Carnival Notes: Fusion and Dark Energy

by Paul Gilster on December 27, 2008

Is nuclear fusion easier to exploit in space than on Earth? Surprisingly, harnessing the power that drives the Sun may be a simpler challenge in propulsion terms than creating clean, safe power supplies for our planet. So says Brian Wang, whose NextBigFuture site speculates on fusion development (and, I should add, also hosts this week’s Carnival of Space). Wang, who has been following fusion development for years, notes key differences between space and planet-side technologies, one of them being that dealing with stray neutrons is easier when you can vent them directly to space, rather than developing reactor materials that can both exploit their energy and ensure maximum safety.

We know that a fusion power plant on Earth must operate for many years, working with steady state fusion that affords low maintenance and maximum reliability. Space, however, offers a different set of goals, with duty cycles in months before major overhauls, and the possibility of interesting pulsed fusion options as well. In terms of creating a clean, high vacuum, space is obviously a simpler environment than a planetary surface. Brian’s conclusion: Generating propulsion is a lesser challenge than producing electricity, while other non-electric uses of fusion, such as creating relatively inexpensive PET isotopes for use in cancer diagnosis, are equally promising offshoots of the search for fusion power.

Also of note in this week’s carnival is Dave Mosher’s post on dark energy, which offers up links to Discovery News stories covering the topic in some detail, with discussion of how dark energy is studied, where the research is headed, and why it has drawn its share of skeptics. It’s a useful package, one highlighted by James Williams’ quick video overview of the question and the ever-reliable Ray Villard’s look at the ultimate fate of the cosmos. For still more on dark energy, have a look at the video below, put together by Alexey Vikhlinin of the Smithsonian Astrophysical Observatory, describing the latest results in this new and compelling science.

The monastic plainchant in the background is a nice touch. And why not — we’re talking about principles that have shaped the growth of matter in the cosmos at the largest scales and over immense periods of time. A certain sense of awe is both welcome and inescapable.

{ 9 comments }

Adam December 28, 2008 at 1:35

Detonating nukes behind a pusher plate has always been easier than “fusion in a jar” that tokamak physicists have been trying to achieve. Whether sustained fusion can make a jet for a drive has yet to be demonstrated. Perhaps Winterberg’s non-fission triggered fusion will eventually make a pulse thruster, but ITER style reactors are too damn heavy for space. Bussard Polywells? Wait and see.

James M. Essig December 29, 2008 at 0:13

Hi Folks;

Space based nuclear fusion for powering star ships is in essence, a technology that became available with appropriate engineering refinements with the development of the hydrogen bomb.

For deep Oort cloud missions and space ark like missions to our nearby stellar neighbors, I think that nuclear bomb pulse rockets should definately be looked at again in more detail. Early thermonuclear devices had very hgh yields, although their mass specific yields were not well optimized. A kilogram of U-235 fully fissioned will yield about 25 kilotons of TNT equivalent whereas the most exothermic of known fusion fuels will yield about 175 kilotons per kilogram. Thus, ironically, the U.S. military’s quest for a pure fusion bomb as has been the subject of various non-classified reports might be just what we need to reach for the stars and actually get there.

Even better than carrying all of the nuclear fusion fuel onboard from the start of the the mission, would be what we have all come to know as the fusion pellet runway. The pellets could be detonated behind the craft as it passed the given pellets, or in the case that the craft would be traveling at relativistic velocities so that the electromagnetic radiation released in the fusion explosion and other debris would either not reach the pusher plate or be so dopplar redshifted such that only inconsequenctial kinetic energy could be imparted to the craft by the explosions, the fusion pellets could be detonated within a reaction tube or chamber that runs the length of the ship wherein the aspect ratio of the tube would permit the radiation released to be largely collected by an energy absorbing material and/or field thus perhaps permitting very high gamma factors to be obtained.

It occured to me that detonating pure fusion devices near the proximity of the ship as it passed by in some sort of plasma bubble, magsail type bubble, or some other topological electromagnetic field configuration might enable a more effective collection of energy from the plasma produced by nuclear fusion devices of the approprately fueled types. I am not sure how one would configure this bubble, how ever, the concept popped into my mind just as I was finishing the above paragraph.

Regardless of whether nuclear bomb pulsed driven fusion ships, or some sort of open ended nuclear fusion reactor rocket (which to me seems much more doable than the closed tokamak type reactors that are used in current nuclear fusion reactor test facilities), we need to look at the ubiquitous presence of hydrogen throughout our universe, and throughout any multiverse composed of identical laws to that of our universe, as a truely cosmic energy source that might make for good fusion rockets in a couple of short decades should we choose to embark on a Apollo Program like financial scaled project to develope such vehicles.

As a son of a now deceased career navy man, who later worked under the late Admiral Rickover for the Navsea Naval Reactors Program, I see nuclear energy as fun and very useful. Nuclear fusion is fun or can be when we consider the perhaps infinite quantity of fusion fuel within our universe to power our future starships.

Thanks;

Jim

ljk December 30, 2008 at 13:42

On Dark Energy and Dark Matter (Part I)

Authors: Shlomo Barak, Elia M Leibowitz

(Submitted on 24 Dec 2008)

Abstract: Phenomena currently attributed to Dark Energy (DE) and Dark Matter (DM) are merely a result of the interplay between gravitational energy density, generated by the contraction of space by matter, and the energy density of the Cosmological Microwave Background (CMB), which causes space dilation.

In the universe, globally, the gravitational energy density equals the CMB energy density. This leads to the derivation of the Hubble parameter, H, as a function of the scale factor, a, the time, t, the redshift, z, and to the calculation of its present value. It also leads to a new understanding of the cosmological redshift and the Euclidian nature of the universe. From H(t) we conclude that the time derivative of a is constant. This is in contrast to the consensus of the last decade.

This result is supported by the fit of our theoretically derived flux from supernovae (SN) as a function of z, with observation. This flux is derived based on our H(z) that determines DL, the Luminosity Distance. We obtain this fit without any free parameters, whereas in current cosmology this fit is obtained by using the dependent free parameters Omega_M and Omega_Lambda.

Comments: 12 pages, 1 figure

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0812.4561v1 [astro-ph]

Submission history

From: Shlomo Barak [view email]

[v1] Wed, 24 Dec 2008 18:24:35 GMT (272kb)

http://arxiv.org/abs/0812.4561

ljk January 4, 2009 at 1:12

Dark Stars: the First Stars in the Universe may be powered by Dark Matter Heating

Authors: Katherine Freese, Peter Bodenheimer, Paolo Gondolo, Douglas Spolyar

(Submitted on 28 Dec 2008)

Abstract: A new line of research on Dark Stars is reviewed, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion.

Weakly Interacting Massive Particles, which may be there own antipartmers, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel.

Comments: 6 pages, Eighth UCLA Symposium: Sources and Detection of Dark Matter and Dark Energy in the Universe, proceedings

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0812.4844v1 [astro-ph]

Submission history

From: Katie Freese [view email]

[v1] Sun, 28 Dec 2008 20:12:01 GMT (98kb)

http://arxiv.org/abs/0812.4844

clay January 4, 2009 at 19:14

Bussard fusion. I just read about this research. I am a 20 year M.E. very familiar with the R&D process, success, failure and the many things that get in the way of practical success. As I read through the history of Dr. Bussard and Energy/Matter Conversion Corp, it makes me wonder if Dr. Bussard was really onto something big, and got trapped in a political trap, when the funding was cut. Or was wasting time on science fiction…. I am no stranger to commercial success. (Half a dozen patents, and lots of products in the marketplace) However, I have observed and been involved in promising technologies, only to watch helplessly as they are scuttled from within, or by fabrication requirement impracticalities & very poor design of experiments, or politics. So what is the real story of what Dr. Bussard was doing?

Did the EMCC funding get cut because they were wasting it? Or did they stumble onto something that ultimately would embarrass the Navy? Or did EMCC simply find the solution that the Navy needed, so then they no longer needed EMCC?

clay

ljk January 8, 2009 at 2:00

Findings of the Joint Dark Energy Mission Figure of Merit Science Working Group

Authors: Andreas Albrecht, Luca Amendola, Gary Bernstein, Douglas Clowe, Daniel Eisenstein, Luigi Guzzo, Christopher Hirata, Dragan Huterer, Robert Kirshner, Edward Kolb, Robert Nichol

(Submitted on 6 Jan 2009)

Abstract: These are the findings of the Joint Dark Energy Mission (JDEM) Figure of Merit (FoM) Science Working Group (SWG), the FoMSWG. JDEM is a space mission planned by NASA and the DOE for launch in the 2016 time frame. The primary mission is to explore the nature of dark energy.

In planning such a mission, it is necessary to have some idea of knowledge of dark energy in 2016, and a way to quantify the performance of the mission. In this paper we discuss these issues.

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0901.0721v1 [astro-ph]

Submission history

From: Edward W. Kolb [view email]

[v1] Tue, 6 Jan 2009 21:25:30 GMT (55kb)

http://arxiv.org/abs/0901.0721

Z monkey January 15, 2009 at 9:12

I’m wondering if we could use a Z machine as a fusion drive. In 2006 a successful experiment has been conducted in Sandia and in about 100 nanoseconds was produced energy for 80 years. It solves the energy crisis once and for all, no need of ITER. A spacecraft with this king of power could be used as fast Interplanetary vehicle…. and interstellar.

ljk January 19, 2009 at 13:06

Did dark energy give us our cosmos?

17 January 2009 by Jessica Griggs

Magazine issue 2691.

OUR universe may have arisen from seeds preserved in a universe that existed before the big bang – all thanks to dark energy.

One of the models put forward to explain how the universe began proposes that it is just the latest phase in a never-ending cycle. Proposed in 2002 by Paul Steinhardt of Princeton University and Neil Turok from the University of Cambridge, the model argues that our universe exists on a 3D region called a “brane” separated from similar branes by a fourth spatial dimension.

Under the right conditions, these branes collide, triggering a big-bang-like event. After the collision, the branes bounce apart, before another collision occurs many billions of years later.

Full article here:

http://www.newscientist.com/article/mg20126914.100-did-dark-energy-give-us-our-cosmos.html

ljk February 11, 2009 at 10:52

Apparently using some dark energy could help us go FTL:

http://www.cosmosmagazine.com/news/2141/dark-energy-spacecraft-could-fly-faster-light

There are a few tiny technical issues, like trying to obtain actual dark
energy to run your star drive, plus, to quote from the above article:

“Even if it were possible, faster-than-light travel would still take an enormous amount of energy. It would consume the entire mass of Jupiter to move a spaceship 10 m at warp speed, the researchers said.”

Well, there are all those superJovian exoplanets we’ve been finding since 1995….

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