My idea on the first 600-1000 MPH train

Nasadowsk wrote:Oh - Mr Toy - Thrust reversal on jetliners actually plays a very minor role in stopping - the FAA's certiication testing doesn't allow the use of it in calculating stopping distances. Rather, it is in fact done primarilly by wheel braking.

I stand corrected. I was basing my coment on the experience of feeling the braking when reverse thrust is applied. It didn't occur to me that brakes were playing the main role, though I was aware that brakes had some role. Learn something new every day, and be smarter tomorrow.

Braking is highly ineffective until the aircraft slows down considerably and lift decreases accordingly, adding weight to the landing gear tires. The slowing until brakes become effective later in the landing roll results from the aerodynamic drag of moving though the air. Drag is intentionally increased by using wing flaps and spoilers.

Bensalemrider, please ditch the catenary idea. On SEPTA I've had catenary land on our car once @ Melrose Park. We were going 70. Go ten times that and you'll have catenaries ripping to shreds before they land on the car. not to mention expensive installation.

now I would declare solar an option as an alternative, but the darn thing would be moving through the daylight too fast to pick up any rays!

As early as the 1960's, or even earlier, science fiction literature postulated a pneumatic tube between NYC and SF. The capsule/trains would "fall" into a downward sloping tunnel, assisted by high speed airflow, and reach speeds of 1,000 mph or so. (No supersonic shockwaves as the internal tunnel flow would be at that speed.)

If anything is ever constructed, the pnematic concept is probably the most feasible.

Loads of problems with this idea:

1) Wheels couldn't remain balanced precisely enough in commercial service to be run at those speeds. Even a slight imbalance would literally shake the train apart.

2) The track couldn't be kept in precise enough alignment. If the train didn't derail, at the very least the ride would be horrible.

3) Electrical pickup from catenary at those speeds would probably be impossible.

4) The amount of power needed to travel at even 600 mph at ground level would be prohibitive. A shortened TGV required 13,000 MW (17425 HP) to reach its record speed of 515.3 km/hr. A regular size train going 600 mph would require well in excess of 100,000 HP. Even if it was economically viable given this kind of energy usage, you would need a catenary voltage of >100 KV to keep the current within limits.

5) Sonic booms

6) Suction pulling people and animals onto the ROW.

7) Hitting a bird at those speeds would be problematic, and the train couldn't be made strong enough to withstand bird strike because high speeds require lighter weights

8) Wheel-rail adhesion decreases as speeds increase. In fact, they decrease so much even at 360 km/hr that any proposed 360 to 400 km/hr trains must have all wheels driven in order to be able to reach their design speeds. 600 mph in the open air via driven wheels is simply not possible, let alone 1000 mph.

9) Stopping is a big problem. Assuming that the train could decelerate at 2 mph/sec, it would require 25 miles and 5 minutes to stop. This would severely impact line capacity making the project less economically viable.

Now, there are ways to go this fast or faster, but first you need to get rid of the wheel-rail interface. That means maglev. Second, you need to get your power via inductive pickup. Third, you need to run in an evacuated guideway. In fact, for any speed much over 300 mph an evacuated guideway should be seriously considered. Once you get into the 400+ mph realm it's more or less mandatory to bring power requirements down. I'll even go so far as to say that maglev in general, unless it's a short-distance, low-speed commuter route where maglev was chosen for its superior acceleration, should be run in an evacuated guideway. After all, if you're going to go through the trouble to build a whole new ROW, you might as well put it in a tube and as a bonus you get to go as fast as you want. Acceleration rate is actually the main controlling factor once you go the vacuum-tube route. The faster you can accelerate, the faster the trip will be. Comfort limits for seated passengers are typically 0.25g. This will get you to/from 1000 mph in 182 seconds/25.3 miles, and on to, say, 5000 mph in about 15 minutes and ~630 miles. Yes, speeds like that are seriously being contemplated for the transcontinental/transoceanic lines being proposed and likely built once we run out of oil for airplanes. Figure by 2050 or so you'll be able to go from NYC to London in less time than it takes now to get a taxi to the airport.

A number of posters spoke of various limitations for such speed, and they are all mostly valid. I add also the ergodynamic effects on the passengers. How many people would want to be harnessed in like space shuttle astronauts. Of course once the space shuttle is in orbit there is the weightless condition and the passengers' bodies travel at the speeds within the spacecraft, but it is the acceleration and deceleration to reach and stop from these speeds that are the problem.

I do not know what the limit of an average person's g-force tolerance in seated strapped-in condition, but for ordinary standing passengers in public transportation vehicles it's about 10% of the acceleration due to gravity (based on the research done for the PCC trolley car development in the 1930's, and the human species has not evolved THAT much over about 70 years). Granted that such a high speed vehicle would not permit passengers to be standing during the speed-up and braking process, but say that the human limit for this might be considered as a full gravitational acceleration for being strapped-in and properly contoured with custom fit for each passenger to avoid neck/spinal injuries, this aceleration of 32 ft/sec/sec (which would amount to freefall off a cliff, where it is known that many people in that kind of free-fall die before they hit the ground) for about half a minute giving a distance of about 2.25 miles to get to a speed of 600mph. Can your body take it even if perfectly suppported? And to reach a speed of 1000mph would take about 45 seconds and about 6.4 miles to reach.

Say, though for a more optimistic outlook, that the seated passenger can tolerate the g-forces only to the extent of double the standing passenger stability acceleration, to reach a speed of 600 mph requires 2.2 minutes over a distance of 11.44 miles, and to reach a speed of 1000 mph requires 3.7 minutes over a distance of 31.13 miles.

Just from my own personal experience traveling on buses at the radii and speed bus drivers like to travel, by calculating the radii and speed of the bus the lateral acceleration can be determined, and that would essentially also cover braking and speeding up horizontal accelerations as well. My personal experience is that even seated, not standing at 10% of gravitational acceleration, one is already "bounced around" in one's seat more than one should at considerably less than 20% of gravitational acceleration, so the accelerative / decelerative peformance of any public transport vehicle is limited to the ergodynamic tolerance of the average passenger, certainly not the astronauts as a model to design a high speed public transport system for. This limitation may be more critical than the track infrastructure or vehicle technology itself, and depending on the frequency of stops, may result in an unviable overall system, given the acceleration / deceleration characteristic requirements for this factor.

Just one more issue to consider!

Sincerely,
Vytautas B. Radzivanas
Perth, Western Australia

CRail wrote:tgv's record high is 260. 600-1000 is way out of range.

the TGV went over 300 i think, but that was a 3 car train down a hill. there are pics and info on trainweb.

It is perfectly
im-
possible.
Besides practicepro's point of the sonic boom:
Catenary / pantograph system that would allow for that speed (and I'm talking of your 'low' value) has yet to be developed - modern catenary system would be whipped up fantastically. Why use batteries? That's just one mystery about this idea, but since there are to be magnetic stainless steel rails anyways...
The point about fast running - talking of 120 - 200 mph - on rails is by far not derailment but keeping a smooth tracking of bogies with practically no flange contact at rails - and that includes wide high speed curves, too (on the TGV when a definite flange contact incidentally happens at speed you'll hear it as a shrill 'zying!' noice). Among many well interacting refinements in bogie design, a well tuned interaction of vertical and horizontal chassis suspension and dampening, as well as high precission construction and maintenances of all components, running these speeds in daily traffic demands trackage of absolute billiard table smoothness and trueness.
If you were at a point where you had to be concerned about derailment this would make quite a rocking journey, totally inacceptable in view of safety, comfort, maintenance, economy.
There is a speed range beyond which the classic rail / wheel system is just not adequate anymore and it would be preferable to go for linear motor rail system. It is only because there already exists a rail system that it has been preferred to build those super-high-speed trains within the existing technical system so that it is kept compact instead of having two incompatible systems at the same time. The speeds now attained in regular service by high speed electric motor coach trains in Japan and in Europe are already stretching the system's suitability, I don't think there will be much further margin for even higher speeds as concerns economic service.
Juniatha

A sonic boom, which the concordes weren't allowed to make 30,000 feet above land, would disallow service above the speed of sound (somewhere around 700 mph).

Not to mention, commercial airplanes don't go above 600, which makes the idea of a train doing that speed inconcievable.

And I'd doubt you'd find a person or government who would fund this.


In the year 5,000 maybe, anytime sooner? Leave it for the Jetsons.

Ken W2KB wrote:As early as the 1960's, or even earlier, science fiction literature postulated a pneumatic tube between NYC and SF. The capsule/trains would "fall" into a downward sloping tunnel, assisted by high speed airflow, and reach speeds of 1,000 mph or so. (No supersonic shockwaves as the internal tunnel flow would be at that speed.)

If anything is ever constructed, the pnematic concept is probably the most feasible.

What could be called the 21st century variant of those pneumatic tube concepts would be the similar concepts for a maglev operated in a partially evacuated vacuum tube. These vehicles would be familiar to anyone who saw the Extreme Engineering show on Discovery featuring the extremely far fetched (and poorly thought out) Trans-Atlantic Tunnel. That show proposed maglevs moving through a floated tunnel at upwards of 1000mph between New York and London. There also was a plan in Switzerland for a series of vacuum maglevs linking the major cities both within Switzerland and potentially in adjacent countries. In so mountainous a country, where any true high speed line is bound to involve a very high proportion of tunnel construction it really does make some sense to make the line fully underground and remove the air from those tunnels to achieve speeds which a surface line would not be capable of. The system was to be called SwissMetro, but it'd seem that despite some testing, the plan has been downgraded and is highly unlikely to be started anytime soon. Certainly the website has lost much of its former glory, and the wikipedia article on the subject makes clear that little will be done in the future on the matter.

If we ever come to a point where it's much more efficient for long distance transportation to use a ground based, perhaps alternative fueled, powerplant than a fossil fuel airborne powerplant then it might make sense to invest in a national vacuum maglev system. With a system providing speeds upwards of 600mph with less friction and a cheaper, domestically produced power source it'd certainly have distinct advantages over airliners, but with a massive cost up front. When compared with an above ground train the problems of a sonic boom, track/rail interface and the propensity for for derailments at such high speeds, birdstrikes and other FOD suction, and other problems are mitigated, as jtr1962 noted. As he also said an inductive pickup would certainly be needed, as a pantograph or shoe would simply break off at the slightest kink in the power supply rail or wire. When compared to the non-maglev pneumatic tube of the 1960s the friction which an airtight seal would require would be unnecessary, and most of the tubes coud have their vacuum maintained, eliminating the inefficient cycling of air a pnuematically driven vehicle would require.

Maybe some day when automation reduces the cost of tunnel construction and fuel costs reach an excessive amount we'll finally reach the point where it makes sense to build tunnels for very high speed ground transportation. However I don't put much faith in this. Oil prices are significantly higher than they were just 5 years ago and they've long since passed points which were previously forecast to trigger reductions in consumption with no action being taken on our part. If we haven't made a significant effort to build TGV or ICE-like HSRs to connect cities like San Fran and LA, or Dallas, Houston, and San Antonio, at 25 to 50 million dollars a mile, with the current oil price problems it'd have to go extremely high for a 100+ million dollar a mile SwissMetro-like tunnel vacuum maglev to make economic sense.

Hmmm maybe they can tack it on to the Big Dig