Controlling gravity will probably never help us launch a spacecraft, but that does not mean we should give up on the idea, says the European Space Agency. It is calling for missions that might one day enable us to harness gravity, however weakly, for the benefits we will reap back on Earth.
ESA has never got involved in gravity-control research before. But NASA’s highly theoretical Breakthrough Propulsion Physics project in Cleveland, as well as recent announcements of unusual experimental findings in major science journals, have convinced the agency to take the field seriously, according to ESA adviser Clovis de Matos.
Since September 2001, investigators Orfeu Bertolami and Martin Tajmar have been combing through more than a dozen different gravity-control schemes for ESA. They conclude that most are not worth wasting money on.
Some schemes, such as certain notions based on superstring theory, promise gravity-reducing effects so weak they would provide a “push” only a billion-billionth as strong as the Earth’s pull. Others simply contradict well-tested science.
But while Bertolami and Tajmar conclude that antigravity is still out of reach, they propose three simple missions that might lead to it in the future.
One is a Sputnik 5 spacecraft to investigate strange gravitational effects felt by the Pioneer 10 and 11 probes. In a second mission, experiments on the International Space Station could test whether antimatter falls any differently from normal matter.
Finally, they propose studies of superconductors and of superfluids – supercooled gases that flow without any friction – to investigate whether spinning them can create “gravitomagnetic” fields, much as rotating a magnet creates an electromagnetic field.
But even if we do work out how to control gravity, it will not help launch spacecraft, the researchers say. If a ship could be made lighter, any propellant it ejected would be lighter too, so it would not accelerate any faster.
Marc Millis, founder of NASA’s Breakthrough Propulsion Physics project, says it could be easier to launch a lighter ship if it was propelled by something outside its low-gravity force field, such as bombs exploded behind it.
But even so, gravity is just one of the problems a spacecraft has to contend with. To launch a satellite into low-Earth orbit, for instance, it has to reach a speed of 8.9 kilometres per second. Even completely shielding it from gravity, it would still have to reach 7.5 kilometres per second just to stay in orbit.
But gravity control would be valuable here on Earth. Metals, ceramics and organic crystals made in microgravity show remarkable qualities. Alloys made in microgravity can be far stronger than normal because they lack the defects caused when gravity swirls the molten metal.
Microgravity also means objects can be suspended in mid-air, avoiding containers that could contaminate a pharmaceutical reaction, say. And certain superconductors can only be grown in microgravity.
Doing all that in space would be hugely expensive, but antigravity would mean it could be done on Earth, says Tajmar.