[Bored chemist]

.8 Gigajoules in one second is an enormous amount of kinetic energy

Yes.
But a laser beam does not have much kinetic energy. Essentially all of the energy is potential energy tied up in stretching electromagnetic fields.
Only the tiny fraction associated with the tiny mass of the photons is, in any way, kinetic energy.
That's why the "shove" from light is so small.

Why can't you accept this simple fact?

The trick is finding a good catch mechanism .

Any "catch" will have a recoil.
So there will be no reactionless force.

[Professor Mega-Mind (OP)]

The internal , oscillating fields of the photon transmute their energy into kinetic energy of moving matter (the electrons ) .  This second form is what has the potential for significant impact , instead of reflection .
P.M.

[Bored chemist]

If you had a photon traveling across the room from left to right, what is the one direction in which the electric field associated with that electron can be guaranteed not to push an electron?

[Kryptid]

.8 Gigajoules in one second is an enormous amount of kinetic energy .

I never said it wasn't.

It is a helluva shove , no matter WHAT does it !

You're speaking from your intuition again without any actual hard evidence to support it. If the mass involved is small or if the time period over which it acts is long then the forces involved will be weaker than if the mass is large or the time period is short.

If you're so interested in impact force, then you really should commit yourself to understanding that impact force is (2 multiplied by mass multiplied by velocity) divided by impact time. That is a simple algebraic equation that any high school student should be capable of understanding. Unless you have dyscalculia or some similar disorder, there is no excuse for your inability to grasp it. Since there are three variables in the equation, here are your three options for increasing impact force:

Increasing the mass of electrons: If the other variables are kept constant, increasing the total mass of electrons will give you more impact force. Since your device is limited to one electron per photon, then increasing the mass of electrons must ultimately involve increasing the number of photons you get. This will require either increasing the laser power or decreasing the energy of each photon. However, decreasing the energy of each photon will also decrease the velocity of the electrons, which will ultimately cancel out any intended benefits. Therefore, the only option is to increase laser power.

Increasing the velocity of the electrons: This is dependent on the Compton scattering equation and is directly related to the energy of each photon. The only way to make this increase is to increase the energy of each photon. If the power of the laser is kept constant, then increasing the energy of each photon must be compensated by having fewer photons per second. This will cancel out any intended benefits of having higher energy photons. Like the previous step, this means that the only option to increase the force is to increase laser power.

Decreasing the time of impact: You can decrease the time period over which a given mass of electrons impacts your plate either by decreasing photon energy or by increasing laser power. Both of these options will give you more photons per unit time to use and therefore allow you to accelerate more electrons per unit time. Decreasing the photon energy, unfortunately, will decrease the velocity of the electrons and ultimately result in no greater force than you started with. The only other option is to increase laser power.

So no matter which of these three variables you change, the only way to get more force is to get a more powerful laser.

EDIT: To add on to what I said earlier, it might be interesting to show what happens when you keep the kinetic energy of an object and its impact time the same while changing the mass. Here are some examples of the velocities and impact forces that you get for objects with a kinetic energy of 1 gigajoule and an impact time of 1 second:

Boeing 747 - 334,400 kilograms - 77.336 meters per second - 51,722,316.8 newtons of impact force
African Bush Elephant - 28,600 kilograms - 264.443 meters per second - 15,126,139.6 newtons of impact force
Bowling Ball - 7.26 kilograms - 16,597.65 meters per second - 120,498.939 newtons of impact force
Ping-Pong Ball - 0.0027 kilograms - 860,663 meters per second - 2,323.7901 newtons of impact force

Is it yet clear that less mass equates to a weaker impact for the same amount of energy?

[Bored chemist]

Is it yet clear that less mass equates to a weaker impact for the same amount of energy?

Light things hit less hard.
That's something I wouldn't expect to have to explain twice to a bright ten-year-old.

Can anyone explain why the OP is still struggling to accept it?

[Professor Mega-Mind (OP)]

............Screwy logic above .
The above reasoning is a montage of false ass.umptions .
First , the impact breakdown earlier  in the thread was accurate .  An inefficient conversion of .8 GW to thrust will equal ~ .8 Mlbs .  That is roughly equivalent to four 747-200 jumbo-jets at Max.Take.Off.Thrust. This is what a good catcher device will experience , as the reciever for the "Compton Engine" . 
You assume that I'm speaking from intuition .  Negative , my figures come from credible charts , graphs , and listings .  My example is crystal-clear , therefore I don't need to change my numerical , or duration , inputs . You admit above that .8 GJ is a massive amount of kinetic energy .  So once again I must query "Where did that energy go ?  What is that breakdown ?" .  The simple , non-numerical answer is "Into the target." .  Not "Reflected uselessly off the target." , as EMR would do , but actually impacted , and pushed , the target hard .
Don't insult my mathematical processes anymore .  They're giving me credible , believable answers , while your "spaghetti on quick-sand" approach is taking you way off target .  I only bother with such tripe for the sake of readers , who might believe you , and become likewise confused .
Toodles , Mr. 2+2=22 !
P.M.

[Bored chemist]

An inefficient conversion of .8 GW to thrust will equal ~ .8 Mlbs . 

This is not true.
Saying more often does not change that.

My example is crystal-clear

Your "example" is wrong.

Don't insult my mathematical processes anymore .

You keep doing the wrong maths.

You admit above that .8 GJ is a massive amount of kinetic energy .

Yes- but it is not the kinetic energy you get from a 0.8GW laser in a second.

So once again I must query "Where did that energy go ? 

Are you asking again because you didn't like the answer you got last time?
It isn't going to change.

Don't insult my mathematical processes anymore .  They're giving me credible , believable answers

Nobody but you thinks they are credible, or believable.

You assume that I'm speaking from intuition .  Negative , my figures come from credible charts , graphs , and listings

Yes, then you take the right numbers and do the wrong things with them
That's why you get the wrong answers.

[Kryptid]

I must now consign Professor Mega-Mind to being beyond hope. To the ignore list he goes.

[Professor Mega-Mind (OP)]

.......Misrepresentations above
First , KE=M×Vsq. does say it all .  Just as it takes disproportionate push to raise speed as speed increases , so disproportionate push is received from decelerating faster objects , as well .  This is why decelerating 40 micrograms of electrons from .8 c , in one second , will yield as much "push" for that second , as four 747s at full thrust , for exactly one second. 
Stick with thrust , your impact #s are scrambled eggs .
FYI , earlier jumbo engines were officially rated at ~50k.kw of power , and ~50klb of thrust .
Also , a laser-beam has intrinsic heat energy , but negligible kinetic energy .  This is why it can melt through steel , but not push it any .  Electrons have no intrinsic heat energy (internal oscillations ) , they have kinetic energy resulting from velocity .  THAT is how they transmit heat .  That is also why physics terms slowly moving free-electrons as "cold" , and fast-moving free-electrons as "hot" .
Lastly , any real space scientist will verify that tiny , fast moving objects hit just as hard as large , slow moving ones .
Pull fingers from ears !
P.M.
P.S.-A full 747 cruises w/~10 GJ of kinetic energy .

[Professor Mega-Mind (OP)]

................Addendum .
 50,000 kw ( 50K kw. ) .
Got worked up , wrote too fast !
P.M.

[Bored chemist]

First , KE=M×Vsq. does say it all

No
If you want to look at forces (and, for a drive, you do) then you have to consider momentum.

OK, let's see where you start to go wrong.
Which  part of this do you not accept. (I will number the bits for you)
(1) Newton's laws tell us that force = mass times acceleration.
(2) Acceleration is the change of velocity divided by the time it takes
(3) If you start or end with zero velocity then that "change of" bit is irrelevant
(4) So force = mass times velocity divided by time.
(5) And, mass times velocity is momentum
(6) So force = momentum / time
(7) [ strictly, force is (change in momentum)/time,  but I got tired of writing "change of"]

And, if you look, you will see that the equation does not even include energy as a term.
Energy isn't want you want, if you want to calculate forces.

So, go on, tell me which step do you think is wrong, and tell me what mistake I have made in going from each equation to the next?

[Professor Mega-Mind (OP)]

Isaac Newton's "laws" were written for matter , not IMITATION matter .  Matter is always extant somewhere , if it interacts within a system .  Light , on the other hand , is created out of thin air . It is used in impossible ways , then chucked out as nothing , without affecting the system .
By the way , you have not yet
accounted for the radial momentum of the light's internal oscillations .
Lastly , I believe that force equals mass times deceleration , also .
P.M.

[Bored chemist]

Matter is always extant somewhere

No
Creation and annihilation of matter/ antimatter pairs is well documented.
In particular, "pair formation" from high energy x rays (which you were talking about earlier) is well known.
You might want to call light "imitation" matter, but it carries momentum. You need to account for that.

It is used in impossible ways

That would be... impossible.
So it's wrong.

By the way , you have not yet
accounted for the radial momentum of the light's internal oscillations .

Actually, I did. I asked you about it.
You didn't answer.
Here's the question again.

If you had a photon traveling across the room from left to right, what is the one direction in which the electric field associated with that electron can be guaranteed not to push an electron?

Perhaps you could actually answer it this time.

Lastly , I believe that force equals mass times deceleration , also .

Give or take a minus sign, yes.
So what?
Anyway, perhaps you could address the point I made and let me know where in that sequence of  7 steps you part company with reality?

[Kryptid]

If you want to look at forces (and, for a drive, you do) then you have to consider momentum.

And he couldn't even get the kinetic energy equation right.

[Bored chemist]

I consider that a naked demonstration of the quality of your thought processes .  Most embarrassing even to be associated with , and likely the reason why heavy-thinkers like myself are avoiding these threads . 

Just a thought.
If you really believe that, set up a poll about it and see.

[Professor Mega-Mind (OP)]

..............Mr. Bull Nitpicky .
ENGINE , not high energy collider !
1 MeV X-ray stream hitting static electrons ain't doing that !
 Next ; does matter just shrivel up and/or dissappear ?  Furk No !  If it did that would screw up your math , now wouldn't it ?
Next , impossible for matter is not impossible for light .
Next , your billiard-ball question is NOT what I was referring to .  I clearly meant a number value for the side-to-side , internal oscillations composing the photon . 
Finally , I don't feel like answering the E.S. level insult .  That is NOT why do this forum !
P.M. 

[Bored chemist]

Next ; does matter just shrivel up and/or dissappear ?  Furk No !  If it did that would screw up your math , now wouldn't it ?

No, the most common form of disappearance is conversion to two photons.
Momentum is conserved.
So is energy- once you take the relativistic equivalence into account.
So, reality doesn't do what you suggest and, consequently, doesn't screw up my maths.

your billiard-ball question is NOT what I was referring to .  I clearly meant a number value for the side-to-side , internal oscillations composing the photon . 

I asked about photons hitting electrons.
That's not a "billiard ball" problem.
It seem you realised this when you say stuff like

impossible for matter is not impossible for light .

but then forgot it again.
Also, the relevant answer to your question would be about what part of the electromagnetic field can push an electron forward. You don't seem to want to think about that , so I will answer it for you.
It is, of course, zero, because the field is at right angles to the direction of motion.
I could go + find a numerical value for the electric field  (so could you if you were less lazy) , but it's in the wrong direction to help your magic machine.

Finally , I don't feel like answering the E.S. level insult .  That is NOT why do this forum !

The point of being on any forum is to discuss things.
That means answering legitimate questions.

[Professor Mega-Mind (OP)]

The question was posed to get you to admit that photons are made of high energy electric/magnetic waves , oscillating within .  You imply that the side-to-side motion can't knock an electron forward , but I say "incorrect" .  The internal waves hit the electrons in a manner similar to a billiard-ball hitting another billiard-ball in a glancing contact .  This can propel the stricken ball sideways , relative to the direction of the striking ball .  Ergo , the photon's internal oscillations knock the electrons forward with great force .
The weak impact forces of photons striking massive objects are because the internal em waves are not engaged .  They are a seperate dynamic , different from ordinary object-striking-object , k.e. and momentum conventions .
Now that you see the trick , stop insulting the MAN who discovered it !
P.M.

[Bored chemist]

but I say "incorrect" .

You say a lot of things...

Now that you see the trick

Nobody has seen anything except you posting gibberish.

[Professor Mega-Mind (OP)]

...........Shock-Wave Engine .
This is an actual , practical , form of the Compton Effect-type of engines . 
Mount a dense-plasma container (X-ray transparent) on a bulkhead , with some padding between it and the container .  Install massively powerful HEX-ray projectors opposite the .container . Fire ultra-powerful , extremely short bursts of unfocused HEX-rays at the tank of plasma . These should generate strong shockwaves , which hit the pad & wall as hammer blows .  A continuous series of these will steadily push on the wall , in a manner similar to a buzz-bomb (pulse-jet) engine .  The Compton-Effect assures that although recoil will be negligible , the shockwaves will be relatively powerful .
THAT is the first practical  Reactionless Drive !
Professor Mega-Mind .