In case you had not considered it, Energy is one of the most important flows for a human civilization. Indeed, it is wise to work on the most efficient generation and distribution methods with the least impact. The US Department of Energy (DOE) is one of the most important agencies in our Nation, and how we handle our energy needs, conservation and technologies will affect our economy, environment and the stability of the Country itself.
In days gone by, we used steam engines for transportation. Trains and even the first cars, in fact most of the early industry used steam engines to create the power to do work. Yes, steam engines were problematic, but back then, it is all we had and it worked. Well, it worked as best as it could considering the technology of the day. Could we re-design the steam engine with modern materials and technology to forego our addiction to foreign oil" asked Robert, who recently inquired about such a concept at the Online Think Tank. The answer; Sure, we could.

In fact, but I suspect with sound frequency bombardment, carbon nano-tubes and maybe helium gas, instead of water, we might be able to borrow some of that old technology back again someday and put it to very good use. Old steam engines were made with iron, today we have much lighter materials. We still use steam today for some things.
Geo-Thermal potential in the US is not being used properly, and probably worth about 5-6% of our total usage, if we were to go for it. Many of these geo-thermal units run off steam technologies, yes, far superior to the old stuff. As far as energy goes, I kind of like Nuclear, Ocean Wave Energy (and Hydro) and look forward to clean coal technology, hydrogen cells (when new materials come available cheap) and solar as our increases in efficiency are making strides now, so the ROI is getting there to compete.

Steam is a powerful source of energy, and it develops quite a lot of force. There was a Steam Driven Aircraft, a couple actually; all in museums now. Today we have the technology to make Nuclear Aircraft, steam driven, talk about performance, they could stay in the air "forever" and never land if we did not need to repair them - kind of interesting, perpetual airplane.
Sure we could easily build upon the steam model, even totally re-design it. Robert asks if we can make an automobile with a steam engine, use the same body, only it could run off steam. Yes, we can do that, one issue is that it would make advection fog, which could cause issues in colder climates - massive car pile ups might ensue. That problem could be solved however.

With a modern day steam engine, you would not have to build the steam engine out of Iron any more, you could use lightweight materials now, totally change everything. If the system was enclosed it would not make vapor trails, sure we could make steam cars, no problem. It does take a lot of energy to heat water, but who says you have to do it by fire? You could excite the molecules in another way. Why do I like Robert's idea? Well, I live here:
http://www.carwashguys.com/blitz.html
So needless to say, the fuel prices are not very funny for me and it is dragging our economy. The cost of energy affects everyone, it is a real issue and we really need to consider all the possibilities as we move into the future.
Energy is the key to a strong civilization, and it is paramount that we take care of these challenges. Lance