# Breakthrough Propulsion Physics Program

The Breakthrough Propulsion Physics Program is a research program established in 1996 by NASA to develop revolutionary methods of spacecraft propulsion that, while they may be possible in the future, require breakthroughs in physics before they could be implemented, which may be seen as a sign of wishful thinking. Some examples include the Diametric drive, the Pitch drive, the Bias drive, the Alcubierre drive, the Disjunction drive, and the Differential sail.

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## Diametric drive

The diametric drive functions by creating an asymmetric field around itself. Under such a field, the side of the field which creates more force on the spacecraft will accelerate the spacecraft in the direction of the force. It is unknown whether it is even physically possible to create such a field. One possibility is through the use of particles of negative mass. Stability issues arise in some such designs, however the huge constant acceleration without need for fuel or reaction mass is certainly an attractive idea.

## Pitch drive

The pitch drive is a diametric drive which uses the principle of a disjoint field (as in the disjunction drive) to eliminate the need for the field to be generated on the spacecraft itself. A type of pitch drive is the bias drive.

## Bias drive

The bias drive is a pitch drive that functions by altering the gravitational constant G in front of and behind the craft. One problem with this concept is that it would create a singularity in the field's gradient located inside the vehicle.

## Disjunction drive

The disjunction drive is based on the possibility of creating a field disjoint from the object that created it. For a simple example, picture a gigantic electromagnet a fraction of a light year away from an iron plate. The electromagnet is turned on briefly, then turned off, emitting a pulse of electromagnetic radiation in the process. By the time the field reaches the plate, the magnet could even have been destroyed. Does the plate still experience a force? If so, it no longer has an object to impart an opposite force against. Similar questions arise with other forces, such as gravity: could a gravitational wave be created disjoint from its source in such a manner? It is currently unknown whether this is possible or not.

## Alcubierre drive

The Alcubierre drive, also called the warp drive is a proposal by the physicist Miguel Alcubierre. For more information, see Alcubierre drive.

## Differential sail

The differential sail is a method of propulsion that operates by tapping into 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 discernable effects such as the Casimir effect. The differential sail is a concept that would utilize cosmic background radiation as its source of varying energy to create a gradient in pressure in space.

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