tag:blogger.com,1999:blog-7494544263897150929.post9169701327106062662..comments2011-09-16T19:36:32.987-07:00Rickhttp://www.blogger.com/profile/16932015378213238346noreply@blogger.comBlogger249125tag:blogger.com,1999:blog-7494544263897150929.post-65455926333101602212011-09-16T19:36:32.987-07:002011-09-16T19:36:32.987-07:00Ok, I finally got to the correct site, and you&#39;re right, it does go into much greater detail than the previous article I read. However, it didn&#39;t change my understanding of the basic device; you can use the thing to either generate thrust or power, and it isn&#39;t a self-sustaining reaction; turn off the laser and the reaction dies. I also don&#39;t see any mention of the power produced (the ion stream of Alpha particles) to be sufficent to power the thing; on the other hand, the laser does seem to be of overall low power and the magnetic nozzel just needs to be powerful enough to get the ion stream going in the general direction; that being said, it does seem to be a very PMF type of rocket engine...if it can be made to work as advertised. We should know in about ten years or so, one way or the other.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-8161813455440598682011-09-15T09:32:18.603-07:002011-09-15T09:32:18.603-07:00Thucydides:<br /><br /><i>&quot;While the article does say you can use this method for electrical generation, it is only an incidental paragraph near the end, so I don&#39;t think the author is suggesting this is a dual mode system...&quot;</i><br /><br />I don&#39;t recall that anyone said anything about dual modes. But the author does mention electrical power generation, and in more places than just the end:<br /><br />&quot;Thus energetic alpha particles<br />“exhaust “ momentum can be used directly to produce high ISP thrust and also offer possibility of<br />power conversion into electricity.&quot;<br /><br />&quot;Proton-triggered 11boron fuel (p-11B) offers the<br />potential for abundant ion kinetic energy for in-space vectored thrust applications as well<br />as for direct energy conversion in specialized direct electrical energy conversion plants.&quot;<br /><br />&quot;This<br />kinetic energy can be converted directly into electricity via conversion techniques based on<br />mature technology derived from other fields, such as microwave technology, resonance-tuned<br />rectennae which entails equipment that is more compact and potentially cheaper than that<br />involved in conventional thermal production of electricity.&quot;<br /><br />&quot;Energetic alpha particle &#39;exhaust&#39;<br />momentum can be used directly to produce high ISP thrust and also offers the possibility<br />of direct power conversion into electricity.&quot;<br /><br /><i>&quot;One last point; given the configuration in the diagrams, it seems to me that the beam of alpha particles would already be fairly focused coming out of the reaction chamber, which would allow for a smaller and lighter magnetic nozzel. Is this a correct observation, or am I missing something here?&quot;</i><br /><br />That diagram is a bit misleading. By their very nature, alpha particles are emitted at a wide variety of angles from the initial event. They have to be directed by an electromagnetic field if you want to focus their effect in a certain direction.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-75722400409375124292011-09-14T19:10:57.328-07:002011-09-14T19:10:57.328-07:00Sorry the link didn&#39;t seem to work for you, but I tried the various work arounds posted and they did work (for people interested in the article).<br /><br />While the article does say you can use this method for electrical generation, it is only an incidental paragraph near the end, so I don&#39;t think the author is suggesting this is a dual mode system. If anyone were to consider this as a dual mode system, it would probably be &quot;either/or&quot;; using it for thrust or running it to generate electrical energy (although I don&#39;t see this as being able to generate excess power to run itself and the hotel power for the ship).<br /><br />One last point; given the configuration in the diagrams, it seems to me that the beam of alpha particles would already be fairly focused coming out of the reaction chamber, which would allow for a smaller and lighter magnetic nozzel. Is this a correct observation, or am I missing something here?Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-14885558838954762852011-09-14T08:17:34.343-07:002011-09-14T08:17:34.343-07:00Milo:<br /><br /><i>&quot;*sigh*<br /><br />...Guys, this is how you do it.&quot;</i><br /><br /><i>Sigh</i>. <a href="http://www.areaparks.com" rel="nofollow">I develop web applications</a> for a living.<br /><br /><br /><br />=Milo=Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-42219465644072861862011-09-13T21:11:13.995-07:002011-09-13T21:11:13.995-07:00*sigh*<br /><br />...Guys, <a href="http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110014263_2011014853.pdf" rel="nofollow">this</a> is how you do it.<br /><br /><br /><br />=Milo=Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-28203183178549156452011-09-13T20:48:27.953-07:002011-09-13T20:48:27.953-07:00Trying again:<br /><br />http://ntrs.nasa.gov/archive/<br />nasa/casi.ntrs.nasa.gov/<br />20110014263_2011014853.pdf<br /><br />(Remove the newline characters before you paste into your address bar.)Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-34688025117550542052011-09-13T20:47:10.594-07:002011-09-13T20:47:10.594-07:00Or I could just give you the link raw:<br /><br />http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110014263_2011014853.pdfTonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-16629101323138606072011-09-13T20:44:25.703-07:002011-09-13T20:44:25.703-07:00Ferrell:<br /><br /><i>If this drive (that I can&#39;t get the link to work), is not that fusion drive, then please accept my apologes.</i><br /><br />It is the drive, but the article has a bit wider scope than propulsion. You can get to it by highlighting and copying the link plus all the text after it, paste into a text editor, and select the actual url at the beginning of the string. It&#39;s a .pdf file, so you shouldn&#39;t have any trouble selecting just the url.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-26831317498274666502011-09-13T17:00:02.987-07:002011-09-13T17:00:02.987-07:00Tony, I&#39;d read the article if the damned link would work; I obviously thought you two were still talking about the bi-foil laser pulse ignited fusion drive that we talked about earlier; that drive is not designed to be self-sustaining, and I did make the comment that you&#39;d need an MHD on the output of the drive to get any power from it; as far as I can tell, you would either get electrical power or thrust from the thing, but not much of both or either.<br /><br />If this drive (that I can&#39;t get the link to work), is not that fusion drive, then please accept my apologes.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-32260161550822590662011-09-12T19:56:00.398-07:002011-09-12T19:56:00.398-07:00Ferrell:<br /><br /><i>&quot;Tony, I think that the whole point of this drive is that you don&#39;t need to sustain a fusion reaction for the drive to work. It isn&#39;t designed to be self-sustaining or power generating; like a rocket, it is primarily for propulsion.&quot;</i><br /><br />You should read the linked document. It makes very specific and unambiguous mention of electrical power generation. Also, if it was just about generating energetic ions, then it <i>does</i> require more poweful (and thus more power intensive) magnetic confinement to direct the exhaust. TANSTAAFL.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-76203910785130387982011-09-12T18:10:28.527-07:002011-09-12T18:10:28.527-07:00Tony, I think that the whole point of this drive is that you don&#39;t need to sustain a fusion reaction for the drive to work. It isn&#39;t designed to be self-sustaining or power generating; like a rocket, it is primarily for propulsion.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-12593042626279212142011-09-12T11:07:35.999-07:002011-09-12T11:07:35.999-07:00Thucydides:<br /><br /><i>&quot;If I am reading the paper correctly, confinement isn&#39;t an issue since this reaction is not self sustaining. Each reaction is triggered by a burst of laser energy starting a &quot;cascade&quot; in the metal foil, releasing high energy protons which triggers a burst of fusion energy in the 11B fuel.<br /><br />No magnetic confinement, no electrostatic fields, no magitech (that I can see), just an energetic reaction in the fuel releasing a stream of alpha particles which can be used for high ISP thrust or captured for electrical energy on board. <br /><br />The apparatus to do this looks like it can be set up on a lab tabletop, so the testing to see if it really works and if it is scalable could be done quickly and easily compared to may of the other schemes being proposed.&quot;</i><br /><br />As described it&#39;s a novel means for generating highly energetic ions for propulsion purposes. It still requires electromagnetic fields to direct those ions out the rear end. And they have to be much stronger fields that you might find in a Hall effect or grid type thruster, because the ions are so much more energetic. YOu have to have external power for those fields and for the excitment lasers, control circuitry, ship&#39;s service circuits, etc. <br /><br />In addition, considering the very low gain of the described reaction, I&#39;m having trouble seeing that it could ever be a self-sustaining power source, much less one can generate utility power above it&#39;s own operating needs.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-33170279727863469142011-09-12T09:38:15.116-07:002011-09-12T09:38:15.116-07:00If I am reading the paper correctly, confinement isn&#39;t an issue since this reaction is not self sustaining. Each reaction is triggered by a burst of laser energy starting a &quot;cascade&quot; in the metal foil, releasing high energy protons which triggers a burst of fusion energy in the 11B fuel.<br /><br />No magnetic confinement, no electrostatic fields, no magitech (that I can see), just an energetic reaction in the fuel releasing a stream of alpha particles which can be used for high ISP thrust or captured for electrical energy on board. <br /><br />The apparatus to do this looks like it can be set up on a lab tabletop, so the testing to see if it really works and if it is scalable could be done quickly and easily compared to may of the other schemes being proposed.Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-80513633543677727582011-09-12T08:57:42.251-07:002011-09-12T08:57:42.251-07:00Thucydides:<br /><br /><i>&quot;Another compact fusion drive idea, this one uses aneutronic reactions (p-11B) which is so much better from many angles.&quot;</i><br /><br />Only if you totally ignore the fact that aneutronic fusion requires plasma confinement and sustainment orders of magnitude beyond even the most pessimistic assumptions about D-T fusion plasmas.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-38608181233255673322011-09-10T21:34:32.695-07:002011-09-10T21:34:32.695-07:00Another compact fusion drive idea, this one uses aneutronic reactions (p-11B) which is so much better from many angles. So far as I understand the paper, this is a pulsed drive like ORION, only using high frequency pulses of relatively low power for thrust. Since it does not relay on self sustaining fusion reactions, it seems much more feasible than many other schemes.<br /><br />Read about it here: <a rel="nofollow">http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110014263_2011014853.pdf</a>Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-21512724319814524902011-09-09T17:50:25.518-07:002011-09-09T17:50:25.518-07:00Thucydide<br /><br />Your example of the two polar expeditions is actually closer to the point I was trying to make; except for the whole starving and freezing to death, using the lessons of early expeditions to help guide the developement of later life support and radiation shielding. We have a lot of options with propulsion (either at hand, or on the drawing boards) but we are still worried about both adiqute shielding and effective life support for long term space travel; the experiances with the ISS have gone a long way to expand our knowledge, but we still have a ways to go.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-38991338448331275312011-09-08T22:33:18.994-07:002011-09-08T22:33:18.994-07:00Ferrell<br /><br />The evidence does not seem to support you. NERVA engines were considered fight ready before the program was cancelled, and these were quite powerful engines in very compact packages (say the size of a minivan) that could generate GW of thermal energy. Despite this, only a very marginal expedition to Mars was possible using the technology; a six man bulked up Apollo mission.<br /><br />Thank you for reminding me of the Ross expedition; obviously leadership and preparation are very important as well. However, since the Franklin expedition was not as well planned or led, the minimum margin available was rapidly used up. Later expeditions learned to live off the land, greatly expanding their margin without expanding the ship or logistical support needed to carry out the expedition. (This partially explains my fascination with things like Solar Sails; you are harnessing the environment and minimizing the mass and energy needed to bring the important stuff to the destination).Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-13795418462542770112011-09-07T17:56:55.506-07:002011-09-07T17:56:55.506-07:00Well, since no one knows yet if these little reactors are viable or not, much less if they are scalable, then perhaps we should wait until we have a little more data about them before we try to make intelligent arguments regarding them.<br /><br />On another note, I do think that developing better shielding and life support technology would allow longer trips with exsiting technology; it should spur space propulsion technology advancement to make fuller use of the extended ability of spacecraft crews to spend in space.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-17145786229873728732011-09-07T09:11:51.077-07:002011-09-07T09:11:51.077-07:00Tony:<br /><br /><i>&quot;It also doesn&#39;t mean that there aren&#39;t workarounds...we just need to find out before we build the things.&quot;</i><br /><br />Actually, there very rarely are workarounds. Brute forcing scalability issues just doesn&#39;t work, because complexity and geometry issues make the thing unworkable. It turns out that you just need bigger boilers for bigger ships and bigger engines for bigger jets. I can&#39;t see anything fundamentally different about nuclear reactor technology that would break that principle.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-58292421156975949542011-09-07T08:34:35.792-07:002011-09-07T08:34:35.792-07:00=Milo=<br /><br /><br /><br />I looked up the <a href="http://en.wikipedia.org/wiki/Franklin%27s_lost_expedition" rel="nofollow">Franklin expedition</a> (to the Arctic), and note that the same ships had previously taken part in the successful <a href="http://en.wikipedia.org/wiki/James_Clark_Ross#Antarctic_explorer" rel="nofollow">Ross expedition</a> (to the Antarctic), which carried the same amount of crew.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-21525901019271809472011-09-06T20:12:22.674-07:002011-09-06T20:12:22.674-07:00We can send small packages to Mars, but large ships suitable for human explorers and all their kit is beyond most current technology. <br /><br />The &quot;classic&quot; NTR missions from the 1970&#39;s had three stage NERVA engined ships assembled in LEO (with three parallel stages to boost the ship out of LEO) to send a bulked up Apollo mission to Mars. I&#39;m sure the astronauts wold have been very keen being stuck in a can for six months one way...<br /><br />For another historical analogy. we are planning to go the way of the Franklin expedition, carrying everything into a hostile environment in very marginal ships. We can hope the outcome is not repeated.Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-58489557512284867922011-09-06T17:31:21.665-07:002011-09-06T17:31:21.665-07:00Tony said:&quot;The problem is that if the reactors can&#39;t be scaled, that doesn&#39;t necessarily mean there&#39;s a workaround.&quot;<br /><br />It also doesn&#39;t mean that there aren&#39;t workarounds...we just need to find out before we build the things.<br /><br />Maybe instead of worrying about drives (we seem to be able to send stuff to Mars already), maybe we should try to come up with better shielding and life support. That, in my opinion, would go a long ways toward creating a reliable interplanetary transport.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-79107488767250230912011-09-05T22:59:12.375-07:002011-09-05T22:59:12.375-07:00Ferrell:<br /><br /><i>&quot;If I remember correctly, the argument was started by wondering about the scalability of these little reactors; if they can&#39;t be scaled up, then you have to get creative with them; if they can be scaled up, then it&#39;s all moot.&quot;</i><br /><br />The problem is that if the reactors can&#39;t be scaled, that doesn&#39;t necessarily mean there&#39;s a workaround.Tonynoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-43729019451322092092011-09-04T12:08:05.281-07:002011-09-04T12:08:05.281-07:00If I remember correctly, the argument was started by wondering about the scalability of these little reactors; if they can&#39;t be scaled up, then you have to get creative with them; if they can be scaled up, then it&#39;s all moot.<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-90687781890557362272011-09-03T19:35:53.434-07:002011-09-03T19:35:53.434-07:00I don&#39;t really see the point of multiple small reactors given the need to provide energy in the Gigawatt range for either electric or NTR drives. Perhaps I am missing something in your argument.<br /><br />By analogy, modern nuclear submarines only use one powerful reactor rather than a bunch of smaller ones, the few exceptions that I know of use two reactors due to the space limitations in the hull. A spaceship in free space would not have that sort of limitation.<br /><br />Another useful analogy might be to compare steam powered ships to modern counterparts using diesel or turbine powerplants. Raising steam from multiple boilers and ensuring the proper amount of steam is available (on top of managing multiple steam expansion engines) adds many levels of complexity compared to using IC engines.Thucydideshttp://www.blogger.com/profile/09828932214842106266noreply@blogger.com