|Musings on Tube Transport||Man in a Shed Biography||Tube Transport Problems||Tube Transport: my concept||The Hyperloop: my thoughts|
I have long been fascinated with the concept of Tube Transport as I termed it - or Hyperloop to use the recent buzz-word created by billionaire innovator Elon Musk. Nearly thirty years ago I was driving along a motorway, dwelling on the tonnes of fuel fumes poisoning the air and thinking there must be a better system of transportation. My engineering training (see Andy Marks Bio) wondered what if ...... you simply move the air from the front of the vehicle to the back. Better yet, enclose the vehicle within a sealed tube ..... and so Tube Transport became a concept which would tax my imagination over the decades. The benefits are enormous over the ludicrously wasteful internal - and external - combustion engines. I hope that a man with the abilities and resources of Elon Musk supports this concept and may actually make it happen in the near future.
Look at any terrestrial vehicle, airplane, ship, train or car. What inhibits their movement? Two things namely, inertia and drag. So you build your vehicle with as little inertia as possible, that is with a minimum mass; and with a low resistance to the surrounding fluids of air or water, and so decrease the drag. Currently, the latter is usually achieved by using a minimal frontal profile and a sleek streamlined body. So, take away the fluid from the front of the vehicle and put it behind. Now you have no resistance in front, just pressure from behind and your vehicle moves forward. To make it even more efficient, put the vehicle in a tube so the low pressure stays in front and the high stays at the back.
The concept of tube transport is not new. Exactly 150 years ago the British Post Office inaugurated a pneumatic railway using cast-iron tubes and trucks to convey mail bags between sorting offices in tunnels beneath London. The trucks were pushed and pulled using air pressure, had rubber seals, weighed up to 3 tonnes full of mail, and initially ran at 40 mph. When the system was retired eleven years later in 1874 for being too slow, the trucks themselves were averaging 60 mph. The absence of an accurate and fast control system was the main reason for delays.
So, after a century and a half of technical developments we can now do the job properly. We can envisage a tube five feet across with a cylindrical pod to travel inside it which could carry up to four people and their luggage. This pod is light has no engine, transmission, fuel, suspension or even wheels. Wheels are not only redundant but a liability at over six hundred miles an hour. Seats alone are needed with a few comfort factors to keep the travellers entertained. The only other major pod components are two seals, one at the front and another identical seal at the back of the pod. A "U" section made of glass filled PTFE seals the pod and slides along the tube, which is also lined with PTFE, giving an ultra-low resistance to movement. The profile of the seals will in themselves create suspension to insulate the pod's occupants from minor tube distortions.
A brief digression into specifics. A tube of say 60 inches, 1.5 metres, diameter has a cross sectional area of 2,827 square inches. At an air pressure of just 1 pound per square inch (psi) the pressure on the back of a pod in this tube is 2,827 lb !! So the forward thrust from behind the pod is a tonne and a quarter and the resistance in front is err... nothing. At atmospheric pressure the thrust would be eighteen and a half tonnes!
So for short distances, a low pressure in front and a high in the rear is just fine. But for longer trips, and for multiple pods, more sophistication is needed, in the form of valves in the tube. These will ensure low pressure is constantly in front of a pod and high behind it. These valves will be simple but effective and fail-safe, pneumatically operated and computer controlled. High and low pressure air mains will run parallel with the pod tube with valves linking to it. As with flight controls on aircraft, all valves will have two further back-up systems - all three being constantly monitored and the components easily accessible for maintenance and replacement from the outside of the tube. Two tubes will run side by side, one for each direction.
The pod has virtually no moving parts, and will spend the whole of its very long life in a temperature and humidity controlled atmosphere. It won't rust, corrode or even get dusty. It won't collide with other pods, pedestrians, trees, animals or insects; or emit hot burnt chemical pollutants. It won't be delayed or affected by weather or seasons. The tubes, being light and compact, will be relatively cheap, easy and fast to install and maintain, but will need to be fairly straight.
To travel directly across the country a network of tubes will be needed. One problematic part of Tube Transport systems will be the intersections, in railway terms the points or switches, which is a subject I have pondered for over a decade and believe I have found a neat solution. This has to be a three dimensional design rather than just the two as for rail junctions, and with the necessity for absolute safety whilst traversing in either direction - but I leave this subject for the moment in these musings (further details here).
Many old designs and concepts can be revisited and made successful by using modern technical innovations, electronics and material advances. The Hyperloop and Tube Transport in general are overdue updates of a Victorian design which will cut to a fraction the amount of energy and materials consumed in moving items and people from one place to another and will do so at several orders of magnitude faster than is currently achieved. Vested interests in maintaining the status quo will be the principal problem to overcome but with a man like Elon Musk at the forefront the light may yet be at the end of the tunnel .... or should that be, at the end of the Tube!
Text © Andy Marks 'A Man in A Shed'
Photos published under Creative Commons License/ M Peel
Andy is also a partner in Skyscan a British aerial photography company.