In my thoughts you would need a super heavy element that creates such a gravitational force that it can warp local space time. You've heard of gravitational lensing where light appear bent around a massive gravitational force? Well my device and its effect would be called space time lensing. Where space time is bent by an exaggerated force of gravity. Have you ever seen the picture with Peter Ustinov and the rubber sheet depicting gravity warping space? Well my device would have an exaggerated mass and gravitational force, reflecting that of the sun. How can you achieve this? You tell lies to the surrounding space time, you tell it very elaborate lies and that space time thinks you have the mass of the sun when you don't. A gravity exaggerator Lynx.
And then you'd have a gigantic mass to accelerate and decelerate, costing you huge amounts of energy. If you have the weight of our sun, you're going to accelerate and decelerate as slowly as our sun would under any given impulse force.
One cannot "lie" to the universe, Nav, nor does space-time "think", your sentient universe blather notwithstanding.
Why use mass to warp space-time when energy will do the same without the concomitant weight?
No, you want to increase energy levels such that the electromagnetic and weak fundamental forces become symmetric (phase change into the electroweak force). This brings back the H
1, H
2 and H
3 Higgs bosons (which at our energy levels underwent quantum mixing via the Higgs mechanism to lend mass to the W
+, W
- and Z
0 bosons) that existed in the earliest moments of the universe.
Then you generate Higgs bosons in a collider. Since you've got the H
0, H
1, H
2 and H
3 Higgs bosons available, you'll be generating doublets via pair production.
Then you want to minimize their quantum vacuum coupling (in a well-shielded Casimir cavity) to slow their spontaneous decay rate, and devise some slow flavor-exchange interaction that violates CP (charge and parity symmetry) such that an asymmetry between the Higgs doublets is created.
My prior idea of forcing a Lorentz transformation, which force the tachyonic Higgs to act on all tensor fields (including the observer's time-like vector field) would slow time in the frame of the spacecraft.
The asymmetry between the Higgs doublet scalars will, when the Higgs undergo decay, translate into a daughter baryon asymmetry.
Then you lower the energy levels to allow the electroweak force to symmetry break back into the weak and electromagnetic force.
The baryonic asymmetry mentioned above would generate a matter-antimatter asymmetry, (this would normally cause dark matter to be manifested from the quantum vacuum to 'balance the equation', but since we've lowered energy levels, only dark energy will manifest... energy levels aren't high enough to manifest dark matter). This mechanism (with dark matter production due to higher universal energy levels) occurring early in the evolution of the universe is postulated to be the reason the universe had about a billionth of its energy converted into invariant mass matter, and the reason dark matter exists.
You let the matter and anti-matter annihilate to generate conventional thrust, and the dark energy provides you a bit of space-time expansion behind your craft, generating that 'wave crest' of space-time upon which your craft is carried.
In effect, you're mimicking the first perceivable moments of the universe to propel your craft.
That'll get you that much closer to c... but you'll still never exceed it, not with a spacecraft made of invariant-mass matter and crewed by invariant-mass matter people, anyway.
Where to get the tremendous amount of energy to make this work? Harvest it via active antennas... those antennas would be mounted at the front of the spacecraft, and their electromagnetic 'footprint' would extend out far ahead of the craft, absorbing energy and thus creating a lower field radiation pressure 'vacuum' ahead of the craft. Thus you've got dark energy and matter/antimatter annihilation pushing the craft and active antennas creating a lower field radiation pressure region ahead of the craft.
Of course, we have the technology right now to only do the above on a small scale... we can design and use active antennas, we can increase energy levels to cause the weak and EM to phase change into the electroweak, we can generate Higgs bosons in a collider, we can cause a Lorentz transformation, we can cause a CP violating flavor-exchange interaction, we can design Casimir cavities... we can't do it on a scale that would push a spacecraft, but it's doable.