A Fusion Runway to Nearby Stars

by Paul Gilster on November 5, 2005

When physicist Geoffrey Landis reviewed interstellar concepts at the American Association for the Advancement of Science’s 2002 meeting, his wide-ranging presentation considered where we stand on nuclear propulsion, solar and lightsail technologies, and particle-pushed sails. He also addressed the question of the Bussard ramjet, which would use an electromagnetic scoop to collect atoms from the interstellar medium to fuel a fusion reactor. Finding serious problems here (he cites, among other things, the fact that the scoop technology acts more like a brake than an accelerator), Landis went on to consider an alternative:

“These problems can be alleviated if, instead of using the ambient interstellar medium, fuel is deliberately emplaced in the path of the spacecraft before flight. In this way, the fuel (probably in the form of small ‘pellets’) can be chosen to be the optimum composition…

The ‘runway’ of fuel pellets could be emplaced, for example, by a dedicated craft which drops fuel pellets at predetermined locations along the flight path. Each ‘fuel pellet’ would have to contain more than the fusion fuel; at a minimum the pellets would have to contain passive locator beacons. The interstellar probe would adjust its trajectory as required to ingest and utilize each successive fuel pellet. Alternately, and possibly more realistically, the fuel pellets themselves would each have a small amount of propulsion capability, enough for them to station-keep in a predetermined location, for example, maintaining position along a laser used as a guide-beam.

[Jordin] Kare noted that, at the velocities proposed for interstellar flight, nuclear fusion can be accomplished at the temperatures produced by impact. If a small pellet carried on the vehicle impacts a stationary pellet of fusion fuel, the result of the impact will be ignition of the fusion reaction, and potentially the liberation of a considerable amount of energy…”

When Centauri Dreams talked to Landis in 2003 about the fusion runway concept (Kare calls the idea the ‘Bussard Buzz Bomb’), the physicist elaborated on why he found the concept so intriguing. Kare’s work had indicated that it would take a velocity of 200 kilometers per second to light the starship’s main engines using these techniques. Landis pointed out that a spacecraft making a close pass by the Sun (virtually skimming the solar surface) could reach 600 kilometers per second, with the fuel pellets lined up so that the vehicle could start using them immediately after the solar pass.

How long would a fusion runway have to be to function? The answer depends on your spacecraft. An unmanned robotic probe that could endure intense gravitational forces would require a much shorter runway. If the craft is manned, the pellets would have to be strung out over a tenth of a light year to allow the probe to reach a cruising velocity of 30,000 kilometers per second. That translates into a forty-plus year journey to the Centauri stars.

Landis’ AAAS presentation is available as “The Ultimate Exploration: Approaches to Interstellar Flight,” in Y. Kondo, ed., Interstellar Travel & Multi-Generational Space Ships (Apogee Books, 2003).

ljk January 5, 2007 at 9:22

Should Google Go Nuclear? Clean, cheap, nuclear power (no, really)

Google engEDU

1 hr 32 min 37 sec – Nov 9, 2006

http://www.google.com

Google Tech Talks November 9, 2006

ABSTRACT This is not your father’s fusion reactor! Forget everything you know about conventional … all » thinking on nuclear fusion: high-temperature plasmas, steam turbines, neutron radiation and even nuclear waste are a thing of the past. Goodbye thermonuclear fusion; hello inertial electrostatic confinement fusion (IEC), an old idea that’s been made new. While the international community debates the fate of the politically-turmoiled $12 billion ITER (an experimental thermonuclear reactor), simple IEC reactors are being built as high-school science fair projects.

Dr. Robert Bussard, former Asst. Director of the Atomic Energy Commission and founder of Energy Matter Conversion Corporation (EMC2), has spent 17 years perfecting IEC, a fusion process that converts hydrogen and boron directly into electricity producing helium as the only waste product. Most of this work was funded by the Department of Defense, the details of which have been under seal… until now.

Dr. Bussard will discuss his recent results and details of this potentially world-altering technology, whose conception dates back as far as 1924, and even includes a reactor design by Philo T. Farnsworth (inventor of the scanning television).

Can a 100 MW fusion reactor be built for less than Google’s annual electricity bill? Come see what’s possible when you think outside the thermonuclear box and ignore the herd.

Speaker: Dr. Robert Bussard

http://video.google.com/videoplay?docid=1996321846673788606

Administrator January 5, 2007 at 10:39

More on the Bussard talk soon, probably early next week.

Edg Duveyoung January 5, 2007 at 15:24

There was a time when I attended these public meetings of “inventors” who claimed something outlandish — usually a “free energy” claim — they were looking for investors. And all of them seemed to be as legitimate as Bussard — not on their resumes, but in their assured manner, their comfort with jargon, and the “just need one more titch of a thingy and it’ll work I swear — would someone lend me a dime” shuck and jive. Been there, done that, and my tee shirt is now a dust cloth.

But here am I, believing again.

But there’s something hinky I tell ya. Why no support for this project that has all the eyes dotted and reports and data up the yinyang? It’d be easy for me to say, “Big oil has had a talk with Bushco and the kibosh has been put on the project.” In fact, there I said it — without any proof of course. But, still, despite my cynicism, what’s a few hundred million dollars these days to the government? The money is there, and though Bussard has slurped at the public trough for over a decade, he now has the results that our tax-dollars funded, but now the funding dries up? It seems hinky. If Big Oil wanted to kill this project, they might have just given more money to it but took over management enough to steer the project into years and years more research and thus keep it off the market until the oil wells run dry.

Meanwhile, a rocket engine that gets me to Mars in record time sits there.

Edg

Michael LaTorra January 13, 2007 at 14:24

I empathize with your experience and your feelings. When it comes to energy systems, green/renewable stuff is fine for households, but it’ll never bring us the concentrated, portable systems needed for a spacefaring civilization or even for advanced technology on Earth over the long haul.

With regard to the funding problems faced by Bussard, there is another possible explanation in addition to the Big Oil Conspiracy one. Recall that Bussard’s funding has always been coming from the Dept. of Defense (especially the Navy), and not from the Dept. of Energy. DoD wants portable, high energy-density systems that do not depend on oil. DoE is covering all sorts of energy generating (and conserving) systems, and it has put virtually all of its fusion money into the tokamak design, which is now going forward with the international ITER project soon to break ground in France.

The fact that Bussard only needs about $200 million over a decade means that it is easily afforded in a total US government annual budget of over $3 trillion, where a couple of hundred million dollars is little more than a rounding error.

I can’t help but feel, though — and this is getting back to the Big Oil influence on the Bush Administration — that Bussard would have gotten the money easily in a pro-science, pro-environment Gore Administration, where there would have been almost no likelihood of an unprovoked war in Iraq siphoning money into a bloody hell-hole.

But that’s just one man’s opinion.

Eric James January 13, 2007 at 19:17

Michael,

Pardon me if I take offense at your off-the-cuff insult to government oversight. I actually work for the goverment where I actually examine projects for their merit and I actually am responsible for authorizing millions of dollars in spending.

It’s not so easy to dismiss a couple of hundred million as “little more than a rounding error.” If this were true, every Tom, Dick, and Harry with criminal intent would be all over it (long before any legitimate researcher might have an opportunity to apply for it). Would you give our (the people’s) money to just anyone? Do you really think that’s how things work?

Did you consider that maybe the people are getting tired of funding these loser projects? Has any fusion experiment ever lived up to its initial expectations? Why should this one be any different? Why this one and not the next, or the next, or even the next..?

Perhaps you should be thanking the government rather than complaining. After all, it’s your (the people’s) money.

Michael LaTorra January 19, 2007 at 0:22

Eric,
Successful government oversight is commendable. As a taxpayer, I thank you for doing your job.

However, even a cursory Net search on the topic of government “waste, fraud and abuse” shows numerous examples totaling many billions of dollars per year. This is so well-known, it’s not even surprising anymore, with the stories of reconstruction monies for Hurricane Katrina damage and Iraq being merely the two largest current examples.

I would not “give the people’s money to just anyone” as you put it. Dr. Bussard has a plausible case for continued or even increased funding. The amount that he seeks is relatively small, when compared to the Katrina and Iraq cases mentioned above, coming in at only a couple of hundred million dollars. If his research fails to pan out, we will not have lost too much. But if his work succeeds and his claimed results produce clean, cheap and abundant power, then the money spent will be repaid many, many times over.

Don’t you think it’s worth considering?

Regards,
Mike

Eric James January 19, 2007 at 2:31

Michael,

The waste you are talking about is mostly pork barrel and other politically motivated spending. Scientists haven’t a chance at this money. It’s generally used for political favors and political showmanship. It’s inefficiently distributed because the politicians rarely bother to setup an efficient mechanism to disperse these short term expenditures. It’s wasteful and stupid, but that’s what we get for voting for the guy with the whitest teeth and the shiniest hair.

Now if you think you can get your local white teethed, shiny haired representaive to put science ahead of his own self interests, then have at it. Good luck!

Unfortunately, I still don’t see any incentive in backing Bussard. Fusion has turned out to be little more than a pipe dream (so far). Why should his system be any different?

Adam January 19, 2007 at 4:01

Eric

You’re such a party pooper.

Adam

Eric James January 19, 2007 at 23:32

Adam,

Let’s have a techno-fusion rave! Party on!

Peter Gardner November 12, 2010 at 23:29

How will a spacecraft slow down before reaching its destination? If it is travelling at even a small fraction of light-speed it will have to begin decelerating at the mid-point of its journey. That too will require the expenditure of energy equal to the amount which brought it up to speed.

-Peter Gardner

Paul Gilster November 13, 2010 at 8:45

Deceleration is extremely difficult, not least of all because you have to boost the fuel needed for deceleration along with the original payload — the rocket equation shows that the initial fuel mass becomes vast beyond comprehension when we’re talking interstellar. But there are some deceleration options that may be feasible, one being a magnetic sail that brakes against the destination star’s stellar wind. This one, closely studied by Dana Andrews and Robert Zubrin, among others, seems like the best alternative at the moment.

Comments on this entry are closed.

{ 2 trackbacks }