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.
The bird demonstrates cutting-edge technology for devising self-folding nanoscale robots.
Cornell University has just announced what may be the smallest origami bird ever folded. While a typical origami animal is the product of an artist's dexterous hands, the Cornell bird was folded by the strategic application of small electrical voltages. It had to be: The material of which the bird is comprised is just 30 atoms thick.
Creative expression isn't the point of the university's little avian — its construction previews principles and techniques that will lead to new generations of moving, nano-scaled robots that "can enable smart material design and interaction with the molecular biological world," says Dean Culver of the U.S. Army Combat Capabilities Development Command's Army Research Laboratory, which supported the research.
According to Cornell's Paul McEuen, "We humans, our defining characteristic is we've learned how to build complex systems and machines at human scales, and at enormous scales as well. But what we haven't learned how to do is build machines at tiny scales. And this is a step in that basic, fundamental evolution in what humans can do, of learning how to construct machines that are as small as cells."
The lead author of the paper describing the tiny bird is postdoctoral researcher Qingkun Liu. The paper, "Micrometer-Sized Electrically Programmable Shape Memory Actuators for Low-Power Microrobotics," is the cover story of the March 17 issue of the journal Science Robotics.
A minuscule swarm of helpers
The project is the result of a collaboration between physical scientist McEeuen and physicist Itai Cohen, both of Cornell's College of Arts and Sciences. It's already resulted in a (very) small herd of nanoscale machines and devices.
Cohen explains, "We want to have robots that are microscopic but have brains on board. So that means you need to have appendages that are driven by complementary metal-oxide-semiconductor (CMOS) transistors, basically a computer chip on a robot that's 100 microns on a side."
The idea is that these minuscule workhorses—a metaphor, no nanoscale origami horses yet exist—are released from a wafer, fold themselves into the desired form factor, and then go on about their business. Additional folding would endow them with motion as they work, change shapes to move their limbs and manipulate microscopic objects. The researchers anticipate that these nanobots will eventually be able to achieve similar functionality to their larger brethren.
Credit: nobeastsofierce/Adobe Stock
How a tiny robot is made and works
The project combines materials science with chemistry, since the folding is achieved with the strategic deployment of electrochemical reactions. Liu explains, "At this small scale, it's not like traditional mechanical engineering, but rather chemistry, material science, and mechanical engineering all mixed together."
"The hard part," says Cohen, "is making the materials that respond to the CMOS circuits. And this is what Qingkun and his colleagues have done with this shape memory actuator that you can drive with voltage and make it hold a bent shape."
The bots are constructed from a nanometer-thick platinum layer that's coated with a titanium oxide film. Rigid panels of silicon oxide glass are affixed to the platinum. A positive voltage creates oxidation, forcing oxygen atoms into the platinum seams between the glass panels, and forcing platinum atoms out. This causes the platinum to expand, which bends the entire glass-platinum structure to a desired angle.
Because the oxygen atoms collect to form a barrier, a bend is retained even after the charge is switched off. To undo a fold, a negative charge can be applied that removes the oxygen atoms from the seam, allowing it to relax and unbend.
This all happens very quickly — a machine can fold itself within just 100 milliseconds. The process is also repeatable. The team reports that a bot can flatten and refold itself thousands of times, and all it takes is a single volt of electricity.
Artistry after all
None of this really removes what one might consider the artistry. Working out how and where to apply voltages to effect the desired shape is not a simple thing to do. McEuen says, "One thing that's quite remarkable is that these little tiny layers are only about 30 atoms thick, compared to a sheet of paper, which might be 100,000 atoms thick. So it's an enormous engineering challenge to figure out how to make something like that have the kind of functionalities we want."
Still, the group is getting quite good at microscopic robotics, and has already been awarded the Guinness World Record for assembling the smallest-ever walking robot. The little 4-legged dude is 40 microns wide and between 40 and 70 microns long. They're angling for a new record with their 60-micron-wide origami bird.
Says Cohen, "These are major advances over current state-of-the-art devices. We're really in a class of our own."
Learn all about mechanical design, product development, material selection, manufacturing, and so much more.
- If you've always had an interest in mechanical engineering and design, these fives courses will fuel your curiosity.
- The Mechanical Engineer and Design Certification Bundle packs 375 lessons and over 17 hours of content for only $30.
- Learn all about mechanical design, product development, material selection, manufacturing, and so much more.
For those who have always had a strong interest in mechanical design, product development, and everything else that falls under this category, this is your chance to fuel your curiosity. The Complete Mechanical Engineer and Design Certification Bundle presents the perfect opportunity to get started — or at least try your hand at it before committing to expensive and time-consuming schooling.
Each student will receive access to 375 lessons broken down into 17 hours worth of training on all things mechanical engineering and design. Led by Mufaddai Rasheed, a mechanical engineer, inventor, and instructor with an average rating of 4.2 out of 5 stars, the training will start off with an inside look into the design and product development process. This will help provide a holistic perspective alongside concrete examples.
Then, it will continue to the basics of material selection, manufacturing selection, sheet metal design, and fundamentals of mechanics behind machine design. Whether you're a student, already an engineer, or just an enthusiast, these courses will inspire you in a number of ways.
It's no wonder this Mechanical Engineer and Design Certification Bundle is worth nearly $1,000, given all the detailed instruction and training behind the course. But lucky for you, it's discounted to just $29.99 for a limited time.
Who knows, you could even take what you've learned from these courses and use it as your first step to a potential new career.
Prices subject to change.
When you buy something through a link in this article or from our shop, Big Think earns a small commission. Thank you for supporting our team's work.
The satellite would burn instead of becoming more space debris.
- Orbiting around Earth are hundreds of thousands of bits of space debris.
- Some of this stuff comes plummeting down eventually, but not enough of it.
- Wood satellites would burn up in the atmosphere without falling on anyone or anything.
It makes sense that this idea comes from the country that brought us origami, those lovely and often diabolically complicated artworks of folded paper. With Earth now surrounded by an orbiting junkyard of satellites, scientists at Kyoto University and Sumitomo Forestry in Japan have proposed a surprising solution: satellites made of wood.
It's a mess up there
Credit: JohanSwanepoel/Adobe Stock
NASA is currently tracking over 500,000 pieces of satellite debris circling the Earth. These bits of mostly aluminum junk whip around the planet as fast as 17,500 mph and constitute a floating minefield that active and manned space vehicles have to find their way through without being struck, or worse, punctured. And those are just the bits large enough to be tracked—those bigger than a marble. There are many more too small to keep an eye on. And the situation is getting worse, with projects such as SpaceX's estimated 42,000 satellites or Amazon's Kuiper project.
The wood satellites being developed won't do much to solve that problem. However, they will help out with another one: what happens to space debris when its orbit decays and it falls back to Earth? We've been lucky so far. No serious impacts have yet been documented, but with all the discarded metal up there, it seems only a matter of time until something hits somebody or some important thing here on the ground. On top of that, some of it never falls all the way down, and is left as tiny bits of floating metal in the atmosphere.
Japanese astronaut and professor at Kyoto University Takao Doi tells the BBC, "We are very concerned with the fact that all the satellites which re-enter the Earth's atmosphere burn and create tiny alumina particles which will float in the upper atmosphere for many years."
(Fun side note: During Doi's visit to the ISS in March 2008, he became the first person to throw a boomerang in space. It was designed specifically for microgravity.)
The proposed wooden satellites to be launched by 2023 will simply burn up harmlessly on their way down through the atmosphere.
Credit: Geran de Klerk/Unsplash
If anyone knows how to construct a wood satellite, it would be Sumitomo Forestry, a company that has been foresting and developing wood products for 400 years. Their website declares that "Happiness grows from trees." In addition to the satellite project, the company is also in the process of designing a mostly wood, $5.8 billion Tokyo skyscraper to be completed by 2041.
The proposed satellites won't be made of just any wood. The researchers consider its exact formulation to be a trade secret, releasing little in the way of detail. It is known that it will have to be resistant to the temperature extremes it will encounter in space, and the scientists are reportedly considering both the basic material to be used as well as special wood-derived coatings.
The wooden satellites may have some advantages in functionality. With wood not being an obstacle to various communication wavelengths, the devices may need less extensive antennae.
Even so, the proposed satellites, though novel and sort of poetic, may not ultimately be of much help. Satellite casings are just a small part of the space-junk problem—their metal and plastic insides are also left up there to bang into other stuff. There are also lots of spent rocket boosters and such in orbit.
All of which brings us back to the larger issue of all the debris that never falls back to Earth, as the wooden satellites are meant to. The problem with all this stuff isn't what happens upon re-entry. It never re-enters at all, circling the planet ad infinitum as part of that great garbage dump in the sky.
Boston Dynamics' notorious robot goes on an interplanetary mission.
- NASA's Jet Propulsion Laboratory announces the deployment of a robotic "dog" for Mars exploration.
- The robot is a modified Boston Dynamics cyberdog familiar to the internet from YouTube videos over the last few years.
- The bot will be autonomous and smart enough to explore Martian caves that may one day provide shelter for human visitors to the Red Planet.
While Mars rovers have been and are unquestionably amazing, they're not the most adaptable or speedy little bots. Curiosity, for example, rolls across flat-ish parts of the Red Planet's surface at a decidedly un-blistering .09 miles per hour. That's about a third as fast as most people walk.
At the December 14, 2020 meeting of American Geophysical Union (AGU), held online this year, NASA/JPL-Caltech announced a new family of robotic explorers referred to as "Mars Dogs."
They're calling it "Au-Spot," and it's based on Boston Dynamics' infamous Spot robot that we've been seeing evolve over the last few years in YouTube videos. We've watched it survive falling down and getting kicked, and we've even seen it dance to "Uptown Funk." Spot has already evoked all kinds of emotions. It's creepy enough to drive an episode of "Black Mirror," and even without a face—or head—it's also somehow oddly endearing.
In a way, it's the abuse we've seen Spot suffer on YouTube that makes it such an ideal candidate for Mars missions. If Au-Spot falls over, it can right itself, a not insignificant capability when exploring alien terrain—it's one of the current rovers' most significant shortcomings. "Toppling does not mean mission failure," noted the scientists introducing the bot. "Using recovery algorithms, the robot can self-right from a multitude of falls."
The 70-pound Au-Spot is also capable of moving three times faster than existing rovers.
This means that Au-Spot will be ideal for exploring Martian caves, an area of great interest to those planning future manned missions to the planet. Satellite images of the red planet have revealed over 1,000 potential cave openings already. It may be possible on such journeys for humans to shelter in caves away from the planet's brutal dusts storms, extreme cold, and punishing UV radiation. These places, however, are not places into which current rovers can be sent.
On the other hand, Au-Spot's remarkable flexibility and smarts will allow Earth-bound scientists to see if the caves can really be of use to future astronauts. The bot pup can get down into such caves and then get itself back out. While there, it can produce 3D maps of the terrain thanks to onboard LIDAR. Built-in AI allows the bot to learn the terrain too, so it can avoid entrapment or damage from collisions with obstacles. It strategically deploys communications modules along the way to keep its command personnel appraised of what it's doing when it's beneath the surface.
Au-Spot can even intelligently choose between multiple pathways forward, making it a far more flexible tool than current rovers. Most things that rovers do are pre-programmed routines—improvisation requires communicating with a human controller back on Earth some 22 minutes away as the signal flies.
The rise of Au-Spot
Au-Spot is the child of a team of 60 scientists and engineers working together as CoSTAR, or the Collaborative SubTerranean Autonomous Resilient Robots. They've customized a factory-fresh Spot, outfitting it with the NeBula (Networked Belief-aware Perceptual Autonomy) system that makes it autonomous enough to successfully navigate new environments, as shown in the DARPA Subterranean Robotics Challenge video above.
To get Au-Spot mission-ready, the CoSTAR team is putting it through its paces here on Earth. In addition to sending it up and down staircases and such, it's gone on field trips to Northern California's Tulelake lava tubes for some practice on Mars-like terrain and some cave exploration as well.
At the presentation, the CoSTAR scientists predicted, "These behaviors could one day enable revolutionary scientific missions to take place on the Martian surface and subsurface, thereby pushing the boundaries of NASA's capability in exploring traditionally inaccessible sites."