The Fire 1 test was designed to study the heating of an Apollo-type reentry vehicle. The total reentry complex weighed approximately 230 kg and entered the upper atmosphere at a velocity of 11.5 km/s. The spectrum of the reentry complex has been studied in the wavelength range 3700 to 8800 A, where 102 multiplets of 21 atoms and the band systems of 5 diatomic molecules have been identified. Comparisons with meteor spectra are made

Millman, P. M.

English

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I,RECEDII_G pAGE BLAI_K NOT FILI4]_D
14. Spectroscopy of Project Fire I, April 14, 1964
PETER M. _'_ILLMAN
National Research Council of Canada
Ottawa, Ontario
The Fire I test, April 14, 1964, u,as designed to study the heating of an Apollo-type
reentry vehicle. The total reentry complex weighed approximately 230 kg and entered
the upper atmosphere at a velocity of 11.5 km/s. The spectrum of the reentry complex
has been studied in the wavelength range 8700 to 8800 ._, where,,i 102 multiplets of 21
atoms and the band systems of 5 diatomic molecules have been identified. Comparisons
with meteor spectra are made.
HE WRITER OF THIS PAPER served as a part-time consultant at the Avco Everett Research
Laboratory during the period 1962 to 1967
(Millman, 1968). The work at Avco involved the
study of the spectra of various reentry objects
resulting from the tests made in the space-
research program of the United States. One of the
tests that has recently been declassified is Project
Fire I, thc high-speed reentry of a scaled-down
model of the Apollo Command Module. This was
launched from Kennedy Space Center, Florida,
at 21 h 42 = 25" UT, April 14, 1964. The reentry
was sighted at 22 h 10m 02.5" UT over a point at
let. 08.8 ° S, long. 14.9 ° W, height 92 km, just
southwest of Ascension Island. Photographic
coverage by Avco was carried out from three
aircraft flying to the northeast of the reentry
track at heights between 2.5 and 4.3 kin. This
experiment produced what were, in effect, a
number of very brilliant artificial fireballs, and it.
is of interest to stud), the spectrum of the lumi-
nosity in relation to comparable studies of bright
meteors.
OBSERVATIONAL DATA
The complete reentry event of Project Fire I
involved the reentries of the main rocket body,
the Apollo model (termed the reentry package,
161
R/P), an Antares II-A5 rocket motor _4th
housing (termed the velocity package, V/P),
and several other unidentified pieces of hardware.
The R/P was in the form of a blunt-faced vehicle
64.5 cm in diameter with a conical after-body
53.6 cm long, and weighed 86.6 kg. The V/P was
cylindrical in form, approximately 356 cm long
and 76 em in diameter, with a spent weight of
143.8 kg. Most of the data given here concerning
the R/P, the V/P, and their reentry trajectory
are taken from Popper et el. (1965). For more
detailed information concerning the mechanical
construction, including the chemical elements
involved, see McI<ee (1966). Over most of the
trajectory covered by the spectrographs, that is,
above 50 km, the R/P and V/P were too close
together to bc separated on the record and the
spectrum photographed is a composite of the
two bodies. For convenience these will be referred
to as the Fire Reentry Complex, FR/C.
The R/P was designed to study the heating
of a blunt, high-speed reentry vehicle and the
radiation emitted by it. It was equipped with
six heat shields on its forward surface and these
were ejected at various heights, measured by
both telemetry and photography. Details con-
cerning the heat shields arc listed in table 1.
The weight of the R/P was 40 percent heat. shields,
40 percent electronics and 20 percent structure.
https://ntrs.nasa.gov/search.jsp?R=19740011337 2020-03-17T14:32:40+00:00Z
16_ EVOLUTIONARY AND PHYSICAL PROPERTIES OF METEOROIDS
TABLE 1 .--Heat Shields on Fire I Reentry Package
No., Approximate
counting Material Thickness ejection
from the (¢m) height
outside (km)
1 Beryllium calorimeter 0.25 70--66
2 Phenolic heat shield 0.50 58---56
3 Beryllium calorimeter 0.50 50--46
4 Phenolic heat shield 0.50 43--40
5 Beryllium calorimeter 0.25 36--32
6 Phenolic heat shield 1.90
TABLE 2.--Observed Velocity of Fire I Reentry Complex
Height (kin) Velocity (kin/s)
90 11.5
75 11.5
65 11.3
55 10.6
50 9.9
45 8.8
40 7.0
The observed velocity of the FR/C is given
in table 2. The trajectory was inclined at 13.3 °
to the horizontal and the visible portion extended
for over 220 km in length from a height of 92 km
down to 41 km above sea level. SeverM isolated
bursts were observed still lower. The projection
of the trajectory on the ocean surface had an
angle of 122 ° from true north through east, taken
in the direction of motion.
Photometry of the visible radiation in the
range 4000 to 6500 ._ gave results consistent
among three independent recordings taken from
two aircraft. For comparison with meteor ob-
servations these data, e.,ipressed in watts per
steradian (Popper et al., 1965), have been re-
duced to absolute panchromatic magnitude,
Mp_n, by nmltiplying by 47r and assuming a total
radiation of 0.126 W as equivalent to Mp,==0.
A summary of the photometry is listed in table 3.
The first part of the table refers to the complete
FR/C. Tile four brightest bursts, well off scale
for the photometric record, were duc to the
breakup of the V/P. From 56 km down, the
magnitudes refer to the R/P only. Comparison
with table 1 will show maxima in luminosity at
the heights where the heat shields were rejected.
Spectrograms of the FR/C for Project Fire I
were obtained with four K-24 cameras, mounted
on a DC-6 aircraft flying at 3.65 km altitude.
The lenses were of 17.8 cm focal length, aperture
ratio .f/2.5, and were fitted with objective trans-
mission gratings, 300 lines/mm, giving a dis-
persion of 187 A/ram in the first order at the
center of the field. Three spectrographs were run
with Eastman Royal-X Pan film, the fourth
with Eastman Aero IR film, and a K2 filter.
Exposures of 2 s each were made continuously
and the data acquisition period was 28 s for one
of the spectrographs loaded _4th panchromatic
film and about 20 s for the other three spectro-
graphs. The distance from the aircraft to the
FR/C varied between 175 and 120 km during
the period of data acquisition.
SPECTROGRAPHIC IDENTIFICATIONS
The general identification of the atomic and
molecular features appearing in the Fire I spectra
were made by a group, which included the writer,
at the Avco Everett Laboratory under the direc-
tion of Charles C. Petty and Richard M. Car-
bone. Many of these identifications have been
illustrated in Popper et al. (1965). However, the
present writer is responsible for the selection of
the data and the height analysis given here. In
general, measurement of the spectra was carried
out using enlarged photographic prints (about
16)<) and the original films were only used for
identification of fine detail, or for examination
of the very faint features.
The typical appearance of Fire I spectra is
illustrated in figures 1 and 2, where many of the
more prominent molecular bands and atomic-line
multiplets are marked for identification. In the
case of the atomic lines the mu]tiplet numbers
used are from Moore (1945), while for the mole-
cules the vibrational band sequences only have
been indicated, with Pearse and Gaydon (1963)
as the primary reference. Heights in kilometers
are placed at the left of the corresponding levels
in the spectra, which are oriented in the figures
with motion downward. The last spectra sho_m,
under 50 km height, are primarily of the R/P
only while the remainder are for the FR/C.
SPECTROSCOPY OF PROJECT FIRE I 163
TABLE 3.--Photometry of Fire I Reentry Complex, April 14, 1964
UT 22 h 10 '_ "4-
02.5
02.8
03.3
03.8
04.1
04.5
05.0
05.8
06.1
06.5
07. I
07.9
08.2
08.7
09.1
09.9
10.5
11.2
11.8
13.0
13.5
15.2
15.8
16.2
16.5
16.8
17.4
18.9
19.4
20.0
20.5
20.5
20.8
22.0
22.2
22.5
23. I
Height (km)
91.6
91.2
89.9
88.6
87.6
86.6
84,9
83,2
82.1
81.2
79.5
77.5
76.7
75.3
74.2
72.4
70.5
68.7
67.3
64
63
59
57
56.4
55.5
54.9
53.5\
5o.0j
48.8
47.5;
46.5j
46,2
45.5;
42.5j
42.1
41.4
40.1
35.6
32.6
-13.1
-14.2
-13.1
- 14.6
-13.6
-14.8
-13.2
-14.4
--14.0
-14.5
--13.6
-- 14.6
--14.2
-15.1
-14.6
-16.7
-18.8
-16.4
-20.5
< --21
<--2I
< --21
<-21
-17.7
-18.3
--19.4
--13.5 to --17.0
-17.9
-16.5 to --17.5
--19.9
--14.5 to -15.5
--19.1
--15.8
--13.2
--17,1
-19. I
Remarks
Photometric threshold
LuminosiW Max.
Min.
Max,
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max,
Min.
Shelf in light curve
Max.
Min.
Luminosity increasing rapidly and record
goes off scale
1]rilliant burst
Very brilliant burst
Very brilliant burst
Most brilliant burst
Record begins again
Rapid oscillations
Max.
Rapid oscillalions
Max.
Rapid oscillations
Max.
Rapid oscillations
Max.
Luminosity decreasing and oscillating
Final spectrographic record
Max,
_fax.
Vibration of the cameras in the aircraft is end- HEIGHTS OF SPECTROGRAPHIC
dent in many of the spectra as wavy lines. These FEATURES
are more marked for some cameras and for the
features where the luminosity is of short duration. . Heights for the various spectrographic expo-
Evidence for a wake of Na and AIO luminosity, sures are available from the trajectory analysis,
and possibly CaC1, is seen at the b_%inning of carried out by Avco using direct photographs.
the overexposed frame at 64_:_ km in figure 2. The first feature visible on the spectrograms is
164
EVOLUTIONARY AND PHYSICAL PROPERTIES OF METEOROIDS
Ht(km)
73
71
4000 5000
cN t c2 A_O C2 A_OCz CZ N
6000 BOO0
I
71
TEST
# 36
, %RV HlIkm)
69
AI 0 0 N N Cu No O12 II 2524 2 1 16 1(3
69
9000
o NaN o N
o _ N
4 2 4 I
4000 5000 6000 7000 8000
WAVELENGTH (ANGSTROMS)
FIGURE 1.--Examples of spectra of the Fire I Reentry Complex from the upper part of the tra-
jectory. Multiplct numbers are from Moore, 1945. The spectrum at 66 km is reproduced
from the second order as the first, order was overexposed.
the cyanogen band system in the violet, which
appears at a height of 88.5 km. This is quickly
followed by the first positive band system of
nitrogen in the red at 87.5 km and the violet
lines of neutral aluminum at 84.5 km. A listing
of the heights of first appearance for all features
identified is given in table 4. This table includes
102 multiplets of 18 neutral atoms and 3 singly
ionized atoms, and the band systems of 5 dia-
tomic molecules. These atoms and molecules are:
H, Li, Be, N, 0, Na, Mg, A1, K, Ca, Ca +,
Ti, Cr, Mn, Fe, Cu, Zn, Sr +, Cd, Ba, Ba +,
BeO, C_, CN, N_, AlO.
This is not claimed to be a complete list but it
does include most of the easily seen features.
The height of disappearance is difficult to de-
termine in many cases owing to the rapidly
varying luminosity and to the overexposure in
the bursts. Most of the atomic lines fade out
between 55 and 50 km, after the breakup of the
V/P. Some multiplets of Mg, Ca, Cr, Cu, Zn,
SPECTROSCOPY OF PROJECT FIRE I
4000 5000
me
• t
WAKE I 2_25 Z 5 4CO 23 2 =2
64_
6000 6000
I
54
49
÷
/
4_
7OOO 8O00
l
165
4000 5000 6000 _ooo = - 7000 sooo
WAVELENGTH (ANGSTROMS}
_IGTJRE 2.--Examples of spectra of the Fire I Reenlry Complex from the lower part of the tra-
jectory, _iultipletr numbers arc from Moore, 1945. The panchromatic spectra at 64 and 54 km
arc reproduced from the second order as the first order was overexposed,
and Cd are visible a little below 50 kin, while
Na and K remain down to the end of the spectro-
graphic record near 40 km height. Bands of CN
and N2 disappear near 70 kin, but C_. is recorded
down to 65 km and Ale to just below 50 kin.
It is possible that, in addition to the molecules
Iisted, bands of CaCI and CaF are present in the
65 to 55 km range. The rejection of the beryllium
heat shields produces a strong Be and Bee
spectrum starting just below 50 kin. Some 20 or
more BeO band sequences have been identified
(Pearse and Gaydon, 1963; Herzberg, 1933;
Lagerquist, 1948) in the blue-green and the red
systems. These remain visible down to the end
of the spectrographic record.
DISCUSSION
The general range of heights observed in the
Fire I spectrum is similar to the range for spectra
of slow fireballs (Millman, 197i) extended to
somawhat greater heights of appearance. The
early appearance of the CN and N2 bands is of
int_rest in relation to the faint band structure
observed with image-orthicon equipment at the
beginning of meteor _rajectories (Millman et al.,
166 EVOLUTIONARY AND PHYSICAL PROPERTIES OF METEOROIDS
TABLE 4.--Heights of the Initial Appearance of Features in
the Fire I Reentry-Complex Spectrum
Height
(km)
88.5
87.5
84.5
79.0
78.0
77.0
74.0
73.5
73.0
72.0
71.5
71.0
68.0
65.0
55.0
48.0
Mtfltiplet numbers (Moore, 1945) and
molecular band sequences*
CN (3883, 4216)b
N_ (first. positive)_
A1 I (1)b
0 I (1)b
0 I (10)b
N I (2)°
0 I (4)e
N I (1)d (16)d, O I (40?)_
N I (24)e (25)e, O I (12)e, Na I (1), (4)b, C2
(4737, 5165, 5636)c
N I (3)e (6). (10),, O I (11), (22)f (23),, Ca I
(2)b, Ca II (1)b, Cr I (1)h (7)b (21)d, Cu I (2)¢,
AIO (4648, 4842, 5079)_
0 I (15)_ (16)t (17)e (18)f, Mg I (2)¢, Cr I (10).
(18)b (22)o, Mn I (2)b, Fe I (1)_ (2)f (3)_,
Cd I (2),
Zn I (2)_
Mg I (1)d, Ca I (3)0 (4)e (5)e (18)¢ (19)¢ (20)° (21)e
(22)_ (23)8 (25)f, Cr I (6)g (8), (31)f (60)_
(145)f (185?)z, Fe I (15)¢ (41)f (42)t (43)f,
Sr II (l)g, Ba I (2),, Ba II (1)d (2)_
H I (1)f, Li I (1)b, N I (8)_, Na I (5)d (6)_
hl I (5), (6), (9)d (10)d (11)d, K I (1)o, Ca I
(1)d (29)d (30)d (31)K (32)°(34)g (41)g (44)a
(47)d (48)_ (49)g, Ca II (2)¢, Ti I (47)g (5)¢
(6), (38)d (42)_ (44), (106)_, Mn I (16)d, Cu I
(6)g, A10 (4470, 5337)8
Mg I (3)a, Fe I (4)_ (16)g (20), (37), (68),
Be I (3)_, BeO (>20 band sequences, 4180-
8712),, AIO (4307),
The subscripts a, b, c, d, e, f, g, in this table form a
qualitative scale which indicates the degree of prominence
of each feature in a descending sequence of values.
1971; Papers 12 and 13, this volume). As in the
case of the faster cometary meteors (Millman,
1971) the atomic lines of 0 and N appear in
Fire I relatively high compared to the rest of the
spectrum. They remain visible to heights below
50 km, which is lower than normally observed in
meteors. In contrast to most meteor spectra,
where the input of atoms from the meteoroid
has a fairly constant composition along the
trail, reentry spectra exhibit a nonhomogeneous
structure resulting from a diversity of atomic
input into the radiating vapor. A good example
is the spot appearances of Cu, Cr and Fe at
different heights between 73 and 71 kin, figure 1.
It has also been found that trace elements in a
reentry vehicle may appear in the spectrum with
unexpected prominence. This warns us agMnst a
superficial estimate of the chemical composition
of an unknown body, based only on the qualita-
tive appearance of its spectrum. The greater
mass and low velocity of reentry vehicles result
in the greater prominence of molecular bands in
their spectra when compared to meteor spectra.
A great variety in the chemical composition of
different components in the reentry objects pro-
duces considerable diversity in the observed band
systems. As noted by Millman (1968), 54 band
systems of 27 different molecules were identified
in a study of 41 reentries that took place in the
period 1960 to 1964.
In any general trcatment of the physics of
solid objects moving at high speed through the
Earth's upper atmosphere the reentry data give
us an important extrapolation of the meteor data
toward more massive objects and lower velocities.
It is hoped that, in the future, a photometric
analysis of these spectrographic records will
become available.
ACKNOWLEDGMENTS
It is a pleasure to acknowledge useful discussions with
Marityn L. Bankoff, Richard M. Carbone and Charles C.
Petty at the Avco Everett Laboratory, Everett, Mass.,
and with the late Luise Hcrzberg at the Defence Research
Board, Ottawa, Ont.
REFERENCES
HERZBERG, L., 1933. ]_ber ein neues bandensystcm des berylliumoxyds und die struktur des
BeO-molektils, Z. Physik, 84, 571-592.
LAGERQUIST, A., 1948. Investigations of the band-spectrum of beryllium oxide, inaugural dis-
sertation for Ph.D., Univ. Stockholm, Almquist and Wiksclls Boktryckeri Ab., Uppsala,
1-98.
MCKEE, C. W., 1966. Project Fire photographic summary and record of reentry phenomena at
hyperbolic velocities, NASA Teeh. Note D-3571, 1-68.
SPECTROSCOPY OF PROJECT FIRE _ 167
MILLMAN, P. M., 1968. A brief survey of upper-air spectra, in Physics and Dynamics of Meteors,
edited by _,. Kre_k at_d P. M. Millman, D. Reidcl Publ. Co., Dordrecht, Holland, 84-90.
--_ 1971. Heights of meteor spectra, J. Roy. Astron. Soc. Can., 65, 37-38.
MILLMAN, P. M., COOK, A. F., AND _IEMENWAY, C: L., I971. Spectroscopy of Pcrscid meteors
with an image orthicon, Can. J. Phys., 49_ 1365-1373.
MOORE, C. E., 1945. A multiplet table of astrophysical interest, Conlrib. Princeton Univ. Obs.,
No. 20.
PEARSE_ 1_. W. B., AND GAYDON, A. G._ 1963. The identification of molecular spectra, Chapman
and Hallj London, 1-347.
POPeEa, L. A., MAnON'EV, P. A., PLAVDON, R. T., BANKOFV, M. L., Am) STAA_, J. V., 1965. Re-
entry data report Project Fire (14 April 1964) ETR #225 Atlas Missile 263D, Avco Everett
Research Lab., Res. Note No. 503_ 1-52.



Spectroscopy of Project Fire 1, April 14, 1964

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