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Figure1. Improving thermal efficiency of engines |
Document created: 27 August 04
Air University Review, November-December
1970
Lieutenant Colonel Rufus D. Hutcheson
As Secretary of Defense Melvin R. Laird told congressional committees in February and March 1970, one of the most serious threats to the United States is posed by the large and growing military research and development program of the Soviet Union. Of course, the specific impacts of this program on our future security are not known, but it is evident that the Soviet government is investing heavily to develop capabilities that threaten us, whatever its intentions may actually be. In fact, in recent years Soviet military technology efforts have been growing at a more rapid rate than ours. A dramatic reminder of this is being provided on a daily basis in Vietnam, where the technical superiority of our weapons so evident twenty years ago in Korea is now no longer apparent.
Reversing this unfavorable trend in selected areas of the relative U.S.—Soviet technological strengths is one objective of the Air Force technology program. With all basic research, exploratory development, and the non-systems-oriented advanced development incorporated in the program, it comprises our “technology base,” from which future systems and improved component technologies can be constructed. At Headquarters USAF the fiscal programming and overall resource management for this base are accomplished with assistance from specialists who have spent most of their professional lives in the technology program. The work of these staff members is paced by the realization that our technology base must expand in those areas critical to the relative capabilities available to the United States and her most likely enemies. Only by this means can we be assured that our future weapon systems will be of sufficient quality and timeliness to counter any threatening enemy innovations.
purposes of technology
Our technology base is expanded in two ways—or, more properly, in pursuit of two purposes. The first is to satisfy near-term needs for particular capabilities, either through engineering support to systems and subsystems or through advancing technology that improves the capability of a system already in operation or under development. For example, once the feasibility of the oxygen concentrator had been proved during exploratory development, the program progressed into engineering development under the Life Support System Program Office. The oxygen concentrator is a device that produces breatheable oxygen during flight and therefore eliminates the need for all the ground support equipment currently used to provide breatheable oxygen for crew and passengers. Additional development is currently under way to apply the oxygen concentrator to existing aircraft systems.
The second way of expanding our technology base is through efforts to achieve long-term incremental gains in fundamental technology areas which give promise of future utility. Thus, not intended to augment a potential system, this work is undertaken because experience has shown that advancements in these areas are likely to have application to future systems, as yet undefined. In actuality, however, one process supports the other; today’s long-term efforts make possible tomorrow’s short-term programs.
The turbine engine technology program is an example of this interaction. Many years ago one of the world’s outstanding scientists determined what was needed to improve the thermal efficiency of our heat engines. Three things were necessary: (1) to increase the pressure ratio; (2) increase the operative temperature of the cycle; and (3) improve the efficiency of the components. These elements are shown in Figure 1, where each cycle operating temperature line represents a series of engine designs with the assumed component efficiencies but at different cycle pressure ratios. The shape of the curves is a function of component efficiency, and the ideal line represents 100 percent component efficiency.
Figure1. Improving thermal efficiency of engines
In the 1950-55 time period the metallurgical temperature limit of the turbine was believed reached, and a plateau for efficiency improvement was acknowledged. This plateau existed, with only slight engine performance improvements, through 1965. In the meantime turbine technology effort continued in the area, among others, of heat transfer in turbine components. It had proceeded far enough by 1965 to support the decision to develop a new-technology C-5A engine with an air-cooled turbine. With acceptance of the cooled turbine, a completely new and very exciting exploitation of gas-turbine technology was made possible. Currently, we have identified and documented enough new high-payoff efforts needing demonstration to use up our projected resources for the next ten years.
Other areas of gas-turbine technology have also moved forward to the point where engine application is now possible. For example, Figure 2 shows a line drawing of two different engines. The top engine represents a paper design. The bottom one represents the TF39, which was developed for the C-5A. The TF39 engine had its component performance technology frozen in 1965 to allow for the development of an engine. In January 1970 we asked General Electric to paper-design a new engine for the C-5A aircraft. That is the engine drawn above the center line. In five years, fan technology has advanced so that we can now do the job in one stage instead of one and a half; we can have an 11-stage compressor instead of one of 16 stages; we can also use a shorter combustor, a one-stage high spool turbine instead of two, and a three-stage power turbine instead of six. If this advanced paper-designed turbofan engine were to be built and installed, with its improved specific fuel consumption and lighter weight, rough calculations indicate that the aircraft would weigh 100,000 pounds less at maximum gross weight than the current C-5A. This new, improved technology base is available for the short-term development of all gas-turbine propulsion systems and is being used in the F-15 and B-1 propulsion systems.
Figure 2. Advance gas-turbine technology is incorporated in the paper-design engine (shown above center line) to improve specific fuel consumption, among other things. If built and installed in the C-5A in place of the TF39 engine (shown below line), it is calculated to reduce the weight by 100,000 pounds.
source of the dilemma
While the current long-term efforts serve eventually to support future short-term programs, the existence of these two purposes for our technology program is the source of an inherent conflict. The competition between long-term and short-term interest for available resources intensifies the conflict. The problem is how to accommodate one adequately without damaging or mortgaging the other. It is not a new problem. Ten years ago the solution was to separate in-house laboratories into organizations of their own, in which the immediate pressures of systems support would not submerge the technology efforts for the future.
During the recent period of reduced defense spending on technology, the viability of this solution has been questioned. The Director of Defense Research and Engineering, Dr. John Foster, recently expressed “serious concern that the DOD in-house laboratory technical expertise is not being applied in full measure to the technical problems which are encountered during the development of new operational systems.” Assistant Secretary of the Air Force (Research and Development) Grant L. Hansen pointed out in response to Dr. Foster’s concern that there are still serious problems in transferring technology into operational systems and in bringing expertise to bear upon the problems of systems acquisition.
Therein lies the dilemma: To what extent should we direct our limited resources toward near-term systems work, realizing that in doing so we are detracting in some measure from technology that could have significant long-term impact? The choice hinges, among other things, on the time we are willing to invest before our operating forces receive a direct benefit from our technology program. The nature of this choice is sometimes difficult to determine. Frequently, for a new system, the Initial Operating Capability (IOC) date and the date when component design is frozen vary with national priorities and funds available; moreover, the date when new technologies will be available for systems use is largely dependent upon the effort expended. Thus, we often find that through greater effort on new and promising technologies we may be able to incorporate them into our newest systems.
current opportunities for system application
There are several areas of technology that currently offer significant opportunities for further exploration and application to systems engineering. One area that could pay off dramatically for future applications is laser technology. A decade ago, breakthroughs in lasers touched off intense effort directed towards finding applications for this newfound technology while simultaneously attempting to improve the efficiency, expand the choice of frequency spectrum by use of new materials, and increase the power of these devices. The entire world became aware of one laser application when the astronauts placed reflectors on the moon and scientists successfully received the reflected light and made accurate distance checks. Military uses of this new technology are, for the most part, highly classified, but it is evident that the technology will find its way into future weapon, communication, and reconnaissance systems as well as numerous support functions.
Technology already having application in system development is exemplified by composite materials using boron or graphite fibers. This may be the most significant materials development in recent years. Successful static and fatigue tests on the F-111 stabilizer, which uses this technology, indicate that full demonstration of advanced composites is possible in flightworthy hardware. The success of this pro-grant has led to the prediction that weight savings of 30 to 50 percent may be possible in some aircraft by 1980. It must be remembered, however, that several years ago a decision was made to press on with the composite program at the expense of a program in beryllium structures because composites appeared to provide more options to the system designer.
A technology needing an equally committing decision now is the fly-by-wire approach. Since the start of the air war over North Vietnam, considerable technical effort has been given to the problems of aircraft survivability. On 12 December 1967 the first successful test flight of a single-axis, fly-by-wire system was completed on a B-47 aircraft by the Air Force Flight Dynamics Laboratory (AFFDL). Fly-by-wire means the complete replacement of the mechanical linkages between the pilot’s stick and the control surface actuators by electrical signal wires. Its advantages are many: decrease in vulnerability and increase in flight control system reliability, design and installation savings, weight savings, volume savings, reduction in maintenance, and immunity to aircraft structural changes due to flexing, bending, and thermal expansion. Technically and operationally there seem to be no disadvantages. Reluctance to change appears to be the major obstacle to applying fly-by-wire technology in new systems.
constraints on technology development
There is little question that tomorrow’s Air Force will be built on technology being developed today, regardless of the purposes for which the technology effort was originated. However, while this has become recognized almost as a truism, it does matter considerably how that effort is designed and directed. In particular, as we carry out a useful and comprehensive program to build our technology base, we must be conscious of certain real and powerful constraints.
First, we need to keep in view the distinction between knowing “what to do” and determining “how to do.” In the example of the gas-turbine engine, even though we knew “what to do” to improve thermal efficiency, it took many years to learn “how to do” it in a manner amenable to the production of aircraft engines in quantity. In most technical areas which the Air Force has examined, the “what to do” is a well-established part of human knowledge, whereas the accessibility of “how to do” is largely a function of how intensely our resources are applied.
We also need to recognize that even new technology has limitations. Continuing with the turbine engine example, the gas-turbine cycle has real technical limitations. We are rapidly (perhaps within 10 years) approaching stoichiometric temperatures for hydrocarbon fuels, and if another cycle and fuel are not identified another technological plateau will be reached. Even though the need is 10 years away, we must be looking for the answer and conducting the necessary experiments to define the potential candidates. It should be remembered that it has taken almost twenty years to bring the air-cooled turbine technology from basic research through engineering development. It will not become old technology until we complete five to ten years of service operation and accumulate millions of hours of service.
When a technological barrier or plateau is reached, we need to be able to pursue effective alternatives, For example, since 1961 rocket-propulsion chemists have been attempting to add hydrogen to fuels and fluorine to the binder systems of solid propellants in order to continue the upward trend in specific impulse. They have met with only limited success in their attempts to characterize a new, widely usable, high-energy propellant. No major breakthroughs are on the horizon. Researchers are probing the frontiers of knowledge, expanding our technology base in the chemistry of rocket propellant propulsion, searching for something that would make possible more than incremental gains. But weapon systems cannot wait for possible breakthroughs, or even incremental advancements. For this reason, a second front has been opened to skirt the propellant specific-impulse problem and attack rocket hardware as a means of improving the systems. The point is that, when an area of technology appears to be up against a technological barrier or seems to be on a technological plateau where large resources will be needed to produce incremental gains, then coordinated technology programs are needed to probe the most likely avenues through the barrier, while supporting the development of alternate approaches to the solution of the problem. The “brute force” approach to systems development is defensible only when time has run out, when our technology base is inadequate, and when national survival may depend on the system operation.
Last, but not least, we need to deal effectively with reduced fiscal support. For the foreseeable future this will present a problem of major consequence and one which cannot be avoided. Although not all the problems harassing today’s Air Force technology program stem from recent funding trends, the management and execution of the program depend heavily upon the dollars available. The program has suffered from major funding reductions in recent years. These reductions become even more noticeable when the totals are corrected for inflation.
The research program has suffered proportionately the least reduction in recent years. It also seems to have considerable national support. For example, President Nixon’s task force on science policy has recommended “a near-doubling of the nation’s basic science research budget and new emphasis on defense research even at the expense of current military hardware development.” Even if scientific and technological competence must be financed at the expense of current weapons procurement, the panel felt that probable long-range gains would be worth the short-range risks. This kind of support for military research, combined with the growing interest in increasing the efforts of the National Institutes of Health and the National Science Foundation, should help to maintain a healthy foundation of scientific research on which technological exploration can be based.
By itself, however, scientific research does not assure us of the capability to react to technological advancements displayed by the enemy or to initiate technological advancements of our own. The exploratory development program is primarily responsible for these technological advancements.
It is interesting to examine what we have done with the approximately $230 million allocated during each of the last four years to exploratory development. This year about $100 million will be used for civilian personnel payroll, benefits, travel, and laboratory housekeeping. And $12 million will support laboratory efforts at Arnold Engineering Development Center, where laboratory products undergo environmental tests in wind tunnels and space chambers. The remaining funds, slightly over $100 million, are available for contract with industry, universities, and other organizations possessing R&D capability. Five years ago more than twice this amount was available for contracts. To accommodate this reduction, there has been a general elimination of funds for the more speculative, long-term endeavors which are not directly tied to a projected weapon system but which are necessary for the advancement of our technology base. In addition, the laboratories have nearly eliminated several areas of technology, such as hypersonic vehicle technology, ground and space support equipment, liquid rocket propulsion for air-launched missiles, space environment measurements, and many more.
Of the three technology program categories, advanced development programs have received the most severe reductions in recent years, and these reductions may hold a key to the dilemma of today’s technology program. There are two general classes of advanced development programs: technology-oriented and systems-oriented. The technology-oriented advanced development programs bridge the gap between component demonstration in exploratory development and concept formulation in systems-oriented advanced development programs. In many exploratory development efforts, such as the ramjets, air-cushion landing gear, aircrew escape and rescue, and controllable solid rocket motor, feasibility has already been demonstrated. Furthermore, it appears that system developers are aware of the performance potential that has been offered.
resolving the dilemma
One may reasonably question why advances in technology already demonstrated have not been used in system development programs. As usual, there is no simple answer, and the solutions provided by managers of technology programs would probably differ considerably from those developed by systems acquisition managers. The answer may sometimes lie in the fact that, although some part of a system has been demonstrated, the entire system may not have been adequately demonstrated. In other instances, demonstrated capabilities may not be used because of more nebulous questions, such as those pertaining to roles and missions, disarmament, or international political developments.
One related factor affects all programs—it might be called an economic deterrent to innovation. System program directors, who have the primary responsibility for new systems acquisition in the Air Force, are under growing pressure to perform on time and within their allocated funds. Hence, cost growths resulting from improved capabilities, increased development time, or program expansion are studiously avoided, and system program directors are constrained not to incorporate anything new unless it is absolutely necessary, and then only if the new technology has been amply demonstrated in a near-operational environment.
This economic deterrent to innovation would not, under normal circumstances, be a major deterrent to the incorporation of the latest technology. An aggressive, well-funded, technology-oriented advanced development program would bridge the gap between technology and new weapon system development. For example, the Advanced Turbine Engine Gas Generator (ATEGG) program has demonstrated, in a true propulsion systems environment, the advanced turbine engine components already described. It has thereby permitted the use of this advanced technology for the F-14, F-15, and B-1 development programs. Unfortunately, equivalent programs have not been established in other technical areas, and usually system program directors are faced with the dilemma of developing their systems by using components and subsystems that are either well demonstrated but obsolescent or undemonstrated but innovative.
It is evident that the technology dilemma is aggravated significantly by reductions in the research, development, test, and evaluation (RDT&E) budget. What, one may well ask, is resource management doing to cope with this situation? Briefly, we are reducing our in-house operating overhead, concentrating our efforts, and applying available contract resources to the areas of maximum payoff—trying to make every nickel in the technology program count. We are engaged in a variety of management efforts to get the most from the technology dollar.
The relevancy of research to future systems has been strengthened by the recent reorganization which brought the Office of Aerospace Research (OAR) under Air Force Systems Command. In the past, the OAR laboratories have maintained close liaison with the AFSC product divisions and system program offices (SPO’s) by (1) a reporting procedure for describing the planned research program, the research objectives, résumés of research under way, and outstanding results; (2) formal coupling meetings, in which AFSC divisions make their needs known to the laboratories; and (3) developing Research Planning Objectives by mission area, based upon Air Force tasks and functions. In the future, close coupling at the headquarters level will increase the liaison between research laboratories and SPO’S.
Of course, this liaison is not without danger to the viability of the research program. Whereas in the past, through its autonomy, OAR has been able to pursue programs based on an objective analysis of the technology involved, the increased headquarters coupling of labs and systems could tend to submerge the research program and turn it into a system support program. Although this would tend to bolster near-term systems acquisition, it could be detrimental to the advancement of technology useful in systems twenty years from now. We will attempt, therefore, to guard against such an excessive swing of the pendulum.
In the exploratory development area, we have initiated Project REFLEX, facilitating expenditure of resources in those areas considered by the laboratory directors to have the greatest payoff. This project resulted from Deputy Secretary of Defense David Packard’s 30 December 1969 request for a demonstration whereby selected DOD laboratories would test the concept of using only fiscal controls instead of the combined fiscal and manpower controls now used to manage their operations. Our intent is to augment the continuing effort to get more technology for the dollar.
To date efforts to bolster the lagging non-systems-oriented advanced development have been marginal. Air Force Systems Command has developed and published the Director of Laboratories (DOL) Plan, which identifies exploratory and advanced development efforts required to meet projected Air Force needs through 1985. In this plan the technical need for several as yet unfunded advanced development programs was identified. Each spring a Joint USAF/AFSC evaluation group reviews and ranks all advanced development programs to make certain that only the most critical are funded, but the new starts that remain unfunded comprise an impressive group. Individual laboratory efforts to keep technology moving ahead include conducting an in-house demonstration of advanced ramjet technology, joint efforts with the Navy to demonstrate thrust vector control for air-launched missiles, and negotiations with the Canadians to provide a C-8 aircraft for demonstration of the air-cushion landing gear. There remains available an important opportunity for management innovations to smooth the transition of new programs from exploratory development into advanced development on a coordinated, technology-wide basis.
An ideal means has not yet been found, but is being sought, to resolve the conflict between near-term needs and long-term goals. Action now under consideration involves relocating certain functional engineers (e.g., avionics, propulsion, structural) who are not directly involved in systems integration and assigning them to the appropriate laboratories. The association of engineers engaged in system support with engineers engaged in exploratory and advanced development would do much to bridge the gap between technology and new operational systems.
As we approach a period in our history marked by reorienting national priorities, decreasing dollars for defense, and rebuilding national confidence in the military R&D community, we must constantly search for the equitable balance between resources for solution of near-term problems and fulfillment of long-term goals. For each system development we must determine whether national goals will be better served by selecting well-established technology that must be extended to its limit to achieve adequate system performance or by encouraging new technology that can be applied more conservatively for equivalent performance. We must also find a way to bridge the gap between technology and future weapon systems so that future programs will show increased responsiveness to the needs of the operating forces.
Hq United States Air Force
Lieutenant Colonel Rufus D. Hutcheson (USMA; M.S., AFIT) is a development engineer, Science and Technology Division, Directorate of Development and Acquisition, DCS/R&D, Hq USAF. His other assignments have been in operational flying, technology, and graduate study (astronautical engineering, University of Michigan, 1963-65). He has served with the Electronic Systems Division and Headquarters of Air Force Systems Command and had a tour flying RF-4Cs in Vietnam.
Disclaimer
The conclusions and opinions expressed in this
document are those of the author cultivated in the freedom of expression,
academic environment of Air University. They do not reflect the official
position of the U.S. Government, Department of Defense, the United States Air
Force or the Air University.
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