Interim Report on Design Study for Nuclear Rocket

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UNIVERSITY OF GALI FOR NIA k. G I as si f ica t io n Each perron rho receives thir documrnt murt sign the cover rheet in the space below. Route t o Noted by Date Route t o Noted by Dot e

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Radiation Iaboratory, Udvemity of U or nia Thh report covor8 calouhtlona and ideae regarding a nuabar The general conclusion is that such a rocket seame rocket of the conventional type, that l a , using hydrogen aa a propellant and e graphits de rated reaatar beating thm hydrogen by ordinary heat attractive and can poasibly be made w i t h a gross might af lees thsn a hundred thousand pounds to reach a range of five thousand milee pltb a pay loed of four thousand paunds.

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The purpw of t h i s atudy u~ilprimarily to learn sarpbthhg of tha To aoo-h Mau a buh ~ osr problem of the design of adear rocrk.t. were rnade of what WM believed to be a typical 0-8. uaa eatlusted t o be about 60,OOO lbu. to reaab a range of 3,000 W with a pay load of 4,000 lbo. takeoff weight or l20,OOO lba. enough heat transfer surfaoe t o hold the graphite temperature to 3,000' Kelvin. Calculations were made on moat of the other part8 of the rocket. indicated tbat the thrust chosen wau a bit lcw and ths weight abit 1- 80 t h a t during the c m e of the calculation changes ware made which do net agree with the original asamptiom and w i t h the earlier parts. As a remit, at present there ia no consistent set of figurea for all parts of the rocket. Hu wever, there it4 sonw ido ation that the effect of theme emom uaild be The ut art hg thrust waa adw to bit M m t& The reautor vcld designed on this bash With This study follma the N a r t h Aperican rqxxt rather cloasb, The North Ibrican repaTt vaa not received until most af the ffgures presented here were completed. seen by the writer i n 1952. Howver, a partial version of this report had been

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It ahauld be noted that thb report does not represent a stopping point in the study. gathered up to now for the use of people at Livermare who w i l l be looking into thfs subjeot further. One result of w h a t has been lsupbd 80 far io that the perfof the rocket aa a whole Is qui b monsltive to many rariabl-. and properties de,tsl.raining these vurIabb8 are generrilly known but not to lb neo486ary awuraay t o datermima the or pay l d with any dogroe ad important information learned by c vt iv ely inexpensive testa and ady8iS. The pre lh har y conclusion seem to be that uith the favorable result of testa of materials end performance of components a missile to carry 4,OOO lbs. 5 , 0 0 0 miles should be possible vith a gross w i g h t of under 100,ooO lba. Ita purpose is to collect the information that hae been I t appeara that this information oan be^ improved and muah ame

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A 8 many a as qt iom are neceaeary it i8a good idea to have 801~3 bas18 of conservatism or optimism to make a choice between various numbere that can be aasurped. optimism ae the baaie. There is no n e d to study bar poor the performance of such a rocket odd be* is not poesible or desirable to 1308 haw good one nrigbt be if the m o s t opt-tfo reaulta were obtafaed he very we.ht - bbeliomd t o have beerr releotsd are assuroptiona whlab have a reemonable hoe af being verified. The intention waa to use a policy of comernative The answer is too obvious. On the other hard, it IWnight be possible t o build (L a-le rocket to reach the where ccnaplication is defined as a multipliaity of ba8icdly reliable required range but it ia probably much hardsr. dropping tanks are assumed t o be poaeible or a t leaat not rulsd out because they are complicated, vhat can be done with it, rather than solving for the rim that would rea& in si- can be made with uansiderable ou~fldonce. to look at all paFtrr of the H e m with #e exaepticm (d those auamn to i. ohemtical rocket. It is dffficult to f u m aqy jUagment on the dstaU.8 wltbout having their effect on the memall parfarpsnoo and tbis require8 a knovlsdgo of haw the overall perfomance is dohrmined which apynmt(l to the 8ame thhg tis detarnining It. that were obtained on the rarioua c-tu of the mobt. In particular, such ideas as Tbey should be judged only on the basis of w i g h t and The third policy vau t o pick a certain sim rocket and see If the siae picked Is nearly right then the ocaTeation The rcupainder of tha report oormista of the figuras a& res&. A n<winal thrurrt of 120,OOO Ik. is taken t o glve an acroelrrfioor of G2 a total mi t d 60 OOQ lba. &raphita rurfaoe. The pr88Sure exxi of the notale w a r taken originally aa 200 psi. Later, aa the specifio inpulse appeared t o be 1-r than d06ked this waa increased to 400 prri so that part of th4 figurea are 001 ana baais and part on another. of the wight of the reaotcn. adpup whether 200 or 400 3.8 opth, Both should be d cul at sd out in the diruaeter of the nosiLe taken aa 3 ft. At the temperatum end psmrr~ determined the f l m rate of about 180 lbs/mea through the nos-’ and the nozlsle throat area of 1.5 sq. ft, 13.0 and the exit pressure 2.3 l b / sq.in, absolub. when the nosale exit prsssu~eequab the bad p r e r m e then oams out 25,300 ft/sac and the specific impulse 680. T ’ b tspP.rrtur0 oi the gaa at tho aotsle Hffever, it is still a question considering the sffeot debil and cunpared. The mxlmum The nossle expansion ratio then becamb The exhauut veloaity A t the flow rate of 182 1bs/6eO

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a thnmt a t the bok pressure out U2,ooO Ibs. Thir I 8 bigbm thn the original l20,OOO and presumably w o u l d man that the flaw should be reduosd~ However, calculations on the reactor were all based on 182 Ibs. a s e o d so the increase thrust waa assuPed to be anew basic figure. altitude on the thruet uaa calculated by the msthod outlined h Zuorou, J& increased or decreased by the difference between the exit pressure d the ambient preesure aoting over the area of the exit of the nosdo. The effeot of J That is, the thrust is assumed to be The noasle is am- t o be oooled by bleeding aold hydrogen ga8 through the walls. but a rough gubss a t 2 Iba/aea has been urred. the throat and part of the axpandine seation of the nosrle. calculation made t o determine what part would require liner and w h a t part No calculations af the quantity reqdred have bean nad. A grapbita liner i o wm3 for There ir no 2. SIse of the Reactor. To withat.and high temperature hydrogen the maat pati d reaomoderating malarial 88- t o be carban in the fmn of grspbih. Even gnphita ia at&&d by hydrogen a t high terapsraturw forming ~ ooQ ~so that a m method of proteotion 58 wcw881y. cireonitna or possibly ether metal in the form of a oarbide an the 6urfacwa af the passage will pravide this protection. that tantalum carbide vill protect the graphite. not very extensive axxi no samples apparently were pr duc dw hi & were protectad at all pinta. It its poirsible that tbb ube @fh ntdha, Teatu by Narth American indieatad Houever, these tests were Uhen proteution is not uad the erosion l a rapid ata

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Besides proteation the graphite m m t be impregnat& with U235. .2 grams af U235/d has been obtained t e n times as much 8s required in the reaotar design eonsidered here. has a density of 1.6 to 1.7. North American has tested a aq les up t o 1.95 density whioh indicated satisfactory properties althougb not all the propertier, of interest were of lover density. North Pmerican found also that graphits uwe8sed at high temperature8 appears t o hold ib shape d hawe remtmablo pr*i.r. They have reached a density of over 1.9 i n thi8 way. t o Brewer graphite oan be caet and this should meah a density af nenr ttU HJarth Adcan. This is ebat density of the graphite must be aa high a8 psi ble. ordinarg pile grapbib --I However, the theoretical denaity i a 2.25. The design of reactar envisaged consists of a large number af 8 d blocks or bricka so that if high density graphite were not obtainable in large pieees this probably would be no handicap. The effeut of graphite denaity on the m8ss of graphite required for the core is indicated in Figure 6. The lawer curve vfiiah is drawn for constant gas passage area ahuuld be used as this provides sufficient heating surface mar the r a g e of dearritier the operating teaperatme w o u l d redue the mam of grapbite required fkam uhiah w o u l d aake a largo dffferumoo in fhe perfammao of tha mardl roakbt. It will Iw noted that an innrease of density fron 1.6 to2at Tbe problem in heat transfer i s t o provide suffident surface area to tranrrfer the paver generated with eu t exceasfvo praJ8urS drape Tb. power required to heat the 182 Ibe/aee to 2300° K is tha order af 3,ooO Ebr. The power dermity WEB manmid t o have a triangular 8- beth rrdially Md t h e maximum pwer density wa8 assumed to exist aver the middle tbfrd of' the length and of the diameter, This power density and the total mass flow gave the rate of increase of temperature a8 the gaa paased through the chllnMb. In the central ahannel the wall tempsrsture vcu a a d t o fnareare fn #kpr from 1,OOo t o 3,000 degree8 ab the gas passed through. The pwer denaity at the surface assumed at 25% of maximum d

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ktween gas temperature and w a l l temperature and the hsat transfer ooeffldent the heating emface required a t ea& point a d d be determined. a conventional reh tion for film coefficient in ~S~IIMYof' Reynolds and Prantjnll's t o .9 hches as iadicated by the graph of Figure 7 . of the paaeage was divided i n t o six steps. The heat transfer coefficient Ua8 -E Knowing the heating surface required, the dlanmter of the holee could The pressure drop w811 calculated uaing equation 22C on page 128 of Thia is not dz1 exact equation for oaqreesnble flaw.McAdam, the Maoh number doea not exceed .3 It irr bel5evd that thb equathn l 8 rea80p1 is i n progress. me pressure drop ing a t an initial pressure of 600. A more accurate calculation using factors for compres8abb flow thie mthoti came out 230 ~b~/sq.in. startThis is qui b dose to the 200 lba. desired. The assumption of increasing uall teaaperatme is not neceesarw the A constant temperature of 3,O0O0 K could have been wed allbest one t o make. the uay through or say 2500' K except for the last section. advantage8 fra the standpoint of oantrol of the reaatar and would slightly reduce the ga8 preasum drop. arbitrary ratios. Has~levar, a8 the total ho& aroee 6 9 0 t h 1 is Inteded t o be constant the hole dlrll#tam should uhange by a factar UP the aquan root af 2 in order that ea& hole uan bamb into tu0 at eaab mter chango, A diagraa of' suoh a knobfag ammgwant is shawn in F i g u m 8. This oham I pattern of hdea Vhiah will e t f.frly dara #peeing avw the -8 Sauljisr witha hexagoml arrq and atill double in mm?mr I n pasing the traaritiah Another problem regarding the flow af gaa through the reaut- 38 whether or not the distribution af flaw tbraugb the psrallel passager ISehble. tamperature m y rise increasing the spmxifio vob af the gas and h~~ ita quantitiee involved are known, it ahauld be possible t o calmlate the dsgree of conditions if the flw decreases_sUghtb in one nhrnnal the $as If the eff eat is too great the flow will cost iw s to decrsasb Until the channsl h Starved and eX~w6ImW& temperature A 8 du stability existing. Arthermore, teats of fiw should provide q pGp tal verifioation of the

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graphite, say 2 inches aquare, by 8 incher long, for exsmple, supported from 2 the bottom on a graphite arch which might be made of larger piecea but c d d still be built out of bricks in the manner of a nnrsonry arch. t o take the total load of 200 lbs/sq. in. over the total cr'ws section of the lower part of the shell. Thirr design is sham on the aaooJnpanying pdllt& would havo awall tenperatwe of 3000' and an ~ntaraal-nturcr of movd hundred dagreea m, the arch not ha- any uranium in it uauld not run any hotter than the gas so tht it8 tanprature of 250O0 uauld be c l o m t o th. temperature of maximum etrsngth of graphite. The graphlte would expad nore than the shell of the reactor a8 ita average temperature w o u l d be higher and enough apace would be l e f t so that a t operating temperature it was tight againat the aide d e r aoppb radial aa well as-axialocq~ression. This would serve to hold the blocks in place. It is mpparted in turn by an intarnal flange a r d Although the iapregnated oare elemnta clom to the oxit eod The temperature drop through the graphite at t h e point of mnyinnlar pover density carnee to about 200° C. ThS8 would produce t h e d stre8686 of tbe order of. 5,000 ~ b ~ / a q .in. using the sristing data on the propsrtier of it is only applied onue, fatip does not bnve t o be acxmidered. thermal strsae w a d probablp ouaur nea e would be parallel t o the dire o tion ai' heat flaw and BO should not bave arq great effect on the heat transfer. a m baaed on the assumption of d o m a irppl.Qgnatlon of the graphits with the etresms d ten prat ~ 2 - 0drop would, af eouresm, be bmr. appears t …