A story in The Scotsman discussing how a hyperspace drive might work is in wide circulation, and today I read the feature in New Scientist that it's based on (thanks to Ian Brown for the tip). Under discussion is the possibility of building what is being called a 'hyperspace engine,' one that could get us to Mars in a matter of hours and to the stars within the kind of time frames once demanded of the crews of sailing ships. But to say that the theories behind this drive are controversial is to turn understatement into a virtual art form. Here's what The Scotsman has to say about how such an engine would work: The theoretical engine works by creating an intense magnetic field that, according to ideas first developed by the late scientist Burkhard Heim in the 1950s, would produce a gravitational field and result in thrust for a spacecraft. Also, if a large enough magnetic field was created, the craft would slip into a different dimension, where the speed of light is faster, allowing...

Centauri Dreams recently examined wormholes and their possible survival from the early universe through the mechanism of a negative mass cosmic string. But what exactly is a cosmic string? Here's Lawrence Krauss on the subject: "During a phase transition in materials -- as when water boils, say, or freezes, the configuration of the material's constituent particles changes. When water freezes, it forms a crystalline structure. As crystals aligned in various distances grow, they can meet to form random lines, which create the patterns that looks so pretty on a window in the winter. During a phase transition in the early universe, the configuration of matter, radiation, and empty space (which, I remind you, can carry energy) changes, too. Sometimes during these transitions, various regions of the universe relax into different configurations. As these configurations grow, they too can eventually meet -- sometimes at a point, and sometimes along a line, marking a boundary between the...

What could inflation theory have to do with the Fermi paradox? Quite a lot, if at least one recent paper is to be believed. The question 'where are they' about extraterrestrial visitation becomes even more pointed when faster-than-light technologies move out of the realm of the impossible to something that may be seriously investigated by physicists. Inflation theory, which holds that the early universe underwent a vast expansion as spacetime itself stretched far beyond the velocity of light, opens the door to technologies that might use this effect to create spacefaring civilizations spanning entire galaxies. Just how fast did inflation occur? In a space of time lasting about 10-35 seconds, the universe could have expanded by a factor of 1030 to 10100. As Brian Greene puts it in The Fabric of the Cosmos: An expansion factor of 1030 -- a conservative estimate -- would be like scaling up a molecule of DNA to roughly the size of the Milky Way galaxy, and in a time interval that's much...

When physicist Geoffrey Landis reviewed interstellar concepts at the American Association for the Advancement of Science's 2002 meeting, his wide-ranging presentation considered where we stand on nuclear propulsion, solar and lightsail technologies, and particle-pushed sails. He also addressed the question of the Bussard ramjet, which would use an electromagnetic scoop to collect atoms from the interstellar medium to fuel a fusion reactor. Finding serious problems here (he cites, among other things, the fact that the scoop technology acts more like a brake than an accelerator), Landis went on to consider an alternative: "These problems can be alleviated if, instead of using the ambient interstellar medium, fuel is deliberately emplaced in the path of the spacecraft before flight. In this way, the fuel (probably in the form of small 'pellets') can be chosen to be the optimum composition... The 'runway' of fuel pellets could be emplaced, for example, by a dedicated craft which drops...

What a pleasure to discover that Robert Freitas' Kinematic Self-Replicating Machines is now available online. The 2004 book (from Landes Bioscience of Georgetown TX) is the most comprehensive study of nanotechnology yet written, a compendium of information on self-replicating systems both proposed and experimentally studied. Moreover, it contains a survey of the historical development of nanotechnology, 200 illustrations and over 3000 references to the technical literature. That nanotechnology (and self-replicating systems in particular) could change our ideas of interstellar flight now seems obvious, but not so long ago ago the concept of one machine building another was studied only at the macro-level. Thus Freitas' previous work on a self-reproducing spacecraft he called REPRO. The scientist wrote the concept up in a 1980 issue of the Journal of the British Interplanetary Society, conceiving of a mammoth Daedalus-style spacecraft built in orbit around Jupiter and, like Daedalus,...

Be aware of The Spaceward Foundation's Elevator:2010 program, a challenge award offering a prize for the first laser-powered tether climbing demonstration that can meet specific criteria. A space elevator of the sort discussed in yesterday's entry would send 20-ton elevator cars with about 900 cubic meters of space up a tether at 200 kilometers per hour, a cheap and safe way to reach geostationary orbit. The Spaceward Foundation intends to promote and test the technologies using a balloon-suspended tether several miles high. The Foundation also offers a quick Space Elevator Primer with salient facts and comments about the concept, among them this thought on government inertia: There is no doubt that the promise of the Space Elevator is mind boggling. And here lies the problem - it requires a paradigm shift. 100 years ago, people thought dirigibles were the only way to fly, and heavier-than-air flying machines were an odd-ball idea. Today, there is an almost unbreakable concept that...

If you wanted to reach Alpha Centauri in 40 years, one way to do it would be to boost a spacecraft up to 10 percent of lightspeed as quickly as possible and then let it coast to destination. Or you could do something entirely different: push your payload at constant acceleration halfway to Centauri, turn it around at the halfway point, and perform a uniform deceleration that gets you to into Centauri space with zero speed. To achieve the latter -- no small feat, needless to say -- requires a constant acceleration of 0.0105g. That number comes from the work of Italian physicist and mathematician Claudio Maccone, whose new paper "Radioactive Decay to Propel Relativistic Interstellar Probes Along a Rectilinear Hyperbolic Motion (Rindler Spacetime)" discusses a novel way to design an interstellar probe. Maccone's study of constant acceleration (using what special relativity calls 'hyperbolic motion') shows that it could provide an ideal mission profile if we can find a way to propel a...

If wormholes exist, is it possible to observe one? A fascinating, decade-old paper argues for the possibility, based on the observed phenomenon of mass curving space, which shows up in numerous instances of gravitational lensing. Just as the image of a background object like a distant galaxy can be bent by an intervening mass to produce a magnified image, so wormholes might be detected through their visual effects. But wormholes, remember, are odd beasts. They should display negative mass. The upshot: instead of focusing light like a gravitational lens, a wormhole should diffuse it in all directions. I discussed the possibilities with Geoffrey Landis at Glenn Research Center a couple of years ago. Landis, who worked on the paper "Natural Wormholes as Gravitational Lenses" (Physical Review D, March 15, 1995: pp. 3124-27) with a remarkable team (John Cramer, Robert Forward, Gregory Benford et al.) pointed out that an actual wormhole would not be visible. But if a wormhole passed in...