Tau Zero and Breakthrough Spaceship Propulsion

In the mainstream, propulsion science does not recognize UFO propulsion technology per se, (Bob Bigelow not withstanding), but there are several theories being bandied about and while interstellar travel just might occur before we become a Kardashev Level One Civilization in around two hundred years (approx. 2200 ACE) , the chances of practical interstellar propulsion being found soon are nil.

From Centauri Dreams:

Speaking at last fall’s International Astronautical Congress in Prague, Tau Zero founder Marc Millis offered a condensed summary of the present state of the art in advanced propulsion physics, summarizing a variety of approaches and next-step questions from the book he co-edited with Eric Davis called Frontiers of Propulsion Science (2009). He’s now written a paper based on the presentation. It’s a useful distillation of an extremely detailed work (739 pages) and well worth scanning now that Millis has made it available on the arXiv site.

Quite a few propulsion concepts have gone through the early stages of the scientific process, with problems defined, data being collected and hypotheses formulated, and Millis also refers to those cases where ideas have progressed into the testing stage. He’s fascinated with the idea of using investigations into broad issues of cosmology to focus in on something far more utilitarian, the possible relevance of new observations for spaceflight. From the paper:

While general science continues to assess cosmological data regarding its implications for the birth and fate of the universe, a spaceflight focus will cast these observations in different contexts, offering insights that might otherwise be overlooked from the curiosity-driven inquiries alone. Homework problems to help teach general relativity now include warp drives and traversable wormholes. Even if there are no spaceflight breakthroughs to be found, adding the inquiry of spaceflight expands our ability to decipher the lingering mysteries of the universe.

Focus on the ‘Space Drive’

The approaches gathered in Frontiers of Propulsion Science are too numerous to list here, but let’s focus for a moment on the issue of space drive physics. A space drive is the umbrella term used to describe the interactions between a vehicle and surrounding space to induce motion, the key point being that such a technology, if ever developed, would eliminate the need for propellant. That’s a big issue — if we could move a craft in this way, we would be dropping the energy requirements from exponential to squared functions of trip velocity, opening up a wide range of mission possibilities we simply cannot achieve with rocketry or space sails.

Notice that the space drive is fundamentally different from what is more and more known as a ‘warp’ drive, the point being that the space drive interacts with spacetime rather than warping spacetime. Quoting Millis again:

Warp drives and wormholes are rooted in the Riemannian geometry of general relativity, where sufficient energy densities can warp spacetime analogously to how a huge gravitational mass bends spacetime. In contrast, most space drive concepts begin with Newtonian representations where the operative goal is to interact with reaction mass embedded in the properties of spacetime. This also implies, therefore, that space drive concepts will be light-speed limited since they operatewithin spacetime.

In other words, a warping of spacetime, if possible, would allow the craft to take advantage of the fact that there is no speed-of-light restriction when it comes to the expansion of spacetime itself (a notion that draws on cosmic inflation in the Big Bang era). The space drive is a different animal, and it compels a different kind of research. The primary issues are conservation of momentum and net external thrust, with the concept raising huge questions about the sources of inertial frames, the nature of the quantum vacuum energy, and the physics of photon momentum in media.

Studying these theories are nice and could provide a foundation of research for the next two hundred years ( like Jules Verne’s sci-fi stories did for our world ), but as a commenter posted on this particular thread: “Our top priority should be to find a really cheap way to get out of the gravity well. Cost is killing space flight.”

Amen to that.

Breakthrough Concepts: A Propulsion Overview