EmDrive

For thrusters that use electrical power to change the velocity of spacecraft, see Electrically-powered spacecraft propulsion. For rocket that uses thrust from the momentum of emitted photons, see Photon rocket.
EmDrive
EmDrive experiment built by NASA Eagleworks laboratory in 2013
Country of originUnited States
Date2001
ApplicationSpacecraft thruster
StatusDevice concept
Performance
Thrust, sea-level0 N (0 ozf)[1]

The EmDrive is a concept for a thruster for spacecraft, first written about in 2001.[2][3][4][5] It is purported to generate thrust by reflecting microwaves inside the device, in a way that would violate the law of conservation of momentum and other laws of physics.[6][7][8][9][10] The concept has at times been referred to as a resonant cavity thruster.[11][12]

There is no official design for this device. Neither person who claims to have invented it has committed to an explanation for how it could operate as a thruster or what elements define it, making it hard to say definitively whether a given object is an example of an EmDrive. However, over the years, prototypes based on its public descriptions have been constructed and tested.

In 2016, Harold White's group at NASA observed a small apparent thrust from one such test,[13] however subsequent studies suggested this was a measurement error caused by thermal gradients.[14][15] In 2021, Martin Tajmar's group at the Dresden University of Technology replicated White's test, observing apparent thrusts similar to those measured by the NASA team, and then made them disappear again when measured using point suspension.[1]

No other published experiment has measured apparent thrust greater than the experiment's margin of error.[16] Tajmar's group published three papers in 2021 claiming that all published results showing thrust had been false positives, explaining each by outside forces. They concluded, "Our measurements refute all EmDrive claims by at least 3 orders of magnitude."[1]

  1. ^ a b c Delbert, Caroline (31 March 2021). "Scientists Just Killed the EmDrive". popularmechanics.com. Popular Mechanics. Retrieved 29 June 2021.
  2. ^ Cite error: The named reference Powell was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference JBIS 2016a was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference shawyertheory 9.3 was invoked but never defined (see the help page).
  5. ^ Breeze, Nick (29 July 2015). "Roger Shawyer, EmDrive Interview, 2015". Envisionation UK.
  6. ^ Cite error: The named reference NASA AIAA 2014 was invoked but never defined (see the help page).
  7. ^ "The Impossible Propulsion Drive Is Heading to Space". popularmechanics.com. 2 September 2016. Retrieved 9 October 2017.
  8. ^ Crew, Bec (6 September 2016). "The 'Impossible' EM Drive Is About to Be Tested in Space". sciencealert.com. Retrieved 9 October 2017.
  9. ^ "NASA Team Claims 'Impossible' Space Engine Works—Get the Facts". National Geographic. 21 November 2016. Archived from the original on 22 November 2016. Retrieved 9 October 2017.
  10. ^ Poitras, Colin (7 December 2016). "To Mars in 70 days: Expert discusses NASA's study of paradoxical EM propulsion drive". Phys.org. Retrieved 1 May 2018.
  11. ^ Templeton, Graham (16 September 2016). "Can the 'impossible' space drive survive falsification in orbit? – ExtremeTech". Extremetech. Retrieved 1 November 2017.
  12. ^ Hambling, David (7 August 2014). "10 questions about Nasa's 'impossible' space drive answered". Wired UK. Retrieved 1 November 2017.
  13. ^ Cite error: The named reference Nat Geo Peer review was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference tajmar20180514 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference tajmar20210401 was invoked but never defined (see the help page).
  16. ^ "'Impossible' EmDrive Space Thruster May Really Be Impossible". Space.com. Retrieved 3 September 2018.