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Remembering Robert Bussard

A note from James Benford, soon to be followed by e-mail from other interstellar advocates, tells me of the death of Robert Bussard. The creator of the Bussard ramjet concept, Bussard (1928-2007) died of cancer in Santa Fe just a few days ago. Benford, who knew Bussard for forty years, recalls his open attitudes and deep technical insight, adding “He was still sharp as a pin into old age.” We should all be so lucky.

Recently we’ve seen a lot of discussion about Bussard’s fusion ideas, but it’s the ramjet that I return to as I think about him. If you collect classic papers, as I do, here’s one for you: Bussard’s “Galactic Matter and Interstellar Spaceflight” in Acta Astronautica 6 (1960), pp. 179–94. Imagine a scoop created by a magnetic field that sucks in interstellar hydrogen ionized by a forward-firing laser. The result is fed into a fusion reactor. Get the vehicle up to about six percent of light speed and you could light that engine, with presumably amazing results.

Bussard ramscoop

At least, that was the idea. Assume one hydrogen atom per cubic centimeter as the density of the interstellar medium and a one-ton probe would demand a scoop 6,000 kilometers in size, but to be realistic about interstellar densities, you’d probably need one as large as 60,000 kilometers to account for hydrogen density variations. The concept was indeed breathtaking even if later work made its success dubious (drag is a major problem, leading to the idea of using magnetic sails for deceleration into a target system).

But imagine going at one g continuously. When Carl Sagan went to work on that one, he got to Alpha Centauri in three years (ship time, obviously), but as the vessel picked up speed, things got more and more interesting. The Andromeda galaxy could theoretically be reached in about 25 years, assuming you’re willing to live with the two million years that passed in the interim back on Earth. Poul Anderson’s starship Leonora Christine in the novel Tau Zero grew directly out of Bussard’s idea.

Image: A Bussard ramjet could theoretically get a crew to Andromeda. Credit: ESA/ITSF/Mancu.

Anderson’s description of the Bussard ramjet at work is superb:

The ship was not small. Yet she was the barest glint of metal in that vast web of forces which surrounded her. She herself no longer generated them. She had initiated the process when she attained minimum ramjet speed; but it became too huge, too swift, until it could only be created and sustained by itself … Starlike burned the hydrogen fusion, aft of the Bussard module that focused the electromagnetism which contained it. A titanic gas-laser effect aimed photons themselves in a beam whose reaction pushed the ship forward—and which would have vaporized any solid body it struck. The process was not 100 per cent efficient. But most of the stray energy went to ionize the hydrogen which escaped nuclear combustion. These protons and electrons, together with the fusion products, were also hurled backward by the force fields, a gale of plasma adding its own increment of momentum . . . The process was not steady. Rather, it shared the instability of living metabolism and danced always on the same edge of disaster…

Suffice it to say that if you haven’t read Tau Zero (and yes, we did name the Tau Zero Foundation after the book, and Poul’s wife Karen is on our board of directors), then you should make haste to your nearest bookseller or library. I think Bussard must have taken great pleasure from reading Tau Zero, as well as knowing that his stunning starship concept would galvanize theoretical research into interstellar propulsion for decades to come. He’s been part of my thinking on interstellar matters for the last forty years, a loss everyone involved in our deep space future will take to heart. Our thoughts and condolences go out to his family.

Comments on this entry are closed.

  • Arvakyr October 9, 2007, 16:16

    Mr. Bussard’s passing will not be lost…I’ll see to it.

    Arvakyr of EXOTERRENE Arts

  • M. Simon October 9, 2007, 18:45

    I have links to technical forums and eulogies here:

    Dr. Bussard has died.

    I will be adding yours. Moving.

  • Ronald October 10, 2007, 4:37

    I am saddened by the passing away of this visionary.

    I just hope that his work on the Polywell IEC fusor (which, I learned recently, was just getting follow-up funding from the US Navy) will continue.

  • Lubo October 10, 2007, 5:59

    Now with his death, the Bussard’s Polywell fusor wont’t be complete any time soon….. :(

  • Adam October 10, 2007, 9:10

    Hi Lubo

    Dr.Bussard had a lot of co-workers on the Polywell and the Navy backing them up, so don’t despair too soon. The Polywell Fusor will be Dr.Bussard’s legacy to the future, to the stars and all who would reach for them.

  • Kurt9 October 10, 2007, 12:45

    Bussard’s group got funding from the Navy to continue with the WB7 and WB8 work. Appearently there are two physicists from Los Alamos, one who is a longtime friend of Dr. Bussard, who are continuing the polywell work. So, hopefully, there will be little “institutional memory loss” as a result of Dr. Bussard’s untimely passing.

    There are other fusion techniques being pursued. One of the more significant efforts is Tri-Alpha, which is trying to develop a variant of the reverse field configuration for Boron-hydrogen fusion. They are being financed by two billionaires, one is believed to be Paul Allen.

  • george scaglione October 10, 2007, 15:12

    kurt,i have not yet taken the opportunnity to say that i too feel the loss of this great man.thank goodness his work continues! your friend george

  • VaGent October 11, 2007, 3:05

    Regular people are the first to recognize greatness!

  • ljk October 11, 2007, 9:36

    Can you qualify that statement?

  • David Langlois October 17, 2007, 7:58

    His vision will live on.

  • ljk October 28, 2007, 1:03

    Orion Arm’s tribute to the Bussard ramjet:


  • Al Jackson October 28, 2007, 12:53

    I too knew Bob Bussard , not real well, but we spoke a few times, he was an amazing and very nice man.
    First thing to remember about him was that he was one of the premier experts in nuclear rocket propulsion
    in the 1950’s and 1960’s.

    One very important thing about the Interstellar Ram Jet. One of the biggest bugaboos about interstellar flight
    before 1960 was the mass ratio problem. Even though people had shown using Fission, Fusion and Anti-Matter
    the problem could be solved in part. Still critics abounded, “Utter Bilge” muttered the Astronomer Royal.
    Bussard swept the problem totally away with the Interstellar Ram. It did not sweep away the technological engineering
    problems, but it did not violate any basic physics ….always the hall mark of a sound engineering concept no matter how
    hard it is to do!

  • ljk November 24, 2007, 0:18

    Fusion propulsion if Bussard IEC fusion works

    Work is continuing towards Robert Bussard’s vision of inertial electrostatic fusion.


  • Geoffrey Thomas February 4, 2008, 20:38

    I’ve been working on some mathematical models if we slowed down in time enough to observe the hour hand of a clock moving a full circle in a second.

    Apparently we can slow down in time slower than that, since there’s no reason why not we can be so slow to observe the hour hand move a full circle “many times per second”.

    It’s inevitable from our point of view at least, we can never reach a point time has stopped despite the fact from the environment’s time frame point of view is concerned we appear to be frozen in time.

    The opposite applies if moving though time fast enough to observe the second hand slowed to equal the hour hand would normally do in if we were in our normal time frame.

    It’s inevitable mathematics predicts the number of centuries pass by the time the hour hand hand moved a full circle. The figure could be so large universe would not even that old. We could never reach a point time has stopped.

    It does raze the question of the theory of time in the center of black holes (singularities) and before the big bang that’s supposed to have created the universe.


    First session Slider Fan. Geoffrey Thomas

  • ljk February 8, 2008, 11:56

    Venture capitalist says nuclear fusion is coming

    A picture from the patent filing for what General fusion is trying to build with backing from Chrysalix Energy Venture Capital. GF will build a ~3 meter diameter spherical tank filled with liquid metal (lead-lithium mixture). Rams use compressed steam to accelerate pistons to ~50 m/s. Make compression wave in the liquid metal. Microsecond of fusion once per second. Note: This could be considered like a variant of “steam punk nuclear fusion” made real if it works.

    “Within five years, large companies will start to think about building fusion reactors,” Wal van Lierop, CEO of Chrysalix Energy Venture Capital, said in an interview at the Clean Tech Investor Summit taking place here this week. In three to four years, scientists will demonstrate results that show that fusion has a 60 percent chance of success, he said.

    Lierop has backed General Fusion’s Magnetized Target Fusion (MTF) model. An electric current is generated in a conductive cavity containing lithium and a plasma. The electric current produces a magnetic field and the cavity is collapsed, which results in a massive temperature spike. MTF has an advantage over other fusion techniques in that the plasma only has to stay at thermonuclear temperatures (150 million degrees Celsius) for a microsecond for a reaction to occur.

    Full article and diagrams here:


  • ljk May 14, 2008, 9:32

    Possible test fusion reactors developed for sale

    May 13, 2008

    The lead Bussard Fusion Reactor (BFR) experimenter is
    considering making turnkey fusion test reactors for 500,000
    to 1 million dollars.

    One of the things we have been considering is selling a
    “turnkey” version of the WB-7. In this case we would design,
    build, license and deliver an operating Polywell, probably on
    the scale of the present machine. Operator training and tech
    support would also be part of the deal. These devices could
    be funded through government grants (we have found a
    mechanism) or privately. I think we could do a turnkey
    machine for a ~ $500k-$1000k depending on how many
    people are interested.

    Full article and links here:


  • ljk June 13, 2008, 14:08

    Latest update on Bussard Fusion Prototype WB7


    June 12, 2008

    The Emc2 team has been ramping up its tests over the past few months, with the aim of using WB-7 to verify Bussard’s WB-6 results. Today, Nebel said he’s confident that the answers will be forthcoming, one way or the other.

    “We’re fully operational and we’re getting data,” Nebel said. “The machine runs like a top. You can just sit there and take data all afternoon.

    Nebel may be low-key about the experiment, but he has high hopes for Bussard’s Polywell fusion concept. If it works the way Nebel hopes, the system could open the way for larger-scale, commercially viable fusion reactors and even new types of space propulsion systems.

    “We’re looking at power generation with this machine,” Nebel said. “This machine is so inexpensive going into the 100-megawatt range that there’s no compelling reason for not just doing it. We’re trying to take bigger steps than you would with a conventional fusion machine.”

    EMC2 built the laboratory and an experiment in nine months. If a working scaled up production system could be built in comparable time then the main part (not the site preparation and power lines) of any new reactor could be produced in 9 months or less.

    This site had an article about the space propulsion breakthrough that this fusion system would enable if it is successful:


  • ljk July 10, 2008, 12:31

    The next Bussard IEC fusion reactor could be 100MW size producing
    net energy

    July 07, 2008

    Dr Nebel is talking about is a 1.5 meter 100 MW net power fusion reactor Dr Nebel has said he is getting good data from the WB7 test device. He is under a publishing embargo and cannot discuss the data, (neutron counts) but he has said the next device might as well be a 100MW version.

    This 100MW version may only cost $3 million to make. The implication is that Dr Nebel and his team are getting very good results. Hopefully this speculation is confirmed in August or September of this year with results published and next stages funded.

    Full article here:


  • ljk August 15, 2008, 22:04

    A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program

    ITER presents the United States and its international partners with the opportunity to explore new and exciting frontiers of plasma science while bringing the promise of fusion energy closer to reality.

    The ITER project has garnered the commitment and will draw on the scientific potential of seven international partners, China, the European Union, India, Japan, the Republic of Korea, Russia, and the United States, countries that represent more than half of the world s population. The success of ITER will depend on each partner s ability to fully engage itself in the scientific and technological challenges posed by advancing our understanding of fusion.

    In this book, the National Research Council assesses the current U.S. Department of Energy (DOE) plan for U.S. fusion community participation in ITER, evaluates the plan s elements, and recommends appropriate goals, procedures, and metrics for consideration in the future development of the plan.