+ For instance saying it "has no tracks" but then ... it's in a tube. This seems to be nitpicking, as the tube is effectively a track. The question of whether something uses a track or not is mainly of interest because things that don't use tracks have more flexibility, and can go off-route. Something that requires a fixed guideway (like a tube) is for all intents and purposes, on a track.
+ Most importantly, the tubes would considerably safer than traditional high speed rail, since debris or other obstacles couldn’t get in and block the vehicles.
Er, is "debris and obstacles" an actual safety problem on existing HSR lines? Oh wait, Shinkansen: perfect safety record over 50+ years of very intense operation.
It's pretty clear that grade separation, and some effort to avoid trespassers, are important, but these things are of course standard practice. Putting everything in a tunnel would appear to at best offer a minimal safety improvement, at great additional cost.
+ Similarly, the vague hand-wavy discussion saying that the tubes would be "cheap and easy to construct" seem a bit specious. Either precision is required or not (and at 500+mph, one had better get this right!), and the form of a tube doesn't seem to make much difference compared to other maglev technologies, e.g. the "U-channel" being used by the JR maglev (one of the notable attributes of the JR tech is that it has a very large gap size, and so is less susceptible to precision issues, as compared to e.g. the transrapid tech).
So if you take existing JR maglev tech, and ... add a roof, is it actually any different than the vague "tube" notion this article talks about?
Maybe Musk does have some truly transformative idea, but certainly nothing in this article is that.
[I think Musk's coyness about this is pretty annoying... if he really has a great idea, and intends to make it public, why not just say it instead of making flirty glances and beating around the bush?]
I agree, and it reminds me of nothing so much as the protracted and anticlimactic unveiling of the Segway.
A tech-world-famous entrepreneur coyly keeping mum about some radical new technology that is supposed to CHANGE THE FREAKIN' WORLD, MAN--and then it turns out to be a revolution in keeping airport security guards from having to walk so much.
I'd love to see it be everything Musk promises (just like I'd love to order a personal cold fusion generator from Amazon), but such lofty claims need substantial evidence to have any credibility.
He's not hyping up the next product as much as he's musing about the notes & ideas written down in his journal when people ask him bluntly "what else are you working on?"
And to be fair, Musk's track record on creating things that are going to CHANGE THE FREAKIN' WORLD, MAN is pretty dang good (paypal, tesla, spacex as if I have to even name them).
I wonder if he even took it all that seriously at first, he may not have realized he's made the transition to Man Whose Words Are Given Great Attention.
He seems like he's starting to realize that, but only now...
I would also say that a lot of great ideas when not executed carefully, frankly suck.
With Musk's precision about his products (checking every car himself), I doubt he's going to just say "here's my idea, have at it" without a built in way to implement it, make it happen while maintaining some semblance of control.
Also, Musk explicitly said it's not that ("But Elon has said there’s no vaccuum tubes involved").
The bad effects of air-friction would seem to still be present, and maybe much greater, because you'd have to move a huge mass of air and the friction would be over a much greater surface area (isolating the moving air to within a small portion of the tube does not look simple to me).
f=0.006; %wall friction factor inside tube, also skin friction outside a train
rho=1.2; %air density [kg/m^3]
R=1.5; %tube radius [m]
Vg=0:200; %velocity of tube gas [m/s]
Vt=250; %velocity of train [m/s]
L=500e3; %length of tube [m]
Cd=0.8; %drag coefficient, form drag
trainfill=0.1; %percent of tube filled by train
airfill=1-trainfill; %percent of tube filled by air
ncars=1000; %number of cars in tube
Pg=pi/4fVg.^3LairfillR; %power required to move gas through tube
Pt_fm=ncars0.5rhopiR^2Cd(Vt-Vg).^3; %power required to overcome form drag on each car
Pt_sk=pi/4f(Vt-Vg).^3LtrainfillR; %power required to overcome skin friction drag
Pg_annulus=0; %since the mass of air is so small between the train and tube wall, assume 0.
Pt=Pg+Pt_fm+Pt_sk; %total power requirements
The per-kilometre cost is going to be astronomical.
I don't think one of the problems of maglev is stopping distance: that's mostly constrained by how many G's you want to subject your passengers to.
Most long train tunnels have a secondary tunnel that acts as a buffer for this sort of thing.
A closed tunnel doesn't buy you much.
Mostly-evacuated tube, or at the very least some type of sealed hydraulic (which is problematic) is the obvious plausible idea to achieve supersonic speeds. The problem is structural engineering of a very large negative-pressure-sealed structure in which a fault anywhere could destroy the whole thing. It would need complex airlocks, which would make each station enormously expensive as well.
I would note, however, one of my ideas that may have some synchronicity: that the speed of sound in a gas rises rapidly as the molecule gets less massive, and the drag force drops as the gas becomes less dense. Simultaneously, if hydrogen cars are going to get off the ground they need a distribution pipeline system. A train that traveled in a tube of hydrogen could effectively bypass the 'air' speed of sound and move at at least mach 3 before reaching the H2-transonic range. Sealing STP hydrogen in a container can be done an order of magnitude easier than sealing vacuum or highly pressurized gas.
The "tracks", of course, would be some form of maglev. Ideally, an 'Inductrack' design, which have not been seen in use yet but offer substantial advantages. On the other hand, given the progess on high-temperature superconductor manufacturing, perhaps those advantages are shrinking.
On Googling, it would appear that I'm not the only one to have this notion:
I don't understand attempting to use a propeller-based primer mover, however. A linear induction motor with variable coil spacing, on a multiple unit train, should function just fine for this type of use.
I'd like to hear more about that idea.