IELTS Academic Reading Practice Test 153

For most of the twentieth century, an engineering drawing was made by hand. A draughtsman worked at a tilted board with pencils, set squares and tracing paper, building up views of a component line by line. When a single dimension changed, every affected view had to be redrawn, and on a large project hundreds of people might be employed doing little else. Drawings were stored in plan chests, and a missing sheet could halt production for days. It was this slow and expensive process that computers eventually transformed.

The first step came from manufacturing rather than design. In the United States, an engineer named John Parsons proposed that a milling machine could be controlled by a sequence of numbers rather than by a skilled operator turning handles. With funding from the United States Air Force, which wanted a faster way to shape complex aircraft parts, the work was taken up at the Servomechanisms Laboratory of the Massachusetts Institute of Technology. In 1952 the laboratory demonstrated a milling machine that cut a curved aircraft component by following coordinates read from punched tape.

Programs for such machines had to be written by hand, a laborious task that occupied skilled staff for weeks. The man who did most to change that was Patrick Hanratty, who in 1957 produced PRONTO, the first commercial system for programming numerically controlled machine tools. He later became known as the father of CAD/CAM, the combined field of design and manufacture by computer.

The idea of designing with a computer was demonstrated at the same institution in 1963, when a young researcher called Ivan Sutherland presented a program he had written for his doctoral thesis. Sketchpad ran on a room-sized machine called the TX-2 and was operated with a light pen, which the user pointed at a screen. Its drawings could be manipulated in ways that now look familiar: lines stretched elastically as the pen moved, and copies were generated instantly. Sketchpad showed what was possible, but it was never sold, and its cost placed it far beyond the reach of any ordinary drawing office.

Industry moved first where accuracy was valued most highly. In the early 1960s the American car maker General Motors worked with IBM on a system known as DAC-1, which was used in the design of body panels. It was a formidable achievement, but the hardware filled a room and was priced accordingly, so that only a large corporation could contemplate buying one. A designer sat at a single terminal linked to a mainframe, and access to the machine had to be booked in advance.

Car bodies and aircraft fuselages raised a mathematical problem as well, because a smooth surface cannot easily be described with straight lines and circles. At the French manufacturer Renault, the engineer Pierre Bézier developed a method for defining a curve by means of a small number of control points, whose position the designer could adjust until the shape looked right. The mathematics behind the idea was not his alone, and a similar approach had been developed independently by Paul de Casteljau at the rival firm Citroën, but Bézier's curves became the standard way of describing the flowing surfaces of vehicles.

Through the 1970s these ideas were consolidated into recognisable design systems, and the aircraft industry again led the way. Engineers at the French company Dassault began building an in-house system to handle the geometry of their aircraft, and it was later sold commercially under the name CATIA. Such programs were still tied to expensive workstations, however, and in most drawing offices the plan chest and the pencil survived untouched.

The economics changed in 1982, when a small Californian company called Autodesk released a program named AutoCAD. It was written for the personal computer, a machine that cost a fraction of a mainframe, and it offered draughtsmen a two-dimensional drawing tool that could be learned in days. Its first version was a modest drafting aid with no three-dimensional modelling at all, yet its price put computer-aided design within reach of small engineering firms, surveyors and architects who had never been able to afford it. Over the following decade it became one of the most widely used design programs in the world.

A more profound change arrived in 1988 with a program called Pro/ENGINEER, developed by a company that later became Parametric Technology. It introduced what is known as parametric, feature-based modelling. Instead of a drawing, the designer built up a three-dimensional model as a sequence of features — a hole, a rib, a rounded edge — each defined by dimensions. Change a dimension and the software would rebuild the whole model, and any drawing made from it, following the recorded sequence. An engineer could now test a dozen variants of a design in the time it had once taken to revise a single one.

The largest demonstration of the technology came with the Boeing 777 airliner in the early 1990s, whose design was carried out entirely on screen using CATIA. Parts were checked for fit in a digital pre-assembly before any metal was cut, which exposed many clashes. The aircraft first flew in 1994, and its development is still cited as the point at which three-dimensional design replaced the full-size master mock-up.

Kerosene, diesel and petrol are stores of energy accumulated underground over millions of years, and burning them releases the carbon they contain. A synthetic fuel, by contrast, is manufactured. It is built from two ingredients: hydrogen, which carries the energy, and carbon dioxide, which supplies the carbon so that the result behaves like a conventional liquid fuel. Because the finished product is chemically almost identical to its fossil equivalent, it can be pumped through existing pipelines, stored in existing tanks and burned in existing engines. This 'drop-in' quality explains the fuel's appeal.

Nearly all synthetic-fuel projects begin with hydrogen made by electrolysis, in which an electric current passed through water separates it into hydrogen and oxygen. If the electricity comes from wind, solar or nuclear generation, the hydrogen carries no fossil carbon, which is why it is often called green hydrogen. Electrolysis is not free of loss: a modern plant converts perhaps two-thirds of the electrical energy it consumes into chemical energy in the hydrogen, and the rest appears as heat. The demand for power is therefore enormous. A plant making useful volumes of fuel must be sited where cheap renewable electricity is available in quantity — windy coasts or sunny deserts.

The carbon dioxide can be captured from the chimney of a cement works or a power station, where it is concentrated and easy to collect. Many early projects take this route because it is cheapest. The alternative is direct air capture, in which fans draw ordinary air across a chemical absorbent that retains carbon dioxide at concentrations of roughly 0.04 per cent. The engineering is elegant, but the volume of air that must be handled is immense and releasing the captured gas takes considerable energy. Direct air capture is therefore much more expensive than collecting the same gas from a flue.

The carbon dioxide is first converted into carbon monoxide, and this is then combined with the hydrogen. The standard route is the Fischer–Tropsch process, which Franz Fischer and Hans Tropsch developed in Germany in the 1920s. The gases are passed over a catalyst at high temperature and pressure, and longer hydrocarbon chains are built up. Germany used the process during the Second World War when oil was scarce, and the South African company Sasol has relied on it for decades to turn coal into liquid fuel. The output is a mixture of chains of different lengths, then refined into kerosene, diesel or the heavier fractions used in ships.

Aviation is the most obvious market. Aircraft need a fuel with a very high energy content per kilogram, and no battery yet comes close; a long-haul airliner would require a battery weighing many times the aircraft itself. Synthetic kerosene can be blended with conventional jet fuel and used without modifying the engine. The world's fleet could in principle be flown on it, and the fuel can be shipped to airports that have no other low-carbon option. Ships are a second market, though here methanol and ammonia are competing with synthetic diesel.

The central problem is efficiency. A battery returns perhaps 80 or 90 per cent of the electricity put into it; a synthetic fuel does not. Each stage, from electrolysis and carbon capture to synthesis and refining, consumes energy. The fraction of the original electricity that ends up driving an aircraft or a ship is often estimated at no more than a tenth to a fifth. Where renewable electricity is abundant and would otherwise be wasted, this hardly matters. Where power is scarce, however, a battery or a direct cable delivers far more useful work from the same wind or sunlight. That is why most analysts expect e-fuels to be reserved for journeys that cannot be electrified.

Cost follows from these losses. Producing a litre of synthetic kerosene currently costs several times as much as refining the fossil equivalent, and the figure depends heavily on the price of electricity and on carbon capture. Optimistic projections suggest that the gap will narrow as electrolysers are mass-produced and renewable power becomes cheaper, but few expect the synthetic product to match fossil kerosene within a decade. The fuel's prospects therefore rest on policy: without a price on carbon, or a mandate obliging airlines to blend a proportion of synthetic fuel, the economics do not work.

Demonstration plants have been built to test the chain at a larger scale. A well-known example stands near Punta Arenas in southern Chile, where strong winds support a wind farm and the site has access to a port. It uses electrolysis and captured carbon dioxide to make a synthetic methanol, which is then converted into liquid fuel, and began producing small volumes in 2022. Similar projects have been announced in Norway, the Netherlands and the United States, most still at the pilot stage. All are small: total world output is a tiny fraction of the fuel burned by aviation alone.

The promise and the arithmetic point in the same direction. Synthetic fuels are the most plausible way to cut emissions from long-haul aviation and from ships that cannot plug in, and they can use the pipes, tanks and airports that already exist. They are also an expensive way to use electricity, and should not be burned in cars or used to heat houses where a battery or a heat pump would be cheaper. The sensible role for e-fuels is therefore narrow but important: a specialist solution for the hardest journeys, not a general substitute for oil.

Few technological ambitions attract as much attention as the plan to put people on Mars. Space agencies in several countries have published outlines of crewed missions, private companies have announced rockets capable of carrying them, and the subject has produced a stream of documentaries and best-selling books. The question I want to consider here is not whether humans will eventually visit Mars — they probably will — but whether the establishment of a permanent, self-supporting settlement is a sensible goal for this century. My answer is that it is not, and that treating it as the purpose of space exploration distorts decisions that have to be made now.

Part of the difficulty is simply that Mars is hostile in ways that are easy to underestimate. Its gravity is about 38 per cent of Earth's, and the long-term effects of that on bone and muscle are unknown. It has no global magnetic field and only a thin atmosphere, so the surface is exposed to radiation that the Earth's inhabitants are largely shielded from. The average temperature is around minus 60°C. The atmosphere is about 95 per cent carbon dioxide at a pressure below one per cent of that at the Earth's surface, so a punctured suit or habitat is not a matter of discomfort but of death within minutes. Dust storms can last for weeks and cut the light reaching solar panels to almost nothing.

The soil adds a further complication. Martian dust contains perchlorates, salts that interfere with the thyroid gland and are toxic to plants and animals, so any greenhouse would need soil that had been washed or treated. Water exists as ice at the poles and, probably, beneath the surface, but extracting it and splitting it into oxygen and hydrogen demands a great deal of power. A settlement would also have to recycle almost all of its water, a technology still being tested in orbit. Every kilogram of equipment must be lifted out of Earth's gravity well in the first place, which is why estimates of the cost of a settlement vary by orders of magnitude.

The strongest argument for going is not scientific but existential: that a self-sufficient colony would insure humanity against catastrophe on Earth. I find this argument weaker than it looks. A settlement that depends on resupply from Earth offers no insurance at all, while a genuinely independent one would have to manufacture tools, medicines, electronics and replacement parts from local materials — an industrial base far beyond anything yet proposed. The hazards most often cited, such as pandemics or nuclear war, would not be escaped by a few thousand people on a frozen planet.

Meanwhile, robots do the science far more cheaply. Orbiters, landers and rovers have mapped the geology, measured the radiation and located the ice, at a cost that would pay for only one crewed expedition. A human mission would return a fraction of the data per pound spent, because most of its mass and money would go on keeping its crew alive. Plans already exist to bring Martian samples back to Earth, a task robots can begin without any crew. Money is finite: the same sum spent on life-support research, on medicine or on decarbonising energy would save many more lives, and the results would be felt within a decade rather than a century.

None of this means that Mars is worthless, and the advocates of exploration have a serious point. Every previous frontier — the oceans, the poles, the Moon — has produced technologies that nobody foresaw: materials, sensors, water recycling, remote medicine. Satellite communication, weather forecasting and water purification are the usual examples, and none of them was the purpose for which the programme that produced them was funded. The difficulty is that such benefits are unpredictable, and a programme justified mainly by hope of spin-offs is hard to defend against other uses of the money. Exploration is worth doing for its own sake, but it should be argued for honestly, not presented as a scheme with a guaranteed return.

There is also an ethical question that receives too little attention. Mars may once have supported life, and it might still, in the form of microbes beneath the surface. International guidelines oblige missions to avoid contaminating other worlds, but a human presence would make it far harder to tell whether any microbe found on Mars was native or had arrived with the visitors. And there is the question of the settlers themselves: a colony that cannot be evacuated is not a normal workplace, and the consent of children born there cannot be assumed.

What I would support is a programme that earns the right to go. That means a return to the Moon, where the journey takes days rather than months and a rescue is conceivable, as a place to learn how to live off local ice and dust. It means robotic sample return from Mars, which would answer the question of past life without exposing anyone to radiation. It means long-duration research in orbit and in Antarctica, where isolation, confinement and cramped conditions can be studied at a fraction of the cost.

The romance of Mars is real, and I do not wish to dismiss it. But romance is a poor basis for a budget. The question is not whether humans deserve to go, but whether we should call a research programme a settlement, and promise a home that we cannot yet build. That is not timidity; it is the ordinary discipline of engineering, which tests a bridge before it invites the traffic across. Explore Mars by all means, and send people there when the journey can be made safely; colonise it only when the technology, and the ethics, have caught up with the ambition.