Static stability tests in hypersonic arc tunnel on blunted cone at mach 2

Harrison, E. F.

English

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NASA TN D-1508
TECHNICAL NOTE
D- 1508
STATIC STABILITY TESTS IN THE
LANGLEY 24-INCH HYPERSONIC ARC TUNNEL ON A BLUNTED CONE
AT A MACH NUMBER OF 20
By Edwin F. Harrison
Langley Research Center
Langley Station, Hampton, Va.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON December 1962
https://ntrs.nasa.gov/search.jsp?R=19630000754 2020-03-24T06:48:52+00:00Z
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
TECHNICAL NOTE D-1508
STATIC STABILITY TESTS IN THE
LANGLEY 24-1NCH HYPERSONIC ARC TUNNEL ON A BLUNTED CONE
AT A MACH NUMBER OF 20
By Edwin F. Harrison
SUMMARY
An experimental investigation has been conducted in the Langley 24-inch i<_er-
sonic arc tunnel to determine the static longitudinal characteristics for a blunted
9° semivertex angle cone at a Mach number of 20 at angles of attack from -2.5 °
to 12.5 ° . The model with a spherical-segmented nose and a truncated conical base
was a i/7-scale Scout payload. The investigation comprised the first force tests
made in the Langley 24-inch hypersonic arc tunnel. This facility is an arc-heated,
hypervelocity, blowdown (hotshot) wind tunnel. For operation during the present
tests_ nitrogen_ initially confined in a reservoir, was heated and pressurized to
approximately 3,000 ° K and 750 atmospheres by generating an electric arc in the
reservoir. The heated gas then expanded through a conical nozzle to the test sec-
tion and into a vacuum chamber.
A compilation of the data of the present tests with other wind-tunnel data at
Mach numbers of 6.8, 9.6, 17, 17.3, and 24 is presented. An analysis of the exper-
imental results showed that for all Mach numbers from 6.8 to 24 (except the free-
flight tests at a Mach number of 17 at angles of attack up to about 4o), the model
was longitudinally stable about the 44-percent body-length station. The normal-
force coefficient generally decreased slightly with increasing Mach number. Mach
number had small effects on the center-of-pressure location which tended to be
approximately at the 50-percent body-length station.
INTRODUCTION
A current project, Scout, which is in support of the space research program,
concerns the investigation of the thermodynamic effects of the upper atmosphere
on a high-velocity vehicle. In an effort to determine the static longitudinal
stability characteristics of the Scout payload configuration, several hypersonic
wind-tunnel tests were made.
The Scout payload configuration consisted of a spherical segmented nose fol-
lowed by a short cylindrical section and a 9° semivertex angle cone with a trun-
cated conical base.
The tests at a Machnumberof 20 were conducted in the Langley 24-inch hyper-
sonic arc tunnel. Normal-force and pitching-moment data were obtained at angeles
of attack ranging from -2.5 ° to 12.5°. In addition_ somedata from tests madein
other wind tunnels at Machnumbersof 6.8, 9.6 (both unpublished results), 17,
17.3, and 24 (refs. i, 2, and 3, respectively) are presented herein.
SYMBOLS
The normal-force and pitching-moment coefficients are referred to the body
axes, and the reference center of momentsis located at 44-percent body-lengt_i
station.
A
%
CN
dC m
dC N
d
M
P
q
R
T
t
v
x/z
u.,
maximum body cross-sectional area, sq in.
pitching-moment coefficient,
Pitching moment
qAd
normal-force coefficient,
Normal force
rate of change of pitching-moment coefficient with normal-force
coefficient
maximum body diameter, in.
Mach number
pressure, ib/sq in.
dynamic pressure, ib/sq in.
Reynolds number
temperaturej OK
tunnel run time, milliseconds
velocity_ ft/sec
center-of-pressure location from nose of model
angle of attack, deg
density, amagat units (a relative scale referred to density
at 0° C and i atmosphere of pressure; for nitrogen,
i amagat = 0.00242 ib-sec2/ft 4)
Subscripts:
i
t,l
t,2
free-stream condition ahead of normal shock
reservoir condition
stagnation condition behind normal shock
MODEL
The model tested in this investigation consisted of a spherical segmented
nose followed by a short cylindrical section and a 9° semivertex angle cone as
shownin figure i. The configuration is terminated by a truncated 40° half-angle
conical base section. A photograph of the model is shownin figure 2. The model
tested at a Machnumber of 20 was designed to feature a light, strong structure.
The light weight was required to maintain low momentsof inertia because rela-
tively short tunnel run time necessitated rapid balance response. The blunt-nosed
conical section of the model, constructed of magnesium,had a 0.020-inch wall
thickness, and the conical base was madeof balsa wood. The complete model weighed
about 0.i pound.
APPARATUS
The tests at a Machnumberof 20 were conducted in the Langley 24-inch hyper-
sonic arc tunnel. This facility is an arc-heated, hypervelocity, blowdownwind
tunnel, and it is essentially the samein design and operation as the hotshot tun-
nel described in reference 4. A schematic diagram and a photograph of the present
tunnel are shownin figures 3 and 4, respectively. The major componentsof the
tunnel include a two-million-joule capacitor electrical-energy storage system with
a charging unit, an arc-heated reservoir with a volume of approximately i00 cubic
inches, a i0 ° total-angle conical nozzle varying in diameter from 0.i00 inch at
the throat to 24 inches at the test section, an approximate 200-cubic-foot vacuum
chamber, and a vacuum-pumpsystem.
A two-component, internal, high-frequency response, strain-gage balance was
used to obtain normal-force and pitching-moment data on the model. A photograph
of the balance is shown in figure 3- This balance was designed with frequency
response of about 1,000 cps which is considerably higher than the conventional
wind-tunnel balance. The support system reduced the natural frequency to approx-
imately 350 cps. The high-frequency response was necessitated by the short tunnel
run time of about 20 to 50 milliseconds. The electrical signal from the balance
is transmitted through a 20-k$1ocycle carrier system and a low-frequency galvanom-
eter element to a consolidated oscillograph recorder.
A single-pass, Z-arrangement schlieren system with a continuous light source
and a Fastaxmovie camera was used for each run. The camera speed was approxi-
mately 4,000 frames per second during a run.
3
A description of the Langley ll-inch hypersonic tunnel for which the unpub-
lished tests are presented herein can be found in reference 5. A calibration of
the tunnel at Mach numbers of 6.8 and 9.6 for air is contained in reference 6.
TESTS AND ACCURACY
For the present tests the arc chamber was charged initially with nitrogen to
a pressure of approximately 1,000 ib/sq in. The nozzle, test section, and vacuum
chamber were evacuated to a pressure of approximately 5 microns of mercury. Then
about 700,000 joules of electrical energy at approximately 4,500 volts were
released across the main electrodes in the arc chamber. This energy heated and
pressurized the nitrogen to approximately 3,000 ° K and 750 atmospheres. The
heated gas then vaporized or burst the Mylar diaphragm near the throat and
expanded through the conical nozzle to the test section and vacuum tank. In the
test section a quasi-steady flow was established with a Mach number of approx-
imately 20 for about 20 to 50 milliseconds.
At the present tim% a very limited range of test conditions has been real-
ized in the Langley 24-inch hypersonic arc tunnel. However, the facility has a
large potential capabilities envelope for simulation of Reynolds numbers and Mach
numbers which are presented in figure 6.
Prior to the present tests, a calibration of the tunnel was made in which the
initial reservoir pressure, reservoir pressure after the arc discharge, and pitot
pressures on a survey rake in the test section were measured. Then, with these
conditions, all other reservoir and free-stream thermodynamic properties were
determined by using the data-reduction program from reference 7- This method is
based on nitrogen in equilibrium. From the calibration data, a Mach number of
20 ± 0.5 was determined for an 8-inch-diameter test-section core at tunnel axial
stations where test models would be located.
In calculating the test-section conditions for the present tests, arc-chamber
pressure was measured and a corresponding average pitot pressure was obtained from
the calibration data. Typical results are listed in table I. A typical oscillo-
graph pressure record is shown in figure 7(a).
A strain-gage-balance oscillograph record is presented in figure 7(b) which
shows the normal-force and pitching-moment traces during a run. Values are read
by averaging the envelope of each trace.
Two typical schlieren photographs of the model at angles of attack of 0o
and 5° are presented in figure 8. In these photographs, the bow wave around the
model can be seen.
Uncertainties involved in repeatability of balance and readability of the
oscillograph records caused maximum probable inaccuracies in CN of ±0.016 and
in Cm of i0.005 for the Mach number 20 data. The angle of attack was set
within ±O.1 °.
4
RESULTS AND DISCUSSION
Experimental normal-force and pitching-moment coefficients for angles of
attack from -2.5 ° to 12.5 ° on a blunt-nosed cone have been obtained at Mach num-
ber 20 for the present investigation and have been compiled with other wind-tunnel
data of Mach numbers 6.8, 9.6, 17, 17.3, and 24. These test results are presented
in figures 9 to 12. For this same Mach number range, the center-of-pressure loca-
tion and dCm slopes for the model are shown in figure 13. Reynolds numbers fordCN
all the tests are given in table II. In analyzing the results, no attempt was
made to show the effects of the different test media on the aerodynamic character-
istics of the configuration.
Normal-Force Coefficient
Variation of normal-force coefficient with angle of attack for a blunt-nosed
cone in the Langley 24-inch hypersonic arc tunnel at Mach number of 20 with nitro-
gen as the flow medium is shown in figure 9. All data points were read at a tun-
nel run time of 25 milliseconds. It can be seen, however, in figure i0 where the
data were read every 2 milliseconds from 15 to 35 milliseconds that the effects of
time on CN are small. In general, for a particular angle of attack, the normal-
force coefficient decreased slightly as Mach number increased (see figs. ii
and 12).
Pitching-Moment Coefficient
Variation of pitching-moment coefficient with angle of attack at a Mach num-
ber 20 is presented in figure 9. Pitching-moment-coefficient data, like normal-
force-coefficient values, were read at a run time of 25 milliseconds and as shown
in figure i0 varied only slightly with run time. At Mach numbers of 6.8, 9.6,
17.3, 20, and 24 the pitching-moment coefficient (fig. ii) indicates that the
model was longitudinally stable about the 44-percent body-length station. How-
ever, the free-flight tests at Mach number of 17 showed a region of slight static
instability about the 44-percent body-length station up to an angle of attack of
about 4 ° . Since absolute values of the pitching-moment coefficient were small
for the tested angles of attack, small or no Mach number effects (see fig. 12)
were observed within the accuracy of the data.
Center-of-Pressure Location and Stability Derivative
The center-of-pressure location and the longitudinal-stability derivative
dC m
are plotted against Mach number for several angles of attack in figure 13.
dC N
The data indicate that the Mach number had small effects on the center-of-pressure
location and that the center-of-pressure location tended to be approximately at
the 50-percent body-length station. For most Mach numbers the dC___mmvalues became
dC N
dCm
more ne_ative with increasing angle of attack. It is clear from the _ plotdCN
that _'or most Machnumbersthe model was stable through the angle-of-attack range
of the tests.
CONCLUSIONS
Wind-tunnel tests have been madeon a blunt-nosed cone at Machnumbersof
6.8, 9.6, 17, 17.3, 20, and 24. An analysis of these tests has led to the fol-
lowing conclusions:
i. At Machnumbers from 6.8 to 24 (except the free-flight tests at Machnum-
ber of 17 at angle of attack up to about 4o), the model was longitudinally stable
about the 44-percent body-length station for angles of attack from -2.5 ° to 12.5°.
2. The normal-force coefficient generally decreased slightly with increasing
Machnumber.
3. Machnumberhad small effects on the center-of-pressure location which
tended to be approximately at the 50-percent body-length station.
Langley ResearchCenter,
National Aeronautics and Space Administration,
Langley Station, Hampton,Va., August 22, 1962.
REFERENCES
i. Kirk, DonnB., and Miller, Robert J.: Free-Flight Tests of Fifth-Stage Scout
Entry Vehicle at MachN_nbers of 5 and 17. NASATN I)-1425, 1962.
2. Pope, T. C.: ChanceVought Hypervelocity Wind Tunnel Force Tests of a Five
Stage Scout Payload Re-Entry Configuration. Rep. No. H_T - TEST13
(Contract No. NAS1-1438), Vought Astronautics, ChanceVought Corp.,
Jan. 24, 1961.
3- Henderson, Arthur, Jr.: Recent Investigations of the Aerodynamic Characteris-
tics of General and Specific Lifting and Nonlifting Configurations at Mach2L
in Helium, Including Air-Helium Simulation Studies. Presented at tile Spec-
ialists' Meeting on the High Temperature Aspects of II_ersonic Flow (Rhode-
Saint-Genese, Belgium) AGARD,Apr. 1962.
4. Perry, R. W., and MacDermott, W. N.:
velocity, Blowdown-TunnelHotshot.
Arnold Eng. Dev. Center, June 1955.
Developmentof the Spark-Heated, IIyper-
AEDC-TR-5$-6,ASTIADoc. No. AD-157158,
5- McLellan, Charles H., Williams, ThomasW., and Bertram, Mitchel H.: Investi-
gation of a Two-Step Nozzle in the Langley ll-lnch Hypersonic Tunnel. NACA
TN 2171, 1950.
6. Bertram, Mitchel H.: Boundary-Layer Displacement Effects in Air at MachN_-
bets of 6.$ and 9.6. NASATR R-22, 1959. (Super_edesNACATN 41_3.)
7. Grabau, Martin_ Humphrey,Richard L., and Little, WandaJ.: Determination of
Test-Section, After-Shock_ and Stagnation Conditions in Hotshot Tunnels Using
Real Nitrogen at Temperatures FromjO00 to 4000° K. AEDC-TN-61-$2(Contract
No. AF 40(600)-800 S/A 24(61-7j)), Arnold Eng. Dev. Center, July 1961.
It= mse ]
_, Pt_l_
deg Ib/sq in.
-2.5
0
2.5
2.5
5.0 i0,800
7.5 13, i00
i0.0 ii,400
12.5 i0,700
12.5 I0,600
Pt, l,
amagat
ii, 300 61
i0, 700 61
ii, 400 63
ii, 200 62
61
61
61
61
61
Tt_ i, PI'
OK ib/sq in.
3,200 0.17 x 10 -2
3,000 .16
3,100 .17
3,100 .17
3,000 .16
3,700 .21
3,200 .17
3,000 .16
3,000 .16
PI'
amagat
Vl_
ft/sec
ql,
ib/sq in. MI
R_
per ft
0.66 X 10-3
.66
.68
.67
.66
.66
.65
.66
.66
9,100
8,800
9,000
9,000
8,900
9,900
9_i00
8,800
8,800
0.46
.44
._6
.46
•44
.54
.46
.43
.43
20 0.22 x 106
20 .24
20 .2_
20 .23
20 .24
19 .19
20 .22
2o .24
20 .24
TABLE II.- SOURCE AND CONDITIONS OF COMPILED DATA
6.8
9.6
17
!17.3
2O
24
R, Model base Test Source
per ft diameter, in. medium
2.04 x 106
1.20
i00.00
1.00
.23
3.42
2.5O9
2.5O9
•401
1.606
2.867
2.5O9
Air
Air
Air
Nitrogen
Nitrogen
Helium
Langley ll-inch hypersonic
tunnel (unpublished)
Langley ll-inch hypersonic
tunnel (unpublished)
Ames supersonic free-flight
wind tunnel (ref. i)
Chance Vought hypervelocity
wind tunnel (ref. 2)
Langley 24-inch hypersonic
arc tunnel (present)
Langley 22-inch helium tunnel
(ref. 3)
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Figure 4.- Photograph of the Langley 24-inch hypersonic arc tunnel (excluding the vacuum tank). 
L--_____ __ __ ~ _______________ ~ __________ ~~ ______ ~ __ --__ ___ 
'/ 
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[ 
t 
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L 
o 1 
INCH 
(a) Balance components. L-6o-707 
(b) Balance assembly. L-6o-708 
Figure 5.- Photograph of the two-component, strain-gage balance used f or 
present test. 
13 
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Figure 6.- Potential capabilities envelope of the Langley 24-inch hyper-
sonic arc tunnel for nitrogen.
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(a) a.:= 0°. 
(b) ° a. := 5 . L-62-2140 
Figure 8.- Typical schlieren photographs of model. 
.o4
C
m
o ©'
0 4 8 12 16
_, deg
.5
.2
cN .i ///(
o
0 _
-.i
-4 o 4 8 12 16
6, deg
Figure 9.- Variation of pitching-moment coefficient and normal-force coef-
ficient with angle of attack for a blunt-nosed cone in the Langley
24-inch hypersonic arc tunnel. MI = 20. Flagged symbols represent
check points.
i7
Cm
.04
i8 22 26 3o
Run time, milliseconds
I I
_, deg
0 2._
7._
<> 12.5
54 38
.3
CN .1
18 22 26 30 34
Run time, milliseconds
38
Figure i0.- Variation of normal-force and pitching-moment coefficients
during runs in the Langley 24-inch hypersonic arc tunnel. M I = 20.
i8
C
m
.O4
-. 04
.I 0
c_, deg
12 16
Test
M 1 medium Source
O 6.8 Air Langley ll-inch hypersonic tunnel (unpublished)
[] 9.6 Air Langley ll-inch hypersonic tunnel (unpublished)
_] 17 Air Ames supersonic free--flight wind tunnel (ref. i)
<> 17.3 Nitrogen Chance Vought hyperveLocity wind tunnel (ref. 2)
• 20 Nitrogen Langley 24-inch hypersonic arc tunnel (present)
24 Helium Langley 22-inch helium tunnel (ref. 3)
.3
C
N
.2
-.1
-4 0 4 8 12 16
% deg
Figure ii.- Comparison of the longitudinal stability characteristics
obtained on a blunt-nosed cone in several research facilities.
19
Cm
.O4
O
__¢
ia
J
Test
medium
6.8 Air
9.6 Air
17 Air
17.3 Nitrogen
20 Nitrogen
2h Helium
.]
i0 14 18 22 2o
0
[]
<>
Z_
% deg
O
4
8
L?
Source
Langley ll-inch hypersonic tunnel (unpublished)
Langley ll-inch hypersonic tunnel (unpublished)
Ames supersonic free-flight wind tunnel (ref. l)
Chance Vought hypervelocity wind tunnel (ref. 2)
Langley 2h-inch hypersonic arc tunnel (present)
Langley 22-inch helium tunnel (ref. 3)
.2
CN .I
-.1
6 lO 14 18 22 26
Figure 12.- Variation of pitching-moment and normal-force coefficients
with Mach number.
2O
.2
o
0
-.2
A
o
O
O
O <>
L_
i0 14
M I
18 22 26
M I
6.8
9.6
17
_ 6
_] _< •
, o i
_ 0
a) .4
o 6
Te st
medium
Air
Air
Air
_ deg
O 0
[] 4
<> 8
Source
Langley ll-inch hypersonic tunnel (unpublished)
Langley ll-inch hypersonic tunnel (unpublished)
Ames supersonic free-flight wind tunnel (ref. i)
17.3 Nitrogen Chance Vought hypervelocity wind tunnel (ref. 2)
20 Nitrogen Langley 24-inch hypersonic arc tunnel (present)
24 Helium Langley 22-inch helium tunnel (ref. 5)
i0 14 18 22 26
M I
Figure 13.- Variation with Mach number of the longitudinal stability deriv-
atives and the center-of-pressure location on a blunt-nosed cone.
N_A-Langley, 1962 L-3049 21


STATIC STABILITY TESTS IN THE LANGLEY 24-INCH HYPERSONIC ARC TUNNEL ON A BLUNTED CONE AT A MACH NUMBER OF 20

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