[Professor Mega-Mind (OP)]

Are Reactionless Drives really , physically possible ?  Argument is put forth here that , contrary to popular belief , they actually , genuinely are .  Though the engineering of Norman Dean proved fruitless , the equivalence principle of Albert Einstein  (E=MC2) made the possibility of producing thrust through uni-directional elimination/conversion of energy a credible concept .  As with airplanes , what once seemed absurd is now most definitely possible .
Pro and con views welcome .
P.M.

*Main.Idea proposed in Reply.91 page # 5 .
**Clarification Reply # 325 , pg. 17 .
》Note-For additional discussion of this subject , go to NSF thread : Discussion on Reactionless Drive (extracted) .
www.thenakedscientists.com/forum/index.php?topic=75493.new;topicseen#new 
**Addendum - The gist of this preposition is laid out in Reply#118,p.6 onwards. The simple interpretation is : If an ~880 ton gun floating in space fires 1/50th of a grain of  sand at 290k.km.per.second , how fast is the gun accelerated in the opposite direction ? The answer is ~100mph , through simple recoil. This automatically means that an 880.ton reciever , gently catching that same 1/50.sand-grain, will be also be accelerated to 100mph . IF the mini.grain can be accelerated WITHOUT recoil , then the basis for an imbalance of thrust (an R.D.) exists . The Compton-Effect could provide that recoilless acceleration .
》Ref.2 : N.S.F. Thread - What is the best Spaceship design ?
www.thenakedscientists.com/forum/index.php?topic=74813.new;topicseen#new 
》》Ref.3 : Is it possible to have a space drive using reflecting light?
www.thenakedscientists.com/forum/index.php?topic=79795.
》》Ref.4 : quora.com/Is-a-reactionless-drive-possible/answer/Derek-Hendricks-7?ch

[wolfekeeper]

Nope. They violate both conservation of energy and conservation of momentum. If you could build them, then you have created a potentially infinite power source.

[Professor Mega-Mind (OP)]

..............Drifting in space .
Let me postulate a possible exception , the man in a box (drifting in space) .
Picture , if you will , a large steel box , floating in space .  In the middle stands an astronaut .  In his right hand he holds a 20lb sandbag , in his left a 20lb steel ball .  When his timer dings , he throws both objects at the opposing walls .  The sandbag hits the right wall , goes "splat" , deposits %55 of it's kinetic energy into the wall , %45 into friction heat , then slowly drifts back to the 'stronut .  The steel ball bounces off the left wall , deposit-ing %2 of it's kinetic energy into the wall , and reversing it's flight with %98 of it's initial kinetic energy intact .  It then strikes a sandbag mounted on the right wall , depositing %55 of that %98 KE into the right wall .  It then drifts back to the "stronut" . Of all the energy he mustered for his simultaneous throws , only %1 went into pushing the left wall , ~%55 went into pushing the right wall , the rest became omni-directional waste heat .  The result is that the box slowly drifts to the right , without ejecting any reaction mass .  Repeating the process would result in a small rate of acceleration .  This would definitely qualify as a reactionless drive .
A repetitive motion system , losing some of it's kinetic energy uni-directionally , experiences an effective "push" from the remaining  kinetic energy .  Energy conversion is the key .  E=MC2 is proven out .  Long live the "Epstein Drive" !
P.M.

[Bored chemist]

Have you considered  doing some study, rather than posting stuff that doesn't work?
Let's start by considering the steel ball.
You throw it at the wall and it bounces off.
Let's make the arithmetic easy.
The ball has a mass of 1Kg and you throw it at 1 m/s
And let's assume that the rest of the apparatus has a total mass (including you) of 100 Kg.

And, you specified that it  keeps 98% of its  energy.
To a good approximation, if it loses 2% of its kinetic energy then it loses 1% of its velocity.

Also, let's start with the whole rig not moving (from our PoV)

You throw the ball.
The laws of physics say that momentum is conserved. The ball goes one way, you go the other. (You may remember that you didn't understand why I suggested you thought about standing on a skateboard and throwing a heavy bag)

(For the minute, I'm ignoring the fact that you throw a sandbag the other way. I will come back to that.)
The next thing we need to consider is whether or not your feet slip. (again, I will come back to this)
For the sake of making things easy, we can assume that you are wearing magnetic boots or something, so you are stuck to the "floor" of the box.

So, when you throw the ball it goes one way, and you go the other (and you drag the box with you).
We can calculate how fast you + the box move from the conservation of momentum.
The system starts from zero velocity and thus a total of zero momentum
The ball gets +1  Kgm/s of momentum. So the box + you must get a momentum of -1Kgm/s so that the sum is still zero.
And, if you and the box weigh 100 Kg then your velocity must be 1/100 m/s.

You are now drifting slowly to one side and the ball is moving to the other.

This continues until the ball hits the wall of the box.
It rebounds.
It had a momentum of 1 kgm/s and it finished going the other way at 99% of the  original speed.so it now has -0.99 Kgm/s
So the change in momentum is 1.99 Kgm/s
And, again, momentum is conserved so, if the ball's momentum changes by 1.99 Kgm/s  then the box must also change by the same amount (but in the opposite direction.)
So the 100 Kg box must have a change of velocity of 1.99/100 Kgm/s
Previously, it was drifting at 1/100 m/s
It's now drifting in the opposite direction at (1.99-1)/100 m/s i.e. 0.99/100 m/s

Imagine you decide to catch the ball.
It currently with a momentum of -0.99 kgm/s and it ends (from your PoV) with a momentum of zero.

So it must transfer -0.99 Kgm/s of momentum to you + the box. And that's exactly the same momentum that you + the box had- but in the opposite direction
So. after that the box+ you + the ball have zero momentum.
You end up not moving

The same would be true if the velocity change was some other fraction, rather than 99%
So, for example, your sandbag wastes 45% of the energy as heat.
So it keeps 55% as KE.
So the velocity must fall to about 74% of the original velocity.
So, you can repeat exactly the same calculation as I did before but replace every instance of .99 with .74
And, in the end you will get the same outcome; when you catch the bag after it bounces, all the momentum changes cancel out and the overall effect is zero.

So it doesn't matter if you throw the two things in opposite directions at the same time- neither of them "knows" about the other, so they can't change their behaviour because of the other throw.
The only difference it makes is we no longer need to fix your feet to the floor.

You don't seem to understand that momentum is conserved, even when energy is lost as heat.

[Professor Mega-Mind (OP)]

Your entire Oedapis Rex up there is badly flawed .  It's missing the counter-throw designed to obviate that very problem .  Use the complete architecture , and the stro-nut stays put .  Everything then works as I claimed .
P.M.

[Bored chemist]

Your entire Oedapis Rex up there is badly flawed .  It's missing the counter-throw designed to obviate that very problem .  Use the complete architecture , and the stro-nut stays put .  Everything then works as I claimed .
P.M.

No, it doesn't, but if you want to show that I'm wrong....
Show your working.

[Professor Mega-Mind (OP)]

Personally , I've got a room in my head .  If you need to see these things physically , google up free-piston or opposed-cylinder engines , and study the forces they produce .
......P.M.

[Bored chemist]

Show your working.

[Professor Mega-Mind (OP)]

................Gloating Time !
Wikipedia once again !
Look up "Opposed Cylinder Engine"
or Kontra Engine by Karl Benz .
Specifically designed to cancel out opposing forces within the engine .  This is why it is the preferred engine for general aviation .  Can't have our airplanes getting pushed sideways , now can we ?
P.M.

[Bored chemist]

Show YOUR working.

[Professor Mega-Mind (OP)]

I'm letting Karl Benz speak for me right now , since my engine would fundamentally be along the lines of his .
P.

[Kryptid]

I'm letting Karl Benz speak for me right now , since my engine would fundamentally be along the lines of his .
P.

His engine doesn't violate conservation of momentum, so if he's "speaking" for you, it's to say that your idea doesn't work.

[Bored chemist]

since my engine would fundamentally be along the lines of his .

No, it is not.

Please show YOUR working

[Professor Mega-Mind (OP)]

Just refer to "Reactionless Drives Possible ?" dated today at 2000hr .
P.

[Professor Mega-Mind (OP)]

Excuza !
Go to "Best Spaceship Design" , dated 11/9/18 at 2000 hrs .
P.M.

[Professor Mega-Mind (OP)]

......Perfectly Inelastic Collision.
www.tutorvista.com/physics/basic-laws-of-physics
 Here is a top-notch breakdown of the physics processes involved .  It makes clear how the opposing impacts can be radically different in kinetic energy transfer (impact) .
Unequal impacts = push/thrust .
P.M.

[Bored chemist]

Excuza !
Go to "Best Spaceship Design" , dated 11/9/18 at 2000 hrs .
P.M.

Why?
What would be the point ain looking at your nonsense there?

......Perfectly Inelastic Collision.
www.tutorvista.com/physics/basic-laws-of-physics
 Here is a top-notch breakdown of the physics processes involved .  It makes clear how the opposing impacts can be radically different in kinetic energy transfer (impact) .
Unequal impacts = push/thrust .
P.M.

You seem not to grasp the fact that you are arguing with a bunch of people who could have written a better web page than that.

We know this stuff.
That's why we know you are talking nonsense.

[Professor Mega-Mind (OP)]

I haven't seen anything impressive yet , just undo criticism of an impressive idea !  It's a simple matter of kinetic energy transfer , which I already broke down .  I have NOT seen any numerical rebuttal yet ! 
Impress me and I'll eat my hat !
P.M.

[Kryptid]

I have NOT seen any numerical rebuttal yet ! 

You are shifting the burden of proof.

It's not up to your detractors to prove you wrong, it's up to you to prove yourself right. This is why we continually ask you to show momentum calculations.

......Perfectly Inelastic Collision.
www.tutorvista.com/physics/basic-laws-of-physics
 Here is a top-notch breakdown of the physics processes involved .  It makes clear how the opposing impacts can be radically different in kinetic energy transfer (impact) .
Unequal impacts = push/thrust .
P.M.

Ironic that your posted website has the following statement written on it as a law of physics:

3) Newton's third law of motion
Newton's third law tells that, every action there is an equal and opposite reaction.

[Bored chemist]

I haven't seen anything impressive yet

Yes you have.
I provided one.
You didn't understand it, but that's hardly my fault.