Tuesday, May 11, 2010

Gravity Plating

A common plot device in science fiction like Star Trek that allows crew to walk around in full gravity on spaceships is Gravity Plating. The idea is simply that the ship is plated with some magical technology that dramatically decreases the strain on the show's special effects budget :)

Having just this technology would have a major effect on NASA's future long duration missions asteroids, Mars and beyond, not to mention stays on the International Space Station.

Serious discussions of artificial gravity generation today are based on the concept of rotating the habitation module. Either a big torus like in 2001 A Space Odyssey, Mission To Mars, Red Planet, and Babylon 5 or, more practical, using a long tether between the habitat and a counterweight, say the expended trans-mars injection stage. Both options are incredibly difficult to do and dangerous. As such, their discussion in NASA circles has been virtually taboo for decades.

Which is why recently, while thinking about gravity plating in science fiction, that I was reminded of some NASA work announced last year that may be applicable. The work involves levitating mice. Perhaps the research got funded because its counter-intuitive to think of levitation as a means for producing artificial gravity. In fact, the research is studying the physiological impact of prolonged microgravity, and possible medical countermeasures.. the kind of work they do on the ISS, but presumably a lot cheaper.

So what do levitating mice have to do with gravity plating?

Imagine the levitating mouse experiment in zero-g. The mouse would already be "levitating", as would everything else, so what would it experience as it approaches a superconducting magnet that is firmly attached to the station? If the "ceiling" of the mouse's cage is the superconducting magnet, the mouse will experience a repulsive force towards the "floor" of the cage.

Diamagnetic repulsion requires a very strong magnetic field, typically in the range of 16 teslas, and so create significant problems if ferromagnetic materials are nearby. Superconducting magnets currently are very heavy and require cryogenic cooling. So, unfortunately, this may also be too dangerous for use by NASA in future spacecraft.

5 comments:

  1. Or you can just travel at near light speed and allow the relativisticly self-induced gravitational field do the job. Hopefully the gravitation of the hull of the ship itself will not self implode under the force of the gravity generated. If it holds up, then you only have to worry about being ripped to shreds as you body is attracted in all 360 degrees towards the hull of the ship. Travelling at light speed would be a little like falling into a black hole, both will likely ruin your day.

    That FTL experience might prove to be a lot worse than just your simple diamagnetic repulsion. Maybe we can just brew up a special concoction of non-toxic bismuth martinis to infuse into the blood of space travellers and thereby use a lower gauss magnetic field? After the first drink or two you would forget all about the bad taste and hurry back to the gym compartment for some real exercise.

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  2. heh, for sure Steve. Of course, after you make your propellantless propulsion drive you can probably just use the power from your micro-fusion core to accelerate at 1g.

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  3. You never know, your "propellantless propulsion drive" might be possible. If you think about it, space-time contains energy, and energy has mass. The trick would be how to induce it to flow past the ship and build a 'propulsion system' to make use of it. On the macro scale this would be a non-starter because of the amount of energy needed to drive such a system, but on the quantum scale it might be possible. If you could harness the aggregation of many many quantum fluctuations of space-time, and focus it in one direction, then you might move in the opposite direction. Think of it as a Magnetohydrodynamic drive operating through quantum mechanics instead of large magnetic fields.

    If you could do that by utilizing the energy contained within that same flowing space-time you would have exactly what would be needed for any real aspirations of space exploration. It kind of sounds like a perpetual motion machine, but quantum physics is one place where you can temporarily break the Newtonian laws of physics and still be able to account for all the energy balancing after the reaction. It could actually be possible, we just don't know enough to understand all the quantum processes required yet. My suspicion is that once we truly understand the quantum nature of 'time' itself such things might be possible.

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  4. Anonymous11:22 AM

    In real life, the only ways to simulate gravity we know of are by rotation or linear acceleration. A spacecraft that continuously accelerated at 1 g would appear to have gravity aboard it, and reach near-light speed in a year. A rotating space habitat would also appear to have gravity aboard it. No engine today can accelerate constantly at 1g or even .5g. If such engines existed, star travel could become a reality.

    Back on the topic of gravity plating, I don't really see how it is supposed to work. We do not completely understand gravity yet, and gravity control remains a pipe dream. Reports of gravity control exist, but there is little hard evidence to back them up. Gravity causes all mass and energy to attract each other, and we can't turn it on and off like a magnetic field. We could pile a whole bunch of mass in one place to create gravity, but that wouldn't be very practical gravity plating.

    You suggested using an electromagnetic field to simulate gravity. However, this is not very practical either. We can generate electric and magnetic fields that will cause objects to levitate, and could conceivably cause an object to feel a force similar to gravity in a microgravity environment. The magnets required create a field strong enough to simulate gravity would be very bulky and heavy, and even more importantly, the electronics on the ship would not take kindly to fields of this magnitude near them. Not to mention any ferromagnetic object would become a lethal projectile if it was caught in the field. I would pass on the Diamagnetic Pseudo-Gravity Generator!! If you did use a device like this, you wouldn't be able to simulate gravity completely. Gravity is always attractive and acts on all matter and energy. Electromagnetic forces can be attractive or repulsive, and act on charged objects. A diamagnetic field would repel diamagnetic substances, but ferromagnetic objects would much more strongly attracted. You would have succeeded in creating a field that simulated one aspect of a gravity field over a short distance, but not in creating actual gravity or anything resembling it. There is no known way to simulate gravity using electromagnetic forces.

    -Christopher

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  5. Anonymous11:23 AM

    Artificial gravity would change the future of space travel. Unfortunately, there is no convenient way of generating it. You would experience gravity on board a constantly accelerating space ship, but we do not have an engine that can operate constantly at high thrust yet. Rotation has severe engineering problems. Maybe a large space station could use it, but a small rocket ship probably can't.

    It is possible that space researchers could develop medications to combat the effects of weightlessness This would be vital for the crews health, and a lot less expensive than using a rotating centrifuge. It reminds me of the early days of sea travel, when scurvy claimed the lives of many sailors. Until we have techniques to keep astronauts bones and muscles from atrophying, and shield them from radiation, space travel will remain very dangerous. Many people like to focus on propulsion systems, because they are cool, but space medicine and life support are just as vital. Even if a dirt-cheap launch and propulsion systems are invented, without resolving the medical issues, it is unlikely we will be able to found colonies on Mars or the Moon. We might dash out to Mars and back, but the crews health would probably suffer for it. But that didn't stop the early sea explorers....

    Of course, soft SF authors have their gravity plating, magic radiation-shielding paint, and force fields. But, as of today, our space travel technologies are as clumsy as a dugout canoe, pointy stick, dried fish, and wooden paddle. Can't cross an ocean with those tools.

    -Christopher

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