A flight test was made a t high subsonic, transonic, and supersonic speeds and at high Reynolds numbers to determine the zero-lift drag of a 1/14-scale model of the Northrop MX-775B pilotless aircraft with small small body. The triangular wing of the model had 67.5 deg leading-edge sweep and 15 deg. trailing-edge sweep, The wing airfoil sections were modified NACA 0004 sections. The drag coefficient based on total wing area was 0.0107 at Mach number 1.60. At transonic speeds the maximum drag coefficient was 0.0125. The force-break Mach number was 0,98

Arbic, Richard G.

Gillespie, Warren, Jr.

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NACA RM SL5OH18 
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
RESEARCH MEMORANDUM 
f o r  the 
A i r  Materiel Command, U, S. A i r  Force 
LARGE-SCALE FLIGHT MEASUREMENTS OF ZERO-LIFT DRAG AT MACH 
NUMBERS FROM 0.90 TO 1.95 OF A -- I SCALE MODEL OF THE 14 
NORTHROP MX-775B PILOTLESS AIRCRAFT WITH SMALL BODY 
By Warren Gillespie,  Jr. and Richard G. Arbic 
A f l i g h t  t e s t  was made a t  high subsonic, transonic, and supersonic 
speeds and a t  high Reynolds numbers t o  determine the zero- l i f t  drag of 
scale  model of the Northrop MX-775B p i l o t l e s s  a i r c r a f t  with small 
a z- 10 body. The t r iangular  wing of the  model had 67T leading-edge sweep 
and 15' trailing-edge sweep, The wing a i r f o i l  sections were modified 
NACA 0004 sections. 
The drag coeff ic ient  based on t o t a l  wing area was 0.0107 a t  Mach 
number 1.60. A t  t ransonic speeds the maximum drag coeff ic ient  was 0.0125. 
The force-break Mach number was 0,98. 
INTRODUCTION 
A t  the request of the  A i r  Materiel Command, U. S. A i r  Force, the 
Langley P i lo t l e s s  Aircraf t  Research Division i s  invest igat ing the  aero- 
dynamic charac ter i s t ics  of the Northrop MX-77SB p i l o t l e s s  a i r c r a f t  through 
the  use of rocket-propelled scale  models. Continuous data a re  obtained 
from high subsonic t o  supersonic speeds a t  high Reynolds numbers, 
This paper presents zero-lift  drag data f o r  a -- I scale  model of 14 
the Northrop MX-77SB p i l o t l e s s  a i r c r a f t  with small body. The Mach number 
range was 0.90 t o  1.95. Reynolds number, based on the wing mean aero- 
6 dynamic chord of 2.31 f ee t ,  varied from 8,s x 10 t o  29.0 x lo6, 
CONFIDENTIAL NACA RM SL50~18 
C~ drag coefficient (Drag/qS) 
C N normal- -force coefficient (~ormal f orce/qs) 
9 dynamic pressure, pounds per square foot (PV~/~) 
P air density, slugs per cubic foot 
V velocity, feet per second 
M Mach number (V/c) 
c speed of sound, feet per second 
R Reynolds number (PVE/~) 
P coefficient of viscosity, slugs per foot-second 
S wing plan-form area (including area within the body), 
5.61 square feet 
- 
c wing mean aerodynamic chord, 2.31 feet 
MODEL AND TESTS 
The model of the present test was a Z& - scale model of the 
A 4  
Northrop MX-775~ pilotless aircraft with small body. The model was 
designed to obtain zero-lift drag information during the coasting flight 
of the model. 
The body and wing profile coordinates and the general arrangement 
of the test configuration are presented in table I and figure 1, 
respectively. Photographs of the model and model-booster combination 
are shown in figures 2 and 3. The body of the model had a fineness 
ratio of 15.6 with body frontal area 1,27 percent of the wing area, 
, n 
The triangular wing had 67$- leading-edge sweep, lSO trailing-edge sweep 
and modified NACA 0004 airfoil sections in the streamwise direction. 
The wing chord plane was 1 inch below the body center line and parallel 
to it. The vertical tail had O0 sweep at the SO-percent-chord line, a 
taper ratio of 0.23, and 3-percent-thick symmetrical diamond airfoil 
sections which were modified by the addition of a constant thickness 
CONFIDENTIAL 
NACA RM ~ ~ 5 0 ~ 1 8  CONFIDENTIAL 3 
of 0.03 inch along the  chord on each side from the chord plane. The 
resul t ing thickness r a t i o s  of the  root and t i p  sections of the v e r t i c a l  
t a i l  were 0.037 and 0.060, respectively. 
The model was of composite wood-metal construction and was 
instrumented with a two-channel telemeter and two accelerometers. The 
accelerometers were mounted t o  measure normal and longitudinal forces. 
There was no sustainer  rocket i n  the  model. 
Figure 3 shows the  model and external booster i n  the launching 
posit ion of 76O. An ABL Deacon rocket motor was used which delivers 
approximately 6200 pounds thrus t  f o r  3.2 seconds. 
Velocity was obtained from the  Doppler radar and .by integrat ion of 
the data from the longitudinal accelerometer. Drag was obtained 
d i r ec t ly  from the longitudinal accelerometer data and by d i f fe rent ia t ion  
of the  Doppler determined velocity-time curve. Normal force  was obtained 
f ron  the normal acceleroneter. Trajectory and atmospheric data were 
obtained from the radar tracking uni t  and by radiosonde observations. 
The accuracy of the r e su l t s  i s  estimated t o  be: 
Mach number . . . . . . . . . . . . . . . . . . . . . . . . . .  k0.010 
CD . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  .*0.0005 
cN . . . e . . a e . a . e e . . . . . . . . . . . . . . . .  &oe020 
RESULTS AND DISCUSSION 
Curves of drag coeff ic ient ,  Reynolds number, and normal-force coef- 
1 f i c i e n t  against Mach number a r e  presented i n  figure 4 f o r  the = - sca le  
Northrop MX-77SB p i lo t l e s s  a i r c r a f t  model with small body, It i s  seen 
from the curve of normal-force coeff ic ient  against  Mach number t h a t  the  
drag data were obtained very near t o  the desired zero- l i f t  t r i m  condition. 
The curve of drag coeff ic ient  against  Mach number of f igu re  4 shows 
tha t  the Northrop MX-775B small-body configuration has a remarkably low 
supersonic drag coeff ic ient ,  The drag coeff ic ient  f o r  t h e  model was 
0.0107 a t  Mach number 1.60. A t  transonic speeds the maximum drag coef- 
f i c i e n t  was 0.0125. The drag coeff ic ient  had a gradual r i s e  with Mach 
number, s t a r t ing  a t  M = 0.93 and broke sharply a t  M = 0.98. 
The drag of the  model t e s t ed  is  compared i n  f igure 5 with the  
minimum drag of two similar wing-body combinations a t  high values of 
Reynolds number. The model of reference 1, which had a body of fineness 
r a t i o  10 and a 60° de l ta  wing with NACA 65~003  a i r f o i l  sections, has a 
lower subsonic drag coeff ic ient  than the model of the present t e s t ,  A t  
CONFIDENTIAL 
4 COXFIDENTIAL NACA RM SLs0~18 
supersonic Mach numbers the  model of reference 1 and the PK-775B model 
have very nearly equal values of minimum drag coefficient.  The model 
of reference 2, which had a body of fineness r a t i o  11.3 and a 63' de l ta  
wing with 5-percent-thick double-wedge a i r f o i l  sections, has a r e l a t ive ly  
high subsonic drag coefficient.  
In  order t h a t  a comparison could be made a t  the  value of bodymng 
s i z e  of the  Northrop MX-77SB t e s t  model, the  drag data  of f igure 6 were 
p lo t ted  against  r e l a t ive  body-wing s ize ,  On t h i s  basis  the Northrop 
MX-775B model has a higher minimum drag coeff ic ient  a t  both subsonic 
and supersonic Mach numbers than the model of reference 1. The t e s t  
poifits of f igure  6 a t  body-wing area r a t i o  of 0.0612 a re  from unpublished 
data  f o r  a model ident ica l  t o  the model of reference 1, but having one- 
half  the wing area. 
CONCLUSIONS 
A t  a Mach number of 1.60 the  minimum drag coeff ic ient  was 0,0107. 
A t  transonic speeds the maximum drag coeff ic ient  was 0.0125. The force- 
break Mach number was 0.98. 
The drag coeff ic ient  was found t o  be very low throughout the  Mach 
number range of the t e s t .  
Langley Aeronautical Laboratory 
National Advisory Committee f o r  Aeronautics 
Langley A i r  Force Base, Va. 
Warren Gillespie,  Jr . 
Aeronautical Research Scient i s t  
Richard G. Arbic 
Aeronautical Engineer 
Approved : 
Robert R. Gilruth 
Chief of P i lo t l e s s  Aircraf t  Research Division 
GMF 
CONFIDENTIAL 
NACA RM SLSOH18 CONFIDENTIAL 
1. Nelson, Robert I,.: Large-Scale Flight Measurements of Zero-Lift Drag 
a t  Mach Numbers from 0.86 t o  1.5 of a Wing-Body Combination Having 
a 60° Triangular Wing with NACA 6SA003 Sections. NACA RM L5OD26, 
1950. 
2, Edwards, George G., and Stephenson, Jack D.: Tests of a Triangular 
Wing of Aspect Ratio 2 i n  the  Ames 12-Foot Pressure Wind Tunnel. 
I - The Effect of Reynolds Number and Mach Number on the Aero- 
dynamic Characteristics of the  Wing with Flap Undeflected. NACA 
RM A7KOS9 1947 
CONFIDENTIAL 
CONFIDENTIAL 
TABLE I 
BODY AND WING AIRFOIL-SECTION O I N A T E S  
MACA RM S L 5 O H 1 8  
CONFIDENTIAL 
A l l  dimensions in inches 
0.030 Stee l  plates over 
3 % diamond section 
A-A 
Typical fin section 
Figure 1.- General arrangement of -- scale model of Northrop MX-775B 14 
p i lo t l e s s  a i r c r a f t  with small body. 
ma NACA RM ~ ~ 5 0 ~ 1 8  
0 0  D 
0. 8 
oboe 
B 
oeoe 
s 
seem 
(a) Side view. 
I Figure 2.- Photographs of - -  sca le  model of Northrop MX-775B p i l o t l e s s  14 
a i r c r a f t  with sinall body. 
CONFIDENTIAL 
. . 
(b) Bottom view. 
L-64658 
Figure 2.- Concluded. 
T 
1;-64694- 
Figure 3,- Model and booeter combination in launching attitude. 
NACA RM SL50H18 
0 Telemeter 
Doppler Radar 
I I I I I I I I I I 1 
Figure 4.- Variation of drag coeff ic ient ,  Reynolds number, and normal- 
1 force coeff ic ient  with Mach number fo r  - - sca le  Northrop MX-775B 14 
small-body model. 
CONFIDENTIAL 
ee MACA FM SL50~18 
e e  
.. e 
80. 
Figure 5.- Variation of minimum drag coefficients of triangular wing- 
body combinations at high Reynolds nuniber with Mach number. 
NACA RM SL50H18 for  A i r  Materiel Connnand, U. S. A i r  Force ent i t led "Large-Scale 
Flight Measurements of Zero-Lift Drag a t  Mach Numbers from 0.9 t o  1.95 of 
a $-Scale Model of the Nmtbrop MX-77% Pilot less  Aircraft with SmaU Body," 
By Warren Gillespie, Jr. and Richard G. Arbic. 
Figure 6 of t h i s  paper should be replaced by the corrected figure below. 
60' Delta, reference 1 and unpublished data 
0 63' Delta, reference 2 
0.02 
0.0 I 
'%IN 
0 
0 0.0 1 0.02 0.0 3 0.04 0.05 0.06 
Ratio of body maximum cross-section area to total  wing area. 
0 
0 0.01 0.02 0.03 0.04 0.05 0.06 
Ratio of body msxi ID~m cross-3ection area to total  wing area. 
(b) mch number 1.53. 
Figure 6. - Variation of mb. w i m w  drag. ~ o e f  firilent with body-wing area ratio. 
C O W  IIXXTIAL 
0 0.0 1 0.02 0.0 3 0.04 0.05 0.06 
Ratio of body maximum cross-section area to total wing area. 
o Present Test 
60" Delta , Ref. I and unpublished datd 
0 63" Deltd , Ref. 2 
( a )  Subsonic Mach nuuiber. 
60" Deltd, Ref. I and unpublished data 
-0- 
/- 
/- 
-.--- 
=Kjz&7 
I I 
r-7 
0 0.0 1 0.02 0.03 0.04 0.05 0.06 
Ratio of body maximum cross-section area to total wing area. 
/LI 
A 
,'4 --v 
-- - 
(b) Mach number 1.53. 
-- 
Figure 6.- Variation of minimum drag coeff ic ient  with body-wing-area 
r a t i o .  
Restriction/Classification Cancelled
Restriction/Classification Cancelled


Large-Scale Flight Measurements of Zero-Lift Drag at Mach Numbers from 0.90 to 1.95 of 1/14-Scale Model of the Northrop MX-775B Pilotless Aircraft with Small Body

Large-Scale Flight Measurements of Zero-Lift Drag at Mach Numbers from 0.90 to 1.95 of 1/14-Scale Model of the Northrop MX-775B Pilotless Aircraft with Small Body

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