Observational Signatures of Self-Destructive Civilisations
arxiv.org
arxiv.org
They seem to say that given Fermi's paradox and the possibility that most civilizations self-annihilate, this is actually a good way to do SETI. Makes sense.
Quite the opposite, that's one of the most delta-v expensive trajectories to embark upon. In fact from earth it's about twice as expensive as leaving the solar system.
For interstellar trajectories you can use stars for gravity assists, but I'm not sure that would work for escaping the Sun. There, you would want to use the Oberth maneuver, where you get into an elliptical orbit around the sun and then fire your engines at perihelion to raise your orbit to a parabolic or hyperbolic trajectory.
In any case the Voyagers both used gravity assists around the gas giants (Voyager 2 used all four, while Voyager 1 just used Jupiter and Saturn because NASA decided to swing past Titan and didn't have enough propellant left to resume the Grand Tour course).
That said, if, for example, humans kill themselves off with a climate change it would have very little external signature.
So if the likeliest outcomes of industrial civilization are environmental self-destruct, self immolation in war, or "subliming" to something we can't imagine, then this would handily explain the Fermi paradox.
Or have I missed something?
Based on the number of people lost in their phones on BART, the streets and meetings, I'd say we're already well on our way to subliming ourselves.