While Rod Hyde, Lowell Wood and John Nuckolls were working on laser-induced fusion to drive a starship back in 1972, the range of options for advanced propulsion continued to grow. One we haven't talked about much in these pages is the use of gravitational slingshots in exotic settings. We're used to the concept within the Solar System because spacecraft like Voyager and Galileo have used a 'slingshot' around a planet to alter course and accelerate. But interstellar visionaries like Freeman Dyson have looked further out to imagine other uses for such techniques. In a 1963 paper, Dyson speculated on how an advanced civilization might use a binary star system made up of two white dwarfs. Send a spacecraft into the system for a close pass around one of the stars and, depending on the mass and orbital velocity of the stars, it is thrown out of the binary system at velocities as high as 3000 kilometers per second. But Dyson took the idea even further. His paper, which appeared as a...

Sara Seager's thoughts on who might join a crew bound for Alpha Centauri have had resonance, as witness Dennis Overbye's story Discovery Rekindles Wish for a Journey to the Stars in the New York Times. Overbye, a touchstone in science journalism, has probably been pondering the issue because of Seager's response to his question about Centauri B b. The MIT astronomer laid it out starkly: "I think we should drop everything and send a probe there." Seager is well aware of the issues involved and knows what a project it would be to drive a lightsail -- or some other kind of spacecraft -- up to ten percent of the speed of light. But she has us all thinking about the kind of people who would go on future manned missions (and whether they might wind up changing their minds). Overbye can look back at his high school yearbook, where he finds "Ambition: To go to the stars." These days he's thinking more about what would happen if he really did: Perhaps it is a sign of my age that I think more...

?If you were offered a chance to make an interstellar journey, would you take it? How about a garden-variety trip to low-Earth orbit? I’m often asked questions like this when I make presentations to the public, and I have no hesitation in saying no. Though I’m no longer doing any flight instructing, I used to love flying airplanes, but getting into a rocket and being propelled anywhere is not for me. To each his own: I’m fascinated with deep space and hope many humans go there, and you can count on me to write about their missions and robotic ones as well while keeping my office right here on Earth. The point is, the percentage of people who actually go out and take the incredible journeys and fly the dangerous missions is vanishingly low. But throughout history, there have always been a few intrepid souls who were willing to get into the canoes or the caravels or the biplanes and open up new territories and technologies. Thank God we have the Neil Armstrongs and Sergei Krikalyovs of...

Voyager 1, now 17 light hours from Earth, continues to be my touchstone when asked about getting to Alpha Centauri -- and in the last few days, I've been asked that question a lot. At 17.1 kilometers per second, Voyager 1 would need 74,000 years to reach the blistering orb we now believe to be orbiting Centauri B. Voyager 1 is not the fastest thing we've ever launched -- New Horizons at one point in its mission was moving with greater velocity, though no longer, and the Helios II Solar probe, no longer functional, reaches about 70 kilometers per second at perihelion. But Voyager 1 will be our first craft to reach interstellar space, and it continues to be a measure of how frustratingly far even the nearest stars happen to be. Cautionary notes are needed when a sudden burst of enthusiasm comes to these subjects, as it seems to have done with the discovery of Centauri B b. What we need to avoid, if we've got our eyes on long-term prospects and a sustained effort that may take centuries...

One of the challenges of explaining why a starship project is worth doing even though its final goal may not be realized for a long time is in showing how this work can have an impact on improving things on Earth. Technological spinoffs have acquired a bad name because of the stigma of Teflon and Tang -- NASA hasn't made the strongest case for how advanced work changes lives (and in any case, Teflon and Tang are not actually NASA spinoffs, though they are in the eyes of the public). But work in space can effect profound changes on Earth, and there is every reason to believe that energy breakthroughs in propulsion and power generation could be highly useful in solving our planet's future energy demands. [See the comments for a recent change to this text]. The list can obviously be expanded, as in the case of closed ecologies, which we've been talking about recently in these pages. A long-duration human mission demands attention to environments and their maintenance that will surely...

The continued explorations of our two Voyagers have earned these tough spacecraft the right to be considered an interstellar mission, which is how NASA now describes their journeys. Neither will come anywhere near another star for tens of thousands of years, but in this context 'interstellar' means putting a payload with data return into true interstellar space. Right now the Voyagers are still within the heliosphere, that great bubble opened out around our system by the Sun's solar wind, and the signs are multiplying that a transition is soon to occur. Three measurements are going to mark the boundary crossing, and we're seeing that two out of the three are in a state of rapid change. This JPL news release points out that on July 28, Voyager 1's cosmic ray instrument showed a jump of five percent in the level of galactic cosmic rays the craft was encountering. In the second half of that same day, the level of lower-energy particles flowing from inside the Solar System dropped by...

It's too bad we don't already have a workable Enterprise, that vast near-term rendition of the Star Trek vehicle that a systems engineer named 'Dan' has been talking about on BuildTheEnterprise.org (a site which has been so heavily trafficked in the last 48 hours that it has proven almost inaccessible). What Dan has in mind is the design, down to the smallest level of detail, of a ship powered by three ion propulsion engines that tap on-board nuclear reactors to remain operational. It may not be an antimatter-powered Enterprise, but it's a faithful simulacrum, reflecting its creator's long-lasting interest in the ship that William Shatner once commanded. Dan thinks the new Enterprise could get us to Mars in 90 days, but getting nuclear reactors into low Earth orbit in the first place will be a challenge not only technically but politically, and shielding the crew will also involve a serious amount of mass that has to get lifted. One of the fascinations of this highly detailed site is...

What would you do if you had a spacecraft pushing toward the edge of the Solar System with nothing much to do? The answer is to assign it an extended mission, as we found out with the two Voyagers and their continuing data return that is helping us understand the boundaries of the heliosphere. In the case of New Horizons, NASA's probe to Pluto/Charon, two extended missions may be involved after Pluto, the first being a flyby of one or more Kuiper Belt targets, the second being a further look at what is actually going on where the solar wind meets the interstellar medium. Alan Stern, principal investigator for New Horizons, comments on the possibility in his latest report on the mission, noting that a second extended mission isn't out of the question, and adding that New Horizons won't make it as far as the Voyagers before it runs out of power. But 90 to 100 AU seems a possibility, which would provide a useful supplement to Voyager data. Remember that New Horizons carries two...

by Andreas Hein The immense problems of time, distance and life support invariably mean that when we talk about an interstellar mission, we talk about robotics. But the imaginative team at Icarus Interstellar, which is now setting up projects on everything from beamed lightsails (Project Forward) to pulse propulsion engines (Project Helios), has pushed into the biggest what-if of all, the question of manned missions. And as project leader Andreas Hein reminds us in the following article, a variety of approaches have been suggested for this over the years from which a new concept study can grow. Andreas Hein received his master's degree in aerospace engineering at the Technische Universität München, and is doing his PhD at the same university in the area of space systems engineering at the Institute of Astronautics. He has participated in several mission studies: a lunar gravity measurement mission by EADS and a cubesat mission analysis. During his internship at ESA-ESTEC, he...

Powering up a spacecraft is a lot easier to manage in the Sun-rich environment inside the orbit of Mars than it is out past the orbit of Jupiter. Solar panels provide plenty of power for a satellite in near-Earth orbit, for example, but moving into the outer system invokes the need for RTGs -- radioisotope thermoelectric generators -- powered by radioactive decay. If you read through the specs on the FOCAL mission design presented here last Friday, you saw that this attempt to reach the Sun's gravitational lens would demand 20 RTGs, and thus requires resumed production of plutonium-238. What's happened is that US production of 238Pu was halted as far back as 1988, leaving us with stockpiles that should be sufficient for missions in the pipeline through the end of this decade. That's the view of Leonard Dudzinski, NASA's Radioisotope Thermoelectric Generator program executive, who was speaking at the opening session of the 43rd Lunar and Planetary Science and the Nuclear and Emerging...

Long-time Centauri Dreams readers have learned to tolerate my eccentricities (or, at least, they’re kind enough not to dwell on them). One of them is my love of poking around in old books related to space travel, which is how Benjamin Field’s A Narrative of the Travels and Adventures of Paul Aermont Among the Planets (1873) recently caught my eye. I don’t know much about Field other than that he chose to produce this tale of interplanetary wanderings under a pseudonym, but what’s fun about his tale is that after his journeys to Jupiter, Saturn, Mars and Venus are over, Field’s protagonist returns to Earth to find that the planet is fully fifty years older, though he himself has aged hardly at all. Time dilation, the reader might say, but of course Field wouldn’t have known anything about special relativity. It’s fun to consider, though, how an idea that in 1873 would have been simple fantasy -- that someone might travel at high speed and age at a different rate than those he left...

One of the first things we need to do in terms of interstellar exploration is to get a spacecraft built for the purpose to travel outside the heliosphere and give us solid measurements on the interstellar medium. The Voyagers are doing their best but they were never designed for what has become their interstellar mission, and while we can marvel at their longevity, it's with the knowledge that their resources are few and their years of useful data gradually drawing to an end. Something along the lines of Ralph McNutt's Innovative Interstellar Explorer would do the job nicely, allowing us to sample the environment that much longer missions will have to work in. Lorentz Force Turning The interstellar medium (ISM) is important not just because we have to learn about things like shielding a fast-moving spacecraft and cosmic ray flux but also because we may be able to use some aspects of the medium for deceleration. Yesterday's discussion of magsails reminded me of a 1969 paper by P. C....

Imagine a future in which we manage to reach average speeds in the area of one percent of the speed of light. That would make for a 437-year one-way trip to the Alpha Centauri system, too long for anything manned other than generation ships or missions with crews in some kind of suspended animation. Although 0.01c is well beyond our current capabilities, there is absolutely nothing in the laws of physics that would prevent our attaining such velocities, assuming we can find the energy source to drive the vehicle. And because it seems an achievable goal, it's worth looking at what we might do with space probes and advanced robotics that can move at such velocities. How, in other words, would a spacefaring culture use artificial intelligence and fast probes to move beyond its parent solar system? John Mathews ( Pennyslvania State) looks at the issue in a new paper, with a nod to the work of John von Neumann on self-reproducing automata and the subsequent thoughts of Ronald Bracewell...

Andreas Tziolas, current leader of Project Icarus, gave a lengthy interview recently to The Atlantic's Ross Andersen, who writes about starship design in Project Icarus: Laying the Plans for Interstellar Travel. Icarus encounters continuing controversy over its name, despite the fact that the Icarus team has gone to some lengths to explain the choice. Tziolas notes the nod to Project Daedalus leader Alan Bond, who once referred to "the sons of Daedalus, perhaps an Icarus, that will have to come through and make this a much more feasible design." I like that sense of continuity -- after all, Icarus is the follow-on to the British Interplanetary Society's Project Daedalus of the 1970s, the first serious attempt to engineer a starship. I also appreciate the Icarus' team's imaginative re-casting of the Icarus myth, which imagines a chastened Icarus washed up on a desert island planning to forge wings out of new materials so he can make the attempt again. But what I always fall back on is...

Ralph McNutt's recent update on the progress of the Innovative Interstellar Explorer concept elicited plenty of comments, enough that Dr. McNutt wanted to answer them in a new post. Now at Johns Hopkins University Applied Physics Laboratory, McNutt is Project Scientist and a Co-Investigator on NASA's MESSENGER mission to Mercury, Co-Investigator on NASA's Solar Probe Plus mission to the solar corona, Principal Investigator on the PEPSSI investigation on the New Horizons mission to Pluto, a Co-Investigator for the Voyager PLS and LECP instruments, and a Member of the Ion Neutral Mass Spectrometer Team on the Cassini Orbiter spacecraft. With all that on his plate, it's hard to see how he has time for anything else, but McNutt also continues his work as a consultant on the Project Icarus interstellar design study. His Innovative Interstellar Explorer is a precursor mission designed to push our technologies hard. by Ralph McNutt I typically do not get involved with commenting on comments...

by Ralph McNutt Because of the interest that the Innovative Interstellar Explorer mission generates whenever I write about it, I was pleased to receive Ralph McNutt's latest update on IIE. This was written in response to a recent article in these pages on the Voyager missions and refers to several of the comments in that thread. I first talked to Dr. McNutt about interstellar precursors back in 2003, when researching my Centauri Dreams book. Now at Johns Hopkins University Applied Physics Laboratory, the physicist's space experience is comprehensive. He is Project Scientist and a Co-Investigator on NASA's MESSENGER mission to Mercury, Co-Investigator on NASA's Solar Probe Plus mission to the solar corona, Principal Investigator on the PEPSSI investigation on the New Horizons mission to Pluto, a Co-Investigator for the Voyager PLS and LECP instruments, and a Member of the Ion Neutral Mass Spectrometer Team on the Cassini Orbiter spacecraft. He has published over 150 science and...

One of the pleasures of writing Centauri Dreams is digging into a paper to look at it from various directions, as I did recently with Jim Benford's work on cost-optimized beamed sails. Jim has been working on these concepts for a long time, and although I had originally intended to devote two days to his latest, the depth of his analysis led me to extend the discussion to a third day. That kind of focus invariably means I get behind in other stories, though, so I want to be sure to catch up with matters like the recent news about the Voyagers as they continue to exit our system. I always point to the still functioning instruments of the Voyagers as an outstanding example of how we can build spacecraft for the long haul -- these tough platforms show what can be done with careful design, and future craft fully optimized for even longer flights certainly seem practical. In this case, three instrument packages -- the Cosmic Ray Subsystem, the Magnetometer and the Low Energy Charged...

Although we frequently talk about beamed sails for interstellar missions, the fact is that spacecraft on the scale Robert Forward used to talk about that could take us to Alpha Centauri in 40 years won't come out of nowhere. The evolution of the solar sail into the beamed sail will involve all kinds of experimentation and a variety of mission concepts developed for use right here in the Solar System. Consider just one, a microwave-driven sail that could reach Mars in one month, and Pluto in five years. I wrote about this one in A Microwave-Beamed Sail for Deep Space. The idea comes from Jim and Greg Benford, who discussed it in a 2006 issue of the Journal of the British Interplanetary Society. The scenario involved a phenomenon the duo had discovered in their laboratory work on microwave beaming. Experimenting with a 7.5 g/m2 carbon sail, they had uncovered the fact that molecules evaporating from the sail created accelerations beyond what would have been expected from photons alone....

by K.F.Long, co-founder Project Icarus Kelvin Long is well known to Centauri Dreams readers. The physicist and aerospace engineer is, in addition to being one of the most energetic voices in the service of interstellar propulsion studies, the co-founder of Project Icarus, the successor to the 1970s-era Project Daedalus starship design study. Here Kelvin looks at where the ongoing Icarus effort stands in terms of fusion, placing that propulsion option in the context of the broader questions raised by pushing a payload to the stars. Back in December 2009 I wrote an article titled Project Icarus and the Motivation Behind Fusion Propulsion. This was an attempt to justify the initial design choice of the team as part of the engineering requirements for the study that is Project Icarus. Despite this article and other discussions we have had, we have recently learned something from our experience at the 100 Year Starship Study Symposium: People still don't understand the Daedalus connection...