05-08-2013, 12:05 PM
(This post was last modified: 05-29-2013, 09:17 AM by Sim Koning.)

The Pdf on the NASA site was taken down, but I still have his paper on my computer (it was freely accessible on the NASA site). This is the bit I found most interesting. His version acts as a FTL "booster" for a more conventional propulsion system. Basically, he seems to be saying that a fusion rocket that travels at *edit* .2c will be boosted up to 20c *edit*.

"The concept of operations as described by Alcubierre is that the spacecraft would depart the point of

origin (e.g. earth) using some conventional propulsion system and travel a distance d, then bring the

craft to a stop relative to the departure point. The field would be turned on and the craft would zip off

to its stellar destination, never locally breaking the speed of light, but covering the distance in an

arbitrarily short time period of time just the same. The field would be turned off a similar standoff

distance from the destination, and the craft would finish the journey conventionally. This approach

would allow a journey to say Alpha Centauri as measured by an earth bound observer (and spacecraft

clocks) measured in weeks or months, rather than decades or centuries.

A paradox identified in [6] is an issue that arises due to the symmetry of the energy density about the x

= xs surface. When the energy density is initiated, the choice in direction of the +x-axis is mathematically

arbitrary, so how does the spacecraft “know” which direction to go? Comparing Figure 1 to Figure 2

visually displays the asymmetry of the York Time and the symmetry of the energy density. Both sets of

three frames were purposely aligned to make direct comparison easier. This asymmetry/symmetry

paradox issue can be potentially resolved when considering the canonical form of the metric derived by

using a gauge transformation in [6] as shown in equation 4.

Using this new information, a modified concept of operations is proposed that may resolve the

asymmetry/symmetry paradox. In this modified concept of operations, the spacecraft departs earth and

establishes an initial sub-luminal velocity vi, then initiates the field. When active, the field’s boost acts on

the initial velocity as a scalar multiplier resulting in a much higher apparent speed, <veff>= γ vi as

measured by either an earth bound observer or an observer in the bubble. Within the shell thickness of

the warp bubble region, the spacecraft never locally breaks the speed of light and the net effect as seen

by earth/ship observers is analogous to watching a film in fast forward. Consider the following to help

illustrate the point – assume the spacecraft heads out towards Alpha Centauri and has a conventional

propulsion system capable of reaching 0.1c. The spacecraft initiates a boost field with a value of 100

which acts on the initial velocity resulting in an apparent speed of 10c. The spacecraft will make it to

Alpha Centauri in 0.43 years as measured by an earth observer and an observer in the flat space-time

volume encapsulated by the warp bubble. While this line of reason seems to resolve the paradox, it also

suggests that the York Time may not be the driving phenomenon, rather a secondary result. In this

physical explanation of the mathematics, the York Time might be thought of as perhaps a Doppler strain

on space as this spherical region is propelled through space. A pedestrian analog to use to help envision

this concept would be to consider the hydrodynamic pressure gradients that form around a spherical

body moving through a fluid – the front hemisphere has a high pressure region while the rear

hemisphere has a low pressure region. Analogously, the warp bubble travelling through space-time

causes space to pile up (contract) in front of the bubble, and stretch out (expand) behind the bubble.

"The concept of operations as described by Alcubierre is that the spacecraft would depart the point of

origin (e.g. earth) using some conventional propulsion system and travel a distance d, then bring the

craft to a stop relative to the departure point. The field would be turned on and the craft would zip off

to its stellar destination, never locally breaking the speed of light, but covering the distance in an

arbitrarily short time period of time just the same. The field would be turned off a similar standoff

distance from the destination, and the craft would finish the journey conventionally. This approach

would allow a journey to say Alpha Centauri as measured by an earth bound observer (and spacecraft

clocks) measured in weeks or months, rather than decades or centuries.

A paradox identified in [6] is an issue that arises due to the symmetry of the energy density about the x

= xs surface. When the energy density is initiated, the choice in direction of the +x-axis is mathematically

arbitrary, so how does the spacecraft “know” which direction to go? Comparing Figure 1 to Figure 2

visually displays the asymmetry of the York Time and the symmetry of the energy density. Both sets of

three frames were purposely aligned to make direct comparison easier. This asymmetry/symmetry

paradox issue can be potentially resolved when considering the canonical form of the metric derived by

using a gauge transformation in [6] as shown in equation 4.

Using this new information, a modified concept of operations is proposed that may resolve the

asymmetry/symmetry paradox. In this modified concept of operations, the spacecraft departs earth and

establishes an initial sub-luminal velocity vi, then initiates the field. When active, the field’s boost acts on

the initial velocity as a scalar multiplier resulting in a much higher apparent speed, <veff>= γ vi as

measured by either an earth bound observer or an observer in the bubble. Within the shell thickness of

the warp bubble region, the spacecraft never locally breaks the speed of light and the net effect as seen

by earth/ship observers is analogous to watching a film in fast forward. Consider the following to help

illustrate the point – assume the spacecraft heads out towards Alpha Centauri and has a conventional

propulsion system capable of reaching 0.1c. The spacecraft initiates a boost field with a value of 100

which acts on the initial velocity resulting in an apparent speed of 10c. The spacecraft will make it to

Alpha Centauri in 0.43 years as measured by an earth observer and an observer in the flat space-time

volume encapsulated by the warp bubble. While this line of reason seems to resolve the paradox, it also

suggests that the York Time may not be the driving phenomenon, rather a secondary result. In this

physical explanation of the mathematics, the York Time might be thought of as perhaps a Doppler strain

on space as this spherical region is propelled through space. A pedestrian analog to use to help envision

this concept would be to consider the hydrodynamic pressure gradients that form around a spherical

body moving through a fluid – the front hemisphere has a high pressure region while the rear

hemisphere has a low pressure region. Analogously, the warp bubble travelling through space-time

causes space to pile up (contract) in front of the bubble, and stretch out (expand) behind the bubble.