Sunday, May 20, 2012

Will Future Aircraft be Fueled by Natural Gas?

   If you could really make more economical vehicles, what would you do in order to maximize the impact on our society?  One approach would be to use such technology in an ultra-ultra economy car, such as the so-called Smart Car. It would be one thing if you could get people to trade in their Hummers for such a car, but if you are going to compete against Honda Civics and other traditional subcompacts, it's not going to really be all that much cheaper, in my opinion.  The cost of gasoline is going to be about the same per mile driven, and in fact these cars are not going to be driven much anyway. 

How much of an economic impact will tiny economy cars have?  Some, but not very much.  

   If you were really going to make a serious economic impact, you would probably try to use your more economical technology (whatever it is) on vehicles that really consume a lot of energy, such as taxicabs , delivery trucks, fleet vehicles, city buses, locomotives and even aircraft. These vehicles are used for tens if not hundreds of thousands of miles per year, and so if you really have a way to save money, this is where the big bucks are to be found.  

   In that regard, I was interested to see the Boeing is designing an aircraft that would use liquefied natural gas (LNG) in place of jet fuel. Published articles are focused on a very advanced concept in which the LNG would actually be frozen.  That offers the highest performance, but even using today's technology (cryogenic liquids), using LNG in aviation should be a no-brainer.  LNG has more energy per unit weight than gasoline (54 MJ/kg versus about 44 MJ/kg for current aviation fuel).  This extra bang per unit weight means that planes are going to weigh less and travel farther and faster than they can today. Plus natural gas combustion emits less carbon than current jet fuel, it's cleaner than petroleum, and it is about half the cost compared to  aviation fuel. 

    Plus, if you want to continue to rely on petroleum fuel, you have to buy it from countries run by idiots, who like threatening the US with nuclear warfare among other things.  What a great idea that is!
   Nevertheless, a great number of Americans believe economic growth is bad for the economy, and moreover they are very comfortable with an occasional ten-year war in the Middle East.  On that basis, there will no doubt be considerable opposition to switching to LNG fuels, as we continue our policy of supporting corrupt foreign despots whenever possible.  Nevertheless, my guess is that common sense will prevail,and thus it will probably happen sooner rather than later. 

If the world starts using liquefied natural gas for aircraft, it's going to be cheaper and faster to fly. 

Post Script

For what it's worth, the modifications needed to run a turbine on natural gas instead of liquid jet fuel are relatively simple, and in fact in the 1990's the Soviet Union built a modified Tupolev 155 jet aircraft that ran on natural gas.  So don't even try to say that it can't be done.  It can be done, and it is a straightforward conversion. 

The use of natural gas for a jet aircraft was successfully demonstrated on a Tupolev 155.

For additional reading:

Andrew Webster, Boeing's SUGAR Freeze plane concept runs on cryogenically frozen natural Gas, The Verge, Mar 21, 2012,

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