Gravitic Engineering: The Next Technological Frontier?

Is it “anti-gravity”?  Ummm… No!  There’s no such thing, and given our present understanding of general relativity, there never will be.  But that doesn’t mean that we can’t develop technologies that use gravitational gradients in a loosely analogous manner to the way that we use the electromagnetic force gradients.

Before I launch into my own speculative “inventions” in gravitics, it is incumbent upon me to tell you about the man who was likely the true father of gravitics, Robert L. Forward.  He invented the rotating cruciform gravity gradiometer or ‘Forward Mass Detector’, for Lunar Mascon (mass concentration) measurements.  This device is so sensitive that it can detect the gravitational gradient of an object as small as a fist held near it.  His 1965 physics doctoral thesis was Detectors for Dynamic Gravitational Fields, for the development of a bar antenna for the detection of gravitational radiation.  He was an inventor with eighteen patents.  Learning of his ideas by reading his science fiction novels shaped my own.

So, can we build something that looks like antigravity (but isn’t)?  Yes we can, in theory.  First, imagine, if you will, finding a mountain of solid heavy metal, uranium will do.  If you dig a tunnel under it, the gravity there will be lower than on the surface because of the huge mass above.  But only by a tiny fraction.  Sorry, no antigravity hoverboard.

Anything else?  Why yes.  Here’s my idea for a gravitically propelled orbtal transport ship.  I apoligize in advance, the explanation of how it works gets a bit technical and requires a good grounding in basic physics and orbital mechanics.  But bear with me.

First, lets imagine a space station that is built like two Eiffel towers stuck together by their feet.  Such a huge structure, built in orbit, would experience tidal forces that would tend to tidally lock its rotation to match its orbital period.  (I did warn you that this would take some understanding of orbital mechanics, right?).  That is to say, that it, like the moon which is also tidally locked, will always point toward the center of the Earth unless something is done to change that.  Oh, and just for fun, and to make it even more likely to become tidally locked, we put big masses on each end of this long structure.

Now imagine putting a set of huge gyros on this structure.  It’s placement probably wouldn’t matter, but for simplicity, lets place it at the center of the structure.  Once spun up, gyros have the convenient property of resisting a force that would change its axis of rotation.  Satellites often have gyros to aid in pointing them where we want them to point.  Now imagine what would happen if, after they have been spun up, the gyros were to be locked to the structure so that it resisted the tidally locked rotation.  That is to say, we attempted to make it point at a single star in the far distance, instead of rotating to always point to the center of the Earth?

Can you guess?  Well first, the rotation would have to be stopped… so lets just assume that we did that.  OK, now what?

Well, that tidal force isn’t going to go away.  As the structure continues in its orbit, the angular difference between where the structure is pointed and where it “wants” to be pointed to reduce the tidal stress will grow.  Now, imagine we suddenly let the structure free.  It would relax the tidal stress and start to rotate, exchanging potential energy for kinetic energy.  Where did that energy come from?  Can you guess?

It came from the potential and kinetic energy of the orbit.  We caused the structure to “drop” into a lower orbit, all without propellent!

The reverse can be done as well.  Consider what would happen if we use motors between the gyros and the structure to force the structure to “lean forward”, as though it was already pointing to a direction that tidally speaking, it will in the future when its orbit brings it to that position.  Now, when we “lean” the structure, we are putting energy into its energy of potential.  But when the structure gets to the point where its tidal forces are gone, as it points to the center of the Earth… oops, the potential energy is gone!  Where did it go?  Can you guess?

Yes, it is in the potential and kinetic energy of the orbit.  We caused the structure to “climb” into a higher orbit, all without propellent!

We can also use this same concept to shift orbits laterally.  So, we can go up, down, and sideways in orbit, all without propellent!

The downside of this technique?  The gravitic forces are very weak, so the change in orbits will be very slow.  Further, the limit to how much angular mementum that can be pre-stored in the gyros to allow a climb limits the orbital altitude that may be gained.   (Angular momentum is still conserved in this scheme, of course.)  The concept might work for station keeping though.  But still, as an excersize in thinking creatively and big, its a great idea.

So, your turn.  Think about gravitics.

(Addendum 1/8/2016:  Exciting new paper, “How current loops and selenoids curve space-time” regarding generating artificial gravity fields using magnetic energy stored inside of electromagnets.  Yes, its real physics, based on Einstein’s General Relativity and the Equivilance Principle.  The effect is REALLY tiny, but may allow us to generate controlled gravity pulses someday:  http://arxiv.org/abs/1504.00333 )