AAWSAP DIRD, Advanced Space Propulsion Based on Vacuum (Spacetime Metric) Engineering, March 2010

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GRAVITY/ANTIGRAVITY/PROPULSION EFFECTS
In the GR ansatz gravitational-type forces derive from the spacetime metric, whether
determined by natural sources (for example, planetary or stellar masses) or by
advanced metric engineering. Fortunately for our consideration of this topic, discussion
can be carried out solely based on the form of the metric, independent of the specific
mechanisms or dynamics that determine the metric. As one exemplar, consider
Alcubierre's formulation of a "warp drive," a spacetime metric solution of Einstein's GR
field equation (References 2, 22). Alcubierre derived a spacetime metric motivated by
cosmological inflation that would allow arbitrarily short travel times between two distant
points in space. The behavior of the warp drive metric provides for the simultaneous
expansion of space behind the spacecraft and a corresponding contraction of space in
front of the spacecraft (see Figure 3). The warp drive spacecraft would thus appear to
be "surfing on a wave" of spacetime geometry. By appropriate structuring of the metric,
the spacecraft can be made to exhibit an arbitrarily large apparent faster-than-light
speed as viewed by external observers without violating the local speed-of-light
constraint within the spacetime-altered region. Furthermore, the Alcubierre solution
showed that the proper (experienced) acceleration along the spaceship's path would be
zero, and that the spaceship would suffer no time dilation-highly desirable features for
interstellar travel. In order to implement a warp drive, one would have to construct a
"warp bubble" that surrounded the spacecraft by generating a thin shell or surface layer
of exotic matter-that is, a quantum field having negative energy and/or negative
pressure. Although the technical requirements for such are unlikely to be met in the
foreseeable future (Reference 22), the exercise nonetheless serves as a good example
for showcasing attributes associated with manipulation of the spacetime metric at will.
The entire discussion of the possibility of generating a spacetime structure like that of
the Alcubierre warp drive is based simply on assuming the form of a metric (that
is, g,, v) that exhibits desired characteristics. In like manner, arbitrary spacetime metrics
to provide gravity/antigravity/propulsion characteristics can in principle be postulated .
What is required for implementation is to determine appropriate sources for their
generation, a requirement that must be met before advanced spaceship technology
based on vacuum engineering can be realized in practice. The difficulties, challenges,
and options for meeting such requirements can be found in the relevant literature
(Reference 22).
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