What would a steam locomotive look like if steam power became yet again the main type used in rail transportation?

Question

Assume in the very near future almost all rail transportation would return to steam-powered locomotives. To define it exactly, I mean solid fuel is burned inside the locomotive, which boils water, which is in turn used to drive the locomotive.

Assume no economic or societal collapse, or at least not a too large one. Also assume that the importance of rail transport versus road transport increases to the levels it was 70-90 years ago. Technology should be the same as we have now.

Steam locomotives are not very efficient, but there might be some causes in their re-emergence. For example, rising oil prices would make road travel uneconomical for goods and only affordable for personal travel to the wealthy, just like it was 70-90 years ago. Or some regulations would be the cause of this. Whatever the reason, steam locomotives are coming back.

(I know that this would explain the reduction in diesel locomotives, but not electrical ones, which can be powered by wind/solar/nuclear power. Maybe something like a new plant which grows fast, easy to harvest, and burns well, perfect for steam locomotives but not economical for power plants? I know, getting rid of electrified rail would not be easy, this might require some suspension of disbelief. But somehow, they are either gone, or reduced to niche roles)

Now, steam locomotives are back, while technology is roughly the current one. What would they look like?

Steam locomotives, especially 20th century ones, are real marvels of engineering, more than 100 years of development led them to be much faster and more efficient than when they were first invented. This knowledge is not lost to us, so we don't have to start from scratch. Many old steam locomotives still exist in functional states with people able to maintain and operate them, either for tourism, or in reserve for emergencies. So, putting the 1930-1940's steam locomotives (the last time significant development was done in this regard) back in production should not be that difficult. But how could we improve them?

One significant change (but invisible from the outside), I guess, would be the computerization of the controls, to make them simpler to operate. Driving a steam locomotive was a very difficult job, and required great wisdom. It's no wonder the word "engineer" originally meant a train driver. Even the job of the person shoveling coal required a lot of knowledge and experience, keeping track of steam pressure, temperature, humidity, the color of the smoke, to know when to shovel fuel and when to release pressure, etc. Everything was done manually, so some improvement could be done there.

What else? Fuel efficiency? What could we do now what they couldn't do 70 years ago? Computer simulations to make a better shape for the boiler to improve efficiency a little? Better steel technology to resist higher pressures? Better filters to not produce that much smoke?

What would visibly change as steam locomotives would be kept improving from where they were left 70 years ago? Steam turbines are more efficient then traditional steam engines, every power plant, including nuclear ones, use highly sophisticated steam turbines. However, they tried it for locomotives, and it was not very successful.

Answer 1

• Most steam engines would use condensers, both to avoid watering stops and to use the thermal energy to pre-heat the feed water.
• Many steam engines would use modern gearing rather than pistons and rods directly coupled to the wheels. This allows the pistons to turn at the optimal speed for power generation and not at the necessary speed to turn the wheels. That would mean driving wheels can get smaller, too, no more need for the outsize wheels of old locomotives.
• Some of them might use steam turbine technology.
• You might see steam-electric engines where the steam engine drives a generator and that generator powers electric motors.
• Technology might be developed to replace the stoker who hauls chunks of coal with a pipeline to transport coal dust.

Answer 2

It will not happen

You asked:

What could we do now what they couldn't do 70 years ago?

Answer: they could not create an electrified railway for locomotives to use instead of lugging all their fuel around.

When it comes to generating power, there is significant economy in scale and centralization. If diesel-electric engines become nonviable, this will not bring back steam engines. It will instead lead to a boom in electrical engines. The power you wish to generate on-board the train will not be done so, but instead at a power plant. As far as economics, efficiency and logistics are concerned, this is the best way to go, if nothing else because it means we can use already existing technology instead of having to re-invent the steam engine in the 21st century.

Also there is no more efficient way to distributing energy than as electricity. Lugging coal and water — or any other steam forming agent around — is horrendously tiresome.

If you are hellbent on creating steam engines again, they will not be the stereotypical puffing chugga-chugga-chugga kind that we are used to, but instead just versions of the diesel-electric kind, where the steam engine drives a generator that in turn drives electrical motors on the wheels. So they will be quite boring looking, and not the stylish art deco machines of the 1920s to 1940s.

I am sorry, but since you asked for "hard science" I am forced to give you a boring answer.

Answer 3

From a purely aesthetic point of view, I hope they come back as art deco beauties

An example of this is PRR-S1

Also, you could make them NUCLEAR! Using RTG's like in satellites, no pollution at all! With a continuous heat source, you have no coal man or fuel to transport, just a lot of water.

Answer 4

Steam engines went out of fashion because they have significant issues compared to diesel electric engines.

1. The power to weight ratio is rather low
2. Steam engines can take up to 10 hours to raise steam from a cold start
3. The weight of water,fuel etc. is far greater than the corresponding weight of diesel fuel
4. Steam engines are relatively complex machines with significant safety issues from the use of live steam and a pressurized boiler.

So to bring back a steam engine, we would have to find ways to overcome these issues. Some of the issues could actually be resolved through the use of supercritical CO2 as the medium of energy transfer other than water. The higher density allows far less fluid to be used, the energy efficiency is much higher and since there is a smaller amount of fluid in the system, the "raise steam" time would be much reduced. Experiments using supercritical CO2 rather than steam in thermal power plants suggest that a turbine and the associated plumbing could be 1/10 the size of the equivalent steam turbine.

https://inldigitallibrary.inl.gov/sti/2906955.pdf

http://energy.sandia.gov/energy/renewable-energy/supercritical-co2/

http://www.co2turbine.com

The obvious result would be the space devoted to the "engine" would be far smaller, and since this is a closed cycle turbine system, the resulting engine would be smaller and lighter as well. This would be offset somewhat by the need for large radiators, and of course the issue of highly pressurized working fluid hasn't been eliminated either.

Direct drive from the turbine to the drive wheels isn't the best solution (the reduction gear case would offset much of the size and weight advantages of using a supercritical CO2 turbine), so the turbine would be powering a high speed generator. A steam-electric serial drive would operate in a similar fashion to current diesel electric engines. Because you are using a turbine, this potentially allows you to produce the same energy output from one locomotive as several diesel electric locomotives. This could be tapped by providing powered bogies on the railcars themselves, allowing for distributed power along the length of the train and potentially providing more traction for starts, stops, moving up steep grades and so on.

The other advantage for the railway company is they would only need one locomotive per train which would be an especially useful cost saving when running large and heavy unit trains

Answer 5

If you look at a late-era steam locomotive like the Mallard, I think there are real similarities to more modern trains, e.g.:

I would expect train manufactuers to continue to design streamlined locomotives that both have good aerodynamic properties and evoke ideas of speed and modernism.

They probably wouldn't be white because white stuff gets dirty around coal. Dark colours are more likely.

I would expect the driver to be at the front because (a) most of the business of fueling the train would be handled by automated machines, (b) the controls would be electronic rather than mechanical and could be operated from a remote cabin, and (c) the front offers better forward visibility and safety.

The coal tender would be covered rather than open for various reasons. Firstly, it would again help the locomotive to look more modern and streamlined. Secondly, there may be some modular solution for more efficient refueling (rather than just 'pouring coal in from the top'). Thirdly, refinements in fuel chemistry and the technology that transports the fuel into the firebox mean that we need to protect the fuel from the elements.

For long-distance trains, there may be solutions for storing fuel above/below the carriages and then automatically transporting it forward to the ending as needed.

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Having said all that, here is some cool art called "Heavy Metal Hero" by Rodney Matthews:

This art was also used on the cover of an old videogame called Transarctica, set in a post-apocolyptic frozen world where people live on trains that roam the landscape looking for supplies.

Answer 6

Steam power would be steam-electric

Diesel trains don't run diesel engines coupled to gearboxes coupled to the wheels. Modern ones will use a diesel to power a generator to power a VVVF (Variable-voltage, variable-frequency) drive unit. The electric generator and motor act as the transmission. This is more efficient today; if you change the prime mover, the generator/drive combination is unaffected and will still be more effective (namely, lighter) than a gearbox mechanical transmission.

For electric generation, a turbine is best

Since you are now connected to an electric generator, the most stable and efficient way to operate one of those is with a constant speed turbine. What do you know, the same technology setup is still used on to the modern day in steam powerplants on warships. The Nimitz aircraft carrier runs (many) 8,000 kW steam turbines, a locomotive might be more like 2,000 kW.

Does it really have to be steam?

You know, if you are going to run a turbine-electric system on a train, why not make it a gas turbine? This is basically a jet engine; instead of putting steam in to power the turbine, you put gasoline in and light it on fire. The power to weight ratio of those things are off the charts (compared to both diesel and steam), and the turbine output is basically the same as from a steam turbine.

Answer 7

The other commenters have done a good job pointing out what might change with the braking and mechanical control systems of a modern steam locomotive would be, as well as the engineering reasons steam lost favor to begin with. However in the the middle of the 20th century French, Argentinean, and British engineers worked hard to radically improve the performance of steam locomotives. Some of the last results looked like this:

It's close to what I imagined when I saw your post, as this is the world building stack exchange after all. The main innovation beyond aesthetics is the thermodynamics of the boiler and fuel feed system. It requires a some basic thermo knowledge to appreciate, but is detailed very well here: https://csrail.org/modern-steam

A fully report on the sleek train pictured is here: https://static1.squarespace.com/static/55e5ef3fe4b0d3b9ddaa5954/t/55e637bee4b0bef289260255/1441150910433/%23+DOMS-2_PORTA_Argentina.pdf

Almost everything you are looking for is linked to from this wikipedia page from a prototype steam locomotive designed in the 1990s.https://en.wikipedia.org/wiki/5AT_Advanced_Technology_Steam_Locomotive

Engineers continue to refurbish and build new steam locomotives today, but most are straightforward rebuilds of midcentury models with the most minimal changes to make them meet safety parameters. They retain the same essentially "non-modern" body you'd imagine.

Answer 8

Why does it have to run on solid fuel? Fluids are easier to handle. Steam locomotives have traditionally run on poor quality oil. Recent examples are tho new and converted locomotives from DLM which run on light oil or diesel fuel. However, steam locomotives might use biowaste such as wood chippings or agricultural waste such as straw, though the energy density per unit volume is very low.

Apart from that, there is no reason why they should look much different from the locomotives of the late 1940s. It would be desirable if they could run equally well in either direction, which is primarily a matter of the design of the cab and fuel-and-water-carrying vehicle. Very large freight locomotives would, with advantage, follow the Beyer-Garrett configuration.

The great advantage of the conventional steam locomotive is that it is simple, with a relatively small number of components, of which the wearing parts can be designed for easy replacement. Also, in the railway environment, the boiler acts as an energy reservoir, providing a "buffer" between conversion of the chemical energy of the fuel into the potential energy in the steam, and thence to mechanical energy via the direct drive.

Boiler wear can be substantially reduced by using liquid fuel and effective water treatment at very high pH, and by keeping the machines permanently warm to avoid heating/cooling cycles. External combustion enables the locomotives to be designed so as to minimise the production of harmful wastes such as carbon monoxide, NOx and particulates.

The long preparation times referred to by some of the above commentators can be eliminated by internal or external pre-heating systems using oil, gas or off-peak electricity.

In my view, it is time that this technology made a comeback at least on secondary routes where the density of traffic did not justify the capital costs of electrification.

Overall thermal efficiency these days is about 12% which is not very good, but waste heat can be used for heating the train. It is worth remembering that the most powerful locomotives in Britain are the class 68 diesel and the Duke of Gloucester, the last British Railways steam design.

Answer 9

I'd wager a modern steamer would look something like this, maybe with an added streamlining shroud and bigger. Mainly because high pressure engines were found to be efficient and very successful, but were still premature during the steam era. When high pressure boilers were more perfected, the steam age had long died, and this prototype of mass potential never came to fruition.

Answer 10

There are 38 new steam locomotives currently under construction in the UK designed to be fired by a range of fuels from solids, liquids and even gas, all of which follow traditional 1930's and 40's configuration and layout. The largest and most powerful of these, the P2, is expected to be capable of producing 3000hp at 80% and 100mph. It's worth noting that during WWII Switzerland, finding it's self cut off from German coal supplies and with a surplus of hydro-electric power it could no longer sell to Germany, converted existing steam locomotives to use immersion heaters supplied via pantographs fitted to the footplate roof. The main problems I can see with steam over electric is power and speed. Steam tops out at a power of around 4000hp for a practical size of locomotive compared with a similar size electric locomotive able to produce 10,000hp. The UK's Tornado steam locomotive built in 2009 has managed 116mph flat out, 109mph slower than the designed top speed of the electric high speed trains using the the same line

Answer 11

Steam describes the medium for translating heat energy into mechanical energy. Nuclear power is often actually steam turbines heated by fissionable material. We'd probably call it a nuclear or atomic train, but it is still a steam engine.