Can the Vacuum be Engineered
for Spaceflight applications?
Overview of Theory and Experiments
H. E. Puthoff, Ph.D.
Institute for Advanced Studies at Austin
4030 W. Braker Lane, Suite 300
Austin, TX 78759-5329
Voice (512) 346-9947, Fax (512) 346-3017, E-mail: firstname.lastname@example.org
Date: Mon, 18 Aug 1997 16:21:16 -0400 (EDT)
Subject: Re: NASA posts the results of propulsion conference
For those interested, here is a copy of the paper I presented at the NASA
Breakthrough Propulsion Physics conference at Lewis Research Center last
week. - Hal Puthoff
Quantum theory predicts, and experiments verify, that empty space (the
vacuum) contains an enormous residual background energy known as zero-point
Originally thought to be of significance only for such esoteric concerns as
small perturbations to atomic emission processes, it is now known to play a
role in large-scale phenomena of interest to technologists as well, such as
the inhibition of spontaneous emission, the generation of short-range
attractive forces (e.g., the Casimir force), and the possibility of
accounting for sonoluminescence phenomena.
ZPE topics of interest for spaceflight applications range from fundamental
issues (where does inertia come from, can it be controlled?), through
laboratory attempts to extract useful energy from vacuum fluctuations (can
the ZPE be "mined" for practical use?), to scientifically-grounded
extrapolations concerning "engineering the vacuum" (is "warp-drive" space
propulsion a scientific possibility?). Recent advances in research into
the physics of the underlying ZPE indicate the possibility of potential
application in all these areas of interest.
The concept "engineering the vacuum" was first introduced by Nobel Laureate
T. D. Lee in his book Particle Physics and Introduction to Field Theory. As
stated there: "The experimental method to alter the properties of the
vacuum may be called vacuum engineering.... If indeed we are able to alter
the vacuum, then we may encounter some new phenomena, totally unexpected."
Recent experiments have indeed shown this to be the case.
With regard to space propulsion, the question of engineering the vacuum can
be put succinctly: "Can empty space itself provide the solution?"
Surprisingly enough, there are hints that potential help may in fact emerge
quite literally out of the vacuum of so-called "empty space." Quantum
theory tells us that empty space is not truly empty, but rather is the seat
of myriad energetic quantum processes that could have profound implications
for future space travel. To understand these implications it will serve us
to review briefly the historical development of the scientific view of what
constitutes empty space.
At the time of the Greek philosophers, Democritus argued that empty space
was truly a void, otherwise there would not be room for the motion of
Aristotle, on the other hand, argued equally forcefully that what appeared
to be empty space was in fact a plenum (a background filled with
substance), for did not heat and light travel from place to place as if
carried by some kind of medium?
The argument went back and forth through the centuries until finally
codified by Maxwell's theory of the luminiferous ether, a plenum that
carried electromagnetic waves, including light, much as water carries waves
across its surface. Attempts to measure the properties of this ether, or
to measure the Earth's velocity through the ether (as in the Michelson-
Morley experiment), however, met with failure.
With the rise of special relativity which did not require reference to such
an underlying substrate, Einstein in 1905 effectively banished the ether in
favor of the concept that empty space constitutes a true void. Ten years
later, however, Einstein's own development of the general theory of
relativity with its concept of curved space and distorted geometry forced
him to reverse his stand and opt for a richly-endowed plenum, under the new
label spacetime metric.
It was the advent of modern quantum theory, however, that established the
quantum vacuum, so-called empty space, as a very active place, with
particles arising and disappearing, a virtual plasma, and fields
continuously fluctuating about their zero baseline values. The energy
associated with such processes is called zero-point energy (ZPE),
reflecting the fact that such activity remains even at absolute zero.
THE VACUUM AS A POTENTIAL ENERGY SOURCE
At its most fundamental level, we now recognize that the quantum vacuum is
an enormous reservoir of untapped energy, with energy densities
conservatively estimated by Feynman and others to be on the order of
nuclear energy densities or greater. Therefore, the question is, can the
ZPE be "mined" for practical use? If so, it would constitute a virtually
ubiquitous energy supply, a veritable "Holy Grail" energy source for space
As utopian as such a possibility may seem, physicist Robert Forward at
Hughes Research Laboratories demonstrated proof-of-principle in a paper
published in 1984, "Extracting Electrical Energy from the Vacuum by
Cohesion of Charged Foliated Conductors."
Forward's approach exploited a phenomenon called the Casimir Effect, an
attractive quantum force between closely-spaced metal plates, named for its
discoverer, H. G. B. Casimir of Philips Laboratories in the Netherlands.
The Casimir force, recently measured with high accuracy by S. K. Lamoreaux
at the University of Washington, derives from partial shielding of the
interior region of the plates from the background zero-point fluctuations
of the vacuum electromagnetic field.
As shown by Los Alamos theorist Milonni and his colleagues, this shielding
results in the plates being pushed together by the unbalanced ZPE radiation
pressures. The result is a corollary conversion of vacuum energy to some
other form such as heat.
Proof that such a process violates neither energy nor thermodynamic
constraints can be found in a paper by D. Cole and myself published in 1993
under the title "Extracting Energy and Heat from the Vacuum."
Attempts to harness the Casimir and related effects for vacuum energy
conversion are ongoing in our laboratory and elsewhere. The fact that its
potential application to space propulsion has not gone unnoticed by the Air
Force can be seen in its request for proposals for the FY-1986 Defense SBIR
Program. Under entry AF86-77, Air Force Rocket Propulsion Laboratory
(AFRPL) Topic: Non-Conventional Propulsion Concepts we find the statement:
"Bold, new non-conventional propulsion concepts are solicited.... The
specific areas in which AFRPL is interested include.... (6) Esoteric energy
sources for propulsion including the zero point quantum dynamic energy of
Several experimental formats for tapping the ZPE for practical use are
under investigation in our laboratory. An early one of interest is based
on the idea of a Casimir pinch effect in non-neutral plasmas, basically a
plasma equivalent of Forward's electromechanical charged-plate collapse
(see Puthoff, 1990). The underlying physics is described in a paper
submitted for publication by myself and M. Piestrup, and it is illustrative
that the first of several patents issued to a consultant to our laboratory,
K.R. Shoulders, contains the descriptive phrase "... energy is provided...
and the ultimate source of this energy appears to be the zero-point
radiation of the vacuum continuum."
Another intriguing possibility is provided by the phenomenon of
sonoluminescence, bubble collapse in an ultrasonically-driven fluid which
is accompanied by intense, sub-nanosecond light radiation. Although the
jury is still out as to the mechanism of light generation, Nobelist Julian
Schwinger has argued for a Casimir interpretation. Possibly related
experimental evidence for excess heat generation in ultrasonically-driven
cavitation in heavy water is claimed in an EPRI Report by George and
Stringham of E-Quest Sciences, although attributed to a nuclear micro-
fusion process. Work is under way in our laboratory to see if this claim
can be replicated.
Yet another proposal for ZPE extraction is described in a patent issued to
Mead and Nachamkin. The approach proposes the use of resonant dielectric
spheres, slightly detuned from each other, to provide a beat-frequency
downshift of the more energetic high-frequency components of the ZPE to a
more easily captured form. We are discussing the possibility of a
collaborative effort between us to determine whether such an approach is
Finally, an approach utilizing micro-cavity techniques to perturb the
ground state stability of atomic hydrogen is under consideration in our
lab. It is based on a 1987 paper of mine in which I put forth the
hypothesis that the nonradiative nature of the ground state is due to a
dynamic equilibrium in which radiation emitted due to accelerated electron
ground state motion is compensated by absorption from the ZPE.
If this hypothesis is true, there exists the potential for energy
generation by the application of the techniques of so-called cavity quantum
electrodynamics QED. In cavity QED, excited atoms are passed through
Casimir-like cavities whose structure suppresses electromagnetic cavity
modes at the transition frequency between the atom's excited and ground
The result is that the so-called "spontaneous" emission time is lengthened
considerably (for example, by factors of ten), simply because spontaneous
emission is not so spontaneous after all, but rather is driven by vacuum
fluctuations. Eliminate the modes, and you eliminate the zero-point
fluctuations of the modes, hence suppressing decay of the excited state.
As stated in an April 1993 Scientific American review article on cavity
QED, "An excited atom that would ordinarily emit a low-frequency photon
cannot do so, because there are no vacuum fluctuations to stimulate its
In its application to energy generation, mode suppression would be used to
perturb the hypothesized dynamic ground-state absorption/emission balance
to lead to energy release (patent pending).
An example in which Nature herself may have taken advantage of energetic
vacuum effects is discussed in a model published by ZPE colleagues A. Rueda
of California State University at Long Beach, B. Haisch of Lockheed-Martin,
and D. Cole of IBM. In a paper published in the Astrophysical Journal in
1995, they propose that the vast reaches of outer space constitute an ideal
environment for ZPE acceleration of nuclei and thus provide a mechanism for
"powering up" cosmic rays. Details of the model would appear to account
for other observed phenomena as well, such as the formation of cosmic
This raises the possibility of utilizing a "sub-cosmic-ray" approach to
accelerate protons in a cryogenically-cooled, collision-free vacuum trap
and thus extract energy from the vacuum fluctuations by this mechanism.
THE VACUUM AS THE SOURCE OF GRAVITY AND INERTIA
What of the fundamental forces of gravity and inertia that we seek to
overcome in space travel? We have phenomenological theories that describe
their effects (Newton's Laws and their relativistic generalizations), but
what of their origins?
The first hint that these phenomena might themselves be traceable to roots
in the underlying fluctuations of the vacuum came in a 1967 study published
by the well-known Russian physicist Andrei Sakharov. Searching to derive
Einstein's phenomenological equations for general relativity from a more
fundamental set of assumptions, Sakharov came to the conclusion that the
entire panoply of general relativistic phenomena could be seen as induced
effects brought about by changes in the quantum-fluctuation energy of the
vacuum due to the presence of matter.
In this view the attractive gravitational force is more akin to the induced
Casimir force discussed above, than to the fundamental inverse square law
force between charged particles with which it is often compared. Although
speculative when first introduced by Sakharov, this hypothesis has led to a
rich and ongoing literature (including a contribution of my own in 1989) on
quantum-fluctuation-induced gravity, a literature that continues to yield
deep insight into the role played by vacuum forces.
Given an apparent deep connection between gravity and the zero-point
fluctuations of the vacuum, a similar connection must exist between these
self-same vacuum fluctuations and inertia. This is because it is an
empirical fact that the gravitational and inertial masses have the same
value, even though the underlying phenomena are quite disparate.
Why, for example, should a measure of the resistance of a body to being
accelerated, even if far from any gravitational field, have the same value
that is associated with the gravitational attraction between bodies?
Indeed, if one is determined by vacuum fluctuations, so must the other.
To get to the heart of inertia, consider a specific example in which you
are standing on a train in the station. As the train leaves the platform
with a jolt, you could be thrown to the floor. What is this force that
knocks you down, seemingly coming out of nowhere?
This phenomenon, which we conveniently label inertia and go on about our
physics, is a subtle feature of the universe that has perplexed generations
of physicists from Newton to Einstein. Since in this example the sudden
disquieting imbalance results from acceleration "relative to the fixed
stars," in its most provocative form one could say that it was the "stars"
that delivered the punch. This key feature was emphasized by the Austrian
philosopher of science Ernst Mach, and is now known as Mach's Principle.
Nonetheless, the mechanism by which the stars might do this deed has eluded
Addressing this issue in a 1994 paper entitled "Inertia as a Zero-Point
Field Lorentz Force," Haisch, Rueda and I were successful in tracing the
problem of inertia and its connection to Mach's Principle to the ZPE
properties of the vacuum.
In a sentence, although a uniformly moving body does not experience a drag
force from the (Lorentz-invariant) vacuum fluctuations, an accelerated body
meets a resistance (force) proportional to the acceleration.
By accelerated we mean, of course, accelerated relative to the fixed stars.
It turns out that an argument can be made that the quantum fluctuations of
distant matter structure the local vacuum-fluctuation frame of reference
(see Puthoff, "Source...," 1989). Thus, in the example of the train the
punch was delivered by the wall of vacuum fluctuations acting as a proxy
for the fixed stars through which one attempted to accelerate.
The implication for space travel is this: Given the evidence generated in
the field of cavity QED (discussed above), there is experimental evidence
that vacuum fluctuations can be altered by technological means. This leads
to the corollary that, in principle, gravitational and inertial masses can
also be altered.
The possibility of altering mass with a view to easing the energy burden of
future spaceships has been seriously considered by the Advanced Concepts
Office of the Propulsion Directorate of the Phillips Laboratory at Edwards
Air Force Base. Gravity researcher Robert Forward accepted an assignment
to review this concept. His deliverable product was to recommend a broad,
multi-pronged effort involving laboratories from around the world to
investigate the inertia model experimentally.
After a one-year investigation Forward finished his study and submitted his
report to the Air Force, who published it under the title Mass Modification
Experiment Definition Study. The Abstract reads in part:
".... Many researchers see the vacuum as a central ingredient of 21st-
Century physics. Some even believe the vacuum may be harnessed to provide
a limitless supply of energy. This report summarizes an attempt to find an
experiment that would test the Haisch, Rueda and Puthoff (HRP) conjecture
that the mass and inertia of a body are induced effects brought about by
changes in the quantum-fluctuation energy of the vacuum.... It was
possible to find an experiment that might be able to prove or disprove that
the inertial mass of a body can be altered by making changes in the vacuum
surrounding the body."
With regard to action items, Forward in fact recommends a ranked list of
not one but four experiments to be carried out to address the ZPF-inertia
concept and its broad implications. The recommendations included
investigation of the proposed "sub-cosmic-ray energy device" mentioned
earlier, and the investigation of an hypothesized "inertia-wind" effect
proposed by our laboratory and possibly detected in early experimental work
by Forward and Miller, though the latter possibility is highly speculative
at this point.
ENGINEERING THE VACUUM FOR "WARP DRIVE"
Perhaps one of the most speculative, but nonetheless scientifically-
grounded, proposals of all is the so-called Alcubierre Warp Drive. Taking
on the challenge of determining whether Warp Drive a la Star Trek was a
scientific possibility, general relativity theorist Miguel Alcubierre of
the University of Wales set himself the task of determining whether faster-
than-light travel was possible within the constraints of standard theory.
Although such clearly could not be the case in the flat space of special
relativity, general relativity permits consideration of altered spacetime
metrics where such a possibility is not a priori ruled out.
Alcubierre's further self-imposed constraints on an acceptable solution
included the requirements that no net time distortion should occur
(breakfast on Earth, lunch on Alpha Centauri, and home for dinner with your
wife and children, not your great-great-great grandchildren), and that the
occupants of the spaceship were not to be flattened against the bulkhead by
A solution meeting all of the above requirements was found and published by
Alcubierre in Classical and Quantum Gravity in 1994. The solution
discovered by Alcubierre involved the creation of a local distortion of
spacetime such that spacetime is expanded behind the spaceship, contracted
ahead of it, and yields a hypersurfer-like motion faster than the speed of
light as seen by observers outside the disturbed region. In essence, on
the outgoing leg of its journey the spaceship is pushed away from Earth and
pulled towards its distant destination by the engineered local expansion of
(For follow-up on the broader aspects of "metric engineering" concepts, one
can refer to a paper published by myself in Physics Essays in 1996.)
Interestingly enough, the engineering requirements rely on the generation
of macroscopic, negative-energy-density, Casimir-like states in the quantum
vacuum of the type discussed earlier. Unfortunately, meeting such
requirements is beyond technological reach without some unforeseen
breakthrough, as emphasized by Pfenning and Ford in a recently submitted
Related, of course, is the knowledge that general relativity permits the
possibility of wormholes, topological tunnels which in principle could
connect distant parts of the universe, a cosmic subway so to speak.
Publishing in the American Journal of Physics in 1988, theorists Morris and
Thorne initially outlined in some detail the requirements for traversible
wormholes and have found that, in principle, the possibility exists
provided one has access to Casimir-like, negative-energy-density quantum
vacuum states. This has led to a rich literature, summarized recently in a
1996 book by Matt Visser of Washington University, St. Louis.
Again, the technological requirements appear out of reach for the
foreseeable future, perhaps awaiting new techniques for cohering the ZPE
vacuum fluctuations in order to meet the energy-density requirements.
We began this discussion with the question: "Can the vacuum be engineered
for spaceflight applications?" The answer is: "In principle, yes."
However, engineering-wise it is clear that there is a long way to go.
Given the cliche "a journey of 1000 miles begins with the first steps," it
is also clear that we can take those first steps now in the laboratory.
Given that Casimir and related effects indicate the possibility of tapping
the enormous residual energy in the vacuum-fluctuation ZPE, and the
demonstration in cavity QED that portions of the ZPE spectrum can be
manipulated to produce macroscopic technological effects such as the
inhibition of spontaneous emission of excited states in quantum systems, it
would appear that the first steps along this path are visible.
This, combined with newly-emerging concepts of the relationship of gravity,
inertia and warp drive to properties of the vacuum as a manipulable medium,
indicate yet further reaches of possible technological development,
although requiring yet unforeseen breakthroughs with regard to the
possibility of engineering vacuum fluctuations to produce desired results.
Where does this leave us? As we peer into the heavens from the depth of
our gravity well, hoping for some "magic" solution that will launch our
spacefarers first to the planets and then to the stars, we are reminded of
Arthur C. Clarke's phrase that highly-advanced technology is essentially
indistinguishable from magic. Fortunately, such magic appears to be
waiting in the wings of our deepening understanding of the quantum vacuum
in which we live.
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