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Space TransportationAlternatjves for LargeSpace Programs: The International SpaceUniversity SummerSession- !992

Bryan A. PalaszewskiLewis 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-I0811TRANSPORTATION ALTERNATIVES FOR

LARGE SPACE PROGRAMS: THE

INTERNATIONAL SPACE UNIVERSITY Unclas , .:

SUMMER SESSION t I992 (NASA) 25 p _,:...._.,

PTG3/16 0175557

https://ntrs.nasa.gov/search.jsp?R=19940006356 2020-03-21T13:26:42+00:00Z

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Space Transportation Alternatives for Large Space Programs:The Intemational Space University Summer Session - 1992

Bryan Palaszewski*National Aeronautics and Space Administration

Lewis Research CenterCleveland, OH

Abstract.

In 1992, the International Space University CAN(ISU) held its Summer Session in Kitakyushu, DOE

Japan. This paper summarizes and expands CNESupon some aspects of space solar power andspace transportation that were considered during EOTVthat session. The issues discussed in this paperare the result of a 10-week study by the Space ESASolar Power Program design project members ETOand the Space Transportation Group to EVAinvestigate new paradigms in space propulsion FRAand how those paradigms might reduce the costs FYfor large space programs. The program plan was GEOto place a series of power satellites in Earth orbit. GPSSeveral designs were Studied Where rnany kW, GWMW or GW of power would be transmit_d to HEarth or to other spacecraft in orbit. During the HLLVsummer session, a space solar power system was ISASalso detailed and analyzed. A high-cost spacetransportation program is potentially the most ISU

crippling barrier to such a space power program. IUSAt ISU, the focus of the study was to foster and Ispdevelop some of the new paradigms that may JETROeliminate the barriers to low cost for space

exploration and exploitation. Many international JPLand technical aspects of a large multinational JPNprogram were studied. Environmental safety, kWspace construction and maintenance, legal and LSSpolicy issues of frequency allocation, technology METStransfer and control and many other areas wereaddressed. Over 120 students from 29 countries

participated in this summer session. The resultsdiscussed in this paper, therefore, represent the

efforts of many nations.

* AIAA Member,

MILAX

MTNIX

Nomenclature

Canada

Department of EnergyCentre Nationale d'Etudes

SpatialeElectric Orbital Transfer

Vehicle

European Space AgencyEarth to Orbit

Extravehicular ActivityFranceFiscal Year

Geostationary Earth OrbitGlobal Positioning SystemGigawattAtomic HydrogenHeavy Lift Launch VehicleThe Institute of Space andAstronautical Science

International Space UniversityInertial Upper StageSpecific Impulse

Japan External TradeOrganizationJet Propulsion LaboratoryJapanKilowatt

Large Space StructuresMicrowave Energy Trans-mission in SpaceMicrowave Lifted Airplane

ExperimentMicrowave Ionosphere Non-

linear Interaction Experiment

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

MPD

MSS

MW

NASA

NLSOTVPLVPOTV

SDISEE

SFUSHARP

SPS

SSPP

SSTO

STS

TSTO

USA

Ministry of internationalTrade and industryMagneto Plasma DynamicMaster in Space StudiesMegawattNational Aeronautics and

Space AdministrationNational Launch SystemOrbital Transfer VehiclePersonnel Launch VehiclePersonnel Orbital TransferVehicle

Strategic Defense InitiativeSociete des Electriciens et desElectroniciens

Space Flyer UnitStationary High AltitudeRelay PlatformSolar Power Satellite

Space Solar Power ProgramSingle Stage to Orbit

Space Transportation SystemTwo Stage to OrbitUnited States of America

IntrogI¢ction

Space power has been studied in the past as analternative to terrestrial power systems (Refs. 1,2, 3, 4, 5). Its attractiveness lies in the thoughtthat because energy is produced in space, thethermal and material pollution of the Earth can besubstantially reduced. Also, because thesepower stations are in space, there is thepotentialfor continuous power. With no cloud cover,storms or other weather to obscure the solar

radiation, power can theoretically be generated 24hours a day and transmitted as it is made. Thisseductive concept becomes more attractive if thecosts of all of the required technologies toassemble and maintain it are small compared tocompeting terrestrial power sources.

Many past studies of space power have madeboth realistic and optimistic assumptions of thecosts of the power generation, of maintenance,and of transportation technologies. In the mostrealistic and near-term cases, space power canprovide specific benefits for a restricted set ofusers in space and on the ground. In its most

optimistic incarnations, it can provide almostunlimited power for all of the world'sindustries. Finding where the truth lies willrequire more thoughtful consideration.

Space Solar Power_Backgroundand History_

During the early 1960's, several researchersconsidered the possibility of collectingenergy from the Sun and transmitting it to theEarth. Peter Glaser (Ref. 6) was the first to

propose and patent the idea of beaming solarenergy from a satellite to Earth. Some of thefirst experiments with ground-based beamedenergy were conducted with a small-scalehelicopter (Ref. 7). JPL and NASAconducted other larger scale demonstrationsof the technology for power beaming in theatmosphere. Amongst these are the world'shighest power level transmitted bymicrowave beam through the atmosphere(Refs. 8 and 9). A total of 30.4-kW ofbeamed power was received at the NASA-JPL Deep Space Network Station inGoldstone, California. An array of lightswere illuminated from a distance of 1540meters.

The NASA-DOE study (Refs. 2, 4)investigated large scale 5-GW power levelsolar power satellites. Detailed conceptualdesigns of all of the components weredeveloped over a period of 5 years from1976-1980. Dozens of these satellites would

be needed to power the USA or any otherlarge industrial user nation. All of thesatellites would operate in GeostationaryEarth orbit (GEO). A typical size for these

rectangularly-shaped satellites is 5 by 10 km.This large surface is almost entirely coveredwith solar cells. As the energy is produced,it is transmitted to a ground station with amicrowave beam. The transmitting antennadiameter is 1 km. The frequency of themicrowave transmission would be 2.45

GHz. On the ground, a receiving antenna, orrectenna, would intercept the beam andground processing stations would convert theenergy into usable power for the mainelectricity grid.

While ambitious,this ideafor generatingpowerfor Earthisexpensive.Theinitial investmentcostsbasedon theNASA/DOE studyestimatedtheinvestmentcostsoverthefirst 30yearsto bemorethan2 trillion dollars(FY 1992dollars,Ref. 1). Thepaybackfor thesystembegan20 to40yearsafterthefirst operationalpowersatellitelaunch. Evenwith aninternationalprogram,it isunclearthat SpaceSolarPowerwill beattractivein a largescaleapplication. ISU thereforeembarkedon thetaskof finding amorecost-effectivemethodorpathto developthetechnologiesfor SSPP.

As partof the199210-weekInternationalSpaceUniversitySummerSession,severalalternativespacesolarpowersystemswerestudied.Spacepowersystemsfor ground-basedandspace-basedpowerusagewereenvisioned.During thisstudy,manyof theassumptionsof pastanalyseswerereviewedandcritiqued. Thelargedriversin costwerereviewedanda seriesofdemonstrationprojectswereconceivedto showthepossiblebenefitsof spacepowerfor ground-baseduse.Thecostreviewhelpedfocusthedirectionof ourstudygroupsandallowedustolist importantdirectionsfor futurestudies.Thedemonstrationprojectsshowedthatthecostsofspacesystemsarenot low. Futuresystemsmustestablishnewparadigmsin spaceflight to reducethesecostsif spacepoweris to becomeaviableenergyalternative.

Thecostof spaceaccesswasoneof themajorcostfactorsin thedevelopmentandoperationsofspacepowersystems.Spacetransportationcostshavehistoricallybeenamajorinfluenceonspaceprogramcosts(Refs. 1-5). Largespaceprograms,especially,will usespacetransportationsystemsextensivelyandfrequently. To reducethecostof thesesystems,newmethodsandparadigmswill berequiredtoremakethefaceof space.Laterin thepaper,anumberof spaceaccessmethodswill bediscussed.

To fully assessthespacetransportationinfluencesoncostsandotheraspectsof theprogram,abroadsystemsperspectiveis needed.Thisview will uncovertheeffectof otherpartsofthesystemaswell asthe influenceof thelegal

andinternationalagreements.Thisinterdisciplinaryperspectiveis wheretheIntemationalSpaceUniversity (ISU) canplayanimportanteducationalandtechnicalrole.

Wha_ Is the International

Space University2

The ISU is a major venue for students fromall over the world to discuss and assess

future space missions and applications. Notonly does ISU provide a fertile ground forthe review of space projects, but it allowspersons from all over the world to meet andattempt to open the floodgates of internationalcommunication between space enthusiasts.

Each summer since 1988, ISU has

sponsored a 10-week session in a differentcity around the world. Cambridge,Massachusetts (USA), Strasbourg (FRA),Toronto (CAN), Toulouse (FRA), andKitakyushu (JPN) have been past ISU sites.These sessions are a very intense time ofeducation and commitment to a designproject. To complement the stresses of theacademic workload, there are many culturaland social activities to promote a cooperativeatmosphere amongst the students and thefaculty. In Kitakyushu, the ISU communitywas even invited to perform traditionalJapanese dances in a local festival.

The summer sessions will ultimately becomplemented with a permanent campus sitewhere ISU will offer a Master in SpaceStudies (MSS) degree. This campus will bein Strasbourg, FRA. Additional affiliatecampuses will also be chosen to furthercontinue and promote ISU research andeducation in a large number of additionalcities. These campuses will not offeracademic degrees, but their work will fosterstudents' international space cooperation.

Departments, Lccture_,and Workshops

Nine departments are part of the ISU lectureseries during a summer session: Architecture,Business and Management, Engineering,

Life Sciences,PhysicalSciences,PolicyandLaw,ResourcesandManufacturing,SatelliteApplications,andHumanities.Five weeksofcorelecturesalloweachdepartmenttocoverthebasicspace-relatedtopicsthatarepartof thedesignproject. Otherspeciallecturesandseminarsarealsoprovidedbyvariousluminariesin the international space community. Theselecturers include astronauts and cosmonauts,

directors of various nations' space programs,artists, historians, entrepreneurs, and ISUalumni. Also, researchers from the local area are

invited to perform joint experiments with thestudents as part of the departmental workshops.For example, the Shimizu Corporation provideda domed area where a Mars surface drill was

simulated and used by engineers from TheInstitute of Space and Astronautical Science(ISAS), Nishimatsu Construction Company, andNagoya University to investigate different boringtechniques (Ref. 10). Various consistencies ofsimulated Martian soil and different drill

techniques were evaluated over a period of oneweek using ISU student volunteers to conductthe experiments.

Design Projects

During the summer session, there are technical

design projects that involve all of the students.After absorbing the core lecture materials, andhaving many hours of additional lectures on howto approach our design projects, students areorganized into task groups. During the firstphase of the design project, our groups wereasked to identify important questions to beanswered during the second phase of the project.

Several groups were formed to address the issuesof economics-business, demonstration-specificproblems, political-social-legal, technical, andenvironmental-safety. As an example, Table I

lists the major issues discussed by theenvironmental-safety group. Each grouprepresented numerous disciplines which yielded

new perspectives on many space issues. Thisinterdisciplinary aspect is one of the majorstrengths of ISU.

In the SSPP design project, the ISU internationalperspective gave new insights into almost anyspace issue. Our space transportationgroup was

composed of students from 5 countries:France, Germany, Japan, Sweden, andUSA. Though not direct members of the

group, representatives from China andRussia also provided their perspectives onspace launchers. All agreed that launch costsare a major stumbling block to success andcost-effectiveness in large programs.

Table I

Environmental/Safety Group Issuesfor SSPP

Living OrganismsHuman:

Effect of Microwaves

Political, Social Influence

HeatingOther:

Effects on Flora, FaunaProtection Needs

Safety Demo

AtmosphereMicrowave-Atmosphere Interactions

Safety DemoGlobal Warming

RectennaLocal Environment EffectsRectenna Placement

Hydrology, Geology, Aesthetics

Launch SystemsEnvironmental Damage (Atmosphere,Land)

Space DebrisDemo of Environmental Impacts

Why the ISU Space Solar PowerProgram?

One function of the SSPP was to develop acost-effective incremental program for thedemonstration of space power. This step-by-step approach was proposed by Peter Glaser(Ref. 11) and embraced by the ISU. Basedon the initial solar power satellite cost

estimates,it is notclearthatonenationcouldaffordsucha system.An incrementalprogrammightallow lesscostlydemonstrationsandgeneratesufficientconfidencefor internationalpartnersto becomeinvestors. By attackingthesmallest,simplestpiecesof theproblemfirst, thesucceedingstepswouldhopefullybecomemucheasier.Also, thevisibility of thedemonstrationswouldfoster publicacceptanceof beamedspacepower.

Japanandothernationshaveembracedthisphasedapproach(Ref. 12). Severaldesignstudieshavebeeninitiated(Ref. 12):SPS2000,SpaceFlyerUnit (SFU)EnergyMissionStudyandMicrowaveGardenProject. Also, small-scaleexperimentshavebeenconducted:theMicrowaveLifted AirplaneExperiment(MILAX), MicrowaveIonosphereNonlinearInteractionExperiment(MINIX), andMicrowaveEnergyTransmissionin Space(METS). Thelattertwo projectswerelaunchedonsuborbitalsoundingrockets.The soundingrocketexperimentsusedhigh-densitymicro-electronicsandhaveshownthepotentialfor lightweightpowergenerationandheatrejection.TheJapaneseMETSexperiment,launchedin early1993,transmitted1kW of electricpowerfrom asoundingrocketmothervehicleto asmallerdaughterfreeflyer releasedfrom themotherrocket. This experimentwasconductedincooperationwith theUSA's Centerfor SpacePoweratTexasA&M UniversityandtheNASALewis Research Center.

Canada and Europe have also conducted or areplanning experiments that show their increasinginterest in beamed power (Ref. 13). TheStationary High Altitude Relay Platform(SHARP) was conducted by Canada toinvestigate long duration airplane surveillanceand communications (Ref. 14). The European

Space Agency (ESA) has held severalinternational conferences on space power (Refs.15, 16, 17).

The Design project: A PhasedApproach

Using the phased approach (Refs. 1, 11), theSSPP team attempted to identify the best

experiments to demonstrate the feasibility ofdiffering aspects of power beaming andreception. Figure 1 shows the SSPP

approach and development plan (Ref. 1).There are five major phases: space to space,terrestrial testing, space to Earth, large-scale

precommercial satellites, and solar powersatellites. In each of these phases, Earth-

bound experiments with point-to-pointtransmission and other environmental impactstudies and/or research would be conducted

prior to any large space demonstrations.

Small Space ExNriments

Small experiments or demonstrations wereproposed as the vehicle for popularizingspace power. One idea even suggested usinga roll-out rectenna or "magic carpel' (Ref.18) that would intercept a microwave beamfrom a passing satellite. This demonstration,though appearing somewhat whimsical,could allow power to be available in remoteareas over longer periods of time. A follow-

on program might provide more-continuouspower to developing nations and remoteexploration sites (in equatorial jungles, etc.).

Lgw-(_ost Demonstrators

During the study, several demonstrationprojects were conceived to provide some data

on power transmission and integration of thespacecraft, the solar power generation, andthe microwave power-beaming technologies.A wide range of ideas were proposed,including a transportation experiment with

electric propulsion.

Cost constraints were given for two of thedemonstration missions: 80 and 800 million

dollars (FY 1992). In the 80-million dollarmission, the Russian Mir space station androbotic Progress tanker vehicle combinationwas used. This experiment allowed ademonstration of space-to-space transmission

and reception. Power was planned to betransmitted from the Mir to the Progress andthe power level of the experiment was to be amaximum of 10 kW for multiple 1-hourdurations. The use of existing Russian

spacecraftallowedasignificantcostsavingsoveracompletelynewvehicledesign.Forthe800-million-dollarexperiment,alargespacecraftinsun-synchronousorbit with a 1000-kmaltitudewasassumedfor space-to-Earthpower-beamingexperiments.At 1000km, thesatellitewoulddeliver50kW to a 1-km2rectenna.Thoughthegroundstationvisibility timeatthis low altitudewasonly 5 percentof anorbitalperiod,theexperimentplanwasto demonstratethatbeamingto equatoriallocationswaspreferrableto theoriginally-selectedAntarcticregionsdueto higherorbitalvisibility andthelower lossesattheequator.Themajorlossesatthepolarareasaredueto blowing snowandice inadvertentlycoveringtherectennas.

Two additionalexperimentswerealsodesigned:onefor under8million andonefor 2-3billiondollars. In the8-million-dollarexperiment,asmallsatellitewouldinterceptmicrowavetransmissionsfrom the300-mdiameterradiotelescopein Arecibo,PuertoRico. ThesatellitewouldbelaunchedaboardanArianerocketasa auxiliarypayloadandplacedintoapolarorbit. Weighinglessthan150kg, thesatellitewoulduseaninflatablerectennaandinterceptasmallfractionof thebeamedenergyfrom Arecibo. Themore-costlymultibilliondollarexperimentsbeamedenergyfrom spacetoEarthandrequiredaminimumof two RussianEnergialaunchesandseveralUSA STSflights.Thesevehicleswouldhavea 1-MW solar-arraypowerlevel, operateatafinal altitudeof 20,000to 36,000km, andbeampowerto near-equatorialgroundrectennas.A rangeof differentsatelliteswereanalyzedto assesstheassemblyrequirementsandthecostsfor severalhigh-powerprecursorpowersatellites.Thoughthecostof thissystemwasseveralbillion dollars,thesesatellitesarerelativelylow-costversionofthehigh-power5-GWpowersatellitesproposedaspartof afull-scalesolarpowersatelliteconstellation.

Theresultsof thesedesignexampleswerelong,extendedexercisesfor thestudentsin thedifficultiesandintricaciesof planningspaceprojects. All of thestudentslearnedanimportantlesson;theywereimpressedwith howsmallthereturnwasfor theinvestedcost.

Qther SSPP Issues

The specific issues that were studied alsoincluded many of the international and

technical aspects of a large multinationalprogram. Environmental safety, spaceconstruction and maintenance, legal and

policy issues of frequency allocation,technology transfer and control, costs andmany other areas Were addressed. Tables 11and HI show the specific groups that wereformed to address these issues and the major

issues, respectively. Some of the importantresults are presented in the next sections.

Table I/

Task Groups of the Space Solar PowerProgram

• Assumptions, Intentions, andExtemal Relations

• Scheduling• Legal and International Relations• Business Planning• Environment and Safety• Space Transportation• Manufacturing, Construction,

and Operations• Spacecraft• Power Collection, Conversion,

and Distribution• Technical Trade Identification

Energy Analysis. To justify theconsideration of space power, and to

quantify the need for future power systems, apreliminary energy analysis was conducted.The predicted energy needs of the world andthe supplies of current energy resources werecompared. Current terrestrial energy sourcesconsidered in this analysis are listed in TableIV. Several future energy consumptionscenarios were considered: low, medium,

and high growth. In all of these cases, thetotal demand for energy will increase, withthe low model increasing by 150 percent (2.5times the current rate) and the high model

TableffICritical Issuesfor SSPP(Ref. 1)

Desi[n ProiectGroupSpacetransportation

Spacecraft

Powercollection,conversion,anddistributionEnvironment,physicalandlifesciencesSocialandpolitical

Manufacturingandassembly

Businessandother

Issuereductionof ETOlaunchcostsattitude,orbit, andvibrationcontrolofLSS

efficientradiatorsmoreefficientpowerconversionsystems

determine beameffects on biota and

Earth's atmospherecreate intemational

management groupfor space solar powerproject

ensure security ofsatellite and beam

develop advancedassembly techniquesin robotics and EVA

achieve business

feasibility for

program

search for long-termfunding

achieve scientific

acceptance

public awareness

having a 400-percent increase (5 times the currentrate).

Alternative Energy Sources. A widerange of energy sources were considered ascompetitors with space power. The potentialalternative energy sources are shown in Table IV.The current energy sources of coal, oil and gas

Table IV

Current, Potential and Speculative PowerSources

Current:Fossil Fuels: Oil, Gas, CoalNuclear Fission

Potential:FusionGeothermalBiomassWindSolar - Thermal and PhotovoltaicOcean - Thermal, Tides, and CurrentsExtraterrestrial Resources

Speculative:Black Holes

CrystalsHuman: Bicycles, TreadmillsVolcanos

Gravity WavesAntimatterAlternate Universes

Tachyons

provide 90 percent of the world's energy(Ref. 19). These sources are destined for

depletion in the early part of the 22ndCentury. The other 10 percent of the energyis produced by nuclear fission, hydroelectricand other technologies, such as solar andwind.

Alternative energy sources were alsoidentified using a brainstorming method.Many alternative technologies are availablefor sustaining the Earth's needs. The timescale for the depletion of the naturalresources may be a driver for the logicalprogression of space power from its currentformative stages to its genesis as a majorpower supply. Some of the unusual andstriking altematives that were considered

..... during the brainstorming sessions were blackholes and crystals.

A preliminarycomparisonof thecostsof powersystemsis presentedin Figure2 (Ref. 20). It isclearthatthebest-estimatecostof space-basedpoweris veryhigh:2 to 6 timesthatof acurrentground-basedalternative.Thoughthisanalysisshowsthatspacepowermaybeunattractivemthenearterm,theanalysisdoesnot includethecostof environmentalimpactandtheneedforincreasingenergydemandwith thedepletionofcurrently-availablefossilfuels. Oncethesecostsareincluded,thepicturemaydramaticallychange.Thefinal analysiswill dependupontheurgencyof theneedfor alternativepower,thetechnologyreadinessof thesealternatives,andthepolitical will to investin futurepowerdirections.

Markets. Another direction our studyaddressed was the market for power from space.This included not only the space applications butthe terrestrial possibilities as well. Table V liststhe market opportunities that were found for

Table V

Markets for Space Power:Near, Mid and Far Term

Space -GEO and LEO Satellites

Space StationsElectric Propulsion

Earth-Remote Sites:

Power RelayPeak Power

Primary Power

space power. The analysis looked into near-,mid-, and far-term options for space and Earthmarkets. Peak power and electric propulsionwere the two areas where space power mightmake a large contribution. Peak power isneeded at times during the day when industrial orother commercial power consumption areparticularly demanding. Because the cost of peakpower level is at least twice as cosily relative to

base-load power, a low-cost space powersystem might provide benefits.

Electric propulsion systems have beeninvestigated for orbital transfer missions andespecially for deployment of space powersatellites. Electric propulsion is alreadyacknowledged as a powerful force inreducing the costs of space transportation(Refs. 2, 4, 21). Using beamed energy with

electric propulsion, in the proper form andmanner, might further reduce the cost of thistransportation option and the overall SSPP.This concept involves bootstrapping the useof the power satellite: using it for a traditionalpower demand as well as powering theElectric Orbital Transfer Vehicles (EOTV)

that are lifting their brethren into their finalorbits. Though this may provide a savingsfor the overall transportation system, there isalso the added complication of potentiallybeaming energy to multiple targets andhanding off the EOTV to other satellites asthey fall out of the line of sight with theirorbital power stations.

SSPP Space TransportationIssues

After reviewing the existing literature onspace power satellite designs, the costs of thediffering systems were identified andassessed. Space transportation was found todominate the cost of advanced power

systems in space. In past studies of thesesolar power satellites, up to 40 percent of theprogram cost was directly related to spacetransportation; this is shown in Figure 3(Ref. 1). The transportation system costs forsolar power satellites were 40 to 45 percentof the total research, technology anddevelopment costs. These costs include theHeavy Lift Launch Vehicle (HLLV), thechemical Orbital Transfer Vehicles (OTV)

and EOTVs. Thus, in the planning of futurespace programs, space transportation willplay a critical role. This paper will addressalternatives to reduce the cost of space flightand the options for various programs'transportation needs. Innovativetechnologies and new architectures are

availableto potentiallyreducethesecostsandmakeall of spaceflight moreaffordable.

TheSpaceTransportationGroupwasformedtoassessnewwaysof conductingspacemissionsthatwouldreducelaunchandothertransportationcosts. Figure4 showsthedriving requirementsthatwereidentifiedin theoveralldevelopmentplanfor spacesolarpower. Theseplanningactivitiesidentifiedtheinteractionsbetweennotonly ourdifferentspacesystemareasbutalsotheinternationalandpoliticalforcesthatareacriticalpartof this largespaceprogram. Theinteractionsof theSpaceTransportationGroupwith theothergroupsin thespacesolarpowerprogramarealsodepictedin Figure4. Theseinteractionsincludetheselectionof theappropriatelaunchvehiclesfor demonstrationmissions,theidentificationof marketsfor spacetransportationrelatedto spacepower,thediscussionof thepayloadaccommodationof thedifferingsatellitepayloadsandthereviewofissuesrelatedto themostpromisingtechnologiesthatmeritfurtheranalysis.

NASA/DQE Study: Transportation

In the studies conducted in the late 1970's, the

elements of space transportation were dividedinto Earth to Orbit, orbital transfer and lunar

transportation. Initially, the transportationincluded only an Earth-centered system. The

primary elements were heavy lift launch vehicleswith electric propulsion and chemical propulsionOTVs. A lunar transportation system was placedin the systems analysis after realizing that Earthtransportation costs were too high to make spacepower economical. Lunar materials wereprocessed into propellants and building materialsto construct the solar power satellites.Production factories would be transported to theMoon and the initial cost for emplacing themwould have to be paid. After these factories paidfor themselves and lunar materials were used in

lieu of those strictly from Earth, the cost of thesatellite systems dropped dramatically. Anumber of transportation vehicles had to beadded to the overall system. These included amass driver, mass catcher, lunar base, oxygenand construction material production plants onthe lunar surface and/or in space, and the

traditional lunar transfer vehicles and landers

for personnel and equipment transport.Though the apparent complexity of thesystem increases, producing materials on themoon significantly reduced the Earth-launched mass. Less mass is needed because

the energy to transport the materials from thelunar gravity well to GEO was less than thatfrom Earth to GEO. However, even with the

use of lunar materials, the payoff for the

space power systems is typically manydecades in the future (Refs. 1, 22).

Combining and using innovative propulsionconcepts might further reduce the time forSSPP to pay for itself. We thereforeembarked to identify new ways to make

space transportation cheaper and thereforemake SSPP more attractive.

New Paradigms

A paradigm is a model of how things shouldbe done. New paradigms for spacetransportation include a number oftechnologies and vehicle concepts that whentaken together, may reduce the costs of spaceaccess. The technologies and vehicle typesthat appeared most promising for costreductions were cataloged. A method ofselecting the technologies and vehicle

concepts for the various mission types wasalso developed.

Transportation Costs

The costs of space transportation includednot only the monetary value of the vehicles,but also the "costs" of reliability,accessibility, launch environment, operabilityand vehicle resiliency. These costs mayseverely limit the viability of a space solar

power system if not addressed early in theprogram. The technologies and vehicleconcepts we reviewed were assessed basedon their ability to allow reduction in all of the

cost of space flight, not just reductions in itsdollar value. We also prepared a white paperwhich discusses these other important costsfor space transportation (Ref. 1).

9

TableVIPropulsionTechnologyandVehicleLink

To SSPPApplications

Earthto Orbit:MetallizedPropellantsHigh EnergyDensityPropellantsHigh EnergyChemical(O2/H2,etc.)SlushHydrogenGunPropulsionMassDriverLaserPropulsion• Vehicles-

TSTOSSTOHLLVPressure-FedBooster

Lunar:In-Situ PropellantsMassDrivers/ Mass Catchers

Gun PropulsionHigh Energy Chemical (O2/HE, etc.)

Aerobraking/Aerocapture• Vehicles -

Lunar Transfer VehicleLunar Excursion Vehicle

Orbital Transfer:

Solar and Nuclear Electric Propulsion

Beamed Energy Electric PropulsionNuclear Thermal PropulsionHigh Energy Chemical (O2/H2, etc.)

Aerobraking• Vehicles -

Light Weight Upper Stage

Propulsion-Related TechnologiesLight Weight StructuresHigh-Temperature Materials• Vehicles -

All of the Options Above

Technologies

The Space Transportation Group compiled a listof future technologies that could potentiallyreduce the cost of access to orbit. Table VI is a

compilation of the technologies considered for

space transportation and their link to differentvehicle concepts. Many of the technologieshave been considered over the last fifty yearsand have greatly varying degrees oftechnology readiness. Several of thetechnologies were considered most attractivefor cost reductions and these will be

discussed later in the paper.

Selection Criteria. In the planning for

space solar power, there are three powerlevel ranges that were considered and theycan be thought of as directly linked to thelevel of advancement in the spacetransportation system. Table VII summarizesthe power level influences. For

Table VII

SSPP Power Influence On TransportationTechnology

Power AdvancementLevel Needed

Range

kW • New Vehicle

Technologies

MW • New Systems orArchitectures

GW • New Paradigms:Lunar transportation,Extraterrestrial resources

example, if only several kW of power wereplanned to be delivered, then relatively smallimprovements in technology would be

required. However, if large satellites of theGW power level were developed, it seemsclear based on past assessments (Ref. 5) thata new model of space transportation, a new

paradigm, would be needed. This newparadigm might entail lunar transportation -using in-situ resources to constructpropulsion systems, and the satellites

10

themselves,usingminimal Earth-derivedresources.This newsystemmight includemassdriversandhavea minimaldependenceontraditionalrocketpropulsionsystemsfor ascentfrom theMoon's surface(Ref. 5).

In-situ resources,however,donotnecessarilysolveall of thetransportationproblems.To placeall of theelementsof the lunartransportationsystemin place,theymustinitiaUybelaunchedfrom Earth. Thereis thereforea paybacktimeoverwhich themassof thelunarbaseanditstransportationsystemsareamortized.Thispaybackmaytakea decadeor more. Also,all ofthematerialsof thesolarpowersatellitemaynotbeeasilyfabricablefrom lunarresources.Thequalityof solarcell productionfrom lunarmaterialshasbeenbothsupportedandquestioned(Refs.23,24, 25). This andothercompetingparadigmsshouldthereforebeexaminedbeforeanytransportationsystemdesignis finalized.

Thedecades-longpaybackperiodalsoled ustobelievethatgovernmentsupportwill beneededtosustainsuchalongprogram.Commercialinvesmaentmaybesolicitedafterthefull-scalespacepowersystemhasbeenprovenandput intopracticaluse. Othersmaller-scaleprograms,suchastheremotesitepowerrelayor thepeakpowerapplicationmightattractearliercommercialinvestors,but it is unlikely thatinvestorsalonewill absorbtheinitial start-upcostfor spacesolarpower.

Two vehicleparadigms,theBig DumbBoosters(Ref. 26,27,28, 29)andTwo Stageto Orbit(TSTO,Refs.30, 31,32,33)aretechnologiesthatcanpotentiallyreduceSSPPcosts. Thesevehicletechnologiesreducethenumberofcomponentsandpotentiallysimplify theoperationsfor theoveralllaunchsystem.HigherdensityandhigherIsppropellanttechnologieswereamongsttheothertechnologiesconsidered(Ref.34,35). IncreaseddensityandI_pcanbeimportantfor smaller,lighter,more-compactrocketsbecausethelowerdry massof therocket,theeasierit is to achieveorbit. Thisaspectcanbecriticalfor TSTOandespeciallyfor SSTOvehicles.ThetechnologiesthatourSpaceTransportationGroupdeemedmostlikely toreducecostswerediscussedin themostdetail.

Theimportantresultsof this transportationtechnologysurveyarediscussedin thenextsections.

Big D0mb Booster. This launchtechnology was considered in the early1960's as a method of placing large payloadsinto orbit. Several different types of engine

technologies were considered but one thatwas most attractive was the pressure-fedbooster. Because this rocket used no high-

pressure turbomachinery, it is perceived as avery simple vehicle. With the pressure-fedbooster, propellants are fed to the engineswith only the pressure from the propellanttanks. The tankage pressures for this

booster are typically very high: 300-500 psia.This is in contrast to the low-pressure, 50-

psia, thin-walled tankage designs that aretypical of flight systems like the SpaceShuttle or Ariane. Versions of the pressure-

fed booster have been proposed in its mostambitious form in the Sea Dragon (Refs. 27,

28) and most recently in the SEA LaunchAnd Recovery (SEALAR) concept (Ref.29).

The Sea Dragon (Ref. 27) was the fh-st largepressure-fed booster to be studied for spacemissions. It was a two-stage rocket with a

payload to LEO of 1.1 million Ibm. Its name

was derived from its large size and the factthat it was sea launched. The Sea Dragon

was over 540 feet long, 75 feet in diameter,had a GLOW of 40-million Ibm and a liftoff

thrust of 80-million lbf. Each stage used

only a single engine to deliver its total thrustlevel. Its impressive dimensions wouldperhaps be unwieldy in a land-based launchpad but using the ocean obviates the massiveinfrastructure of a fixed launch site. Other

support facilities, such as a dock forconstruction and refurbishment are required,but the relative cost of the ocean-based dock

to the land-based launch pad favors the ocean

system (Ref. 27). Also, with the ocean-based system, nearly any size rocket can belaunched without creating a new launchfacility. The first stage was to be recoveredat sea and towed to the launch vehicle

shipyard where it would be refurbished.

11

Thevehiclealsowasdesignedto usetankagemadein shipyardsratherthanin theclean-roomenvironmentof atypical aerospacefactory.Shipyardswereconsideredbecausethesizeofthetankagewasextremelylargeandits wallswerevery thick. With the 1.1million poundsofpayloaddesign,theSeaDragonfuel tankwallthicknesswasseveralinches,amarkedcontrastto thedelicatepaper-thintankageof ourcurrentlaunchvehicles.Thelaunchvehiclestagesweredesignedfor ruggeduse,includingsearecoverywith minimal aerodynamicbraking,andthereforeaerospace-standardtolerancesandcleanroomswerenotrequired.Thecostof usingshipyard-quality fabricationtechniqueswassubstantiallybelow thecostsin themore-typicalaerospaceplantwhichfurtherreducedtheestimatedcostofthe launchsystem.

Themore-recentSEALAR programwasareusable,sea-launchedrocketthatcanplace10,000-to 140,000-Ibmpayloadsinto LEO (Ref.29). With a SEALAR rocket,manypayloadscouldbelaunchedat ahighrate,whichwasveryattractivefor potentialStrategicDefenseInitiative(SDI) applications.Subscalewaterimmersiontestsof therocketcomponentsandshipboardrocketenginef'wingswereconductedin theSEALAR program. However,dueto budgetreductions,SEALAR wasneverfullydemonstrated.Its inspiration,SeaDragon,wasperceivedassomewhatradicalandimpracticalbyNASA in the 1960'sdueto its immaturedesignandthepotentiallow reliabilityof asingleenginesystem. Their potentialto lift largepayloadsatreducedcost,however,maketheselargesea-orground-basedpressure-fedboostersstrongcandidatesfor reducinglaunchcosts.

Two Stage to Orbit. This launch vehicleuses an airbreathing first stage and accelerates asecond stage to a speed of approximately Mach 6to 10 (Ref. 30-33). The first stage is a wingedairplane. A rocket-powered second stage then

proceeds to orbit. The airbreathing stage fliesback to an airport-like landing area forrefurbishment. The second stage may be either apayload canister or a reusable flying vehicle. The

operations of this vehicle can potentially be verysimple compared to traditional rockets. It is also

a potential interim step prior to developing aSingle Stage to Orbit (SSTO) vehicle.

Turbojets and scramjets on the TSTO willproduce much lower velocities than that foran all-airbreathing SSTO. Therefore the

airbreathing technology is much more nearterm than the Mach 25 scramjets needed to goto orbit.

The TSTO appearedattractive because of the

aircraft-like operations afforded by wingedstages. Though the current Space Shuttle is awinged vehicle, it does not have any of theairplane-like operational characteristics of theTSTO. The first stage, with the large air-breathing engines, can be maintained withmany of the well-developed techniquesemployed by the military for high-speedaircraft. The Space Shuttle requires a largearmy of technicians to assess its safety aftereach flight. Hopefully, that large contingentof personnel could be pruned with the newTSTO approach.

Single Stage to Orbit. The advent ofhigh performance rocket engines and lighterweight structures may someday make theconcept of Single Stage to Orbit vehicles areality (Ref. 31). Because the vehicle onlyneeds to be reloaded with propellants andserviced, the cost of operations istheoretically reduced. Current rocket andmaterial technologies, however, make SSTO

impractical. The current technology levels

for propulsion Isp and lightweight materialscan only deliver a marginally-small payload

to Low Earth Orbit. Development of thesetechnologies may be driven by the needs ofan SSPP-type endeavor. As discussed inthe TSTO section, airbreathing SSTO is alsoan option, but the technology required is in

the development stage. The TSTO thereforeseems to be a more near-term SSPP optionfor reduced launch costs.

Guns. Gun propulsion is a way toprovide orbital velocities while leaving themain "propulsion" system on the ground.Using a high muzzle velocity gun or cannonto launch payloads is potentially attractive ifthe payload is insensitive to shock and

12

vibration (Ref.36). Thepayloadmustalsohavea systemto allow maneuveringafterthelaunchtocircularizetheorbit. A highmassfractionforpropellanttanksandotherstructuresmaynotbepossiblewith suchhighlaunchvelocitiesandaccelerations.Also, aremotesitewill haveto beselectedfor the launchof theprojectiles.Thenoisegeneratedby thefiring during launch willbe very high. An estimate of the distance tominimize the sound level to 70 dB is 2 km (Ref.36). A similar safety distance is typical for arocket launch. Many of the past studies havediscussed the mass of the projectile and ignoredthe added mass to withstand the high

accelerations during launch. Current studieshave included these factors and have shown

promising results. An SSPP using thistechnology would have to acquire and use manysmall masses and assemble them into the final

vehicle. Typically, the proposed gun launchershave payloads of 1,000 kg. Assembling thesemany small masses into a large operationalvehicle may be a significant challenge.

Electric Propul_;ion. The technology ofelectric propulsion will potentially allow greatreductions in the cost of space transportation. Itenables this through the reduction of the masslaunched into orbit, the reduction of the mass of

the propulsion system, and the reduction of thepayload capacity needed of the launch vehicle toplace a payload into orbit. All of these factorscan reduce overall program costs.

Electric propulsion differs fundamentally fromchemical propulsion in several ways: electricalpower supply, low acceleration, large flexiblestructures and low-thrust attitude control. A

large electrical power system is carried on boardthe vehicle to provide energy to electric thrusters.This electrical energy is used to ionize andaccelerate a propellant to very high speeds. This

acceleration produces a very high Isp. Because

of the high Isp, the total mass of the vehicle canbe significantly reduced over chemicalpropulsion. This is especially true for the veryhigh energy missions. The performance of anelectric OTV is strongly dependent upon the

power technology, power level and the Isp of thethrusters. For each mission type, a series of

trade studies and an optimization of powerlevel and thruster performance is thereforeneeded.

With electric propulsion, a vehicle thrust to

weight of 10 -4 to 10-6 is typical. The lowacceleration requires long thrusting times inEarth orbit or in Earth-lunar space. Anattitude control system is needed that willautonomously maintain the correct thrust

angle and attitude of the entire vehicle duringthe long orbital transfer. Also, large lightweight flexible structures are typically usedfor the solar arrays and other power systemstructures, taking advantage of the lowacceleration of the vehicle.

There are several thruster technologies that

are appropriate for OTVs. They are ion,arcjet and Magneto-Plasma-Dynamic (MPD)thrusters. Each system can use varyingpropellants and the performance is dependentupon the propellant selection. Ion propulsionwill typically use inert gas propellants, suchas xenon, krypton or argon. Arcjet thrustersmay use hydrazine, ammonia or hydrogen.For MPD thrusters the propellants may bedeuterium, hydrogen or even lithium for veryhigh efficiency engines.

By using electric propulsion, the Isp of the

upper stage propulsion system is increasedvery significantly: up to 5000 lbf-s/Ibm

versus the typical values of 300 to 450 lbt"s/Ibm for chemical propulsion. An example

of reducing the launch vehicle size is the useof solar electric ion propulsion for thedeployment of Global Positioning Satellites(GPS, Ref. 21). Over the life of the GPSsystem, the total cost savings will be manybillions of dollars. Similarly, for spacesolar power, electric propulsion offers themost efficient method of emplacing andmaintaining the satellites.

Pr0gramPlan

In addition to assessing the propulsiontechnologies and vehicle options, we alsocreated a timeline for the development of the

13

flight systems needed for a solar power satelliteprogram. Figure 5 shows a simplified scheduleand flowchart of the SSPP. Four demonstration

missions, which were discussed earlier in the

paper, are planned, each using existing boosterswith some small modifications and near-term

technology upgrades.

One critical problem with space transportationdevelopment for SSPP is the time scale that isconsidered. Over the period from 1992 to 2037,

many improvements in technology are possible.Therefore, two iterations on the design of thevehicles and the technologies are included in the

plan. Though technology infusion has movedslowly in the past twenty years, the impetus ofthe SSPP may provide the incentive to advancetransportation technology at a higher rate than hasbeen seen previously. International investments,not only from space programs but from energy-based investments, may provide the funding to

leap-frog to the next generation in technologyrather than following the typical, ponderousevolutionary path.

After the initial identification of the vehicle sizes

required for the power satellites, the vehicleselection will be made. Depending on the

satellite technology to be demonstrated, thelaunch system will have to be designed or currentvehicles and systems will be pressed into service.For example, if the demonstration were only fora small-scale power beaming demonstration,there would be no need for new technology.

Prior to 2006, the technologies that were

perceived as important in the 1992 time framewill be developed. In 2006, the reevaluation ofthe STS concepts would begin. New technicaldevelopments would hopefully allow lower cost

implementations of SSPP.

Because the time scale for SSPP development is

up to 50 years in the future, it is difficult to pointto a specific technology as the one of choice for aspecific application. Innovative solutions tomany of the technical challenges of space solarpower are possible and it is nearly impossible topredict the potential of space propulsion over afive decade span. Though the scale and directionfor SSPP is hard to predict, the need for

advanced propulsion technology is clear onlyif very high power levels are desired. In ourplanning, the low-cost demonstrationmissions occur in 1992, 1996, 2005 and

2012 (see Figure 5). The first advancedspace transportation system is available in2006. Therefore, no new launch system isavailable for the first three demonstrations.

Existing boosters such as Ariane, SpaceShuttle and Energia will be used.

For the fourth demonstration and theremainder of the SSPP, the f'trst iteration of

the new transportation system will beavailable. It is planned to have yet anothergeneration of launch vehicles completed priorto the final full-scale deployment of SSPP.

In the 30 years from 2006 to 2037, there issufficient time in the schedule to

accommodate this new vehicle's development

and operational testing. The newtransportation paradigms, if any, would beborn from this phase of the program plan.Sufficient time would be devoted to systems

analysis and technology development toassure that the new paradigms would reducecosts and make the system "better, faster,

cheaper."

Concluding Remark_s

Only by reducing the costs of spacetransportation can solar power from spacebecome feasible. With many past studies of

solar power satellites, the transportationsystem cost has been 25 to 40 percent of thetotal program cost. Even with current spaceprojects, the cost of space launch services isterribly high. Without active measures tobring down the costs of space access, theviability of any large space program is

questionable. It should also be clear thatthese "'costs" include not only dollar value ofthe booster, but also the transportationsystem reliability, accessibility, launchenvironment and the vehicle resiliency. Allof these factors can increase cost and defeat

our purposes in space. Only through theapplication of innovative technologies andstreamlined space launch operations will

14

humankindattaintheheightof perfectionandlow"cost" in spaceflight.

Therearemanyoptionsfor launchingpayloadforaspacepowersystem.In thenearterm,therearenumerouscapabilitiesto deliverlargeandsmallpayloadsto LEO andbeyond.Overthenexttenyears,therewill belittle changein thecapacitytomovesateUitessincetherearefewdevelopmentsin theplanningstagesotherthanincrementalvehiclepayloadimprovements.Beyondthetenyearhorizon,newlaunchvehicledesigns,propulsionandmaterialstechnologieshavethepotentialto makeexcitingleapsin payloaddeliveryefficiency. VehiclesusingTwo StagetoOrbit andSingleStageto Orbithavethepotentialto reduceoperationalcostsof payloadlaunches.Simplifyingtheseoperationsis amajorstumblingblock to makingouraccessto orbit affordable.

Many technologiesareavailablefor spacetransportationsystemsof thefuture. Thefinalselectionof whichtechnologiesareusedisverydependenton thetimeframeof thesolarpowersystemdevelopment.Baseduponthisreport'sdevelopmentplan, thefirst launchvehicledevelopmentsfor anylargescalepowersatelliteswould bein the2005-2010timeframe. Thef'n'stsatellitewouldbe launchedin 2035-2040.Becauseof the longtimeuntil thefirst vehicleflight, it wouldbeunwiseto selectaspecifictechnologyor setof technologiesfor thetransportationsystem.Also, thespecificarchitectureof thespacesolarpowersystemwilldeterminetherelativeimportanceof thetransportationtechnologies.If a largescalepowersystemis required,theneedfor lunarresourcesmaybecomecrucial. On theotherhand,asmallersatelliteconstellationwouldmostlikely notuseextraterrestrial-basedresources.The propulsiontechnologiesthatwouldbeusedwouldbeadvancesreflectingthepotentialofSingleStageto Orbit andotherimprovementsinpropulsiontechnologyto increasetheenergydensityof propellants(suchasmetallizedpropellantsandhigh energydensitypropellants).Light weightorhightemperaturematerialswillalsoplay avital rolein reducingthecostof spaceoperationsandspaceaccess.Only timewill tellhow ambitiousandexcitingourglobal

technologicalfuturewill bein spacetransportation.

Of themanytechnologiesthathaveexcitingpotentialfor costreduction,electricpropulsionhasaspecialandimportantaddedfeature.It cannotonly reducethetransportationcostbut thereis alsoa potentialmarketfor beamedpower. OrbitalTransferVehiclesusingelectricpropulsionpotentiallycanbemoreeffectiveusingbeamedpower.Usingaremotepowersourcereducesthemassof thetransfervehicleandimprovesitsacceleration.Thisaccelerationshortensthetrip timeandmakeselectrictransfernotonlymoremassefficientthanothercompetingpropulsiontechnologiesbutalsoreducesthevehicletrip timeovertraditionalelectricvehicles.Thebenefitof electricpropulsionfor spacetransportationandthepotentialmarketit maycreatein othertransportationsystemsmakesit especiallyattractive.Therefore,usingelectricpropulsionis oneofthehigh leverageissuesthatshouldbeconsideredin anyfuture largespacetransportationsystem.

Werecognizetheimportancethatpropulsiontechnologieshavefor thesuccessof spacesolarpowerandany largespaceprogram. Alunarbaseora Marsmissionall needverycapablepropulsion-intensivevehicles.Reducingthe"costs"of spacetransportationmaymaketheseambitiousprojectsareality.This isacrucialconsiderationfor thefutureof manyspaceprograms.Thesynergismofthetransportationtechnologiesof aspacesolarpowerprogramwith otherlargescaleprojectscanultimatelyreducethecostofaccessto spacefor all nations.Majorreductionsin the"costs"of spaceaccesswillalsomakespacetruly usefulanddesirableforcommercialventures.A largelow costspacetransportationprogram,suchastheoneforspacesolarpower,couldbetherising tidethatcarriesall spaceships.

15

Acknowledgements

I would like to acknowledge NASA for itssupport of the International Space University.Also, I'd like to thank the ISU Faculty, the SSPPDesign Team and the other members of the SpaceTransportation Group of the Space Solar PowerProgram for their significant contributions to theSummer Session Final Report. They are listedbelow:

Chistophe BardetPhillippe BertheFrederic Ferot

Stefan FoeckerspergerToshiya HanadaMario Hucteau

Yoshitsugu Kanno

Thierry Le FurAlain LouisUlf PalmnasMichael ReichertMasaharu UchiumiRichard Wills

FRANCEFRANCEFRANCEGERMANYJAPANFRANCEJAPANFRANCEFRANCESWEDENGERMANYJAPANUSA

1)

2)

3)

4)

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Program," Final Report of the SummerSession of the Intemational Space University -

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5) O'Neill, G., The High Frontier: Human

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Future," Science, Volume 162, Number3856, 1968, pp. 857-861.

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Volume 13, Part 5, 1965, pp. 225-235.

Dickinson, R., "Evaluation of a

Microwave High-Power Reception-Conversion Array for Wireless PowerTransmission," NASA CR-145625, JPL

TM-33-741, September 1, 1975.

Dickinson, R., and Brown, W.,"Radiated Microwave Power

Transmission System EfficiencyMeasurements," NASA CR- 142986,

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11) Glaser, P., "The Economic and

Commercial Development of Space,"Journal of Social Political and Economic

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Summer 1984, pp. 211-229.

12) Anon., "New Technology Japan:Special Issue - Solar Power SatelliteR&D in Japan," Japan External TradeOrganization (JETRO), Three 'T'Publications, Ltd., Japan, 1991.

13) Deschamps, L., Pignolet, G., andToussaint, M., "A European ViewRegarding Power Transmission inSpace," 1st Annual Wireless PowerTransmission Conference, Feb. 1993.

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Schlesak, J., Alden, A., and Ohno, T.,

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Record - Volume 2, 1985, pp. 960-964.

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des Electriciens et des Elecu'oniciens (SEE)

Proceedings, June 1986.

"SPS 91 - Power from Space," Societe desElectriciens et des Electroniciens (SEE)

Proceedings, August 1991.

"SPS Rio 92 - Space Power Systems and theEnvironment in the 21st Century," Societedes Electriciens et des Electroniciens (SEE)

Proceedings, June 1992.

Collins, Patrick, Foreign Research Fellow,The Institute of Space and AstronauticalScience (ISAS), Kanagawa, Japan, PersonalCommunication at ISU '92, July 1992.

Energy for Planet Earth, Scientific American,Special Issue, September 1990.

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17

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35)Palaszewski,B., "Atomic HydrogenAs ALaunchVehiclePropeUant,"AIAA Paper90-0715,January1990.

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18

Overall Development Plan

pa_ce to Spe_ace

SpaceTechnology

• collection• conversion• beaming• receiving

Beam Effectson

-electronics-astronauts•obsen/ations

PreliminaryCost Estimatesof Technologies

TerrestrialTesting

GroundTechnologies

• receiving• conversion• storage• distribution

Beam Effectson

• biota• comrnunicatic

Cost Estimateof Ground

Technologies

.¢_Space to Earth

'",_v_olar PowerSatellite

IntegratedSystems

Technologies

• beam pointing• system

efficiency• deployable

solar arrays

_eam Effects on

• atmosphere

Cost Estimateof Integrated

System

Large-ScalePrecommercial

Solar PowerSatellite

Large ScaleFlight

Technology

EngineeringScale-up

CommercialDemonstration

Cost Estimateof Large Scale

System

Full ScaleFlight

Technology

Full CommercialImplementation

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¢_

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250

200 -

150 -

100 -

50 --

0

Projected

H

Coal

Best Estimate

Bars Show the Rangeof Estimates

Fusionm

CentralizedGround Solar

Advanced

Light Water iReactor i I"_-- -I

iI

SPS

I

I---I

Prices of Alternative Energy Sources for(1978 Dollars, Ref. 20)

the Year 2000

Figure 2. cost Cornt_ison of Power Systems

20

Ist 5 G_e SPS

R,_'D COSTS PROOUCTIOtl COSTS

RECURRING

TRAN_PORTATIO_ COSTS

/ .<<v1:_e:,",\s-./_,o,;",.1........_\

'T'V

Figure 3. Space Transportation Costs for Solar Power Satellites

21

COST CONSTRA£NT

HowM_ PowTwa, __

[Orbit Selection

POWER COLLECTION, CONVERSION ANDDISTRIBUTION

REQUIREMENTS

Power Generation Method Power Transm_sion

Power Conversion Aperture Product

SPACECRAFT DESIGN

A[ o_.o.._ [ [ s_ __OPERATIONS TRANSPORTATION

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/

Start of_

SSPP:J

R&D for NewSpace Transportation

Technologies:1992

H I

/ "_,aunc.o,1_ First SPS:J

2036

\\

Development ofAdvanced STS:

2006

Figure 5. Overall Development Schedule

23

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Space Transportation Ahematives for Large Space Programs: TheInternational Space University Summer Session- 1992

¢ AUTHOR(S)

Bryan A. Palaszewski

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space AdministrationLewis Research Center

Cleveland, Ohio 44135-319I

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National Aeronautics and Space Administration

Washington, D.C. 20546-0001

WU-506--42-72

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E-7999

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NASA TM- 106271AIAA-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.

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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

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.

14. sUBJECT TERMS

Space transportation; Rocket propulsion; Launch vehicles; Metal propellants

17. SECURITY CLASSIFICATIONOF REPORT

Unclassified

NSN 7540-01-280-5500

18. SECURITY CLASSIFICATIONOF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATIONOF ABSTRACT

Unclassified

i lS. NUMBI=R OF PAGES

2416. PRICE CODE

A03

20. UMITATION OF AB31nACT

Standard Fo_- 298 (Rev. 2-89)Prescribed by ANSI Std. 7-39-18

298-102

II=