I&EC REPORTS AND COMMENTS Identifying materials science
A novel pump for corrosive materials Rockets from waste
MATERIALS SCIENCE Amid the constantly changing names for technical disciplines, one of the most baffling is materials science. Because the boundaries and the internal composition of any discipline are constantly in flux, it is not unreasonable to expect that, like professionalism, materials science would be difficult to identify. This assumes, of course, that materials science is a bona fide discipline in the same sense that chemistry and physics are disciplines. After lengthy inquiry, it seems that there is an organizational problem involved in the identification of materials science that has not been accounted for. Disciplines such as chemistry and physics are primary. They may be combined in many ways to form secondary disciplines, such as engineering and the medical arts. The secondary disciplines may be further combined with the primary disciplines and with each other to form tertiary disciplines, ad nauseam. T h e trouble is that each successive level of combination introduces complexity. By the time we get to tertiary disciplines the identity of whatever it is we seek is so nebulous that it literally defies classification and becomes little more than an exercise in induction. The alternative is to proceed with an operational definition. This, of course, is merely an obtuse way of suggesting that we forget the whole thing and accept whatever we find in front of us. Still, it would be nice to know what is meant by materials science. The materials in materials science obviously don’t include gases or liquids, except in an incidental way. This suggests that materials science is just another name for solid state
physics. However, largely by gravity, solid state physics has come to be identified with electronic materialsi.e., semiconductors, superconductors, nonconductors, and the like. It now begins to dawn that the materials in materials science also include refractory materials, ceramic materials, metals, carbons, polymers, reinforced plastics, and all other types of solid composites. Materials science, therefore, is nothing more or less than a convenient collection of technical disciplines (hardly a science) which regulates and hopefully makes useful regularities in the classes of solids enumerated above. This is certainly desirable, but it is a mystery why such a simple idea should be hidden behind all that mumbo-jumbo. Perhaps the grant dispensing agencies are more touchable by a materials scientist than a solids technologist or a metallurgist. We may be witnessing a classic example of titleship. In addition to the collaboration implied between various groups under the banner of materials science, a positive advantage is the better regulation of effort. This alone makes all the trouble worthwhile. But why not call a spade a spade and not an instrument for agricultural excavation. v
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RECIPROCATING JET PUMP A novel type of jet pump, for hot or corrosive fluids, was demonstrated at the recent Physics Exhibition in London by The General Electric Co., Ltd. The pump contains no moving parts and operates on a novel principle which is adaptable to a number of design configurations. The pump extracts fluid from a stream during an exhaust stroke and reinjects the same fluid into the stream during a subsequent intake stroke. The net thrust of the fluid in the stream results from the difference in flow patterns around the intake and exhaust jets (see sketch). During the exhaust stroke, the fluid removed through the exhaust jet has little momentum in contrast to the relatively high momentum at the intake jet. The necessary cycling action is achieved by varying the pressure above an auxiliary tank of fluid connected to the jets. The net efficiency of the pump is low-only about 20%-but the method is nevertheless attractive in those cases where absence of moving parts is more important than efficiency. This pump also avoids the dilution of the main fluid which occurs when a second fluid is used as a source, as is the case with conventional jet pumps.
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I&EC R E P O R T S DROP COALESCENCE The perpetually popular subject of drop coalescence has been investigated with variable success. Less popular but probably more useful are critical looks at the productivity of research programs, not in terms of financial return but in terms of useful results. G. B. Lawson [Chem. Process Eng. 48 ( 5 ) , 45 (1967)] has surveyed the complex field of research on drop coalescence and, not surprisingly, has concluded that there are gaps which require filling. This is particularly true of the “many drop s ystem .’’ The capacity of all forms of liquid extraction equipment is limited by the behavior of droplets. I n rotating disk contactors, for example, the droplets produced at the disks must retain their identity as they move through the equipment or a reduction of surface area of the droplets will decrease the mass transfer rates. However, at the interface, in the end of a typical column, rapid coalescence is desirable to minimize residence time. Similar problems exist in spray columns, pulse columns, mixer-settler units, etc. The inherent complexity of the problem has led to two simplified approaches in evaluating drop coalescence research. In the first, the technique is to focus attention on the behavior of single drops at a twofluid interface; in the second, a more pragmatic and descriptive study of the operational performance of types of equipment. In the simplest terms, the first approach may be called the mechanistic approach and the second the empirical approach. The mechanistic approach yields many numbers and great masses of mathematical expressions representing models. I t doesn’t seem to have yielded too much bona fide information. The empirical approach yields many data representing the performance of equipment. Because of the subtle, and usually unknown, differences between pilots and 12
actual operational units, it is virtually impossible to transpose information froin one unit to another. This is the traditional penalty of empiricism. In summary, problems of coalescence are just about those of any other technical discipline-viz., there is a lot of research into the mechanisms with little coordination and even less useful result. The empiricists provide the most immediately useful information but it has little long term utility-at least with respect to providing designers and operators with performance criteria of yet to be built units. I t seems we have seen this all somewhere before.
ROCKETS FROM WASTE Like most other areas of the space business, propellant formulation and manufacture are reacting strongly to the cost consciousness of the Congress. I n speculating about the future development of rocket motors for the 62nd National Meeting of the A.I.Ch.E., J. C. Barr, of Lockheed Propulsion Co., noted that there are now no manufacturing facilities in the United States for the continuous production of solid propellants. Some plants employ semicontinuous or batch/continuous-cast methods but none have, apparently, even any plans for a truly continuous facility for packaged rocket motors. One of the more intriguing items in Barr’s discussion was the utilization of waste as a rocket fuel. By combining paper, human waste, food waste, powdered metal, and an oxidizer, it is possible to produce an auxiliary fuel. I t doesn’t provide high performance but it does get rid of the waste in a useful manner and adds to the overall weight/propulsion ratio of a motor. Two reactions to these ideas are incredulity at the state of the art of propellant production and wonder at the entremes that are apparently necessary in seeking efficiency of rocket performance. If it is possible to manufacture propellants with the
I N D U S T R t A L A N D ENGINEERING C H E M I S T R Y
same general approach one would apply to any other chemical product, then a liberal dose of chemical engineering seems in order for the rocket business. The economics of rocket production are now more strict than ever before, probably because of Congressional scrutiny and because the novelty of the business has worn off. O n the other hand, the nature of the product seems to make it desirable to produce in more isolated surroundings than one would expect in a paint factory. On the other hand, conventional economics don’t appear applicable to the rocket business. Except for the fact that we all have to pay the bill, the only legitimate criterion for success is the approach to the limiting efficiency. This is truly a business of extremes where engineering is master.
CORRECTION The captions for the figures of the article beginning on page 106 of the May issue for 1967 (Vol. 59) should read as as follows: Figure 2. Fadeometer studies Figure 3. Comparison of esterification time with acid numbers for various formulations Figure 4. Comparison of burning rates of bromine-and chlorine-containing resins Figure 6. T h e effect of phosphorus on burning rate Figure 7. T h e effect of antimony oxide on the flammability of tetrabromophthalate resins Figure 8. Tunnel test results Figure 9. A S T M D-635-63 Figure 10. ASTAMD-757 apparatus Figure 11. A S T M D-757 burning rate us. Br content Figure 12. HLT-15 apparatus Figure 13. Method 2023.2 (LP-406b) test apparatus Figure 14. ASTM E-162-62T
In addition the top curve in Figure 2, page 106 should be labeled B and the lower curve should be labeled A .
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