Take a look at the image below. It’s a jet coming off the quasar 3C273. I call your attention to the length of this jet, some 100,000 light years, which is roughly the distance across the Milky Way. Jeff Greason pointed out at the Montreal symposium of the Interstellar Research Group that images like this suggest it may be possible for humans to produce ‘pinched’ relativistic electron jets over the much smaller distances needed to propel a spacecraft out of the Solar System. This is an intriguing image if you’re interested in high-energy beams pushing payloads to nearby stars. Greason is a self-described ‘serial entrepreneur,’ the holder of some 29 patents and chief technologist of Electric Sky, which is all about beaming energy to craft much closer to home. But he moonlights as chairman of the Tau Zero Foundation and is a well known figure in interstellar studies. Placing beaming into context is a useful exercise, as it suggests alternative ways to generate and use a beam. In all of...

Breakthrough Starshot’s concept for a flyby of Alpha Centauri would reach its destination in a single human generation. We’ve discussed sail materials in the last couple of posts, but let’s step back to the overview. Using a powerful ground-based laser, we illuminate a sail on the forward side of which are embedded instruments for communications, imaging and whatever we choose to carry. We need a sail that is roughly 4 meters by 4 meters, and one that weighs no more than a single gram. As Richard Norte pointed out to the Interstellar Research Group’s Montreal symposium (video here), a US penny weighs 2.5 grams, which gives an idea what we are up against. We need a payload at gram-scale and a sail that is itself no more than a gram. Obviously our sail must be of nanoscale thickness, and able to take a beating, for we’re going to light it up for 10 minutes with that laser beam to drive it to 20 percent of lightspeed. We’re engineering, then, in the realm of nanotechnology, but working...

The science fiction trope that often comes to mind in conjunction with the interstellar ark idea is of the crew that has lost all sense of the mission. Brian Aldiss’ Non-Stop (1958), published in the US as Starship, is a classic case of a generation ship that has become the entire world. The US title, of course, gave away the whole plot, which is sort of ridiculous. Have a look at the British cover, which leaves the setting mysterious for most of the book, and the American one, which blatantly tells you what’s going on. I wonder what Aldiss thought of this. Be that as it may, interstellar arks are conceived as having large crews and taking a lot of time to move between stars, usually on the order of thousands of years. We can trace the concept in the scientific literature back to Les Shepherd’s famous 1952 paper on human interstellar travel, a key paper in the evolution of the field. An interesting adaptation of the paper appeared in Science Fiction Plus in April of the following...

A material called aerographite offers options for solar sails that transcend the capabilities of both beryllium and graphene, the latter being the most recent candidate for fast sail missions outside the Solar System. Developed at the Technical University of Hamburg and refined by researchers at the University of Kiel, aerographite came to the attention of the interstellar community in 2020 thanks to a groundbreaking paper by René Heller (Max Planck Institute for Solar System Research, Göttingen), working with co-authors Guillem Anglada-Escudé (Institut de Ciencies Espacials, Barcelona), Michael Hippke (Sonneberg Observatory, Germany) and Pierre Kervella (Observatoire de Paris). I’ve written about aerographite before, in Aerographite: An Advance in Sail Materials with Deep Space Implications and Solar Sails: Deeper into the Aerographite Option, both of which are in the archives along with several other posts on the subject. But here I need to pause for a brief administrative moment:...

One of the great problems of lightsail concepts for interstellar flight is the need to decelerate. Here I’m using lightsail as opposed to ‘solar sail’ in the emerging consensus that a solar sail is one that reflects light from our star, and is thus usable within the Solar System out to about 5 AU, where we deal with the diminishment of photon pressure with distance. Or we could use the Sun with a close solar pass to sling a solar sail outbound on an interstellar trajectory, acknowledging that once our trajectory has been altered and cruise velocity obtained, we might as well stow the now useless sail. Perhaps we could use it for shielding in the interstellar medium or some such. A lightsail in today’s parlance defines a sail that is assumed to work with a beamed power source, as with the laser array envisioned by Breakthrough Starshot. With such an array, whether on Earth or in space, we can forgo the perihelion pass and simply bring our beam to bear on the sail, reaching much higher...