Garbage truck fires are never ideal, but they are usually not catastrophic. When a fire broke out on December 6 in the back of a garbage truck making its Friday rounds through the Chicago suburb of Arlington Heights, the fire department responded within five minutes. Firefighters saw flames shooting five feet into the air out the back of the truck, and they prepared to put the fire out using hoses and water. Four minutes after their arrival on scene, however, the garbage truck exploded in rather spectacular fashion, injuring several firefighters and police officers, damaging several homes in the vicinity, and scattering debris through the neighborhood.

The truck, it turned out, was powered by compressed natural gas (CNG), stored in five carbon-fiber-wrapped cylinders on the roof. The cylinders had pressure relief valves installed that should have opened when they reached a temperature between 212° and 220° Fahrenheit (100°–140° Celsius). This would vent (flammable) methane gas into the atmosphere, often creating a powerful flamethrower but keeping the tanks from exploding under the rising pressure caused by the heat. In this case, however, all the pressure relief devices failed—and the CNG tanks exploded.

Fire officials now believe that the whole incident began when a resident improperly disposed of a lithium-ion battery by placing it in a recycling bin.

The CNG cylinders were stored atop the truck. Credit: Arlington Heights FD

Explosion on a sunny day

December 6, 2024, was a sunny day with temps in the mid-30s when local dispatch received a call from the driver of a garbage truck operated by a local company called Groot. The driver said that his load was on fire. Arlington Heights firefighters had dealt with six garbage truck fires in the last several years and had no reason to believe that this call would be exceptional.

Typically, a garbage truck driver will compress the truck's load if fire is seen, starving the flames of oxygen and often putting the fire out. The driver of the burning truck had tried this, but the maneuver failed. Apparently, some of the flammable material got under the slide bar of the compactor, spreading the fire further into the truck.

When firefighters arrived on scene, they asked the driver to dump his load in the street, which would reduce the risk of anything on the truck itself—gasoline, CNG, etc.—catching fire. Then the firefighters could put out the blaze easily, treating it like a normal trash fire, and have Groot haul away the debris afterward. But this didn't work either. The flames had spread far enough by this point to put the truck's dumping mechanism out of commission.

So, firefighters unrolled hoses and hooked up to a nearby fire hydrant. They recognized that the truck was CNG-powered, as were many Groot vehicles. CNG offers a lower maintenance cost, uses less fuel, and creates less pollution than diesel, but best practices currently suggest not spraying CNG cylinders directly with water. Firefighters instead tried to aim water right into the back of the garbage truck without wetting the CNG cylinders nearby on the roof.

They were waiting for the telltale hiss of the pressure relief system to trigger. These valves typically open within two to five minutes, depending on fire conditions, and they should be capable of venting all their natural gas some minutes before the CNG canisters would otherwise be in danger of exploding. But the hiss never came, and as Fire Chief Lance Harris and his crew worked to secure the scene and put water onto the burning load, the CNG canisters exploded catastrophically instead.

The explosion, as captured by a bodycam.

In a board of trustees meeting this week in Arlington Heights, Harris recounted the incident, noting that he felt lucky to be alive—and thankful that no township personnel or residents sustained serious injuries.

"We can't prove it," he said, but after two months of investigating the situation, his department had concluded with high probability that the fire had been caused by a lithium-ion battery discarded into a recycling container. This suspicion was based on the amount of fire and the heat and speed with which it burned; lithium-ion batteries that enter "thermal runaway" can burn hot, at around 750° Fahrenheit (399° C).

Harris' takeaway was clear: recycle even small lithium-ion batteries responsibly, as they can cause real hazards if placed into the waste system, where they are often impacted or compressed.

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In a remarkable statement Thursday, SpaceX founder Elon Musk said the International Space Station should be deorbited "as soon as possible."

This comment from Musk will surely set off a landmine in the global space community, with broad implications. And it appears to be no idle comment from Musk who, at times, indulges in deliberately provocative posts on the social media network X that he owns.

However, that does not seem to be the case here.

"It is time to begin preparations for deorbiting the @Space_Station. It has served its purpose. There is very little incremental utility. Let’s go to Mars," Musk wrote at midday on Thursday.

This original statement was somewhat ambiguous. Last July, NASA awarded Space X an $843 million contract to modify a Dragon spacecraft to serve as a propulsive vehicle to safely guide the aging space station into the Pacific Ocean in 2030. So in some sense, preparations are already underway to shut down the laboratory.

I asked Musk if he meant that NASA and the US government should commit to the 2030 end-of-life date, or if he wanted to accelerate the timeline for the station's demise.

"The decision is up to the President, but my recommendation is as soon as possible. I recommend 2 years from now," Musk replied.

In other words, the owner of SpaceX, the most powerful actor in spaceflight globally, and one of the most powerful people in the world who is presently working alongside the US president to transform the government, wants to bring the space station down in early 2027.

Myriad ramifications

The politics of this are complicated. President Trump could propose shutting down the space station, but the budget for the deorbit vehicle (which is necessary, otherwise the station might make an uncontrolled reentry over land) must be funded by Congress.

The space station has key supporters in Congress, including Sen. Ted Cruz (R-Texas), in whose state the orbiting laboratory is managed. Cruz has long been an advocate of the space station. Ars reached out to Cruz for a comment on Thursday, but the senator did not immediately respond.

However, a key source said Cruz was "furious" with the sentiment from Musk. The timing of Musk's tweet could make the confirmation of private astronaut Jared Isaacman to become NASA administrator more difficult. As part of the confirmation process, Isaacman is due to begin meetings with US senators in the coming week.

Having to answer questions about the end-of-life for the space station will make some of these meetings uncomfortable.

As chairman of the US Senate Committee on Commerce, Science, & Transportation, Cruz effectively has control over Isaacman's confirmation process. He was also just re-elected to a six-year term, so theoretically Cruz is less susceptible to political pressure from the Trump White House.

NASA in a tight spot

Musk's statement would also put NASA in a difficult position. The US space agency, along with most of the international partners, wants to keep the space station operating until at least 2030. Roscosmos, Russia's space agency, has formally committed to operating the space station through at least 2028. The United States and Russia each operate a large segment of the space station, and cooperation from both major partners is necessary to keep the lab flying.

In reality, NASA has only been fully utilizing the space station since late 2020, when it began to fly a full complement of astronauts thanks to SpaceX's Crew Dragon coming online. The agency says it has a lot of worthwhile scientific and human performance research to conduct over the next five years.

NASA's selection of a deorbit vehicle last summer was a concrete signal that it intends to end the life of the venerable space station in 2030.

Some stakeholders, including Boeing, which has a large contract to operate the station for NASA, have suggested the facility could fly beyond 2030. However, structural elements of the station have been in space for more than a quarter of a century, and NASA is growing increasingly concerned about leaks in Russian modules aboard the facility.

As the ISS goes away, NASA's plan is to transition operations to private space stations in low-Earth orbit, a plan it calls "Commercial LEO Destinations." The space agency has provided some funding to four different companies to begin work on these stations.

Nevertheless, this program is generally underfunded, and there are questions about the viability of private companies operating facilities in space by or before 2030. The general consensus in the space community is that if NASA wants to have even a single private space station operating in low-Earth orbit by 2030, it will need to increase funding for this.

What is Elon doing?

There are some plausible explanations for why Musk would seek to end the life of the space station early. His statement about "Let's go to Mars" implies that the money presently being spent on the space station should be repurposed toward human exploration of Mars.

NASA's annual budget for the International Space Station is a little more than $3 billion. Of this more than half is spent on "transportation," which is cargo and crew supply missions. In 2023, for example, NASA spent $1.76 billion on transportation to the station, the majority of which went to SpaceX for its Dragon cargo and crew flights.

Canceling NASA's operations in low-Earth orbit could free up some funding for Mars if Cruz and the other ISS supporters in Congress agree, which seems questionable.

Musk has likely told Trump that NASA does not need to fund private space stations in low-Earth orbit. Rather, Musk could offer an alternative solution if NASA wants to maintain a presence there. SpaceX already plans to launch multiple Starship vehicles into space, and NASA is working on Starship life support systems for its Artemis missions. A version of Starship could be developed to provide a semi-permanent presence in low-Earth orbit.

This is, of course, easier said than done.

It would also wreck the business plans of multiple US companies working to provide this capability for NASA. Moreover, it would shoulder even more responsibility for the US space enterprise onto a single company, SpaceX. This goes against NASA's long-standing policy to have multiple providers and its desire to foster a healthy ecosystem of commercial space companies.

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An asteroid discovered late last year is continuing to stir public interest as its odds of striking planet Earth less than eight years from now continue to increase.

Two weeks ago, when Ars first wrote about the asteroid, designated 2024 YR4, NASA's Center for Near Earth Object Studies estimated a 1.9 percent chance of an impact with Earth in 2032. NASA's most recent estimate has the likelihood of a strike increasing to 3.2 percent. Now that's not particularly high, but it's also not zero.

Naturally the prospect of a large ball of rock tens of meters across striking the planet is a little worrisome. This is large enough to cause localized devastation near its impact site, likely on the order of the Tunguska event of 1908, which leveled some 500 square miles (1,287 square kilometers) of forest in remote Siberia.

To understand why the odds from NASA are changing, and whether we should be concerned about 2024 YR4, Ars connected with Robin George Andrews, author of the recently published book How to Kill an Asteroid. Good timing with the publication date, eh?

Ars: Why are the impact odds increasing?

Robin George Andrews: The asteroid’s orbit is not known to a great deal of precision right now, as we only have a limited number of telescopic observations of it. However, even as the rock zips farther away from Earth, certain telescopes are still managing to spy it and extend our knowledge of the asteroid’s orbital arc around the Sun. The odds have fluctuated in both directions over the last few weeks, but overall, they have risen; that’s because the amount of uncertainty astronomers have as to its true orbit has shrunk, but Earth has yet to completely fall out of that zone of uncertainty. As a proportion of the remaining uncertainty, Earth is taking up more space, so for now, its odds are rising.

Think of it like a beam of light coming out of the front of that asteroid. That beam of light shrinks as we get to know its orbit better, but if Earth is yet to fall out of that beam, it takes up proportionally more space. So, for a while, the asteroid’s impact odds rise. It’s very likely that, with sufficient observations, Earth will fall out of that shrinking beam of light eventually, and the impact odds will suddenly fall to zero. The alternative, of course, is that they'll rise close to 100 percent.

Ars: What are we learning about the asteroid's destructive potential?

Andrews: The damage it could cause would be localized to a roughly city-sized area, so if it hits the middle of the ocean or a vast desert, nothing would happen. But it could trash a city, or completely destroy much of one, with a direct hit.

The key factor here (if you had to pick one) is the asteroid’s mass. Each time the asteroid gets twice as long (presuming it’s roughly spherical), it brings with it 8 times more kinetic energy. So if the asteroid is on the smaller end of the estimated size range—40 meters—then it will be as if a small nuclear bomb exploded in the sky. At that size, unless it’s very iron-rich, it wouldn’t survive its atmospheric plunge, so it would explode in mid-air. There would be modest-to-severe structural damage right below the blast, and minor to moderate structural damage over tens of miles. A 90-meter asteroid would, whether it makes it to the ground or not, be more than 10x more energetic; a large nuclear weapon blast, then. A large city would be severely damaged, and the area below the blast would be annihilated.

Ars: Do we have any idea where the asteroid might strike on Earth?

Andrews: The "risk corridor" is currently spread over parts of the eastern Pacific Ocean, northern South America, the Atlantic Ocean, parts of Africa, the Arabian Sea and South Asia. Additional observations will ultimately narrow this down, if an impact remains possible.

Ars: What key observations are we still waiting for that might clarify the threat?

Andrews: Most telescopes will lose sight of this "small" asteroid in the coming weeks. But the James Webb Space Telescope will be able to track it until May. For the first time, it’s been authorized for planetary defense purposes, largely because its infrared eye allows it to track the asteroid further out than optical light telescopes. JWST will not only improve our understanding of its orbit, but also constrain its size. First observations should appear by the end of March.

JWST may rule out an impact in 2032. But there's a chance we may be stuck with a few-percentage impact probability until 2028, when the asteroid makes its next Earth flyby. Bit awkward, if so.

Ars: NASA's DART mission successfully shifted an asteroid's orbit in 2022. Could this technology be used?

Andrews: Not necessarily. DART—a type of spacecraft called a kinetic impactor—was a great success. But it still only changed Dimorphos' orbit by a small amount. Ideally, you want many years of advance notice to deflect an asteroid with something like DART to ensure the asteroid has moved out of Earth’s way. I've often been told that at least 10 years prior to impact is best if you want to be sure to deflect a city killing-size asteroid. That’s not to say deflection is impossible; it just becomes trickier to pull off. You can’t just hit it with a colossal spacecraft, because you may fragment it into several still-dangerously sized pieces. Hit it too softly, and it will still hit Earth, but somewhere that wasn’t originally going to be hit. You have to be super careful here.

Some rather clever scientists at the Lawrence Livermore National Laboratory (which has a superb planetary defense contingent) worked out that, for a 90-meter asteroid, you need 10 years to confidently deflect it with a kinetic impactor to prevent an Earth impact. So, to deflect 2024 YR4, if it’s 90 meters long and we have just a few years of time, we’d probably need a bigger impactor spacecraft (but don’t break it!)—or we’d need several kinetic impactors to deflect it (but each has to work perfectly).

Eight years until impact is a little tight. It’s not impossible that the choice would be made to use a nuclear weapon to deflect it; this could be very awkward geopolitically, but a nuke would impart a bigger deflection than an equivalent DART-like spacecraft. Or, maybe, they’d opt to try and vaporize the asteroid with something like a 1 megaton nuke, which LLNL says would work with an asteroid this size.

Ars: So it's kind of late in the game to be planning an impact mission?

Andrews: This isn’t an ideal situation. And humanity has never tried to stop an asteroid impact for real. I imagine that if 2024 YR4 does become an agreed-upon emergency, the DART team (JHUAPL + NASA, mostly) would join forces with SpaceX (and other space agencies, particularly ESA but probably others) to quickly build the right mass kinetic impactor (or impactors) and get ready for a deflection attempt close to 2028, when the asteroid makes its next Earth flyby. But yeah, eight years is not too much time.

A deflection could work! But it won’t be as simple as just hitting the asteroid really hard in 2028.

Ars: How important is NASA to planetary defense?

Andrews: Planetary defense is an international security concern. But right now, NASA (and America, by extension) is the vanguard. Its planetary defenders are the watchers on the wall, the people most responsible for not just finding these potentially hazardous asteroids before they find us, but also those most capable of developing and deploying tech to prevent any impacts. America is the only nation with (for now!) a well-funded near-Earth object hunting program, and is the only nation to have tested out a planetary defense technique. It’s a movie cliché that America is the only nation capable of saving the world from cosmic threats. But, for the time being—even with amazing planetary defense mission contributions from ESA and JAXA—that cliché remains absolutely true.

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Spread across NASA's headquarters and 10 field centers, which dot the United States from sea to sea, the space agency has had a workforce of nearly 18,000 civil servants.

However, by the end of today, that number will have shrunk by about 10 percent since the beginning of the second Trump administration four weeks ago. And the world's preeminent space agency may still face significant additional cuts.

According to sources, about 750 employees at NASA accepted the "fork in the road" offer to take deferred resignation from the space agency later this year. This sounds like a lot of people, but generally about 1,000 people leave the agency every year, so effectively, many of these people might just be getting paid to leave jobs they were already planning to exit from.

The culling of "probationary" employees will be more impactful. As it has done at other federal agencies, the Trump administration is generally firing federal employees who are in the "probationary" period of their employment, which includes new hires within the last one or two years or long-time employees who have moved into or been promoted into a new position. About 1,000 or slightly more employees at NASA were impacted by these cuts.

Adding up the deferred resignations and probationary cuts, the Trump White House has now trimmed about 10 percent of the agency's workforce.

However, the cuts may not stop there. Two sources told Ars that directors at the agency's field centers have been told to prepare options for a "significant" reduction in force in the coming months. The scope of these cuts has not been defined, and it's possible they may not even happen, given that the White House must negotiate budgets for NASA and other agencies with the US Congress. But this directive for further reductions in force casts more uncertainty on an already demoralized workforce and signals that the Trump administration would like to make further cuts.

An awful week

Job losses are always terrible. This will be a dark and painful day at a space agency that brings so much light and joy to the world. Many of the probationary employees are just starting out their careers and were likely thrilled to land a job at NASA to explore the universe. And then all of that youthful energy and hope was extinguished this week.

It's possible to view these losses through a couple of lenses.

Yes, NASA is clearly losing some capability with these latest cuts. Many of these hires were likely being counted on to bring new energy into the space agency and become its future discoverers and leaders. And their jobs are being sacrificed for no clear purpose. Is it to increase funding for the military? Is it to pay for tax cuts for the rich? There is a lot of anger that the relatively thin budget line of NASA—less than one-half of 1 percent of the federal budget—is being sliced for such purposes.

There is also frustration at the indiscriminate nature of the cuts. The Trump White House and the Department of Government Efficiency, spearheaded by Elon Musk, have taken a meat-cleaver approach by firing a lot of people at the same time, and probably not the right people, through a messy and painful process. This is not dissimilar to job cuts during corporate mergers or bankruptcies. It's the fastest possible way to make cuts. There is no empathy, and it is a brutal process.

Are cuts needed?

It is also clear that, as within other federal agencies, there is significant "bloat" in NASA's budget. In some areas, this is plain to see, with the space agency having spent in excess of $3 billion a year over the last decade "developing" a heavy lift rocket, the Space Launch System, which used components from the Space Shuttle and costs an extraordinary amount of money to fly. In the meantime, the private launch industry has been running circles around NASA. Similarly, consider the Orion spacecraft. This program is now two decades old, at a cost of $1 billion a year, and the vehicle has never flown humans into space.

One could go on. Much of the space community has been puzzled as to why NASA has been spending on the order of half a billion dollars to develop a Lunar Gateway in an odd orbit around the Moon. It remains years away from launching, and if it ever does fly, it would increase the energy needed to reach the surface of the Moon. The reason, according to multiple sources at the agency when the Gateway was conceived, is that the lunar space station would offer jobs to the current flight controllers operating the International Space Station, which is due to retire in 2030.

In recent years, NASA has been in the midst of a difficult transition. The agency deserves a lot of credit for nurturing a commercial space industry that now is the envy of the world. But as part of this, NASA has been moving away from owning and operating its rockets, spacecraft, and other hardware and buying services from this commercial space industry. This transition from traditional space to commercial space marks an important step for NASA to remain on the cutting edge of exploration and science rather than trying to compete with US industry.

But it is also a painful step.

The key is ensuring that any future cuts at NASA are not indiscriminate. If and when Jared Isaacman is confirmed by the US Senate as the next NASA administrator, it will be up to him and his team to make the programmatic decisions about which parts of the agency are carrying their weight and which are being carried, which investments carry NASA into the future, and which ones drag it into the past. If these future cuts are smart and position NASA for the future, this could all be worth it. If not, then the beloved agency that dares to explore may never recover.

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Most PC games that you can play on a modern PC would run faster on an Nvidia RTX 5080 or 5090 than, say, a GTX 1070. But some games, from a particular phase of enthusiasm for particles, destructible environments, and smooth-moving hair, will take a notable hit if their owners upgrade to the latest Nvidia cards.

That's because PhysX, once a dedicated physics simulation tool and card that became a selling point for Nvidia's gear, has been largely deprecated on Nvidia 50-series cards. The transition was announced in January, but it seems to have taken some time for someone to notice the impact on 32-bit, PhysX-enabled games (as seen by PCGamesN). The most recent of these affected games, Assassin's Creek IV: Black Flag, came out in 2013.

What follows is a brief primer on PhysX: what it was, what it did, and why it's left out of Nvidia's road map.

Ten thousand to 40,000 strands of tessellated, HairWorks-enhanced hair on this Polish legend. Credit: CD Projekt Red

From Citadel Station to Geralt’s Hair

Many years ago, if you wanted impressive physics in your game, someone had to build it in code. Seamus Blackley, who would one day create and design the Xbox, took his graduate-level physics knowledge and applied it to System Shock, making it the rare game where the player's body had real mass to it and grenades bounced off walls like you might think they would.

These days, game engines like Unity can handle a lot of the physics thinking for developers. But in the years between, there was PhysX. PhysX started as a simulation engine from a Swedish firm, NovodeX, then was acquired by Ageia in 2004 and expanded to include hardware cards.

PhysX cards held such promise that, at one point, Tim Sweeney—back then, known primarily for Unreal Tournament—considered adding support for a PhysX card for the 2007 version of his game.

But Nvidia bought Ageia in 2008 and got to work incorporating PhysX into its own GPUs. The newly green-hued PhysX showed up as an SDK available to all PlayStation 3 developers and made outreach efforts to get developers thinking about PhysX support from the beginning. It worked, to some extent, with games like Mafia II and Batman: Arkham City showing off advanced particles, collision, and other physics effects. You could shoot a wall and leave holes in it, and smoke didn't look so much like a flat sprite trick, but a real thing that took up space.

Nvidia's PhysX offerings to developers didn't always generate warm feelings. As part of its broader GamesWorks package, PhysX was cited as one of the reasons The Witcher 3 ran at notably sub-optimal levels at launch. Protagonist Geralt's hair, rendered in PhysX-powered HairWorks, was a burden on some chipsets.

PhysX started appearing in general game engines, like Unity 5, and was eventually open-sourced, first in limited computer and mobile form, then more broadly. As an application wrapped up in Nvidia's 32-bit CUDA API and platform, the PhysX engine had a built-in shelf life. Now the expiration date is known, and it is conditional on buying into Nvidia's 50-series video cards—whenever they approach reasonable human prices.

See that smoke? It's from Sweden, originally. Credit: Gearbox/Take 2

The real dynamic particles were the friends we made…

Nvidia noted in mid-January that 32-bit applications cannot be developed or debugged on the latest versions of its CUDA toolkit. They will still run on cards before the 50 series. Technically, you could also keep an older card installed on your system for compatibility, which is real dedication to early-2010's-era particle physics.

Technically, a 64-bit game could still support PhysX on Nvidia's newest GPUs, but the heyday of PhysX, as a stand-alone technology switched on in game settings, tended to coincide with the 32-bit computing era.

If you load up a 32-bit game now with PhysX enabled (or forced in a config file) and a 50-series Nvidia GPU installed, there's a good chance the physics work will be passed to the CPU instead of the GPU, likely bottlenecking the game and steeply lowering frame rates. Of course, turning off PhysX entirely raised frame rates above even native GPU support levels.

Demanding Borderlands 2 keep using PhysX made it so it "runs terrible," noted one Redditor, even if the dust clouds and flapping cloth strips looked interesting. Other games with PhysX baked in, as listed by ResetEra completists, include Metro 2033, Assassin's Creed IV: Black Flag, and the 2013 Star Trek game.

Commenters on Reddit and ResetEra note that many of the games listed had performance issues with PhysX long before Nvidia forced them to either turn off or be loaded onto a CPU. For some games, however, PhysX enabled destructible environments, "dynamic bank notes" and "posters" (in the Arkham games), fluid simulations, and base gameplay physics.

Anyone who works in, or cares about, game preservation has always had their work cut out for them. But it's a particularly tough challenge to see certain aspects of a game's operation lost to the forward march of the CUDA platform, something that's harder to explain than a scratched CD or Windows compatibility.

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