The news from Reaction Engines Ltd. about its air-breathing rocket engine SABRE is interesting not only for its implications in near-term space development, but also for its pedigree. Reaction Engines grew out of British work on a single-stage-to-orbit concept called HOTOL ((Horizontal Take-Off and Landing) that was being developed by Rolls Royce and British Aerospace in the 1980s. Initially backed by the British government, HOTOL lost its funding in 1988, prompting Alan Bond's decision to form the new company, which would continue the work with private funds. The name Alan Bond should ring many bells for Centauri Dreams readers. Bond was a key player in and leading author of the report on the British Interplanetary Society's Project Daedalus, the ambitious 1970s attempt to design a starship based on fusion propulsion. One thing the extensive Daedalus effort made clear was that a future attempt to reach the stars could only take place within the context of a Solar System-wide...

Although we ordinarily think of Stanislaw Ulam in connection with pulse propulsion -- and in particular with the Orion concept, in which nuclear devices are exploded behind the spacecraft -- the scientist was also investigating other propulsion ideas. It puts yesterday's discussion of Freeman Dyson's 'gravitational machines' into context to realize that Ulam was writing about obtaining 'a velocity arbitrarily large -- that is, close to the velocity of light...' using gravitational slingshots around astronomical objects in papers written as early as the late 1950s. There is, as Greg Matloff and Eugene Mallove remind us in The Starflight Handbook fantastic energy available in the orbital motion of celestial bodies. How best to tap it? Michael Minovitch was already working at UCLA in the early 1960s on how to use a gravity 'slingshot' to affect spacecraft trajectories, thus extending the capacity for exploration. Dyson's futuristic paper, as we saw yesterday, described gravitational...

When young Rod Hyde, fresh out of MIT, started working on starship design in mid-1972, there were not many fusion-based precedents for what he was up to. He had taken a summer job that would turn into a career at Lawrence Livermore National Laboratory, but right off the bat he was involved with Lowell Wood and John Nuckolls in a concept that would use a battery of lasers to create fusion reactions whose energy would be channeled out the back of the ship by magnetic nozzles. Wood and Nuckolls had been developing their ideas for years, after Nuckolls first began to ponder how to use laser fusion micro-explosions to drive a spacecraft. Now the duo had a kid who had spent his previous summers working in a beet cannery, a recruit for Livermore who had run up high grades at MIT and had shown he could work like a demon once he put his mind to it. This would be his first technical job. Hyde went into full gear on containing the plasma from the fusion explosions with a magnetic field. If they...

by A. A. Jackson It’s always good when you can go to the source, which I am delighted to do with this reminiscence by Al Jackson, whose laser-powered ramjet (and laser-powered interstellar rocket) ideas we’ve been looking at for the past few days. Al recalls discovering the work of Eugen Sänger back around 1960 and beginning the study of interstellar propulsion ideas, a passion he continues to this day. His 1975 doctorate from the University of Texas at Austin followed his work for NASA during the heyday of Apollo as astronaut trainer on the Lunar Module Simulator. Here he thinks back to the genesis of his interest in astronautics and reflects on the factors that led to his combining the Bussard ramjet concept with the developing idea of beamed energy. I don’t think I had ever planned to write a technical paper about interstellar flight. However, as an SF reader I had been entranced by the idea since the early 1950?s. I was already a space cadet! When I got to university in 1959 and...

The year after Al Jackson, working with Daniel Whitmire, published his concept of a laser-powered interstellar ramjet, the duo returned in the pages of JBIS with a spinoff design. The issue was obvious: Central to Robert Bussard's ramjet design was the idea that the spacecraft would carry no fuel, but collect reaction mass from the interstellar medium. There were a number of reasons why this was problematic, including the drag of the ram scoop and the problem of lighting proton/proton fusion. So Jackson and Whitmire decided to look at a space-based laser powering up a starship that carried its own reaction mass onboard. It turned out that John Bloomer had looked at supplying a spacecraft through an external laser energy source as far back as 1967, though in his case the craft would use the laser energy it received to run an electrical propulsion system (the Bloomer citation is given at the end of this article). Jackson wanted to think in terms of relativistic interstellar flight, and...

Many of the interstellar concepts I write about in these pages take on a life of their own. After the initial brainstorming, the idea gets widely enough disseminated that other scientists take it on, looking to modify and improve on the original concept. That's been true in the case of solar sails and the more recently devised 'lightsails,' which use beamed energy from a laser or microwave source to drive the vehicle. We continue to study magnetic sails -- 'magsails' -- and various nuclear options like the inertial confinement fusion that powered Daedalus and perhaps Icarus. Sometimes insights arise when ideas are grafted onto each other to create a hybrid solution. The idea I want to examine today, a hybrid design combining a Bussard-style interstellar ramjet with laser beaming -- exemplifies this mix and match process. Working with Daniel Whitmire, A. A. Jackson, a frequent commenter and contributor here on Centauri Dreams, pondered the various issues the Bussard ramjet had run...

I see that 'Zarmina' is back in the news. The informal designation refers to Gliese 581 g, an exoplanet candidate announced by the Lick-Carnegie team in an effort led by Steven Vogt (UC-Santa Cruz). First you see it, then you don't -- Gl 581 g has been controversial from the start, and is now the subject of a new analysis describing a 32-day orbit, a super-Earth in the habitable zone. More on the analysis later in the week, because my purpose today is to keep digging into the options for getting to a place like this once we're sure it really does exist. Gl 581 is just over 20 light years from the Sun in the constellation Libra, a red dwarf whose planetary system is one of the nearest yet detected. Among the options for propulsion in a future interstellar probe is Medusa, the brain-child of Los Alamos physicist (now retired) Johndale Solem. As examined here on Friday, Medusa is a nuclear-pulse system, like Orion in that it relies on the explosion of a series of atomic bombs to propel...

Having looked at the Z-pinch work in Huntsville yesterday, we've been kicking around the question of fusion for propulsion and when it made its first appearance in science fiction. The question is still open in the comments section and I haven't been able to pin down anything in the World War II era, though there is plenty of material to be sifted through. In any case, as I mentioned in the comments yesterday, Hans Bethe was deep into fusion studies in the late 1930s, and I would bet somewhere in the immediate postwar issues of John Campbell's Astounding we'll track down the first mention of fusion driving a spacecraft. While that enjoyable research continues, the fusion question continues to entice and frustrate anyone interested in pushing a space vehicle. The first breakthrough is clearly going to be right here on Earth, because we've been working on making fusion into a power production tool for a long time, the leading candidates for ignition being magnetic confinement fusion...

The road to fusion is a long slog, a fact that began to become apparent as early as the 1950s. It was then that the ZETA -- Zero-Energy Toroidal (or Thermonuclear) Assembly -- had pride of place as the fusion machine of the future, or so scientists working on the device in the UK thought. A design based on a confinement technique called Z-pinch (about which more in a moment), ZETA began operations in 1957 and began producing bursts of neutrons, thought to flag fusion reactions in an apparent sign that the UK had taken the lead over fusion efforts in the US. This was major news in its day and it invigorated a world looking for newer, cheaper sources of power, but sadly, the results proved bogus, the neutrons being byproducts of instabilities in the system and not the result of fusion at all. Fusion has had public relations problems ever since, always the power source of the future and always just a decade or two away from realization. But of course, we learn from such errors, and...

Back in the days when I was studying Old Icelandic (this was a long time ago, well before Centauri Dreams), I took a bus out of Reykjavik for the short journey to Þingvellir, where the Icelandic parliament was established in the 10th Century. It was an unusually sunny day but that afternoon the storms rolled in, and just before sunset I remember looking out from the small hotel where I was staying to a rainbow that had formed over the lava-ridden landscape. It inevitably brought to mind Bifröst, the multi-colored bridge that in Norse mythology connected our world with Asgard, where the gods lived. The idea may have been inspired by the Milky Way. In the world of rocketry, a new Bifröst has emerged, one designed to link the nuclear rocket technologies that were brought to a high level of development in the NERVA program with our present-day propulsion needs. For despite a serious interest that resulted in a total of $1.4 billion in research and the testing of a nuclear engine, NERVA...

NASA’s Innovative Advanced Concepts program has issued a second call for proposals, following the selection of its first round of Phase I concepts in 2011. NIAC (formerly the NASA Institute for Advanced Concepts) ran from 1998 to 2007 in the capable hands of Robert Cassanova, who is now external council chair for the new organization. After a four year interregnum, the program returned in 2011 with the goal of funding “early studies of visionary, long term concepts – aerospace architectures, systems, or missions (not focused technologies).” The 2011 effort resulted in funding for 30 advanced technology proposals, each of them receiving $100,000 for one year of study. The new call for proposals continues the NIAC theme of looking for ideas that are both innovative and visionary, while remaining at an early stage of development, considered as being ten years or more from actual use on a mission. Approximately fifteen proposals are likely to win funding in the 2012 selection, with short...

Project Orion keeps surfacing in propulsion literature and making the occasional appearance on the broader Internet. A case in point is a vigorous defense of Orion-style engineering by Gary Michael Church on the Lifeboat Foundation blog. Church is rightly taken with the idea of propelling payloads massing thousands of tons around the Solar System, but he’s also more than mindful of the realities, both political and economic, that have kept Orion-class missions in the realm of the theoretical. It was, after all, the nuclear test ban treaties of the Cold War era that brought the original project to a close, and anti-nuclear sentiment remains strong in the public today. But the Orion idea won’t go away because it is so tantalizing. Church runs through the relevant information, much of it familiar to old Centauri Dreams hands. Freeman Dyson and Ted Taylor were working on a concept in which a large percentage of the energy of a nuclear explosion -- these are small nukes of the kind Taylor...

Adrian Mann has done it again, as witness his illustration of a gas mining operation on Uranus, reproduced below. The idea, as explored by Adam Crowl on Discovery News this morning, is to acquire vast amounts of helium-3 to supply not only Earth's energy needs but the fusion engines of the Project Icarus star probe. I love Adrian's work and particularly his Project Daedalus images, on display along with much of his other work in his online gallery. What he manages to do is to take an engineering concept and translate it into images that are both accurate yet stunning. It's easy to forget, until he reminds us, that hard-nosed equations and their resulting designs can lead to extraordinary vistas, a result that reawakens the sense of wonder. Image: Balloons, like those shown here in the atmosphere of Uranus, could be used to harvest helium-3 as starship fuel for Project Icarus. Credit: Adrian Mann. Adam Crowl is a frequent Centauri Dreams contributor, but he's also deep in the Project...

by Adam Crowl Adam Crowl has been following Friedwardt Winterberg's fusion concepts for some time, and now weighs in with a look at Winterberg's latest thinking on the use of deuterium reactions in advanced propulsion designs. If fusion is our best bet for interstellar missions, we need to get past the limitations of deuterium/tritium, which produces a neutron flux of such proportion that a manned mission would pay a huge penalty in shielding. Winterberg's ideas on thermonuclear deuterium reactions offer a technique with high exhaust velocities, one with interesting echoes of Project Orion. Back in the 1960s Robert Enzmann imagined immense fusion-propelled starships which saved tankage mass by storing frozen fusion fuel - chiefly deuterium - as a huge frozen ball. Enzmann and his co-workers eventually found that deuterium isn't a very strong solid and a tank of some sort would be needed for mechanical support under acceleration. Even so attaching a starship to a great big mass of...

?The last time we developed a new way of reaching orbit was back in the 1950s. How useful, then, to come up with one that allows huge weight reduction because it leaves propellant and energy source on the ground. Keeping the fuel at home or harvesting it along the way are key ways to conceptualize missions to the outer Solar System or beyond. But in more immediate terms, laser-beamed lightcraft can give us a relatively inexpensive way to low-Earth orbit as we begin to build a true space-based infrastructure. Eric Davis (IASA) and Franklin Mead (formerly of the Propulsion Directorate, AFRL, now retired and pursuing independent research) envision a ground-based laser beam generator system made up of power supply, laser beam generator/transmitter and related tracking, hand-off and safety systems. As we saw yesterday, the system would power an air-breathing pulsed-detonation engine that feeds off ambient air turned into plasma by the laser from the ground, producing a 'superheated plasma...

Not the least of the objections against using laser propulsion to boost a lightsail to the stars is the engineering required to build the system. But theorists like Robert Forward, who originated the laser lightsail idea, never thought we would simply create such a system from scratch. We might ask, then, in the area of laser propulsion, what ideas are being experimented with right now, and might be capable of development into more advanced designs? Enter the Lightcraft Laser lightcraft command the attention here. Extensive work has been done on them at the Air Force Research Laboratory (AFRL), building upon earlier work at the AFRL Propulsion Directorate at Edwards Air Force Base. These early designs aim not at the stars, of course, but at a much more accessible target: Low Earth Orbit. A ground-based laser transmits power to the spacecraft, which collects the incoming energy and uses it to power its propulsion system. The beauty of this is that ambient air becomes the working...

A story on MIT's Technology Review site looks at ion propulsion, and specifically at improvements made in the technology at Glenn Research Center. Comparing the recent work to the engines used in the Deep Space 1 and Dawn missions, the story quotes GRC's Michael Patterson as saying, "We made it physically bigger, but lighter, reduced the system's complexity to extend its lifetime, and, overall, improved its efficiency." That's good news, of course, and Patterson presented it to the AIAA's Joint Propulsion Conference & Exhibit this week in Denver. With sessions on everything from Electric Propulsion Thruster Wear and Life Assessment to Advanced Propulsion Concepts, Denver was clearly the place to be for propulsion mavens. An entire session was devoted to the new ion thrust work, which goes under the name NASA's Evolutionary Xenon Thruster (NEXT). Quoting from an abstract of one of the talks: The NASA NEXT thruster is engineered to be extremely flexible in terms of input power and...

Sometimes our concerns about the human future are eerily like those of our ancestors. Giancarlo Genta (Politecnico di Torino) likes to quote an ancient Assyrian tablet on the matter, one said to have been rendered around 2800 BC: Our Earth is degenerate in these latter days; bribery and corruption are common; children no longer obey their parents; every man wants to write a book and the end of the world is evidently approaching. Marvelous as it is, the quote may be apocryphal, as Genta noted in his recent talk at the deep space conference in Aosta. In fact, I suspect it is, unless the bit about every man wanting to write a book was literally written 'every man wants to keep his household accounts on a clay tablet' or some such. But whatever the case, the quote echoes similar sentiments found throughout history, thoughts that evoke a golden age when things were just plain better than they are in the present and the future did not seem so dark. Which is not to say we don't have serious...

One of the things that makes travel both entertaining and exasperating is the assurance that the best laid plans will come up against events beyond your control. Thus I arrived at Milan's Malpensa airport in plenty of time for my Delta flight, only to be told that the flight had been canceled. But Delta moved quickly on setting me up with an Alitalia flight to New York that left only thirty minutes after the first had been scheduled to leave, and after two more connections (and a twenty-three hour day on the move) I arrived back home. The photo is a shot of the streets of Aosta one early morning, from a walk I took on the last day to remember it by. I returned with a satchel full of notes, the conference proceedings, numerous business cards and the world's worst back-ache, a consequence of trying to move too fast in crowded airports with laptop and luggage. While the latter heals, I've also decided not to try to move through the Aosta material in one go -- there's too much of it, and...

Catching my eye in the latest Carnival of Space, hosted by Brian Wang at Next Big Future, is Adam Crowl's write-up of a rethinking of an exotic ramjet technology. Robert Bussard put the interstellar ramjet into the public eye back in 1960 in a paper proposing that a starship moving fast enough would be able to use the hydrogen between the stars as a source of fuel, enabling a constant acceleration at one g. You'll recognize the Bussard ramjet in Poul Anderson's classic novel Tau Zero (originally published in Galaxy in 1967 as To Outlive Eternity). The Problem with Slow Fusion Anderson's 'Leonora Christine' was a runaway starship, accelerating ever closer to lightspeed until she was punching through entire galaxies in times experienced by the crew as mere minutes. But we don't have to get quite that extreme with the Bussard idea. It's built around the premise of gathering fuel along the way so as to avoid the vast mass ratio problems of conventional rocketry. We can imagine an...