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SOME CONTRIBUTIONS TO ENERGETICS BY THE LEWIS

RESEARCH CENTER AND A REVIEW OF THEIR

POTENTIAL NON-AEROSPACE APPLICATIONS

by Robert W. Graham and Martin U. GutsteinLewis Research CenterCleveland, Ohio

TECHNICAL PAPER proposed for presentation atthe Conference on the Impact of Aerospace Technologyon Society in the 70's sponsored by the AmericanSociety of Mechanical EngineersAnaheim, California, September 10-13, 1972

SOME CONTRIBUTIONS TO ENERGETICS BY THE LEWIS RESEARCH CENTER

AND A REVIEW OF THEIR POTENTIAL NON-AEROSPACE APPLICATIONS

By Robert W. Graham and Martin U. Gutetein

NASA Lewis Research CenterCleveland, Ohio

ABSTRACT

The primary technology areas of the LewisResearch Center are aerospace propulsion, power andmaterials. As examples in these technologies, theauthors review the Center's programs in the fieldsof cryogenics and liquid metals. Potential non"aerospace application for the results of theseprograms are discussed. These include such possi-bilities as: hydrogen as a non-polluting industrialfuel; more efficient central power stations andpowerplants for advanced ground transportation.

INTRODUCTION

This paper reviews some of the aerospaceresearch and development at the Lewis ResearchCenter which can be classified under the generalheading of "Energetics." Most of the R 6 0 done atLewis could be placed in this category because theCenter has the NASA responsibility for propulsion,energy conversion, and materials.

The propulsion research involves airbreathingengines, chemical rockets, electric thrusters, andnuclear rockets. The effort in energy conversionIncludes batteries, fuel cells, thermionic con-verters, photovoltaic cells, magnetohydrodynamics,and Ranklne and Brayton cycle systems. The materialsprogram includes applications for high temperature, forcryogenic use and such exotic materials as metal-polymer matrix composites. We have chosen to focuson two topics; namely, cryogenics and liquid metalswith which we have been personally involved. First,we will present a review of the work that has beendone or is in progress in these areas as part ofNASA's aerospace effort. This w i l l be done by high-lighting some of the programs and citing a part ofthe significant technical 1iterature which detailthe work in these programs. Then, in response tothe theme of this session, we w i l l comment on theapplicability of this work to several non-aerospaceproblem areas.

CONTRIBUTIONS TO CRYOGENICS

In the late 40's and aarly JO's the LewisResearch Center was involved in a research programto select optimum high energy fuels and oxidizerssuitable for jet propulsion applications. Fromknown theoretical thermochemical performance, liquidhydrogen ranked high on the list of fuels. Once arare laboratory curiosity, liquid hydrogen becameavailable in sufficient quantities for fuel researchlargely as a result of the U.S. intensive thermo-

nuclear research and development of the ''tO's. TheNational Bureau of Standards, the Atomic EnergyCommission, the Department of Defense, and manyprivate contractors including universities, hadcontributed to highly developed techniques for pro-ducing, handling and storing liquid hydrogen.

Fuel Research

The turbojet work with liquid hydrogen was doneas a flight research program in a B~57 aircraftwhich was specially fitted and modified for the pro-gram. Figure 1 is a photograph of the aircraft.It was concluded from this study (I) that it isfeasible to fuel an operational aircraft with hydro-gen.

Studies of hydrogen for chemical rockets beganeven before the turbojet program. This effortproved to be significant and timely. It was one ofthe earliest programs to evaluate the problems andpotentials of hydrogen-fueled rockets. Hydrogenproved to be unusually well behaved as a liquid fuel.It burned stably and efficiently over broad limitsof fuel/oxidant ratios (2,3). There were some un-usual and difficult problems with the oxidizers usedin conjunction with hydrogan. Liquid oxygen was acryogen that required special handling in scrupulouslyclean hardware. Fluorine was nastier yet in termsof its compatibility with flow systems and storagevessels. Elaborate procedures had to be followed tocondition the flow system against complete oxidationby the fluorine. The "pickling" process was tediousand didn't always insure that the oxidizer wouldstay contained in the system as intended.

In any case, hydrogen with either of theseoxidizers was, and s t i l l is, the most energeticliquid chemical propellant combination known. Thetechnology advanced sufficiently during the I950'sto make hydrogen one of the fuels selected for spacemissions in the I960's.

A decision was made in 1961 to utilize hydrogenas a fuel in the upper stages of the Apollo vehiclefor the moon-landing mission. The pioneering rocketstudies with hydrogen years before NASA came intobeing proved to be influential in reaching thisdecision.

Measurement and PumpingInterest in hydrogen as a propellant was the

motivation for some research relating to the handlingand usage of the fuel in propulsion systems. Includedin this research was a separate program on instru-mentation. For example, the Lewis Research Center

has been active in the application of carbon andplatinum resistor temperature gages (4). Also inconjunction with the early rocket thrust stands,the use of turbine-type flow meters for hydrogenservice was developed (5)-- More recently, a newmethod for determining the density of liquid andtwo phase hydrogen has been devised (6).

Pumping of hydrogen was another research area:In the pumping of liquids, one of the primary con~cerns is encountering cavitation on the impellervanes. Cavitation generally leads to severe loss ofperformance and even to physical damage of the pump.It was learned that in the case of liquid hydrogen,there was considerably more operational margin beforecavitation effects on performance were noted. TheLewis Research Center developed practical designcriteria to allow hydrogen pump designers to incor-porate this added cavitation margin into theirdesigns (?)•

fluid PropertiesPhysical and transport property data for hydro-

gen were very scanty when these programs withhydrogen were initiated during the 1950's. Con-sequently, it was necessary to acquire a morecomprehensive set of property data. Through acontract, the National Bureau of Standards wasengaged in an extensive program of property acquisi-tion and correlation (8). The Bureau of Standardsalso continued to make valuable contributions tothe measurement and handling techniques for liquidhydrogen.

Heat Transfer ~Another research program with hydrogen was an

investigation of the heat transfer and flow charac-teristics of the fluid. Figure 2 is a phase diagramof the fluid on the temperature entropy plane. Theregion (region I I I ) underneath the saturation linedome represents the two-phase state. To the left ofthe dome is a compressed liquid region (region ll);to the right is a gaseous or vapor region (region la);just above the apex of the dome is the near-criticalstate region IV; and further above that, the fluidbehaves like a gas (region I).

The objective of the program was to investigatethe heat transfer characteristics of hydrogen overthe entire domain of fluid states. In a propulsionsystem, several of these fluid states are encountered.The program began with a study of the two-phase domainand continued into the near-critical and then high-pressure gas regions. The apparatus consisted of anelectrically heated tubular test section and a tankwhich pressure-fed the hydrogen through the testsection. Many channels of instrumentation wereemployed in measuring the heat transfer rates, thefluid and wall temperatures, the flow rates andpressures of the fluid.

In the two-phase region (region I I I , fig. 2),a film boiling situation was encountered which wasunique when compared to experiences with other fluids.A correlation for the local heat transfer and pressuredrop was developed (9). Besides the convectiveboiling, the pool boiling of liquid hydrogen wasstudied. The experiments encompassed nucleate andfilm boiling processes and such factors as bodyforces (gravity) and geometry were parameters of theprogram (10). It was observed that hydrogen will

begin to boil on surfaces when subjected to tem-perature differences less than one degree Fahrenheit.

Following the two phase studies in the heated-tube apparatus, hydrogen in its near-critical statewas examined. It was discovered that the heattransfer of near critical hydrogen resembled thatof the two phase region and that conventional forcedconvection correlations were greatly in error (II).

The liquid hydrogen programs pursued at Lewisduring the 1950's and I960's contributed informationwhich was utilized by NASA and its contractors inthe design and successful operation of liquid hydro'gen engines. Hydrogen w i l l continue to hold animportant place In future space flight missions.

Current Research

In the cryogenic area, two of the programsnow underway at the Lewis Research Center w i l l bediscussed. The first is an attempt to systematizethe available fluid properties of the cryogens sothat one consistent, authoritative source of infor-mation is available throughout NASA. The LewisResearch Center is conducting this program in con-junction with the National Bureau of Standards.Fluid properties (including transport properties)are now available in useful computer codes that areadaptable to a variety of applications (12, 13).

The second program is directed at investigatingthe choked flow characteristics of cryogens. Follow-ing the Apollo 13 accident in which liquid oxygenleaked out of a rupture in one of the main supplytanks, the question of estimating discharge ratesfor such a fluid was raised. Preliminary compu-tational methods are compared with experimentalchoked flow rates for a two-phase cryogen (1 ».).Current research is directed at a general analyticalmethod for estimating choked flows of cryogens.

CONTRIBUTIONS TO LIQUID METAL TECHNOLOGY

Since I960 the Lewis Research Center has hadprimary NASA responsibility for development ofelectric power systems for use in space. Througha coordinated in-house and contractoral effortboth dynamic and static (direct) energy conversionsystems were studied. The operating temperaturesof some of these space systems are well above thoseof terrestrial central power stations. Hence, the"exotic" liquid metals (mercury, potassium, sodium,lithium, etc.) were selected as the working fluidsand coolants. These selections were based on theliquid metals' relatively low vapor pressures, highthermal conductivities and chemical stability.Results achieved in the development of the liquidmetals technology w i l l be illustrated by brieflydescribing the status of the potassium Rankinespace electric power system. The potassiumtechnology is discussed further in references 15and 16

Materials Compatibility

Tantalum and niobium-based refractory alloyswere selected as containment materials for the hightemperature portions of the potassium systembecause of their high strength and ductility andease of fabrication and joining (17, 18, 19, 20).They are, however, susceptible to oxidation in airat elevated temperatures. Therefore, thesematerials must be protected by enclosure in vacuumchambers capable of operating at pressure levelsof about 10 ° torr.

The long-term compatibility of the candidatealloys exposed to the alkali liquid metals wasdetermined in two corrosion test loops built undercontract by Nuclear Systems Programs, GeneralElectric Company (21-25). Each of these loops wascomprised of a reactor coolant and a potassiumboiIing-and-condensing circuit, see figure 3. Anelectric heater of 10 KW capacity substituted forthe reactor heat source, and a simulator ratherthan a turbine, was installed at the boiler exit.Analyses conducted after these tests demonstratedno generalized corrosion of either the Nb-IZr orT-lll materials in contact with the high temperature(about 1360 K) liquid metals, attesting to theexcellent compatibility of these refractory alloys.

Nuclear Heat Source

Efforts to develop the technology for alithium-cooled, compact, fast spectrum nuclearreactor of the type required for the potassiumRankine system have recently begun as an in-houseproject at Lewis. Ceramic uranium mononitride hasbeen selected as the fuel due to its high thermalconductivity, melting point and uranium content.The candidate cladding material is T-lll. A ref-erence design of this reactor calls for a 2 MWtoutput for 50,000 hours at an outlet temperature of1220 K (26). Efforts are underway in materials com-patibility, irradiation effects, bearings and seals,reactor physics and reactor control. Reference 27presents a detailed discussion of the materials'programs for this reactor. A brief discussion ofthe irradiation program is as follows.

Miniature fuel elements clad with T-lll, Nb-|Zr,W-25 Re-30 Ho and stainless steel will be irradiatedat selected temperatures in the range 830 to 1370° C.The burnup rate for these experiments will be accel-erated 5 to 10 times that of the reference design.Selection of clad material and temperature levelw i l l place the fuel in a relatively restrained, apartially restrained or an unrestrained condition.The measured diametral swelling w i l l be comparedwith predictions made by analytical models. Asecond series of accelerated burnup rate tests w i l lbe conducted with thinner-clad, full or near fullsize fuel pins to more directly confirm the fuelelement design. Other irradiations in reactors w i l lexplore fuel swelling effects with pins containingU02 and porous UN fuel and using T-lll and Nb'lZras clad materials. Finally, fast neutron irradia-tions of a series of unfueled clad and structuralmaterials, including tantalum, molybdenum andtungsten based alloys, w i l l be conducted at elevatedtemperatures. Previous exposure of materials tofast'spectrum neutrons have demonstrated the genera-tion and growth of voids. The voids result inswelling and embrittlement, a major obstacle to theachievement of a long-life fuel element. Thematerials irradiation tests to be conducted w i l lyield information on changes in mechanical proper-ties, density, chemistry and microstructure.

Turbine

In potassium as well as steam Rankine turbines,condensation or the formation of liquid drops,usually occurs during the vapor expansion process.The constant impact of these droplets, particularlyon the rotating members of the latter stages of theturbine, could result in material removal, loss ofperformance and eventual failure. To assess thesignificance of moisture erosion on turbine life,two potassium turbines were built and tested at aninlet temperature level of about 1500° F (1100 K),

a level typical of the temperature of the vaporflowing in the latter stages of the space systemturbine (28, 29, 30). The first turbine was operatedfor 5000 hours at a moisture level of 3 percententering (8 percent leaving) the last of two rotatingstages. Subsequently, a three-stage potassiumturbine (shown in fig. 4) was tested for an identicalperiod of time with a moisture level of about7 percent entering the third stage (13 percentleaving).

The erosion damage to the blades of the first turbinewas found to be negligible. Examination of theblades of the last stage of the 3~stage turbineindicated the microscopic beginnings of erosionpitting at blade tips. This result, when extrapolated,suggested the need for condensate removal devices,such as those employed in conventional steam power-plants. Consequently, the three-stage potassiumturbine was reassembled incorporating rotor andstator moisture removal devices. In addition, avortex condensate separator was installed at theturbine exit. This latter device was representativeof a separator which might be installed in the ductingbetween the two spools of a space system turbine.The effectiveness of these devices with potassiumvapor at about 1500° F (1100 K) was found comparableto moisture separation units employed in conventionalsteam turbines (31).

Boiler

The initial efforts to develop the technologyfor the boiler were directed at obtaining potassiumboiling heat transfer and pressure loss data inonce'through single tubes at temperatures up to1750° F (1230 K) (32), and up to 2100° F (1420 K)(33). The tests were conducted with inserts insidethe tubes which caused the boiling potassium to swirl.Analysis of the data indicated the presence of threedistinct two-phase heat transfer regimes in a potas-sium boiler: a nucleate boiling regime in which thetube wall is believed fully wetted; a transitionboiling regime in which the wall is only partiallywetted; and a superheat region where the tube wallis essentially dry but the vapor may contain tinydroplets. The swirl inserts were found to extendthe nucleate boiling regime to higher vapor quali-ties than possible in a plain tube, thereby reducingthe length of the transition region. In addition,the helical flow induced by the inserts enhanced theheat transfer in both the transition and superheatregions. These benefits permitted very compactboiler design, an important requirement for space.

Based on the results just described, a full-scale, multiple-tube potassium boiler was designed(34) . One tube of this boiler was fabricated ofT'lll and tested over a range of temperatures between1700° F (1200 K) and 2100° F (1420 K), exit superheatsas high as 300° F (167° C) and power inputs between60 and 185 kWt (90 kWt design) (35). Lithium, flowingcountercurrent to the potassium in an external annularjacket, served as the heating fluid. The boiler wasfound to be extremely stable even during transientoperations simulating startup. Preliminary analysisof the data indicates that the procedure employed IDdesign potassium boilers with swirl-flow inserts isvery accurate (36, 37).

Other Components

Lewis has also sponsored efforts to develop thetechnology for the other components of liquid metalsystems. Several potassium condensers were testedsuccessfully (38, 39). An electromagnetic boilerfeed pump cooled by NaK at 800° F (700 K) was tested .

for 10.000 hours without degradation (40). Isolationand throttle valves of t-inch nominal size have beenbuilt and tested in flowing lithium for 5000 hours(3500 hours at a temperature of 1900° F (1300 K) (41).Finally, an electrically-actuated throttle valve ofli-inch nominal size was operated for 5000 hourswhile frequently exposed to potassium vapor at 2IOO°F(1420 K) (37). A photograph of this valve Is shownin figure 5.

APPLICATIONS

In the previous section, we have reviewed someof the research and development work in cryogenicsand liquid metals that has been done, or is inprogress, at the Lewis Research Center. As has beenindicated, all of this work is directed towardaerospace propulsion and power applications. Nextwe w i l l suggest some non-aerospace areas where theresults of this work could be useful. \

tCryogenic Use in Electrical Equipment

A promising area for the application of cryo"genie technology is in the production and trans-mission of electricity. The electrical resistivityof pure metals such as aluminum and copper isdramatically reduced at cryogenic temperatures. Forinstance at liquid hydrogen temperatures, theresistivity is approximately 1/500 that of the roomtemperature resistance. Cryogenic resistive trans-mission cables are being considered for largecapacity (200 MW) transmission (42).

Design proposals have been made to buildelectrical generators and transformers withcryogenical lycooled conductors. According toreference 43, hydrogen cooled aluminum conductorsappear to have attractive design characteristics.

Superconducting magnets are being built whichemploy niobium-tin, niobium-zirconium, or niobium-titanium alloys as the winding material. Theseconductors are cooled to liquid helium temperatures(4.2 K). At this extremely low temperature, theseconductors exhibit practically zero electrical resis-tance. Superconducting magnets have been manufacturedwith field strengths as great as 15 Teslas (44).

They are being used in nuclear accelerators andbubble chambers and in research facilities formagnetohydrodynamic and thermonuclear (fusion)studies. It appears that they will have importantapplication to the electric-power generation systemof the future. Also, they are being considered asa possible means of levitating vehicles for surfacetravel.

Hydrogen as a Fuel

Because of the high depletion rate of ourfossil reserves, some studies (45) suggest thathydrogen could be used as a fuel'and also as a basicraw chemical for domestic and industrial use Inplace of oil and natural gas.

As part of a study of turbine engines for high-speed trains and buses for the Department of Trans-portation, the Lewis Research Center is examiningthe use of hydrogen as a fuel. Hydrogen is parti-cularly attractive for domestic vehicles becauseof its clean combustion products. Significantamounts of hydrogen could be made available from theelectrolysis of water. The electrical power toperform the electrolysis could come from largenuclear-fission powerplants. Some are even lookingfurther ahead to the advent of fusion-electricpower and are suggesting that nuclear parks wouldbe constructed along the coastal waters where bothelectrical power and hydrogen would be produced asbasic energy commodities (46). Engineering-economic studies show that transmission of energyover long distances (^ 350 mi.) can be done moreeconomically by means of fluids in pipe lines ratherthan by high-voltage electric transmission lines (45).The existing pipe line system for natural gas couldprobably be adapted to the transport of hydrogen.Such a proposal poses a number of serious technicalproblems. One of the most serious is the safetyproblem. Hydrogen in air has extremely broadexplosive limits (18.3% to 59%) and is prone to leak.In these regards it is more difficult to deal withthan natural gas, and the safety procedures wouldhave to be more strict, safety~wise. Also, becauseof hydrogen's low density, flow control equipment,pipe and valve sizes and burner designs would haveto be modified. The broad experience with this fuelin the space program should aid in expediting use ofhydrogen for domestic purposes. How rapidly and howextensively hydrogen utilization w i l l evolve is notclear at this time.

Non~aerospace Applications of the LiquidMetal Technology

The l i q u i d metals and potassium Rankine tech-nology developed for space w i l l likely find broadterrestrial use. In central station power genera-tion, a lower temperature version of the potassiumRankine system has been proposed as a topping orbinary cycle for conventional fossil-fueled steampowerplants (47). Interest in a similar alkali metalbinary cycle has been expressed by the Department ofInterior (48). The potassium topping cycle whencombined with a steam cycle results in an increasein conversion efficiency from the 40 percent levelof modern combustion steam powerplants to 50 percentor more. Consumption of fuel, stack emissions andwaste heat release are all substantially reducedper unit of electrical power produced by such aplant. A potassium-steam binary cycle has also beenproposed as the conversion system for fusion power(49). Depending on potassium turbine inlet tempera-ture, such a powerplant could produce electricity

with an efficiency exceeding 55 percent.When fusion power is realized, mankind will

have an energy source which relies on a virtuallyunlimited source of fuel. The fusion reaction con"sidered most likely to be demonstrated first is thedeuterium-tritium (O'T) reaction. A powerplantutilizing the 0"T reaction w i l l require lithium,either in the form of a liquid metal or molten salt,as a coolant and as a material for breeding tritium.To contain the lithium, niobium-and tantalum-basedrefractory alloys have been suggested. The practi-cality of such a fusion system w i 1 1 depend consider-ably on the availability of fully-developed, fully-proven refractory materials and lithium technologies.Results of several Lewis studies are relevant tothese technologies. For example, the long-termcompatibility of these refractory alloys with high-temperature flowing lithium was demonstrated. Otherstudies include: the determination of long-termcreep and thermal stability of refractory alloys;the preparation of specifications for obtainingrefractory alloys qualified for lithium service;the fabrication of large-diameter refractory alloypipe; the development of high-purity welding andjoining techniques; the establishment of lithiumhandling and purification procedures; and the fabri-cation and operation of components for high-temperature lithium service, such as heat exchangers,pumps, valves, electric heaters and instrumentation.Some research related to evaluating the feasibilityof fusion for propulsion may also be applied to groundfusion powerplant systems (50).

Another space technology which w i l l have impacton the civilian sector is that of'once-throughboilers. The Environmental Protection Agency ispursuing the development of closed steam" andorganic-Rankine cycle engines for automobilesbecause of their potential for reduced emissions.These engines must satisfy stringent requirementson acceleration and other performance transientsand must fit into a compartment not much differentfrom that occupied by the internal combustion enginein today's cars. Most of the boilers for these autoengines are of the once-through type and several areadaptations of aerospace boiler designs. One majoradvantage of the once-through boiler over therecirculating type, for example, is its small workingfluid inventory. Rapid engine startups and quickresponses to operator demands are made possible bythe small inventory. Moreover, in the event of atube failure, the once-through boiler would dischargea smaller quantity of high temperature working fluid,an important safety feature. The compactness affordedby once-through boilers is, of course, another ad-vantage of interest to the developers of these engines.Reference 51 illustrates the application of potassiumonce-through boiler design procedures developed underthe space program to steam boilers for automobileengines.

The swirl-flow inserts developed for use in thepotassium boiler may find application in the steamgenerators of liquid metal fast breeder reactor(LMFBR) powerplants. Reference 52 describes thedesign, fabrication and test.ing of a 1.5 MWt-capacity module of a sodium-heated steam evaporatorproposed for this nuclear powerplant. The evaporatorcontains helical inserts to swirl the boiling flow.According to this reference, swirling the flow delaysthe onset of the departure from nucleate boiling(DNB) to higher qualities. Hence, thermal cyclingof the tube wall separating the sodium and steamfluids will be held to a minimum by these inserts

5

resulting in greater reliability and longer lifefor the heat exchanger. Additional applicationsof the once-through boiler technology to non-aerospace uses should become evident in coming years.

The swelling of fuel clad and structuralmaterials of the LMFBR is the subject of major effortby the Atomic Energy Commission. Excessive swellingwould require premature fuel element removal, thusincreasing the cost of electricity generated by thepowerplant. Studies are being made of advancedLMFBR's using nitride, carbide and metallic fuelsin place of the present uranium oxide. Also, alloyscontaining molybdenum, vanadium and niobium arebeing considered for cladding in place of stainlesssteels. Lewis' materials irradiation program forthe space power reactor will obtain swelling datafor some of these materials and fuels. This infor-mation should be very useful to breeder reactordesigners.

In 0"T fusion systems, very energetic neutronsat high flux levels will be formed and will interactwith the plasma-containing walls. Neutrons of thespectrum and flux level believed typical of thefusion reactor cannot be generated either by reactorsor ion accelerators. Consequently, engineering dataon mechanical properties of materials irradiatedunder fusion reactor conditions may not becomeavailable prior to the construction of a fusionpowerplant. The design of the containment wall andthe selection of the material for this wall maywell have to be predicated on a basic understandingof the swelling and damage mechanisms. Lewis'irradiation program, which is oriented towardobtaining a more fundamental understanding of thesephenomena, represents another technology area ofpotential importance to the non-aerospace powergeneration field.

CONCLUDING REMARKS

This paper has presented a brief review of thetwo aerospace technologies being pursued at theLewis Research Center. These two are directly rele-vant to the nation's capabilities to developadvanced terrestrial energy conversion systems, bothstationary and mobile. They are providing means toimprove the performance or service life of componentsfor these systems and offer new ways of storing andtransmitting energy. These technologies and theirapplications illustrate the relevance of aerospacetechnologies to other national needs.

REFERENCES

1 Lewis Laboratory Staff, "Hydrogen for Turbo-jet and Ramjet Powered Flight," NACA RM E57023,Apr. 26, 1957.

2 Auble, C. M., "Study of Injection Processesfor Liquid Oxygen and Gaseous Hydrogen in a 200 PoundThrust Rocket Engine," NACA TM D 56-125, Jan. 1957-

3 Heidmann, M., "Combustion Performance withVarious Hydrogen and Oxygen Injection Methods in a200 Pound Thrust Rocket Engine," NACA RM E 58 E2t.

4 Sinclair, D. H., Terbeek. H. G., and Ma lone,J. H., "Cryogenic Temperature Measurement," NASATM X-52825.

5 Minkin, H. L. and Hobart, H. F., "Liquid-Hydrogen-Flowmeter Calibration Facility; PreliminaryCalibrations on Some Head-Type and Turbine-TypeFlowmeters," NASA TN D'577 (1961).

6 Wenger, N. C. and Smetana, J., "HydrogenDensity Measurements Using an Open-Ended Microwave

Cavity," I.E.E.E. Transactions on Instrumentation andMeasurement, Vol. IM-21, No. 2, May 1972-

7 "Pump Technology" Proceed ings of the Conferenceon Selected Technology for the Petroleum Industrv.Part VI, NASA SP-5053, December 1965.

8 Goodwin, R. D., Oili e r , 0. W., Roder, H. M.,and Weber, L. A., "Pressure-Density TemperatureRelations of Fluid Parahydrogen From 15 to 100 K atPressures to 350 Atmospheres," Journal of Researchof the National Bureau of Standards, Sec. A. Phys.and Chera., Vol. 67, No. 2. Mar-Apr. 1963,pp. 173-192.

9 Hendricks, R. C., Graham, R. W., Hsu, Y. Y.,and Friedman, R., "Experimental Heat Transfer andPressure Drop of Liquid Hydrogen Flowing Through aHeated Tube." NASA TN D-7&5, 1961.

10 Graham, R. W., Hendricks, R. C., andEnters, R. C., "Analytical and Experimental Studyof Pool Heating of Liquid Hydrogen Over a Range ofAccelerations," NASA TN D-1883, 1965.

11 Hendricks, R. C., Graham, R. W., Hsu, Y. Y. ,and Friedman, R., "Experimental Heat Transfer Resultsfor Cryogenic Hydrogen Flowing in Tubes at Subcriticaland Supercritical Pressures to 800 Pounds per SquareInch Absolute," NASA TN D-3095, Mar. 1966.

12 Hendricks, R. C., Baron, A., Peller, I.,and Pew, K. J., "GASP—A Computer Code for Calcula-ting the Properties of Eight Fluids," NASA TM X-67895.

13 Gordon, S. and McBride, B. J., "ComputerProgram for Calculation of Complex Chemical Equi-librium Compositions, Rocket Performance Incidentand Reflected Shocks and Chapman"Jouguet Detona-tions." NASA SP-273, 1971.

14 Simoneau, R. J., Henry, R. E., Hendricks,R. C., and Watterson, R., "Two-Phase Critical Dis-charge of High Pressure Liquid Nitrogen," NASATM X-67863.

15 Peterson, J., Heller, J. A., and Gutstein,M., "Status of Advanced Rankine Power ConversionTechnology," Presented at the American NuclearSociety Meeting, Boston, Mass., June I3"17, 1971.

16 Manson, S. V., "A Review of the Alkali MetalRankine Technology Program," Presented at the 1968IECE Conference,. Boulder, Col., Aug. 13-17, 1968.

17 Heller, J. A., Moss, T. A., and Barna, E. J.,"Study of a 300-Kilowatt Rankine'Cycle AdvancedNuclear-Electric Space Power System," NASA TM X-1919,Nov. 1969.

18 Rosenblum. L., Fnglund, D., Hall, R., Moss, T.,and Scheuermann, C., "Potassium Rankine SystemMaterials Technology," NASA SP-131, Aug. 1966.

19 Proceedings of Conference on Recent Advancesin Refractory Alloys for Space Power Systems, LewisResearch Center, NASA SP-245, June 26, 1969.

20 Moorhead, P. and Stone, P., "Survey of Prop-erties of T'lll (Tantalum-8 Tungsten-2 Hafrium),"NASA TN 0-5873, June. 1970.

21 Hoffman, E. and Holowach, J., "Cb-IZr RankineSystem Corrosion Test Loop," General Electric Co.,GE-246, May 1968.

22 Harrison, R., "Advanced Refractory AlloyCorrosion Loop Program," Quarterly Progress ReportNo. 19. NASA CR-72662. Feb. 1970.

23 Harrison, R. and Smith, J., "Advanced Re-fractory Corrosion Loop Program," Quarterly ProgressReport No. 20, NASA CR'72739, May 1970.

24 Harrison. R. and Smi'th, J., "Advanced Re-fractory Alloy Corrosion Loop Program," QuarterlyProgress Report No. 21, NASA CR-72782, Aug. 1970.

25 Harrison, R. and Smith, J., "Advanced Re-fractory Corrosion Loop Program," Quarterly ProgressReport No. 22, NASA CR-72818, Nov. 1970.

26 Krasner, M., Oavison, H., and Olaguila, A.."Conceptual Design of a Compact Fast Reactor forSpace Power," NASA TM X-&7859, Presented at theAmerican Nuclear Society Meeting, Boston, Mass..June 13-17, 1971.

27 Gluyas, R. and Lietzke, A., "MaterialsTechnology Programs for a Compact Fast Reactorfor Space Power," NASA TM X-&7869, Presented at theAmerican Nuclear Society Meeting, Boston, Mass..June 13-17. 1971.

28 Zimmerman, W. and Rossbach, R., "Metallur-gical and Fluid Dynamic Results of a 2000-HourEndurance Test on a Two-Stage 200-Horsepower Turbinein Wet Potassium Vapor," ASME Paper 67"GT-9.Presented at the Gas Turbine Conference, Houston,Texas, March 5~9, 1967.

29 Schnetzer, E., "Two-Stage Potassium TurbineThree-Thousand-Hour Test," NASA CR'72273, July 1967-

30 Schnetzer, E. and Kaplan, G., "ErosionTesting of a Three-Stage Potassium Turbine," ASMEPaper 70-Au/SP T"37, Presented at the Space Tech-nology and Heat Transfer Conference, Los Angeles,Calif. , June 21-24, 1970.

31 Rossbach, R. J. and Kaplan, G., "PotassiumTesting of Condensate Removal Devices for RankineSpace Power Turbines," Presented at 197' IECEConference, Aug. 197'•

32 Peterson, J. R., "High-Performance 'Once-Through' Boiling of Potassium in Single Tubes atSaturation Temperatures of 1500 to 1750° F,"NASA CR-842, Aug. 1967.

33 Bond, J. and Converse, G., "Vaporizationof High-Temperature Potassium in Forced Convectionat Saturation Temperatures of 1800 to 2100° F,"NASA CR-843, July 19&7.

3^* Peterson, J. , Weltmann,' R. , and Gutstein,M., "Thermal Design Procedures for Space RankineCycle System Boilers," Presented at the IECEConference, Boulder, Col..Aug. I3"l6, 1968.

35 Bond, J. A., "The Design of Components foran Advanced Rankine Cycle Test Facility," Presentedat the IECE Conference, Las Vegas, Nevada,Sept. 21-25, 1970.

36 Gutstein, M. and Bond, J. A., "PreliminaryResults of Testing a Single-Tube Boiler for theAdvanced Rankine System," NASA TM X~52996,March 1971.

37 Bond, J. A. and Gutstein, M., "Componentand Overall Performance of an Advanced RankineCycle Test Rig." Presented at the IECE Conference,Boston, Mass., Aug. 3~5, 1971.

38 Sawochka, S., "Thermal and Hydraulic Per-formance of Potassium During Condensation InsideSingle Tubes," NASA CR-851, Aug. 1967.

39 Fenn, 0., Acker, L., and Coe, H., "Steady-State Performance of a Seven-Tube NaK'Cooled Potas-sium Condenser," NASA TN D-4020, June 1967.

40 Powell, A. and Couch, J., "Boiler Feed EMPump for a Rankine Cycle Space Power System,"Presented at IECE Conference, Las Vegas, Nevada.Sept. 21-25. 1970.

41 Harrison, R. and Holowach, J., "RefractoryMetal Valves for 1900° F Service in Alkali MetalSystems," GE SP~508, Apr. 1970.

42 Fox, G. R. and Bernstein, J. T., "Under-ground Cryogenic Cable Systems," Mech. Eno.. Aug.1970, pp. 7-12.

43 Burnier, P. and de La Harpe, A., "Applica-tions of Liquid Hydrogen in Electrical Engineering,"Pure and Applied Cryogenics. Vol. 5, Pergaraon Press,1966.

44 Laurence, J. C.. "Superconductive Magnets,"NASA TM X-52752.

45 Gregory, 0. P., Ng, D. Y. C. , and Long.G. M., "Hydrogen Economy", The Electrochemistry ofCleaner Environments." Plenum Press, 1972,

46 Weinberg, A.. "The Energy Crisis, A Look atShort and Long-run Solutions," New Engineer.

Feb. 1972.47 Fraas, H. , "Preliminary Assessment of a

PotasstunTSteam-Gas Vapor Cyc\e for Better FuelEconomy and Reduced Thermal Pollution," ORNL'NSF-EP-6, Aug. 1971.

48 Testimony of Hollis H. Dole, AssistantSecretaryHineral Resources, U. S. Dept. of Interiorto Senate Committee on Interior and Insular Affairs,Feb. 8, 1972.

49 Fraas, A,, "Conceptual Design of a FusionPower Plant to Meet the Total Energy Requirements ofan Urban Complex," Proceedings of Conference onNuclear Fusion Reactors, Culham, England, Sept. 17"19, 1969.

50 Roth, J. R., Rayle, W. 0., and Reiranann,J. J., "Technological Problems Anticipated in theApplication of Fusion Reactors to Space Propulsionand Power Generation," NASA TM X-2106, Oct. 1970.

51 Peterson, J., "The Effect of Swirl FlowUpon the Performance of Monotube Steam Generators,"Presented at 1970 SAE Automotive EngineeringCongress and Exposition, Detroit, Mich., Jan. 12"16, 1970.

52 Stevens, W., Daman, E., Zebroski, E., andTippets, F., "Steam Generator Development for aProposed 350 MWe Liquid Metal Fast Breeder ReactorDemonstration Plant." ASME Paper 7l"WA/NE-6, 1971.

00If)

fcl

Figure 1. - NACA B-57 hydrogen-fueled aircraft.

100

90

80

Sa.

70

60

1 50

40

30

20

Ratio of pressureto critical pressure,

P/Pr

£j£2i &ff T" locus

10 20 30 40Inlet bulk entropy, J/(g)(K)

50

Figure 2. - Heat-transfer regions as function of inlet con-ditions. Region I, gas or fluid; region la, gas (lowtemperature); region II, liquid (fluid); region III, twophase; region IV, near critical.

TURBINESIMULATOR

ruu-iN-ruse

POTASSIUM

PftEHEATER

HOWMETE * ._.

PRESSURETRANSDUCER

SfRESSED

PRESSURETRANSDUCERSLACKDIAPHRAGM

TURSIMtSIMU1ATOR

VACUUM

TANK

CONDENSERSU8COOUR

H LITHIUM

m POTASSIUM• ARGON

. ILKTRICAt POWER

m rtcxrsuDRIVE CAME

CORROSION LOOP 1 [T-lll]

Figure 3. - Schematic of refactory materials compatability test apparatus.

Figure 4. - Three stage potassium turbine after 5000 hours operation.

COin

t°"Noi

Figure 5. - Throttle valve for use with potassium.

NASA-Lewis-Com'l