InigoMontoya

In my experience, "stiffness" is shorthand for "resistance to deformation." How does one measure it? With a tape measure, LVDT, or any other means to measure deflection. Granted, you're not measuring "stiffness" as much as you're comparing it.

REDUCED stiffness in turn simply means a structure that is more prone to deflection.

Usually, this means lower moments of inertia for structural members but it can also be a result of material selection (particularly in dynamic applications).

If you want to talk about gaps in our current understanding of physics that could be exploited... Fine. Then do so (although even then I'd argue that an engineering forum is the wrong place). But to talk about the hows of exploiting such a gap when the gap hasn't even been identified? That's the very definition of putting the cart before the horse.

The caps lock key; find it, he would.

Fixed your post.

Please, open your mind !!! and read all I am saying ....by transforming "unknown energy" into a "known energy".....!!!!

 

You know that most (80 %) of the energy existing in Our Universe ... we don´t know were it is ... it is unknow (dark) energy.

 

Possibly this knowledge is too high for you?

And we could have warp drives on our flying cars if only we could find those damned Dilithium Crystals!

The point: If you want to use nothing but your imagination and wave your arms around and talk of mystical energies and state that our understanding of physics is flat out wrong? OK, sure. You could have your free energy machine. But if you want to stick to anything that resembles the laws of physics as we currently know them... Nope. Not gonna happen.

So... If you want to talk free energy devices, might I suggest you drop into a forum that caters to creative writing and not a forum that caters to engineering. 'Cause if you want to base your discussion around known engineering principals, you're not going to get far.

Interesting in theory but what about practice? I could see a few issues....

- How would the floating bridge deal with icebergs or similar hazards in the Bering?

- How easy/difficult would it be to inspect/repair/maintain?

There DO exist free energy machines, since (definitional) free energy is just some device that extracts some energy from some source, without the owner paying a bill. So a windmill or solarpanel IS free energy.

Except that in both cases you either have to own the land (in which case you pay taxes) or pay rent to the land owner. Even if you want to define "free" as an economic term rather than the engineering term usually used around here... Even then there ain't no such thing as a free lunch (or free energy).

You owe me a new keyboard.

I know a person that assure to me he has developed a "free energy" machine,

And people have been making such claims for hundreds of years. So far, not a one of them has been correct. So what makes your friend any different?

Accepted and not doubted, but I think my post makes clear that I realise perpetual motion is not possible but that under the everyday understanding of free we can get energy without ourselves putting energy into a system. Any system using wind power, wave power, water flow or light would come under that everyday definition. My point, such as it is, would be that for example we don't have to burn coal.

Coal's free. You just dig it up out of the ground.

If you're using air muscles for the moving bits and are scrapping the lasers/thrusters (which you would have to).... What's the point of a fuel cell? That provides electrical power; not the pneumatic power you need for your air muscles. Why not just have a CO2 tank and a small battery to power solenoid valves and the like?

LOW POWER lasers have already been successfully tested in missile defense roles. Turns out you don't have to shoot the missile down. You just have to blind it. And IR seekers are pretty sensitive so blinding isn't that difficult. Google for TADIRCM. That was probably 10 years ago. I'm sure they're much better now (although I don't see folks talking about 'em).

Except photon particles can travel a speed from 0 to C. Photon does not have no moving state, and always move only the speed of light, C. @@What is a mass? F=ma. At a light we can not change an acceleration. So mass concept is important.

Except that the "real" equation isn't F = ma. It's really F = d(momentum). For the vast, vast majority of stuff, mass is constant so that simplifies out to F = m * d(velocity) = m*a.

But if you've got momentum (and photons do), then if you change the momentum, you have a force... Even if you don't have mass in the normal sense of the word.

Note too that for objects that have mass that varies (like, say... rockets) if you want to be *accurate* you can't use F=ma. You have to use F = d(momentum).

With a sideways grip, aren't you also defeating the strength of your muscles against the recoil? The straight-up grip is much stronger and more designed with the way the hand and arm muscles work, it seems to me.

Quite possible. I'm not an ergonomics person so I didn't address any such issues. I simply addressed the straight forward discussion of sight design and adjustment (or lack thereof).

Also, with a semi-automatic, aren't you running the risk of hot casings coming back at your face instead of off to your right and behind?

Depends heavily on the gun.

I've seen guns that actually eject the brass *forward*. I've seen others that ejected the cases with seemingly zero velocity (cases seemed to just drop from gun rather than getting thrown). I've seen guns that eject straight back and over the head of the shooter (heck, I own one!). Still others have ejection ports on the bottom of the gun. In other words... It depends on the gun.

Well then why can't you just use the side of the gun barrel to align with your target?

You could. That would be better than nothing.... But only barely.

Suffice to say that holding a gun sideways is a billboard that says, "I'm an idiot!" to anyone who has even a small amount of weapons training.

Is there some kind of engineering reason behind this?

Yes.

In a nutshell: The sites are designed to operate with gravity (which affects bullets too!) aligned with the sites. Holding the gun sideways means that gravity is 90 degrees offset from the direction the sites assume. Voila, the sites aren't adjusted worth a damn.

Yes, water injection works.

On that note...

A few years ago I recall reading about somebody who built a 6-cycle engine that was a hybrid between a normal IC engine and a steam engine (I'll see if I can find a link). It was very cool. Basically it was a normal internal combustion engine for the first 4 cycles. Then, after the normal exhaust stroke water was injected. The next two strokes were a power stroke using water boiled using residual heat from the previous 4 strokes, and a second exhaust stroke. A good indicator of how well the engine was using energy was the fact that it didn't require a cooling system; the 2 steam-related cycles not only generated power but removed enough heat from the system to eliminate the need for additional cooling.

edit to add... a link

Another potential problem: The more O2 you add to the mix, the more likely you are going to be seeing detonations inside the cylinder. Add in meaningful amounts of hydrogen and you're almost guaranteed to be detonating. So even if everything else worked as envisioned (it won't, but we'll say it will for the moment), you're going to have HUGE maintenance problems as your engine will be blowing itself apart over not very much time at all. True, you could built the engine heavier and more robust so that it could handle the detonations, but if you're shooting for lower fuel consumption you're not going to see it simply because everything just got more massive and harder to move.

How could these people use wind and/or water to power furnaces for large-scale metalworking?

Well, they really couldn't.

I was primarily concerned with ore processing and forced air furnaces with the water wheel concept. You wouldn't be able to use that as your source of heat. You'd still need a fuel source. Wood could work, but I gather you're interested in a decidedly barren landscape.

Also, how much "side technologies" are we talking about? What technologies would they most certainly master somewhere along the way?

Virtually everything that doesn't fall under thermodynamics would HAVE to be mastered.

So, isn't there any way to use magnetism in any meaningful way in an otherwise low-tech world to do things which would be otherwise done with steam power or other sources of power?

Nope.

However, if you like the idea of different orders of discovery or technology mastery... Perhaps mastering the propeller before mastering the steam engine? Instead of having a dozen guys rowing you could have a dozen guys cranking on a bronze-age bicycle of sorts hooked to a prop to make the boat go. It's got a couple of things going for it... Legs are stronger than arms. Props are more efficient than oars. Combine those two and you've got a kick arse boat for the day.

Note that one of the problems with your basic premise is that to get all those neato electrical devices one must first master metal working on a large scale. To do that, one needs a source of power beyond mere muscle. Maybe you could skip the steam engine by using water wheels and going straight for electrical power, but you couldn't change the order radically simply because electrical power is reliant upon a large number of previously mastered technologies.

Your job sounds pretty sweet. +1.

I'm pretty partial to it.

Me

...and the facility I run.

If peltier coolers really dumped 100 times more heat than they pumped, who would buy them?

We use 'em at my place of employment.

The application that they generally find themselves in....

- Temporary. IE, the test rig is only going to be in operation for a few days before being torn down.

- Extreme noise/vibration. As in, your ear drums would literally rupture if you were in the room.

- Hot. Ambient temperatures in the region of 100-120 F.

- Lots o' power available. Need 100 amp 480 VAC service? No problem.

And through all that you need to keep some electronics cool. Peltier coolers are cheap and easy to throw into a box. They handle harsh environments. We don't care too much about efficiency. What's not to like?

Depending on what you wish to distil, you may find that copper plumbing fittings and pipe can do the job more easily than glass.

That was my thought as well.

Buy a pressure cooker at a thrift shop. Attach copper tubing to steam outlet. Run copper tubing through a water bath....

I fully confess that I've not had to do such calcs in 20 years and am no longer up on the math required beyond remembering it involves the Lorentz Transform. However, a quick google for "acceleration at relativistic speeds" gives me a wikipedia link to time dilation...

Time dilation at constant acceleration

 

In special relativity, time dilation is most simply described in circumstances where relative velocity is unchanging. Nevertheless, the Lorentz equations allow one to calculate proper time and movement in space for the simple case of a spaceship whose acceleration, relative to some referent object in uniform (i.e. constant velocity) motion, equals g throughout the period of measurement.

Let t be the time in an inertial frame subsequently called the rest frame. Let x be a spatial coordinate, and let the direction of the constant acceleration as well as the spaceship's velocity (relative to the rest frame) be parallel to the x-axis. Assuming the spaceship's position at time t = 0 being x = 0 and the velocity being v0 and defining the following abbreviation

the following formulas hold:[17]

Position:

Velocity:

Proper time:

 

In the case where v(0) = v0 = 0 and τ(0) = τ0 = 0 the integral can be expressed as a logarithmic function or, equivalently, as an inverse hyperbolic function:

A fun little numbers excercise I *can* still do, however.... And mind you, I'm going to neglect relativistic effects here. While I know the real version of what I'm about to say is much, much worse, this should be an interesting exercise....

Suppose you want to get your spaceship to 0.5c on the way to your other planet. You have to accelerate to 0.5c and then decellerate back to 0c (You don't want to just crash land into that other planet at 0.5c do you?) yielding a total deltaV requirement for any rockets of 1.0c. Suppose you have an 20 stage rocket. 10 stages to accelerate. 10 to decellerate. Each stage is responsible for a deltaV of 0.05 = 0.05*3E8 = 15E6 m/s.

The rocket equation tells us the required mass ratio for any stage given engine performance. deltaV = Vext * ln(MR). If we assume that the engine in question is 10X better than the best ion thruster on the drawing board today, we get.... 15E6 = 10 * 5000 * 9.81 * ln(MR). So... 30.6 = ln(MR) Which means that MR = e^30.6 which is approximately 19E12.

Oh my.

What does that mean?

It means that the mass ratio for each stage must be 19E12, of course. What does THAT mean? It means that the rocket's pre-ignition mass must be 19E12 TIMES it's burnout mass. In English?

If you want to push your space ship to 0.05c and your capsule (with you and all your food, etc.) has a mass of 1 kg (you've been on a diet, ok?), then your spaceship's final stage must have a mass of 19E12 kg. But that's just the LAST stage. The stage prior? Well, sticking to the math... 19E12*19E12 = 3.2E24 kg. Great, only 18 more stages to go. Long story short.... 19^8*10^(20*12) = 17E9*10E240... If I remember how all those powers and such work, that implies when your rocket leaves Earth it needs to have a mass of 1.7E249 kg.

For comparison, the Sun has a mass of 2E30 kg.

The only thing you have to do is to accelerate constantly.

With an acceleration of 1m/s2, it will take you about 9,5 years to reach SOL (If I calculated correctly). At g (9,8 m/s2) it will take about one year.

You didn't.

Newtonian physics break down at relativistic speeds.

Okay, I'm officially out of ideas.

 

One of the protagonists in my web series is an alien from a far away world, outside the Solar System. It's set in 2135 in case you forgot, so what's the fastest way for her to possibly get to Earth from her planet?

There is no fast way without resorting to Dilithium Crystals or other story-telling magic wand. Using our current knowledge of physics, anyway you cut it, it would take hundreds if not thousands of years to make such a trip. That leaves you with a few options....

1) The alien was in some sort of suspended animation for the trip.

2) The alien lives a VERY long time.

3) The alien is actually the offspring of those who began the trip and was born somewhere along the way.

4) Some combination of the above.