The EmDrive turns out to be the "um..." drive after all, as a new study dubs any previous encouraging EmDrive results "false positives."
- The proposed EmDrive captured the public's imagination with the promise of super-fast space travel that broke the laws of physics.
- Some researchers have detected thrusts from the EmDrive that seemed to prove its validity as a technology.
- A new, authoritative study says, no, those results were just "false positives."
Now it seems that, yep, it was too good to be true. Scientists at Dresden University of Technology (TU Dresden) appear to have conclusively proven that the EmDrive does not, in fact, produce any thrust. They provide some compelling evidence that small indications of thrust in previous research were simply false positives produced by outside forces.
How the EmDrive is supposed to work
Credit: AndSus/Adobe Stock
In the EmDrive, says
the company that owns rights to the invention, "Thrust is produced by the amplification of the radiation pressure of an electromagnetic wave propagated through a resonant waveguide assembly." In simpler words, trapped microwaves bounce around a specially shaped enclosed container, producing thrust that pushes the whole thing forward.
They also assert that while the EmDrive is not exactly on speaking terms with Newton's Third Law, the company says it's perfectly in line with the second one:
"This relies on Newton's Second Law where force is defined as the rate of change of momentum. Thus, an electromagnetic (EM) wave, traveling at the speed of light has a certain momentum which it will transfer to a reflector, resulting in a tiny force."
Interest in the EmDrive has been understandable considering what it was supposed to do. Speaking to Popular Mechanics last year, Mike McCulloch, the leader of DARPA's EmDrive investigation, describes how the engine could "transform space travel and see craft lifting silently off from launchpads and reaching beyond the solar system." He mentioned his excitement at being able to get from here to Proxima Centauri — 4.2465 light years away — in just 90 human years.
It doesn't work. Yes it does. No, it doesn't.
NASA Eagleworks' EmDriveCredit: NASA/Wikimedia Commons
DARPA, part of the U.S. Department of Defense, is only one of the organizations investigating the claims made for the EmDrive. In 2018 the agency invested $1.3 million to study the device in research that will be wrapping up this May barring any significant last-minute breakthroughs.
Teams from all over the world have been testing Shawyer's idea since it was introduced and releasing often contradictory test results. This may have to do with the fact that teams detecting any EmDrive thrust at all have reported vanishingly small amounts of it, measured in milliNewtons (mN). A mN equals about 0.00022 pounds of force.
"Ever since the introduction of the EmDrive concept in 2001, every few years a group claims to have measured a net force coming from its device. But these researchers are measuring an incredibly tiny effect: a force so small it couldn't even budge a piece of paper. This leads to significant statistical uncertainty and measurement error."
For a sense of how minuscule these results are, consider that the possible thrust force reported by NASA in 2014 of 30-50 micro-Newtons is roughly equivalent to the weight of a big ant. Chinese researchers have claimed detection of 720 mN in their tests. That would be 72 grams of thrust. An iPhone 11 with a case weights 219 grams.
Too small to stand out against background noise
These tiny amounts of EmDrive thrust lie at the heart of what the TU Dresden researchers are saying: The effects are simply too small to rule out effects that don't really come from the EmDrives at all. The researchers have just published three papers. The title of one "High-Accuracy Thrust Measurements of the EmDrive and Elimination of False-Positive Effects" tells the story. The other two studies are here and here.
When the UT Dresden team turned on their EmDrive based on NASA's EmDrive, they, too witnessed tiny amounts of apparent thrust.
However, says Martin Tajmar of UT Dresden to German media outlet GreWi, they soon realized what was going on: "When power flows into the EmDrive, the engine warms up. This also causes the fastening elements on the scale to warp, causing the scale to move to a new zero point. We were able to prevent that in an improved structure."
Putting the kibosh on other researchers' results, the authors of the studies write:
"Using a geometry and operating conditions close to the model by White et al. that reported positive results published in the peer-reviewed literature, we found no thrust values within a wide frequency band including several resonance frequencies. Our data limits any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by more than three orders of magnitude."
This would seem to be the definitive end of the EmDrive story.
When we look at the night sky, we may see junk instead of stars.
- New research has found that the entire planet is covered by light pollution from space objects.
- Companies like SpaceX and Amazon plan to launch thousands of satellites into orbit this decade.
- Scientists fear this space traffic will impede their ability to stare into deep space.
In December, we reported on the imminent clean-up of space junk. With an estimated 129 million pieces of debris currently orbiting our atmosphere, one lucrative contract awarded by the European Space Agency will commence in 2025.
Four years is a long time, however, given the amount of junk we've allowed to float into space. It's not the only issue affecting the crowded ether. New research, published in the Monthly Notices of the Royal Astronomical Society: Letters, has found that astronomers can no longer find anywhere on Earth to view the night sky free of space junk and satellite pollution.
Although the first satellite was only launched in 1957, as of the beginning of this year, 3,372 are now in orbit, alongside the aforementioned debris—what the research team from Slovakia, Spain, and the United States term "space objects" for sake of brevity. These objects range in altitude from a few hundred to over 35,000 kilometers.
These objects pose an immediate threat to researchers by compromising astronomical data. Space debris and satellites often appear as streaks of varying lengths and brightness in ground-based telescopes. And the problem is going to get worse, says John Barentine of the International Dark-Sky Association.
"It's a bit of an eye-opener. As space gets more crowded, the magnitude of this effect will only be more, not less."
This handout image supplied by the European Space Agency (ESA), shows a view of The Palms, Dubai as the SpaceX Dragon spacecraft passes below, in an image taken by ESA astronaut Tim Peake from the International Space Station on April 10, 2016.Photo by Tim Peake / ESA/NASA via Getty Images
Plenty more is coming as the race for consumer travel heats up. SpaceX has already launched over 1,000 Starlink communication satellites as it builds a new global internet infrastructure. Last year, the FCC approved 3,236 Amazon satellites that will all be in orbit as part of the mega-constellation "Project Kuiper" by 2029. While these aren't the only companies in the race to a global internet, SpaceX alone aspires to launch 42,000 satellites into space.
On Earth, we might enjoy faster internet speeds, but in observatories, researchers are concerned. Currently, scientists plan their observations around the orbit schedule of known objects. In a few years, the researchers of this letter write, that might prove impossible. An exponential increase in satellites will likely guarantee streaks in every telescope across the globe.
Slovakian astronomer Miroslav Kocifaj, part of the team behind this new research, believes this logjam in space could create such an intense background glow that we'll no longer be able to gaze out into the farthest reaches of space.
His team points to the 1979 resolution of the International Astronomical Union, which stated observatories should only be built in regions where light pollution adds less than 10 percent more light than normal skyglow. While they point out that "natural skyglow" is a debatable term, they're also concerned that the ambitious plans of private companies will ensure that nowhere will come in under that number. As the team writes:
"These results imply that diffuse night sky brightness produced by artificial space objects directly illuminated by the Sun may well have reached nowadays, and perhaps exceeded, what is considered a sustainability 'red line' for ground based astronomical observatory sites."
Just at the moment when we're reaching further into the cosmos, we seem to be boxing ourselves in. For millennia, we've started into the night sky and dreamed about the stars. Soon, it seems those dreams will be aimed at the junk we've placed there.
Stay in touch with Derek on Twitter. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
Humans are more likely to have "first contact" with an advanced alien civilization, according to a recent NASA-funded paper.
- A new paper outlines some of the most promising ways scientists and space agencies can search for evidence of extraterrestrial civilizations.
- Because of a concept called "contact inequality," the researchers suggested it's relatively unlikely humans will discover evidence of alien civilizations that have similar levels of technology to us.
- However, near-future technology could soon allow scientists to search for both highly advanced and less advanced alien civilizations.
How will humans discover the existence of extraterrestrial civilizations?
Unless aliens decide to visit Earth, the most likely answer is by scanning the skies for "technosignatures," which are observational evidence of technological or industrial activity in the Universe.
In a recent paper published in the journal Acta Astronautica, a team of NASA-funded researchers outlined some of the most promising ways scientists and space agencies could search for technosignatures. The paper included a somewhat surprising proposition: Humanity's "first contact" with aliens is likely to be with a much more advanced civilization.
In other words, there could be many alien civilizations throughout the Universe, or even in our galaxy, but if they're similar to us in terms of technological advancement, we probably can't spot them yet. The same goes for those human-like civilizations spotting us.
That's because the "cosmic footprints" of our civilization and theirs would be relatively small, compared to highly advanced alien civilizations. The researchers call this concept "contact inequality."
"It seems unlikely that civilizations with a relatively low level of technological development would enter into contact with each other, since that would require either very high sensitivities or highly visible engineering," reads the paper. "Less advanced civilizations lack the sensitivity needed to detect other civilizations unless they have built very large or luminous structures."
So, unless near-future technology like the James Webb Space Telescope enables scientists to find biomarkers on other planets, we're far more likely to discover more sophisticated civilizations.
How? The paper outlines a series of strategies that are either currently being practiced, could be practiced in conjunction with other astronomical projects, or could be developed in the near future.
A few of those strategies include searching for:
- Dyson spheres — gigantic structures that, in theory, could orbit stars and generate vast amounts of energy for civilizations.
- Near-Earth objects — space agencies could search the Moon, Mars or other space bodies for evidence of extraterrestrial artifacts, such as crashed probes.
- Abnormal spectra in planetary atmospheres — if aliens are conducting industrial activity on another planet, that planet's atmosphere would likely contain evidence of such activity.
- Night-time illumination
- Radio and laser signals
When thinking about the best ways to search for alien life, it helps to reverse the perspective: How would aliens know humans exist? With this question in mind, researchers who deal with technosignatures consider all of the signals humans are sending into space.
Some of our technosignatures are transmitted intentionally, like the Arecibo message humans sent toward the globular star cluster M13 in 1974. Others are unintentional, like night-time illumination and pollution-driven atmospheric changes.
To put the concept of technosignatures into perspective, researchers have developed a framework called ichnoscale. Ichnoscale ranks the size of a technosignature relative to what human technology is currently capable of producing.
The scale also ranks the number of potential targets throughout the Universe. For example, searching for a crashed alien probe on the Moon would represent one target, while scanning the stars for Dyson spheres would have millions of targets.
Together, these measurements help scientists estimate the most likely ways to discover evidence of alien civilizations. Of course, there's no guarantee that any one strategy will work, or that aliens even exist.
That's one reason why efforts to search for technosignatures have received little funding. But the researchers propose that many of these strategies could be tacked onto other astronomical missions at little cost.
Socas-Navarro et al.
And even if the searches turn up nothing, the researchers said the results would still provide "enormous ancillary benefits on solar system research and advance our knowledge about the objects being scrutinized," and would "establish quantitative upper bounds on certain types of technologies or developmental stages of civilizations in the solar neighborhood."
"The search for TS deals with questions that have profound implications on the future of humanity," the researchers concluded. "Perhaps one the most important is whether technological civilizations are ephemeral or, on the contrary, can be long lasting. A closely related question is whether space faring civilizations are common, and if humankind will eventually become one of them."
"We do not yet have any answers for these and other important questions but if we can start to explore the search parameter space, even in the absence of any detection we may be able to gain some valuable insights."
Sound waves behave quite differently on Mars than on Earth.
- NASA's Perseverance rover landed on Mars on February 18, and is currently preparing to begin its main mission of searching for signs of ancient life.
- The rover contains two microphone systems, one of which was recently used to capture sounds of the rover traveling at speeds below .01 mph.
- NASA hopes to return Perseverance's rock collection to Earth by 2031.
It's been over a month since Perseverance landed on Mars, where the rover will search for evidence of ancient life. Since the landing on February 18, Perseverance has returned images, conducted tests of its robotic arm and steering system, and recorded the sound of wind on the red planet.
This week, NASA released audio of the six-wheeled rover driving on the surface of Mars, captured by Perseverance's Entry Descent and Landing (EDL) microphones. The 16-minute recording features raw, unedited audio of the rover traveling 90 feet across the Martian surface at speeds approaching about .01 mph.
It's the first time a NASA rover has captured audio of itself driving.
It's also not the most pleasant recording.
"If I heard these sounds driving my car, I'd pull over and call for a tow," Dave Gruel, lead engineer for Mars 2020's EDL Camera and Microphone subsystem, told NASA's Jet Propulsion Laboratory. "But if you take a minute to consider what you're hearing and where it was recorded, it makes perfect sense."
It sounds like that partly because the rover's off-the-shelf EDL microphones weren't intended to capture sounds from the Martian terrain, but rather to record audio as the rover made its descent. And then there's the wheels.
"A lot of people, when they see the images, don't appreciate that the wheels are metal," Vandi Verma, a senior engineer and rover driver at NASA's Jet Propulsion Laboratory in Southern California, told NASA's Jet Propulsion Laboratory. "When you're driving with these wheels on rocks, it's actually very noisy."
Sound waves also behave differently on Mars. Compared to Earth, the red planet's atmosphere is colder, less dense and contains far more carbon dioxide. That means sound waves travel more slowly and quietly, and the atmosphere would absorb more higher-pitched sounds, an effect known as attenuation.
"The variations between Earth and Mars – we have a feeling for that visually," Verma said. "But sound is a whole different dimension: to see the differences between Earth and Mars, and experience that environment more closely."
NASA released an edited version of the audio that filters out some of the screeches and rattles.
Perseverance has a second microphone system included in its SuperCam instrument, which was designed to identify organic compounds on the Martian surface. SuperCam works by firing a laser at rocks and soil, and using a camera and spectrometers to study the composition of the materials.
"SuperCam's laser is uniquely capable of remotely clearing away surface dust, giving all of its instruments a clear view of the targets," Roger Wiens, the project's principal investigator, told NASA.
How do we fly a helicopter on Mars? It takes ingenuity and perseverance. Tune in on Thursday, March 11, 7pm PT (10p… https://t.co/FxHpBCMw8L— NASA JPL (@NASA JPL)1615339147.0
What's next for Perseverance? In April, NASA plans to conduct a test flight of the Ingenuity helicopter, which will fly near the rover to monitor the environment and provide imaging support. Soon after, Perseverance will spend one Mars year (687 Earth days) on its main mission: Collecting arguably the most scientifically significant rock collection in human history. NASA hopes the rocks will contain evidence that life once existed on Mars.
But it might take years to find out, considering that the ultimate goal is to send another spacecraft to Mars to return the rocks to Earth for closer inspection. For that retrieval mission, NASA and the European Space Agency have their sights on launching 2028 and returning in 2031.
The discovery could help astronauts find better ways to grow food in space.
- The bacteria were collected as part of a surveillance program that tasks astronauts with regularly collecting samples from eight sites aboard the International Space Station.
- The bacteria discovered on the space station belong to a family of bacteria that helps plants grow and blocks pathogens.
- Finding sustainable ways to grow food is critical to any long-term space mission.
Three previously unknown strains of bacteria were found growing in the International Space Station, according to a recent genetic analysis. The discovery could help scientists develop better ways to grow food on Mars.
The analysis, published in the journal Frontiers in Microbiology, describes how astronauts collected four strains of bacteria within the space station in 2011, 2015 and 2016. It was part of an ongoing surveillance program that tasks astronauts with monitoring eight sites of the space station for bacterial growth.
Astronauts have already sent hundreds of samples back to Earth for analysis, and thousands more are scheduled to be sent back on return missions.
The newly discovered strains belong to a family of bacteria called Methylobacteriaceae, which is commonly found in soil and freshwater. These bacteria help plants grow, fix nitrogen and stop pathogens.
International Space Station
So, how did these novel microbes get in the space station? They likely came from the plant-growing experiments that astronauts have been conducting for years aboard the ISS, such as the Advanced Plant Habitat, an automated growth chamber that grows plants in space so scientists can study them back on Earth.
The new strains could be beneficial to space farming. After all, it's already clear that the bacteria can survive the conditions of the space station, and the researchers wrote that the strains might possess "biotechnologically useful genetic determinants" that could help astronauts grow food on long-term missions, or on other planets.
"To grow plants in extreme places where resources are minimal, isolation of novel microbes that help to promote plant growth under stressful conditions is essential," study authors Kasthuri Venkateswaran and Nitin K. Singh said in a press release.
"Needless to say, the ISS is a cleanly-maintained extreme environment. Crew safety is the number 1 priority and hence understanding human/plant pathogens are important, but beneficial microbes like this novel Methylobacterium ajmalii are also needed."
To accelerate their understanding of how bacteria behaves in space, Singh and Venkateswaran proposed developing customized equipment that astronauts could use to analyze bacteria on the space station.
"Instead of bringing samples back to Earth for analyses, we need an integrated microbial monitoring system that collect, process, and analyze samples in space using molecular technologies," they said. "This miniaturized 'omics in space' technology — a biosensor development — will help NASA and other space-faring nations achieve safe and sustainable space exploration for long periods of time."
Genome-based phylogenetic tree showing the phylogenetic relationship of Methylobacterium ajmalii sp. nov. with members of the family Methylobacteriaceae.
Credit: Bijlani et al.
NASA is hoping to send humans to Mars by the 2030s, while private companies like SpaceX are aiming to reach the Red Planet this decade. For any Mars mission, developing sustainable ways to grow food is critical. That's mainly because it's impractical for astronauts to pack the food they'll need for the journey, which will take 14 months roundtrip, not including time spent on the planet.
Astronauts also need to stay healthy. The main problem with prepackaged food, besides its weight, is that the nutrients break over time. That's why NASA has been experimenting with growing various types of nutritious plants through projects like Veggie and the more recent Advanced Plant Habitat. These projects help scientists learn about the complexities of growing plants in microgravity, and how plants might grow on Mars.
NASA astronaut and Expedition 64 Flight Engineer Kate Rubins checks out radish plants growing for the Plant Habitat-02 experiment.
But growing plants in space isn't all about nutrition. NASA notes that plants are psychologically beneficial to people, both on Earth and in space. These psychological benefits might become especially important to astronauts on long-term missions millions of miles away from Earth.
Here's how astronaut Peggy Whitson, who worked aboard the International Space Station, described seeing plants in space for the first time:
"It was surprising to me how great 6 soybean plants looked," she told Space Daily. "I guess seeing something green for the first time in a month and a half had a real effect. From a psychological perspective, I think it's interesting that the reaction was as dramatic as it was. [...] I guess if we go to Mars, we need a garden!"