in space cant you just keep speeding up ?...

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tomorows_scientist

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<p>ok so the speed of light from my knowledge is basically un reachable by any other object well except for light lol... but in space can you not just keep speeding up ?... u have no friction no air to slow you down ?... so if you somehow were able to compress enough fuel and well oxygen to burn into a container that would keep burning for lets say 2000k years wouldnt you just keep on speeding up the whole time because there is absolutly nothing there in your way to start slowing you down..... so technically if that is true couldnt you hit light speed or even beyond light speed (if you could compress the necisary requirments ALOT OF FUEL lol) by just letting your rockets keep burning..... and the whole time they are burning you are excelerating correct ?....</p><p>&nbsp;</p><p>i had a discussion fairly close to this&nbsp; about 5 months ago but never really got an answer that fit my question.... btw im going to start posting again lol i havnt been on in a long time.....&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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Mee_n_Mac

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>ok so the speed of light from my knowledge is basically un reachable by any other object well except for light lol... but in space can you not just keep speeding up ?... u have no friction no air to slow you down ?... so if you somehow were able to compress enough fuel and well oxygen to burn into a container that would keep burning for lets say 2000k years wouldnt you just keep on speeding up the whole time because there is absolutly nothing there in your way to start slowing you down..... so technically if that is true couldnt you hit light speed or even beyond light speed (if you could compress the necisary requirments ALOT OF FUEL lol) by just letting your rockets keep burning..... and the whole time they are burning you are excelerating correct ?....&nbsp;i had a discussion fairly close to this&nbsp; about 5 months ago but never really got an answer that fit my question.... btw im going to start posting again lol i havnt been on in a long time.....&nbsp; <br />Posted by <strong>tomorows_scientist</strong></DIV><br /><br />You do keep accelerating but at an ever decreasing pace. You keep speeding up but only asymptotically approach the speed of light. You never get there. <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>
 
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weeman

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>ok so the speed of light from my knowledge is basically un reachable by any other object well except for light lol... but in space can you not just keep speeding up ?... u have no friction no air to slow you down ?... so if you somehow were able to compress enough fuel and well oxygen to burn into a container that would keep burning for lets say 2000k years wouldnt you just keep on speeding up the whole time because there is absolutly nothing there in your way to start slowing you down..... so technically if that is true couldnt you hit light speed or even beyond light speed (if you could compress the necisary requirments ALOT OF FUEL lol) by just letting your rockets keep burning..... and the whole time they are burning you are excelerating correct ?....&nbsp;i had a discussion fairly close to this&nbsp; about 5 months ago but never really got an answer that fit my question.... btw im going to start posting again lol i havnt been on in a long time.....&nbsp; <br />Posted by tomorows_scientist</DIV><br /><br />You are right about everything you said. In space there is no friction or&nbsp;atmospheric resistance, and yes, with 2000 years of fuel, you could certainly pick up some serious speed. </p><p>However, there is a catch. The faster you go, the more your mass will increase. Therefore, this would require more and more energy, with an equally increasing amount of fuel to produce that energy. So, if the speed of light is represented by C, and C=1, then I can help you visualize how hoping for lightspeed will be a lost cause. </p><p>At .9 C your mass will be much greater than at .5 C, and at .999 C your mass will have still increases from .9 C. Additionally, at .9999999 C your mass will still continue to increase from that of .999 C. So, what you will begin to notice (from the comfort of your spaceship) is that it will require more and more energy the closer you travel towards the speed of light. So, hypothetically, even if you could harness the power of 1,000 suns, it may get you to .9999999999999 C but you will never actually achieve lightspeed. </p> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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yevaud

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One addition to all of the above:&nbsp; it has been estimated that due to friction with the Interstellar medium, it is doubtful we can ever exceed about 0.3 C.&nbsp; The higher velocities, the more you will have dust and gas impacting your vehicle, and at higher velocities, they hit <strong>hard</strong>!&nbsp; These cause cascades of primary, secondary, and tertiary radiation sleeting through the ship, which is kind of inimical for life. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
 
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weeman

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>One addition to all of the above:&nbsp; it has been estimated that due to friction with the Interstellar medium, it is doubtful we can ever exceed about 0.3 C.&nbsp; The higher velocities, the more you will have dust and gas impacting your vehicle, and at higher velocities, they hit hard!&nbsp; These cause cascades of primary, secondary, and tertiary radiation sleeting through the ship, which is kind of inimical for life. <br /> Posted by yevaud</DIV></p><p>That is indeed true. Of course, if we had the technology to go .3 of C, then perhaps we could have the technology that would be able to withstand such impacts.&nbsp; </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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deapfreeze

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That is indeed true. Of course, if we had the technology to go .3 of C, then perhaps we could have the technology that would be able to withstand such impacts.&nbsp; &nbsp; <br /> Posted by weeman</DIV></p><p>&nbsp;</p><p>We need to get something to deflect space junk. I vote we use politicians.&nbsp;</p> <div class="Discussion_UserSignature"> <p><font size="2" color="#0000ff"><em>William ( deapfreeze ) Hooper</em></font></p><p><font size="1">http://deapfreeze-amateur-astronomy.tk/</font></p><p> </p> </div>
 
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MeteorWayne

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;We need to get something to deflect space junk. I vote we use politicians.&nbsp; <br />Posted by deapfreeze</DIV><br /><br />LOL, talk about space junk.... <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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Mee_n_Mac

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;We need to get something to deflect space junk. I vote we use politicians.&nbsp; <br />Posted by <strong>deapfreeze</strong></DIV><br /><br />As appealing as this idea is I wonder how well it competes on the technical merits.&nbsp; On one hand we have to loft a lot of politicians out of Earth's gravity well and given their general propensity for Kennedyesque proportions ... well that's a lot of rocket fuel.&nbsp; On the other hand we require a very good sheilding material and there's nothing known to be more dense than a politician.&nbsp; Hmmmm ..... <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>
 
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weeman

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;We need to get something to deflect space junk. I vote we use politicians.&nbsp; <br />Posted by deapfreeze</DIV><br /><br />Do you have a template for such a design? I think we have the next Nobel Prize! <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-wink.gif" border="0" alt="Wink" title="Wink" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>ok so the speed of light from my knowledge is basically un reachable by any other object well except for light lol... but in space can you not just keep speeding up ?... u have no friction no air to slow you down ?... so if you somehow were able to compress enough fuel and well oxygen to burn into a container that would keep burning for lets say 2000k years wouldnt you just keep on speeding up the whole time because there is absolutly nothing there in your way to start slowing you down..... so technically if that is true couldnt you hit light speed or even beyond light speed (if you could compress the necisary requirments ALOT OF FUEL lol) by just letting your rockets keep burning..... and the whole time they are burning you are excelerating correct ?....&nbsp;i had a discussion fairly close to this&nbsp; about 5 months ago but never really got an answer that fit my question.... btw im going to start posting again lol i havnt been on in a long time.....&nbsp; <br />Posted by tomorows_scientist</DIV></p><p>While I heartily endorse the use of politicians as shielding or exterios cladding in general, you did start with a serious question.</p><p>Yveaud's comment is valid, and may well provide a lower practical limit to speed in space.&nbsp; However, special relativity provides a more fundamental limitation at the the speed of light.</p><p>Special relativity is based on two and only two assumptions: 1) the laws of physics are the same in all inertial reference frames and 2) the speed of light is the same in all inertial reference frames.&nbsp; Assumption 1) translates to the notion that there are no preferred reference frames, which is consistent with all observations to date.&nbsp; Assumption 2) has been verified in many experiments, notably the Michelson-Morley experiment.&nbsp; Special relativity itself makes other predictions, and those predictions are consistent with a large body of experimental data.</p><p>If one follows the logic in the development of special relativity, from the two fundamental assumptions one derives the Lorentz transformation that relates speeds and time between two inertial reference frames in uniform motion with respect to one another.&nbsp; A logical consequence that comes from the mathematical reasoning involved is that the speed of light is the maximum speed with which anything, including information can move in any measurement frame.&nbsp; This follows from the fact that c, the speed of light, is constant in all inertial reference frames -- and any phenomena that propogates with any constant velocity, X, in all inertial reference frames would do.&nbsp; It just so happens that the speed of light, c, plays this role.&nbsp; From that you can conclude that the only speed that is constant in all reference frames is c, and that nothing can go faster.&nbsp; This has nothing to do with friction or drag.&nbsp; It has to do with the fundamental nature of space and time.</p><p>One of the consequences of special relativity is that, from the perspective of an observer "at rest", (which really means that you simply pick an observer and use that reference frame for subsequent discussion) that an object in motion gains mass, and as the speed of the object approaches c the mass increases without bound.&nbsp; From the equation E=mc^2 with mass tending to infinity, the energy required to approach c also increases without bound.&nbsp; Thus to accelerate a massive body to the speed of light requires infinite energy, and an infinite amount of energy is not available.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
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js117

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>One addition to all of the above:&nbsp; it has been estimated that due to friction with the Interstellar medium, it is doubtful we can ever exceed about 0.3 C.&nbsp; The higher velocities, the more you will have dust and gas impacting your vehicle, and at higher velocities, they hit hard!&nbsp; These cause cascades of primary, secondary, and tertiary radiation sleeting through the ship, which is kind of inimical for life. <br />Posted by yevaud</DIV></p><p style="margin:0in0in10pt" class="MsoNormal"><font face="Calibri" size="3">If and when we ever can exceed 0.3 C.<span>&nbsp; </span>we will probably <span>&nbsp;</span>have a magnetic<span>&nbsp; </span>shield </font></p><p style="margin:0in0in10pt" class="MsoNormal"><font face="Calibri" size="3">out front<span>&nbsp; </span>to deflect <span>&nbsp;</span><span>&nbsp;</span>small objects . This is mentioned in Star Trek Enterprise<span>&nbsp; </span>the first</font></p><p style="margin:0in0in10pt" class="MsoNormal"><font face="Calibri" size="3">episode Broken Bow Part I . </font></p><p>&nbsp;</p>
 
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Philotas

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>While I heartily endorse the use of politicians as shielding or exterios cladding in general, you did start with a serious question.Yveaud's comment is valid, and may well provide a lower practical limit to speed in space.&nbsp; However, special relativity provides a more fundamental limitation at the the speed of light.Special relativity is based on two and only two assumptions: 1) the laws of physics are the same in all inertial reference frames and 2) the speed of light is the same in all inertial reference frames.&nbsp; Assumption 1) translates to the notion that there are no preferred reference frames, which is consistent with all observations to date.&nbsp; Assumption 2) has been verified in many experiments, notably the Michelson-Morley experiment.&nbsp; Special relativity itself makes other predictions, and those predictions are consistent with a large body of experimental data.If one follows the logic in the development of special relativity, from the two fundamental assumptions one derives the Lorentz transformation that relates speeds and time between two inertial reference frames in uniform motion with respect to one another.&nbsp; A logical consequence that comes from the mathematical reasoning involved is that the speed of light is the maximum speed with which anything, including information can move in any measurement frame.&nbsp; This follows from the fact that c, the speed of light, is constant in all inertial reference frames -- and any phenomena that propogates with any constant velocity, X, in all inertial reference frames would do.&nbsp; It just so happens that the speed of light, c, plays this role.&nbsp; From that you can conclude that the only speed that is constant in all reference frames is c, and that nothing can go faster.&nbsp; This has nothing to do with friction or drag.&nbsp; It has to do with the fundamental nature of space and time.One of the consequences of special relativity is that, from the perspective of an observer "at rest", (which really means that you simply pick an observer and use that reference frame for subsequent discussion) that an object in motion gains mass, and as the speed of the object approaches c the mass increases without bound.&nbsp; From the equation E=mc^2 with mass tending to infinity, the energy required to approach c also increases without bound.&nbsp; Thus to accelerate a massive body to the speed of light requires infinite energy, and an infinite amount of energy is not available.&nbsp; <br />Posted by DrRocket</DIV><br /><br />Can we not use the Lorentz factor to explain? With the relativisitc formula for kinetic energy, <img class="tex" src="http://upload.wikimedia.org/math/9/a/4/9a4cbc3faaaa536d8c82fa8921c5e096.png" alt="E_k = m gamma c^2 - m c^2 = frac{m c^2}{sqrt{1 - v^2/c^2}} - m c^2" /> </p><p>and set v =&nbsp;c, then &nbsp;we'll have to divide on zero; which gives us the kinetic energy for mass with the speed of light E<sub>k</sub> = &infin;.&nbsp;&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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Saiph

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<p>Magnetic sheild?&nbsp; Bah, magnetic ramscoop.&nbsp; Use that matter as reactioni mass for the engines.</p><p>Granted, you'll still have the radiation sleeting off as you accelerate the particles from their "stationary" position to the speed of the ship...</p><p>&nbsp;</p><p>So some other shielding is required.&nbsp; Hard gamma rays are bad, mmm-kay. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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DrRocket

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Can we not use the Lorentz factor to explain? With the relativisitc formula for kinetic energy, and set v =&nbsp;c, then &nbsp;we'll have to divide on zero; which gives us the kinetic energy for mass with the speed of light Ek = &infin;.&nbsp;&nbsp; <br />Posted by Philotas</DIV><br />&nbsp;That is precisely why infinite energy is required to travel at c. <div class="Discussion_UserSignature"> </div>
 
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kelvinzero

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<p>As mentioned this light speed isnt much of a problem for travel in the forseeable future. On top of the issues mentioned, relativity does not prevent you going so fast that you experience the trip as arbitrarily short. At light speed you would experience no time passing at all from your own perspective.</p><p>it is really that darn Newton that made super fast travel so difficult when he stuck us with that law which says that kinetic energy is proportional to the square of the velocity. This means you do not need twice as much energy to go twice as fast, you need four times as much, and to go ten times as fast you need a hundred times as much energy.</p><p>In practice it is this, not relativity, which prevents&nbsp;current designs&nbsp;from maintaining constant 1-g accelerations for years at a time.</p>
 
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skeptic

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>As mentioned this light speed isnt much of a problem for travel in the forseeable future. On top of the issues mentioned, relativity does not prevent you going so fast that you experience the trip as arbitrarily short. At light speed you would experience no time passing at all from your own perspective.it is really that darn Newton that made super fast travel so difficult when he stuck us with that law which says that kinetic energy is proportional to the square of the velocity. This means you do not need twice as much energy to go twice as fast, you need four times as much, and to go ten times as fast you need a hundred times as much energy.In practice it is this, not relativity, which prevents&nbsp;current designs&nbsp;from maintaining constant 1-g accelerations for years at a time. <br /> Posted by kelvinzero</DIV></p><p>Actually the amount of energy required is slightly more than (delta v)^2.&nbsp; This is because the kinetic energy has mass and that mass must be accelerated too.</p><p>As with everything in relativity the answer you get depends upon your perspective.&nbsp; Suppose a rope was streched from earth to the nearest star and was knotted every 300,000 km.&nbsp; An observer (naive about relativity) on a spaceship traveling from earth to the star may try to calculate the ship's velocity by measuring the time between knots.&nbsp; When the ship is traveling at 0.786c he would see the knots passing by at 1 per second and would calculate the ship was traveling at c.&nbsp; His calculation would be confirmed when he reached Proximo Centauri in 4.3 light years.</p><p>If the ship could travel faster than 0.786c, he'd be convinced that he'd travelled faster than the speed of light. How would you persuade him otherwise?</p>
 
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kelvinzero

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Actually the amount of energy required is slightly more than (delta v)^2.&nbsp; This is because the kinetic energy has mass and that mass must be accelerated too.As with everything in relativity the answer you get depends upon your perspective.&nbsp; Suppose a rope was streched from earth to the nearest star and was knotted every 300,000 km.&nbsp; An observer (naive about relativity) on a spaceship traveling from earth to the star may try to calculate the ship's velocity by measuring the time between knots.&nbsp; When the ship is traveling at 0.786c he would see the knots passing by at 1 per second and would calculate the ship was traveling at c.&nbsp; His calculation would be confirmed when he reached Proximo Centauri in 4.3 light years.If the ship could travel faster than 0.786c, he'd be convinced that he'd travelled faster than the speed of light. How would you persuade him otherwise? <br />Posted by skeptic</DIV></p><p>Oh, surely.</p><p>Im just saying that we are not anywhere near having that as our limiting factor. Interstellar travel would look just as daunting in a purely newtonian universe for practical reasons. People often give me the impression that they think einstein is a big bully who ruined space for everybody :) </p><p>If we could 'just keep going faster' which to me implies linear increase in speed for linear expenditure of effort, ie 1g acceleration for&nbsp;extended periods,&nbsp;then we could get to neighbouring stars in just a few years in either purely newtonian or relativistic universes, and the effort would only be something like that of running a decent rocket for years instead of minutes. Hard but not staggeringly hard.<br /></p>
 
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skeptic

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Oh, surely.Im just saying that we are not anywhere near having that as our limiting factor. Interstellar travel would look just as daunting in a purely newtonian universe for practical reasons. People often give me the impression that they think einstein is a big bully who ruined space for everybody :) If we could 'just keep going faster' which to me implies linear increase in speed for linear expenditure of effort, ie 1g acceleration for&nbsp;extended periods,&nbsp;then we could get to neighbouring stars in just a few years in either purely newtonian or relativistic universes, and the effort would only be something like that of running a decent rocket for years instead of minutes. Hard but not staggeringly hard. <br /> Posted by kelvinzero</DIV></p><p>Another limiting factor on the ultimate velocity of a rocket is it's exhaust velocity.&nbsp; I heard once that a rocket can't go faster than the exhaust velocity of the rocket.&nbsp; This relationship is not obvious until you do the math.&nbsp; The problem is that the rocket must accelerate the remaining fuel in addition to the payload.&nbsp; If you estimate that 90% of the rocket's mass is fuel and 10% is payload, you find that the first 86% of the fuel provides about the same acceleration as the last 14%.&nbsp; If you increase the ratio of fuel to payload to 99:1, the first 93.7% of the fuel provides the same amount of acceleration as the last 6.3%. </p>
 
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SpeedFreek

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<p>Here is the problem:</p><p>The Relativistic Rocket.&nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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kelvinzero

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<p>Hi Skeptic,</p><p>I was going to say this was a subset of the v^2 problem but you might be right.. If you expend half your mass to increase by a speed v, then to get to a speed of n*v you have to expend 2^n times your mass? That is exponential, even worse than v^2. Can anyone confirm this?</p><p>Hi SpeedFreek,</p><p>You will notice that the first thing they do is assume a rocket which can accelerate at 1g perpetually.</p>
 
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SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hi SpeedFreek,You will notice that the first thing they do is assume a rocket which can accelerate at 1g perpetually. <br /> Posted by kelvinzero</DIV></p><p>Yes, but I thought the section further down was relevent to the problem you were discussing, where the <em>"fuel is payload"</em> problem is explained.&nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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