## AlcubierreEdit

Main article: Alcubierre drive

The Alcubierre drive, also called the warp drive, is a proposal, originally due to the physicist Miguel Alcubierre, who proved mathematically that movement at speeds greater than the speed of light was possible without locally exceeding the speed of light. NASA has an experiment which consists of White–Juday warp-field interferometer utilizing a 633 nm HeNe laser beam which is split in two. One beam passes through an electromagnetic field which attempts to distort space enough to see a phase difference between the two beams when they are brought back together. NASA scientist Harold White indicates that a difference of only one part in ten million would be enough to prove the feasibility of the concept. To many people, this concept is reminiscent of the fictional "warp drive" from the science fiction series Star Trek.

## Differential sailEdit

The differential sail was another speculative proposal, which appealed to the zero-point energy field. As the Heisenberg uncertainty principle 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. The differential sail was a speculation that it might be possible to induce differences in the pressure of vacuum fluctuations on either side of sail-like structure—with the pressure being somehow reduced on the forward surface of the sail, but pushing as normal on the raft surface—and thus propel a vehicle forward. [1]

A quantum vacuum plasma thruster is an example of this type of propulsion source.

## LegacyEdit

After funding for research ended, the Project's founder and manager, Marc G. Millis, was supported by NASA to complete the documentation of results. The culmination of that work is the book, Frontiers of Propulsion Science, which was published in February 2009, by the American Institute for Aeronautics and Astronautics (AIAA). Chapter 3 (Prerequisites for Space Drive Science) provides refinements and deeper explanation of the following hypothetical "space drive" propulsion methods: diametric drive, pitch drive, bias drive, disjunction drive, and three variations of differential sails.

After the BPP was canceled in 2002, some former members, including manager Marc G. Millis, founded the Tau Zero Foundation (named after the novel of the same name), an organization that advocates research into interstellar travel. The new organization is not affiliated with NASA. Millis retired from NASA on February 3, 2010, and continues to pursue similar research via Tau Zero.