Imagine a subway that travels at 4,000 mph.
That is exactly what some people are proposing. Sounds cool.
ET3.com, Inc., an open consortium looking to implement “space travel on Earth,” has begun selling licenses for its Evacuated Tube Transport (ETT) system, which they claim could take travelers from Washington D.C. to Beijing in just 2 hours, without ever leaving the ground. The company and its advocates say this form of transport is safer, cheaper, greener and much, much faster than planes, trains and cars.The systems works (in theory) by putting capsules in an evacuated tube, which accelerates up to 4,000 mph in roughly 3 minutes using linear electric motors. Friction is almost completely eliminated, as passive superconductors allow the capsule to “float” within the tubes. The energy used to accelerate the capsules is then recaptured as they slow down. Capsules could drastically range in size according to their contents.
It sounds really cool but when something goes wrong at 4,000 mph, it goes real wrong.
March 29, 2012 at 3:15 am
Does it come with inertia dampers?
March 29, 2012 at 3:50 am
I'm pretty sure that's more G's than astronauts feel. So I guess it sounds cool until you hop in one and arrive at your destination as soup…
March 29, 2012 at 4:06 am
I think that's actually only 3/4 of a G or so, but definitely something that goes wrong at 4,000 mph goes really wrong, and something that goes wrong at 4,000 mph in a vacuum goes even worse…
March 29, 2012 at 4:37 am
Ultimate speed of 4,000 mph equates to about 5,800 feet per sec, one of the fastest rifle caliber bullets only travels about 4,200 feet per second from the muzzle (.17 Remington). If it takes 3 minutes (180 sec) to ultimate speed, that equates to an acceleration rate of about 32 feet per sec per sec which is 1 g. Totally doable. However, I wouldn't get in that tube unless it was designed and built by the swiss or germans.
March 29, 2012 at 6:56 am
@ most recent anonymous: Give me the Japanese any day over the Swiss or Germans.
Holy mackerel, though. 5800 fps is 1767.8 m/s. And three minutes to get to that…means only 19 minutes to get up to escape velocity, 11,200 m/s. Presumably in a sort of coiled, multi-tiered tunnel…ending in a Verne gun (a cannon that shoots things into orbit, named after the one in From the Earth to the Moon).
Of course, we (meaning science fiction writers) have examined the evacuated-tunnel idea and found it wanting—mainly because of the risk of suffocation in an accident. It'd be interesting to see if real-world trials prove us wrong; forgive me if I don't volunteer to be an early adopter here.
Incidentally, the usual safety measure for this kind of system is to have air-hatches on the tunnel, that can be opened if the cars get stuck, preventing passengers from suffocating.
March 29, 2012 at 10:37 am
I'm just loving all of the physics experts who are showing up on this. Impressive!
March 29, 2012 at 12:06 pm
True, but when something goes wrong at 30,000 feet, it goes pretty wrong, as well.
March 29, 2012 at 2:39 pm
I'd put commercial goods on that transport, but not people. Test it out for a few years moving watermelons and inline skates.
March 29, 2012 at 2:45 pm
I don't need to get anywhere that fast.
March 29, 2012 at 3:34 pm
Ha ha ha! Larry D, when i first read your comment I thought you wrote "inertia diapers". Those might be a good idea as well.
KB
March 29, 2012 at 4:22 pm
That is the coolest thing I have heard in a long long time. I'm onboard for sure. But I want my luggage sent first.
March 29, 2012 at 5:18 pm
Looks virtually terrorist-proof to me. As are all habitrails on tinkertoys.
March 29, 2012 at 8:01 pm
How would families travel together?? Family sized tubes??
March 29, 2012 at 8:15 pm
It sounds really cool but when something goes wrong at 4,000 mph, it goes real wrong.
mainly because of the risk of suffocation in an accident.
Two thoughts:
(1) if something goes wrong at 4,000 mph, it won't last long.
(2) if something goes wrong at 4,000 mph, suffocation would seem to be the lesser worry.
March 29, 2012 at 9:17 pm
That better be a pretty good vacuum – the SR-71 skin surface reached 1100 degrees at 85,000 feet, which is around 1/50 of sea level air pressure. We're talking about something that moves at almost twice that speed . . .
March 31, 2012 at 12:31 am
The biggest challenge IMO is making a tube that runs from DC to Beijing that maintains a total vacuum within. That means it must resist inward pressure of 14.7 psi. Presuming a 10 foot diameter, circumference is approximately 377", meaning it is subject to a compressive force of 5542 pounds per INCH of length. How many inches from DC to Beijing?
March 31, 2012 at 10:29 am
I just realized, this thing is supposed to go in the northern Pacific. As my sister said of a proposed underwater railway connecting Japan and some other country in the Pacific, "At the ribbon-cutting ceremony, they should totally play 'Ring of Fire'."
Because seriously, do you know how many volcanic eruptions and underwater earthquakes, and their attendant tidal waves, the Pacific experiences every year?