August 02, 2015

EMdrive paper and what original inventor Roger Shawyer believes is happening

The keys to EMDrive experiments are prove the propulsion is real and will work in space. Find a way with theory or experiment to scale up the effect.

If it is real and the effect can be scaled up then at the very least space travel is transformed.

Here is information from a Shawyer paper, his website FAQ and his videos. Roger Shawyer is the original inventor of the EMdrive.

* Not Reactionless, but propellentless
* Shawyer background was with UK Army research and then in the space industry
* Main players in UK, China and the USA are pursuing EMDrive research
* At least three other countries (that Shawyer knows about) have serious programs running and university departments and private individuals

Chinese Northwestern Polytechnical University

In 2008 a team of Chinese researchers led by Juan Yang, professor of propulsion theory and engineering of aeronautics and astronautics at NWPU, claimed to have developed a valid electro-magnetic theory behind a microwave resonant cavity thruster. A demonstration version of the drive was built and tested under different cavity shapes and at higher power levels in 2010. A maximum thrust of 720 mN was reported at 2,500 W of input power on an aerospace engine test stand usually used to precisely test spacecraft engines like ion drives. As of 2015, this is by far the most significant test of such a device to date - no other group has even announced plans to run tests at similar power levels.

Propulsion forces from NASA Eagleworks and the the German researchers are in the tens of micronewton range.

In an IAC13 paper the dynamic operation of a second generation superconducting EmDrive thruster was described. A mathematical model was developed and, in this paper, that model is used to extend the performance envelope of the technology. Three engine designs are evaluated. One is used as a lift engine for a launch vehicle, another as an orbital engine for the launcher and a third as the main engine for an interstellar probe.

The engines are based on YBCO superconducting cavities, and performance is predicted on the basis of the test data obtained in earlier experimental programmes. The Q values range from 80 million to 200 million and provide high values of specific force over a range of accelerations from 0.4 m/s/s to 6 m/s/s.

The launch vehicle is an “all-electric” single stage to orbit (SSTO) spaceplane, using a 900 MHz, eight cavities, fully gimballed lift engine. A 1.5 GHz fixed orbital engine provides the horizontal velocity component. Both engines use total loss liquid hydrogen cooling. Electrical power is provided by fuel cells, fed with gaseous hydrogen from the cooling system and liquid oxygen. A 2 ton payload, externally mounted, can be flown to Low Earth Orbit in a time of 27 min. The total launch mass is 10 ton, with an airframe styled on the X37B, which allows aerobraking and a glide approach and landing.

The full potential of EmDrive propulsion for deep space missions is illustrated by the performance of the interstellar probe. A multi-cavity, fixed 500 MHz engine is cooled by a closed cycle liquid nitrogen system. The refrigeration is carried out in a two stage reverse Brayton Cycle. Electrical power is provided by a 200 kWe nuclear generator. The 9 ton spacecraft, which includes a 1 ton science payload, will achieve a terminal velocity of 0.67c, (where c is the speed of light), and cover a distance of 4 light years, over the 10 year propulsion period.

The work reported in this paper has resulted in design studies for two Demonstrator spacecrafts. The launcher will demonstrate the long-sought-for, low cost access to space, and also meet the mission requirements of the proposed DARPA XS-1 Spaceplane. The probe will enable the dream of an interstellar mission to be achieved within the next 20 years.

Shawyer has notes from his dynamic tests He claims to have achieved a thrust of 96 milli Newtons was produced for an input microwave power of 334 Watts.

Q. Is the thrust produced by the EmDrive a reactionless force?
A. No, the thrust is the result of the reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it.

Q. How can a net force be produced by a closed waveguide?
A. At the propagation velocities (greater than one tenth the speed of light) the effects of special relativity must be considered. Different reference planes have to be used for the EM wave and the waveguide itself. The thruster is therefore an open system and a net force can be produced.

Q. Why does the net force not get balanced out by the axial component of the sidewall force?
A. The net force is not balanced out by the axial component of the sidewall force because there is a highly non linear relationship between waveguide diameter and group velocity. (e.g. at cut off diameter, the group velocity is zero, the guide wavelength is infinity, but the diameter is clearly not zero.) The design of the cavity is such that the ratio of end wall forces is maximised, whilst the axial component of the sidewall force is reduced to a negligible value.

Q. Does the theory of the EmDrive contravene the accepted laws of physics or electromagnetic theory?
A. The EmDrive does not violate any known law of physics. The basic laws that are applied in the theory of the EmDrive operation are as follows:

Newton’s laws are applied in the derivation of the basic static thrust equation (Equation 11 in the theory paper) and have also been demonstrated to apply to the EmDrive experimentally.

The law of conservation of momentum is the basis of Newtons laws and therefore applies to the EmDrive. It is satisfied both theoretically and experimentally.

The law of conservation of energy is the basis of the dynamic thrust equation which applies to the EmDrive under acceleration,(see Equation 16 in the theory paper).

The principles of electromagnetic theory are used to derive the basic design equations.

Q. Why does the EmDrive not contravene the conservation of momentum when it operates in free space?
A. The EmDrive cannot violate the conservation of momentum. The electromagnetic wave momentum is built up in the resonating cavity, and is transferred to the end walls upon reflection. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. The direction and acceleration that is measured, when the EmDrive is tested on a dynamic test rig, comply with Newtons laws and confirm that the law of conservation of momentum is satisfied.

Q. Is the EmDrive a form of perpetual motion machine?
A. The EmDrive obeys the law of conservation of energy and is therefore not a perpetual motion machine. Energy must be expended to accelerate the EmDrive (see Equation 16 of the theory paper). Once the EmDrive is switched off, Newton’s laws ensure that motion is constant unless it is acted upon by another force.

Q. Why does the thrust decrease as the spacecraft velocity along the thrust vector increases?
A. As the spacecraft accelerates along the thrust vector, energy is lost by the engine and gained as additional kinetic energy by the spacecraft. This energy can be defined as the thrust multiplied by the distance through which the thrust acts. For a given acceleration period, the higher the mean velocity, the longer the distance travelled, hence the higher the energy lost by the engine.
This loss of stored energy from the resonant cavity leads to a reduction in Q and hence a reduction of thrust.


Roger Shawyer is the creator of EmDrive (Electromagnetic Thrust) technology. This interview was conducted in May 2015 by Nick Breeze.



Roger Shawyer invented the Emdrive. NASA is testing the EMdrive and the Cannae drive and getting interesting results Shawyer presented in October, 2014.

EMDrive results have not been conclusively proven yet and there is no proven underlying theory and any scaling has not been determined.

There are interesting results in the 50-900 micronewton ranges. There does seem to be scaling with increased power levels.

Shawyer sees scaling up the superconducting version of EMdrive to 300 Newtons per kilowatt combined with radioisotope thermoelectric generators or small scale nuclear fission systems to achieve 200 kilowatts for a Alpha Centauri ten year flyby probe. A probe that reaches about 60% of lightspeed and covers 4 light years in ten years.

300 newtons per kilowatt would be scaling up the energy to thrust efficiency by 300 times.

NASA Eagleworks now calculate scaling to many Newtons if EMdrive matches Sonny Whites quantum vacuum theories

NASA eagleworks calculate that if high power Magnetron enhancement works they could achieve 2000 newtons of thrust and high levels of newtons per kilowatt.



Sawyer projected interstellar probe





Shawyers's Development of a Demonstrator Engine

Although the experimental thruster had verified the static thrust equation, it became apparent that the concept would not become generally accepted until a viable engine could be demonstrated. Accordingly, a proposal for the design, manufacture and test of a complete demonstrator engine was submitted to DTI. A Research and Development grant was awarded in September 2003 and the work started with a mission analysis phase.

This work enabled the specification of the demonstrator engine to be optimised against the requirements of a typical commsat mission. Unlike the experimental thruster, the engine would be rated for continuous operation and extensive design work was required to increase the specific thrust by raising the design factor and unloaded Q.

The engine was built with a design factor of 0.844 and has a measured Q of 45,000 for an overall diameter of 280 mm. The microwave source is a water cooled magnetron with a variable output power up to a maximum of 1.2 kW.

To obtain the predicted thrust the engine must maintain stable resonance at this high Q value. Major design challenges have included thermal compensation, tuning control and source matching.

The engine was tested in a large static test rig employing a calibrated composite balance to measure thrust in 3 directions, up, down and horizontal. A total of 134 test runs were carried out over the full performance envelope, with a maximum specific thrust of 214mN/kW being measured.









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