Transterrestrial Musings

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The late MIT professor Lawrence Lidsky said much the same thing in a (in)famous article in MIT's Technology Review back in the 1980s.

Me, I suspect something like dipole fusion reactors burning (catalyzed) deuterium would have to be the way to go; conventional tokamaks are just too expensive and marginal.

Posted by Paul Dietz at March 10, 2006 09:28 AM

It's the classic straw-man problem of future tech, shared by nanotech, orbital beanstalks, fusion, etc. That being that since the technology itself is not developed yet nobody knows what shape it will be. Thus, the most common way of arguing against technological feasability is to assume some most likely technological model (e.g. tokomak fusion, kevlar fiber beanstalks, or somesuch) and then showing its deficiencies. In other words, setting up a straw-man and knocking it down. The alternative of spanning over a wide range of alternative technologies or disproving feasability from first-principles is almost impossible (and for good reason). In the end though this sort of exercise is no better than, say, proving that the bumble bee is incapable of flight. It proves little more other than our current level of ignorance.

Personally I think there is a lot of promise in fusion and I think we've been making substantial progress recently. However, I also think designs like ITER (organizationally and technologically) are unlikely to be the way forward. More likely the solution will be just a tad bit more sophisticated and less "ugly brute force/massive pile of money" oriented. A perfect parallel would be NASA and the Shuttle/ISS versus a more efficient method of manned spaceflight (simpler, smarter, more robust, vastly cheaper).

20 years ago the idea of fusion power was at best a pie-in-the-sky dream. Today fusion power is most likely technologically achievably and questionably economically feasible. There are people working out, in good detail with excellent science, how to make fusion power viable. Today fusion power is not "40 years away" as it was then. Rather, we are maybe 10-20 years away, depending on how much effort we put into it, from finding out how feasible fusion power might be. That represents a significant advancement and increase in maturity of the field, I believe.

Posted by Robin Goodfellow at March 10, 2006 10:48 AM

I agree with the others who have commented, it really speaks to the danger of One True Wayism in scientific development. If everyone adopts the One True Dead End, it tends to shut down alternative research, while yielding only scattered returns, and not much real progress.

While I'm not an expert in either field, I see the same thing happening with Minsky's view of AI and Drexler's view of nanotechnology.

Posted by Jon Acheson at March 10, 2006 11:49 AM

I'm for kinetic fusion by rail gun. The thrust to weight is not so good for local destinations. http://www.thespacereview.com/article/317/2
Excellent for a lunar power source. A 6km single gun shooting at a deuterated parrifin target might be the thing.

Or just set off bombs: http://www.thespacereview.com/article/299/1.

Posted by Sam Dinkin at March 10, 2006 12:08 PM

Researchers have been leaving the fusion field since the early 90's. I attended a conference on particle beam modification of thin films in Tennessee in '97 and found that many of the other attendees are ex-fusion researchers who have left the fusion field.

The cited several reasons: One, they believe the tokamak is a dead-end and that it is an bureaucratically driven program, much like NASA, and had no hope of working. They also believe that D-T fusion also is flawed because the intense neutron bombardment rapidly destroys the chamber walls in a fusion reactor.

Another problem is that a potential tokamak fusion reactor, if it worked, would be so large and expensive that it would not be economically practical. They went on and on.

The material science people also talked about a "physics culture" that was also detrimental to progress in the field.

They expressed the opinion that any fusion process that has potential would have to use an advanced, aneutronic fuel cycle such as Boron-hydrogen, and this can never be done in a Tokamak.

Later (on the same trip, I cam from Japan for this trip), we went to Los Alamos to meet with some researchers. We were trying to develop a new thin film deposition process for making diamond like carbon thin films and the people we were seeing were developing the same process, hense the purpose of our visit. It turns out that they process chamber that they were using for their research (the one we visited and saw) was left over from an alternative fusion experiment called the Spheromak. The spheromak work had lost its funding because it competed with the Tokamak and the tokamak people made sure that all competitive approaches were cut. The people I visited with were quite bitter about this and thought the spheromak was an approach more likely to lead to commercial fusion.

Google internet searches will bring up several other approaches such as dense plasma focus, IEC, magnetized target fusion, and the like. Also, there is Sandia's Z-machine, that may well be approaching break even.

I believe fusion is possible. I also believe that the tokamak approach has zero chance of success. Any of the massive government funded programs to develop fusion suffer from all of the same structural and organizational bureaucratic flaws as NASA. The government funded fusion programs are as useful for developing fusion as NASA is for developing commercial space industry.

Posted by Kurt at March 10, 2006 12:21 PM

I wonder if a fusion X-prize would help? Some suitably large amount of money for the first reactor that produces a certain amount of power for a certain amount of time?

Posted by Dave at March 10, 2006 12:51 PM

A prize for fusion would probably take a pretty big chunk of change. There would probably also be a lot of institutional opposition to it from the fusion community, which tends to be more interested in the physics than the practical application.

Kurt makes a very interesting point in noting the parallel between Big Government Fusion and Big Government Space.

Posted by Rand Simberg at March 10, 2006 01:32 PM

And where is Andrew Case when we need him?

Posted by Rand Simberg at March 10, 2006 01:33 PM

Andrew Case left Fusion research in favor of industry,

Posted by pat bahn at March 10, 2006 02:11 PM

Not that long ago. He still knows (and has opinions about) what's going on.

Posted by Rand Simberg at March 10, 2006 02:31 PM

If we can put a man on the moon ... Oh wait, we can't put a man on the moon anymore.

There was a time when we knew how to do things. I think we as a society, as a country, are becoming sclerotic with old age and fear of, well, pretty much everything. If the frontiers weren't all closed, it would be time for the young and ambitious to go elsewhere and start fresh.

Posted by lmg at March 10, 2006 02:52 PM

Not that long ago. He still knows (and has opinions about) what's going on.

And anyway, this particular critique (of Parkins') has been circulating since the late 1990s. There's even a rebuttal available on line.

The rebuttal would be a bit more convincing if one couldn't construct an isomorphic document from NASA 'rebutting' critiques of, say, ISS.

Posted by Paul Dietz at March 10, 2006 03:11 PM

I agree with Kurt's general sentiment on tokamak fusion, it won't be useful until the late 2040s, according to the timeline on ITER's site. The only thing you can do to get a conventional tokamak reactor to acieve ignition is to make it bigger, which is all they're doing with ITER (of course, this is not the case with Spherical Tokamaks--not to be confused with spheromaks, which, due to their lower aspect ratio, can achieve higher power densities than conventional tokamaks).

Spheromaks are a good alternative to tokamak fusion, but I'm not sure it was entirely an issue of competing with the tokamak as it was an issue of confinement. To date, spheromaks have always lost particles faster than tokamaks, though there is evidence that better confinement can be achieved by targeting specific causes of the losses.

Another alternative that I would like to mention is the Field-Reversed Configuration. Like the spheromak, it can achieve much higher power densities than tokamak, but also suffers from poor confinement. The FRC has stability issues as well. The reason why I mention the FRC is because it is perfect for fusion propulsion. It has a simpler magnetic field configuration than the spheromak, while offering similar advantages. It's also relatively easy to sustain in steady state unlike the spheromak, which would require a far more complex current drive system. It also has a natural divertor, which allows the high energy products of the fusion reaction to be used as a direct exhaust, and can achieve exhaust velocities of about 3 orders of magnitude higher than that of chemical propulsion with the D-3He reaction.

As for technical feasibility, the development of a p-B11 FRC reactor, according to GE technology officer Vincent Page, might only take 8 years with $75 million dollars, pocket change compared to the ~$10 billion needed for giant tokamaks like ITER.

Which, of course, brings up point that the private sector can do it better than the government. Still, while the government really isn't getting us anywhere in fusion research, the private sector isn't doing anything at all. This is not to say that I appove of government waste, but I don't think that market forces are currently strong enough to drive the development of a fusion reactor, either for generating electrical energy, or space propulsion. My point is that while fusion might be possible today, I don't think that we'll see it happen anytime soon. Still, as a physics student planning to get into fusion myself, I do hope I'm wrong, as I'd much rather work in the private sector than the government.

Posted by Justin at March 10, 2006 06:11 PM

I think a couple of years ago, I mentioned my idea (I am sure I am not the first) for a Fusion prize.

Posted by Mike Puckett at March 10, 2006 08:24 PM

I knew a bunch of plasma physicists in the 70s who told me that it was going to be a great field to work in because you wouldn't accomplish your goals until the year 2000, and therefore would have a long and uninterupted career. Fortunately, I didn't go into plasma physics, but instead invested my intellectual capital into Space.

No much difference in the end.

As to fusion, there should be a law, if you can't solve the problem in 20 years, put it on hold and wait for new and different technology to arise which could make it easier. I'd say that fusion is going to have to wait for room temperature superconductors or perhaps someone will solve the unified field theory and create artificial suns in the lab.

Posted by K at March 10, 2006 08:29 PM

Artificial suns? Doctor Octopus tried that. Did not work too well.

Posted by Mike Puckett at March 10, 2006 08:58 PM

Thanks to this paper I'm now less skeptical of fusion. Remember Clarke's first law: When a distinguished but elderly scientist states that something is possible,he is almost certainly right. Whenhe states that something is impossible, he is very probably wrong.

Posted by Lee Valentine at March 10, 2006 09:31 PM

You don't really need superconductors. Copper magnets would work fine for high-beta plasmas like Spherical Tokamaks, spheromaks, and Field Reversed Configurations. You'll only need superconductor magnets for giant tokamaks like ITER, because conventional tokamaks require stronger magnetic fields to contain a plasma of a given pressure. The issue is not so much with the technology itself, but with the understanding of the confinement properties of these alternatives, particularly with the spheromak and Field-Reversed Configuration, as they have high transport rates, or particle losses. The key is pinpointing the causes of the transport.

Posted by Justin at March 10, 2006 11:04 PM

Justin,

I am no sort of expert on the technicalities of fusion power.

But on the subject of fusion drives, I think we all ought to remember Larry Niven's Kzinti Lesson; that the better a reaction drive is the better it is as a weapon.

This will not get us into space. It's far too dangerous; what would the exhaust do to the ground underneath, never mind the eyesight of any onlookers? And what would people like the late unlamented pilots of the World Trade Centre aircraft do with such a craft?

The only, and partial, answer to this problem would be summary execution for anyone piloting a fusion drive craft in atmosphere.

And in any case, there is a much easier way to make a nuclear-driven spacecraft. Remember Project Orion?

Posted by Ian Campbell at March 11, 2006 04:52 AM

Ian: I don't think anyone is proposing using a controlled fusion rocket in the atmosphere. All the designs I've seen are for prolonged thrust at the milligee level in space.

Your concern about eyesight/etc. is weird. A continuous thrust rocket (assuming for the moment that this could or would be done using fusion) used in the atmosphere will almost certainly use considerable inert reaction mass, limiting the exhaust temperature. Beyond a certain point having high exhaust velocity just wastes energy.

Having made this spurious complaint, you then propose Orion rockets. Good grief. Orion is a really bad idea that appears interesting only because even the government was never stupid enough to try to build it.

Posted by Paul Dietz at March 11, 2006 05:16 AM

A direct exhaust fusion propulsion system wouldn't work in the atmosphere, at least not with any current technology I can think of. Any contact that the plasma makes with the atmosphere would cause it to cool to a point where fusion can't occur. In the atmosphere, fusion would only be useful as a thermal system, or in a system that requires large energy input, like an arc-heated scramjet or turbine.

Posted by Justin at March 11, 2006 08:19 AM

Paul,

Quite. I don't even know whether plus-gee fusion rockets are possible.

But I thought the whole idea of fusion rockets was to achieve very high exhaust velocity and thus high specific impulse; thus the use of large amounts of inert reaction mass would put us back very close to where we started.

Of course, that doesn't preclude the possibility of an air-breathing option for atmospheric flight, thus getting the vehicle into space where the supply of inert reaction mass can be closed off and the efficiency thereby greatly improved.

The whole issue of fusion rocket power is a total waste of time unless the exhaust velocity is higher than a chemical rocket, and therefore the exhaust temperature has to be higher, and therefore the exhaust will emit vast quantities of short-wave radiation such as UV and maybe even soft X-rays.

Orion would work. Nobody sane wants to use Orion technology for takeoff from ground, although it would probably work rather well in space where the radiation isn't much of an issue.

However, if the human race doesn't get into space and start using its resources, it may be the only way to avoid the total collapse of civilisation. In short, in twenty years or so it may be the only chance we have left.

Al Qaeda in charge of an Orion vehicle? If you want to give yourself nightmares, think about that one.

We need to get out there NOW. We could and should have had space colonies twenty years ago, and we need them!

Posted by Ian Campbell at March 11, 2006 08:19 AM

But I thought the whole idea of fusion rockets was to achieve very high exhaust velocity and thus high specific impulse; thus the use of large amounts of inert reaction mass would put us back very close to where we started.

Cost is generally minimized when the exhaust velocity is similar to the mission delta-V. If you have a variable Isp, the energy cost is generally minimized if you can have exhaust velocity similar to the delta-V so far. This is one reason it's good to use hydrocarbons instead of hydrogen as the fuel in the first stage of chemical launchers.

If you have very high Isp early in a mission, almost all the kinetic energy is left in the jet of reaction mass, not in the vehicle. This is wasteful.

The whole issue of fusion rocket power is a total waste of time unless the exhaust velocity is higher than a chemical rocket, and therefore the exhaust temperature has to be higher, and therefore the exhaust will emit vast quantities of short-wave radiation such as UV and maybe even soft X-rays.

No, rockets using nuclear energy can also trade temperature against molecular weight. The chamber temperature of 1000 sec. Isp thermal rocket using just hydrogen as the reaction mass can be considerably lower than the chamber temperature of a high performance chemical rocket.

Orion would work.

Orion was a Rube Goldberg scheme that would have been a nightmare to develop. If they had gone ahead with it the practical difficulties would likely have made it one of the outstanding aerospace boondoggles of all time.

However, if the human race doesn't get into space and start using its resources, it may be the only way to avoid the total collapse of civilisation.

Nonsense. There's ample resources down here to support civilization for millions of years. Just which resource did you have in mind that (1) we're about to run short of, (2) cannot be substituted for, and (3) is available in space?

Posted by Paul Dietz at March 11, 2006 08:35 AM

Just which resource did you have in mind that (1) we're about to run short of, (2) cannot be substituted for, and (3) is available in space?

Only one potential one that I know of--human freedom.

Posted by Rand Simberg at March 11, 2006 08:54 AM

That's why I mentioned arc-heated scramjets and turbines, which would require no onboard propellant. The biggest issue with arc heated systems would be in preventing erosion of the electrodes, and in the case of the scramjet, ionizing and heating the particles at hypersonic speeds.

On the other hand, in a vacuum environment like space, you can have direct-exhaust fusion which, as I've mentioned before, can have exhaust velocities of about 3 orders of magnitude higher than chemical propulsion, depending on the fuels used.

Posted by Justin at March 11, 2006 09:03 AM

As has been mentioned here before, scramjets are useful for maybe half a minute of boost phase. The rest of the time, they're dead weight.

Scramjets are for flying fast in the atmosphere, not for exiting it.

Posted by Big D at March 11, 2006 10:26 AM

Exiting the atmosphere is not the issue in reaching orbit, delta-V is. A arc-scramjet would be useful in a launch vehicle because it requires no onboard propellant, which makes up the bulk of the weight in chemical rockets. Of course, you still have the problem of getting it off the ground and into orbit, which would be the main issue in such a launch system.

Don't get me wrong, I'm not endorsing the idea of an arc scramjet. I mentioned the arc-scramjet because it was one of the few ways I could think of to apply fusion energy to a propulsion system that would work in the atmosphere.

Posted by Justin at March 11, 2006 11:30 AM

Sounds like there is plenty of interest in fusion power, somebody should set up a technically good blog on the issue. Any takers or are there already good bolgs on the subject?

Posted by A.Syme at March 11, 2006 08:38 PM

My blog is essentially a fusion blog, even though it has nominally been a space blog.

Posted by Justin at March 11, 2006 10:28 PM

You need to really this book...

http://www.amazon.com/exec/obidos/ASIN/0805059857/spaceviews/102-5165352-6872101

Before you make comments like these...

"Orion was a Rube Goldberg scheme that would have been a nightmare to develop."

"Nobody sane wants to use Orion technology for takeoff from ground, although it would probably work rather well in space where the radiation isn't much of an issue."

Orion is a tested technology. It works. Prototypes using conventional explosives have flown. The requirements for the pusher plate using atomic detonation have been tested. The only thing required technically to make it work is a self loading artillary piece (not exactly beyond our ability.)

Count me among the insane, because takeoff from ground is precisely why you want orion. Nothing matches it's ability to get infrastructure into space... not even close.

Last bugaboo, radiation. It's the concentration of radiation that kills, but that's true of anything. Concentrate enough water and I guaranty that'll kill you too. Low concentrations of radiation is a good thing (your body requires it for health.)

It's kneejerk ignorance and fear that keeps us from accomplishing a lot of tremendous fantastic goals.

Instead we make snails pace progress with water rockets.

Posted by ken anthony at March 12, 2006 08:56 PM

Orion is a tested technology. It works.

This is an outrageously and obviously false statement. Large areas of technology involved in Orion are not tested. No one has built pusher plates and tested them against repeated nuclear explosions. No one has built the nuclear device dispensing and control systems. No one has built the full-scale shock absorbers. No one has integrated it all and worked out the bugs that would show up when the systems are combined.

Getting all these to work, and to work reliably, would be very expensive. The system is more complex than ordinary chemical rockets, and look at how many of those (on a much smaller scale!) had to blow up before the technology reached its current state of development.

Posted by Paul Dietz at March 13, 2006 05:29 AM

Paul,

I assume you've read the book. You are right that a complete orion has never been tested. However, the essentials were. These were such known quantities that the scientist and engineers on the project had extremely high confidence. I happen to believe that the political problems were the only thing stopping them. The technical issues were well covered in 1950's terms.

These days we are of course too smart. If you asked todays graduate if we could get to the moon with vaccuum tubes they would of course give the correct answer that we can't. How sad.

The essential question that makes orion possible is what happens to a pusher plate in close proximity to a nuclear explosion. THAT QUESTION HAS BEEN ANSWERED. The rest, as they say, is left as an exercise to the student. Yes, the plumbing for chemical rockets gets complicated, but to presume that orion is more so is to deny the facts.

I guess the CAN'T DO attitude is alive and well.

Posted by ken anthony at March 14, 2006 11:14 PM

Let me add one more thing. If an asteroid was heading our way and the political consensus was that only Orion could handle the job of deflection this would be my prediction...

We'd have battleship sized spacecraft flying in less than 5 years. Of course, we might have to pay some private company to do it. Remember liberty ships? They were made of concrete. What a crazy idea.

Posted by ken anthony at March 14, 2006 11:25 PM

...or if you can stand the fish smell, stand at the base of the Brooklyn bridge. This is a thing made in the 19th century out of rocks. In case you need more inspiration.

Posted by ken anthony at March 14, 2006 11:44 PM

I assume you've read the book. You are right that a complete orion has never been tested. However, the essentials were.

Yes, I have that book. I can't imagine what book you think you were reading, since the one I have doesn't resemble your claim at all.

They never tested a pusher plate with a nuclear pulse unit. This is one of the essentials. They would have had to have gone further and tested fatigue of the plate as its material was subjected to the thousands of pulses it would have been subjected to over the launch, each creating an internal shock wave in the plate material (one of the particpants is quoted in the book as thinking spallation from these shocks would have been a showstopper.) Tests of subscale plates with chemical-explosive driven propellant pulses is not the same.

The system to disperse oil to protect the surface of the pusher plate from ablation was not tested, nor could it have been adequately tested short of flight experience (imagine the interaction of this oil spray with the hot, turbulent environment during a launch from the ground.)

The shock absorber systems weren't built on the scale required. The pulse unit delivery system -- this is the Rube Goldberg part I was talking about -- wasn't built or tested. Lots of pretty pictures, though.

The interactions of all these components wasn't tested at all, and these interactions were nontrivial.

Herbert York's comment on page 277 is relevant:

"Orion involved putting togeter simultaneously a number of novel technologies, most of which could not be meaningfully tested in isolation from each other or on a small scale."

Posted by Paul Dietz at March 15, 2006 03:24 AM

Paul, your criticism is valid. However, the essential fact that makes Orion possible at all is that a thin ablative coat can withstand the blast of a nuclear bomb in close proximity at all. This is extremely non-intuative.

You call it a Rube Goldberg contraction. My impression is that the fact that it uses nuclear bombs causes a disconnect. An external combustion engine is actually pretty simple. The key point in my mind is that the people actually working on the project knew they could do it. From a certain perspective a modern car engine could be viewed as much more of a Rube Goldberg.

Orion is dead with about nil probability of being resurrected. So this isn't an argument I'm ever likely to win. I do respect your opinion.

Your materials issue is certainly valid, but to call it a show-stopper? I don't think so.

Posted by ken anthony at March 16, 2006 09:02 PM

"could not be meaningfully tested in isolation from each other or on a small scale"

I think we also interpret this statement differently. The overall impression I got was that things became easier if you could scale them up and a lack of funding was the problem. Again, the compelling point in my mind is that the people actually working on it knew they'd take a battleship to Saturn by 1970 if only they had the funding. The people involved weren't delusional in my opinion. They not only had the can do attitude that is missing today, they had proved it on other projects (a big one as I recall.)

Posted by ken anthony at March 16, 2006 09:11 PM

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