Personal Flying Machines

Up to: What futures do we want?

During World War II, journalists, when otherwise unoccupied, would speculate about the ``post-war world''. Unlike present journalistic speculations with similar titles, theirs were generally optimistic, and one of the themes was that certain new inventions would make our lives more comfortable. One such speculation was that helicopters would become as common as cars and be used instead of cars. Forty years have passed, and this still hasn't come about. Why didn't it happen? Is it impossible or can it still happen? What is required? Whose fault it it anyway?

To begin with, what good would be a personal flying machine that could be used like a car, i.e. kept at home and flown to work or to the store? To many people, myself included, it seems obvious, but there are many skeptics and negative thinkers, so it's worthwhile spelling it out. Here are some advantages:

1. If the flying machine was reasonably fast, the comfortable commuting range would be much larger. More people could live where they want, and husbands and wives would be more independent of each other in the job market.

2. Intrinsically there is plenty of room in the sky. With accurate enough electronic control, there wouldn't be traffic jams.

3. Less land would be occupied by highways and there would be less expense in building them.

4. Flying is fun.

5. Islands will become much more habitable when flying machines become an important form of personal transportation. The advent of cars, trucks and buses made land transportation more convenient and water transportation suffered by comparision.

The WWII idea was good, but the speculations were naive. With 1990s technology, the dream may be technically and economically realizable, but it may require innovations in the social mechanisms for supporting technology in order to get the development done. It may require the reversal of some recent innovations in technology assassination in order that it be allowed to happen.

To begin with, what's wrong with helicopters.

1. They are expensive. A reasonable four place helicopter with instrumentation costs $250,000 and $150,000 per year to maintain. (These figures are guesses and to be replaced by current figures). This is not the decisive problem, because there are a substantial number of rich people who can afford that and who pay much more for private jets. If this were the only problem the rich would lead the rest of us into the helicopter world just as they led us into the automotive world.

2. Helicopters are too dangerous unless operating restrictions are imposed that seriously impair their usefulness. For a long time helicopters were regularly used from roof tops, but this practice has mostly been replaced by helipads in parking lots. My impression is that occasional unpredictable wind gusts caused too many accidents. Also helicopters have only recently been able to fly in instrument weather, e.g. through overcasts. They can do this only at similar altitudes to those used by airplanes. Indeed it may be that the only person in the world who commutes anywhere regularly using a helicopter is the President of the United States. Even he can't go to the store by helicopter. For him to go to Camp David requires several hours notice.

3. They require too much skill to fly them safely, and a lot of willingness to cancel trips if the weather appears doubtful.

4. They are too noisy. Many cities, e.g. Palo Alto, CA, forbid landings except at airports, hospitals and a few other designated places.

5. They have poor public acceptance. There has always been a problem of public acceptance of any new annoyance except by phenomena in whose benefits the public already shares. Remember the proposed British laws of the 1890s about there having to be a man carrying a flag walking in front of automobiles. The anti-technological attitudes widely prevalent among intellectuals combined with equalitarianism and litigiousness will be difficult to overcome.

Here are some ideas about how the problems can be solved. Helicopters are still a possibility but not the only one.

1. We don't propose anything special concerning cost. If a large market among the rich develops, competition and automation will bring the cost down to a level the middle class can afford.

2. Personal flying machines must be entirely automatically flown. This is independent of whether there is a big automatic traffic control system or whether each machine avoids the others with its own detection and computation apparatus. Anyone who treats an airplane --- let alone a helicopter --- like an automobile is asking for a short life. We humans just aren't reliable enough. Airliners which fly fixed routes require at least two professional pilots to achieve sufficient safety. Getting sufficient reliability in computer control is an unsolved but solvable problem. (Some computer scientists might disagreed with this judgment in connection to their opposition to defense against ballistic missiles). Much of the mechanical maintenance will have to be automatic or automatically controlled and inspected if the costs are to be affordable.

3. A new system of navigation and wind observation is required. The navigation problem has become easy now that the GPS (Global Positioning System) is available. Differential GPS will be required for landing. With this, landing and taking off in complete fog will be feasible, i.e. the helicopters would exceed cars in usability.

Wind gusts must be detected and observed. My candidate for this is lidar, i.e. radar using light. The lidar, whether mounted on the flyer or on the ground must scan the air mass through which the plane proposes to fly and determine the velocity field. This can be done by doppler reflection from particles suspended in the air. So far, as I understand it, the technique has mainly been used for atmospheric research.

4. I don't know if the noise problem of helicopters can be sufficiently solved. If the answer is yes, then helicopters are an obvious candidate.

Another candidate is the airplane. For this purpose the airplane must be capable of slow speed flight. It can keep the noise down with a muffler on the motor and a large slow-turning propeller. Lockheed built experimental models of such a plane, called the Q-Star for the Army in the 1960s.

One possibility for landing is that the airplane land and take off from a perch like a bird using legs. If the plane's landing speed is 64 feet per second, and if the legs can extend 16 feet, then an acceleration of 4g will stop the plane in one half second. I believe that anyone can withstand this, properly supported, because it isn't necessary to breathe during that time. Whether people will find the short acceleration acceptable is a matter on which a priori opinions aren't worth much.

The changes in this essay since the 1970s version are minimal. This is because the relevant considerations haven't changed, except that GPS makes navigation easier.

1990s Technological and Political Considerations

There is still no alternative in sight to using hydrocarbons as fuel. The way to minimize the fuel requirement is to use light weight composite materials. These are still very expensive, but Bert Rutan's round-the-world airplane has shown what can be done.

Some billions of dollars will have to be spent to develop personal flying machines. If the American political environment were that of the 19th century, this would be easy. At present, naysayers are too powerful. However, there are some indications that this will change - both in the futuristic attitudes of some politicians and in the attitudes of younger people. The revolution of diminished expectations may have run its course.

Sky-High Invention lists a number of proposals for personal flying machines. It seems to me that almost all of them are based on supporting the machine by direct thrust. This works and will work better with computer control. However, direct thrust for lift burns fuel so fast that the machine can't stay up long enough to be useful.

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