X-Message-Number: 21049 Date: Tue, 04 Feb 2003 00:27:14 +0100 From: Henri Kluytmans <> Subject: Cost of MNT objects Thomas Donaldson wrote : >I was not, at least directly, claiming that biological systems >would be more efficient. But you seemed to suggest it. :) >Your message said that biological systems provided a proof >of principle for the existence of nanotechnological >systems. I pointed out one way in which they were quite clearly >different from nanotechnological systems, Yes, you are right about that. I said : "There seems to be no theoretical barrier, even better, biological systems seem to be a proof of concept (like birds where for flying machines)." I was meaning to say here, that biological systems are a proof of the two fundamental things which the MNT concept and biology have in common, and which are : "molecular building blocks" and "self-reproduction" Indeed, biological systems cannot be used as proof that the MNT concept as a whole is possible. When I made this statement I was only having in mind these two central issues of MNT and biology. ( This was because Yvan was questioning the possibilty of "self assembly" of more than 20 components. ) The two main differences between the way biology works and the way MNT should work are : 1) That biology uses molecular building blocks that are weakly bonded (e.g. Van der Waals interaction) to each other (e.g. proteins) while the MNT concept want to use very strong (covalent) bonds between its building blocks (mostly diamondoid). 2) That biology uses transport of molecules mostly based on Brownian movement while the MNT concept will use mechanically controlled systems. The first will result in MNT producing stronger objects than biology, the latter will result in MNT producing atomically precise objects. Similarly, regarding the birds example, they are only a proof that flying objects heavier than air are physically possible, and not, of course, that a yet-engine or propeller driven flight is possible. ================ >I raised the question of >whether or not living systems might tell us that the kind of >nanotechnological devices you envisioned just wouldn't be >so easily made that they could compete. I raised a question, >but did not directly answer it. And I tried to make clear that current research into MNT designs (or as Robert Freitas calls it "Exploratory Design") seems to indicate that they will compete, and by a very large margin indeed. >I WILL point out that in real life at least one factor which >you don't mention in your message becomes quite important: the >energy cost of making a device in the first place. Sure, the >device when made may use far less energy than a living cell, >be packed more tightly, etc etc. But how much will it cost to >make? Hmm, this is a fairly straight forward calculation. I will try to do it here for two examples : the MNT computing device with a processing power equal to the human brain, and the artificial red blood cells (i.e. respirocytes). The energy released when following materials are burned : 1 KG of lipids = 38 megajoule 1 KG of proteins = 17 megajoule 1 KG of glucose = 16 megajoule 1 KG of diamond = 33 megajoule 1 KG of methane = 50 megajoule 1 KG of gasoline = 44 megajoule 1) MNT computing device of 10^16 cps (calculations/second) Merkle made following estimate in "Molecular Repair of the Brain" : "Given that there are 100 grams of protein and 175 grams of lipid in the brain, this means there is almost 2,000 kilocalories of chemical energy stored in the structure of the brain, or about 8 x 10^6 joules" Regarding the MNT computing device based on nano-rod-logic : A 10^16 cps device, uses 1 watt , size 10^-11 m^3 (cube with 0.22 mm sides) which would contain a chemical energy of about 1 joule when made of solid diamond. (Of course, the actual device will contain much less total chemical energy in its bonds because it's not a solid block of diamond. I guess even more than 2 or 3 times less chemical energy.) A less conservative human brain processing power estimate would result in a 10^13 cps device, that uses 1 microwatt , and has a size of 10^-14 m3 (cube with 0.022 mm sides), and it would contain less than 0.001 joule of chemical energy !!! (These estimates are based on chapter 12 in Nanosystems) I did not include the cooling part of the device, but on the other hand, I took the chemical energy for a volume-equivalent mass of diamond, which should make more than good for the omission of the cooling part. Also the energy cost for transportation of molecules, inefficiencies, computation and entropy reduction together are almost ten times less than the chemical energy. 2) Artificial red blood cells (or respirocytes) From the article about respirocytes by Freitas : - the operational lifespan of respirocyte is about 20 years. - 1% per day of all red cells are destroyed naturally - baseline respirocytes can deliver 236 times more oxygen to the tissues per unit volume than natural red cells - density of red cells = 1100 kg/m3 - a 1-micron respirocyte has a density of 679 kg/m3 with tanks empty Assuming a human lifespan of a 100 years : Every 100 days, all red blood cells must be replaced. Thus for a 100 years that's 365 times total replacement for red blood cells. For the respirocytes only 5 times total replacement is required in 100 years. For 1 milliliter of blood the chemical energy is = ~30 Kilojoule (assuming a 50%/50% proteines/lipids proportion for red cells) For 1 milliliter of respirocytes chemical energy is = ~22 Kilojoule For a 100 years, the chemical energy for producing red bloodcells or an equivalent mass of respirocytes compare as 2*10^4 :: 1 === CONCLUSION : The energy cost of making a device, and also the operational energy usage of device made using MNT should be several orders of magnitude better than for biological systems. If these examples are typical, then it seems that biological systems are not very efficient in ANY WAY . === I didn't even take into account that : 1) Of course, as I said before, MNT systems could be designed that would be based on building blocks with lower bond energies and Brownian movement transportsystems. Such systems should use less energy for building atomicely precise objects than biological systems do. 2) Furthermore it's to be questioned if the energy consumption for creation of objects is a valid general reference for efficiency or economic cost. Energy will be much cheaper in the future when solar power collectors can be manufactured much cheaper and better than now. One should also consider the fact that an enormous amount of energy is being wasted in our solar system. More than 99.999999% of the energy the sun is producing is radiated into space without being used at all. 3) Also, as Drexler notes in Nanosystems, when organic feedstock molecules are used as raw material (in stead of CO2) then a reasonably efficient molecular manufacturing process will be net energy producer!! >to make more nanosystems. The construction process you propose >(not that I think you are alone) COULD turn out to be expensive >enough that it just isn't practical when compared with how >living things are made. Regarding the "economic price" of MNT produced objects, they should be VERY CHEAP indeed, compared to the price of currently manufactered products. Current products vary between 10-10000 $/Kg (tv,cars,furniture,airplane,etc..) Drexler estimated a price for MNT produced objects of : 0.1 $/Kg but here he assumed obtaining raw materials from agricultural resources. ==== The basic price of a product is determined by the cost of energy, raw materials and development of the design blueprints. Because the cost of design can be neglected when large series of a product are made, the price will be determined primarily by the cost of energy and raw materials. (And there will probably be a lot of designs that will be available as open-source, like there are for computer software now.) The raw materials are mostly molecules containing C atoms (and some H and/or O). On Earth, at this moment, the easiest source to obtain these raw materials is the atmosphere (CO2 and H2O). These resources are for free. Energy can be obtained from solar power collectors, that in turn can be produced using MNT. Raw material and energy cost for creating the solar power collectors themselves can be neglected in the long term. The cost of surface area seems to be the principal remaining cost! Merkle made a crude estimate in "Molecular Repair of the Brain" : "The land cost $100 [for 1 year], so the cost per joule is 0.9 nanocents and the cost per kilowatt hour is 3.3 millicents. Solar power, once we can make the solar cells cheaply enough, will be over several thousand times cheaper than electric power is today." Making 1 KG of diamond out of CO2 would require about 33 MegaJoule, so the energy cost would only be about 0.03 cents! (Hmm, looks like the price Drexler estimated is very conservative.) Furthermore, even cheaper would be, creating floating solar panels in international waters (or in space), this should eliminate the cost of surface area. >(Not that if this were so, we could >not use similar reactions to those of living things to make >our nanodevices!). Indeed. But for the moment, it still looks like MNT systems based on covalent C-C bonds and mechanical transport systems producing atomicely precise objects seem feasible. And also that the products made using this technology will not be expensive at all. >Basically I was pointing out one issue which some proposals >for making nanodevices don't consider. Hmm, I seem to recall many articles/books where production and energy costs were considered (by Drexler and Merkle). >In any case, if YOUR proposed systems are too costly compared >to the kinds of nanodevices based on chemistry and biochemistry, >then no one will buy them. From the examples available it looks like it will be the opposite : objects manufactured using MNT should be dirt cheap! (Even compared to products based on biochemistry.) >If they are put out to compete with >living things, living things will win, not by being more >efficient or superior, but simply by numbers alone, When considering self-reproducing systems, starting numbers are not relevant, in the long term reproduction efficiency is the only thing that counts. >while your nanodevices struggle to reproduce themselves only >a few times. Ehh ... why will they struggle to reproduce only a few times ? Cheers >Hkl Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=21049