The ‘future’ of space travel just passed into the past


  • 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 impulses from the EmDrive that seemed to prove its validity as a technology.
  • A new authoritative study says no, those results were simply “false positives.”

  • When Roger Shawyer’s EmDrive was first proposed in 2001, it seemed too good to be true. The proposed electromagnetic thruster (“Em” for short) did not need fuel and was therefore so light that it promised to allow travelers to traverse the cosmos at unprecedented speeds. It does not matter that the operation of the EmDrive seems to violate Newton’s Third Law of Motion, that every action produces an equal and opposite reaction.

    Now it seems that, yes, it is
    it was too good to be true. Scientists at the Dresden University of Technology (TU Dresden) seem to have conclusively shown that the EmDrive, in fact, does not produce any thrust. They provide compelling evidence that the small hints of push in earlier research were simply false positives produced by external forces.

    How EmDrive is supposed to work


    Credit: AndSus / Adobe Stock

    In the EmDrive, says the company that owns the rights to the invention, “the thrust is produced by amplifying the radiation pressure of an electromagnetic wave propagated through a resonant waveguide assembly.” In simpler words, trapped microwaves bounce around a specially shaped container, producing a thrust that pushes everything forward.

    They also state that while the EmDrive is not exactly in terms of talking to Newton’s Third Law, the company says it is perfectly in line with the second:

    “This is based on Newton’s Second Law, where force is defined as the rate of change of momentum. Therefore, an electromagnetic (EM) wave, traveling at the speed of light, has a certain moment that is will transfer to a reflector, resulting in a small force. ”

    The interest in the EmDrive has been understandable considering what it was supposed to do. Talking to
    Popular mechanics Last year, Mike McCulloch, DARPA’s EmDrive research leader, described how the engine could “transform space travel and see spacecraft silently taking off from launch pads and reaching beyond the solar system.” He mentioned his enthusiasm for being able to get from here to Proxima Centauri, 4,2465 light-years away, in just 90 human years.

    It does not work. If it does. No, it is not.

    NASA Eagleworks EmDriveCredit: NASA / Wikimedia Commons

    DARPA, which is part of the US Department of Defense, is just one of the organizations investigating claims made by EmDrive. In 2018, the agency invested $ 1.3 million to study the device in an investigation that will conclude this May, unless there are important last-minute advances.

    Teams around the world have been testing Shawyer’s idea since it was introduced and published often conflicting test results. This may have to do with the fact that teams that detected any thrust from EmDrive have reported extremely small amounts, measured in milliNewtons (mN). One mN equals approximately 0.00022 pounds of force.

    As Paul Sutter wrote in an op-ed for Space.com:

    “Since the introduction of the EmDrive concept in 2001, every few years a group claims to have measured a net force coming from their device. But these researchers are measuring an incredibly small effect: a force so small that it couldn’t even move a piece of paper. This leads to significant statistical uncertainty and measurement error. ”

    To get an idea of ​​how miniscule these results are, consider that the possible push force reported by NASA in 2014 of 30-50 micro-Newtons is roughly equivalent to the weight of a large ant. Chinese researchers have claimed the detection of 720 mN in their tests. That would be 72 grams of thrust. An iPhone 11 with a case weighs 219 grams.

    Too small to stand out from background noise

    These small amounts of EmDrive oomph are at the heart of what the TU Dresden researchers say: 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 articles. The title of one “EmDrive High Precision Thrust Measurements and Elimination of False Positive Effects” tells the story. The other two studios are here and here.

    When the UT Dresden team turned on their EmDrive based on NASA’s EmDrive, they too witnessed small amounts of apparent thrust.

    However, says Martin Tajmar from UT Dresden to the German media outlet GreWi, they soon realized what was happening: “When power flows into the EmDrive, the motor heats up. This also causes the fasteners of the scale deform, causing the scale to move to a new zero point. We were able to avoid that in an improved structure. ”

    Putting the brakes on the results of other researchers, the study authors write:

    “Using geometry and operating conditions close to the model of White et al. Who reported positive results published in the peer-reviewed literature, we did not find thrust values ​​within a wide frequency band that includes various resonant frequencies. Our data limit any anomalous thrust below the equivalent force of 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.

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