One of the interesting things about gravitational assists is their ability to accelerate massive objects up to high speeds, provided of course that the astrophysical object being used for the assist is moving at high speeds itself. Freeman Dyson realized, as we saw yesterday, that a pair of tightly rotating white dwarfs could offer such an opportunity, while a binary neutron star carried even more clout. When Dyson was writing his “Gravitational Machines” paper, neutron stars were still a theoretical concept, so he primarily focused the paper on white dwarfs. Get two neutron stars in a tight enough orbit and the speeds they achieve would make it possible to accelerate a spacecraft making a gravity assist up to a substantial percentage of lightspeed. But what an adventure that close pass would be -- the tidal forces would be extreme. I don’t recall seeing a neutron star propulsive flyby portrayed in science fiction (help me out here), though Gregory Benford offers a variant on the...

Let's start the week by talking about gravitational assists, where a spacecraft uses a massive body to gain velocity. Voyager at Jupiter is the classic example, because it so richly illustrates the ability to alter course and accelerate without propellant. Michael Minovitch was working on this kind of maneuver at UCLA as far back as the early 1960s, but it was considered even before this, as in a 1925 paper from Friedrich Zander. It took Voyager to put gravity assists into the public consciousness because the idea enabled the exploration of the outer planets. Can we use this kind of maneuver to help us gain the velocity we need to make an interstellar crossing? Let's consider how it works: We're borrowing energy from a massive object when we do a gravity assist. From the perspective of the Voyager team, their spacecraft got something for 'free' at Jupiter, in the sense that no additional propellant was needed. What's really happening is that the spacecraft gained energy at the...

Most of my research for Centauri Dreams involves looking at papers and presentations on matters involving deep space, whether propulsion systems, closed loop life support, or even possible destinations. That's why it's a huge help to get an article like the one below, giving us an overview of current thinking and an analysis of what is either in the pipeline or under consideration for the near-term. How do we get from here to the kind of Solar System infrastructure we'll need to go interstellar? Ioannis Kokkinidis has an impressive background: He holds a Master of Science in Agricultural Engineering from the Department of Natural Resources Management and Agricultural Engineering of the Agricultural University of Athens. He went on to obtain a Mastère Spécialisé Systèmes d'informations localisées pour l'aménagement des territoires (SILAT) from AgroParisTech and AgroMontpellier and a PhD in Geospatial and Environmental Analysis from Virginia Tech. Today...

Looking at John Brophy's Phase II NIAC award reminds us how useful the two-step process can be at clarifying and re-configuring deep space concepts. Brophy (Jet Propulsion Laboratory) had gone to work in Phase I with a study called "A Breakthrough Propulsion Architecture for Interstellar Precursor Missions." The work studied a lithium-fueled ion thruster with a specific impulse of 58,000 seconds. If that didn't get your attention, consider that the Dawn spacecraft's ISP is 3,000 seconds, and think about what we might be able to do with that higher figure. I think about ideas like this in terms of infrastructure. The relation to interstellar flight is this: While we may well get robotic nano-probes off on interstellar missions (think Breakthrough Starshot) some time this century, the idea of human expansion into the cosmos awaits the growth of our civilization into the rest of the Solar System. Along the way, we will learn the huge lessons of closed-loop life support, means of...

When we kick around ideas for deep space propulsion, we have to keep in mind that the best solutions may involve hybrid technologies, leveraging the best of several methods. JAXA (Japan Aerospace Exploration Agency) demonstrates this with its ambitious plan to take a sail like IKAROS to Jupiter, for a study of the Jupiter trojan asteroids. Like the original, the upgraded IKAROS will use liquid crystal reflectivity control devices as a means of attitude control. But operating at the limits of solar sail functionality, the new JAXA sail will also carry a high specific impulse ion engine to facilitate its maneuvers among the trojans. Here we have a mission that couldn't be flown with just a sail, because the numerous trajectory changes required at destination demand a reliable thruster, one that in this case will be fed by some 30,000 solar panels in the form of thin film solar cells attached to the sail membrane. What of missions into still deeper space? We'd like to return with robust...

Although I want to start the week by looking at hybrid propulsion technologies, let's start by considering developments in ion propulsion before going on to see how they can be adapted for future deep space missions. Hall thrusters are a type of ion engine that uses electric and magnetic fields to manipulate inert gas propellants like xenon. The electric field turns the propellant into a charged plasma which is then accelerated by means of a magnetic field [see reader 'Supernaut's correction to this in the comments below]. We've seen the benefits of ion engines in missions like Dawn, which has recently received a second mission extension to continue its work around the asteroid Ceres. Now we learn that a Hall thruster called X3, developed at the University of Michigan by Alec Gallimore, has received continuing design modification by researchers at NASA Glenn and the US Air Force, scaling up the low thrust levels produced by conventional ion engines. A series of tests have...

Larry Klaes has been a part of Centauri Dreams almost since the first post. That takes us back to 2004, and while I didn't have comments enabled on the site for the first year or so, I remember talking to Larry about my Centauri Dreams book by email. Ever since, this author and freelance journalist with a passion for spaceflight has contributed articles, comments and ideas, as he does again today. Project Orion caught Larry's attention as a way of using known technologies to enable daring deep space missions. The essay below gives us an overview of Orion and its possibilities, looking at a concept that never flew but still captures the imagination. In addition to his active freelancing, Larry has been editor of SETIQuest magazine and president of the Boston chapter of the National Space Society. He now writes regularly for SpaceFlight Insider, where this article originally appeared. by Larry Klaes Image: Project Orion concept. Image Credit: Adrian Mann. At their most fundamental...

Thinking about Eugen Sänger's photon rocket concept inevitably calls to mind his Silbervogel design. The 'Silverbird' had nothing to do with antimatter but was a demonstration of the immense imaginative power of this man, who envisioned a bomber that would be launched by a rocket-powered sled into a sub-orbital trajectory. There it would skip off the upper atmosphere enroute to its target. The Silbervogel project was cancelled by the German government in 1942, but if you want to see a vividly realized alternate world where it flew, have a look at Allen Steele's 2014 novel V-S Day, a page-turner if there ever was one. I almost said that it was a shame we don't have a fictionalized version of the photon rocket, but as we saw yesterday, there were powerful reasons why the design wouldn't work, even if we could somehow ramp up antimatter production to fantastic levels (by today's standards) and store and manipulate it efficiently. Energetic gamma rays could not be directed into an...

Building a space infrastructure is doubtless a prerequisite for interstellar flight. But the questions we need to answer in the near-term are vital. Even to get to Mars, we subject our astronauts to radiation and prolonged weightlessness. For that matter, can humans live in Mars' light gravity long enough to build sustainable colonies without suffering long-term physical problems? Gregory Matloff has some thoughts on how to get answers, involving the kind of space facility we can build with our current technologies. The author of The Starflight Handbook (Wiley, 1989) and numerous other books including Solar Sails (Copernicus 2008) and Deep Space Probes (Springer, 2005), Greg has played a major role in the development of interstellar propulsion concepts. His latest title is Starlight, Starbright (Curtis, 2015). by Gregory Matloff The recent demonstrations of successful rocket recovery by Blue Origin and SpaceX herald a new era of space exploration and development. We can expect, as...

Our choice of orbits can create scientifically useful space missions that can be operated at lower cost than their more conventional counterparts. How this has been done and the kind of missions it could enable in the future is the subject of James Jason Wentworth's essay. An amateur astronomer and interstellar travel enthusiast, Wentworth worked at the Miami Space Transit Planetarium and volunteered at the Weintraub Observatory atop the adjacent Miami Museum of Science. Now making his home in Fairbanks (AK), he was the historian for the Poker Flat Research Range sounding rocket launch facility. His space history and advocacy articles have appeared in Quest: The History of Spaceflight magazine and Space News. by J. Jason Wentworth In the 1990s, then NASA Administrator Daniel S. Goldin introduced the "Better, Faster, Cheaper" paradigm for space missions. While NASA's subsequent experiences led many engineers to modify that to "Better, Faster, Cheaper--choose two," the goal of low cost...

If you're a Centauri Dreams regular, you're familiar with Adam Crowl, an Australian polymath who is deeply involved in the ongoing Project Icarus starship design study. Adam maintains a blog called Crowlspace where interesting and innovative ideas emerge, some of them related to earlier work that has been largely forgotten in our era. A recent post that caught my eye was on Ernst Stuhlinger's 'umbrella ship,' a kind of spacecraft that, when introduced to the world on Walt Disney's 1957 TV show Mars and Beyond, surely surprised most viewers. The umbrella ship, as Adam notes, looks nothing like what readers of the famous space series in Collier's (1952-1954) had come to associate with manned travel to other worlds. Wernher von Braun was then championing massive rockets to be engaged in the exploration of Mars, an exploratory operation that would send a fleet of vessels to the Red Planet. Unlike tiny capsules of the kind we used to reach Earth orbit and explore the Moon, these would be...

My view is that the spacecoach, the subject of renewed discussion below by Brian McConnell and a design he and Alex Tolley have created, is the most innovative and downright practical idea for getting crews and large payloads to the planets that I've yet encountered. It's low-cost and uses ordinary consumables as propellant, dramatically revising mission planning. Brian and Alex have continued refining the concept, as explained below in Brian's essay on a modified version of the rocket equation. Have a look and you'll see that planning long duration missions or missions with larger crews becomes a much more workable proposition because more consumables translate into more propellant. Could the spacecoach be our ticket to building a space-based infrastructure, with unmistakable implications for even deeper space? by Brian S McConnell The spacecoach, first introduced here in Spaceward Ho! and A Stagecoach To The Stars and on spacecoach.org, is based on the idea of using consumables...

I'm glad to see that Brian McConnell will be speaking at the International Space Development Conference in Toronto this week. McConnell, you'll recall, has been working with Centauri Dreams regular Alex Tolley on a model the duo call 'Spacecoach.' It's a crewed spacecraft using solar electric propulsion, one built around the idea of water as propellant. The beauty of the concept is that we normally treat water as 'dead weight' in spacecraft life support systems. It has a single use, critical but heavy and demanding a high toll in propellant. The spacecoach, on the other hand, can use the water it carries for radiation shielding and climate control within the vessel, while crew comfort is drastically enhanced in an environment where water is plentiful and space agriculture a serious option. Along with numerous other benefits that Brian discusses in his recent article A Stagecoach to the Stars, mission costs are sharply reduced by constructing a spaceship that is mostly water....

Imagine the kind of spaceship we'll need as we begin to expand the human presence into the nearby Solar System. We'd like something completely reusable, a vessel able to carry people in relative comfort everywhere from Mars to Venus, and perhaps as far out as the asteroid belt, where tempting Ceres awaits. Capable of refueling using in situ resources, these are ships not crafted for a single, specific mission but able to operate on demand without entering a planetary atmosphere. Brian McConnell, working with Centauri Dreams regular Alex Tolley, has been thinking about just such a ship for some time now. A software/electrical engineer, pilot and technology entrepreneur based in San Francisco, Brian here explains the concept he and Alex have come up with, one that Alex treated in a previous entry in these pages. The advantages of their 'spacecoach' are legion and Brian also offers a sound way to begin testing the concept. The author can be reached at bsmcconnell@gmail.com. by Brian...

How do you go about creating a straightforward, highly durable design for a spacecraft, one that is readily refuelable and offers manifest advantages for crew comfort and safety? Alex Tolley and Brian McConnell have been asking that question for some time now, coming up with an ingenious solution that could open up large swathes of the Solar System. Alex tells me he is a former computer programmer now serving as a lecturer in biology at the University of California, where he hopes to inspire the next generation of biologists. He's also a Centauri Dreams regular who was deeply influenced by 2001: A Space Odyssey and the Apollo landings. Below, he fills us in on the details in a narrative that imagines an early trip on such a vessel. by Alex Tolley The covered wagon or prairie schooner is one of the iconic images of the 19th century westward migration of the American pioneers. The wagon was simple in construction, very rugged, and repairable. They were powered most often by oxen that...

Back in 1950, George Pal produced Destination Moon, a movie that was based (extremely loosely) on Robert Heinlein's Rocketship Galileo. Under the direction of Irving Pichel, the film explained the basics of a journey to the Moon -- using among other things an animated science lesson -- to a world becoming intrigued with space travel. I've wondered in the past whether we might one day have an interstellar equivalent of this film, a look at ways of mounting a star mission in keeping with the laws of classical mechanics. Call it Destination Alpha Centauri or some such and let's see what we get. Christopher Nolan's film Interstellar doesn't seem to be that movie, at least based on everything I've seen about it so far. I did think the early trailers were interesting, evoking the human urge to overcome enormous obstacles and buzzing with a kind of Apollo-era triumphalism. The most recent trailer looks like starflight is again reduced to magic, although maybe there will be some attempt to...

One day in the late summer of 1958, at a time when the Jet Propulsion Laboratory was still in the hands of the U.S. Army (the transfer to NASA wouldn't happen until the end of that year), Freeman Dyson and Ted Taylor showed up at the facility outside Pasadena. Try to imagine the scene: At the time, JPL was busy building the Explorer 6 satellite, all 65 kilograms of it. And here came two Project Orion scientists talking about not just satellites but auxiliary vehicles, additional payload to fly aboard their proposed 4000 ton spacecraft that they hoped would explore the outer planets. "The reception there was rather cool," Dyson would later say. "The lady at the front office decided Taylor and I were a pair of crackpots and tried to get rid of us. After about half an hour of arguing we got inside and then it all went very well." Image: Freeman Dyson, whose payload ideas must have confounded the team working on early Earth satellites. Credit: Courtesy of Princeton University Archives....

Yesterday I remarked on how many more tools for exoplanet discovery we have today than were available to Harry Stine when he wrote "A Program for Star Flight" in 1973. That same day came the disheartening news that the Kepler mission has been stopped in its tracks by an equipment malfunction. But take heart -- a vast amount of data already gathered by Kepler remains to be studied, meaning we'll be getting Kepler discoveries for some time to come. The Kepler news also sharpens our focus on TESS (Transiting Exoplanet Survey Satellite), which will build our catalog of nearby stars hosting exoplanets, with launch now scheduled for 2017. For more on Kepler, see Dennis Overbye's Breakdown Imperils NASA's Hunt for Other Earths. But back to Stine, who in 1973 was hunting not only for target exoplanets but also for a propulsion system that would get a human crew to them. He was evidently familiar with Eugen Sänger's papers on photon rockets, in which the German designer proposed deflecting...

Tim Folger and Les Johnson (NASA MSFC) stood last summer in front of a nuclear rocket at Marshall Space Flight Center in Huntsville, Alabama. Johnson's work in advanced propulsion concepts is well known to Centauri Dreams readers, but what he was talking to Folger about in an article for National Geographic was an older technology. NERVA, once conceived as part of the propulsion package that would send astronauts to Mars, had in its day the mantle of the next logical step beyond chemical propulsion. A snip from the story: Johnson looks wistfully at the 40,000-pound engine in front of us... "If we're going to send people to Mars, this should be considered again," Johnson says. "You would only need half the propellant of a conventional rocket." NASA is now designing a conventional rocket to replace the Saturn V, which was retired in 1973, not long after the last manned moon landing. It hasn't decided where the new rocket will go. The NERVA project ended in 1973 too, without a flight...

Richard Obousy, a familiar face on Centauri Dreams, is president and primary propulsion senior scientist for Icarus Interstellar, whose portfolio includes Project Icarus, the redesign of the Project Daedalus starship. Dr. Obousy is just back from the latest Advanced Space Propulsion Workshop and, as he did for the 2010 ASPW, he now offers his take on the event. Although I missed this ASPW, I'll be back in Huntsville soon for an upcoming conference, and I heartily second what Richard has to say about that Saturn V at the US Space and Rocket Center. It's not to be missed. by Richard Obousy The 2012 Advanced Space Propulsion Workshop (ASPW) was held over three days at the US Space and Rocket Center in Huntsville, Alabama running from Tuesday 27th November to Thursday 29th November. The conference was sponsored by the Game Changing Development Program under NASA's Space Technology Program and the Office of the Chief Technologist at NASA Marshall Space Flight Center. This was the 19th...