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I put forward my argument here: https://news.ycombinator.com/item?id=4806458 https://news.ycombinator.com/item?id=4806458 Of course, Elon Musk had to throw a w

I put forward my argument here: https://news.ycombinator.com/item?id=4806458 https://news.ycombinator.com/item?id=4806458 Of course, Elon Musk had to throw a wrench in it. From SXSW: >[The Hyperloop is] not exactly a train. It's a new mode of transportation that doesn't exist. It could be underground or above-ground. An underground Lofstrom loop seems unlikely. The most revealing hints are the speed and the cost. Musk says it'll be cheaper than the LA-SF high-speed rail, which is so expensive because the allowable turn radius is enormous. Their right-of-way acquisition is constrained by ruthless physics. Since the allowable radius scales as square of velocity, anything doing LA-SF in 30 minutes will move more or less in a straight line (except near the endpoints). So it has to be a straight line, but also avoid right-of-way issues. In my mind the Lofstrom loop is still the only option that fits.

jholman 13y ago
The people who originated the concept of the launch loop wanted to solve problems of launching spacecraft, thus the name. Elon Musk wants to commute faster between LA and SF, because he does that 400 mile commute 4 times a week. (Obviously Elon also very much wants to launch spacecraft, but maybe has reasons to ignore the launch loop for that purpose.) With that in mind, is there any reason a launch loop needs to be vertically oriented? Why can't it go, you know, SF, LA, San Diego, Las Vegas, Reno? And if so, why can't parts of it be "underground or above-ground"?
- schiffern 13y ago
  >maybe has reasons to ignore the launch loop for that purpose True. I think you would probably agree that they're more technical than anti-competitive. Musk has called space elevators a long-term optimization, but points out that you still need rockets anyway. Engineering-wise, a small loop is a lot easier than an orbit-capable loop. >is there any reason a launch loop needs to be vertically oriented? In the canonical implementation, the loop is actually fired horizontally from the base stations. The curve ofhe Earth makes the angle for the vertical component. You're quite right, of course, that the optimized design for launching is different from the optimized design for transport. I picture in my head a >20° departure angle, but I haven't run the math so I really don't know. I don't quite understand your question. Could you clarify?
- btilly 13y ago
  Obviously Elon also very much wants to launch spacecraft, but maybe has reasons to ignore the launch loop for that purpose. Elon wants to be able to launch rockets that can land vertically on Mars. A spacecraft capable version of a launch loop is a wonderful optimization, but doesn't get him to the rocket technology you need to colonize a planet that does not yet have the technology to build such a launch loop. (Plus he has contracts to fulfill that he can't meet in time with a launch loop.)
deftnerd 13y ago
Lofstrom has lately been talking about "PowerLoops" - basically underground loops that run for many miles under railroad right-of-ways in order to store energy from windfarms and solar arrays. He seems to indicate that the ROI could be as short as months by buying utility power at night when its cheap and reselling it during the day. Perhaps if the loops were along railroad tracks, they could be used to propel trains? Probably not, but as a power storage method, they can be underground. http://launchloop.com/PowerLoopAbstract http://launchloop.com/PowerLoopAbstract
Dn_Ab 13y ago
Actually, I still think you are right. You know how in pictionary when someone gives an absurd suggestion that is actually not so absurd because you end up mentally responding with 'I guess if you look at it like blah blah..'? I think that's what is going on here. Musk is thinking, I guess if you put a train in an evacuated tube such that friction was not an issue, and moved it electromagnetically using above ground solar, you could reach supersonic speeds and a lot of the same scientific principles would be shared or be in use. That would fit the idea of a railgun+air hockey+concorde. You could share a lot of the same type of engineers on both projects even though the devices are not related in actuality. He is playing fast and loose interpretation wise and switching between talking about the interface Hyperloop and the particular instantiation he has in mind. It's the only way I can think of where he can claim it's not a vacutrain at the same time as say it could work underground. But the launch loop fits so much better, in particular because of the massive kinetic energies involved (no batteries for store) and how very well it works with space travel. Even if this particular incarnation doesn't help, it would be invaluable in terms of experience and proof of concept.

jholman 13y ago

The people who originated the concept of the launch loop wanted to solve problems of launching spacecraft, thus the name. Elon Musk wants to commute faster between LA and SF, because he does that 400 mile commute 4 times a week. (Obviously Elon also very much wants to launch spacecraft, but maybe has reasons to ignore the launch loop for that purpose.) With that in mind, is there any reason a launch loop needs to be vertically oriented? Why can't it go, you know, SF, LA, San Diego, Las Vegas, Reno? And if so, why can't parts of it be "underground or above-ground"?

schiffern 13y ago
>maybe has reasons to ignore the launch loop for that purpose True. I think you would probably agree that they're more technical than anti-competitive. Musk has called space elevators a long-term optimization, but points out that you still need rockets anyway. Engineering-wise, a small loop is a lot easier than an orbit-capable loop. >is there any reason a launch loop needs to be vertically oriented? In the canonical implementation, the loop is actually fired horizontally from the base stations. The curve ofhe Earth makes the angle for the vertical component. You're quite right, of course, that the optimized design for launching is different from the optimized design for transport. I picture in my head a >20° departure angle, but I haven't run the math so I really don't know. I don't quite understand your question. Could you clarify?
btilly 13y ago
Obviously Elon also very much wants to launch spacecraft, but maybe has reasons to ignore the launch loop for that purpose. Elon wants to be able to launch rockets that can land vertically on Mars. A spacecraft capable version of a launch loop is a wonderful optimization, but doesn't get him to the rocket technology you need to colonize a planet that does not yet have the technology to build such a launch loop. (Plus he has contracts to fulfill that he can't meet in time with a launch loop.)

deftnerd 13y ago

Lofstrom has lately been talking about "PowerLoops" - basically underground loops that run for many miles under railroad right-of-ways in order to store energy from windfarms and solar arrays. He seems to indicate that the ROI could be as short as months by buying utility power at night when its cheap and reselling it during the day. Perhaps if the loops were along railroad tracks, they could be used to propel trains? Probably not, but as a power storage method, they can be underground. http://launchloop.com/PowerLoopAbstract http://launchloop.com/PowerLoopAbstract

Dn_Ab 13y ago

Actually, I still think you are right. You know how in pictionary when someone gives an absurd suggestion that is actually not so absurd because you end up mentally responding with 'I guess if you look at it like blah blah..'? I think that's what is going on here. Musk is thinking, I guess if you put a train in an evacuated tube such that friction was not an issue, and moved it electromagnetically using above ground solar, you could reach supersonic speeds and a lot of the same scientific principles would be shared or be in use. That would fit the idea of a railgun+air hockey+concorde. You could share a lot of the same type of engineers on both projects even though the devices are not related in actuality. He is playing fast and loose interpretation wise and switching between talking about the interface Hyperloop and the particular instantiation he has in mind. It's the only way I can think of where he can claim it's not a vacutrain at the same time as say it could work underground. But the launch loop fits so much better, in particular because of the massive kinetic energies involved (no batteries for store) and how very well it works with space travel. Even if this particular incarnation doesn't help, it would be invaluable in terms of experience and proof of concept.