The Breakthrough Propulsion Physics Project (BPP) was a

research project Research is creative and systematic work undertaken to increase the stock of knowledge. It involves the collection, organization, and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness to ...

funded by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

from 1996 to 2002 to study various proposals for

revolutionary A revolutionary is a person who either participates in, or advocates for, a revolution. The term ''revolutionary'' can also be used as an adjective to describe something producing a major and sudden impact on society. Definition The term—bot ...

methods of

spacecraft propulsion Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric e ...

that would require breakthroughs in physics before they could be realized. The project ended in 2002, when the Advanced Space Transportation Program was reorganized and all speculative research (less than

Technology readiness level Technology readiness levels (TRLs) are a method for estimating the maturity of technologies during the acquisition phase of a program. TRLs enable consistent and uniform discussions of technical maturity across different types of technology. TR ...

3) was cancelled. During its six years of operational funding, this program received a total investment of $1.2 million. The Breakthrough Propulsion Physics project addressed a selection of "incremental and affordable" research questions towards the overall goal of propellantless propulsion, hyperfast travel, and breakthrough propulsion methods. It selected and funded five external projects, two in-house tasks and one minor grant. At the end of the project, conclusions into fourteen topics, including these funded projects, were summarized by program manager Marc G. Millis. Of these, six research avenues were found to be nonviable, four were identified as opportunities for continued research, and four remain unresolved.

Non-viable approaches

One in-house experiment tested the Schlicher thruster antenna, claimed by Schlicher to generate thrust. No thrust was observed. Another experiment examined a gravity shielding mechanism claimed by Podkletnov and Nieminen. Experimental investigation on the BPPP and other experiments found no evidence of the effect. Research on quantum tunneling was sponsored by the BPPP. It was concluded that this is not a mechanism for faster-than-light travel. Other approaches categorized as non-viable are oscillation thrusters and gyroscopic antigravity, Hooper antigravity coils, and coronal blowers.

Unresolved approaches

A theoretical examination of additional atomic

energy levels A quantum mechanics, quantum mechanical system or particle that is bound state, bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical mechanics, classical pa ...

(deep Dirac levels) was carried out. Some states were ruled out, but the problem remains unsolved. Experiments tested Woodward’s

theory A theory is a systematic and rational form of abstract thinking about a phenomenon, or the conclusions derived from such thinking. It involves contemplative and logical reasoning, often supported by processes such as observation, experimentation, ...

of inducing transient inertia by electromagnetic fields. The small effect could not be confirmed. Woodward continued refining the experiments and theory. Independent experiments also remained inconclusive. A possible torsion-like effect in the coupling between electromagnetism and spacetime, which may ultimately be useful for propulsion, was sought in experiments. The experiments were insufficient to resolve the question. Other theories listed in Millis's final assessment as unresolved are Abraham–Minkowski electromagnetic momentum, interpreting inertia and gravity quantum vacuum effects, and the Podkletnov force beam.

Space drives

One of the eight tasks funded by the BPP program was to define a strategy towards space drives. As a motivation, seven examples of hypothetical space drives were described at the onset of the project. These included the gravity-based pitch drive, bias drive, disjunction drive and diametric drive; the

Alcubierre drive The Alcubierre drive () is a speculative warp drive idea according to which a spacecraft could achieve apparent faster-than-light travel by contracting space in front of it and expanding space behind it, under the assumption that a configurabl ...

; and the vacuum energy based differential sail. The project then considered the mechanisms behind these drives. At the end of the project, three mechanisms were identified as areas for future research. One considers the possibility of a reaction mass in seemingly empty space, for example in

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...

, or

zero-point energy Zero-point energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly Quantum fluctuation, fluctuate in their lowest energy state as described by the Heisen ...

. Another approach is to reconsider

Mach's principle In theoretical physics, particularly in discussions of gravitation theories, Mach's principle (or Mach's conjecture) is the name given by Albert Einstein to an imprecise hypothesis often credited to the physicist and philosopher Ernst Mach. The ...

and

Euclidean space Euclidean space is the fundamental space of geometry, intended to represent physical space. Originally, in Euclid's ''Elements'', it was the three-dimensional space of Euclidean geometry, but in modern mathematics there are ''Euclidean spaces ...

. A third research avenue that might ultimately prove useful for spacecraft propulsion is the coupling of fundamental forces on sub-atomic scales.

Quantum vacuum energy experiments

One topic of investigations was the use of the

field. As the Heisenberg

uncertainty principle The uncertainty principle, also known as Heisenberg's indeterminacy principle, is a fundamental concept in quantum mechanics. It states that there is a limit to the precision with which certain pairs of physical properties, such as position a ...

implies that there is no such thing as an exact amount of energy in an exact location, vacuum fluctuations are known to lead to discernible effects such as the

Casimir effect In quantum field theory, the Casimir effect (or Casimir force) is a physical force (physics), force acting on the macroscopic boundaries of a confined space which arises from the quantum fluctuations of a field (physics), field. The term Casim ...

. The differential sail is a speculative drive, based on the possibility of inducing differences in the pressure of vacuum fluctuations on either side of a sail-like structure — with the pressure being somehow reduced on the forward surface of the sail, but pushing as normal on the aft surface — and thus propel a vehicle forward. The Casimir effect was investigated experimentally and analytically under the Breakthrough Propulsion Physics project. This included the construction of MicroElectroMechanical (MEM) rectangular Casimir cavities. Theoretical work showed that the effect could be used to create net forces, although the forces would be extremely small. At the conclusion of the project, the Casimir effect was categorized as an avenue for future research.

Tau Zero Foundation

After funding ended, program manager Marc G. Millis was supported by NASA to complete documentation of results. The book ''Frontiers of Propulsion Science'' was published by the

AIAA The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering. The AIAA is the U.S. representative on the International Astronautical Federation and the International Council of ...

in February 2009, M. Millis and E. Davis, ''Frontiers of Propulsion Science'', AIAA, Progress in Astronautics & Aeronautics Vol 227, 2009. providing a deeper explanation of several propulsion methods. Following program cancellation in 2002, Millis and others founded the Tau Zero Foundation.

References