<story><title>Hyperloop</title><url>http://www.spacex.com/hyperloop</url></story><parent_chain><item><author>Anechoic</author><text>&lt;i&gt;I don&amp;#x27;t believe that an experimental tube is going to be somehow magically cheaper and easier to route and build than train tracks.&lt;/i&gt;&lt;p&gt;&lt;i&gt;Do you really think the special interests that are making HSR so difficult and expensive would say, &amp;quot;Oh, do whatever you like with your tube.&amp;quot;?&lt;/i&gt;&lt;p&gt;These are extremely important issues that advocates seem to be glossing over. Putting the guideway on pylons doesn&amp;#x27;t magically eliminate land issues, you will still have to deal with visual impacts, along with any number of anticipated and unanticipated problems.&lt;p&gt;Musk should do what the Germans did with the TR0x series of maglev vehicles, build a 10-20 mile test section someplace and demonstrate that is analysis is sound.&lt;p&gt;&lt;i&gt;(perhaps more in the future--why wouldn&amp;#x27;t California design with this goal [350 km&amp;#x2F;h] in mind?)&lt;/i&gt;&lt;p&gt;There are a variety of reasons, but one important reason I have to deal with is that the speed of shear waves through soil is only on the order of a couple of hundred miles per hour. When a train exceeds the shear wave speed, ground-borne vibration waves &amp;quot;build up&amp;quot; in a manner similar to the shock wave created in air when a plane exceeds the speed of sound, causing a ground-borne vibration equivalent of a &amp;quot;sonic boom&amp;quot; that can cause problems for wayside structures. I believe the French have started to experience this with some of their higher-speed TGV experiments and we don&amp;#x27;t have a good way to handle this yet.</text></item><item><author>goodcanadian</author><text>I am intrigued, but not overwhelmed. Many of his reasons why his hyperloop is superior to high speed rail are not specific to the hyperloop. For example, you can put railway tracks up on pylons, too, with very little impact on the ground. It is common to do this in urban areas, but it is rarely done in rural areas because it is flat out cheaper to put it on the ground. I don&amp;#x27;t believe that an experimental tube is going to be somehow magically cheaper and easier to route and build than train tracks.&lt;p&gt;Now, I am not trying to defend California&amp;#x27;s HSR, specifically. I agree with Musk that it appears to be very poorly done. However, the answer, to my mind, is to do it properly rather than propose a wild experiment with hand-wavy arguments as to why it would be politically easier to do. Do you really think the special interests that are making HSR so difficult and expensive would say, &amp;quot;Oh, do whatever you like with your tube.&amp;quot;?&lt;p&gt;Now, in an attempt to end on a positive note, I do like his proposal as a possible next step beyond HSR. Rail can go up to 350km&amp;#x2F;h currently (perhaps more in the future--why wouldn&amp;#x27;t California design with this goal in mind?), but Musk&amp;#x27;s hyperloop is proposed up to ~1000km&amp;#x2F;hr. It is definitely an idea worth exploring, but I think it falls far short as a serious alternative to the current high speed rail plans.</text></item></parent_chain><comment><author>yk</author><text>&amp;gt;  one important reason I have to deal with is that the speed of shear waves through soil is only on the order of a couple of hundred miles per hour.&lt;p&gt;Perhaps a stupid question, but the shock wave forms because the trains is moving continuously over the ground? So if you put the entire thing on stilts, there would be one wave formed at t0, x0 when the train reaches pylon 0 and the next wave would be at t1, x1 etc. So the interference pattern for the waves would look vastly different. ( This holds of course only for point like trains... )</text></comment>
<story><title>Hyperloop</title><url>http://www.spacex.com/hyperloop</url></story><parent_chain><item><author>Anechoic</author><text>&lt;i&gt;I don&amp;#x27;t believe that an experimental tube is going to be somehow magically cheaper and easier to route and build than train tracks.&lt;/i&gt;&lt;p&gt;&lt;i&gt;Do you really think the special interests that are making HSR so difficult and expensive would say, &amp;quot;Oh, do whatever you like with your tube.&amp;quot;?&lt;/i&gt;&lt;p&gt;These are extremely important issues that advocates seem to be glossing over. Putting the guideway on pylons doesn&amp;#x27;t magically eliminate land issues, you will still have to deal with visual impacts, along with any number of anticipated and unanticipated problems.&lt;p&gt;Musk should do what the Germans did with the TR0x series of maglev vehicles, build a 10-20 mile test section someplace and demonstrate that is analysis is sound.&lt;p&gt;&lt;i&gt;(perhaps more in the future--why wouldn&amp;#x27;t California design with this goal [350 km&amp;#x2F;h] in mind?)&lt;/i&gt;&lt;p&gt;There are a variety of reasons, but one important reason I have to deal with is that the speed of shear waves through soil is only on the order of a couple of hundred miles per hour. When a train exceeds the shear wave speed, ground-borne vibration waves &amp;quot;build up&amp;quot; in a manner similar to the shock wave created in air when a plane exceeds the speed of sound, causing a ground-borne vibration equivalent of a &amp;quot;sonic boom&amp;quot; that can cause problems for wayside structures. I believe the French have started to experience this with some of their higher-speed TGV experiments and we don&amp;#x27;t have a good way to handle this yet.</text></item><item><author>goodcanadian</author><text>I am intrigued, but not overwhelmed. Many of his reasons why his hyperloop is superior to high speed rail are not specific to the hyperloop. For example, you can put railway tracks up on pylons, too, with very little impact on the ground. It is common to do this in urban areas, but it is rarely done in rural areas because it is flat out cheaper to put it on the ground. I don&amp;#x27;t believe that an experimental tube is going to be somehow magically cheaper and easier to route and build than train tracks.&lt;p&gt;Now, I am not trying to defend California&amp;#x27;s HSR, specifically. I agree with Musk that it appears to be very poorly done. However, the answer, to my mind, is to do it properly rather than propose a wild experiment with hand-wavy arguments as to why it would be politically easier to do. Do you really think the special interests that are making HSR so difficult and expensive would say, &amp;quot;Oh, do whatever you like with your tube.&amp;quot;?&lt;p&gt;Now, in an attempt to end on a positive note, I do like his proposal as a possible next step beyond HSR. Rail can go up to 350km&amp;#x2F;h currently (perhaps more in the future--why wouldn&amp;#x27;t California design with this goal in mind?), but Musk&amp;#x27;s hyperloop is proposed up to ~1000km&amp;#x2F;hr. It is definitely an idea worth exploring, but I think it falls far short as a serious alternative to the current high speed rail plans.</text></item></parent_chain><comment><author>javert</author><text>&amp;gt; Musk should do what the Germans did with the TR0x series of maglev vehicles&lt;p&gt;Musk has already given more than enough for the world and done more than enough. Somebody should do it, but we should not expect him to do it.</text></comment>