Propellentless Drive Successfully Tested by NASA

Centauri Dreams: What We Want to Hear

And also XKCD 1404

Since posting that link, I've been running around the web, digging up articles and discussions on not just this 'Cannae Drive,' but the 'EM Drive' and the 'Woodward-Mach Effect' as well.

Seems to be a fair amount of debate as to whether this experiment was done in a vacuum. I have come across multiple conflicting accounts on that part of the test.

Another thing is the 'shape' of the device, which is apparently highly crucial, and something that *might* be overlooked by the 'conservation of momentum' people. My own analogy here:

1) You have a perfectly ordinary hamster, in a perfectly ordinary cubical hamster cage. No matter how energetic said hamster gets (barring a cheat of some sort), he's not going to be able to move said cage.

2) Now, put hamster in hamster ball. Now hamster rolls all over the place.

3) But...suppose you put hamster in a sealed, cylindrical 'wheel' that was not mounted. Now, hamster can move this device in two directions (forward and backward), but cannot move sideways.

but instead of a single hamster, we have billions (?) of photons, bouncing about in a container whose shape decrees the bulk of the impacts will be along the one side.

Another comparison might be that of dice. A normal cubical die has an even chance of landing on any of its six surfaces. But, if the die is unevenly balanced, then one number will appear far more often than it should. Maybe something similar is effect here, except with shape instead of distributed weight.

That said, I find it fascinating that NASA tested this at all, and went on to recommend further tests.

(Maybe one of these private space companies will build a test craft along these lines, launch it into orbit, aim it at Mars, and turn it loose. A demonstration like that works, it changes things).

via NASA Watch:

OutThere blog: Did NASA Validate an “Impossible” Space Drive? In a Word, No.

io9: Don't Get Too Excited About NASA's New Miracle Engine

From that last link:

Quote :

Restating: the researchers measured thrust when the drive was all set up to produce thrust, but they also measured thrust when it was set up to do nothing at all. That the null test article produced thrust is really suspicious. Either it's a measurement error, or this drive produces thrust by some mechanism that isn't explained by the semi-plausible physics backing it up and this breakthrough in spacecraft propulsion is working by some not-even-theoretical mechanism.

Now, which is more likely?

1. Eight days of initial tests on a piece of controversial technology in a NASA lab have proven all-new, extraordinary, physics-revolutionizing spacecraft propulsion in a manner so spectacular that the drive works even when it isn't set up to do anything at all; or
   
2. Somewhere in the testing process is some sort of procedural, mechanical, or interference error producing false results.

As someone who has done my fair share of novel research that didn't go exactly as expected, this conference abstract reads like the researchers were looking for extra eyeballs to figure out what about their testing rig might be flawed — not a grand announcement of a spectacular breakthrough. This has the potential to be cool, but at the moment, about the strongest thing that it's scientifically responsible to say about these test results is that the researchers need to revise their testing setup.

Lazarus-

I'd already found and read the second article you linked to.

However, the first article was new to me.  I found the debate in the comments section afterwards to be most interesting.  One poster linked to the original NASA paper.  Reading through that, it seems like the NASA team took a lot of measures to prevent contamination of the results - but still were not completely sure.  They also apparently did test the device in a vacuum, or near vacuum; the first part of the paper goes into the difficulties this caused.  

Quote :

To simulate the space pressure environment, the test rig is rolled into the test chamber. After sealing the chamber, the test facility vacuum pumps are used to reduce the environmental pressure down as far as 5x10E-6 Torr. Two roughing pumps provide the vacuum required to lower the environment to approximately 10 Torr in less than 30 minutes. Then, two high-speed turbo pumps are used to complete the evacuation to 5x10E-6 Torr, which requires a few additional days. During this final evacuation, a large strip heater (mounted around most of the circumference of the cylindrical chamber) is used to heat the chamber interior sufficiently to emancipate volatile substances that typically coat the chamber interior walls whenever the chamber is at ambient pressure with the chamber door open. During test run data takes at vacuum, the turbo pumps continue to run to maintain the hard vacuum environment. The high-frequency vibrations from the turbo pump have no noticeable effect on the testing seismic environment.

Quote :

F. Cannae Testing: Lessons Learned during Integration and Testing Almost six days were required from equipment delivery to first thrust measurement for test preparation and integration activities. The most significant challenge was RF system engineering, including manual frequency control of the RF test article. Lessons learned included:
 At ~1 GHz frequencies, RF signal leakage can be substantial if all interfaces are not properly RF shielded. All cables, components, and connectors must be designed or sealed (e.g., with conductive tape or a Faraday cage) to eliminate (or at least reduce) RF leak paths. Be aware of the circuit protection specifications on RF amplifiers.
 Manual control of the resonant cavity frequency will add a substantial amount of time to the test schedule. Eagleworks implemented an automated, phase-locked loop (PLL) frequency control circuit during a subsequent test campaign.
 Cable routing must be evaluated and designed to prevent ground loops. This was a not a significant challenge during this campaign, but it became more difficult after implementation of the PLL during a subsequent test campaign.
G. Cannae Testing: Summary of Results and Conclusions
The resistive RF Load evaluation indicated no significant systemic cause for torsion pendulum displacement. Based upon this observation, both test articles (slotted and unslotted) produced significant thrust in both orientations (forward and reverse). Test schedule constraints prevented multiple data points to be gathered in the reverse orientation, and the single data point for each test article is insufficient to allow comparative conclusions (between slotted and unslotted) to be drawn. However, for the forward thrust orientation, the difference in mean thrust between the slotted and unslotted was less than two percent. Thrust production was not dependent upon the slotting.

Quote :

Configuration Test Article Thrust Direction
Thrust Range (μN) Mean Thrust (μN)
Number of Test Runs
1A Slotted Forward 31.7 – 45.3 40.0 5
1B Slotted Reverse 48.5 48.5 1
2A Unslotted Forward 35.3 – 50.1 40.7 4
2B Unslotted Reverse 22.5 22.5 1
RF Load 50Ω Load N/A 0.0 0.0 2

Quote :

F. Tapered Cavity RF Evaluation, General Findings and Lessons Learned Overall, the biggest lesson learned was that RF tuning and optimization constraints are very challenging. We discovered early in the COMSOL® analysis process that just because you can achieve a great RF solution does not mean that it will be an ideal Q-thruster implementation.
There appears to be a clear dependency between thrust magnitude and the presence of some sort of dielectric RF resonator in the thrust chamber. The geometry, location, and material properties of this resonator must be evaluated using numerous COMSOL® iterations to arrive at a viable thruster solution. We performed some very early evaluations without the dielectric resonator (TE012 mode at 2168 MHz, with power levels up to ~30 watts) and measured no significant net thrust.
Numerous COMSOL® analysis runs also indicated a strong dependency between thrust magnitude and antenna type, location, orientation, and number of antenna feeds. Slight changes in antenna design and number of feeds changed the COMSOL® thrust prediction by a factor of three which forced our team to implement tighter configuration control protocols during testing to ensure close representation of as built hardware to the analyzed configuration.
Finally, our experience with the TE012 mode indicated that it is important to design the RF prototype such that any target mode of operation is as isolated as possible in the frequency domain to help ensure that the system can be effectively tuned manually. This also protects for the ability to implement and use a phase lock loop (PLL)
Figure 22. TE012 test data, quality factor of 22000, applied power of 2.6 watts, net average thrust of 55.4 micronewtons

Mode Frequency (MHz)
Quality Factor, Q
Input Power (W)
Peak Thrust (μN)
Mean Thrust (μN)
Number of Test Runs
TM211 1932.6 7320 16.9 116.0 91.2 5
TM211 1936.7 18,100 16.7 54.1 50.1 2
TE012 1880.4 22,000 2.6 55.4 55.4 1
Table 2. Tapered Cavity Testing: Summary of Results
Downloaded by Philip Panicker on August 2, 2014 | http://arc.aiaa.org | DOI: 10.2514/6.2014-4029

American Institute of Aeronautics and Astronautics 19
automated frequency control circuit. Due to the slow process commensurate with manual tuning, our future test articles will make use of a PLL whenever practical in order to increase the amount of data that can be collected for a given test article configuration and operating condition during a given amount of test time.

More tests needed, of course, especially tests in space.

I have been keeping tabs on this topic since my original post. Very little new turned up in any of the forums or other sites I was visiting until I came across this thread:

http://forum.nasaspaceflight.com/index.php?topic=29276.270

The first eighteen pages mostly recycle the existing arguments presented elsewhere. A few posts down on page 19, though, things get interesting:

Doctor Jose Rodal, a person with serious credentials, enters into the debate, making a good case for the observed effects being the result of thermal variance.

This, in turn, prompts the entry of a person involved with the NASA team that did the actual testing, plus other interested and seemingly credentialed individuals.

This discussion, which cuts very deep into both the methodology of the testing and the theory behind the drive, has been going on for several days now. I find it quite fascinating.

Apologies if linking to another forum violates the rules here.