The 192 lasers of the National Ignition Facility at Lawrence Livermore National Laboratory in California can focus 500 trillion watts of power onto a pellet of hydrogen fuel the size of a pencil eraser. With full-scale experiments slated to begin soon, we'll learn much about the feasibility of nuclear fusion on Earth, hoping to extract more energy from the process than goes into making it happen. The forms of hydrogen at play here are deuterium and tritium, which fuse to form helium. Image: All of the energy of NIF's 192 beams is directed inside a gold cylinder called a hohlraum, which is about the size of a dime. A tiny capsule inside the hohlraum contains atoms of deuterium (hydrogen with one neutron) and tritium (hydrogen with two neutrons) that fuel the ignition process. Credit: National Ignition Facility. Inertial confinement fusion using lasers is a different approach than the magnetic confinement method used at the International Thermonuclear Experimental Reactor (ITER),...

by Adam Crowl In the market for a mammoth starship? Recently released work by Friedwardt Winterberg, discussed here by Adam Crowl, points to fast interplanetary travel and implies possibilities in the interstellar realm that are innovative and ingenious. Adam notes in an e-mail that Winterberg's drive has certain similarities to MagOrion, a system that in its earliest iteration combined a magnetic sail with small yield nuclear fission devices. Dana Andrews and Robert Zubrin first published that concept in 1997 and it has been evolving in the years since, but Winterberg's work takes the idea into the realm of what may be a truly workable fusion design. Read on as we follow up our earlier story on Winterberg with a much deeper look. Friedhardt Winterberg has worked on inertial confinement fusion since 1954 and was extensively involved in developing new fusion devices during the Cold War alongside bomb-makers like Edward Teller. Much of his non-fission triggering work was classified,...

Back in 1966, the Jet Propulsion Laboratory's Dwain Spencer laid out the principles of a fusion engine that burned deuterium and helium-3 (an isotope of helium with a nucleus of two protons and one neutron). Deuterium and helium-3 make a good combination for rocket propulsion because a fusion-based drive based on them releases one-hundredth the amount of radioactive neutrons than deuterium/tritium. A spacecraft using such an engine would, in other words, require far less shielding. And even more to the point, the protons and alpha particles produced by the reaction can be readily manipulated by a magnetic nozzle. This was the background in 1971, when physicist Friedwardt Winterberg published a paper on fusion ignition using intense beams of electrons, speculating that such techniques could be used in rocket propulsion. Winterberg's work took place in a context of energetic study, with newly declassified work becoming available that examined the use of lasers in igniting fusion. At...

It's safe to say that Franklin Chang-Diaz knows what he's talking about when he discusses the space experience. An astronaut who has logged seven flights and over 1600 hours in space (a period that includes three spacewalks), Chang-Diaz has been making even more impressive news in recent times with his Ad Astra Rocket Company, where the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) is under development. It's heartening to think of VASIMR undergoing space-based tests, a future that is now in the cards with the news that NASA has plans to test the VASIMR engine aboard the International Space Station. We naturally think long-term here, but VASIMR's uses in potential missions to Mars (Chang-Diaz talks about a 39-day trip to the planet!) and beyond will first have to be shaken out in near-Earth orbit. But ponder a VASIMR gradually becoming operational, mounting missions to communications satellites that are now economically all but unreachable. Indeed, VASIMR sets up the...

By Larry Klaes Tau Zero journalist Larry Klaes takes a look at Mason Peck's work with reconfigurable space structures. Anyone who ponders the future of large structures in the Solar System -- and this might include space-based telescopes, O'Neill habitats or perhaps one day enormous lenses of the sort Robert Forward envisioned -- will wonder how such creations can be assembled. Potential solutions may one day grow out of Peck's work, until recently funded by NIAC. Centauri Dreams also wonders how such theories will be supplemented by nanotechnological techniques that may one day return us to the era of thinking big in environments far from home. Space is a promising but often difficult environment to work in. A typical spacecraft has to deal with a near vacuum, extreme temperatures, radiation fields, and micrometeoroids. With space 'starting' at one hundred miles above Earth's surface, a region attainable at present only with expensive rockets, sending up numerous vehicles that have...

Please use this post for further comments in the above thread, which originally appeared under the title "A Practical Positron Rocket?"

We're a long way from achieving practical fusion to supply our power needs, much less fusion rockets to the stars. Just how far can be gauged by a look at current research. The principle seems straightforward: Heat hot, ionized gas to the point of ignition and you can fuse hydrogen into helium. But can you contain the plasma while you're heating it? More to the point, can you get more power out of your device than you put in? Most of the effort these days is going into tokamak designs that use magnetic fields to contain the plasma. But tokamaks tap plasma currents to produce at least part of the needed field. And, says John Canik (University of Wisconsin), "The problem is you need very large plasma currents and it's not clear whether we'll be able to drive that large of a current in a reactor-sized machine, or control it. It may blow itself apart." Enter the stellarator, an alternative plasma confinement method that uses no plasma currents, but one that loses energy at a high rate...

A nice upgrade to existing satellite engine technology comes out of Georgia Tech, where researchers have developed a design that allows the engine to optimize available power, much like the transmission of a car. Thus the engine can burn at full throttle in 'first gear,' maximizing acceleration, while dropping into a much more economical gear for long-term space operations. "You can really tailor the exhaust velocity to what you need from the ground," says team leader Mitchell Walker. The engine at work here is known as a Hall effect thruster, a plasma-based propulsion system that operates with xenon, a gas that is injected into a discharge chamber where its atoms become ionized. The electrons that are stripped from the outer shell are trapped in a magnetic field, while the heavier xenon ions are accelerated out into space by an electric field. What Georgia Tech has introduced is better control over the exhaust stream through an enhanced electric and magnetic field design. Image:...

On his Crowlspace site, Adam Crowl points us to the artwork of Rhys Taylor, a remarkably gifted graphic artist in the U.K. Taylor has created a series of Project Orion images from the nuclear pulse propulsion studies conducted in the late 1950s and early 1960s (and I presume he's unrelated to Project Orion leader Ted Taylor). Check this animation of an Orion launch, for example, or click here for Taylor's gallery of other Orion art, including (my favorite) Orion at Enceladus. The Saturnian moon was once considered a prime destination for an early Orion mission. Taylor's work is lovely indeed. Now if I can just get Adam to explain the term 'gob-smacked.'

Whenever I think about Project Orion, I recall the 'putt-putt' experiments that tested the propulsion concept back in 1959. It was hardly an atomic spaceship, but the little putt-putt called 'Hot Rod' is as far as Orion ever got operationally. Using chemical explosives, Hot Rod rose 100 meters, a brief flight that nonetheless validated the idea that a spacecraft built around nuclear bombs, propellant and a pusher plate could be made to take stable flight. An atomic spaceship. There was a time when the idea seemed to have interstellar possibilities. Freeman Dyson, a key figure in Orion, envisioned one version that used a copper pusher plate twenty kilometers in diameter. Driving the ship would be a nuclear arsenal of staggering proportions: 30 million nuclear bombs, each of which would explode 120 kilometers behind the vehicle at intervals of 1,000 seconds. With a total acceleration time of five hundred years—and a comparable time for deceleration—this mammoth super-Orion...

New Scientist is covering the work of Rudolph Meyer (UCLA), who envisions a vehicle that sounds for all the world like a cross between a solar sail and an ion engine. And in a way, it is: Imagine a flexible solar panel a solid 3125 square meters in size, and imagine this 'solar-electric membrane' weighing no more than 16 grams per square meter, far lighter than today's technology allows. I'll be anxious to see the paper when it's published in Acta Astronautica, but the gist of the design seems to be this: the solar membrane would power an ion engine array which, conventionally enough, draws xenon ions through a powerful electric grid to create thrust. The membrane, stabilized by additional ion engines at the corners, could reach remarkable speeds. Meyer talks about 666,000 kilometers per hour -- that's one year to Pluto, and an obvious invitation out into the Kuiper Belt. No show stoppers here, but clearly a design heavily dependent on advances in thin film arrays. I always listen to...

It's heartening to see that NASA has inked an agreement with a commercial firm to get its VASIMR (Variable Specific Impulse Magnetoplasma Rocket) technology into the private sector. Houston-based Ad Astra Rocket Company is actually located within the Johnson Space Center and, under the direction of president and CEO Franklin Chang-Diaz, focuses on the development of plasma rocket technologies. Its agreement with NASA should further work on a design widely thought to offer powerful advances over conventional chemical rockets. Chang-Diaz is a veteran of seven Shuttle flights who retired from NASA last July to focus on the Ad Astra/VASIMR connection. The design, which he conceived back in 1979, uses magnetic fields to channel a plasma exhaust that would melt conventional rocket nozzles. An additional beauty of the concept is that both thrust and specific impulse can be varied during the course of a mission. Ad Astra compares this to the transmission in an automobile; the exhaust...

The European space agency is ramping up expectations for its Dual-Stage 4-Grid (DS4G) ion thruster. Using a concept developed by UK propulsion theorist David Fearn, the agency's test model, designed and built by a team from Australian National University, is said to be ten times more fuel efficient than the ion engine used on the SMART-1 lunar mission. In fact, says Roger Walker of ESA's Advanced Concepts Team, who is technical manager of the project, "Using a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldn't just reach the Moon, it would be able to leave the Solar System entirely." Walker calls the design "an ultra-ion engine," and ESA talks about using flight models to push into the Kuiper Belt and beyond, or deploying clusters of higher-power versions of the engine on manned Mars missions. All of which is exciting stuff, though it comes with a needed caveat. Currently at the stage of laboratory...

Ion drives may open up the outer Solar System, but they're anything but high-thrust. With NASA's Deep Space 1 mission and the later European Smart 1 moon mission, the idea was to operate for long periods of time with very little kick from the engine. The effect is cumulative, and it works. Japan's Hayabusa asteroid probe used four ion engines designed to burn throughout its cruise to asteroid Itokawa. 20,000 hours of cumulative operation used up a scant 20 kilograms of propellant, highlighting the efficiency of these engines. NASA has run an NSTAR thruster at the Jet Propulsion Laboratory for over 30,000 continuous hours, almost five years of operation. Now the European Space Agency has conducted successful tests of a new kind of ion drive, one designed to provide greater thrust than its predecessors. The Helicon Double Layer Thruster (HDLT) uses radio waves to ionise argon gas, creating two layers of plasma between which charged particles can be accelerated in a beam. The HDLT...

First noted in Star Spangled Cosmos, this article from the Palm Beach Post about fusion research, focusing on recent progress and discussing the International Thermonuclear Experimental Reactor (ITER) consortium. The latter group plans to build an experimental fusion reactor in France by 2016. Speaking to Stephen Paul, a senior research physicist at Princeton University's plasma laboratory, writer Ron Wiggins notes that fusion reactions have been sustained in laboratory settings for up to 24 seconds. How do we fund the next steps toward viability? From the story: The problem is that plasma — the primordial gas resulting when hydrogen atoms are heated to 100 million degrees — is difficult to contain in small reactors. The bigger the reactor, the easier it is to control the reaction. Big reactors are expensive. "Our reactor at Princeton is small — a man could walk into it. England has the biggest facility — about two stories." ITER would create such a reactor, a...

According to this note from Out of the Cradle, the site will feature live blog coverage on the Falcon-1 launch, now scheduled for Saturday. Falcon-1 is the first all new orbital rocket in over a decade, and the first privately developed liquid fuel rocket to attempt orbit. Keep an eye as well on the SpaceX site for further information. If the Falcon-1 makes orbit, it's good news for space agency budgets everywhere -- priced at $6.7 million, the SpaceX rocket offers the lowest cost to orbit of any launch vehicle in the world, a significant step forward for the commercial space industry.