i t_ "'//v

NASA Technic_a| Memoranduffi- I062_J1 ...... AIAA-93-2278 ......

Space TransportationAlternatjves for Large Space Programs: The International Space University SummerSession- !992

Bryan A. Palaszewski Lewis Res_earch Center._ Cleveland, Ohio

Prepared for the 29th Joint Propulsion Conference and Exhibit cosponsored by the AIAA, SAE, ASME, and ASEE Monterey, California, June 28-30, 1993

(NASA-TM-I06271) SPACE N94-I0811 TRANSPORTATION ALTERNATIVES FOR LARGE SPACE PROGRAMS: THE INTERNATIONAL SPACE UNIVERSITY Unclas , .: SUMMER SESSION t I992 (NASA) 25 p _,:...._.,

PT G3/16 0175557 _T . Space Transportation Alternatives for Large Space Programs: The Intemational Space University Summer Session - 1992

Bryan Palaszewski* National Aeronautics and Space Administration Lewis Research Center Cleveland, OH

Abstract. Nomenclature

In 1992, the International Space University CAN Canada (ISU) held its Summer Session in Kitakyushu, DOE Department of Energy Centre Nationale d'Etudes Japan. This paper summarizes and expands CNES upon some aspects of space solar power and Spatiale space transportation that were considered during EOTV Electric Orbital Transfer that session. The issues discussed in this paper Vehicle are the result of a 10-week study by the Space ESA European Space Agency Solar Power Program design project members ETO Earth to Orbit and the Space Transportation Group to EVA Extravehicular Activity investigate new paradigms in space propulsion FRA France and how those paradigms might reduce the costs FY Fiscal Year for large space programs. The program plan was GEO Geostationary Earth Orbit to place a series of power satellites in Earth orbit. GPS Global Positioning System Several designs were Studied Where rnany kW, GW Gigawatt MW or GW of power would be transmit_d to H Atomic Hydrogen Earth or to other spacecraft in orbit. During the HLLV Heavy Lift Launch Vehicle summer session, a space solar power system was ISAS The Institute of Space and also detailed and analyzed. A high-cost space Astronautical Science transportation program is potentially the most ISU International Space University crippling barrier to such a space power program. IUS Inertial Upper Stage At ISU, the focus of the study was to foster and Isp Specific Impulse develop some of the new paradigms that may JETRO Japan External Trade eliminate the barriers to low cost for space Organization exploration and exploitation. Many international JPL Jet Propulsion Laboratory and technical aspects of a large multinational JPN Japan program were studied. Environmental safety, kW Kilowatt space construction and maintenance, legal and LSS Large Space Structures policy issues of frequency allocation, technology METS Microwave Energy Trans- transfer and control and many other areas were mission in Space addressed. Over 120 students from 29 countries MILAX Microwave Lifted Airplane participated in this summer session. The results Experiment discussed in this paper, therefore, represent the MTNIX Microwave Ionosphere Non- efforts of many nations. linear Interaction Experiment

* AIAA Member,

Copyright © 1993 by the American Institute of Aeronautics and Astronautics, Inc. No Copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all fights under the copyright claimed herein for Government purposes. All other fights are reserved by the copyright owner. M1TI Ministry of international optimistic incarnations, it can provide almost Trade and industry unlimited power for all of the world's MPD Magneto Plasma Dynamic industries. Finding where the truth lies will MSS Master in Space Studies require more thoughtful consideration. MW Megawatt NASA National Aeronautics and Space Solar Power_Background Space Administration and History_ NLS National Launch System OTV Orbital Transfer Vehicle During the early 1960's, several researchers PLV Personnel Launch Vehicle considered the possibility of collecting POTV Personnel Orbital Transfer energy from the Sun and transmitting it to the Vehicle Earth. Peter Glaser (Ref. 6) was the first to SDI Strategic Defense Initiative propose and patent the idea of beaming solar SEE Societe des Electriciens et des energy from a satellite to Earth. Some of the Electroniciens first experiments with ground-based beamed SFU Space Flyer Unit energy were conducted with a small-scale SHARP Stationary High Altitude helicopter (Ref. 7). JPL and NASA Relay Platform conducted other larger scale demonstrations SPS Solar Power Satellite of the technology for power beaming in the SSPP Space Solar Power Program atmosphere. Amongst these are the world's SSTO Single Stage to Orbit highest power level transmitted by STS Space Transportation System microwave beam through the atmosphere TSTO Two Stage to Orbit (Refs. 8 and 9). A total of 30.4-kW of USA United States of America beamed power was received at the NASA- JPL Deep Space Network Station in Goldstone, California. An array of lights IntrogI¢ction were illuminated from a distance of 1540 meters. Space power has been studied in the past as an alternative to terrestrial power systems (Refs. 1, The NASA-DOE study (Refs. 2, 4) 2, 3, 4, 5). Its attractiveness lies in the thought investigated large scale 5-GW power level that because energy is produced in space, the solar power satellites. Detailed conceptual thermal and material pollution of the Earth can be designs of all of the components were substantially reduced. Also, because these developed over a period of 5 years from power stations are in space, there is thepotential 1976-1980. Dozens of these satellites would for continuous power. With no cloud cover, be needed to power the USA or any other storms or other weather to obscure the solar large industrial user nation. All of the radiation, power can theoretically be generated 24 satellites would operate in Geostationary hours a day and transmitted as it is made. This Earth orbit (GEO). A typical size for these seductive concept becomes more attractive if the rectangularly-shaped satellites is 5 by 10 km. costs of all of the required technologies to This large surface is almost entirely covered assemble and maintain it are small compared to with solar cells. As the energy is produced, competing terrestrial power sources. it is transmitted to a ground station with a microwave beam. The transmitting antenna Many past studies of space power have made diameter is 1 km. The frequency of the both realistic and optimistic assumptions of the microwave transmission would be 2.45 costs of the power generation, of maintenance, GHz. On the ground, a receiving antenna, or and of transportation technologies. In the most rectenna, would intercept the beam and realistic and near-term cases, space power can ground processing stations would convert the provide specific benefits for a restricted set of energy into usable power for the main users in space and on the ground. In its most electricity grid. While ambitious,thisideafor generatingpower andinternationalagreements.This for Earthisexpensive.Theinitial investment interdisciplinaryperspectiveis wherethe costsbasedon theNASA/DOE studyestimated IntemationalSpaceUniversity(ISU) can theinvestmentcostsoverthefirst 30 yearsto be playanimportanteducationalandtechnical morethan2 trillion dollars(FY 1992dollars, role. Ref. 1). Thepaybackfor thesystembegan20 to 40 yearsafterthefirst operationalpowersatellite Wha_ Is the International launch. Evenwith aninternationalprogram,it is Space University2 unclearthat SpaceSolarPowerwill beattractive in alargescaleapplication. ISU therefore The ISU is a major venue for students from embarkedon thetaskof finding amorecost- all over the world to discuss and assess effectivemethodorpathto developthe future space missions and applications. Not technologiesfor SSPP. only does ISU provide a fertile ground for the review of space projects, but it allows As partof the199210-weekInternationalSpace persons from all over the world to meet and UniversitySummerSession,severalalternative attempt to open the floodgates of international spacesolarpowersystemswerestudied.Space communication between space enthusiasts. powersystemsfor ground-basedandspace- basedpowerusagewereenvisioned.During this Each summer since 1988, ISU has study,manyof theassumptionsof pastanalyses sponsored a 10-week session in a different werereviewedandcritiqued. Thelargedrivers city around the world. Cambridge, in costwerereviewedanda seriesof Massachusetts (USA), Strasbourg (FRA), demonstrationprojectswereconceivedto show Toronto (CAN), Toulouse (FRA), and thepossiblebenefitsof spacepowerfor ground- Kitakyushu (JPN) have been past ISU sites. baseduse.Thecostreviewhelpedfocusthe These sessions are a very intense time of directionof our studygroupsandallowedusto education and commitment to a design list importantdirectionsfor futurestudies.The project. To complement the stresses of the demonstrationprojectsshowedthatthecostsof academic workload, there are many cultural spacesystemsarenotlow. Futuresystemsmust and social activities to promote a cooperative establishnewparadigmsin spaceflight to reduce atmosphere amongst the students and the thesecostsif spacepoweris to becomeaviable faculty. In Kitakyushu, the ISU community energyalternative. was even invited to perform traditional Japanese dances in a local festival. Thecostof spaceaccesswasoneof themajor costfactorsin thedevelopmentandoperationsof The summer sessions will ultimately be spacepowersystems.Spacetransportationcosts complemented with a permanent campus site havehistoricallybeenamajorinfluenceonspace where ISU will offer a Master in Space programcosts(Refs. 1-5). Largespace Studies (MSS) degree. This campus will be programs,especially,will usespace in Strasbourg, FRA. Additional affiliate transportationsystemsextensivelyand campuses will also be chosen to further frequently. To reducethecostof thesesystems, continue and promote ISU research and newmethodsandparadigmswill berequiredto education in a large number of additional remakethefaceof space.Laterin thepaper,a cities. These campuses will not offer numberof spaceaccessmethodswill be academic degrees, but their work will foster discussed. students' international space cooperation.

To fully assessthespacetransportation Departments, Lccture_,and Workshops influenceson costsandotheraspectsof the program,abroadsystemsperspectiveis needed. Nine departments are part of the ISU lecture Thisview will uncovertheeffectof otherpartsof series during a summer session: Architecture, thesystemaswell astheinfluenceof thelegal Business and Management, Engineering, Life Sciences,PhysicalSciences,Policyand composed of students from 5 countries: Law, ResourcesandManufacturing,Satellite France, Germany, Japan, Sweden, and Applications,andHumanities.Five weeksof USA. Though not direct members of the corelecturesallow eachdepartmenttocoverthe group, representatives from China and basicspace-relatedtopicsthatarepartof the Russia also provided their perspectives on designproject. Otherspeciallecturesand space launchers. All agreed that launch costs seminarsarealsoprovidedbyvariousluminaries are a major stumbling block to success and in the international space community. These cost-effectiveness in large programs. lecturers include astronauts and cosmonauts, directors of various nations' space programs, artists, historians, entrepreneurs, and ISU Table I alumni. Also, researchers from the local area are Environmental/Safety Group Issues invited to perform joint experiments with the for SSPP students as part of the departmental workshops. For example, the Shimizu Corporation provided a domed area where a Mars surface drill was Living Organisms simulated and used by engineers from The Human: Institute of Space and Astronautical Science Effect of Microwaves (ISAS), Nishimatsu Construction Company, and Political, Social Influence Nagoya University to investigate different boring Heating techniques (Ref. 10). Various consistencies of Other: simulated Martian soil and different drill Effects on Flora, Fauna techniques were evaluated over a period of one Protection Needs week using ISU student volunteers to conduct Safety Demo the experiments. Atmosphere Design Projects Microwave-Atmosphere Interactions Safety Demo During the summer session, there are technical Global Warming design projects that involve all of the students. After absorbing the core lecture materials, and Rectenna having many hours of additional lectures on how Local Environment Effects to approach our design projects, students are Rectenna Placement organized into task groups. During the first Hydrology, Geology, Aesthetics phase of the design project, our groups were asked to identify important questions to be Launch Systems answered during the second phase of the project. Environmental Damage (Atmosphere, Several groups were formed to address the issues Land) of economics-business, demonstration-specific Space Debris problems, political-social-legal, technical, and Demo of Environmental Impacts environmental-safety. As an example, Table I lists the major issues discussed by the environmental-safety group. Each group Why the ISU Space Solar Power represented numerous disciplines which yielded Program? new perspectives on many space issues. This interdisciplinary aspect is one of the major One function of the SSPP was to develop a strengths of ISU. cost-effective incremental program for the demonstration of space power. This step-by- In the SSPP design project, the ISU international step approach was proposed by Peter Glaser perspective gave new insights into almost any (Ref. 11) and embraced by the ISU. Based space issue. Our space transportationgroup was on the initial solar power satellite cost estimates,it is notclearthatonenationcould experiments to demonstrate the feasibility of affordsucha system.An incrementalprogram differing aspects of power beaming and mightallow lesscostlydemonstrationsand reception. Figure 1 shows the SSPP generatesufficientconfidencefor international approach and development plan (Ref. 1). partnersto becomeinvestors. By attackingthe There are five major phases: space to space, smallest,simplestpiecesof theproblemfirst, the terrestrial testing, space to Earth, large-scale succeedingstepswould hopefullybecomemuch precommercial satellites, and solar power easier.Also, thevisibility of thedemonstrations satellites. In each of these phases, Earth- wouldfoster public acceptanceof beamedspace bound experiments with point-to-point power. transmission and other environmental impact studies and/or research would be conducted Japanandothernationshaveembracedthis prior to any large space demonstrations. phasedapproach(Ref. 12). Severaldesign studieshavebeeninitiated(Ref. 12):SPS2000, Small Space ExNriments SpaceFlyerUnit (SFU)EnergyMissionStudy andMicrowaveGardenProject. Also, small- Small experiments or demonstrations were scaleexperimentshavebeenconducted:the proposed as the vehicle for popularizing MicrowaveLifted AirplaneExperiment space power. One idea even suggested using (MILAX), MicrowaveIonosphereNonlinear a roll-out rectenna or "magic carpel' (Ref. InteractionExperiment(MINIX), andMicrowave 18) that would intercept a microwave beam EnergyTransmissionin Space(METS). The from a passing satellite. This demonstration, lattertwo projectswerelaunchedon suborbital though appearing somewhat whimsical, soundingrockets.The soundingrocket could allow power to be available in remote experimentsusedhigh-densitymicro-electronics areas over longer periods of time. A follow- andhaveshownthepotentialfor lightweight on program might provide more-continuous powergenerationandheatrejection.The power to developing nations and remote JapaneseMETS experiment,launchedin early exploration sites (in equatorial jungles, etc.). 1993,transmitted1kW of electricpowerfrom a soundingrocketmothervehicleto asmaller Lgw-(_ost Demonstrators daughterfreeflyer releasedfrom themother rocket. This experimentwasconductedin During the study, several demonstration cooperationwith theUSA's Centerfor Space projects were conceived to provide some data PoweratTexasA&M UniversityandtheNASA on power transmission and integration of the Lewis Research Center. spacecraft, the solar power generation, and the microwave power-beaming technologies. Canada and Europe have also conducted or are A wide range of ideas were proposed, planning experiments that show their increasing including a transportation experiment with interest in beamed power (Ref. 13). The electric propulsion. Stationary High Altitude Relay Platform (SHARP) was conducted by Canada to Cost constraints were given for two of the investigate long duration airplane surveillance demonstration missions: 80 and 800 million and communications (Ref. 14). The European dollars (FY 1992). In the 80-million dollar Space Agency (ESA) has held several mission, the Russian Mir space station and international conferences on space power (Refs. robotic Progress tanker vehicle combination 15, 16, 17). was used. This experiment allowed a demonstration of space-to-space transmission The Design project: A Phased and reception. Power was planned to be Approach transmitted from the Mir to the Progress and the power level of the experiment was to be a Using the phased approach (Refs. 1, 11), the maximum of 10 kW for multiple 1-hour SSPP team attempted to identify the best durations. The use of existing Russian spacecraftallowedasignificantcostsavingsover Qther SSPP Issues acompletelynewvehicledesign.Forthe800- million-dollarexperiment,alargespacecraftin The specific issues that were studied also sun-synchronousorbit with a 1000-kmaltitude included many of the international and wasassumedfor space-to-Earthpower-beaming technical aspects of a large multinational experiments.At 1000km, thesatellitewould program. Environmental safety, space deliver50kW to a 1-km2rectenna.Thoughthe construction and maintenance, legal and groundstationvisibility timeatthislow altitude policy issues of frequency allocation, wasonly 5 percentof an orbitalperiod,the technology transfer and control, costs and experimentplanwasto demonstratethatbeaming many other areas Were addressed. Tables 11 to equatoriallocationswaspreferrableto the and HI show the specific groups that were originally-selectedAntarcticregionsdueto higher formed to address these issues and the major orbitalvisibility andthelower lossesatthe issues, respectively. Some of the important equator.Themajorlossesatthepolarareasare results are presented in the next sections. dueto blowing snowandice inadvertently coveringtherectennas. Table I/ Two additionalexperimentswerealsodesigned: Task Groups of the Space Solar Power onefor under8million andonefor 2-3 billion Program dollars. In the8-million-dollarexperiment,a smallsatellitewouldinterceptmicrowave transmissionsfrom the300-mdiameter • Assumptions, Intentions, and radiotelescopein Arecibo,PuertoRico. The Extemal Relations satellitewouldbelaunchedaboardanAriane • Scheduling rocketasa auxiliarypayloadandplacedinto a • Legal and International Relations polarorbit. Weighinglessthan150kg, the • Business Planning satellitewoulduseaninflatablerectennaand • Environment and Safety interceptasmallfractionof thebeamedenergy • Space Transportation from Arecibo. Themore-costlymultibillion • Manufacturing, Construction, dollarexperimentsbeamedenergyfrom spaceto and Operations Earthandrequiredaminimumof two Russian • Spacecraft EnergialaunchesandseveralUSA STSflights. • Power Collection, Conversion, Thesevehicleswould havea 1-MW solar-array and Distribution powerlevel, operateatafinal altitudeof 20,000 • Technical Trade Identification to 36,000km, andbeampowerto near-equatorial groundrectennas.A rangeof differentsatellites wereanalyzedto assesstheassembly requirementsandthecostsfor severalhigh- Energy Analysis. To justify the powerprecursorpowersatellites.Thoughthe consideration of space power, and to costof thissystemwasseveralbillion dollars, quantify the need for future power systems, a thesesatellitesarerelativelylow-costversionof preliminary energy analysis was conducted. thehigh-power5-GW powersatellitesproposed The predicted energy needs of the world and aspartof afull-scalesolarpowersatellite the supplies of current energy resources were constellation. compared. Current terrestrial energy sources considered in this analysis are listed in Table Theresultsof thesedesignexampleswerelong, IV. Several future energy consumption extendedexercisesfor thestudentsin the scenarios were considered: low, medium, difficultiesandintricaciesof planningspace and high growth. In all of these cases, the projects. All of thestudentslearnedan total demand for energy will increase, with importantlesson;theywereimpressedwith how the low model increasing by 150 percent (2.5 smallthereturnwasfor theinvestedcost. times the current rate) and the high model TableffI Table IV Critical Issuesfor SSPP(Ref. 1) Current, Potential and Speculative Power Sources Desi[n ProiectGroup Issue Spacetransportation reductionof ETO launchcosts Current: Spacecraft attitude,orbit, and Fossil Fuels: Oil, Gas, Coal vibrationcontrolof Nuclear Fission LSS Potential: efficientradiators Fusion Powercollection, moreefficientpower Geothermal conversion,and conversionsystems Biomass distribution Wind Environment, determine beam Solar - Thermal and Photovoltaic effects on biota and Ocean - Thermal, Tides, and Currents physicalandlife Extraterrestrial Resources sciences Earth's atmosphere Socialandpolitical create intemational Speculative: management group Black Holes for space solar power Crystals project Human: Bicycles, Treadmills Volcanos ensure security of satellite and beam Gravity Waves Antimatter develop advanced Manufacturingand Alternate Universes assembly techniques assembly Tachyons in robotics and EVA Businessandother achieve business feasibility for program provide 90 percent of the world's energy (Ref. 19). These sources are destined for search for long-term depletion in the early part of the 22nd funding Century. The other 10 percent of the energy is produced by nuclear fission, hydroelectric achieve scientific and other technologies, such as solar and acceptance wind.

public awareness Alternative energy sources were also identified using a brainstorming method. having a 400-percent increase (5 times the current Many alternative technologies are available rate). for sustaining the Earth's needs. The time scale for the depletion of the natural Alternative Energy Sources. A wide resources may be a driver for the logical range of energy sources were considered as progression of space power from its current competitors with space power. The potential formative stages to its genesis as a major alternative energy sources are shown in Table IV. power supply. Some of the unusual and The current energy sources of coal, oil and gas striking altematives that were considered ..... during the brainstorming sessions were black holes and crystals. base-load power, a low-cost space power A preliminarycomparisonof thecostsof power system might provide benefits. systemsis presentedin Figure2 (Ref. 20). It is clearthatthebest-estimatecostof space-based Electric propulsion systems have been poweris veryhigh:2 to 6 timesthatof acurrent investigated for orbital transfer missions and ground-basedalternative.Thoughthisanalysis especially for deployment of space power showsthatspacepowermaybeunattractivem satellites. Electric propulsion is already thenearterm,theanalysisdoesnotincludethe acknowledged as a powerful force in costof environmentalimpactandtheneedfor reducing the costs of space transportation increasingenergydemandwith thedepletionof (Refs. 2, 4, 21). Using beamed energy with currently-availablefossilfuels. Oncethesecosts electric propulsion, in the proper form and areincluded,thepicturemaydramatically manner, might further reduce the cost of this change.Thefinal analysiswill dependuponthe transportation option and the overall SSPP. urgencyof theneedfor alternativepower,the This concept involves bootstrapping the use technologyreadinessof thesealternatives,and of the power satellite: using it for a traditional thepolitical will to investin futurepower power demand as well as powering the directions. Electric Orbital Transfer Vehicles (EOTV) that are lifting their brethren into their final Markets. Another direction our study orbits. Though this may provide a savings addressed was the market for power from space. for the overall transportation system, there is This included not only the space applications but also the added complication of potentially the terrestrial possibilities as well. Table V lists beaming energy to multiple targets and the market opportunities that were found for handing off the EOTV to other satellites as they fall out of the line of sight with their orbital power stations. Table V Markets for Space Power: SSPP Space Transportation Near, Mid and Far Term Issues

After reviewing the existing literature on Space - space power satellite designs, the costs of the GEO and LEO Satellites differing systems were identified and Space Stations assessed. Space transportation was found to Electric Propulsion dominate the cost of advanced power systems in space. In past studies of these Earth- solar power satellites, up to 40 percent of the Remote Sites: program cost was directly related to space Power Relay transportation; this is shown in Figure 3 Peak Power (Ref. 1). The transportation system costs for Primary Power solar power satellites were 40 to 45 percent of the total research, technology and development costs. These costs include the space power. The analysis looked into near-, Heavy Lift Launch Vehicle (HLLV), the mid-, and far-term options for space and Earth chemical Orbital Transfer Vehicles (OTV) markets. Peak power and electric propulsion and EOTVs. Thus, in the planning of future were the two areas where space power might space programs, space transportation will make a large contribution. Peak power is play a critical role. This paper will address needed at times during the day when industrial or alternatives to reduce the cost of space flight other commercial power consumption are and the options for various programs' particularly demanding. Because the cost of peak transportation needs. Innovative power level is at least twice as cosily relative to technologies and new architectures are availableto potentiallyreducethesecostsand traditional lunar transfer vehicles and landers makeall of spaceflight moreaffordable. for personnel and equipment transport. Though the apparent complexity of the TheSpaceTransportationGroupwasformedto system increases, producing materials on the assessnewwaysof conductingspacemissions moon significantly reduced the Earth- thatwouldreducelaunchandothertransportation launched mass. Less mass is needed because costs. Figure4 showsthedriving requirements the energy to transport the materials from the thatwereidentifiedin theoveralldevelopment lunar gravity well to GEO was less than that planfor spacesolarpower. Theseplanning from Earth to GEO. However, even with the activitiesidentifiedtheinteractionsbetweennot use of lunar materials, the payoff for the only our differentspacesystemareasbutalsothe space power systems is typically many internationalandpoliticalforcesthatareacritical decades in the future (Refs. 1, 22). partof thislargespaceprogram. The Combining and using innovative propulsion interactionsof theSpaceTransportationGroup concepts might further reduce the time for with theothergroupsin thespacesolarpower SSPP to pay for itself. We therefore programarealsodepictedin Figure4. These embarked to identify new ways to make interactionsincludetheselectionof the space transportation cheaper and therefore appropriatelaunchvehiclesfor demonstration make SSPP more attractive. missions,theidentificationof marketsfor space transportationrelatedto spacepower,the New Paradigms discussionof thepayloadaccommodationof the differingsatellitepayloadsandthereviewof A paradigm is a model of how things should issuesrelatedto themostpromisingtechnologies be done. New paradigms for space thatmeritfurtheranalysis. transportation include a number of technologies and vehicle concepts that when NASA/DQE Study: Transportation taken together, may reduce the costs of space access. The technologies and vehicle types In the studies conducted in the late 1970's, the that appeared most promising for cost elements of space transportation were divided reductions were cataloged. A method of into Earth to Orbit, orbital transfer and lunar selecting the technologies and vehicle transportation. Initially, the transportation concepts for the various mission types was included only an Earth-centered system. The also developed. primary elements were heavy lift launch vehicles with electric propulsion and chemical propulsion Transportation Costs OTVs. A lunar transportation system was placed in the systems analysis after realizing that Earth The costs of space transportation included transportation costs were too high to make space not only the monetary value of the vehicles, power economical. Lunar materials were but also the "costs" of reliability, processed into propellants and building materials accessibility, launch environment, operability to construct the solar power satellites. and vehicle resiliency. These costs may Production factories would be transported to the severely limit the viability of a space solar Moon and the initial cost for emplacing them power system if not addressed early in the would have to be paid. After these factories paid program. The technologies and vehicle for themselves and lunar materials were used in concepts we reviewed were assessed based lieu of those strictly from Earth, the cost of the on their ability to allow reduction in all of the satellite systems dropped dramatically. A cost of space flight, not just reductions in its number of transportation vehicles had to be dollar value. We also prepared a white paper added to the overall system. These included a which discusses these other important costs mass driver, mass catcher, lunar base, oxygen for space transportation (Ref. 1). and construction material production plants on the lunar surface and/or in space, and the

9 space transportation and their link to different TableVI vehicle concepts. Many of the technologies PropulsionTechnologyandVehicleLink have been considered over the last fifty years To SSPPApplications and have greatly varying degrees of technology readiness. Several of the Earthto Orbit: technologies were considered most attractive MetallizedPropellants for cost reductions and these will be High EnergyDensityPropellants discussed later in the paper. High EnergyChemical(O2/H2,etc.) SlushHydrogen Selection Criteria. In the planning for GunPropulsion space solar power, there are three power MassDriver level ranges that were considered and they LaserPropulsion can be thought of as directly linked to the • Vehicles- level of advancement in the space TSTO transportation system. Table VII summarizes SSTO the power level influences. For HLLV Pressure-FedBooster Table VII Lunar: SSPP Power Influence On Transportation In-Situ Propellants Technology MassDrivers/ Mass Catchers Gun Propulsion High Energy Chemical (O2/HE, etc.) Power Advancement Level Needed Aerobraking/Aerocapture • Vehicles - Range Lunar Transfer Vehicle Lunar Excursion Vehicle kW • New Vehicle Orbital Transfer: Technologies Solar and Nuclear Electric Propulsion Beamed Energy Electric Propulsion MW • New Systems or Architectures Nuclear Thermal Propulsion High Energy Chemical (O2/H2, etc.) GW • New Paradigms: Aerobraking • Vehicles - Lunar transportation, Extraterrestrial resources Light Weight Upper Stage

Propulsion-Related Technologies Light Weight Structures High-Temperature Materials example, if only several kW of power were • Vehicles - planned to be delivered, then relatively small improvements in technology would be All of the Options Above required. However, if large satellites of the GW power level were developed, it seems clear based on past assessments (Ref. 5) that Technologies a new model of space transportation, a new The Space Transportation Group compiled a list paradigm, would be needed. This new of future technologies that could potentially paradigm might entail lunar transportation - reduce the cost of access to orbit. Table VI is a using in-situ resources to construct propulsion systems, and the satellites compilation of the technologies considered for

10 themselves,usingminimal Earth-derived Theimportantresultsof thistransportation resources.This newsystemmight includemass technologysurveyarediscussedin thenext driversandhavea minimaldependenceon sections. traditionalrocketpropulsionsystemsfor ascent from theMoon's surface(Ref. 5). Big D0mb Booster. This launch technology was considered in the early In-situ resources,however,do notnecessarily 1960's as a method of placing large payloads solveall of thetransportationproblems.To place into orbit. Several different types of engine all of theelementsof thelunartransportation technologies were considered but one that systemin place,theymustinitiaUybelaunched was most attractive was the pressure-fed from Earth. Thereis thereforea paybacktime booster. Because this rocket used no high- overwhich themassof thelunarbaseandits pressure turbomachinery, it is perceived as a transportationsystemsareamortized.This very simple vehicle. With the pressure-fed paybackmaytakea decadeor more. Also,all of booster, propellants are fed to the engines thematerialsof thesolarpowersatellitemaynot with only the pressure from the propellant beeasilyfabricablefrom lunarresources.The tanks. The tankage pressures for this qualityof solarcell productionfrom lunar booster are typically very high: 300-500 psia. materialshasbeenbothsupportedandquestioned This is in contrast to the low-pressure, 50- (Refs.23,24, 25). This andothercompeting psia, thin-walled tankage designs that are paradigmsshouldthereforebeexaminedbefore typical of flight systems like the Space anytransportationsystemdesignis finalized. Shuttle or Ariane. Versions of the pressure- fed booster have been proposed in its most Thedecades-longpaybackperiodalsoled usto ambitious form in the Sea Dragon (Refs. 27, believethatgovernmentsupportwill beneededto 28) and most recently in the SEA Launch sustainsuchalongprogram.Commercial And Recovery (SEALAR) concept (Ref. invesmaentmaybe solicitedafterthefull-scale 29). spacepowersystemhasbeenprovenandputinto practicaluse. Othersmaller-scaleprograms, The Sea Dragon (Ref. 27) was the fh-st large suchastheremotesitepowerrelayorthepeak pressure-fed booster to be studied for space powerapplicationmightattractearliercommercial missions. It was a two-stage rocket with a investors,but it is unlikely thatinvestorsalone payload to LEO of 1.1 million Ibm. Its name will absorbtheinitial start-upcostfor spacesolar was derived from its large size and the fact power. that it was sea launched. The Sea Dragon was over 540 feet long, 75 feet in diameter, Two vehicleparadigms,theBig DumbBoosters had a GLOW of 40-million Ibm and a liftoff (Ref. 26,27,28, 29) andTwo Stageto Orbit thrust of 80-million lbf. Each stage used (TSTO,Refs.30, 31,32,33) aretechnologies only a single engine to deliver its total thrust thatcanpotentiallyreduceSSPPcosts. These level. Its impressive dimensions would vehicletechnologiesreducethenumberof perhaps be unwieldy in a land-based launch componentsandpotentiallysimplify the pad but using the ocean obviates the massive operationsfor theoveralllaunchsystem.Higher infrastructure of a fixed launch site. Other densityandhigherIsppropellanttechnologies support facilities, such as a dock for wereamongsttheothertechnologiesconsidered construction and refurbishment are required, (Ref.34,35). IncreaseddensityandI_pcanbe but the relative cost of the ocean-based dock importantfor smaller,lighter,more-compact to the land-based launch pad favors the ocean rocketsbecausethelowerdry massof therocket, system (Ref. 27). Also, with the ocean- theeasierit isto achieveorbit. Thisaspectcan based system, nearly any size rocket can be becriticalfor TSTOandespeciallyfor SSTO launched without creating a new launch vehicles.Thetechnologiesthatour Space facility. The first stage was to be recovered TransportationGroupdeemedmostlikely to at sea and towed to the launch vehicle reducecostswerediscussedin themostdetail. shipyard where it would be refurbished.

11 a potential interim step prior to developing a Thevehiclealsowasdesignedto usetankage Single Stage to Orbit (SSTO) vehicle. madein shipyardsratherthanin theclean-room Turbojets and scramjets on the TSTO will environmentof atypical aerospacefactory. produce much lower velocities than that for Shipyardswereconsideredbecausethesizeof an all-airbreathing SSTO. Therefore the thetankagewasextremelylargeandits walls airbreathing technology is much more near werevery thick. With the 1.1million poundsof term than the Mach 25 scramjets needed to go payloaddesign,theSeaDragonfuel tankwall to orbit. thicknesswasseveralinches,amarkedcontrast to thedelicatepaper-thintankageof ourcurrent The TSTO appearedattractive because of the launchvehicles.Thelaunchvehiclestageswere aircraft-like operations afforded by winged designedfor ruggeduse,including searecovery stages. Though the current Space Shuttle is a with minimal aerodynamicbraking,andtherefore winged vehicle, it does not have any of the aerospace-standardtolerancesandcleanrooms airplane-like operational characteristics of the werenotrequired.Thecostof usingshipyard- TSTO. The first stage, with the large air- qualityfabricationtechniqueswassubstantially breathing engines, can be maintained with below thecostsin themore-typicalaerospace many of the well-developed techniques plantwhichfurtherreducedtheestimatedcostof employed by the military for high-speed thelaunchsystem. aircraft. The Space Shuttle requires a large army of technicians to assess its safety after Themore-recentSEALAR programwasa each flight. Hopefully, that large contingent reusable,sea-launchedrocketthatcanplace of personnel could be pruned with the new 10,000-to 140,000-Ibmpayloadsinto LEO (Ref. TSTO approach. 29). With a SEALAR rocket,manypayloads couldbelaunchedat ahighrate,whichwasvery Single Stage to Orbit. The advent of attractivefor potentialStrategicDefenseInitiative high performance rocket engines and lighter (SDI) applications.Subscalewaterimmersion weight structures may someday make the testsof therocketcomponentsandshipboard concept of Single Stage to Orbit vehicles a rocketenginef'wingswereconductedin the reality (Ref. 31). Because the vehicle only SEALAR program. However,dueto budget needs to be reloaded with propellants and reductions,SEALAR wasneverfully serviced, the cost of operations is demonstrated.Its inspiration,SeaDragon,was theoretically reduced. Current rocket and perceivedassomewhatradicalandimpracticalby material technologies, however, make SSTO NASA in the 1960'sdueto its immaturedesign impractical. The current technology levels andthepotentiallow reliabilityof asingleengine for propulsion Isp and lightweight materials system. Their potentialto lift largepayloadsat can only deliver a marginally-small payload reducedcost,however,maketheselargesea-or to Low Earth Orbit. Development of these ground-basedpressure-fedboostersstrong technologies may be driven by the needs of candidatesfor reducinglaunchcosts. an SSPP-type endeavor. As discussed in the TSTO section, airbreathing SSTO is also Two Stage to Orbit. This launch vehicle an option, but the technology required is in uses an airbreathing first stage and accelerates a the development stage. The TSTO therefore second stage to a speed of approximately Mach 6 seems to be a more near-term SSPP option to 10 (Ref. 30-33). The first stage is a winged for reduced launch costs. airplane. A rocket-powered second stage then proceeds to orbit. The airbreathing stage flies Guns. Gun propulsion is a way to back to an airport-like landing area for provide orbital velocities while leaving the refurbishment. The second stage may be either a main "propulsion" system on the ground. payload canister or a reusable flying vehicle. The Using a high muzzle velocity gun or cannon operations of this vehicle can potentially be very to launch payloads is potentially attractive if simple compared to traditional rockets. It is also the payload is insensitive to shock and

12 vibration (Ref.36). Thepayloadmustalsohave trade studies and an optimization of power a systemto allow maneuveringafterthelaunchto level and thruster performance is therefore circularizetheorbit. A highmassfractionfor needed. propellanttanksandotherstructuresmaynotbe possiblewith suchhighlaunchvelocitiesand With electric propulsion, a vehicle thrust to accelerations.Also, aremotesitewill haveto be weight of 10 -4 to 10-6 is typical. The low selectedfor thelaunchof theprojectiles.The acceleration requires long thrusting times in noisegeneratedby thefiring during launch will Earth orbit or in Earth-lunar space. An be very high. An estimate of the distance to attitude control system is needed that will minimize the sound level to 70 dB is 2 km (Ref. autonomously maintain the correct thrust 36). A similar safety distance is typical for a angle and attitude of the entire vehicle during rocket launch. Many of the past studies have the long orbital transfer. Also, large light discussed the mass of the projectile and ignored weight flexible structures are typically used the added mass to withstand the high for the solar arrays and other power system accelerations during launch. Current studies structures, taking advantage of the low have included these factors and have shown acceleration of the vehicle. promising results. An SSPP using this technology would have to acquire and use many There are several thruster technologies that small masses and assemble them into the final are appropriate for OTVs. They are ion, vehicle. Typically, the proposed gun launchers arcjet and Magneto-Plasma-Dynamic (MPD) have payloads of 1,000 kg. Assembling these thrusters. Each system can use varying many small masses into a large operational propellants and the performance is dependent vehicle may be a significant challenge. upon the propellant selection. Ion propulsion will typically use inert gas propellants, such Electric Propul_;ion. The technology of as xenon, krypton or argon. Arcjet thrusters electric propulsion will potentially allow great may use hydrazine, ammonia or hydrogen. reductions in the cost of space transportation. It For MPD thrusters the propellants may be enables this through the reduction of the mass deuterium, hydrogen or even lithium for very launched into orbit, the reduction of the mass of high efficiency engines. the propulsion system, and the reduction of the payload capacity needed of the launch vehicle to By using electric propulsion, the Isp of the place a payload into orbit. All of these factors upper stage propulsion system is increased can reduce overall program costs. very significantly: up to 5000 lbf-s/Ibm versus the typical values of 300 to 450 lbt" Electric propulsion differs fundamentally from s/Ibm for chemical propulsion. An example chemical propulsion in several ways: electrical of reducing the launch vehicle size is the use power supply, low acceleration, large flexible of solar electric ion propulsion for the structures and low-thrust attitude control. A deployment of Global Positioning Satellites large electrical power system is carried on board (GPS, Ref. 21). Over the life of the GPS the vehicle to provide energy to electric thrusters. system, the total cost savings will be many This electrical energy is used to ionize and billions of dollars. Similarly, for space accelerate a propellant to very high speeds. This solar power, electric propulsion offers the acceleration produces a very high Isp. Because most efficient method of emplacing and of the high Isp, the total mass of the vehicle can maintaining the satellites. be significantly reduced over chemical propulsion. This is especially true for the very Pr0gramPlan high energy missions. The performance of an electric OTV is strongly dependent upon the In addition to assessing the propulsion power technology, power level and the Isp of the technologies and vehicle options, we also thrusters. For each mission type, a series of created a timeline for the development of the

13 flight systems needed for a solar power satellite advanced propulsion technology is clear only program. Figure 5 shows a simplified schedule if very high power levels are desired. In our and flowchart of the SSPP. Four demonstration planning, the low-cost demonstration missions, which were discussed earlier in the missions occur in 1992, 1996, 2005 and paper, are planned, each using existing boosters 2012 (see Figure 5). The first advanced with some small modifications and near-term space transportation system is available in technology upgrades. 2006. Therefore, no new launch system is available for the first three demonstrations. One critical problem with space transportation Existing boosters such as Ariane, Space development for SSPP is the time scale that is Shuttle and Energia will be used. considered. Over the period from 1992 to 2037, many improvements in technology are possible. For the fourth demonstration and the Therefore, two iterations on the design of the remainder of the SSPP, the f'trst iteration of vehicles and the technologies are included in the the new transportation system will be plan. Though technology infusion has moved available. It is planned to have yet another slowly in the past twenty years, the impetus of generation of launch vehicles completed prior the SSPP may provide the incentive to advance to the final full-scale deployment of SSPP. transportation technology at a higher rate than has In the 30 years from 2006 to 2037, there is been seen previously. International investments, sufficient time in the schedule to not only from space programs but from energy- accommodate this new vehicle's development based investments, may provide the funding to and operational testing. The new leap-frog to the next generation in technology transportation paradigms, if any, would be rather than following the typical, ponderous born from this phase of the program plan. evolutionary path. Sufficient time would be devoted to systems analysis and technology development to After the initial identification of the vehicle sizes assure that the new paradigms would reduce required for the power satellites, the vehicle costs and make the system "better, faster, selection will be made. Depending on the cheaper." satellite technology to be demonstrated, the launch system will have to be designed or current Concluding Remark_s vehicles and systems will be pressed into service. For example, if the demonstration were only for Only by reducing the costs of space a small-scale power beaming demonstration, transportation can solar power from space there would be no need for new technology. become feasible. With many past studies of solar power satellites, the transportation Prior to 2006, the technologies that were system cost has been 25 to 40 percent of the perceived as important in the 1992 time frame total program cost. Even with current space will be developed. In 2006, the reevaluation of projects, the cost of space launch services is the STS concepts would begin. New technical terribly high. Without active measures to developments would hopefully allow lower cost bring down the costs of space access, the implementations of SSPP. viability of any large space program is questionable. It should also be clear that Because the time scale for SSPP development is these "'costs" include not only dollar value of up to 50 years in the future, it is difficult to point the booster, but also the transportation to a specific technology as the one of choice for a system reliability, accessibility, launch specific application. Innovative solutions to environment and the vehicle resiliency. All many of the technical challenges of space solar of these factors can increase cost and defeat power are possible and it is nearly impossible to our purposes in space. Only through the predict the potential of space propulsion over a application of innovative technologies and five decade span. Though the scale and direction streamlined space launch operations will for SSPP is hard to predict, the need for

14 humankindattaintheheightof perfectionandlow technologicalfuturewill bein space "cost" in spaceflight. transportation. Therearemanyoptionsfor launchingpayloadfor Of themanytechnologiesthathaveexciting aspacepowersystem.In thenearterm,thereare potentialfor costreduction,electric numerouscapabilitiesto deliverlargeandsmall propulsionhasaspecialandimportantadded payloadsto LEO andbeyond.Overthenextten feature.It cannotonly reducethe years,therewill belittle changein thecapacityto transportationcostbutthereis alsoa potential movesateUitessincetherearefewdevelopments marketfor beamedpower. OrbitalTransfer in theplanningstagesotherthanincremental Vehiclesusingelectricpropulsionpotentially vehiclepayloadimprovements.Beyondtheten canbemoreeffectiveusingbeamedpower. yearhorizon,newlaunchvehicledesigns, Usingaremotepowersourcereducesthe propulsionandmaterialstechnologieshavethe massof thetransfervehicle andimprovesits potentialto makeexcitingleapsin payload acceleration.Thisaccelerationshortensthe deliveryefficiency. VehiclesusingTwo Stageto trip timeandmakeselectrictransfernotonly Orbit andSingleStageto Orbithavethepotential moremassefficientthanothercompeting to reduceoperationalcostsof payloadlaunches. propulsiontechnologiesbutalsoreducesthe Simplifyingtheseoperationsis amajorstumbling vehicletrip timeovertraditionalelectric block to makingour accessto orbit affordable. vehicles.Thebenefitof electricpropulsion for spacetransportationandthepotential Many technologiesareavailablefor space marketit maycreatein othertransportation transportationsystemsof thefuture. Thefinal systemsmakesit especiallyattractive. selectionof whichtechnologiesareusedisvery Therefore,usingelectricpropulsionis oneof dependenton thetimeframeof thesolarpower thehighleverageissuesthatshouldbe systemdevelopment.Baseduponthisreport's consideredin anyfuturelargespace developmentplan, thefirst launchvehicle transportationsystem. developmentsfor anylargescalepowersatellites would bein the2005-2010timeframe. Thef'n'st Werecognizetheimportancethatpropulsion satellitewouldbe launchedin 2035-2040. technologieshavefor thesuccessof space Becauseof thelongtimeuntil thefirst vehicle solarpowerandany largespaceprogram. A flight, it would beunwiseto selectaspecific lunarbaseora Marsmissionall needvery technologyor setof technologiesfor the capablepropulsion-intensivevehicles. transportationsystem.Also,thespecific Reducingthe"costs"of spacetransportation architectureof thespacesolarpowersystemwill maymaketheseambitiousprojectsareality. determinetherelativeimportanceof the This isacrucialconsiderationfor thefuture transportationtechnologies.If alargescale of manyspaceprograms.Thesynergismof powersystemis required,theneedfor lunar thetransportationtechnologiesof aspace resourcesmaybecomecrucial. On theother solarpowerprogramwith otherlargescale hand,asmallersatelliteconstellationwouldmost projectscanultimatelyreducethecostof likely notuseextraterrestrial-basedresources. accessto spacefor all nations.Major The propulsiontechnologiesthatwouldbeused reductionsin the"costs"of spaceaccesswill would beadvancesreflectingthepotentialof alsomakespacetruly usefulanddesirablefor SingleStageto Orbit andotherimprovementsin commercialventures.A largelow costspace propulsiontechnologyto increasetheenergy transportationprogram,suchastheonefor densityof propellants(suchasmetallized spacesolarpower,couldbetherising tide propellantsandhigh energydensitypropellants). thatcarriesall spaceships. Light weightorhightemperaturematerialswill alsoplay avital rolein reducingthecostof space operationsandspaceaccess.Onlytimewill tell how ambitiousandexcitingour global

15 Acknowledgements Coloniesin Space, Space Studies Institute Press, Princeton, NJ, 1989. I would like to acknowledge NASA for its support of the International Space University. 6) Glaser, P., "Power From the Sun: It's Also, I'd like to thank the ISU Faculty, the SSPP Future," Science, Volume 162, Number Design Team and the other members of the Space 3856, 1968, pp. 857-861. Transportation Group of the Space Solar Power Program for their significant contributions to the 7) Brown, W., et al., "An Experimental Summer Session Final Report. They are listed Microwave Powered Helicopter," IEEE below: International Convention Records, Volume 13, Part 5, 1965, pp. 225-235. Chistophe Bardet FRANCE Phillippe Berthe FRANCE 8) Dickinson, R., "Evaluation of a Frederic Ferot FRANCE Microwave High-Power Reception- Stefan Foeckersperger GERMANY Conversion Array for Wireless Power Toshiya Hanada JAPAN Transmission," NASA CR-145625, JPL Mario Hucteau FRANCE TM-33-741, September 1, 1975. Yoshitsugu Kanno JAPAN Thierry Le Fur FRANCE 9) Dickinson, R., and Brown, W., Alain Louis FRANCE "Radiated Microwave Power Ulf Palmnas SWEDEN Transmission System Efficiency Michael Reichert GERMANY Measurements," NASA CR- 142986, Masaharu Uchiumi JAPAN JPL TM-33-727, May 15, 1975. Richard Wills USA 10) Kawashima, N., et al., "Development of Drilling Machine on Board Mars References Rover and Drilling Test of Simulated Martian Soil," in Proceedings of the 1) Arif, H., et al., "Space Solar Power International Conference on Missions, Program," Final Report of the Summer Technologies, and Design of Planetary Session of the Intemational Space University - Mobile Vehicles, published by Centre Kitakyushu, Japan, Available from the Nationale d'Etudes Spatiale (CNES), International Space University, Boston, MA, 1992, pp. 337-343. August 1992. 11) Glaser, P., "The Economic and 2) "Space Solar Power Satellite System Commercial Development of Space," Definition Study Phase III, Final Report," Journal of Social Political and Economic Boeing Aerospace Company, Volume 3, Studies, Volume 9, Issue Number 2, 1980. Summer 1984, pp. 211-229.

3) "America At The Threshold: America's Space 12) Anon., "New Technology Japan: Exploration Initiative," Stafford Synthesis Special Issue - Solar Power Satellite Group Report, NASA, U. S. Government R&D in Japan," Japan External Trade Printing Office, May 1991. Organization (JETRO), Three 'T' Publications, Ltd., Japan, 1991. 4) "SPS Concept Definition Study - Systems Subsystems Analyses, Final Report," 13) Deschamps, L., Pignolet, G., and Rockwell International, Volume II, 1980. Toussaint, M., "A European View Regarding Power Transmission in 5) O'Neill, G., The High Frontier: Human Space," 1st Annual Wireless Power Transmission Conference, Feb. 1993.

16 14) Schlesak, J., Alden, A., and Ohno, T., Ninth PrincetorgAIAMSSI Conference, "SHARP (Stationary High Altitude Relay 1989, pp. 144-151. Platform) - Rectenna and Low-Altitude Tests," in GLOBECOM 85 - Conference 24) Criswell, D. and Waldron, R., "Lunar Record - Volume 2, 1985, pp. 960-964. System to Supply Solar Electric Power to Earth," in Proceedings of 25th 15) "SPS 86 - Solar Power Satellites," Societe Intersociety Energy Conversion des Electriciens et des Elecu'oniciens (SEE) Engineering Conference flECEC), 1990, Proceedings, June 1986. pp. 61-71.

16) "SPS 91 - Power from Space," Societe des 25) Brandhorst, H., NASA Lewis Research Electriciens et des Electroniciens (SEE) Center, Chief, Power Technology Proceedings, August 1991. Division, Personal Communication, August 1992. 17) "SPS Rio 92 - Space Power Systems and the Environment in the 21st Century," Societe 25) Anon., "Big Dumb Booster- des Electriciens et des Electroniciens (SEE) Assessment of the Pressure Fed Proceedings, June 1992. Booster," United States Office of Technology Assessment Report, U. S. 18) Collins, Patrick, Foreign Research Fellow, Government Printing Office, No The Institute of Space and Astronautical Number, February 1989. Science (ISAS), Kanagawa, Japan, Personal Communication at ISU '92, July 1992. 27) "Sea Dragon Concept, Volume 1: Summary," Aerojet-General 19) Energy for Planet Earth, Scientific American, Corporation, NASA CR-52817, January Special Issue, September 1990. 1963.

20)Hopkins, M., "The Satellite Power Station 28) Truax, R., "The Pressure-Fed Booster: and the Non-Cost Uncertainty Aspects of Dark Horse of the Space Race," IAF Risk," in Final Pr0c¢¢dings of the Solar Paper SD-2, October 1968. Power Satellite Program Review, U.S. Department of Energy, Conf-800491, 29) Frey, T., "Sea Launch and Recovery Contract Number FG05-79ER 10116, July (SEALAR): Responsive and Affordable 1980. Access To Space," AIAA Paper 92- 1361, March 1992. 21) Rosen, S. and Sloan, J., "Electric Orbit Transfer Vehicle: A Military Perspective," 30) Weldon, V., and Fink, L., "Near Term AIAA 89-2496, July 1989. Two Stage to Orbit Fully Reusable, Horizontal Takeoff/Landing Launch 22) "Solar Power From Satellites," Hearings Vehicle," IAF Paper 91-194, October before the Subcommittee on Aerospace 1991. Technology and National Needs, Committee on Aeronautical and Space Sciences, U.S. 31) Nadell, S., et al., "Mission and Sizing Senate, 94th Congress, U.S. Government Analysis for the Beta II Two-Stage-To- Printing Office, 1976. Orbit Vehicle," AIAA 92-1264, February 1992. 23) Landis, G. and Perino, M., "Lunar Production of Solar Cells - A Near Term 32) Stanley, D., Wilhite, A., Englund, W., Product for a Lunar Industrial Facility," in and Laube, J., "Comparison of Single- Space Manufacturing 7: Space Resources to Stage and Two-Stage Airbreathing _[mprove Life On Earth, Proceedings of the Launch Vehicles," Journal of Spacecraft

17 andRockets,Volume 29,Number5, September-October1992. 33) Plencner,R., "Overview of theBetaII Two Stageto OrbitVehicleDesign,"AIAA Paper 91-3175,September1991. 34) Palaszewski,B., "LaunchVehicle PerformanceUsingMetallizedPropellants," AIAA Paper91-2050,June1991. 35) Palaszewski,B., "Atomic HydrogenAs A LaunchVehiclePropeUant,"AIAA Paper90- 0715,January1990. 36) Hunter, J., andHyde, R., "A Light Gas GunSystemfor LaunchingBuilding Material Into Low EarthOrbit," AIAA Paper89- 2439,July 1989.

18 Overall Development Plan

Large-Scale Precommercial Solar Power Full Scale .¢_Space to Earth Satellite Flight Technology

'",_v_olar Power Large Scale Full Commercial Satellite Flight Technology Implementation

Terrestrial Integrated Testing Systems Engineering Technologies Scale-up

Ground pa_ce to Spe_ace Commercial Technologies • beam pointing • system Demonstration • receiving efficiency Space • conversion • deployable Cost Estimate Technology • storage solar arrays • distribution of Large Scale • collection System • conversion _eam Effects on Beam Effects • beaming • atmosphere • receiving on • biota • comrnunicatic Beam Effects on Cost Estimate -electronics Cost Estimate of Integrated -astronauts of Ground System •obsen/ations Technologies

Preliminary Cost Estimates of Technologies

Genet I Research ( Life 3ciences ) Preliminary study of beam on environment Long term effects of beam on environment

Public awareness Public education Public acceptance I I ! I I I

Figure 1. Phased Approach for Space Power Development

19 A ¢_ 250 e-- | H Best Estimate

Bars Show the Range I,= of Estimates SPS 200 - ,p= Fusion o O m O

s... O Centralized 150 - Ground Solar C J_ |

t_ G) ¢2. 100 - W m m Advanced tl =E Light Water i Reactor i I" _---I

,I-I i ¢0 Coal I I O 50 -- I---I

>,

=l

=m I-- ¢J 0 m IJJ Projected Prices of Alternative Energy Sources for the Year 2000 (1978 Dollars, Ref. 20)

Figure 2. cost Cornt_ison of Power Systems

20 RECURRING Ist 5 G_e SPS TRAN_PORTATIO_ COSTS R,_'D COSTS PROOUCTIOtl COSTS

/ .<

'T'V

Figure 3. Space Transportation Costs for Solar Power Satellites

21 COST CONSTRA£NT

HowM_ PowTwa, __

[Orbit Selection

POWER COLLECTION, CONVERSION AND DISTRIBUTION REQUIREMENTS

Power Generation Method Power Transm_sion Power Conversion Aperture Product

SPACECRAFT DESIGN

A

[ OPERATIONSo_.o.._ [ [TRANSPORTATIONs_ __

COST CONSTRAINT

Figure 4. Group Interactions and Driving Requirements For SSPP Design Project

22 Demo 1: Demo2: Demo3: Demo4: 1992 1996 2005 2012 I H H H I / Start of_ SSPP:J / "_,aunc.o,1 2036 _ First SPS:J \ \ R&D for New Development of Space Transportation Advanced STS: Technologies: 2006 1992

Figure 5. Overall Development Schedule

23 Form Approved REPORT DOCUMENTATION PAGE OMBNo.0704-0188

Public reporting burden for this collection of information Is estimated to average 1 hour per response,' Including the time fo_ reviewing Inst_6t;_-_,, searching existing data sources,

collection of Information, including suggestions for reducing this ouroen, to Wasnlngton rreaoquanere _ervlces, ulreccoram mr imonnacon Uperd_ arm r,upu_, ,,=.= ,J,, =._u_, Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Pape_rk Reduction Pro_ect (0704-0188). Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DAT.-,_ COVERED June 1993 Technical Memorandum ,= 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Space Transportation Ahematives for Large Space Programs: The International Space University Summer Session- 1992 WU-506--42-72 ¢ AUTHOR(S)

Bryan A. Palaszewski

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER National Aeronautics and Space Administration Lewis Research Center E-7999 Cleveland, Ohio 44135-319I

10. SPONSORING/MONITORING 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) AGENCY REPORT NUMBER

National Aeronautics and Space Administration NASA TM- 106271 Washington, D.C. 20546-0001 AIAA-93-2278

1i. SUPPLEMENTARY NOTES

Prepared for the 29th Joint Propulsion Conference and Exhibit cosponsored by the AIAA, SAE, ASME, and ASEE, Monterey, California, June 28-30, 1993. Responsible person, Bryan A. Palaszewski, (216) 977-7493.

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DiSTRIBUTiON CODE

Unclassified - Unlimited Subject Categories 16 and 20

13. ABSTRACT (Maximum 200 words)

In 1992, the International Space University (ISU) held its Summer Session in Kitakyushu, Japan. This paper summarizes and expands upon some aspects of space solar power and space transportation that were considered during that session. The issues discussed in this paper are the result of a 10-week study by the Space Solar Power Program design project members and the Space Transportation Group to investigate new paradigms in space propulsion and how those paradigms might reduce the costs for large space programs. The program plan was to place a series of power satellites in Earth orbit. Several designs were studied where many kW, MW or GW of power would be transmitted to Earth or to other spacecraft in orbit. During the summer session, a space solar power system was also detailed and analyzed. A high-cost space transportation program is potentially the most crippling barrier to such a space power program. At ISU, the focus of the study was to foster and develop some of the new paradigms that may eliminate the barriers to low cost for space exploration and exploitation. Many international and technical aspects of a large multinational program were studied. Environmental safety, space construction and maintenance, legal and policy issues of frequency allocation, technology II= transfer and control and many other areas were addressed. Over 120 students from 29 countries participated in this summer session. The results discussed in this paper, therefore, represent the efforts of many nations.

i lS. NUMBI=R OF PAGES 14. sUBJECT TERMS 24 Space transportation; Rocket propulsion; Launch vehicles; Metal propellants 16. PRICE CODE A03 20. UMITATION OF AB31nACT 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION OF ABSTRACT OF REPORT OF THIS PAGE Unclassified Unclassified Unclassified Standard Fo_- 298 (Rev. 2-89) NSN 7540-01-280-5500 Prescribed by ANSI Std. 7-39-18 298-102