DON'T PANIC! Gee gas is only double but available
For a future engine, my thoughts are turning to gas/jet generator to power electric motor, ie series hybrid if you want to use the auto term. Anybody else have any thoughts ?
A self launched or winch launched glider? Its wind and solar powered!
Electric? Not even soon for cars. Right now electric cars are novelties and not on par with the fill'er up drive cross country of gas cars. May be 20 years for cars, but planes the weight/volume issues are greater. Hydrogen fuel cells are promising but cost, safety and infrastructure is an issue. Of course manufacturing hydrogen takes energy, electrical energy. The no free lunch rule.
In the past 100 years we used a 1/3rd of all oil, the oil that is easiest to get.
The next 3rd will be harder to get and of couse will not last 100 years at current use rates.
The last oil or related fossil energy, oil from coal, shale oil or lighter hydrocarbons (gaseous) are just more difficult to get, process and use, aka expensive, lower volume and of course higher cost.
The "other" oil, like natural gas, a gaseous fossil fuel (methane, propane, natural gas) has been used for power generation, heat and moving vehicles. Even Piper considered and tried propane plane long ago, but there are technical difficulties. The good news is there is LOTS of natural gas under the ground, even more than oil some say.
When will the proverbial shizzle hit the fan? Probably 40 years, depending on many factors, may be 60 yrs, may be less than 40 yrs. In about 60-100 yrs (when I won't care) thing will be desperate fuel wise, if technology does not have suitable substitutes for fossil fuel. Home and cars I see many alternatives: Nuke, Solar, Wind, (hydrogen) fuel cells and who knows.
Planes? That is a different story, high energy density. Currently electric is not going to happen practically or large scale for plane due to battery technology. Can you imagine an electrical engine making 20,000 to 90,000 lbs of thrust a typical commercial jet engine produces. Even making 100 hp for extended periods is not likely to be practical anytime soon, may be ever?
100LL (really 95UL is the future) will be avaiable through out our life and our kids (may be), its just a matter of cost. Don't panic. A RV flown prudently can get into the 30 mpg, easily 25 mpg. Not super when compared to a super econ-O-box car but not far off. An sub compact car of course does not do the better part of 200 mph.
Bottom line our hobby just got way more expensive. Gas will be avaiable, just a matter of if you can afford it. Really we'll be looking back on the $100/barrel days as the GOOD OL DAYS. Actually its already at $120/barrel. So the good ol days was just last month.