The data obtained from the flight of a simplified (dummy) rocket-propelled model of the MX-656 have been analyzed to determine the booster-model characteristics and the model-alone characteristics up to a Mach number of 1.3. The data indicate that the model-booster combination is satisfactory. The model alone is longitudinally stable i n the Mach number range covered by the test (0.9 to 1.3) with the center of gravity at -15 percent of the mean aerodynamic chord. With the stabilizer setting at 0 deg. the variation of normal-force coefficient with Mach number is not large. The total-drag-coefficient variation with Mach number is not unusual. About 12 percent of the total drag at a Mach number of 1.3 can be attributed to body base drag

Mitchell, Jesse L.

Peck, Robert F.

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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
l3ElSEARC H MEMORANDUM 
f o r  t he  
A i r  Materiel  Command, U. S. A i r  Force 
RESULTS OF THE FLIGHT TEST OF A D W  OF THE 
~x-656 ROCKET-PROPELZED M0DEX.S 
By Jesse L. Mitchell  and Robert F. Peck 
SUMMARY 
The da t a  obtained from the  f l i g h t  of a s impl i f ied (dummy) rocket- 
propelled model of the  MX-656 have been analyzed t o  determine t he  
booster-model cha rac t e r i s t i c s  and the  model-alone cha rac t e r i s t i c s  up 
t o  a Mach number of 1.3.  
The da ta  ind ica te  t h a t  t h e  model-booster combination i s  
s a t i s f ac to ry .  The model alone i s  longi tudinal ly  s tab le  i n  the  Mach 
number range covered by the  t e s t  (0.9 t o  1 .3)  with the  center of 
g rav i ty  a t  -15 percent of t he  mean aerodynamic chord. With the  
s t a b i l i z e r  s e t t i n g  a t  0' t he  va r i a t i on  of normal-force coef f ic ien t  
with Mach number i s  not large .  The to ta l -drag-coeff ic ient  va r i a t i on  
wi th  Mach number is  not unusual. About 12 percent of t he  t o t a l  drag 
a t  a Mach number of 1.3 can be a t t r i b u t e d  t o  b o Q  base drag. 
INTRODUC TION 
A t  t h e  request  of t he  A i r  Materiel  Command, U. S. A i r  Force, 
f l i g h t  t e s t s  of rocket-propelled models of t he  MX-656 a r e  t o  be made, 
The models a r e  designed t o  be boosted t o  supersonic speeds by a 
Deacon rocket motor. The configuration is  qui te  unsymmetrical as 
compared t o  previous rocket-propelled models t e s t ed  by the  National 
Advisory Committee f o r  Aeronautics. Therefore a dummy model w a s  b u i l t  
and flown t o  obta in  da ta  on t h e  performance, s t a b i l i t y ,  and separat ion 
cha rac t e r i s t i c s  of the  booster-model combination, and t h e  longi tudinal  
s t a b i l i t y ,  t r im change, and drag cha rac t e r i s t i c s  of t h e  dummy alone. 
This paper presents  the  r e s u l t s  obtained from the  f l i g h t  of t h i s  dummy 
model. 
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C ONF IIXNTIAL NACA RM SL5OA07 
SYMBOLS 
normal-force coefficient ($ %) 
chord-force coefficient 
normal acceleration, feet per second per second 
longitudinal acceleration, feet per second per second 
static longitudinal stability, per radian 
base pressure coefficient 
free-stream static pressure, pounds per square foot 
base pressure, pounds per square foot 
dynamic pressure, pounds per square foot 
weight, pounds 
wing area (including that enclosed within fuselage), 
square feet 
acceleration due to gravity, feet per second per second 
MOIXL AND TEST 
Mode 1 
The basic geometry of the dummy is given in figure 1. Since the 
dummy was designed for ease of construction there are certain important 
differences between it and the MX-656 models. These differences are 
listed in table I. 
NACA RM SL5OAO7 CONFIIENTIAL 3 
For t h i s  t e s t  the weight of the model was 128.5 pounds, the 
pitching moment of i n e r t i a  was 12 -81 slug-feet square; and the center 
of gravity w a s  a t  -15 percent of the mean aerodynamic chord. A l l  
surfaces were fixed at  zero deflection re la t ive  t o  the m ~ d e l  reference 
l ine .  The booster w a s  a Deacon rocket with s tab i l iz ing  f i n s  on the 
r ea r  and a special  adapter on the  f ront  t o  transmit the thrus t  t o  the 
model. The model and booster rocket a re  shown on the Launcher ready 
fo r  f i r i n g  i n  f igure 2. 
Test 
The data  from the f l i g h t  were obtained from photography and from 
telemeter, velocity-radar, flight-path-radar, and radiosonde records. 
The telemetered data  recorded were the normal and longitudinal 
accelerations of the model and booster, and two model base pressures. 
Mach number and dynamic pressure were obtained from radar and radio- 
sonde data. The launching and boosted phases of the f l i g h t  were 
recorded by 16-millimeter motion-picture cameras. 
6 The Reynolds number of the t e s t  varied from 6.6 x 10 a t  M = 0.9 
t o  10.9 X 106 a t  M = 1.3.  
RESULTS AND DISCUSSION 
Combination Characteristics 
The booster-model combination was found t o  perform sa t i s f ac to r i ly  
during the three phases of f l i gh t :  launching, f ree  f l igh t ,  and 
separation. This performance was determined from an examination of 
the telemeter record and the 16-millimeter motion pictures.  Visual 
observation a t  the time of f i r i n g  offered additional proof. The 
maximum Mach number obtained w a s  about 1.34, and the model was f r ee  
and well away from the influence of the booster by the time it had 
decelerated t o  a Mach number of 1.3. An auxiliary f lap  fastened t o  
the booster adapter t o  give additional separating force apparently 
worked as desired. This f l ap  which remained closed during posit ive 
acceleration was triggered by deceleration and gave the booster 
additional drag and a downward pitching moment a t  the time of 
separation. 
,B 
0 
(I) 
B e 
e 
0 8  
0. 
e 
e 
Model Characteristics 
Table I l is ts  cer tain comparative geometric and structural '  d e t a i l s  
of the MX-656 models and the dummy model, and the  differences should be 
kept well i n  mind when making conclusions about the MX-656 from the 
d m  data.  The lower s t i f fness  of the dummy boom and empennage, fo r  
instance, may a f fec t  the s t a b i l i t y  and t r im adversely. The r e l a t ive ly  
th ick  wings and empennage of the  dumnry are  believed t o  have a large 
adverse influence on the  t o t a l  drag. 
Longitudinal s t ab i l i t y . -  A t  separation a pitching osc i l l a t ion  was 
induced by the difference i n  model t r im a t t i t ude  on and off  the booster. 
The osc i l ia t ion  ( f ig .  3) is  dmped; t h i s  f ac t  indicates t h a t  the model 
has dynamic and s t a t i c  s tabi1i-B~ i n  t h i s  speed range (M = 1.2 t o  l e 3 )  
and a t  the t e s t  center of gravity (-15 percent of the mean aerod;ynamic 
chord). An analysis of t h i s  osc i l l a t ion  was made by the method of 
reference 1. Since no lif t-curve-slope data  on the configuration are  
available with which t o  calculate the longitudinal damping coefficients,  
only the s t a b i l i t y  parameter Cm, was estimated. The values of C,, 
a re  given i n  figure 4 a s  a function of Mach number. As  s ta ted  previ- 
ously, the s t a b i l i t y  may be great ly  influenced by the s t i f fness  
character is t ics  of the dummy. The rather  s h q  negative increase 
i n  Cma a t  a Mach number of 1.23, however, i s  i n  agreement with 
other t e s t s ,  notably those of reference 1, which also indicate t h i s  
sudden increase i n  s t a b i l i t y  near a Mach number of 1.2. 
Longitudinal-trim change.- The longitudinal-trim change a s  
determined by the variat ion with Mach number of the normal-force 
coeff ic ient  f o r  a constant s t ab i l i ze r  se t t ing  (0') is  given i n  
f igure 5. A t  t h i s  center of gravity and t a i l  se t t ing  the t r i m  change 
near a Wch number of 1 .0  i s  small and is  i n  the nose-up direction. 
The model trims a t  very nearly zero normal-force coeff ic ient  a t  a l l  
Mach nmibers covered by the t e s t .  
Total drag.- Since the normal-force coefficients were very nearly 
zero, the chord-force coeff ic ients  obtained from the longitudinal 
accelerations a re  taken equal t o  minimum drag coeff ic ients .  Values 
of the minimum drag coeff ic ients  so determined are  shown i n  figure 6. 
The drag coeff ic ient  i s  prac t ica l ly  constsnt i n  the Mach number range 
of 1 .3  t o  1.0. A s  previously noted, it i s  believed t h a t  the actual  
models w i l l  have appreciably lower drag coefficients.  
Base drag.- The pressure was recorded a t  two points on the base, 
one i n  the plane of symmetry 2.34 inches from the bottom of the 
fuselage, and the other a t  a point corresponding t o  the center of the 
duct out le t  on the MX-656 models (about 3.3 inches from the plane of 
symmetry and 2.2 inches from the bottom). The variat ion of the base 
NACA RM SL5OA07 C 0NFII;IEMTIAL 
pressure coeff ic ient  with Mach number is  given i n  figure 7. 
A s  can be seen, both base pressure coeff ic ients  become positive a t  a 
Mach number of about 0.98. This posit ive base pressure (indicating 
negative base drag) a t  high subsonic speeds has been observed on other 
b o a t t a i l  bodies (unpublished data) and a t  present no explanation is 
available. An average base pressure coeff ic ient  was assumed from 
f igure 7 and the contribution of the base t o  the t o t a l  drag coeff i -  
c ien t  calculated. The base drag coeff ic ient  i s  plot ted i n  figure 6. 
It can be seen tha t  the base drag a t  supersonic speeds is  appreciable 
(about 12 percent of the t o t a l  drag a t  a Mach number of 1.3). 
CONCLUDING IiEMARKS 
A simplified rocket-propelled dummy model of the MX-656 has been 
flown and the following conclusions may be made from the t e s t  data: 
1. The booster-model combination performed sa t i s fac tor i ly .  
2. The dummy i s  longitudinally s table  i n  the Mach number range 
covered by the t e s t  (0.9 t o  1.3) with the center of gravity a t  -15 per- 
cent of the  mean aerodynamic chord. 
3. The longitudinal-trim change near a Mach number of 1.0 i s  a 
pitching-up tendency of small magnitude. 
4. The t o t a l  minimum drag coeff ic ient  is  very nearly constant 
between a Mach number of 1.0 and 1.3. 
5. The base drag i s  of the order of 12 percent of the t o t a l  dSag 
at  a Mach number of 1.3. 
Langley Aeronautical Laboratory 
National Advisory Committee f o r  Aeronautics 
Langley A i r  Force Base, Va. 
z' 
sse L. Mitchell 
Robert F. Peck 
Approved: Aeronautical Research Scient i s t  
Robert R e  Gilruth 
Chief of P i lo t l e s s  Aircraft  Research Division 
mcf CONFIDENTIAL 
REFERENCE 
1. G i l l i s ,  C. L., Peck, R. F., and Vitale, A. James: Preliminary Results 
from a Free-Flight Investigation a t  Transonic and Supersonic Speeds 
of the Longitudinal S tab i l i t y  and Control Characteristics of an 
Airplane Configuration with a Thin Straight  Wing of Aspect Ratio 3, 
NACA RM LgK25a, 1950. 
BBI NACA RM SL50A07 
TABU I 
DIFFEmNCES BETWEEN MX-656 MODEL AWD IXlMMY MOEL 
Constant percent Constant thickness, 
thickness, 4.5 percent 
Horizontal t a i l  Constant percent Constant thickness, 
thickness, 4.5 percent 
Vertical t a i l  Constant percent Constant thickness, 
thickness, 4.5 percent 
Construction material: 
Duralumin Duralumin 
Duralumin 
m erne 
NACA RM
 SL5O
A
07 
0.. 
.
 
e.
. 
*. 
.
 
.
 
0
 
.
 
CON FI DENTIAL 
Figure 2 .- Dummy model and booster on launcher . 
CON FI DENTIAL 
• • • ••• • 
••• •• . .. ., . . 
.. ., .. . 
• 
• 
• 
•••• 
NACA RM SL5OAO7 
Figure 3.- Variat ion of normal-force coef f i c ien t  CN with time during 
pi tching o sc i l l a t i on .  
k c h  nuniber 
Figure 4.- Var ia t ion of s t a t i c  longi tudinal  s t a b i l i t y  with Mach number. 
NACA RM S L 5 0 A 0 7  
CIu t r i m  
.8 1.0 1.1 1.2 1.3 1.4 
Mach rmPlber 
Figure 5.- Variation of trim normal-force coefficient with Mach number. 
-0- Total drag 
- Base drag 
.8 .9 1 .O 1.1 1.2 1.3 1.4 
Mach number 
Figure 6.- Variation of drag coefficient with %ch number. 
.8 09 1.0 1.1 1.2 1.4 
k c h  number 
Figure 7.- Variation of base pressure coefficient with Mach number. 
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Results of the Flight Test of a Dummy of the MX-656 Rocket-Propelled Models

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