Republic Aviation Presentation of Supersonic Flight Issues circa 1960

A. Kartveli R

epublic Aviation Corporation

*

.:,

$PECTRUM OI. SUPERSONIC AIRCRAT'T

Preeented at tlre Institute of Aeronautical Sciences National Meeting, San Diego, Cal. August 1-3, 1960

earch and Developnlent Division REPUBLIC AVIATION CORPORATION Farmingdale, ,L, L , New York R es

i

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:-.

SPECTRUM OT" SUPERSONIC AIRCRAtr'T by

Alexander Kartveli

I

have followed with interest the transactioni of the

first

two d.ays of this rneeting and, feel that opinions expressed., and. the

resulting diecugsions are very important in helping to forrn our national policy in regari. to tJre future of man-carrying rnilitary

air-

pLanes.

The problern of continuing or not continuiag the d.eveloprnent and production of

if any, ia,

rnilitary aircraft and what types shor:Iil be developed,

indeed., a very cornplex one and. wiII require a very thorough

analysis. one thing is obvious to rne: There will be'a continuing reguirernent for neur and irnproved. rnanned, military you nray not corrpletely agree with e>rpotrnd on the

tci you what

aircraft.

i

Some of

this statement. I arn not here to

P"o: and cons of this problem, but rathel to d.escribe

I feel are the possible design concepts that could be avail-

able in the foreseeable

future. This will, I hope, p::ovid.e an a4d;tiorr"i

input to the requirernent picture.

rn my talk today, on supersonic rnilitary airplanes co,ering the range from Mach z to zs, r will present various typical designs; ind'icating probabre perforrnance, rnilitary qualities, and pointing. out

some areae wbich require continual research and development effr>rts.

'

The rnaterial th.at r \xriu present shourd, be consid.ered as only typical designs which could be achieved in the. varioue speed. regirnes for

typical rnissions. Mogt of theee data are based. upon design

and.

anarytlcar studiee cond,ucted by the Research and Development Group at Republic Aviation Corporation. Sorne of thern have been thoroughly anal'yzed, others are sirnply possible concepts with firnd,amental

design

and technical

verificitions.

Mil.itary airplanes of tod.ay-operate in the region of Mach 2 pruq. ' This is achieved, by the century s6ries fighter-bombers and

fighters and. the B-5g bomber. The next probrem in this region of speed is to improve congid,erabry their take-off and 1ind,ing character-

isticsr esP€cially for tactical operations without irnpairing their basic rnilitary performance. :

Two tytrles of airplanes ernerge frorn this requirernent 'l

STOL and VISTOL.

rn regard to

srol, it is rny opinion tlpt thejtentative

specificatione written for this airplane by the Tacticar -Z*

Air

Cornmand.

l

ean be reasonabry inet with an airprane weighing between 50,000 and,

60,000 por:nd,s and, using two existing or nearly existing jet engines.

:

rt rnay.involve variabre geornetry or entirery retractable wings.

I strongly believe tbat with the excellent work which

NASA

has done orr the subject, problems of aerodynarnics 'and. stability can be succesefully solved within the preecribed

tirne. As to structural

and mecba.nical aspects of variable geornetry wings" r arn also con-

vince4 that they are within th'e present state of the art and do not represent a sudden jurnp in airplane technol0gy. .rt will require, howeve,r, aa utrzrost perfection in aerod.5mar.,^iic, structr:ral ahd, power prant design to achieve the required. rninimurn dragr.stabirity and" low weight neceEsary to prod,uce the desired performance.

Due to the neceasary novelty of the overall approach to the problem, this airplane

in ad'dition to exhibiting an:outstanding perforrnance at sea level will have excellent perforrnance at high altitud.e and extrelnely attractive

ferry range.

Thp

vrol type of airplane in the region

of cotrrser. a rnore involved

and. comprex

of Mach 2 pr.us is,

problern than the srol,

.

Aerod'ynarnic probleme of achieving high perforrrance are coupl.ed. with

specific problerns of vertical take-off and randing. Artificia!.ry generating the lift and, accornBlishing smooth, stable and safe transition

from zeto speed. to furl fly:ng speed. are, of course, the rnost irnportant problerns to solve. The solution should not, howeverr. conflict with the -3-

general aerod)rnamic efficiency, nor should it penalize the weight of '?he

airplane so that proper performance at sufersonic sPeed can 'be

achieved.

'

The Republic design,

aircraft. rt is a single

Ap-I00, is an example of euch.an

pLace supersonic

bomber cruising at Mach

2.3,

cagtabre

vertical-rising fighter-

of accurate bornbing r:nd.er

ar1

weather conditions frorn altitudeg of '?s1000 feet down to sea Leve1.

tr'igure 1 gives the three-view d.rawing. The airprane weight for the norrnal rnission is 38,000 pounds and has six irnproved. G.E. J-gs t,

fuserage. rts Lpngth is 67 feet 9.5 inches, wing area of 600 sguare

feet, and a height of

profile.

13

feet I0.5 inches. tr'igure z g|ve the inboard

Each lift-prod.ucing fan is fed, by two engines

side. !'9r vertical take-off

-

one on either

and randing, the gas flow of each engine

is diverted into the proper fan by a special d.iverter valve a

lift of 14,400 pounde per fan.

The vertical

and. prod.uees

lift vector of each fan

can be incrined backward by rneans of 1ouvers on the bo ttom sid,e of

the fuselage, thus producing the horizontal propelling force necessary

for transition. After the transition is accornprished., the d.iverter valve directs the e>draust gaq backward, thus creating a normal trce of propulsion. Figure 3 is the artistrs conception of the machine.

More effort should be applied to further incr

eas e the

efficiency and reliability of this tlpe of design. tr'irst, it is neces sary -

4-

to develop rrore powerful engines wiuh much greater ihrust to weight

ratio, improve the efficiency and. reduce the weight of.the lift prod.ucing fans. Thus, the number of engines will be reduced and. the weight of the power plant decreased. This is now being seriously considered. by the engine rnanufacturers.

su"oodly, research should be continued to irnprove the aerodlmamics of vertical rising and transition. Recent tests have shown that there :.s -qo,,,e loss of

take-off, a loss of lift

lift

due to gror:nd interference at

due to the forward. rnotion of the

aircraft during

the transition and a pitching rnoment due to forward. rnotion wlth fans operating.

These phenomena are prod.uced, by interference of the

vertical flow with the ground on one

sid.e and by the

very cornplex

nature of the combined, horizontal and vertical fl.ows on the other hand.

These problerns ehould be stud.ied analyticar.ry ag well as

experirnentally. Studies

conducted, by Repubtric show that these

'culties can be.overcome by proper defleetion

and. shield.ing

diffi-

of flows.

rn the region of Mach 3 great effort has been exerted by the ind,uatry in the course of the 1ast few years.

A great number of proposals.

and. designs have been

started

in the class of interceptors and fighter-bombers and bornbers; Such

aircraft as the xE-103

MachNo. of 3.2, the B-zo

designed. to a

tr

-Jr

for a Mach 3 and the F-l0g are arl exarnpres of this epeed category. 'W'e atrI know of their fate and recent re-evaluation of the designed

B-70. The general consensuB'of

opinion was and, I presrune, is.now

that fighting iirpranes in this class of speed do not give enough

tacticar and strategical ad,vaniage as cornpared to the great cost and d'evelopment tirne

the future

involved. Whether this d.ecision was right or wrong,

will show.

Going up in the scale of speedto the region of Mach 4

-

5,

a study riras rnad.e of the feasibility of an extended range, high-speed. strategic bornber in the I9ZO-I9ZS tirne period.. Figure 4 shows an

artistts conception of the aircraft using nuclear rarnjets. A rad.ius of action of 8r 500 nautical rniles was desired so that the aircraft could, be based

in continental United States and not rely on al1ied bases. Our

findings:indicated that airplanes with projected chernical fueled. propulsion systerns would not rneet the desired. requirernelt without introd'ucing the cornplicated. concept of staging. Qur solution to the

problern of long range airplanes lies with-nuctrear powered propulsiori systerns.

Figure 5 shows the three-view drarying of a Republic configuration d.esigned for Mach 4.zscruise at g5ro00 The internal arrd.ngement

is shown.in Figure

ft.

altitud.e.

6 on the inboard, profile.

It is noted that the cruise airpl.ane weighing 350,000 pound.s is powered. by two rarnjets based. on the G. E. Ac-zIO-1. nucrear engine. The aII

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internal cornpg'ession inlet, the air-ind.uction system, the nuclear ramjet reactor and the expansion noz4res are shown. rn between the two propulsion systems, the two-rnan crew shierded. cornpartrnent, electronics and armament payload, and three J -79 auxiliary rand.ing power plants are also shown. The pitot view at rand.ing is aid.ed by rn'eans of a

periscoPe. The boost systern installation for take-off is

shown on Figure 7.

rn the past, velocity incrernents of new generations of

aircraft were cornparativery srna1l. This was because even such ' increaees gave

one a decided tacticar ad.vantage. As the speed.s of

aircraft have increased, srnall incrernents in

speed neither provid.e

such an advantage, nor are they necessariry econornical. Ae one ppoceeds frorn the Mach 4

- s range, the next step appeare to be to

consider designs in the Mach Z Study of supersonic and using rarnjet propulsion

-

IO regime.

aircraft with practical lift/drag ratio

for cruise indicates that the rnaxirnurn

values of the.range parameter are rearized in the Mach No. range

around

7. l'or this

reason an ai::craft in this region of speed. has been

studied. Figure 8 gives the three-view drawing of this concept.

The

aircraft configuration essentially condists of a delta wing-body combination. The entire forebod,y serves as the rarnjet inlet and. the rarnjet rrozzLe

fills the entire

base of the

aircraft.

The low pressure d.rag is

achieved by subme::ging the useful vorume of fuselage between the

large engine inlet and rrozzle exit required. for the ramjet at Mactr 3'igure 9 gives the general arrangernent of this aircraft that useful load,, fuel landing gear

and.

Z;

and, shows

the two turbojet engines used

for take-offr land,ing and. acceleration to Mach 3 are located

between

the inlet and exit of the rarnjet.

The turbojet inlets are subrnerg6d within the ramjet inlets and bypass ducting

is

provid.ed. so that the

can be used as afterburnera

rarnjet cornbustion charnber

for the turbojet. The turbojet inlet is

closed and. the turbojets are inoperative at Mach 3; Ttre ramjet engines

provide the thrust for acceleration to and cruise at Mach ?.

f igure l0 gives the artistf s view of the airplane.

The rnajor problern for such an aircraft is. the high aerodynarnic heating rates associated. with Mach

?. It appears to be feasible

to solve the high ternperature problern by fly.ng at high altitude in ord.er to reduce the heating rate and d.esigning a rnulti-layer structgre with high ternperature insulated, skin cooled, by rad,iation

If 'the present state of knowled.ge in structuraL engineering' and.

metallurgy is assurrred, corrputations show that a Jp-6 fueled,

ramjet aircraft

oJ

this conception can carry 2, oo0 pounds store to

a

I

radius of 21000 nauticat miles at an altitudE of lz0r000 feet,

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and.

will

:

.--

!1

weigh approximatery 140,000 pound's.

structural concepts are ad.vances in the next

used.

rf, however, very

ad.vanced

together with probable rnetallurgical

five years the rad.ius courd. be increased. by

approxirnately 4010. Such an aircraft could be

used.

for off-shore

bombing and long reconnaissance missions. 'where do we go frorn here with a rrran-c4rrltng airprane

?

rs it necessaryto go faster and higher with such a vehicle? rf so,.is ^r

'

t technologically possibLe?

and ultirnately space

ships.

We know that frorn Mach Z5.O appro:<i-

VIouId,

it serve a useful purpose and what

would.it take for an airplane to approach thig dornain and,, perhaps, to

join it? In order to clarify the subject, we have studied. a concept of

It consists of a lifting

rnachine with chernical air-breathing

power plant, ca.rrying substantial rnilitary Load, capabLe of taking; off

from the gror:nd, accelerating to orbital speed, orbiting arognd. the earth and landing on earth when desired. l

our study was rather general

and was intend.ed. orrly to

Prove the validity of the idea and the basic feasibility of the vehicle.

The design

is based uPon the assurnption that a supe,rsonie

combustion engine can be d.eveloped. The problerns of subsonic cogrbustion at high flight Mach nurnbers have been extensively investigated.

-9-

and show good

promise. The super'sonic combustion is not as far

advanced in theory and d.everoprnent as can be seen

in current ritera-

ture. Nevertheress, the aiarysis ind,icates tbat a good. performance may be available using a supersonic cornbustion scherne similar to that presented by propulsion in

Dr. Ferri at the Mi1an rneeting

April

on air-breattring

1960.

We have done e>qploratory analyses on a supersonic i

i

cornbustion scherne for producing thr.ust in the hy;rersonic flight range :

frorn Mach 7 * 25 and ascertained that there is a good theoretical

i I

possibility to prod.uce thrust at these speed.s. Extensive gas cycle cornputatione have been made and ehow that thrust can be obtained, with high specific irnpurses. r'igure tI shows a typical curve of

specific irnpulse vs. Mach nurrber computed, for this power plant. 'we have studied the trajectories along which such a

.fuel iequirementg and, rnaneuver capability.

I will very rapidly describe this

concept.

tr'igure 12 shows a three-rriew d.rawing of the machine which gives an idea of configuration, size and weight of the vehicle whic[ has been and

studied. As you can see, it is an unusuELl cornbination of a wing

lifting body having a horizontar projected area of g,500 sq. ft.

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rt is

1?0

ft.

Ipng and 33 ft.

high. weight analysie

shows 400,000 .[bs.

gross weigh-t,:of which 200,000 rbs. is liguid. hydrogen fuel

and.

35,000 Ibs. rnilitaty payLoad.

tr'igure 13 shows the inboard profile of the airplane. The forward portion of the airprane is shaped in the forrn of an open air intake which conxPresses the outsid.e air and. supplies

it to four ramjet

cornbustion charnbers located in the aft portion of the fuserage. tr our

turbojet engines are instarled insid.e tJ.e fuselage. They are fed by the ernbranchment from the sarne air intake and, can use the combustion chamber of the rarnjets for afterburning. Location of the usefi:I and.

1oad.

fuel is also shown.

The inboard' profile has been stud.ied, for space volurne an6

weight for feasibility purposes.

r'igure

:

14 givea the

artistrg concept o{ the design.

Take-off is accornplished. by four hydrogen burning J-58 type engines and takes approxirnately 8, ooo ft. to clear a 50 ft. obstacle.

The airplane is then accelerated to Mach 3.0 by.the same engines. At

this time, the rarnjets are ignited,

and. using

liquid hyd.rogen.as fuel.in

a subsonic cornbustion rnode accelerates the airprane to Mach 2.0. tr'rom there the same rarnjets, using supersonic tytrle of combustion, continues to accelerate the ship up to orbital verocity reaching an

altitude

of. 20O,000.

ft.

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:

$$gure 15 Ehows that a variety of flight paths can be ,

within the outer fringes of the atr:rosphere at an altitud e of

miles.

26O,O0O

ft.

The upper left-hand trajectory shown in Figure 15 corresponds

to an essentially consta'nt altitude circurar orbit at ?;60,oo0 ft, rnaxirnurn

altitude. This trajectory is obtained.

2oo, o0o

by accelerating to approxirnately

ft- with z\o of. the initial fuel weight rernaining. At this point,

a pulI-up

is effected and one cornplete circuit can be accornplished by using two-thirds of' 2To of the initial fuel weight d.uring the clirnb frorn z00r 0o0 to 260,000 ft. The rernaining one-third, is used for the cruise portion. on the other hand., if the airprane is pulred. up to z?s,ooa ft. it is possible to rnake two cornplete circuite,

and,

if orbit altitudes of 300,000

" ft- are obtained three comprete circuits of the earth can be mad.e.

Figure

15 correspond's to two skips to an apogee of about 200 rniles with

approximately two cornplete circuitg of the

earth. This rnaneuver

accornplished by again using two-thirds of the fuel for pulling up

is

and.

rnaintaining constant clirnb speed, and the rernaining one-third for the cruising portion of the ftight.

The rernaining trajectory in the rower central portion of

tr'igure 15 corresponds to a trajectorywhich has an apogee of I,000

rniles' This trajectory is obtained by overspeed.ing frorn circular orbit -L?-

velocity by +,000 ftlsec and then performing skip maneuver. During 1 the tirne that the vehicle is attaining 1r 000 ft/sec excess velocity over

orbit velocity the pilot rnust adjust th6 wing angle of attack to rnaintaiu a congtant altitude. This implies that the attitud,e of the vehicle wiII be in a r-elatively negative position to that during the

orbit velocity

condition where.the centrifugal force is eqr:aI to the 1ift capability of the vehicle- I"or this condition

it is neceBsary that ad.ditional fuel be

provided' by adding 20, o0o por:nd,s to the overall fuel weight. This rrrust co:rle by replacing sorne of the useful load in terrns of ad.d.itional fuel.

rn addition, the vehicle has the capability, since it is flying

in an atrnosphere, to change the prane of its orbit by perforrning a rol1 maneuver. At th'ese altitudes within the atmosphere the vehicle has enough control to maneuver, change'the

the size of the

trajectory, increase or decrease

orbit. In addition to the orbital capabilities, the *ehicle

has a rnost irnportant rnilitary characteristic to take-off and land. at

suitable

airfields. rt

'

can rerease a sma1l parasite

shown on the inboard

profile (tr'igure

aircraft which was not

13) and which can be used.

for local

tactical rnissions. This small ai'rcrh.ft provides a weapon systern capability which can meet requirernents discussed. by the Air Force.

!'rorn the prelirninary st.d,ies which we have rnade, it aPPears that this vehicle has so many attractive potentialities an6

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il t,

:

global apprlcatlons that,a more d.etailed. bagic research is very much in ord,er.

of

course there are many ad,vanced. an. challenging problerns connected with this concept. There are, in the first place, probrems of rarnj-et operation and phenornena of subgonic and. supersonic cornbustion.

'

The possibilities of application of supersonic cornbustion

are so attractive that a continued and

extend.ed,

research oo atl" subject'

should be undertaken.

Another chalrenging probrern is that of .right and ad.equate

structural design capabre of withstand.ing high ternperature. con_ siderable research and, d.everoprnent work is going on at present in the scidntifi"c worrd. and. in industry on this subject and is rnostry in connection with the ad.vanced. subjects of agtronautics.

rt is

::easonaHle Yeevaresg to assurne that the

results of this wbrk wirl

directly applicable to the.subject in questioa. structural assumptions in this design are of the same order of rnagnitud.e ae those for large re-entry bodies consid.ered for r,nar work. be

I have

gone over the spectrurn of supersonic airplanes and.

I feel that the nran-c?.fryang _ r___o airplane ___r-e..v has .Ee stil1 rnuch to rlllff;rl t(, oIIer -b{r offer ln. in the near and fariway future. The establishrnent of future'rnanned rnilitary ;

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a!,rcraft rcqrdrernonte ls a prlvllegc whlcb, belonga to bigh ranking profeagional lnilitary people who have military experience

and,

Unfortunately now the research and, d,eveloprnent work in the fietrd, of airplanes is practlcally at a eta,nd,sti1l.

:

Consequeutly,

:'

if at any time in tbe future

due to

tactical,

etrategical er politJ.cal coasi.deratione and especia[y due to'un]snown intentioas of the proepective enemy ehould tJrere be a need for

l

dvaacell airplanee

, it will take us mgre

money and much Longer time.

Creative work must go on to avoid thie ernbarraasing aad., perbaps,

tragic eituation in the future.

-.I E-e

RAC

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