Subsonic longitudinal aerodynamic characteristics of semiapex angle conical reentry configuratio

Phillips, W. P.

English

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SUBSONIC LONGITUDINAL 
AERODYNAMIC CHARACTERISTICS 
OF A 40" SEMIAPEX ANGLE 
CONICAL REENTRY CONFIGURATION 
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Langley Research Center 
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/ N A T I O N A L  AERONAUTICS A N D  SPACE A D M I N I S T R A T I O N  W A S H I N G T O N ,  D. C. NOVEMBER 1966  
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SUBSONIC LONGITUDINAL AERODYNAMIC CHARACTERISTICS OF A 
40' SEMIAPEX ANGLE CONICAL REENTRY CONFIGURATION 
By W. P e l h a m  Ph i l l i p s  
Langley R e s e a r c h  Cen te r  
Langley Station, Hampton, Va. 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
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I 
SUBSONIC LONGITUDINAL AERODYNAMIC CHARACTEFUSTICS OF A 
40' SEMIAPEX ANGLE CONICAL REENTRY CONFIGURATION 
By W. Pelham Phillips 
Langley Research Center 
SUMMARY 
A wind-tunnel investigation has been made to determine the subsonic longitudinal 
aerodynamic characteristics of a 40' semiapex angle conical reentry configuration 
having several nose-to-base radii bluntness ratios. The longitudinal center-of -pressure 
locations near zero angle of attack were aft of the base for all nose bluntness ratios over 
the subsonic Mach number range investigated. The only notable effect of increasing nose 
bluntness for a given Mach number was a slight rearward movement of the center-of- 
pressure location relative to that of the sharp apex configuration. 
INTRODUCTION 
Considerable aerodynamic research has been conducted by the National Aeronautics 
and Space Administration and others on low-fineness-ratio bodies of varying shapes and 
bluntness having applications as possible manned or unmanned reentry configurations. 
(See, for example, refs. 1 to 6.) Blunted conical shapes of very low fineness ratio (that 
is, 0.5 to 1.0) are particularly desirable as unmanned reentry vehicles since increases in 
cone angle and nose bluntness result in considerable reductions in total entry heating and 
the associated higher deceleration levels are acceptable for payload instrumentation. 
The present investigation was made to provide the subsonic longitudinal aerodynamic 
characteristics for a 40° semiapex angle conical reentry configuration having nose-to-base 
radii bluntness ratios of 0, 0.2, and 0.4. The investigation was conducted in the Langley 
high-speed 7- by 10-foot tunnel at angles of attack from approximately -2' to 47' over a 
Mach number range from 0.200 to 0.583. 
SYMBOLS 
The data presented herein were computed about the body axis system and nondimen- 
sionalized with respect to the maximum cross-sectional area and maximum diameter of 
the cone. The moment reference point was located at the intersection of the axis of 
symmetry with the plane of maximum cross  section. 
cA 
cA, o 
Cm 
Cma! 
cN 
No! 
C 
d 
2 
M 
NRe 
r 
R 
S 
V 
X 
-F 
Axial force 
qs  
axial-f or c e coefficient, 
axial-force coefficient at a! = 0' 
Pitching moment 
qSd 
pitching-moment coefficient, 
longitudinal stability parameter, per degree 
normal-f orce coefficient, Normal force 
qs 
normal-force-curve slope, per degree 
base diameter, 0.4064 meter 
cone length (measured from apex to station for  maximum cross  section), 
0.2426 meter 
Mach number 
Reynolds number, 
I-1 
free- stream dynamic' pressure, newtons/meter% 
nose radius, meters 
base radius, 0.2032 meter 
base area (cross sectional), 0.1297 meter2 
free- stream velocity, meters/second 
longitudinal center-of-pressure location expressed in body lengths from nose 
a! angle of attack, degrees 
2 
density of air, kilograms/meter 3 P 
kilograms 
meter- second 
I.1 viscosity of air, 
MODEL 
The wind-tunnel model of the present investigation was a right circular cone having 
a semiapex angle of 40' and a sharp-edged slightly convex base. Model drawings and a 
photograph are included in figures 1 and 2, respectively. 
The base cap of the model was formed by a spherical segment having a radius of 
0.9144 meter. Nose-to-base radii bluntness ratios (referred to cross-section radius at 
base) of 0, 0.2, and 0.4 were  made possible by the use of replaceable nose caps. 
TESTS AND CORRECTIONS 
The present investigation was  conducted in the Langley high-speed 7- by 10-foot 
tunnel at Mach numbers from 0.200 to 0.583. Average test Reynolds numbers are shown 
as a function of Mach number in figure 3. The model was tested at angles of attack from 
approximately -2' to 47' and utilized a sting-mounted, six-component strain-gage balance 
to provide force and moment measurements. A differential pressure transducer was 
used to measure pressure differences between the central region of the spherical base 
cap and the sting cavity. 
J e t  boundary and blockage corrections have been applied to the data (where appli- 
cable) in accordance with the methods outlined in references 7 and 8, respectively. The 
angle-of-attack data have also been corrected to account for sting and balance deflection 
under load. No corrections to the axial-force data were made to account for pressure 
differences across the region of the spherical base cap containing the sting cavity since 
pressure measurements indicated only insignificant corrections. 
(including base drag) a re  presented herein since the model represents an unpowered 
reentry configuration. No attempt was  made to fix transition during the wind-tunnel 
investigation. 
Total axial-force data 
RESULTS 
The longitudinal aerodynamic characteristics for the 40' semiapex angle conical 
reentry configuration are presented in figure 4 for the various nose bluntness ratios over 
the Mach number range investigated. 
3 
The positive values of Cm noted at a = 0 are equivalent to a 0.0203-meter ver- 
tical displacement of the axial-force vector relative to the balance moment reference 
point. This discrepancy is attributed to possible errors in model-balance construction 
and/or wind-tunnel installation. The discrepancies noted in' CA and Cm at a = 24' 
a r e  indicative of sting support interference on model base pressures for the sting knuckle 
setting visible in figure 2. This knuckle setting was required to obtain aerodynamic data 
at the high angles of attack (24' to 47") of the investigation. Variations of the aerody- 
namic parameters xcp/2, C N ~ ,  and CA are shown in figure 5 as a function of Mach 
number. 
The most forward center-of-pressure location (a! = 2') for  the 40' semiapex angle 
cone was found to occur at 0.132 aft of the maximum cross  section for the sharp apex 
configuration (r/R = 0) at a Mach number of 0.583. (See fig. 5.) Center-of-pressure 
locations aft of the configuration base are desirable for  unmanned reentry configurations 
in that they allow uncomplicated longitudinal payload balancing to achieve acceptable 
static longitudinal stability levels in nose-forward flight attitudes. 
Increasing the nose-to-base radii bluntness ratio from the sharp apex conditions to 
a value of 0.4 produced slight rearward movements in center of pressure throughout the 
Mach number range investigated with no appreciable effect on C N ~  and C A , ~ .  
Increasing test Mach numbers from 0.200 to 0.583 produced increases in C N ~  and 
C A , ~  and a slight forward movement of the center of pressure. 
CONCLUSIONS 
An investigation has been made in the Langley high-speed 7- by 10-foot tunnel to 
determine the subsonic longitudinal aerodynamic characteristics of a 40' semiapex angle 
conical reentry configuration having several nose- to-base radii bluntness ratios. Inves- 
tigation results may be summarized by the following observations: 
1. The longitudinal center-of-pressure locations near zero angle of attack were aft 
of the base for all nose bluntness ratios over the subsonic Mach number range investigated. 
2. The only notable effect of increasing nose bluntness for a given Mach number was 
a slight rearward movement of the center-of-pressure location relative to that of the 
sharp apex configuration. 
Langley Research Center, 
National Aeronautics and Space Administration, 
Langley Station, Hampton, Va., August 25, 1966, 
124-07-03-05-23. 
4 
REFERENCES 
1. Witcofski, Robert D.; and Woods, William C.: Static Stability Characteristics of Blunt 
Low-Fineness-Ratio Bodies of Revolution at a Mach Number of 24.5 in Helium. 
NASA TN D-2282, 1964. 
2. Penland, Jim A.: A Study of the Stability and Location of the Center of Pressure on 
Sharp, Right Circular Cones at Hypersonic Speeds. NASA TN D-2283, 1964. 
3. Armstrong, William 0.: Hypersonic Aerodynamic Characteristics of Several Series 
4. Brooks, Cuyler W., Jr.; and Trescot, Charles D., Jr.: Transonic Investig&ion. of the 
of Lifting Bodies Applicable to Reentry Vehicle Design. NASA TM X-536, 1961. 
Effects of Nose Bluntness, Fineness Ratio, Cone Angle, and Base Shape on the 
Static Aerodynamic Characteristics of Short, Blunt Cones at Angles of Attack to 
180'. NASA TN D-1926, 1963. 
, 
5.  Hayes, William C., Jr.; and Henderson, William P.: Some Effects of Nose Bluntness 
and Fineness Ratio on the Static Longitudinal Aerodynamic Characteristics of 
Bodies of Revolution at Subsonic Speeds. NASA TN D-650, 1961. 
6. Spencer, Bernard, Jr. ; and Phillips, W. Pelham: Transonic Aerodynamic Charac- 
teristics of a Series of Bodies Having Variations in Fineness Ratio and Cross- 
Sectional Ellipticity. NASA TN D-2622, 1965. 
7. Gillis, Clarence L.; Polhamus, Edward C.; and Gray, Joseph L., Jr.: Charts for 
Determining Jet-Boundary Corrections for Complete Models in 7- by 10-Foot 
Closed Rectangular Wind Tunnels. NACA WR L-123, 1945. (Formerly NACA 
ARR L5G31.) 
8. Herriot, John G.: Blockage Corrections for Three-Dimensional-Flow Closed-Throat 
Wind Tunnels, With Consideration of the Effect of Compressibility. NACA 
Rept. 995, 1950. (Supersedes NACA RM ArS28.) 
5 
I / I \  / \  I 
c(0406rad 
Axis of 
symmetry 
- Momenf 
point 
reference 
Figure 1.- Geometric characteristics of model tested. All dimensions are i n  meters unless otherwise specified. 
0 
II 
w . L 
G- c.- si 
S - 
W 
V 0
E 
a, 
c 0 V 
0 0 m
0 
c 
2 .- > 
W 
v) 
E 
N 
S m .- 
Y 
7 
0 ./ .2 .3 4 .5 
Much number, M 
.6 
Figure 3.- Variation of average test Reynolds number (based on model length) with Mach number. 
8 
(a) Variation of CN with a. 
Figure 4.- Effect of nose-to-base radii bluntness ratio on the longitudinal aerodynamic characteristics for the configuration. 
CL 
0 
M 
a200 
-4 0 4 8 12 16 20 24 28 32 36 40 44 4t 
Q ,deg 
Q305 
01405 
0583 
8 
(b) Variation of CA with a. 
Figure 4.- Continued. 
R? 
0 0  
0 0.2 
0 0.4 
(c) Variation of C, with a. 
Figure 4.- Concluded. 
12 
0 ./ .2 .3 
Mach number, M 
.5 .6 7 
.o/o 
%7 
005 
0 
Figure 5.- Summary Of aerodynamic parameters Q&, C b ,  and CA,O for various nose bluntness ratios and Mach numbers. 
NASA-Langley, 1966 L- 5160 
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Subsonic longitudinal aerodynamic characteristics of a 40 deg semiapex angle conical reentry configuration

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