Simulating gravity

In the epic science fiction movie 2001: A Space Odyssey, producer and director Stanley Kubrick and sci-fi author Arthur C Clarke envisioned the creation of “artificial gravity” using a monumental centrifuge — a giant spinning drum fitted with control consoles and furniture for astronauts. That movie was released way back in 1968.

Fifty-four years later, Orbital Assembly Corporation, following the movie’s footsteps, recently announced a plan to develop a space business park (hotel), complete with the so-called artificial gravity and designed to accommodate 28 guests, in five modules built around a spinning “gravity” ring. It plans to simulate a sixth of Earth’s gravity.

The California-based start-up aims to make its first Pioneer-class space station operational by 2025 — an ambitious target, if not unrealistic. Notwithstanding the ginormous claims, and a maze of scientific mumbo jumbo, is the creation of artificial gravity even possible?

The idea of using artificial gravity within a spacecraft is certainly intriguing. According to many scientific experts, simulating Earth’s gravity (even a fraction of it) and countering weightlessness would help keep astronauts healthy on long trips, preventing loss of bone density and muscle atrophy, to Mars and even further. Also, fluids in the body shift upward to the head in microgravity, which may put pressure on the eyes and cause vision problems.

The impact of microgravity on humans’ physical and mental health is unfathomable and ensuring artificial gravity shall help humanity settle on celestial bodies beyond Earth. Sadly, there is no confirmed technology at present that can simulate gravity, other than actual mass or acceleration.

But there are several proposals at play. The first and considered most feasible is making a spaceship rotate. Remember a carnival ride: When we are inside a large, spinning object, we feel a pull toward the outside wall. This is because of inertia or the pseudo “centrifugal force” in such a scenario — the basis of the solution to artificial gravity in 2001: A Space Odyssey.

A 2013 piece in Wired on how artificial gravity worked inside the iconic spaceship shown in Kubrick’s movie explained that the spinning centrifuge’s function should actually be to counteract the weightlessness astronauts feel in space. “Really, a spinning spacecraft could produce an artificial apparent weight — but not artificial gravity,” wrote Rhett Allain, professor of physics at Southeastern Louisiana University. Similarly, centripetal acceleration could be used and a person on board would feel the outer hull of a spaceship pushing him/her towards the centre.

But there is an issue of size with such a solution. With rotating spacecraft, the radius of rotation grows with the square of the orbital period. “If you wanted to simulate Earth’s gravity, for example, you would need a radius of 56m if the orbital period was 15 seconds. A period of 30 seconds would need a 224-m radius and so on. As delivery of materials to space is very expensive, at present, designs would need to reduce mass as much as possible. Ship designs could also assist to keep the material needed to a minimum,” explains an article in interestingengineering.com.

When looked at for setting up space colonies, however, this centrifuge solution is worth considering. Called the O’Neill system, after Gerard K O’Neill, a Princeton University physicist, who gained fame in the 1970s for his detailed concepts for human settlements in space, this idea caught the attention of Jeff Bezos, founder of Amazon and space company Blue Origin. He once showed interest in building O’Neill cylinders, but nothing happened thereafter in that regard.

Another approach could be to use electricity and magnetism as a way of substituting for gravity. This can be done via creating a magnetic field by running electricity in circles (this would produce magnetism). Astronauts would wear metal boots and the magnetic attraction should allow them to walk on the floor. But this method could be extremely power-sapping, a no-no in a spacecraft where every resource is limited. Also, being stuck to the floor isn’t the same as gravity.

According to Mika McKinnon, physicist at Search for Extraterrestrial Intelligence Institute, scientists could try to harness real gravity. Everything with mass has gravity. “Build yourself a planet and then you’ve got enough gravity,” she noted (www.sciencenewsforstudents.org). That, of course, is easier said than done.

The key might be to get a lot of mass into a very small area. “A teaspoon of neutron-star material might be enough to give us gravity… or a tiny pencil prick of a black hole,” she said. Neither feasible nor possible currently.

Another idea is making gravity generators. In the 1990s, Eugene Podkletnov, a Russian engineer, claimed to have designed and demonstrated gravitomagnetic devices consisting of rotating discs constructed from ceramic superconducting materials. But this couldn't be verified by third parties. In 2006, another research group created a similar device but that resulted in “creation” of only around 0.0001g. The process wasn’t replicated. However, string theory does predict that gravity and electromagnetism could be unified in hidden dimensions and act as a way to “generate” gravity in the future. But all the above-mentioned solutions to artificial gravity are in the realms of concept and fiction — and a tall order for the laws of science.