Author Topic: Fusion with space related aspects thread  (Read 584775 times)

Offline PlanetStorm

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Re: Fusion with space related aspects thread
« Reply #20 on: 12/01/2006 09:10 AM »
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HD209458 - 30/11/2006  4:43 PM

Back on topic a little bit; it has always been my impression that IEC fusion like this was useful as a neutron source, but not for power generation (or propulsion). IIRC, Bussard's main claims about the power of his machine were denominated in neutron counts, which seemed to me to support this view of IEC as primarily a neutron source.

Do the nuclear enginners here know if this is true? Or is Bussard et. al doing something different, that is causing his machine to generate power?

The thingt he is doing that is different is that he has reduced losses by an enormous factor. By removing the grid, or more accurately, by shielding the grid with magnetic fields, he keeps the electrons from hitting absorbers and so they can cycle 100,000 times.

The neutron count thing is a red-herring. In the demo devices, he deliberately used "fuels" that generate large neutron fluxes because the neutrons provide such a good diagnostic that fusion has actually occurred. Utlimtately, though, his goal is to use boron fuel and essentially eliminate neutron production altogether. This would be perfect for energy generation but not much good in his small scale demo devices because, as the gain is so small (remember he says that gain scales as size ^ 5), there would be no detectable energy production and hence no way of knowing that fusion has occurred.

If I had 200 million to spare, I would seriously consider giving it to him!


Offline PlanetStorm

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Re: Fusion with space related aspects thread
« Reply #21 on: 12/01/2006 09:13 AM »
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braddock - 1/12/2006  1:23 AM

This is a very interesting video.  I'm skeptical of the potential, but regardless I just learned an awful lot about interesting fusion devices while watching.

There is a fairly critical critique of the presentation here:
http://futurepower.org/nuclear_energy_experiments.html
Don't know how much credence to give the critique or the presentation, but I found both interesting.

Does anyone have links to the "8 or 9 papers" he mentions that discuss using their fusion technique for space travel?
Or the main lessons learned paper he mentioned that was to embody his lessons learned in the astronomical proceedings?

I don't think that critique shows any insight into the potential of the device. Mostly psychobabble IMO.


Offline braddock

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Re: Fusion with space related aspects thread
« Reply #22 on: 12/01/2006 09:46 AM »
The critique was sobering counter-balance, although I think it was a little too critical of him personally -- it's not like Robert Bussard isn't a world famous physicist already (Bussard Ram Jet, Asst Director of Atomic Energy Commission, etc).

The problems I have with the presentation are:

1) No energy accounting presented - the magnetic fields would presumably take much more energy than the old grid approach.  Where is break-even?

2) No cost proposal presented - in fact he mentioned that his cost slide was from 1994, complete with old crossed out prices and penciled in new ones!

3) A quarter of a millisecond reading of unexpected peak neutron emissions just before the prototype blew up and they shut down the lab - not exactly good scientific proof there.

4) He needs to publish everything.  Anyone who fully funds him on a $200 million adventure without a few years of peer-review publication is crazy.

By all means, someone give him $2 million to prove what he thinks he has achieved.  That is all he says he wants to continue research for one year ($5 million to ramp up the scale more quickly).  But he only mentions the $2 million in the Q&A afterwards...

Offline PlanetStorm

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Re: Fusion with space related aspects thread
« Reply #23 on: 12/01/2006 10:42 AM »
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braddock - 1/12/2006  10:29 AM

The critique was sobering counter-balance, although I think it was a little too critical of him personally -- it's not like Robert Bussard isn't a world famous physicist already (Bussard Ram Jet, Asst Director of Atomic Energy Commission, etc).

The problems I have with the presentation are:

1) No energy accounting presented - the magnetic fields would presumably take much more energy than the old grid approach.  Where is break-even?

2) No cost proposal presented - in fact he mentioned that his cost slide was from 1994, complete with old crossed out prices and penciled in new ones!

3) A quarter of a millisecond reading of unexpected peak neutron emissions just before the prototype blew up and they shut down the lab - not exactly good scientific proof there.

4) He needs to publish everything.  Anyone who fully funds him on a $200 million adventure without a few years of peer-review publication is crazy.

By all means, someone give him $2 million to prove what he thinks he has achieved.  That is all he says he wants to continue research for one year ($5 million to ramp up the scale more quickly).  But he only mentions the $2 million in the Q&A afterwards...

Give him a break, he had only one very rushed lecture in which to present a decade of work: you can't blame him for not filling in all the details, and he wasn't trying to build a full buisiness case, just outline the technology and its potential.

But in detail:
(1) energy accounting was covered in essence by the scaling law for gain and fusion output.

(2) He outlined his development plan and the funds needed, in as much detail as could be expected in the time allotted. Besides, he is clearly a physicist and his time is best spent doing physics - leave the bean counting to someone else!
 
(3) Where else are the neutrons going to come from? Also, evidence for fusion was obtained from two runs, if I understood him right. Wish I had been there to ask some questions though.

(4) Of course no one is going to give him 200 million right of the bat. I think he should rebuild his old 1/8 scale device and run some more tests, just
to counter worries like your point (3), and this looks like it could be done for a few million. He naturally wants to go to full scale device with continuous operation as the next step because he is convinced that there is nothing else to learn from small devices, but that is the only major problem I have with his argument. My other major problem is that I don't have a few million to give him!



Offline josh_simonson

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Re: Fusion with space related aspects thread
« Reply #24 on: 12/01/2006 08:16 PM »
As I understand it, Google's 'foundation' for philanthropic purposes is not a 'non-profit' organization - when it can it is supposed to actively attempt to make money by helping people.  Long-shot, high payoff technology investments such as this are the ideal of philanthropy with such a mindset.  

It is suspicious that they pulled a rabbit out of the hat in the last hours of funding, that's the main concern I'd have.  

He seems to believe that there's a tokamak conspiricy wherein the fusion community will work to quash his research because it threatens the tokamak workforce (reminicent of shuttle workforce problems in NASA).

There's a petition online for congress to restore funding to this research, and $2m isn't all that much, I can't imagine him having to talk to too many billionaires and foundations that are hostile to the energy industry to find someone willing to fund or partially fund this work - especially considering that success could make them multi-billionaires.

Offline PurduesUSAFguy

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Re: Fusion with space related aspects thread
« Reply #25 on: 12/02/2006 08:27 PM »
Well there is no doubt about what he says in refrence to their being a tokomak 'mafia'. There has been so many physicist who have staked their carreers on toridal magnetic confinement that there is an ingrained bypass in the plasma physics community against any nonconventional containment method.

Offline Tony Rusi

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Re: Fusion with space related aspects thread
« Reply #26 on: 12/14/2006 09:04 AM »
Robert Bussard not only concieved of a fusion ram jet rocket. He designed and tested the first US fission rocket. It is kind of sad that this genius is not more well known. Here is an article that Tom Ligon wrote about his work just before it went under wraps. It makes you wonder what else the DOD has cooking in some closet.


http://web.archive.org/web/20011213171457/http://torsatron.tripod.com/fusor/fusor.html


Here is the only post Brussard has made on the fusor.net page.

http://www.fusor.net/board/view.php?site=fusor&bn=fusor_announce&key=1143684406


Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #27 on: 01/23/2007 10:13 PM »
Speak of the devil and in he walks.  Tom Ligon here.
A better copy of my December 1998 fact article in _Analog_ can be found at fusor.net, in their Newbie section.  It is called "The World's Simplest Fusion Reactor."  The other copies are pirated scans, no figures, and full of typos.

There's a lot of buzz on his October 2006 paper and the Google talk on this subject.  Links below include the talk, the paper, and a fairly new Wiki that I've been contributing to.

http://www.askmar.com/Fusion.html

http://en.wikipedia.org/wiki/Polywell

Goldin had something in the works, I can't find any references now, called "Strategy F", the idea being to get manned missions to Mars using fission or fusion propulsion.  The fission option was essentially NERVA, developed from Bussard's original fission rocket work (Rover, Kiwi-A).  The two fusion options were Bussard's electrodynamic p-B11 approach (see the paper linked at askmar) and the thought of strapping ITER on a rocket (hah!).


Offline Tony Rusi

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Re: Fusion with space related aspects thread
« Reply #28 on: 01/28/2007 06:12 PM »
Tom!

Nice to see you here! What have you been up to lately? Looks like Bussard has gotten some international recognition for his work.

http://www.science.edu/TechoftheYear/TechoftheYear.htm

I have gotten an e-mail from Jim Benson that indicates that they don't intend to let Bussard's work lie fallow too much longer.  But Benson is still looking for big investors.

http://peswiki.com/index.php/Directory:Inertial-Electrodynamic_Fusion_Device

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #29 on: 01/28/2007 08:26 PM »
Yes, when Dr. Bussard had to close the lab, SpaceDev was kind enough to store the equipment and hire 3 of the people who made the thing work.  Jim would love to pick up the work an run with it.

I'm working for Athena Technologies on UAV control systems.  Morphing aircraft with LMA, Mars Flyer High Altitude Demonstration Drop, and neat stuff like that.  I just had a story accepted at Analog and am working on a sequel to "The World's Simplest Fusion Reactor."  Hopefully, by the time that publishes, somebody will have had the wisdom to fund this.

Looking at the data EMC2 produced, WB-6 ran at less magnetic field than any of the earlier models, and produced fusion as low as 5 kV, copious fusion at 12.5 kV.  Fusors don't generally make easily-detectable fusion on DD that low.  WB-6 is in a class by itself as IEC machines go.

Wikipedia also has an article and some discussion of this under PolyWell.  I contributed some to that.  http://en.wikipedia.org/wiki/Polywell

"The World's Simplest Fusion Reactor" was published with the intent of getting folks familiar with IEC, and getting some kids building them as science projects.  It begat an amateur fusion movement now centered around fusor.net, and to date 8 high-schoolers have made measurable fusion with Fusors, and two more are preparing to.  Michael Li won 2nd place in the Intel Science Talent Search in 2003 for his.

That wiki in your post has a couple of bugs that I've noticed so far.  The ions are actually "confined" by oscillating thru an electrodynamic potential well.  They are not affected significantly by the magnetic field.  It is the electrons creating the potential well that are confined with the aid of the magnetic fields, by virtue of the field both insulating the anode that accelerates them, and by formation of a trapping effect called a "wiffle-ball"

EMC2 started out in Manassas, VA, but has not been there in years.  The successes were in San Diego, and anyone wishing to contact Dr. Bussard at this time would use the Santa Fe address, or contact Jim Benson at SpaceDev.

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #30 on: 01/28/2007 09:23 PM »
Tony,

To answer your questions posed under the Hawking topic ...

I worked for Dr. Bussard for about 5 and a half years.

Dr. Nicholas A. Krall has been working with Dr. Bussard on this essentially from the start.  His reputation as a theoretical plasma physicist is on par with Bussard's as a designer.

If I had 200 million and enough left over to live on comfortably, this thing would be funded already.

Bussard's approach is essentially a "perfect Hirsch/Farnsworth Fusor".  It is a spherical convergent focus electrodynamic particle accelerator.  It doesn't work on maxwellianized heat, it works by raising ions to fusion velocity and focussing them on a central convergence point.  Ions not making fusion collisions recirculate, and those making elastic non-fusion collisions have their energy re-equalized by a collisional phenomenon that occurs near the outside of the potential well.  The result is long ion lifetime at high kinetic energy.

I have a little Hirsch/Farnsworth fusor that puts out 3000 fusions per second at 18 kV on DD.  At 12.5 kV, the highest drive voltage WB-6 was run at, most fusors put out so little you have to beat the counting statistics to death to even detect the output, but WB-6 actually put out (for about a quarter of a millisecond at a time) a screaming load of neutrons.  Yesterday I read a report that noted that one of the tests was actually run at 5 kV and produced a neutron count (26000 fusions per count) in the 1/4 millisecond or so that the deep potential well existed.  Realizing that the statistical significance of one count is +/- 100%, it still floored me.  NOBODY does DD fusion at detectable levels at 5 keV.  The reason it could happen is that the machine naturally produces head-on collisions at fusion energies in the region around the central convergence point.

I'm not at all worried by the fact WB-6 was a pulsed machine.  I built and ran the smaller WB-3, which was perfectly capable of running essentially continuously at about 1/2 of the WB-6 parameters.  Correctly built, larger machines should be able to run continuously.

The scaling formulas for output tend to go up as B^4R^3, and gain goes up at B^4R.  Bussard expects B to scale with R, which is probably a gross under-estimate once you get into the superconductingmagnets he intends to use.  WB-6 ran most of its successful tests below 0.1 T.  The scaleup he wants to do for p-B11 is from R of 0.15 meters (WB-6) to R of 2 meters.  ITER recently tested one of their magnets at 13 T, and I think 25-30 T is achievable.  If his output scaling is correct, even scaling up WB-6 to the larger sizes and fields suggests the thing is going to run, and WB-6 was almost certainly not running in an optimal fashion.

Unless he is missing something really important, the thing should work.   Most technical criticisms people have mounted of this thing wind up referencing a master's thesis by Todd Rider, and to the best of my knowledge, the points Rider raised have all been addressed.  Some were were wrong or not applicable to this machine, one important one the machine itself corrects via a collision mechanism of the ions near the MaGrid, one is insignificant with proper design.  The electron loss problem in cusps was essentially correct, but applies only to the HEPS-style machines.  The MaGrids (which WB-6 is) are immune to it because they recirculate electrons lost to the cusps.  And Rider never said it wouldn't work, he just hoped a way could be found to overcome the problems he felt he had detected.

Offline Tony Rusi

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Re: Fusion with space related aspects thread
« Reply #31 on: 01/29/2007 04:58 AM »
Tom,

Thanks for shedding a little light on this. I just can't figure out why more scientists and engineers are not interested. I can't think of anything that would improve the quality of life of the children of the world more. Maybe the press is gun shy from the cry wolf effect of cold fusion.

Bussard's own admission, that for years they padded the DOE budget of the Tokamak to siphon off a little for programs that might actually work, does not engender trust with the press and the lay public, I am sure. Do you know any of Bussard's lab people that are working with Benson? Has Benson started any work on rebuilding WB-6 or starting WB-7 or 8? Or is all the equipment still in mothballs?

Are Bussard and Krall still working on this with Jim Benson? What is Krall up to now? Do you know how to contact him? Why did Bussard say he needed a bunch of engineers trained in the "gaseous electronics" of the era of Langmuir and Tesla? Who does teach design of magnatrons and gyrotrons right now? Just what type of vacuum tube type equipment does he need? Why was Bussard stressing this?

Why is he calling it Magrid Transport? Can you describe this in more detail? Is he leaving out a bunch of details here to protect his work? I read something about Mu-metal being a magnetic shield material. Is Magrid Transport more than a simple magnetic shield? But I don't know anymore than this, can you expand on this?

The one thing Bussard seemed adamant on was that you couldn't make this smaller than a 2.5 meter cube. Why is that? Something nine foot on a side, seems like that puts it beyond the amatuer benchtop scientist. Is it? Has anyone on Fusor.net built ever super-conducting magnets?

"Realizing that the statistical significance of one count is +/- 100%, it still floored me." I don't undertand this.

I have talked to a Phd. in Fusion candidate at the University of Washington, and he said something about maxwellian distribution and the Todd Rider paper. Would it take millions to rebuild WB-6? Could someone like you or Richard Hull do it?

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #32 on: 01/29/2007 12:41 PM »
Three of the EMC2 lab people were hired by SpaceDev.   There is no money for salaries at the moment, but my understanding is that Dr. Krall is still interested, and Benson has expressed a strong interest.  I wouldn't want to give the impression that "the fix is in", in case anyone else is interested, but there does seem to be at least that much interest.

Gaseous electronics is alive, and has an annual conference.  I attended one a few years back.  That includes things like vacuum tubes, thyratrons, plasma displays, and gas discharge lighting.  A MaGrid style Polywell is essentially a vacuum tube diode with a magnetic field around the anode, and so would probably qualify as a magnetron.  The machine is an Elmore Tuck Watson machine (electron accelerator) with a magnetically insulated anode grid.  With high electron densities and energies, one property of the magnetic field is that it displays a trapping phenomenon called a Wiffle-Ball which increases electron densities inside the grid by a factor of some thousands.  Cusp losses from this trap (one of Rider's objections) are not really a problem as the MaGrid simply recirculates them.  The electrons only want to get to the anode.  Rider probably was only familiar with an earlier form of the machine called HEPS, which did not allow recirculation of corner cusp losses.  High electron lifetime at high kinetic energy is what makes the deep potential well that drives the ion trapping, and this must be efficient to make it work.  The loss rate of electrons across the field to the MaGrid needs to be low ... that's MaGrid Transport. WB-6 finally got the shape of the MaGrid right to greatly reduce those losses.

You can build a small machine, but the scaling says you need larger to make net power.  But higher fields in a small machine would go in the right direction.

One of Richard Hull's friends, Ed Sines, lives about 3 miles from me and knows how to make high temperature superconducting magnets.  If the group at fusor.net could pool their talents, I think they could at least build little machines, especially on the scale of WB-2 or WB-3.  For big net power machines, I doubt they could afford even the vacuum chamber without real funding.

An estimate of the standard deviation of a counted event is the square root of the count.  The square root of 1 is 1, so a count of 1 should be taken as 1 +/- 1 to a confidence interval of about 65%.  In other words, you need more counts to really call it a number.  But the timing of the count, as low as the background count on those counters is, suggests it really did respond to a burst of neutrons produced by a 5 kV drive voltage and probably about a 4 kV well depth, putting the ion kinetic energies no higher than 4 keV.  That's off the bottom of the charts for most D-D fusion crossection plots.  The reason anything could happen is that the machine naturally has a lot of head-on collisions due to the radial nature of the ion flow, and that turns out to be the equivalent of collisions at 4x the kinetic energy on those plots.

At one point in his paper, Rider seemed to make the assumption that the machine would maxwellianize because all plasmas maxwellianize.  That's how plasmas are usually taught.  But a properly designed IEC machine has a very non-maxwellian energy distribution, and ions reaching the center are nearly mono-energetic.  IEC machines are particle accelerators, not heat machines.  The only place where a properly-run machine maxwellianizes is close to the inner surface of the MaGrid, where the ions slow down and turn around for another pass.  At that point, the density is high and they actually do maxwellianize ... and in the process equalize out any kinetic energy imbalances they developed due to collisions at higher energies.  Rider raised the objection that the high energy non-fusion collisions would result in maxwellianization, and the machine itself responded by using maxwellianization to fix the problem!  

The whole key is finding a density low enough to allow decent mean free paths for the ions when transitioning most of the radius of the machine, but still high enough that fusion is likely in the high-density central focus region.  Done right, you find this sweet spot, which is not unlike finding the right fuel/air ratio to make an internal combustion engine run.






Offline mong'

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Re: Fusion with space related aspects thread
« Reply #33 on: 01/29/2007 09:19 PM »
going back to space related questions, what would be the typical specific power of, say, a multi-megawatt reactor ? are we talking Watts/kg ? KiloWatts/kg ?

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #34 on: 01/30/2007 12:51 AM »
Let's see if we can extract what you want from "Inertial-Electrostatic-Fusion Propulsion Spectrum:  Air-Breathing to Interstellar Flight,"  Bussard and Jameson, JPP v11 No 1, pps 365-372.  I'll limit this to the "QED" craft utilizing relativistic electron beam heating of reaction mass, aimed at Mars flight. Figure 7 compares thrust to mass at various power levels and Isp, for the whole engine system.  If you want the mass of the p-B11 reactor alone, I don't have that in this article, but judging by size, probably less than half the mass of the system.  For a couple of these, that would put it on the order of a megawatt per kg.  Hey, I'm just reading the graphs here.  This is a direct conversion reactor with very little waste heat.

With this system, one has a choice of how much reaction mass to use with a given amount of energy, thus a range of Isp is possible.  My experience is Dr. Bussard is fond of fast rockets, and may tend to run a bit rich on the reaction mass, so higher Isp may be practical.  For landers or lunar missions, he tends to go toward an Isp of 1500.  For longer distances, he shows as high as Isp = 5500.  He also has another class of diluted fusion product engines that hit far higher Isp (he shows 70,000 sec but I think half a million may be possible) at low thrust.  I'm not sure if the figures below are his CSR or ARC versions, which differ in the cooling mechanism and size of radiators.

Tagging the four corners of this envelope, with apologies in advance for the the columns probably not lining up, and for the fact I'm reading log-log graphs on a Monday:

Isp      Megawatts       Newtons      Total System Mass kg
1500     1000                1.2e5             2e3
1500     6000                7e5                1.6e4
5500     1000                3.2e4             1.8e3
5500     6000                2e5                1.3e4

Offline mong'

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Re: Fusion with space related aspects thread
« Reply #35 on: 01/30/2007 10:36 AM »
5500 sec. at 20 tons of thrust, that puts it above gas core nuclear thermal.
with that we can begin large scale settlement of mars, setup scientific bases on the outer planets, maybe a small colony on titan. those engines can use common propellants so sustained use should not be a problem

Offline TyMoore

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Re: Fusion with space related aspects thread
« Reply #36 on: 01/30/2007 12:35 PM »
It sounds good--let's build one!

Is there any idea what the neutron flux is going to be? I know that we are talking p-B11 fusion--so theoretically there are no neutrons--but it has been my observation that there is always some neutrons produced from side reactions, etc.

Also, a thrust to weight ratio of 1:1 seems incredible for a fusion device. This machine--if built--would make a very nice compact powerplant all by itself. Infact, if it is as small as the 'graphs' say it can be--and I'm a bit skeptical here--then such units ought to be capable of being used for municipal waste treatment by indirect electric arc or even direct plasma contact...

Hmmm.

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #37 on: 01/30/2007 02:09 PM »
That's what I say ... let's build one.  The naysayers have their math, Bussard, Krall, Jameson, and Wray have their math, and we can do math until we're blue in the face, and the only thing that proves anything is to build the bloody thing and try it.  Or so says the guy who can't do the math at the level of these guys.  Mike Faraday was my kind of lab rat.

I ran into a figure of merit for various nuclear fuels somewhere yesterday.  From memory, I think p-B11 was something like 50x better than D-He3 from the standpoint of neutron emissions (D-He3 has D-D side reactions, half of which make a neutron).

Skepticism in fusion claims is warranted and healthy, as long as it doesn't make us unwilling to try the thing that finally works.

Offline mong'

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Re: Fusion with space related aspects thread
« Reply #38 on: 01/30/2007 05:03 PM »
especially when you have an experiment that works, albeit a smaller one

EDIT: I just looked up VASIMR projected performance, it would seem that with the heavy 10 GWe reactor Dr. Bussard is proposing it could reach 5 tons of thrust at 30,000 sec. ISP using hydrogen(!)
that means settlements on the outer planets and definately a large colony on titan

Offline Tom Ligon

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Re: Fusion with space related aspects thread
« Reply #39 on: 01/30/2007 10:05 PM »
Oh, yes.  One of his papers specifically mentioned a rocket made for colonizing Titan.

But Mars is Bussard's first love.  He'd like a place "a little south of Syrtis Major."

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