Hyperloop - Elon Musk's Alternative to High-Speed Rail

[TheMentat]

Pretty cool:

Hyperloop
- by Elon Musk

When the California “high speed” rail was approved, I was quite disappointed, as I know many others were too. How could it be that the home of Silicon Valley and JPL – doing incredible things like indexing all the world’s knowledge and putting rovers on Mars – would build a bullet train that is both one of the most expensive per mile and one of the slowest in the world? Note, I am hedging my statement slightly by saying “one of”. The head of the California high speed rail project called me to complain that it wasn’t the very slowest bullet train nor the very most expensive per mile.

The underlying motive for a statewide mass transit system is a good one. It would be great to have an alternative to flying or driving, but obviously only if it is actually better than flying or driving. The train in question would be both slower, more expensive to operate (if unsubsidized) and less safe by two orders of magnitude than flying, so why would anyone use it?

If we are to make a massive investment in a new transportation system, then the return should by rights be equally massive. Compared to the alternatives, it should ideally be:

Safer
Faster
Lower cost
More convenient
Immune to weather
Sustainably self-powering
Resistant to Earthquakes
Not disruptive to those along the route

Is there truly a new mode of transport – a fifth mode after planes, trains, cars and boats – that meets those criteria and is practical to implement? Many ideas for a system with most of those properties have been proposed and should be acknowledged, reaching as far back as Robert Goddard’s to proposals in recent decades by the Rand Corporation and ET3.

Unfortunately, none of these have panned out. As things stand today, there is not even a short distance demonstration system operating in test pilot mode anywhere in the world, let alone something that is robust enough for public transit. They all possess, it would seem, one or more fatal flaws that prevent them from coming to fruition.

Constraining the Problem

The Hyperloop (or something similar) is, in my opinion, the right solution for the specific case of high traffic city pairs that are less than about 1500 km or 900 miles apart. Around that inflection point, I suspect that supersonic air travel ends up being faster and cheaper. With a high enough altitude and the right geometry, the sonic boom noise on the ground would be no louder than current airliners, so that isn’t a showstopper. Also, a quiet supersonic plane immediately solves every long distance city pair without the need for a vast new worldwide infrastructure.

However, for a sub several hundred mile journey, having a supersonic plane is rather pointless, as you would spend almost all your time slowly ascending and descending and very little time at cruise speed. In order to go fast, you need to be at high altitude where the air density drops exponentially, as air at sea level becomes as thick as molasses (not literally, but you get the picture) as you approach sonic velocity.


Continue Reading...hyperloop-alpha.pdf

[John Rogers]

That would work really well, at least going TO Sacredemto, it sucks so bad up there that the low pressure would pull the people weanie right on up! How to get it back to LA or San Diego is another matter??????

[jyl]

I read a couple articles on the idea.

Without being a physicist, my questions would be:

- The whole concept requires the air in the tube to be at low pressure. Not a vacuum, but low enough to greatly reduce air resistance. Otherwise the pod will require continuous propulsion, instead of being accelerated once then getting small re-accelerations at intermediate points. I am not sure how low is "low", but I'd think we are talking 30,000 foot altitude equivalent or thereabouts. How do you maintain low pressure in a thousand miles of 20 foot diameter tube? What are the structural requirements, the energy requirements? What are the safety mechanisms: if the tube is badly holed at Bakersfield and the northbound pod approaching Bakersfield is slowed from 800 mph to 300 mph by the sea-level air pressure, does the following pod crash into it? Are passengers injured by the deceleration? If the pod keeps slowing, does it get stuck between intermediate re-acceleration stations?

- Along the same lines, the pods have compressor fans on the nose, that capture the air that would otherwise slow the pod down, compress it, send some of it to the air bearings, and some to the passenger cabin, then that air is exhausted out the back of the pod. He says this is not only feasible, but can be powered by a battery carried in the pod. Assuming that is so, suppose the compressor fan in pod #1 fails, and the pod slows from 800 mph to 300 mph, what stops pods #2, 3, 4 etc from crashing into pod #1 at 800 mph? How many compressor fans, batteries, etc do we need to have for redundancy?

- How big are the pods? The artist conceptions show a narrow capsule where people sit reclined, one behind the other, like daisy-chained F1 drivers. That is an obvious non- starter, the public won't travel like that. He has also talked about pods big enough to hold cars. Okay, that's more like it - is it practical to propel a pod big enough to hold, say, 50 people and 10 occupied cars? Because it seems the pods have hold enough people that they don't have to run too close together. At 800 mph, trying to coordinate pods that are gliding on air-bearings (so, the pod itself has no independent ability to accelerate or slow) seems tricky, too tricky to have them flying along 30 seconds apart.

- Why, exactly, does this save so much money? The articles I read suggested the tube would be elevated, so it can run through farm fields and over roads etc without expensive property acquisition, railway beds, crossing infrastructure, etc. If so, why can't a bullet train's tracks be similarly lightweight and elevated, with the same savings? I suspect the reason is that the train carries 100's of people and is massive, while the pod is small and light. But that gets to the preceding question. (By the way, this does touch on something I've never understood about the CA train - why doesn't it run down the median of Hwy 5, where the state already owns the land?)

There is a long, detailed PDF that probably answers these and more questions. I've started reading it but it is long . . .

[RWebb]

I definitely think we should stuff people into those little cylinders the bank uses for checks and money and shoot them thru a long tube with air pressure.

The only question is: which people...

[red-beard]

So, we're building the trans-Canadian pipeline and using it for transportation. In the "non-technical" section, there are serious errors. You cannot "ignore" thermal expansion. Running along the same route as a highway, say over the Grapevine, at 350 mph would still subject people to many g's as they follow the terrain and curves, or it would require very large radius curves. Think of the structure required to keep curves and assents to less than 1%.

Also, since he is suggesting that it be a closed, welded, pneumatic system, there will be no views and no visual reference.

Costs. We're talking about a pipe which needs to hold a vacuum of around 14 psi. For a reasonable size cabin, let's call it 15 feet in diameter. Using A36 steel, you'd need about .28 wall pipe for working pressure (10 safety factor). At .28 lbs per cu in, and 604.8 cu in/ft, this leads to ~532 lbs/ft of tube. 300 miles of tube (LA to SF) would require ~850,000,000 lbs of steel just for the tube. Since this will have to be rolled from steel plates, it will be a around $2 per lb in a special mill. But transporting 15' diameter tubes would be costly and impractical, a mobile rolling system would be required to roll them at the point of installation.

[jyl]

By the way, he says we shouldn't invest in new transportation infrastructure unless it is

"Safer
Faster
Lower cost
More convenient
Immune to weather
Sustainably self-powering
Resistant to Earthquakes
Not disruptive to those along the route"

Compared to other cars, the Tesla is arguably two of those (second and last).

[Hawktel]

I am not a engineer enough to know if it would work.

But I like the idea behind it. I think we should have a train that gets from LA to NY in under 4 hours including the 1/2 hour stop in Denver, and the one in Chicago.

[porwolf]

Hyperloop? Is that that idea about shooting people through an underground vacuum tube? What a hair brained idea! It ill never happen. The costs would be astronomical and the benefits minimal. Costs of safety measures will be unforseeable, if even solveable. In California a high speed train along the coast from San Diego to San Francisco, or even up to Seattle would be the sensible solution. Up to 500 miles distance travel time would beat air travel. Every other civilized country in the world has them why not us? We can spend gazillions of dollars on freeways why not on trains? Realistic trains that is.

[porwolf]

Hyperloop + 3,000 miles vacuum tube! That is supposed to work? And we cannot even keep the vacuum in our few feet of lines in the CIS system!

[red-beard]

Uh, great circle route Chicago to LA is 1744 miles which would be 5 hours with no stops. 5 hours locked in a windowless tube. If there is a stop in Denver, then you would have slowdown time, loading and unloading luggage, etc. I expect you'd be closer to 6 hours.

Also, air bearing are another word for LIFT. Lift induces drag! It will require enough lift to hold the "tube" up. So the train needs to be a very efficient lifting body. And that lift induced drag will require propulsion to keep the train going 350 mph.

The lift will be very similar to an aircraft of similar size, without the ability to do it with wings!

The more I look at this, they're building an aircraft that is running inside of a tube!

[jyl]

PDF is interesting reading.

"Passenger Hyperloop Tube
The inner diameter of the tube is optimized to be 7 ft 4 in.

Passenger Plus Vehicle Hyperloop Tube
The inner diameter of the tube is optimized to be 10 ft 10 in. (3.30 m), larger
than the passenger version to accommodate the larger capsule."

This is intended to be a very narrow vehicle indeed. Hope you don't have to pee during the journey, 'cuz you can't even get out of your seat, nor can you walk around during the 0.5 g turns. Admittedly the trip from L.A. to S.F. is only supposed to take 35 minutes, so I guess you just hold it.

"4.5.3. Capsule Stranded in Tube
A capsule becoming stranded in the Hyperloop tube is highly unlikely as the
capsule coasts the majority of the distance at high speed and so there is no
propulsion required for more than 90% of the journey.
If a capsule were somehow to become stranded, capsules ahead would
continue their journeys to the destination unaffected. Capsules behind the
stranded one would be automatically instructed to deploy their emergency
mechanical braking systems. Once all capsules behind the stranded capsule had
been safely brought to rest, capsules would drive themselves to safety using
small onboard electric motors to power deployed wheels.
All capsules would be equipped with a reserve air supply great enough to
ensure the safety of all passengers for a worst case scenario event."

Emergency mechanical braking systems sufficient to bring a capsule (pod) from 800 mph to 0 mph how quickly? Then capsules drive themselves on auxiliary wheels and reserve power to somewhere, presumably not all the way to S.F.? In the meantime air pressure in the tube is <1 psi so the capsule must be pressurized so the passengers don't die horribly, by the nose compressor, whose batteries now have to last longer than the normal 35 minute trip? Or maybe the tube is flooded w/ ambient air?

"4. An onboard water tank is used for cooling of the air.
a. Water is pumped at 0.30 lb/s (0.14 kg/s) through two intercoolers
(639 lb or 290 kg total mass of coolant).
b. The steam is stored onboard until reaching the station.
c. Water and steam tanks are changed automatically at each stop."

For each trip, 640 lb of water is converted to steam, to cool the air that gets compressed and thus heated to 1,100 F (fig 10 p 18 of the PDF). The steam is stored onboard. I think that would be about 500 m^3 of uncompressed steam. Does the capsule have a 20 meter long section devoted to the steam tank, or is the steam cooled or compressed before storage? This also makes me wonder about the energy balance in the tube. Energy is entering the tube, some gets converted to the capsule's motion, some to heat, the tube has to radiate off the heat, how hot is it in there? The calculations assume air enters the compressor at 65 F. Of course, inside the tubes is very low pressure, maybe that chills the remaining air like commercial vacuum cooling.

I think this would be cool as heck. Seems like there is a lot of comfort, safety, redundancy, etc stuff that would have to be added - a lot.

[red-beard]

7' 4", so about the size of an ERJ.

[widebody911]

Simpsons did it. I mean Futurama

[porwolf]

Originally Posted by jyl

PDF is interesting reading.

[i]"Passenger Hyperloop Tube...................
..................I think this would be cool as heck. Seems like there is a lot of comfort, safety, redundancy, etc stuff that would have to be added - a lot.

I believe it when I see it. My money is on NEVER! Elon Musk's background is only an engineering bachelor degree, good enough for a battery car. I think we have the Peter Principle working here: "Everybody tends to rise to their level of incompetence."

[TheMentat]

Originally Posted by porwolf

Elon Musk's background is only an engineering bachelor degree, good enough for a battery car.

I'm sure he relied solely on his own expertise in the design of those cars, and for that matter, PayPal, SpaceX and SolarCity!

[stealthn]

Definitely more questions than answers at this point, what about accel and decel? Maglev is still the best solution and can be incorporated with Eco crap to make it less reliant on electricity.

Just save money and put people in pigs in the existing pipelines, ala James Bond

[Pazuzu]

If you haven't read the 60 page PDF, then please do so before asking any other questions.
He has fully fleshed out the engineering behind this, I would be all at surprised if he has prototypes in his CAD programs already.

The science is sound, the engineering is sound, and the concept is sound. The only flaw is that it's not immediately expandable, but i suspect that with little work, the pylons could be designed to carry 2 or 3 stacked sets of tubes, which would increase the traffic load by that much.

[1-ev.com]

Absolutely Great Idea!!! as all his other ides, - TESLA, Space-X, PayPal, more is here Elon Musk - Wikipedia, the free encyclopedia

PLUS Hyperloop more looks like this: (PCmag on Hyperloop)


PLUS if we would spend $3,000,000,000,000 USD ( The Three Trillion Dollar War - Wikipedia, the free encyclopedia ) on Hyperloop we would be visiting cities across USA for FREE (solar panels powered Hyperloop) and we would not need so much GAS to burn while idle in the traffic, prodicing CO2

PLUS we would be OPEC nation... what a thought, HA... ---> I think I am running hi- fever of dreams, sweet dreams...

[kach22i]

Originally Posted by jyl

- How big are the pods? The artist conceptions show a narrow capsule where people sit reclined, one behind the other, like daisy-chained F1 drivers. That is an obvious non- starter, the public won't travel like that.

The G-forces at start up and deceleration are best tolerated in that position, it's form follows function.

[1-ev.com]

Everyone loves roller coaster, now it will be in the tube, that all

PLUS you might actually watching your favorite movie while riding it...