Explaining EmDrive, the ‘physics-defying’ thruster even NASA is puzzled over

Even if you don’t keep up with developments in space propulsion technology, you’ve still probably heard about the EmDrive. You’ve probably seen headlines declaring it the key to interstellar travel, and claims that it will drastically reduce travel time across our solar system, making our dreams of people walking on other planets even more of a reality. There have even been claims that this highly controversial technology is the key to creating warp drives.

These are bold claims, and as the great cosmologist and astrophysicist Carl Sagan once said, “extraordinary claims require extraordinary evidence.” With that in mind, we thought it’d be helpful to break down what we know about the enigmatic EmDrive, and whether it is, in fact, the key to mankind exploring the stars.

So without further ado, here’s absolutely everything you need to know about the world’s most puzzling propulsion device.

 

What is the EmDrive?

See, the EmDrive is a conundrum. First designed in 2001 by aerospace engineer Roger Shawyer, the technology can be summed up as a propellantless propulsion system, meaning the engine doesn’t use fuel to cause a reaction. Removing the need for fuel makes a craft substantially lighter, and therefore easier to move (and cheaper to make, theoretically). In addition, the hypothetical drive is able to reach extremely high speeds — we’re talking potentially getting humans to the outer reaches of the solar system in a matter of months.

We’re talking potentially getting humans to the outer reaches of the solar system in a matter of months. The issue is, the entire concept of a reactionless drive is inconsistent with Newton’s conservation of momentum, which states that within a closed system, linear and angular momentum remain constant regardless of any changes that take place within said system. More plainly: Unless an outside force is applied, an object will not move.

 

Reactionless drives are named as such because they lack the “reaction” defined in Newton’s third law: “For every action there is an equal and opposite reaction.” But this goes against our current fundamental understanding of physics: An action (propulsion of a craft) taking place without a reaction (ignition of fuel and expulsion of mass) should be impossible. For such a thing to occur, it would mean an as-yet-undefined phenomenon is taking place — or our understanding of physics is completely wrong.

How does the EmDrive “work?”

Setting aside the potentially physics-breaking improbabilities of the technology, let’s break down in simple terms how the proposed drive operates. The EmDrive is what is called an RF resonant cavity thruster, and is one of several hypothetical machines that use this model. These designs work by having a magnetron push microwaves into a closed truncated cone, then push against the short end of the cone, and propel the craft forward.

This is in contrast to the form of propulsion current spacecraft use, which burn large quantities of fuel to expel a massive amount of energy and mass to rocket the craft into the air. An often-used metaphor for the inefficacy of this is to compare the particles pushing against the enclosure and producing thrust to the act of sitting in a car and pushing a steering wheel to move the car forward.

While tests have been done on experimental versions of the drive — with low energy inputs resulting in a few micronewtons of thrust (about as much force as the weight of a penny) — none of the findings have ever been published in a peer-reviewed journal. That means that any and all purportedly positive test results, and the claims of those who have a vested interest in the technology, should be taken with a very big grain of skepticism-flavored salt. It’s likely that the thrust recorded was due to interference or an unaccounted error with equipment.

Until the tests have been verified through the proper scientific and peer-reviewed processes, one can assume the drive does not yet work. Still, it’s interesting to note the number of people who have tested the drive and reported achieving thrust:

• In 2001, Shawyer was given a £45,000 grant from the British government to test the EmDrive. His test reportedly achieved 0.016 Newtons of force and required 850 watts of power, but no peer review of the tests verified this. It’s worth noting, however, that this number was low enough that it was potentially an experimental error.
• In 2008, Yang Juan and a team of Chinese researches at the Northwestern Polytechnical University allegedly verified the theory behind RF resonant cavity thrusters, and subsequently built their own version in 2010, testing the drive multiple times from 2012 to 2014. Tests results were purportedly positive, achieving up yo 750 mN (millinewtons) of thrust, and requiring 2,500 watts of power.
• In 2014, NASA researchers, tested their own version of an EmDrive, including in a hard vacuum. Once again, the group reported thrust (about 1/1,000 of Shawyer’s claims), and once again, the data was never published through peer-reviewed sources. Other NASA groups are skeptical of researchers’ claims, but in their paper, it is clearly stated that these findings neither confirm nor refute the drive, instead calling for further tests.
• In 2015, that same NASA group tested a version of chemical engineer Guido Fetta’s Cannae Drive (née Q Drive), and reported positive net thrust. Similarly, a research group at Dresden University of Technology also tested the drive, again reporting thrust, both predicted and unexpected.
• Yet another test by a NASA research group, Eagleworks, in late 2015 seemingly confirmed the validity of the EmDrive. The test corrected errors that had occurred in the previous tests, and surprisingly, the drive achieved thrust. However, the group has not yet submitted their findings for peer review. It’s possible that other unforeseen errors in the experiment may have cause thrust (the most likely of which is that the vacuum was compromised, causing heat to expand air within it testing environment and move the drive). Whether the findings are ultimately published or not, more tests need to be done. That’s exactly what Glenn Research Center in Cleveland, Ohio, NASA’s Jet Propulsion Laboratory, and Johns Hopkins University Applied Physics Laboratory intend to do. For EmDrive believers, there seems to be some hope.

Implications of a working EmDrive

It’s easy to see how many in the scientific community are wary of EmDrive and RF resonant cavity thrusts altogether. But on the other hand, the wealth of studies raises a few questions: Why is there such a interest in the technology, and why do so many people wish to test it? What exactly are the claims being made about the drive that make it such an attractive idea? While everything from atmospheric temperature-controlling satellites, to safer and more efficient automobiles have been drummed up as potential applications for the drive, the real draw of the technology — and the impetus for its creation in the first place — is the implications for space travel.

Spacecraft equipped with a reactionless drive could potentially make it to the moon in just a few hours, Mars in two to three months, and Pluto within two years. These are extremely bold claims, but if the EmDrive does turn out to be a legitimate technology, they may not be all that outlandish. And with no need to pack several tons-worth of fuel, spacecraft become cheaper and easier to produce, and far lighter.
For NASA and other such organizations, including the numerous private space corporations like SpaceX, lightweight, affordable spacecraft that can travel to remote parts of space fast are something of a unicorn. Still, for that to become a reality, the science has to add up.

Shawyer is adamant that there is no need for pseudoscience or quantum theories to explain how EmDrive works. Instead, he believes that current models of Newtonian physics offer an explanation, and has written papers on the subject, one of which is currently being peer reviewed. He expects the paper to be published sometime this year. While in the past Shawyer has been criticized by other scientists for incorrect and inconsistent science, if the paper does indeed get published, it may begin to legitimize the EmDrive and spur more testing and research.

Spacecraft equipped with a reactionless drive could potentially make it to the Moon in just a few hours.

Despite his insistence that the drive behaves within the laws of physics, it hasn’t prevented him from making bold assertions regarding EmDrive. Shawyer has gone on record saying that this new drive produced warp bubbles which allow the drive to move, claiming that this is how NASA’s test results were likely achieved. Assertions such as these have garnered much interest online, but have no clear supporting data and will (at the very least) require extensive testing and debate in order to be taken seriously by the scientific community — the majority of which remain skeptical of Shawyer’s claims.

Colin Johnston of the Armagh Planetarium wrote an extensive critique of the EmDrive and the inconclusive findings of numerous tests. Similarly, Corey S. Powell of Discovery wrote his own indictment of both Shawyer’s EmDrive and Fetta’s Cannae Drive, as well as the recent fervor over NASA’s findings. Both point out the need for greater discretion when reporting on such instances. Professor and mathematical physicist, John C. Baez expressed his exhaustion at the conceptual technology’s persistence in debates and discussions, calling the entire notion of a reactionless drive “baloney.” His impassioned dismissal echoes the sentiments of many others.

Shawyer’s EmDrive has been met with enthusiasm elsewhere, including the website NASASpaceFlight.com — where information about the most recent Eagleworks’ tests was first posted — and the popular journal New Scientist, which published a favorable and optimistic paper on EmDrive. (The editors later issued a statement that, despite enduring excitement over the idea, they should have shown more tact when writing on the controversial subject.)

Clearly, the EmDrive and RF resonant cavity thruster technology have a lot to prove. There’s no denying that the technology is exciting, and that the number of “successful” tests are interesting, but one must keep in mind the physics preventing the EmDrive from gaining any traction, and the rather curious lack of peer-reviewed studies done on the subject. If the EmDrive is so groundbreaking (and works), surely people like Shawyer would be clamoring for peer-reviewed verification.

A demonstrably working EmDrive could open up exciting possibilities for both space and terrestrial travel — not to mention call into question our entire understanding of physics. However, until that comes to pass, it will remain nothing more than science fiction.

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Scientists find evidence of gravitational waves predicted by Einstein

File image – An image from a simulation showing how matter might be moved around in the extreme environment around a black hole. (Özel/Chan) (Özel/Chan)

After decades of searching, scientists announced Thursday that they have detected gravitational waves which are ripples in the fabric of space-time that were predicted by Einstein.

 

An international team of astrophysicist said that they detected the waves from the distant crash of two black holes, using a $1.1 billion instrument. The Ligo Collaboration was behind the discovery and it has been accepted for publication in the journal Physical Review Letters.

Related: Meteorite probably didn’t kill man in India, NASA says

“We have detected gravitational waves,” Caltech’s David H. Reitze, executive director of the LIGO Laboratory, told journalists at a news conference in Washington DC.

The news, according to the Associated Press, is being compared by at least one theorist to Galileo taking up a telescope and looking at the planets and the biggest discovery since the discovery of the Higgs particle. It has stunned the world of physics and astronomy, prompting scientists to say it the beginning of a new era in physics that could lead to scores more astrophysical discoveries and the exploration of the warped side of the universe.

“Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” Reitze said in a statement.

Related: Hundreds of hidden galaxies glimpsed behind Milky Way

The discovery confirms a major prediction of Albert Einstein’s 1915 general theory of relativity. Gravitation waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere.

Not only have they fascinated by scientist by found their way into pop culture – namely through movies such as “Back To The Future,” where the space-time continuum was used a medium for the DeLorean time machine to go back in time. It also featured in the “Terminator” series.

Their existence was first demonstrated in the 1970s and 1980s by Joseph Taylor, Jr., and colleagues. In 1974, Taylor and Russell Hulse discovered a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the 1993 Nobel Prize in Physics.

Related: White House proposes $19 billion NASA budget

In the latest breakthrough, the gravitational waves were detected on Sept. 14, 2015 by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington.

Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About three times the mass of the Sun was converted into gravitational waves in a fraction of a second — with a peak power output about 50 times that of the whole visible universe.

By looking at the time of arrival of the signals — the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford — scientists can say that the source was located in the Southern Hemisphere.

Related: New star puts on a show in stunning image

According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. In a final fraction of a second, the two black holes collide and form one massive black hole. A portion of their combined mass is converted to energy, according to Einstein’s formula E=mc2, and this energy is emitted as a final strong burst of gravitational waves.

These are the gravitational waves that LIGO observed.

“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe — objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” Caltech’s Kip Thorne said.

 

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Surprise! Monster Black Hole Found in Dwarf Galaxy

Size doesn’t matter…

This image shows a huge galaxy, M60, with the small dwarf galaxy that is expected to eventually merge with it. (NASA/Space Telescope Science Institute/European Space Agency)

Astronomers have just discovered the smallest known galaxy that harbors a huge, supermassive black hole at its core.

The relatively nearby dwarf galaxy may house a supermassive black hole at its heart equal in mass to about 21 million suns. The discovery suggests that supermassive black holes may be far more common than previously thought.

A supermassive black hole millions to billions of times the mass of the sun lies at the heart of nearly every large galaxy like the Milky Way. These monstrously huge black holes have existed since the infancy of the universe, some 800 million years or so after the Big Bang. Scientists are uncertain whether dwarf galaxies might also harbor supermassive black holes. [Watch a Space.com video about the new dwarf galaxy finding]

“Dwarf galaxies usually refer to any galaxy less than roughly one-fiftieth the brightness of the Milky Way,” said lead study author Anil Seth, an astronomer at the University of Utah in Salt Lake City. These galaxies span only several hundreds to thousands of light-years across, much smaller than the Milky Way’s 100,000-light-year diameter, and they “are much more abundant than galaxies like the Milky Way,” Seth said.

The researchers investigated a rarer kind of dwarf galaxy known as an ultra-compact dwarf galaxy; such galaxies are among the densest collections of stars in the universe. “These are found primarily in galaxy clusters, the cities of the universe,” Seth told Space.com.

This is an illustration of the supermassive black hole located in the middle of the very dense galaxy M60-UCD1. It weighs as much as 21 million times the mass of our Sun. Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way! Despite its size it is pretty crowded, containing some 140 million stars. Because no light can escape from the black hole, it appears simply in silhouette against the starry background. The black hole’s intense gravitational field warps the light of the background stars to form ring-like images just outside the dark edges of the black hole’s event horizon. (Combined observations by the NASA/ESA Hubble Space Telescope and NASA’s Gemini North telescope determined the presence of the black hole inside M60-UCD1.)

Now, Seth and his colleagues have discovered that an ultra-compact dwarf galaxy may possess a supermassive black hole, which would make it the smallest galaxy known to contain such a giant.

The astronomers investigated M60-UCD1, the brightest ultra-compact dwarf galaxy currently known, using the Gemini North 8-meter optical-and-infrared telescope on Hawaii’s Mauna Kea volcano and NASA’s Hubble Space Telescope. M60-UCD1 lies about 54 million light-years away from Earth. The dwarf galaxy orbits M60, one of the largest galaxies near the Milky Way, at a distance of only about 22,000 light-years from the larger galaxy’s center, “closer than the sun is to the center of the Milky Way,” Seth said.

The scientists calculated the size of the supermassive black hole that may lurk inside M60-UCD1 by analyzing the motions of the stars in that galaxy, which helped the researchers deduce the amount of mass needed to exert the gravitational field seen pulling on those stars. For instance, the stars at the center of M60-UCD1 zip at speeds of about 230,000 mph (370,000 km/h), much faster than stars would be expected to move in the absence of such a black hole.

The supermassive black hole at the core of the Milky Way has a mass of about 4 million suns, taking up less than 0.01 percent of the galaxy’s estimated total mass, which is about 50 billion suns. In comparison, the supermassive black hole that may lie in the core of M60-UCD1 appears five times larger than the one in the Milky Way, and also seems to make up about 15 percent of the dwarf galaxy’s mass, which is about 140 million suns.

“That is pretty amazing, given that the Milky Way is 500 times larger and more than 1,000 times heavier than the dwarf galaxy M60-UCD1,” Seth said in a statement.

Astronomers have debated the nature of ultra-compact dwarf galaxies for years — whether they were extremely massive clusters of stars that were all born together, or whether they were the centers or nuclei of large galaxies that had their outer layers stripped away during collisions with other galaxies. These new findings hint that ultra-compact dwarf galaxies are the stripped nuclei of larger galaxies, because star clusters do not host supermassive black holes.

The researchers suggest M60-UCD1 was once a very large galaxy, with maybe 10 billion stars, “but then it passed very close to the center of an even larger galaxy, M60, and in that process, all the stars and dark matter in the outer part of the galaxy got torn away and became part of M60,” Seth said in a statement. “That was maybe as much as 10 billion years ago. We don’t know.”

Eventually, M60-UCD1 “may merge with the center of M60, which has a monster black hole in it, with 4.5 billion solar masses — more than 1,000 times bigger than the supermassive black hole in our galaxy,” Seth said in a statement. “When that happens, the black hole we found in M60-UCD1 will merge with that monster black hole.”

The astronomers suggest the way stars move in many other ultra-compact dwarf galaxies hints that they may host supermassive black holes, as well. All in all, the scientists suggest that ultra-compact dwarf galaxies could double the number of supermassive black holes known in the nearby regions of the universe. The researchers are participating in ongoing projects that may provide conclusive evidence for supermassive black holes in four other ultra-compact dwarfs.

The scientists detailed their findings in the Sept. 18 issue of the journal Nature.

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Monster Galaxy Cluster Is Biggest Ever in the Early Universe

This image of the massive galactic cluster IDCS 1426 combines data taken by three major NASA telescopes. The off-center core of X-rays is shown in blue-white near the middle of the cluster, and was captured by Chandra. Visible light from the Hubble Space Telescope is green, and infrared light from Spitzer is shown in red. (NASA, ESA, and M. Brodwin (University of Missouri))

KISSIMMEE, Fla. ─ The most massive collection of galaxies in the early universe has been spotted. Although not the largest collection of galaxies ever found, it holds the record as the largest group in the early universe, appearing surprisingly old for the time.

“Of all the structures we’ve ever seen, this is the most massive in the first 4 billion years of the universe,” astronomer Mark Brodwin, of the University of Missouri at Kansas City, said at a news conference unveiling the discovery here at the 47th annual meeting of the American Astronomical Society. Brodwin led the team that identified the evolved ancient galaxy cluster.

“It should be consistent with the largest cluster in the observable universe.” [The History and Structure of the Universe in Images]

A young monster

Galaxy clusters are collections of galaxies that formed once stars and individual galaxies had been built. Gravity binds hundreds of thousands of galaxies together in collections so large, they can distort the fabric of space-time. According to present understanding, the massive objects should take billions of years to form.

In 2012, scientists used NASA’s Spitzer Space Telescope to measure the galactic cluster IDCS 1426, which lies approximately 10 billion light-years from Earth. Because light takes a full year to travel the distance of 1 light-year, that means astronomers are able to study the cluster as it appeared when the universe was only 3.8 billon years old. [Related: How Old Is the Universe?]

Initial estimates suggested that IDCS 1426 contained an enormous mass at a significant distance, but were not conclusive. Brodwin and his colleagues decided to use NASA’s Hubble Space Telescope, Keck Observatory and Chandra X-ray Observatory to refine measurements of the mass of the cluster, using three different methods.

Hubble and Keck studied IDCS 1426 in optical light. Because clusters bend space-time, they are frequently used as natural magnifying glasses to observe objects behind the cluster in a process known as gravitational lensing. A more massive cluster produces a higher gravitational force that bends the light more strongly; by observing how the light traveled around the cluster, the scientists could calculate its weight.

At the same time, Chandra studied the object in the X-ray wavelength. The more massive a galaxy cluster is, the more the gas within it is compressed and heated, producing more X-rays. By observing those X-rays, the scientists were able to compute the mass of the cluster.

All three observations independently provided a mass 250 trillion times higher than the mass of the sun, or 1,000 times more massive than the Milky Way.

IDCS 1426 is not the most massive galaxy cluster in the universe. That distinction is held by a massive cluster that lies only 7 billion light-years from Earth. Known informally as ‘El Gordo,’the hefty cluster weighs in at a whopping 3 quadrillion times the mass of the sun (that’s 3 followed by 15 zeros, or one thousand million million). However, according to Brodwin, the cluster is on track to grow into something that large.

“Statistically speaking, it is a progenitor of ‘El Gordo,'” he said.

After another 3 billion years, the ancient collection should weigh in fairly close to the larger cluster.

The research will be published in The Astrophysical Journal, though a preprint of the study is available on the site Arxiv.org.

A sloshing core

The enormous mass of IDCS 1426 in the early in the life of the universe isn’t the only indication of its unusual evolution. In addition to studying its mass, Chandra also took the temperature of the heart of the distant cluster, and found something surprising.

The core of a galactic cluster is an active place, with objects moving around and bumping into one another. This ongoing activity keeps the core hot for the cluster’s early lifetime. Once things slow down, however, conditions in the core begin to relax, and the center begins to release energy in the form of X-rays, causing the center to slowly cool.

Chandra revealed a bright knot of X-rays at the center of IDCS 1426 that were surprisingly cool. In fact, it is the first “cool core” cluster at such an early age in the universe. The cool heart of the cluster provides even more evidence for its formation early in the life of the universe.

“A cool core is a property of an evolved cluster,” Brodwin said.

A collision may have added the extra kick to the formation of the young cluster. The cool core lies not in the center of the IDCS 1426 but off to one side by a few hundred thousand light-years.

“When it is hit by another group or cluster, the cool core will slosh around like wine in the bottom of the wine glass,” Brodwin said.

“Eventually it will settle towards the center, but it hasn’t settled yet.”

All of these suggest an advanced age for the cluster that came as a surprise for a feature so early in the life of the universe.

“The cluster looks at least a billion years old,” Brodwin said.

“It probably really started forming 2 to 3 billion years earlier, which is very early for something of that size.”

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