Electromagnetic Propulsion

[siarad]

Ion engines have already been proved but the topic is dealing with propulsion without external transfer of energy therefore allowing continuous motion for nothing.<br />This is why it's been ridiculed but as I've said light seems to do this.

 

[siarad]

So light coming from the sun gains energy form earth causing it to 'go blue' so the sun isn't yellow but red then.

 

[nacnud]

Eh?

 

[drwayne]

"I agree that the energy in form of elmag waves (like radiation and light) can escape the vessel. But heat, as vibrating molecules, can not if space is completely empty at the site. "<br /><br />Look up greybody radiation. It is a means by which a body at a certain temperature turns that thermal energy into photons.<br /><br />"The question then is, since there is a relation between mass and energy, would letting out energy at the back, in stead of mass, make the vessel move forwards?"<br /><br />Yes, as another poster pointed out, you could move a ship with a flashlight. Slowly, but it will accelerate.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vidar]

Pardon me, but the reason its been ridicule seems to be very different.<br />The reasoning is like ‘the car engine won’t work – there is a banana in the exhaust system.<br /><br />The reason seems rather to be like the NIH of Monte Python And The Holy Grail (NIH: Not Invented Here).

 

[mrmorris]

<font color="yellow">"The reason seems rather to be like the NIH..."</font><br /><br />Actually the reason is because of NPPITU (NPPITU: Not Physically Possible In This Universe). This is evident to anyone with a reasonable understanding of physical laws.

 

[vidar]

The idea is not silly at all. It is incomplete in detailed description, though.<br /><br />The hammer/piston should thereby generate photons in backwards direction, when generating motion in forward direction. It is possible to make photons out of impacts. Although the photons represent ‘waste energy’, it could be controlled as beacon and/or carrier-wave for data transmission. Still the system is sealed with a transparent backside.<br /><br />Anyway, some principle should be tested in real environment, i.e. space.<br />That would of cause be different miniature model with electric batteries as energy source.

 

[drwayne]

Actually, I don't think I have ridiculed you. I have pointed out some things that you assuming that I know from analysis to be incorrect, but I have tried to do it in a fashion that was not mean.<br /><br />You need to avoid attaching motives to people who are telling you your analysis is incorrect. Physics is not a debate in which the best worded argument (or best looking person on TV) wins. It is about analysis. Understanding the underlying physical principles and applying them to the analysis and solution of problems is what physics is about. <br /><br />This is not a skill that develops overnight, or as the result of reading a few books. It comes from doing a *lot* of work, a lot of problems, a lot of paper and pencils and late nights. It comes from doing a lot of experiments. It comes from teaching introductory physics labs that feature experiments with air tracks and tables which demonstrate things like conservation of momentum. (Or a fascinating lab in which we fired a .22 bullet into a ballistic pendulum)<br /><br />Even then: <br /><br />There were many principles of physics that I did not really *get* until I was preparing for the Ph.D. orals I mentioned in an earlier post, years after I first "learned" them.<br /><br />I can tell you all of that, but I can not make you believe / understand it. You may well believe that it is all some elitist argument designed to put you in your place. You can believe that I am really some dumb old guy who is hiding behind degrees. Heck, maybe I am lying about the degrees. Or maybe think I am some book smart egg-head who doesn't live in the real world. (My wife might even agree with elements of the last one).<br /><br />Or you can understand the context that I am giving you.<br /><br />Its up to you.<br /><br />Wayne<br /><br /> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vidar]

No hard feelings doctor.<br /><br />I have responded at this site equally rude, when called for.<br /><br />Most participants have realised that this is a constructive debate.

 

[somispin]

Maybe if by constrive debate, you mean helpless, endless spiraling disarray, than sure, this thread is priceless.<br /><br />The discussion on the princess and the weight was in effect much much more interesting.<br /><br />Your theory of electromagnetic propulsion has ben debunked beyond debunkage.

 

[vidar]

There is a third possibility of electromagnetic propulsion.<br />As some (tomnackid, starfhury, nacnud and drwayne) have pointed out, the use of laser photons, as propulsion, can work.<br /><br />With a NTG (Nuclear Thermal Generator) and a laser gun inside the ship, it can be an alternative for chemical and nuclear propulsion.<br /><br />Early TNG that weighted 20 Kg provided 500W for decades. Hopefully the effect is doubled now. <br /><br />What speed can the laser and NTG make a 200 Kg vessel gain? <br />

 

[rpmath]

<font color="yellow">Early TNG that weighted 20 Kg provided 500W for decades. Hopefully the effect is doubled now. <br /><br />What speed can the laser and NTG make a 200 Kg vessel gain? <br /></font><br />The problem with laser is that the exhaust moves at light speed, and its momentum is P = E /c<br /><br />If your laser works for decades, lets say 50 years, the energy provided will be:<br />500W * 50 y * 365.25 d/y*24 h/d * 3600 s/h = 7.9 * 10¹¹ J<br />divide that per c = 3 *10⁸ m /s and you get P = 2.6 * 10³ Kg m/s<br />divide per 200 Kg and you get 13m/s<br /><br />In 50 years that ship will only get a little faster than a 100m runner does in secconds <img src="/images/icons/frown.gif" /> .

 

[vidar]

13 m/s is too slow, back to the drawing board.<br /><br />The problem is the speed of light in laser exhaust. <br />There have been some light-slowing experiments, that has reduced the speed of a light to 17 m/s. http://en.wikipedia.org/wiki/Speed_of_light <br /><br />Would it be a solution to reduce the speed of the laser light down to 300 m/s and use 2 KW generators, or would that just be tricking a mathematical formula?<br />

 

[larper]

As soon as the light leaves your rocket, it is doing c. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[rpmath]

<font color="yellow">13 m/s is too slow, back to the drawing board. <br /><br />The problem is the speed of light in laser exhaust. <br />There have been some light-slowing experiments, that has reduced the speed of a light to 17 m/s. http://en.wikipedia.org/wiki/Speed_of_light <br /></font><br />The solution is to use the laser to heat something... and use it as exhaust<br />For things moving at a speed v much slower than c, from the equations of:<br />energy <font color="#00FFFF">E = m v² / 2</font> and momentum <font color="#00FFFF">P = m v</font> you can relate P and E by:<br /><font color="#00FFFF">P = 2 E / v</font> and E = P²/ 2 m => <font color="#00FFFF">P = square_root(2 m E)</font><br />The most exhaust mass you heat (to make its molecules move faster) with the same amount of energy the most momentum you get. <br />The problem is that if you need to carry too much mass, your ship will not gain much speed because v = P / m and this m includes the mass you will eject during your trip. And you will end with a compromise value.<br /><br />I remember some experiments with “light ships”. The idea is to point a high energy laser to a small mirror ship. The mirror has some sort of parabolic curvature to concentrate the laser in a small ring around the ship, where the air is heated to thrust the ship. <br /><br /><font color="yellow">Would it be a solution to reduce the speed of the laser light down to 300 m/s and use 2 KW generators, or would that just be tricking a mathematical formula? <br /></font><br />What some physicists call “reducing light speed” is generally making it being absorbed and re-emitted among dense matter. The speed of light in vacuum isn't really reduced, it's something like moving in a longer way... well... if you are moving light among a very very very dense material (like a Einstein-Bose condensate), you can have some sort of gravit

 

[vidar]

So, the problem with electromagnetic propulsion in space, is not to make the forward force, but to make the backwards contra-force, according to the laws of momentum.<br /><br />Hypothetically, let’s say we manage to make elmag force at 1 G. Is it possible to make accordingly much exhaust momentum with radiation, light and heat? For example, the forward propulsion is an electromagnet pushing an magnet at the back of the hull. That electronic magnet also produces photons from LEDs or neon-ligh for backwards exhaust, representing just as much force. <br /><br />Now, what is wrong this time?<br />

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>Now, what is wrong this time? <p><hr /></p></p></blockquote><br /><br />This....<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>the forward propulsion is an electromagnet pushing an magnet at the back of the hull. <p><hr /></p></p></blockquote><br /><br /><br />So, all you have is the photons coming out the end, and they don't represent "Just as much force". <br /><br />Eliminate the electromagnet and you have the exact same system: A photon drive producing extremely low amounts of force. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[vidar]

This time you should rather try to answer the main question: <br />'Is it possible to make accordingly much exhaust momentum with radiation, light and heat?'

 

[larper]

If you throw enough photons out the back, you will produce 1G thrust. We don't have the technology to actually do this, however. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[mrmorris]

<font color="yellow">"If you throw enough photons out the back, you will produce 1G thrust. "</font><br /><br />True... but just saying we "don't have the technology..." doesn't quite cut it in exhibiting the just exactly what difficulties are involved. It's equivalent to telling your five-year-old that's digging a hole in the backyard with a teaspoon that if he digs the hole deep enough, he'll make it to China. Potentially true in the absolute broadest of senses, if you ignore a <b>vast</b> array of problems (including the fact that all else ignored, the kid would be fiftyish by the time the tunnel was complete... assuming no meal, sleep, or potty breaks). <img src="/images/icons/smile.gif" /><br /><br />In terms of photons creating 1G of acceleration, consider a solar sail. The hope for these is that a ship with a square mile or so of sail <b>might</b> achieve accelerations of a hundredth of a G or so (probably less, I'm making a WAG). This despite the fact that a square mile of sail collects a *huge* number of photons, and the sailcraft will be extremely light. The energy densities required to power a craft that will produce its own photons in the quantities required to accelerate its mass at 1G are staggering. You're looking at antimatter-levels here.

 

[larper]

I know the scale of the problem. I was just hoping to make it clear to vidar that, for once in this thread, it is not a physical impossibility, just an engineering problem. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[mrmorris]

<font color="yellow">"I was just hoping to make it clear to vidar ..."</font><br /><br />So was I. However, telling him that it's <b>possible</b>, without then going on to show just how incredibly, immensely, mind-bogglingly <b>improbable</b> is just begging for this thread to continue on in the same check-your-common-sense-at-the-door fashion that has been primarily the case.

 

[vidar]

I am very sorry to say this, but your opinions are like echoes of, you cant bike – you wont keep the balance, it cant drive – it will explode, it cant sail – its made of iron, it cant fly – its to heavy, I cant imagine further – it will blow my mind.

 

[mrmorris]

<font color="yellow">"I am very sorry to say this, but your opinions are like..."</font><br /><br />Ouch, that'd sting -- if I had any respect whatsoever for your opinions. Guess I'm just naturally lucky.

 

[vidar]

No offence, really. <br />Just mutual response, when called for.<br /><br />I believe we’re going interstellar some day.<br />Chemical rockets, solar sail, or fusion explosives won’t do.<br />Electromagnetism might, even though we haven’t figured out how, yet.<br /><br />This is a discussion about how.<br />I’ll bet some other than me have learned some, and will learn more.<br />