How to get a Kick out of Gravity
- Gary V Stephenson, Seculine Consulting
Will humankind ever master the control of gravity? If so, how will we be able to control
gravity in useful ways, for instance for space propulsion? The answer may involve
gravitational waves. Just as alternating current, or AC, unlocked the utility of electricity a
century ago, alternating gravity, dubbed "AG", may be the key to unlocking the useful
control of gravity in the century ahead.
What is a gravitational wave?
What is a gravitational wave? It is a ripple in space-time, predicted by general
relativity. Everyone knows Einstein's famous formula E= mc 2, which says that
energy can come from mass - it was the birth of the nuclear age. But Einstein
wrote down an equation even more important: G = K*T. This says that gravity,
the shape of space-time, is equal to a constant K, times T, the mass-energy
tensor, which describes the shape (or distribution) of mass or energy in space. In
other words, gravity, the shape of space-time, depends only on mass and
So all you have to do to make a gravity wave is to change gravity, and all you
have to do to change gravity is to move a little mass or energy around. How
much? That's the catch: the constant K is a VERY small number: about 2*10-43, a
decimal point with 43 zeros, then a 2. So it takes a big change in mass or energy
to make a little gravitational wave.
And there are more problems. Gravitational waves are predicted to be
quadrupole waves. Due to conservation of momentum, every positive going
ripple must be balanced by a negative going ripple - this is the simplest AG
(Alternating Gravity) wave that can exist. See figure 1 for one view of how a time
varying quadrupolar gravitational wave might propagate.
Another problem: no one has actually measured a gravitational wave here on
Earth. It can be induced from the behavior of binary stars that gravitational waves
exist, but it would be nice to detect one here on earth before spending a lot of
time designing ways to use them.
How soon is now?
There is hope. In May of 2003, a group of scientists and engineers met to
discuss the possibility of generating AG waves in the lab. This group was called
the International High Frequency Gravitational Wave (HFGW) working group.
The consensus of that group was that the generation of gravitational waves may
now be within reach of technology, and is therefore worth attempting.
"To make a great dream come true, you must first have a great dream." - Hans Selye
AG GW Source
Figure 1: the Alternating Gravity (AG) Quadrupole Gravitational Wave (QGW)
It is a fairly easy matter to dream of a new technology, but it is quite another to
attempt to develop one. Edison and Tesla did not develop the polyphase electric
generator overnight, and no one expects the development of a gravitational wave
generator to be any easier. Several ideas have been proposed. Baker, Woods,
Li, and others have proposed a number of different ways to create a high order
acceleration in mass to create AG pulses, including very fast nano-technology
Portilla, Navarro, and others have developed a concept first proposed by
Gertsenshtein, which called for AG generation by passing RF or light through a
strong magnetic field, which sets up a resonance with gravity, causing a
gravitational wave. I am reviewing this latter technique in an upcoming paper at
STAIF 2005, the meeting of the Space Technology & Application International
A Source of Propellantless Propulsion?
Most propulsion requires something to push against. Cars push against the road
with their tires to propel themselves. Aircraft push against the air, either with
propellers or with turbofan blades. In space there is nothing to push against
except a reaction force: if you push rocket fuel out the back of a rocket, the
rocket will get pushed forward by it. But rocket fuel is heavy to carry and runs out
quickly. Wouldn't it be nice to get a force in space without needing to carry
propellant? The lure of gravitational waves is that they may someday be able to
provide a way to create an unbalanced force without the use of expelled
Name that technology
When we were kids my brother Ward and I used to play a game. It was a sort of
"name that technology" game where we would see some bit of science fiction on
TV, and we would take turns trying to explain how it worked. Even though he's 3
years younger he was never easy to fool, and I would like to thing that I wasn't
either. So for instance, one if us would ask "How do you think 'phasors' stun?"
then it was up to the other to dream up an explanation like "They probably zap
your nerves with an electric jolt." Then whoever asked the question would be
obligated to sit in judgment on the explanation - the response was either "Cool"
This was a very fun game, but there were a few sci-fi items that eluded
explanation, and the one that comes to mind in the context of this article was the
"impulse drive" on Star Trek. Neither of us really ever came up with how you
could get the USS Enterprise to turn on a dime without any visible rocket
thrusters. Why are there two engines? Why do they stick out like that? According
to StarTrek.com the impulse engines employ "traditional Newtonian action-
reaction thrust physics." Not satisfactory. Surely we can do better than that.
Could gravitational waves be applied to this problem?
The problem with getting a gravitational wave to perform a propulsion function is
that waves are in the form of an alternating or AC signal, but propulsion requires
a constant direction DC force. The process of converting AC to DC is known as
"rectification." In electric current, AC is rectified using a diode, a device that
allows current to flow in only one direction, essentially throwing out the other half.
(Actually there are ways to reverse the other half but let's not get into that right
now.) How would one go about rectifying a quadrupole wave, especially one
which requires that momentum be conserved?
The answer may lie in how the alternating gravity is generated to begin with.
Some AG generator concepts, such as Baker's spindle, use a series of
mechanical motions to generate the gravitational waves, and this motion may be
controlled such that it is fast in one direction, but slow in the other direction. The
resultant AG signal would be a very strong spike in one direction, but a very low
level gravitational signal in the other slower "relaxation" part of the cycle. Since
the response of gravity is non-linear with frequency, the fast signal is much,
much stronger than the slow signal, resulting in an unbalanced force, which is
what we were after in the first place. This concept is known as "quadrupole
rectification" (QR). See figure 2 for a graphic of how this might work.
Figure 2a, Quadrupole Rectification
Step 1: Fast Impulse Step 2: Slow Relaxation
Figure 2b, An Example of an Individual Quadrupole Rectification (QR) Cycle
Note that even if the QR device could be made to work, it still does not look that
useful. Since it is still producing quadrupole waves, for every two "positive going"
(mass-like attractive force) pulses it produces, it also produces two "negative
going" (negative-mass-like repulsive force) pulses. So don't they just balance out,
causing a jitter? No - notice from figure 2a that the pulse directions are now
"sorted" so that all the pulses of one type come out in one direction, and all the
pulses of the other "amplitude" come out in the other direction.
Does life imitate art?
Now imagine a ship that wanted to use the quadrupole rectification of
gravitational waves, let's call them GW motors. If we take a pair of the GW
motors from figure 2b, and we are careful to keep them in phase, and we mount
them away from the body of the ship to which they would be connected, then we
may see unbalanced propulsion forces result, as shown in figure 3.
Fore Reaction Mass
Motor Starboard GW
Aft Reaction Mass
Figure 3, A Balanced Pair QR GW Motor Impulse Drive
Such a scheme might be called a "balanced pair quadrupole rectification
gravitational wave impulse drive," but that is a bit of a mouthful. It might be easier
to call it an "impulse drive" to give credit where credit is due.
The Other AG
Sometimes when the subject of gravitational waves comes up people get a little
nervous. Maybe their face starts twitching, or they look a little clammy, or just not
well. Then they will say something dismissive, like, "Are you talking about Anti-
Gravity?" That's when I can be sure of what is wrong: fear. Fear of the unknown,
fear of being an outcast, fear of not fitting in, Fear. Powerful stuff.
While we are on the subject of Anti-Gravity, and the elephant has wandered into
the room, let's also talk about him, or it, namely, UFOs. UFOs, whether you
believe in them or not, are allegedly users of Anti-Gravity technology. That
means that all gravitationally related work is Verboten, and should be left to
conspiracy theorists. This is really where I part company with the critics, by
making two points:
1) Closing our eyes very tightly has never made anything go away, other than
information and sometimes consciousness.
2) No one tells me what to do, unless I am at work, in traffic, in public, or at
home, and even then I don't always listen.
So when it comes to UFOs, I favor the approach recommended by the famous
aerospace reporter Nick Cook, who recently challenged the aerospace industry
to investigate not whether UFOs exist, but instead to look at how they would work
if they were assumed to exist. How would they hover? How would they undergo
high G maneuvers without harming occupants? And how would they produce
thrust without the use of propellants or propellers? This kind of approach might
lead to some inventive and creative thinking of the type that may include the use
of gravitational waves.
The Allegory of the Cave
In all fairness, we are still cavemen, and we are all afraid to leave our little cave
called Earth. Outside is nothing but the unknown. There might even be monsters.
To truly commit ourselves to space exploration, we will have to overcome these
fears. Plato explained it best in his allegory of the cave. He said that not only are
we cavemen, but we see only the shadows on the walls, and the shadows are
not cast by the light of day, but by a fire of our own making.
Let's not be afraid to seek out a new light. If we truly have faith, we have nothing
About the Author
Gary V. Stephenson received a Bachelor of Science degree in Physics and a Bachelor of
Arts degree in Philosophy from Montana State University in 1983. Since that time he has
worked as a Systems Engineer at Hughes Aircraft Company, ITT, and is presently with The
Boeing Company. Starting in 1989 he has also been the President of Seculine Consulting,
where he specializes in the study of the history of science.