Technology as Magic...in an age of pessimism

Robert Goddard was a dreamer and inventor. Born in Massachusetts in 1882, he was a sickly child, and fell behind his fellow students. But he had an  insatiable curiosity about the physical world and was a voracious reader. He managed to become valedictorian of his high school class, stating in his address, "It has often proved true that the dream of yesterday is the hope of today, and the reality of tomorrow." 

Robert Goddard had dreams of practical liquid fueled rocketry, and he was the pioneer in the field. In 1926 he launched his first liquid- fueled rocket, and worked throughout the 1930s to develop his designs for higher altitude. His work was so successful that it caught the attention of the Germans, who during the second world war, used their own V2 liquid fueled rocket, built around Goddard’s ideas, to attack England. And he believed that liquid fueled rockets had the capability of taking man to the moon. Robert Goddard was a visionary and achieved amazing things.

And yet he was mercilessly ridiculed for his efforts and belief that his liquid rocket technology would take man into space. In 1920 a New York Times editorial expressed disbelief that Professor Goddard actually "does not know of the relation of action to reaction, and the need to have something better than a vacuum against which to react". Goddard, the Times declared, "only seems to lack the knowledge ladled out daily in high schools”.

Justice was finally served many years after his death, when the Times published a short item entitled “A Correction” on July 17, 1969, the day after the launch of Apollo 11. Although a bit tongue-in-cheek, but no doubt heartfelt, "A Correction", summarized its 1920 editorial mocking Goddard, and concluded, "Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error.

William Thomson (1824-1907) was a British engineer and physicist, who among other achievements, was noted for his work on the transatlantic telegraph, the mariner’s compass, and on the laws of thermodynamics. He was knighted and elevated to the House of Lords in London, earning the title Lord Kelvin. He is probably best known in scientific circles for developing the concept of an absolute zero temperature, and thus the temperature unit Kelvin is named in his honour. In his day Lord Kelvin was extremely successful, and very well respected.

And he became additionally well known in the technical world for a prediction gone wrong. In a 1902 newspaper interview, one year before the Wright brothers’ first flight, he predicted that "no balloon and no aeroplane will ever be practically successful."

It seems there was a time, early in the past century, when prestigious newspapers and learned persons, not to mention the general public, had little faith in the potential for advancement of technology.

How times have changed.

The Relentless Advance of Technology

I bought a run-of-the-mill new laptop computer last week. It cost me eight hundred dollars, and it has 4 Gigabytes of random access memory (RAM). In 1983, my parents bought our family an Apple II computer for three thousand dollars. It had 64K of RAM memory, which was already 4 times more than the moon-landing Apollo 11 spacecraft on-board computer, developed by NASA 14 years earlier. Thus from 1983 to today, a period of 27 years, a consumer grade personal computer has increased in at least one aspect of performance by a factor of 63,000 and dropped in price by 75% (not even considering inflation). I don’t really need to remind you that the computing power of the personal computer has increased exponentially since it was first developed.

And it’s not just computers. There isn’t a day that goes by when some new advancement in technology isn’t announced in the media.

It’s literally everywhere, and with the introduction of the Internet, tool of communication and trading of information, the root of all technical innovation, the rate of advance only increases.

Incredible, odds-defying advances are everywhere.

In medicine, it’s new very serious diseases arriving on the scene such as HIV/AIDS, and at least life-prolonging treatment developed within two decades of its arrival. It’s MRI development, giving accurate non-invasive diagnosis almost in real time. From unravelling the human genome, to stem cell research and disease treatment, it does not stop.

Privately developed space aircraft are on the verge of taking paying passengers into space, and the international space station is going strong.

It seems there are no limits to what technology can do. Even aircraft that are powered by the sun are making the news.

Solar Aviation – the Sky’s the Limit

The Solar Impulse project is the brainchild of Bertrand Piccard, a Swiss balloonist and adventurer. Piccard, in conjunction with the École Polytechnique Fédérale de Lausanne, is developing two aircraft for what is planned to become the first attempt to circumnavigate the globe in a solar powered aircraft.

The first aircraft, named HB-SIA, is a prototype, being tested in 2010 and making big news doing so. The second aircraft, named HB-SIB, will be slightly larger and will have the capacity to travel around the world in around 25 days.

The first Solar Impulse aircraft is a one-seater. It has a very large wingspan –63 meters, and is 21 meters long. It has four 10-horsepower electric motors, driving propellers, and has a maximum speed in flight of 70 kilometers per hour. It is made of lightweight materials such as carbon fibre.

Beyond the sheer thrill of adventure, Piccard`s motives for attempting such a groundbreaking technical feat are about showing how science and technology can be used for the development of renewable energy sources.

He is quoted as saying "We have to support the environment without threatening the world economy and our mobility. Solar Impulse will show that a win-win situation is possible."

A Challenge to the Reader

I am now going to pose a challenge to the reader. Would you follow me through a very short, but meaningful, engineering calculation? There is a lesson to be learned on the completion of the calculation, and I think, if you have the patience to follow, you will profit from it.

OK, here goes. Asking myself the question “With all the interest surrounding solar aviation, could solar power be used to power a typical modern passenger aircraft?”, I set out to find an answer. It is a surprisingly simple calculation, so please follow along, if you wish. 

Using the concept of conservation of energy (from the First Law of Thermodynamics, but please, don’t let these fancy words intimidate you), let us simply compare the maximum possible amount of solar power available from the sun landing on the upper surface of the aircraft (that would somehow be converted into forward propulsive power) compared to the actual power consumed during take-off. Let’s consider using a fairly big aircraft, say, the Boeing 737-900, for example. This is the latest version of the 737, the passenger transport workhorse of many airlines worldwide.

From the publicly available specifications for the 737-900, the total surface area of the aircraft when viewed from above is approximately 290 square meters. Let’s assume it’s completely covered in solar panels, and all of the sun’s power gets transferred into the propulsion system. Assuming the power from the sun landing on the aircraft skin is approximately 1.0 kilowatt per square meter at sea-level (this is also called insolation, and 1.0 is a typical value used at the equator, for a sunny day), the total solar power available to the aircraft is therefore 290 kilowatts (kW). For those readers who prefer dealing in Imperial units, this equates to about 390 horsepower, the power typically available from a large automobile engine.

So, how much power is required to get a 737-900 off the ground and into the air, at high speed? From publicly available information, the fuel consumption of the jet engine on the 737-900 (called the CFM56-7) under full power (take-off) conditions is approximately 0.91 kilograms per second. There are two engines on a 737, so the total fuel consumption at take-off is 1.82 kilograms per second. Knowing that the energy content of jet fuel (similar to kerosene) is about 43,000 kilojoules per kilogram, multiplying the two gives 78,260 kilojoules per second (or kilowatts, as kilojoules per second are known).

So the maximum possible power available from the sun is 290 kilowatts, and the fuel power required at take-off is 78,260 kilowatts (or about 105,000 horsepower). This results in the conclusion that the aircraft take-off power requirement is 270 times greater than the maximum power available from the sun.

For readers with a technical background, I will point out that my calculations are highly simplistic, in that I have disregarded both solar cell efficiencies and jet engine efficiencies (converting fuel energy into forward thrust). Given that solar cell efficiency and jet engine efficiencies are both in the order of 30 to 40 percent, the overall power ratio remains the same.

So, in summary, our very simple energy-balance engineering calculation shows the impossibility of ever powering a large, high-speed passenger aircraft with solar power.

Predicting The Future Of Solar Aviation

So, now that we have established that solar power is insufficient to power a transport aircraft the size of a 737 (with its speed and passenger carrying performance characteristics) by a factor of 270 to 1, let’s quickly estimate what the specifications of a solar powered aircraft with the wingspan similar to that of a 737 would look like.

Given that the available solar power for the aircraft is in the order of 290 kW (or 390 HP) and the electrical power available is a lot less in practice, there would probably be one or several small electric motor-driven propellers. The aircraft might have lightweight and dense batteries for some power storage. The aircraft would have a large wingspan (for solar power collection as well as high lift at low speed), but the body would be small and thin, and the whole structure would be lightweight, no doubt made of carbon fibre and other composite materials. The aircraft would be slow moving, and fragile, and possibly be able to carry one, or maybe several passengers, at the most.

Lo and behold, that sounds a lot like a description of Solar Impluse.

In other words, Solar Impulse, for all the wonder that it is, is about the best humanity is ever going to get out of a solar powered airplane. Any notion that the sun will ever power a heavier-than-air passenger-carrying aircraft significantly larger or faster than Solar Impulse is simply incorrect. The power required from the sun is simply not available in sufficient quantity, as we have shown.

Building Unrealistic Expectations

I think Bertrand Piccard’s goals are noble, and Solar Impulse is a great project. Both inspiring a new generation of aviation adventure, and generating interest in sustainable development are good objectives.

Solar powered aircraft no doubt have a practical future, possibly being used as long-duration, high altitude communication platforms. But solar power will never drive large, high-speed transport aircraft. We have proven it together in this article, and should anyone propose to develop one, we can advise against it with confidence.

I take issue with one of the outcomes of Solar Impulse. I have heard a senior executive in civil transport aviation (someone without technical training), speak about research into solar aviation. He left the decided impression among the listeners that solar aviation for passenger traffic was not only possible, but also the inevitable future of aviation.

When Bertrand Piccard attempts to show that air mobility is not threatened when supporting the environment by the use of solar power, he is entirely wrong. Affordable air travel for the general public is completely threatened by the use of solar power for aircraft propulsive power.

When projects like Solar Impulse are used, whether purposefully or not, to further the public’s expectations that anything is literally possible via technology, this is not only wrong, but also dangerous.

Technology As Magic

Unlike in the early part of the 20th century, the general public has come to have a very different view of technology and its possibilities.

I have heard it said by numerous economists that regarding climate change, and greenhouse gas emission reductions, economic incentive plans such as a carbon tax will spur technical innovation, with the implication that there are no limits to technology. Tax it, and it will come! The technical solution, that is.

This kind of thinking is somewhat naïve. No doubt economic incentive schemes can have an effect, depending on the technology available. 

My point in performing the aircraft calculation above was to show that there are limits to technology based on, among other things, physical laws. Today we suffer from the opposite problem of the past, namely, the general public, not to mention some economists, believe there are no limits. We have developed unrealistic expectations of what is possible.

Critical Thinking Required

Humanity faces some very difficult challenges going forward, especially with regards to reducing emissions of all kinds, and building a more sustainable energy future. And while there are huge political elements to these challenges, there are also technical challenges.

I am personally against any effort to make the challenges we have look easy to solve, and the proposal of simplistic solutions to hugely integrated problems. When our citizens en masse start to expect unfeasible miracles from technology, and this gets translated into unrealistic policy from government bodies, we all lose. Investment money, a limited resource, is wasted on projects that ultimately do not deliver concrete benefits to society. And time is wasted.

There is much serious work to do to build a sustainable future. We need to embrace our enthusiasm for technical solutions with critical thinking so that the best, most realistic solutions are implemented.

We must not be lulled into thinking there are easy solutions to energy-related technical challenges, or sold exaggerated capabilities. There is too much at stake to get it wrong.

Learning From Icarus

Icarus, of Greek mythology fame, was the son of Daedalus. Icarus and his father were imprisoned on the island of Crete by King Minos. In an effort to escape, Daedalus fashioned two pairs of wings out of wax and feathers for himself and his son.

Enthralled with his new wings, and the possibility of flight, Icarus flew too close to the sun, beyond the capabilities of his wings. His wax wings melted and he plunged to his death in the Icarian Sea, which today bears his name.

We can learn from Icarus. All the technology around us is astounding. As I have described, as a society, we have gone from underestimating the possibility of technological advance, to now believing there are no limits. We are told time and again that all of the huge challenges facing our world, be it climate change, peak oil, and future energy crises are all solvable with existing and future technology that will inevitably be developed.

But there are limits, and the laws of physics apply today just as they always have. We need to balance our enthusiasm for technology with the critical thinking required to properly evaluate which future technologies make sense and which don’t. We have the power to do this.

Let’s not allow our belief in the future of technology to cause us to fly too close to the sun, wasting precious time and resources on ill-thought out ideas.