseries in England.

Edward Tian didn’t think of himself as a writer. As a computer science major at Princeton, he’d taken a couple of journalism classes, where he learned the basics of reporting, and his sunny affect and tinkerer’s curiosity endeared him to his teachers and classmates. But he describes his writing style at the time as “pretty bad”—formulaic and clunky. One of his journalism professors said that Tian was good at “pattern recognition,” which was helpful when producing news copy. So Tian was surprised when, sophomore year, he managed to secure a spot in John McPhee’s exclusive non-fiction writing seminar.

Every week, 16 students gathered to hear the legendary New Yorker writer dissect his craft. McPhee assigned exercises that forced them to think rigorously about words: Describe a piece of modern art on campus, or prune the Gettysburg Address for length. Using a projector and slides, McPhee shared hand-drawn diagrams that illustrated different ways he structured his own essays: a straight line, a triangle, a spiral. Tian remembers McPhee saying he couldn’t tell his students how to write, but he could at least help them find their own unique voice.

If McPhee stoked a romantic view of language in Tian, computer science offered a different perspective: language as statistics. During the pandemic, he’d taken a year off to work at the BBC and intern at Bellingcat, an open source journalism project, where he’d written code to detect Twitter bots. As a junior, he’d taken classes on machine learning and natural language processing. And in the fall of 2022, he began to work on his senior thesis about detecting the differences between AI-generated and human-written text.

When ChatGPT debuted in November, Tian found himself in an unusual position. As the world lost its mind over this new, radically improved chatbot, Tian was already familiar with the underlying GPT-3 technology. And as a journalist who’d worked on rooting out disinformation campaigns, he understood the implications of AI-generated content for the industry.

While home in Toronto for winter break, Tian started playing around with a new program: a ChatGPT detector. He posted up at his favorite café, slamming jasmine tea, and stayed up late coding in his bedroom. His idea was simple. The software would scan a piece of text for two factors: “perplexity,” the randomness of word choice; and “burstiness,” the complexity or variation of sentences. Human writing tends to rate higher than AI writing on both metrics, which allowed Tian to guess how a piece of text had been created. Tian called the tool GPTZero—the “zero” signaled truth, a return to basics—and he put it online the evening of January 2. He posted a link on Twitter with a brief introduction. The goal was to combat “increasing AI plagiarism,” he wrote. “Are high school teachers going to want students using ChatGPT to write their history essays? Likely not.” Then he went to bed.

Tian woke up the next morning to hundreds of retweets and replies. There was so much traffic to the host server that many users couldn’t access it. “It was totally crazy,” Tian says. “My phone was blowing up.” A friend congratulated him on winning the internet. Teens on TikTok called him a narc. “A lot of the initial hate was like, ‘This kid is a snitch, he doesn’t have a life, he never had a girlfriend,’” says Tian with a grin. “Classic stuff.” (Tian has a girlfriend.) Within days, he was fielding calls from journalists around the world, eventually appearing on everything from NPR to the South China Morning Post to Anderson Cooper 360. Within a week, his original tweet had reached more than 7 million views.

Most people interpret radiation as a bad thing—but it isn’t always. In fact, radiation is a very normal phenomenon. For now, let’s just say that radiation is when an object produces energy. When a material is radioactive, it emits energy either as particles or electromagnetic waves. The particles are usually things like electrons or atoms. The waves could be in any region of the electromagnetic spectrum. Since your Wi-Fi produces electromagnetic waves, technically your home access point is a source of radiation. So is that light bulb in the ceiling. Actually, even you are a source of radiation in the infrared spectrum, due to your temperature.

However, most people don’t think of radiation that way. What’s commonly called “radiation” is actually a special type: ionizing radiation. When an object produces ionizing radiation, it emits enough energy that when it interacts with other materials there’s a chance it could free an electron from its atom. This electron is then free to interact with other atoms, or maybe just wander off into empty space. But no matter what the electron does, once it gets away from its original atom, we call that ionization.

Ionizing radiation was discovered by accident. Before digital smartphones, when people took pictures on film, the basic idea of photography was that when film was exposed to light, it would cause a chemical reaction that would reveal a picture when the film was developed. Then in 1896, French physicist Henri Becquerel discovered radioactivity when he realized that uranium salts produced an effect on otherwise unexposed photographic film that was still in its wrapper. Somehow the uranium produced an effect similar to light, but unlike the light, it could pass through the paper wrapping.

It turns out that uranium is naturally radioactive, and this was a type of ionizing radiation. Uranium produces electromagnetic waves in the gamma spectrum. Gamma radiation is similar to visible light when it interacts with film (thus exposing it), but it’s different from visible light in that it can pass through paper.

You might not directly use uranium in your everyday life, but you will indeed encounter ionizing radiation—at safe levels—in many different applications. For example, smoke detectors use a radioactive source to detect smoke in the air. A radioactive source produces charged particles (alpha particles, in most cases) that ionize the air inside the detector, which in turn creates an electric current in the air. If tiny particles of smoke get inside the detector, it blocks this electrical current. Then the detector sends a signal to make an ear-piercing noise so that you know there’s a fire—or maybe that you burnt your dinner on the stove.

Eighteen percent of the electrical power in the US comes from nuclear power plants, and they obviously produce ionizing radiation. Medical x-ray images can produce ionizing radiation. Some ceramic dishes are coated in a uranium-based paint—yup, that produces radiation. Technically, bananas are radioactive, due to their comparatively large concentration of potassium. Ionizing radiation could even be from outer space—we call these cosmic rays.

Firefly Aerospace just set a new responsive-launch record.

The company’s Alpha rocket lifted off from Vandenberg Space Force Base on Thursday (Sept. 14) at 10:28 p.m. EDT (7:28 p.m. local California time; 0228 GMT on Sept. 15), kicking off a mission for the U.S. Space Force called Victus Nox.

The rocket roared off the pad just 27 hours after the U.S. Space Force gave the order — less time than on any previous national security mission. 

“The success of Victus Nox marks a culture shift in our nation’s ability to deter adversary aggression and, when required, respond with the operational speed necessary to deliver decisive capabilities to our warfighters,” Lt. Gen. Michael Guetlein, commander of the Space Force’s Space Systems Command (SSC), said in an emailed statement. 

“This exercise is part of an end-to-end Tactically Responsive Space demonstration which proves the United States Space Force can rapidly integrate capabilities and will respond to aggression when called to do so on tactically relevant timelines,” Guetlein added.

Thursday’s launch was not livestreamed. Neither Firefly nor the Space Force publicized the timing of the liftoff in advance.

Related: US Space Force establishes new unit to track ‘threats in orbit’

The wheels for Victus Nox (Latin for “conquer the night”) began turning in September 2022, when the Space Force awarded contracts to Texas-based Firefly and Millennium Space Systems, a Boeing subsidiary headquartered in the Los Angeles area that built the mission’s payload.

That payload will perform a “space domain awareness” mission, keeping tabs on the orbital environment for the Space Force.

But the leadup to launch may have been more important than any data that Victus Nox ends up gathering, as it showcased new capabilities that the U.S. military is eager to implement. 

“This end-to-end mission will demonstrate the United States’ ability to rapidly place an asset on orbit when and where we need it, ensuring we can augment our space capabilities with very little notice,” SSC’s Lt. Col. MacKenzie Birchenough said in a statement last year, when the Victus Nox contracts were announced. 

On Aug. 30 of this year, Firefly and Millenium entered the mission’s “hot standby” phase, a six-month period during which they could receive a launch-alert notice at any time. After receipt of that notice, Millenium and Firefly would have 60 hours to get the satellite from Millenium’s Southern California facilities to Vandenberg, fuel it up and mate it to the Alpha rocket’s payload adapter.

The alert came through recently, and the mission teams hit their ambitious timeline.

“Upon activation, the space vehicle was transported 165 miles [266 kilometers] from Millenium’s El Segundo facility to Vandenberg Space Force Base where it was tested, fueled and mated to the launch adapter in just under 58 hours, significantly faster than the typical timeline of weeks or months,” Space Force officials said in the emailed statement. 

The teams then had to wait for the launch order, which would give them Victus Nox’s orbital requirements. They would then have just 24 hours to update Alpha’s trajectory and guidance software, encapsulate the satellite in its payload fairing, get the payload to the pad, mate it to Alpha and get the rocket ready to launch, Firefly wrote in a statement.

The teams managed that task as well. They were ready to launch as soon as the first window opened, which was 27 hours after the Space Force gave the order.

“Challenging missions like this is where Firefly excels, and we are extremely humbled and proud to provide the U.S. Space Force and the nation with the critical capability to launch on-demand in support of national security,” Firefly CEO Bill Weber said in the same company statement.

“Together with our mission partners, we’ll be setting a new standard, proving nominal launch operations can be completed in a matter of hours rather than weeks to months,” he added.

Victus Nox’s speed goals didn’t end with the successful liftoff. The teams now aim to get the satellite up and running within 48 hours of its deployment.

The previous responsive-launch record for a U.S. national security mission was 21 days, Space Force officials said. That mark was set in June 2021 on the Tactically Responsive Launch-2 (TacRL-2) mission, which was carried out by a Northop Grumman Pegasus XL air-launched rocket.

TacRL-2 and Victus Nox are both demonstration missions of SSC’s Space Safari Program Office, “which is responsible for responding to urgent on-orbit needs, to include acquiring, integrating, and executing TacRS capabilities,” according to the Space Force statement.

Victus Nox’s liftoff was just the third for Firefly’s Alpha. The rocket failed during its debut launch in September 2021. It delivered seven satellites to orbit on its second flight, in October 2022, but apparently deployed them at a lower altitude than planned, leading to early reentries for the payloads.