originally posted by: rogerstigers
My gut is telling me that there is nothing involved in these drives that violates the laws of physics. The law of momentum is not being broken.
They simply haven't tested the contraption fully or correctly as yet to identify where the loss is coming from to yield the thrust.
there are natural laws of physics that are never violated, so of course those aren't broken, ever, as far as we know.
However the human "guesses" at these natural laws may need some "tweaking" and the classical concept of conservation of momentum may indeed need some
tweaking in light of quantum mechanics. I don't pretend to know the final outcome but consider these points which lead to my guess:
1. Nobody seems to be questioning the Solar Sail
, which gains thrust from the momentum of
The total force exerted on an 800 by 800 meter solar sail, for example, is about 5 newtons (1.1 lbf) at Earth's distance from Sol, making it a
low-thrust propulsion system,
So, there appears to be nobody questioning any laws of physics about this concept. Photons have momentum.
2. If you put a spherical light bulb in a spherical chamber, the photons emitted will exert this same type of pressure on the inside walls of the
chamber, but since there are far less photons than coming from the sun the pressure will be far less.
3. Cut a hole in this chamber so that photons come out that hole, and why wouldn't you have an imbalance of photon pressure? The photons are pushing
on all the inner surface of the chamber except where you cut the hole, so I see no reason why the photons coming out the hole can't provide some
thrust, and if the classical law of conservation of momentum needs to be updated to reflect this, I wouldn't be surprised as it's a really old law and
we've found exceptions on other old laws (like an exception to the second law of thermodynamics for example).
Now before you get excited and think I'm suggesting the EM drive will be useful, I'm not suggesting that. I'm only suggesting that I won't be at all
surprised if old conservation of momentum concepts are updated to reflect experimental observations.
The bottom line however is that if you do calculations on how much thrust you can get from a photon, it turns out to not be very useful for a drive.
So my guess is that some itsy bitsy teeny tiny thrust will be confirmed, and some concepts may need to be updated to reflect this, but the itsy bitsy
teeny tiny thrust won't be useful.
But you may ask, what about the 1.1 pounds of thrust from a 800 by 800 meter solar sail, couldn't that be useful? Of course, but keep in mind that the
sun is producing power at the rate of 3.846×10^26 W. How much power can a spacecraft be reasonably expected to produce? When you scale down the power
to what can fit on a reasonably sized spacecraft, well guess how many watts you will have available on the spacecraft, and see what kind of thrust you
Some guys attempted to do those calculations here and after some corrections they all seemed to realize that even ignoring the conservation of
momentum law issue, at any conceivable reasonable power level on the spacecraft, the calculated thrust doesn't seem to be useful:
Photon space drive
So I won't be surprised if some thrust is confirmed but I expect it won't be a useful amount of thrust. Tweaking an old human "law" to match
observation and experiment is a non-issue for me.
edit on 18-8-2014 by Arbitrageur because: clarification