A previous HN discussion brought up the possibility of a Launch Loop and several descriptions of that proposal seem to fit very well.
A Launch Loop is an iron cable just 2 inches thick that runs inside of a sheath at tens of thousands of miles an hour. The sheath has electromagnets inside of it to accelerates the cable. The motion of the cable would cause the loop to curve and raise into the sky.
To outside observers, it would look like a giant version of the St. Louis arch with the peak nearly in low earth orbit, but only a few inches thick. The magic comes with the fact that the iron cable can be used for travel by using electromagnetic attraction to the iron cable through the sheath.
What's interesting is that while there are several engineering challenges, unlike a space elevator, this wouldn't require any materials technologies that don't already exist today. The iron cable could be made by existing forges that make the cabling for bridges, and the electromagnetic sheath could borrow a lot of existing technologies from the hard drive manufacturing industry.
It would also fit with his previous work on Space X and Solar Cities to some extent.
A launch loop can be used to transport cargo or passengers high enough that the energy required to get them into orbit is very inexpensive, which ties into his Space X work.
The external sheath of the Launch Loop could have solar panels on it to power the electromagnets that help keep the loop in motion, and even when the sun goes down, millions of tons of iron spinning like a flywheel has enough kinetic energy to keep going until the sun rises again.
I wouldn't be surprised if he ran across the concept when he was researching ways to get into space before he founded Space X, and it's his "Step 2".
Lastly, if you had a giant cable stretched across the sky that worked kind of like a bicycle brake cable in its sheath, but the cable was running through the system at 30k mph in a giant loop, what better name than Hyperloop? It also explains why a trip that he describes as being twice as fast as an airplane would take 30 minutes. It takes more time to go to LEO and back down
Keep an eye out for Musk buying any patents on electromagnetics or him buying a oceanic cable-laying ship.
Musk explicitly mentions, "If you put solar panels on it, you generate more power than you would consume in the system. There's a way to store the power so it would run 24/7 without using batteries." [1]
I think that might be true of launch loops? The cable has incredible kinetic energy, but it is magnetically suspended in a vacuum tube, so its power loss could be low.
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.
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.
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
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"?
>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?
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.)
Also of interest, the worlds most authoritative subject on Launch Loops is Keith Lofstrom [1]. He maintains a wiki on the subject with amazing information on the concept. [2]
He also maintains a wiki on one of his other projects, Server Sky, a push to get a cloud of micro-satellites in orbit for public access. A literal cloud of servers. [3]
What caught my eye is that Keith Lofstrom spoke at the International Space Development Conference (ISDC) this year and he has a ton of patents under his belt. He's not a kook and seems to really have done his homework on the subject. That makes me think that it's a plausible technology.
What happens to the sonic boom in this scenario? I understand that is the main obstacle to conventional supersonic flights above or close to land, how would this be different?
The tubed is pumped vacuum. See http://launchloop.com/VelocityShear. That also argumentatie that having a heavy fast-moving Core close to a heavy stationery ouder tube is less of a problem than having a hard disk platter close to a stationry 1 gram (possibly less) disk head. I do not quite get that. The damage, once something goes wrong, is way higher, so we should make a much larger effort to decrease the probability that something goes wrong.
That sounds interesting for, say, a sci-fi novel, but in the real world I wouldn't want to be responsible for dealing with infrastructure maintenance, earthquakes, tornadoes... Can you imagine if even part of something like that collapsed?
Over the ocean? Would be relatively minor impact even for a catastrophic failure.
The thing is the speeds - anything that can do NYC-LA in minutes is going to have a catastrophic failure mode that kills everyone in a big radius. I am just trying to imagine the London Underground at 14,000 mph.
I guess the only problem with his is your have to put it 5+ miles out into the ocean and there's really no way you can sail out that far, take the trip and sail back in under 30 minutes.
A Launch Loop is an iron cable just 2 inches thick that runs inside of a sheath at tens of thousands of miles an hour. The sheath has electromagnets inside of it to accelerates the cable. The motion of the cable would cause the loop to curve and raise into the sky.
To outside observers, it would look like a giant version of the St. Louis arch with the peak nearly in low earth orbit, but only a few inches thick. The magic comes with the fact that the iron cable can be used for travel by using electromagnetic attraction to the iron cable through the sheath.
What's interesting is that while there are several engineering challenges, unlike a space elevator, this wouldn't require any materials technologies that don't already exist today. The iron cable could be made by existing forges that make the cabling for bridges, and the electromagnetic sheath could borrow a lot of existing technologies from the hard drive manufacturing industry.
It would also fit with his previous work on Space X and Solar Cities to some extent.
A launch loop can be used to transport cargo or passengers high enough that the energy required to get them into orbit is very inexpensive, which ties into his Space X work.
The external sheath of the Launch Loop could have solar panels on it to power the electromagnets that help keep the loop in motion, and even when the sun goes down, millions of tons of iron spinning like a flywheel has enough kinetic energy to keep going until the sun rises again.
I wouldn't be surprised if he ran across the concept when he was researching ways to get into space before he founded Space X, and it's his "Step 2".
Lastly, if you had a giant cable stretched across the sky that worked kind of like a bicycle brake cable in its sheath, but the cable was running through the system at 30k mph in a giant loop, what better name than Hyperloop? It also explains why a trip that he describes as being twice as fast as an airplane would take 30 minutes. It takes more time to go to LEO and back down
Keep an eye out for Musk buying any patents on electromagnetics or him buying a oceanic cable-laying ship.
http://en.wikipedia.org/wiki/Launch_loop