7 portion (e.g., 85 or 90 percent) of the avail,,ible energy for normal energization of the engines. The magnitude of the portion that is norinally wasted will geiaerally be determined in accordance with the p.-ak wind veloei' ies occurr,-iig at the altitude at Vnich the v-.hicle is to opcrate, as will be better uiderstood in connection witii the description of the operatioi of vehicle 32. As in the case of the veh@'.cle described in connection with the earlier fi,-Ures, th-,re will normally be other add;.tional members emdloyed in actual practice in order to support such operat-ional or "pay load" eqi-i-pment as radar, communicat:@ons transceivers and the like. The configuration of the refiecting surface of memb-,rs 33 and 34 is such as to equally divide energy of beam 14 bet@,veen the engines mounted on the vehicle 32 when such veh@cle is centered (both translationally and ingularly) with respect to th@- beam 14, as shown in r-'!G. 4. As may be seen, the positiois in which the en-,ines 36 and 33 are mounted is such as to provide respective thrusts directed upwardly and away from the center of the vehicle 32. Thus, the thrust produced by eacii of ti@c engines 36 and 38 has a major component siibstanti@,lly parallel to the direction of trarsmission of the radiofrequency energy, along with a minor component normal. tliereto and direct-,d away therefrom. By means of this construction, the vehicle 32 may be rpaintained in flight or hovering condition and may also be controlled as to attitude in the plane of the drawing sheet. As will become apparent in conpection Nvith thedescription of the operation of the apparattis of FIG. 4, it will be necessary to provide three such engines to achieve attitude control in all directions. In the operatioil of the v--hicle of FIG. 4, when the vehicle is operatin.@ in a cent--red position with respect to the beam of microwave cr@ergy 14, with the central vertical axis of the vehicle in registry with the center line of the radiated beam, a propulsive thrust is provided for either propelling the vehicle upwardly or for maintainina given altitude in opposition to gravitational forces, and the thrust comronents normal to the directio-.i of the 1- radiated beam 4 are equal in magnitude and so directed as to cancel each other. Wheii th-- vehicle 32 is moved from this desired position, as by wind forces or the like-, the veliiele is re-centered on the beam by virtu,- of the structure described. For example, if the vehicle were to suff-er translation toward the right as viewed in FIG. 4, the reflecting member 34 would lie nearer the center of the beam 14 and would therefore intercept a greater amoilint of rad;o-frequ@ency energy that would member 33. Accordingly, enpine 36 would be illuminated with more eiiergy than falls on en.-ine 38, and the oppositelydirected horizontal or lateral components of force exerted by the respective engines would result in a -iiet lateral force applied to the vehicle 32 and directed toward the left in FIG. 4. This lateral correcting force will be so applied until the vebicle is once again entered on the bp-am. A corresponding operation obtains where the vehicle 32 is displaced laterally to the left in FIG. 4. In additior, the structure of FIG. 4 provides automatic attitude correction to restore the vehicle to a desired POsition upon an unwanted angular d.@SDIacement thereof with respect to the center line of the beam 1,1, of radiated energy. For example, if the vehicli:@ 32 were to be angularly displaced in a clockwise direction about an axis perpendicular to the draw-ing sheet and passing thr0u-.h ap--x 42, the reilecting mer@- iber 33 would, as a resalt, be moved toward a position more n--arly norn,,n.1 to the d;rection of the incoming radiant energy. As a result,- th-an@,,les of incidence and reflection are correspondin.-ly increased, and the focus poiit 35 is moved toward the engin@- 38 to supply a greater level of energization ther--to. A correspond;ng decrease - in the ener.@izat-'@on of eng@ne 36 obta-"ns, and a net resultant 'Lorce is applied to the vehicle .32 about the aforementioned ax;s at apex 42 to correct the attitude of the vehicle. As is evident, a 8 similar but o-,oposit-,Iy-directed operation occurs upon a-@igul,-,r disolac--merit o-f ttie veh-icle 32 in a counter-cloel,@ wi-qe direct;oii. The iilve@it7o-i has been described above in cons-iderlble Cctail, a-,id p,-,rticulprly with reference to its applicat-lon to a snace vehicle ada_nted to be maintained at a desired alt-itlide and lateral positio@i in space@llapart relationship wi'@li. respect 'Lo the Earl,h or o'her mother pialiet. Howev-,r, it will be apparent to thos-- skilled in fiae art that 10 the inventio.1 is equally applicab'@e to vehicles adapted for movemc,.it rclative to suen mother planet, whether i-iivolving a change in altitude, latitude or longitude, or some combinaio-.i t reof, so lo@ig as a s le beam of radiait eiiergy is provided. The vehicle of FIG. 4 is 1,5 sljow@l and describ-.d as having a separate dished reflector for each I-lowever, it is evident that a single reflectin.- sart'ace of revolution may equally well be empio@,ed, along with a suitable annular collecting and distribut;ng means, as indicated in FIGS. 1 and 2. Con20 versely, t@i-. scoaratp- re-@qectors of FIG. 4 may equally well bp, e@uploycd i@'n the embodiment of FIGS. 1 and 2. Further, the embodiment of FIG. 4 is not necessarily strictly ai'Leriiative to that of the preceding figures, since the two embod-me-ii@s r!iay be conibined in a single vehicle to 25 perfo.-m 'che combined results ol each enibod-'.Ment. In addition, the invention is not lim-ited to use of any partic ar @-m ust-providing engine (except as to the requirement at it be energized by received radiant rii,- rgy), and the particular means for creating the pro30 putsive tlirust may be either a jet stream, a propoller or the like. In this connection, it should be noted that while the vehicle of the present i-tiventio@a is described as being energized solely by microwave electroinagnetic energy, the vehic'e may also include a conventional engine and 35 fuel sup@iy system for suppl.-menting the action of the n-iierowave engin-.s until such fuel supply is exhausted. Also, the @invelition is applicable to tethered air vehicles, and wh,-re the operating altitude is low, the tethering means may serve as a tra-iismission line for supplying 40 er-,er, to the vehicle without prohibitive losses. Hence t,,i-- invention is not to be considered as being limited to the Particular details given, nor to the specific application to ,vl?-ich reference has been made duriiag the descriptio@l of the apparat-,is, except ir@soiar as may be required by 45 tile scope of t@.e a-opended clain-is. What is claimed is. 1 - A thrust-propelled space vehicle adapted to be maintained in a centered position with respect to a beam of radiated energy, comprising a plurality of thrust engines 50 mounted for rotary movement about a common axis, a major portion of the thrust at)pl-.ed to suc-i vehicle by each of said engines being substantially tangential to the circle of rotation thereof with a minor portion of such thrust bein.- directed outwardly from si-ich circle, airfoil 55 mears mounted for movement with said engines to apply a lifting force to such vehicle, means for receiving energy radiated toward such vehicle in a beam normally lying along said -,,-is and for applying such energy to said plurality of engines to energize the latter thereby, the energy 60 t.qus being applied to said engines being apportioned in accordance with the rela'Live positions of each of said engines apd the center of such beam upon a displacement of such beam away from said axis, with those engines disposed more n,-arly in the direction of displacement of 65 suc'ii beam center from said axis at any given instant receivlig relativ-,Iy greater energization than others, whereby corrective forc,-s are applied to such vehicle in direet-Lons substantially normal to said axis to maintain such v-,hicle centered on such beam. 70 2. A thriist-propelled space vehicle comprising a plurality o@,@ tnr-ast engines mounted for rotation about a common axis at eqtial distances therefrom, a major portion of the thriist applied to slich vehicle by each of said engi@@ies beiti-, siibstantially tangential to the circle of rota75 tio.-i therp-of with a minor portion of such th@-ust bein.-

d@'@rected outwardly from such circle, airfoil means mount-.d for niovement with said engines to provide a li,-,'t force for sustainin-. air 'light oj' such vehicle, means for receiv@n,- ener.-y radiated toward such vehicle in a beannormally lying olon.- said axis and for applying such e-.iergy to sa;d p'Lrality of engines in amounts appo.-t:oned in direct relatioiship with the respective dista-@ices of each o;4 sa;d eng-ines irom the center line of s-..ch beam at aiy -!-,,en ;-ilstant, whereby said engines are energized by s,,-@ch received energy to prov@de movement o'l said airfo;l neans and to provide corrective forces to su..-h ve:%,icle in directions substantially normal to said axis to mainta;n such vehicle ce-@itered on s-,ich beam. 3. A th@-tist-propelled space vehlicle in accordance with clia-'@M 2, Nvith such rad:lated energy being microwave electromagnet;c eiler.-y, said e-iigines including means for convertl-ig incident electroma-,netic energy into propulsive tar-,ist, and said energy rec,-ivin-, and applying means compris@irg q, concave siir.L'ace of revo!Lltion positioned on said -,x:s to reflect the electromagn-@tic energy of such beam to said eng;nes. 4. A ;hrust-pro,.@elled space vehicle adapted to be mainta;.-,,-d ip a centered position with respect to a beam of rad,'ated energy, comnrising a pair of tl-.rust en-ines ada,)tcd to be energized by such radiated energy and mou@nted in symmetrical relationshio on opposite sides of a central ax;s of such vehicle, said pair of engines bein.mo-,Lited in a si-lbsta-.itially common plane including such c@-n'ral axis and at ,v;th respect to such axis to apply to slich v--h@cle respective thrusts having compor,e.its directed away from such axis, ard means symmetrically dis-,osed about such axis for directin@ energy from si-ich beam to said en,-ines in respective amounts apport;on@-d in accordance with the relative distances b-.tv,Te-,n each ol' sa@'.d engines and the center line of stich be@-@m, whereby sa;d en-ines are difj'erentially energized to exert corrective thr-asts upon displacement of such ax.-s j'rom the ce-@iter 1-ine of such beam. 5. A thrust-propeli-@d space vehicle in acco-dance ",ith cia-'m 4, with such radiated energy being microwave electroma.-netic ener.@y, sa;d engines includidg means for convert;-Ilg elcc+romagretic energy into propulsive thrust, and said directin.- means coniprisid.@ a pair of concave reflectin, memb--rs eaell r,-flecting a portion of the energy of s,ich beam to a resjective one of said converting means. 6. A thr,.ist-prop-,Iled space vehicle adapted to be maintai-,ie,-i -@-,i a centered position with respect to a beam of radiated ener,@y, comprismg a plurality of thrust engines adapted to be ener,@ized by such radiated energy and mo,,ir@t-,d in symmetrical relationship with respect to a c@@ntral a,-,is of such vehicl@-, the thrust produc--d by each olr said eii.-iii,-s bein.@ siibstantially confined to a respective p ' iar@.- ineltidin.- siich central axis and havin.- components both para'llel vv-ILh and directed a@,@iay -,'rom su--h cen@ril axis, and means symmetrically disposed about such axis for d,'rectin.- energy from such beam to said engines in resp--cti-,,e amoints al,)pcrtioned in accordanc-- with the reiative distances between each of said en-.ines and the cant@-r line of s,,ich beam, whereby said engines are differentially e-.lergized to exert corrective thrusts upon displace--ic-@it of such a@-- s from the cent.--r li@-ie o-'c such b,-am. 7. A system for maintainh-ig a th,-ust-propelled space vehicle in space,-I-apart relationship with a mot'ilf,,r plariet at a sel--ctabl,- location with respect thereto, comprising a coptrol station on such mother plan-@t fortransmitting m:crowave electromagnetic energy in a substantially vertical',Y-directed beam to si-ich vehicie, a plural'ity of thrust en,@l;nes o-.i such vehicle mounted for rotary movement about a substantially vertleal common axis, a major port;on O'L the thrust appii--d to such vehicle by each of said engines being substartial"y tangential to the circle of rotation thereof with a minor portion of such thrust being direct-,d outwardly from such circle, airfoil means mounted for niovenient with said engines to provide a 3,114,517 10 lifting force for s@-istaining air flight of such vehicle, means for receivipg energy transmitted toward such vehicle along said axis from sa4d control station and for appiyipg sich ene@.gy to said plurality of engines to energize the latt-,r thereby, the ener.-Y thus being applied to said en,--"r.,cs bc;ng aprortioned in accordance with the relative positions of eacti of said engin-,s and the center of such beam ii-poq a displacement of such beam away from said axis, with those engines disposed more nearly in the di10 rection of disDIaceme@it of such beam center from said a,-,'.s at any given instant receiving relatively greater energ-!zatio.,l than others, whereby corrective forces are applied to such vehicle in directions substantially normal to said axis to maintain such vehicle centered on such 15 beam. 8. A system for maintaining a thrust-propelled space vehicle in spaced-apart relationship with a mother planet at a selertable location with respect thereto, cotnprisin@a control station on such mother planet for transmittin@ 20 microwave electroma,--iietic energy in a substantially verticahy-directed beam toward such vehicle, a pair of thrust engines on such vehicle adapted to be cnergized by such radiated cnergy and moi-inted in symmetrical relationship on opposite sides of a central axis of such vehicle nor25 mally coiliciding with the center Iiiie of such beam, said pair of engines bein.- niounted in a substantially common plane ircluding such central axis tnd at an.-les with resp--ct to such axis to provide respective thr-L7sts to si-ich vehicle having components both normal to and parallel 30 with such axis, and means sylr@metrically disposed about such axis for directing energy from such beam to said engines in respective ainounts apportioned in accordance with the relative distances between each of said engiiies and the center liue of slich energy beam, whereby said 35 engines are differentially energized to exert corrective thrusts upon displacen-lent of such axis from the center line of such beam. 9. A system for maintaining a thr-ust-propelled space vehicle in spaced-apart relationship with a moth,-r planet 40 at a s-@lectable location with respect thereto, comprising a control station on such mother planet for transmitting microwave electromagnetic ener@y in a substantially vertically-directed beam tov,,ard suc'h vehicle, a plurality of thrust engines on such vehicle adaptcd to be energized 45 by such transmitted energy a@id mounted in symmetrical relationship with respect to a central axis of such vehicle normally coinr-iding with the. center line of such beam, th-, thiust produced by each of said engi-@ies being substa.,itially confined to a resp--ctive plane i-@icluding such 50 central axis and havin- cor@iponents both parallel with and directed away from such central axis, and means symmetrically disposed about si-ich axis for directing energy from such beam to said engines in respeotive 55 mounts apportioned in accordance with the relative distances betweeli each of said engines and the center line of such energy beam, whereby said engines are differentially energized to exe@rt corrective thr-usts upon displacement of such axis from the center line of such b-,am. 60 10. A space vehicle, comprising body means, antenna means o-.i said body means for intercepti@ng incident n-iicrowave energy, rreans on said body means for converting said intercepted microwave energy direetly into a fiight-producing force applied to said body means, and 6,5 means for directing microwave eiergy intercepted by said antenna means to said converting means. 11. A system for Temotely energizin@- a space vehicle, comprising means at a control station on a n-iother planet 70 for generating mir-rowavp- energy, means at such control station to radiate such microwave energy to such space vehicle, antenna @nieans on said vehicle for intercepting such radiated microwave energy, n-ieans on such vehicle for converting said intercepted microwave energy directly 75 into a flight-producing force applied to such vehicle, and

12 means for directing microwave energy intercepted by 2,813,242 Crump --------------- Nov. 12, 1959 said antenna means to said converting means. 2,941,764 Lee et al - ------------- June 21., 1960 2,949,550 Brown --------------- Aug. 16, 1960 References C@led in the file of tllis patent UNITED STATES PATENTS 5 OTHER REFERENCES 889,790 Kitsee ----------------- June 2, 1908 "Vistas iii Astronautics," published by Pergamon Press 930,50-0 Vreelaiid ------------- Aug. 10, 1909 in 1958; page 192. 2,471,744 Hershberger ----------- May 31, 1949 Advaiieed Piopulsion Systems, published 1959 by Per2,769,601 Ha.-opian ------------- Nov. 6, 1956 gamon Press, pp. 81-88.

Un'l'ted States Pateiit Office 3,114@517 P a ' , e n i t e d D e c . 1 7 , 1 9 6 3 2 it is -ciaer,-,Ily iiecessary to focus th-. transmitted energy so as'to ach;ev-- a des;rably high power density at a remo@@- -oint o.- area wi,h respect to a given generator or transrr@iter power level. Ii accordance ivith the laws of ooties, 'che sharl--@iess of tli-, beam produced by an anterna as the ralio o4l antenna dimensions to the cf the transm.tt.@,.! energy. Thus, for a giveli or desired power densi@y or beam sharpness, a decrease in the wavele-@i-th of the transmitted en,-rgy permits a co,-rcsi@ondirg decrease in the dimens;ons of the antenna. FroLi the st,.)ndpoint of mechanical convenience, it is -.ene,@-ally desirable to employ small ar@tennas and other com,,@,on--n@s, ar,.d it is.therefore advaiitageous to employ cic-,-gy of very siaort wavelength. I.,i additio@i, the difricul,,ics in relatively Ion.- wave transmiss;on as a resiiil ot na@Lural and man-made interference or noise (whic'- rl noise wouid interfere with tl-ie transmission ol ra-lar or co@- iiiiunications intel',igence via the microwave roi@,er beam) e@o not ocr-i-ir with aiiy appreciable signiflc@a,2!,@c at microwave frequencies. Also, where the space voliic"e is to be operated at an altilude above tlie ionosi@i-iere, Io-@i- wave transmission will generally be reqecled by the re,-lectin.- layers thereof, while niicrowaves pass through stic.,i i,@tyers subscan@-lallyunafirec',ed. in v-'--w of tlae sever,,tl adva@qta,@es stated above, it might apr)- @-,ir cles-irab'@e to employ the shortes, wavelength poss@ble com-,-ilensurate wi-Ilh the power-generatin- cip-ibilit-'@es of the trars-niitter at the wavele.,l@.th chosen. A iower limit is 'iqxed, however, for the wavelength that may bo i-ised -in a practical radiating system in view of t,--c i@ioreas:@n-, ',--sses due to absorpt;on occ,,irring in the ,L@'iuospLere at wavele7i,-ths b--Iow five to ten ceiitimeters. In t'Lle to two centimeter region, there is a peak i@i absc)rptioi by water vapor, and even for dry air the ab@.orzt'@on of el--c,6romagr@et;- energy increases very r@ipidly one or t,,vo centimeters. It may thus be seen t@iat m;crowaves iTi a region having the ai)proxin-iate bounds of two and th;rty centimeters are rea-dily adaptable to coaven,'@ent radiation of energy to a remote point w;th s:rall transm@'@ss:.on lo3s, w@.th th@- preferred waveler@gt'@-s being of the order of five or ten centim,-ters in order to accomplish effic-'@ent i'Ocu,@ing with a transmitti-@ig leiis sys'Lem of rea.-otiabic size wi,hout inflicling an intol--rable power loss by @ibso.,:ption. The '@ey to the prp..ctical utilizat;on of high-power el.-ctroma.-netic beams for remote en-.rgizatio@n of space veatid the like is a device wh;ch will @-enerate large amou--Is of po@ver w: @thin this wavelength re-ion. In a-Jdit,.o@i, maiiy ar)i)licat;o-@is of such highpower beams -rt,,q,,i-ire stich refi-iements as broad electroric bandwidth and low phase d;stortion, placing the additional requireol sophisticated performance on 'che hi.-h-power generator. A eevice which currently sat-sfies ti-,e duel reqi-i-ire@-nents o-f L,:.-h nower oul@put and refined performanc6 is the Amplitron tube, a rela'ively new typp- of crossedfield vacuum tube which may be used as a compact, highly el-Ecient, broadband amplifier caidable of handling hi,-h pea!c and avera.@epowers,-and wh-',Ch generally corilpri@-es a ci@-cular but no-i-reentrant, dispersive network malc!i-d at both cr@ds over the frequency region of interest, a-@id a reen@rant electron beam originating from a co@it;nuous'y-coated (or nearly so) cathode coaxial with t',-le neLwor'@-, with a D.-C. polential being applied between t'Lie calhode and anode, aiil a magnetic field adplied pa,- allel to the axis of the cathode and transverse -to the elec'@ric field between the anode and the cathode. For a more com@ ol--te descri t;o@i of the Amplitron, reference -P @ may be had to my application Serial No. 706,812, filed Jartiiary 2, 1958, for "Low Level Diii,)Iexer System," now United States Letiers Patent No. 2,933,723, which iss@,icd April@ 19, 1960. Amplitrons currently available are 3,114,517 MAICIROVYIAVE OPERA i-z@D SPACE VE, I-HCI-F E4 S Wiliiam C. BrowE, Westen, Yines., as!5@ignor to Raytheon Company, Lemin,-ton, M,@Fs., n corporntion of Delaware FL@ed M@ny 12, l@' S9, Ser. ?-To. 812,710 5 11 Claims. (Cl. 244-1) Th-z's inv.-Pt@'.oTi pcrtair%.s gcnera-"Iy to space vehicles and th,- ll""c, and morp- particiila,-'IY to a novel form of s@jace vel;clo and a system for mainta,'.-P-@'ng such veh-icle in 10 flig',,t or at a des-irtd loca-io-,i in spaced-apart relat"@Onship wilh respect to a mother planet or the like. 'The )rlor art ai--tore-@s many ex,,im-:)Ics of apparl,,tus a-dap'Led 'Lo b-c nrc@,celled :l spaced-a-!3art relatioiis-iiip w'ith the ear@l-, as well as systems for main'taining this r,-Ia15 t-'-o-riship @'n ()T,.@?os;tio-ii to th3 gravitatioilal field thereof. s of th,s typ-. a-ze co-iv,--iit:onal aircra' Exe@up'ary 13vce t (both jet and pro,-,eller dr@ven) and the more modern ti,@i-manned or pi'lotless vehic',es s-,,ich as rocket--oro,- elled -iiissiles. however, the operation of eaeii oi@ t@iese ve- 20 hicles of the prior art necessitales the exi,,--iidi@ure of a ftiol carried by th,- vehicle. Fi:Lrther, w'@iil-- an orbital Ear,lh sat@Dllite reqlir--s no appi'@ed enorgy i-q executin.- a g;v,-.n orbit, eiormotis quantities o,- -iru-,l are coisumed ill iau-ilchi@-,- the sat--il@te in'to o-bit. Also, wh-,re t-ti.- 25 sptell,'@te ve'--icl-- is desig-,ied for ti-,e stibseq@aent correction of or o@her change iTi '@he o@b-@'@a'@ path, a fael supply mi-ist be carried by th@- satell7te in o.-der to provide thc@ desired corrective thrusts. it is t@ilis appirent tha@' in each ol' 'chese pr',@or art ve- @0 h-'.cles a fiicl si-ip,3!y -miis" be carr-@'Cd ther@-by for local constir..- ipt@'@o@i :n order to -@'nitiate, mainlain or aller a g@'@ven -Lq-l i@,h'L pattern, whether such pa"tern i--@volves motion o-@ the ve!a:cle relative to the Earth or a substant'@ally motio.'lless hovering with resrect there@lo. It tiierefore follows 35 that the max;ria,,i.,ii payload ekoab-ii-ities of such ve!i-icles are limited by t'@-ic fact that the vehicle must support ,.he o-@ the _fuel carried thereby. Also, s-ach vehic-les are not natl,.rally ada.2ted to ind--t@in-,t@-iy lo-,i.- tcriods of contir@@,,oil -s operatioq, s,.nce the fuel supply therein will 40 ever,-tually be exhaus',Cd, r@--cessitating a ret-,trn ot the v-,- h;cle to a relueling base, or alter-riatively, an in-ilight refueli-iig process as is accon-i:,",ished w-ith some conventional aircraft. Tho utiiity of a space vehicle or 'Lhe lil@,e which is ca- 45 pable o-- sustained iii.-ht over an inde@r-@nitely lon.- per,'@od of 'Linie without employinl- a local Piel supply is evideit, and the applicalio.,is ther-,-For ar,- nlirr@erous. For example, a veh@- 'C'.e c-,tpablp- oi. peroetiial op--ration (exc-.pt ior fa-'@lure) and stationed in space above the 50 sur-fac-- of t@o Earth, either w;thin or will'iiout theatmosphere th--reof, rtiay perforn alarm and surveillance tasl@@s by radar tecliniciues, alorig w@.th -Uidance and protectior of de@lense vehicles, and rr.,ay sini-Lilianeously provide lon- haul broadband commuiications. Systems of 55 such velicl-,s or plat_forms may be established to provide radar and comm,,in:cation net,,vorks. Th,-se desired opera"ional characteristics ire provided by the vehicle of the present invention, which vehicle is @iz -is of transmitted m; row ener@' ed by mcai @c ave electro- 60 ma,-netic e-@ier.-y that is beamed toward the vehicle. The microwave ener-,y incide-.it upon the vehicle is converted i.ito appropriate mechan@cal forces which produce the desired -iqi,@iat operation of the vehicle. Tlle advantages attenjqant the utilizaticii of m-'@crowave en,-rgy, n contrast 65 to electroma,@net;c energy of other wavel.,n.@'hs, are readily apparent. Micro-wa-,,es have been generally deiq.ned as radio waves whose wavelength is less than 30 centimeters, with a lower wavelen.-th '@-imit on tho order of o-@ie m@,llimeter or one cent-'.Meter so@n-.tim,-s bein.- 70 appl-'ed ',o what is called "the microwave re-@'o-ii." The superiority of m;cro,.vaves is dute in part to th,- fact that

3 capable of producing 15 or 20 kilowatts of average ra7.- dio-frec,,@aency power i-@i the nei-hborhood of ten contimet-,rs -in wavelength, and future models are expecled to yield 500 kilowatts or more average power, with 50 me@.awatt peak power. It is accordingly a primary object of this inventio-i to provide a soace veh-lele or the like designed for an indefinitely long period of operation either in moving flight or at a selectable location wilh respect to the Earth or other mother planet, with energy n@- cessary for such op-,ration being sut)plied to such device in the forr-i of microwav-- clectorma,-netic energy. A further object of the invent,'@On is to provide a system for maintaining a space vehicl@e either in moving flight or at a selectable location with respect to a mother plan--t or the like in response to microwave electromagnetic eiiergy transmitted from such mother pla-@iet to fne vehicle. In accordance with an exemplary embodiriient of the present invention, this system for maintaini-.ig fli@,,ht of the st)ace vehicle includes means on the Earth or some other motli-.r planet for radi-.iting m-icrowave ener.-y in a beam directed toward and focused on th-. vehicle for siibstantially continuously stipp'iying such vehicle with the power necessary for the operation thereof. The space vehicle of the invention has means associated therewith for receving and converting incident microwave energy into appropriat-- forces applied to the vehicle to sustain fliglit. The received microwave energy m@ ay be directly converted into a flight-producing force as by an ion en.@ine or the like, or the microwave ener-,y may be subjected to a mesne conversion to heat. In the latter case, means are provided for applyin.@ the heat con,,,P-rted to a stiitable fluid medium which is expanded thereby to perform the work necessary to pro,-,el or siistain the vehicle@ In one t)referred form of 'Lhe apparatus of the iivention, a pluralil@y of thrust-providing engines are motinted for rotary movement about a substantially vertical corrnion axis along which the beam of energy is norirally transm;tted, with suitable airfoil means beip. mounted for movement with such e-@igines to provide the lifting force necessary to maintain fliaht of such vehicle. Means are provided for apportioning the received ener,- y between tl-ie several engines in such manner as to selectively energize the en.-ines to maintain the vehicle centered on the transmitted beam. In an zciternative 'lorm of the apparatus of this invention, a plurality of thrust-providing engines are synimetrically positioned with respect to the vertical central axis of the vehicle along which the beam of energy is normally transmitted. Means are provided for distribi-iting the received energy between the engines so as to differentially ener-,ize the engines to apply correctivc forces to the vehicle Lipon the occurrence of anguiar or translatioral displacement oj' the axis thereof from the center line of the radiated beam. With the above consideration3 and objects in mind, the invention itself will now be described in connection with a preferred embodiment thereof gi@ien by way of example and not of limitation, and ivith reference to the accompanying drawings, in which: FIG. I is a perspective view of a preferr.-d form of the apparatus of the present invention, schematically indicating the control system therefor; FIG. 2 is a partial sectional view in elevation of the vehicle shown in FIG. 1, 'Lhe section being taken substantially centrally of the vehicle; FIG. 3 is a plan view of a portion of the apparatus of FIG. 1; and G. 4 is a partial sectional view in elevation of an alternative form of the apparatus of this invention. Referring now to FIG. 1, one prefcrred form of the vehicle of the present invention is indicated generaliy at 10. As shown, the vehicle 10 is adapted to be maintained in fliglit or in hoverin.- p-ositioi with resp-,ct to tlie Eartli or other ii-iotlier plan.-,, 12 by riie-,ins of energy traiismitted to 3,114,517 4 the vehicle as radiated microwave electromagnetic energy in beam form, as ind:@cated by lobe 14 having center line 15. A suiiabl.e tra-qsmitter 16 is provided for this purpose, along with a beam-forming transmitting antenna 18. As v-,,ill be appreciated by those skilled in the art, the represo@ilat-ions of the transmitting equipment and microwave bcai-.q in FIG. I are Iiighly diagrammatic in form, and the present i-iivention is not limited to any particular transmitter or antenna assembly. As a practical matter, how10 ev--r, tl-.c r@-iqcctor of the antenna assembly 13 is considerabiy larger ttan most of the reflectors of the prior art in order to focus a large amount of power at a highaltitude (e.g. 65 ' 000 feet) space vehicle. In an exen-iplary embodiment, the antenna re-qcctor is at least partially supported 15 in a large bowl or other du,--out area on the Earth's surfpce so as to provide a convenient means of support therefor. Also, the antenna may actually coniprise a lar-,e r@umber of small horn and reqector assemblies. In addit;o-ii, the tra-- ismitter 16 is capable of much greater power 20 output than most of the prior art transmitters, and, as stated in the earlier paragraphs of this specification, the povier-generatin.- element of the transmitter is preferably an Amplitron tube in order to achieve sufficient power OU'L@T)Ut. 25 Th-- microwave energy that illuminates the vehicle 10 is interce-,)ted by the Linder or concave side of the reflecting member 20, the curvature of which is such that the energy rece,' .,@ed along a substa-@itially straight line parallel to the ceyitral axis of the radiated beam of energy is re3o ficcled itato an annular opening 22 in the frame member 2,1.. The latter frame m-- m@ ber may preferably comprise a hollow .wiavegu,.de for the received radiofrequency energy, and the energy applied thereto through the openiii@- 22 is, in turn, applied to the several engines 26 con35 nected thereto. The means 'Lor maintaining fli,@ht or hovering conditions in tli-- veh;cle 10 include the several engines 26, which effect a rotary motion of the vehicle frame in the direction sho-A7iii by the arrows about a substantially vertical central 40 axis 1-iormall.y coinciding with the center line of the transmitted beam 14 of microwave energy. Upon such rotary motion of the vehicle frame, a suslaining lift is provided by means of a plurality of air,@Loil members 28, which may ,enerally be in the form of the rotary wings of a helicop45 ter or the like. It will be understood that only the basic elements of the vehicle 10 are shown in the drawing, and that otlier frame members and the like would normally be provided to stipport a payload of radar, conin-lunication or other similar equipment. In this connection, 5o the bcain 14 also provides a signal-information link betv/een the ground station and the payload equipment on the vehicle. FIG. 2 shows in somewhat ---reater detail the construction of the apparatus of FIG. 1, with the showing of FIG. 55 2 beln.- taken along a vertical plane through one of the supporting airfoil members 29. The construction and operation of the several thrust engines will not be discussed in detail herein, since a complete description of engines suitable for this purpose is provided in my tppli60 cation Serial Number 812,697, filed May 12, 1959, now United States Letters Patent No. 3,083,528, -,vhich issued Apr-'I 2, 1963, and assi.-ned to the assignee of the present application. As disclosed in such application, an exeril)lary embodiment of an eng,'.ne suitable for use in the 65 vehicle of the present applicalic)n includes a h eat-exchan,-in.- contair@er means adapted to be energized by microwave energy to heat a gaseous medium therein and cause expansion of same to produce a jet stream for providing a propulsive tlirust. In one preferred form of th@- inven70 tion, the container means comprises an electroinagpetic waveguide of lossy characteristics which procluces heat upon er@ergizat-lon by su@.table clectromaga--tic en.-rgy to raise the temperature of a gascotis mediu@-n p,-,ssing thercthrough. A member of stacked ar@d clos--Iy-spaced elec75 trica'ily lo3sy piates is preferabiy motinted willhin the

wave,-uidp- to serve as the main m@ caqs for absorb in,microvvn,i,e energy atid cori-- r'Lin.- same inlo heat, as dL-scribed in detail in the afo-.zmertioned copel-ding aoplicat@'.O@l. 7,b-, plurg@lity of ciosel@y spaced plates form therebet-,A,7e-.n a s@ries of narrov,, p,-@ssa,@,es thro-agh which pass--s the ga@.eous i-.ed;-,im @;,ihirh is to b3 h-,ated thereby. Tii@, microwa,ie ener.-y employed ',s of suiMe@'@Cntly hi,-h frequency to 1)roclucc@ a prono,,,need sl,:i-rl efl,@ect in the -,vave-u;de and assoc;ated so that the energy expe,.lded ii creit;ng he--t in the st,-ady ta,@- condition is ef--fc@ct-ively and qticl,-Iy - Lransforr--d to 'the gE,.sco-,Is meditiT,,-i in which the Dart-icular co-@idi-ictor exh'@bit,:--i.- tl,,e si@in effect is immers-.d. This latl,er feature is partic-,,ilarly advanta.-eous in transient-state cond@'tio@ns Nvith respact lo the aliility of th,- engi-.ic of this ip-vention to pr(>vid-, almost instartanco-LLs r--sponse 'Lo a change in the le,,,,el of the appl,'ed nucrow-p@-ve enercy, since li't.e or ro time la.@ is invo@ved in convertin.- electroma.- ret,:c crier,-y to hea@ and tra.Tisferring it to the coolin.- -as. As ds evideit, the licated -as iro@y be form@-d into a jet stre,,i @m in or,-i--r to provide priD@DLIsion, or a turbiqe may be driven tl-,ereby to prov:dc a rolar,17 shaft oL,'Lput 'lor driv,'--@ig a prop.-lic@r cr th-@ li@le. As may be sce,,i iii FIG. 2, the eng,'@nes 2@rg are supported from the rotary frar@7,e member 2;1 by mi eatis of sli-'@tab'@e si-@Dporting -Tnembers 30 whi--h -)'@so serve as ,he mcans for transferring the microv;,ive energy in -Lhe in@erior of the 'rame member 2@' , to the interior of the eng:ines 26. Th,,is, each of the s-apporting membe@-s 3,9 nrist be adapt--d to act as a transm,ssion lipe of short 'iength for the radiofreq,,icney eicr.-y employ-@d. -The parcculay ci-irvatiire o-f the refle--tiD,- m@-mber 2il is chosen so as t-- eitect the ref@l---,@ticn of radiqted eiier@@y indi--i',ed i,-i FIG. 2, viz., the epcrgy transmitted toward tii-. ve-',iirle i-ear-hes the reftector m-,mber 20 ,Io--.- subs'ancially strai-ht parallel pa,hs as shov,Tn by the verLice-.1 dash-dot lines, ap-d unon rc,,-flecla'on all of the received encr.-y is focused o-ii the open:ill.- 22 in the frame nici@iber '@IJ so that 4t may be traiis.'Lerred inlo the several engines 26. F:G. 3 shoi@is t'--lat t@he dircct'lon of thrlist produced by eacl@i of the eigiries 25 is not qui@e ta-iigep-tial to the circle c,f rotation thereof. As shown, t-he ene-iries 2,@ a,@7e mourtod at a small a-@i,@le wi@Lh resp@@c, to the peripl-icry of the fraw-e r@i,-mber 2-,!, so th-at vvh-'@le the major port;o@l of t.:ie thrust produced by each of the en.-iiies is tangential to such perip-.Iiery, a sm-,ill com@ponerit thereof is d;rected a-@,iay from ',he center of Cr@,- vehicie. T'@,is co-iistruct;o-tl is eniployed in order to provide a vehicle v,,I-iic@h is r,---Pable of a -ei'L-cznt.-riii.@ or bc,,im ridin.- opera';on, as will ir.c,re fuuy describ--d below. In the operation of t.e d.--,,,ice thus far described, transmitter 1 6 -e@ierat.-s a s,,iiiable microw-,ve &I.-nal -f o,- trarsmissioll to the veh@cle IC@ by means of the radiatin,@ alitenna -!LO. In tl-e normal operalion of the dev,'ce, t'qe refiectin- member 2@ will be ce-@itrally posilion,-d iii the rad-ial,ed beam 14, aqd thc@ energy of the beam iiill therefore be refiected ;n eqiial amou-iits to-;,iard all port;ois of the annLIar ovenin@ 22 in frame member 241. As a result, ti%c +hree c-ii.-iies 26 will receive equal amounls o'L the radio-freqL,.ency e-.ier.@y, and normal opere,.tion is thei-eby efiect,-d, res-dlting in a rotary movement of tlc eni,@,nes 26 and the frame member 241 about ',he ceptral vertical ax;s of the vehir-le 10. As mentioned abo@,e, such rotat,'.onal movement of t@e frame member '-74 produces a correspor,d;r@.- rotation of the ,iirfoil members 23 tO PEOvide a vertical thrust for maintaining the vehicle 10 in fl;g'iit or in a ho-,,eri-@i.- position with respect to the mother planet 12. in order to maintain the vehig!e 10 in a desired location with respect to the center-line of the transi-@iited rad:lofrequency beam 14, viz., at,a centered posilion with the verlical central ax;s of the v.-h@.cle coinc@ding with tho cc-iiter Ene of tl@e trirsmitted beam, the shape of the coica.ve re@fl,--.tin.- surface of mem-ber 2fj is chosen as described above to reflect ener.-Y of the beam 14 eqi-ially to the 3,114,517 6 several engines 26 when the vehicle 10 is properly centered in tl-le bcarn 14. Upon a lateral displacement of the vehicle '-,,G from Lie beem 1,1,, one side of the reflecting slirfice 20 will be illuminated by more radiated epergy than t@i-. oppos;te side, ar,.d t@le several en,-ines 26 are tL-,-rcupoii di-fterentially energized to provide co.-rective lateral forces to achieve rc@aentering of the vehicle in the be-am. it will 'oe understoo-,l that the desired tolerance as to vehicle position and t'ne 1,-Lteral diyfeiisio-iis of the beam 10 and 'che volij@le -,ire so interrelated that a displacement beyo@id s-,ici-i tolerapce v@i@ill restilt in a significant degree of si-ich differe,,ltial eiergization. For example, if the vehicle 1-0 wer-- to be di,@iilac--d toward tho ri@-ht dn FIG. 2, the left-hand portion of the reflectin.- -n-iember 20 wotild lie 15 ilearer the canter o@l' the bearti 14, and the engine shown in F',-G. 2 viou,,d thereupon receive a greater amount of orergy than 'Eh-- o'!-.er engines. Since the engine Z6 of 2 (qs -,veil jas each of t.ip- remainin.- engines of the vehicle) provides a componerit of thrust normal to the 2o circle of rotation thereof -,ind direct@d away from the cent.-r of th-- velaicl-., such additional energizal@io@i of the engine she-,vn in I-'IG. 2 ivill provid,- a resultalit lateral tlinist toward the left in tb-is fi@-are. 1+ is evident that the pE,.rLictilar engine 26 siiown -in FIG. 2 will be in motion, and 25 ii,@ill theref o -c no.@'L rcmaii-i at the posit",On shov,,ii to continuously receive tl,-e mijor Dortioii of the ener,@y intercepted by reilector r.,aember 2i'@. As ear-h of the engines Z6 passes throu,-h the azin-i-.,ithal positioti of rotation opposi'@e to 'L'-ne direction of lateral displq@eement of the velicle 30 10 from tlae ce--ater of tL-@ bear.-i it then receives a @reate., onergization th-,n the rom@aining engines, and suci'i dif-@--e@-citial ener.@ization of the several en.-ines 26 contin-aes witb the rotational moveneiit of such engines Lilitil the vehicle is o-nce ag-,tin ce@itered in the beam 14. As will 35 be aparec;al,,.d by those skilled in tLe art, there must be a miiimiim 1,?,g in Viie transient response of each of the ei,@,,ines 26 @iii order to a--hieve the selfcenterin.- actio@ii. 'in this conne,-tio-@i, tic efficary of the en.-ine of my aforemetitioled copoiding @appli--a-ion is evident. As stated 40 above, the therma.1 time la.- of t@-his engine is mini,@nal as a resul' , o'L th-, fict tlln-t there is a significant skin effect in the micro-,Ti-,tve heal exchan.-er, and the trans@e,@it-sta"e heat ch@Lnl-es are prod,,iced in intim@tte proximity to the fluid m--dilim to bo heated. As a result o,@' the propinqi,-,ity of 45 tl,.e heat so,,irce kltlie shallow skin eili'e,-t penetration of the heat-excli-an,-;ng wall) and th-, s-ink (the flu;d med@ium to b-- heat--d), such are ible 'Lo respond almost instar.LaTicously to a el-i-,tngein the power idpiit, tlius makidg tiae selfcentering of v--hicle 10 feasibl-,. 50 An a,-@@.-r@ative form o-r the api)aratus of th;s invention is shovi-ii in FIG. 4, wi'll the vehicle tlierei.1 be;n,- indiepted aer@eral'iy -@Lt 32. As shown, the vehicle 32 i-@icludes reiq@ctor -@l,,imbers 33 a-id -@,4 havi-@ig concqve lower surfic@-s 'Lor ref@ecti-ii,- @@ncident microwxve energy of beam 55 l@, to resi)@-ot-'@Ve fo,.@,il po;nts ilidicated generally at 35 a-@id 37. A plural;ty of sli-oport-ing arms 40 are provided for moun@ing the respective engines 36 and 33 on the re-q-.ct,'np, moribers 34 and .33. The diagral-iimatic showoi eiigines 31,4 and in FIG. 4 are intended to rep60 rescnt jet eii-@iies of the, typo disclosed in my aforementioned cop.-nd-ir@g appilcatioti, and it -is to be understood t'nat t@ic microwave energy necessary for operation of eich en,.,7i-.e 36 ivd 33 is received at the upper or intake eiid '@liereof. Tile focus "t)oints" 35 and 37 are in reality 6,3 -,reas rath-@r than po;nts, ard the engines 36 and 38 are i@itp-nt-onally mounted slightly inboard of a centered position with respect to the associat-,d area 35 or 37, so t-at norninily no" all of the en--rgy at each area is directed i-,ito the respoctive engine. This condition is ind@'cated 70 in Fll-j. 4 by t'@e spveral ref'tected dot-dash lines which poss by ratiier than into the mouths of enoines 36 and 33. T.@,e part,clilar rro,-ortion of energy that is thus normally wast--d, qs com,3ared to tiat portion which is collected by ti'i-, en.aiTi,-s, is a mitter ot choice in design in a given 75 inst,,irice, but it is g,-n.-rally desirable to utilize a m-,tjor