ANALYSIS OF BLAST DOORS ASSOCIATED WITH CHINESE CSS-3 ICBM ROLLOUT SITES

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81T00380R000100510001-6
• Release Decision: RIPPUB
• Original Classification: T
• Document Page Count: 11
• Document Creation Date: December 28, 2016
• Document Release Date: November 4, 2010
• Sequence Number: 1
• Publication Date: February 1, 1981
• Content Type: REPORT

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Ioapry oulysis report
Analysis of Blast Doors Associated
with Chinese CSS-3 ICBM Rollout Sites (S)
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ANALYSIS OF BLAST DOORS ASSOCIATED WITH
CHINESE CSS-3 ICBM ROLLOUT LAUNCH SITES (S)
1. (TSR) This report is a summary of information on the size, shape, composition, and
construction of blast doors at Chinese CSS-3 ICBM rollout launch sites. Blast doors, often desig-
nated as clamshell doors because of their convex shape, protect the missile storage cave or earth-
covered bunker at the new CSS-3 launch sites from enemy attack. Similarly shaped but smaller
doors protect the drive-in entrances to the other caves and bunkers that store missile support
equipment, propellants, and command and communications equipment at each site. Each entrance
has a pair of blast doors that are hinged at the sides and open outward from the middle (Figure 1).
2. (TSR) Imagery of construction activity at Delingha SSM Launch Site 1
in 1978 provided the first identification of the interior framework of a blast door (Figure 2). High
resolution imagery acquired during October 1978 provided data for detailed measurements of this
framework. The door framework is the main structural element of a blast door. It is dark toned
and appears to be entirely composed of steel. Other materials, such as wood, were stacked at the
launch site and appeared to be somewhat lighter in tone than the door framework. The framework
has a checkerboard appearance and measures 0 long by 0 in overall width. There
are six structural members lengthwise and ten cross members. Each structural member has an
approximate thickness of Each of the 43-45 spaces (voids) between these structural
members is 0 wide and long (Figure 3). A hinge plate was identified at the top
and bottom on one side of each framework.
3. (TSR) The sequence of blast door construction at Delingha SSM Launch Site 1 is shown
in Figures 4 through 8. The two steel frameworks for the door were delivered to the launch site by
and stacked one on top of the other. They were each delivered in one piece, already
fully assembled. Between the door frameworks had been moved to the
front of the cave entrance and were turned over, side-by-side (Figure 4). Between
the door frameworks were installed on the adit facing (Figure 5). During the same
three weeks in November 1978, the concrete launch pad was poured and covered to allow the
concrete to harden evenly. Attaching the blast door frameworks and constructing the launch pad
apparently require special work crews from outside the site. Buses and a large number of vehicles
were in the housing support area in November 1978 during this phase of construction.
4. (TSR) No further construction progress was observed until mid-1979, probably because
of severely cold winter weather. December 1978 and January 1980 imagery of the blast door
frameworks indicated that a solid plate is incorporated into the design. When the sun was at a very
low angle and the back of the blast door was open to view, sunlight did not penetrate the
framework. The solid plate, probably also made of steel, appears to form the back surface of the blast
doors, i.e., the concave side facing the missile storage area (Figures 2 and 6).
5. (TSR) In August 1979, a buildup of activity was again observed in the housing support
area, indicating a renewal of blast door construction. On a scaffold was
erected against the front of the two frameworks and filling the voids in the framework with
When the site was next observed on
complete and the scaffold had been removed (Figure 8).
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(Figure 7) and L
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FIGURE 3. DIMENSIONS AND ARTIST'S SKETCH OF BLAST DOOR FRAMEWORK
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SHAPE OF DRIVE-IN CHAMBER
OF THE MISSILE STORAGE BUNKER
BEFORE FACING AND ENTRANCEWAY
IS CONSTRUCTED
NPIC T-0831
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6. (TSR) Imagery of the completed, installed clamshell blast doors indicates that the overall
dimensions of the closed door pair are 6 meters wide and 6 meters high, including the lintel
(Figures 8 and 9). The doors are placed within the concrete retaining wall and adit facing of the
storage bunker. The lintel, also of concrete, closes the space between the flat facing and curved
doors. No door guides were observed; each clamshell door appears to be entirely supported by two
large hinges. Most of the completed bunkers also contain one or two personnel entrances. Each
personnel entrance is small (about 2 by 1 meters) and is protected by a rectangular, flat door of
unknown composition.
7. (TSR) During June and July 1980, the blast doors on the missile storage cave or bunker at
Delingha SSM Launch Sites 2, 3, and 4 (BE Numbers
respectively) were constructed. The activity observed at these sites in 1980 supported the construction
sequence and data concerning door size, shape, and composition observed at Delingha SSM Launch
Site I in 1978 and 1979. Stereoscopic imagery of good interpretability was acquired of the blast door
framework at Delingha Launch Site 2 on Figure 10). Each space in the door where
work was underway had a slanted bin in front of it. The process to fill the blast doors with concrete
appears to be a manual operation with the final, exterior door surface applied with a trowel in a manner
similar to stucco.
8. (TSR) A special study of the completed blast doors was requested by NPIC in order to
determine the composition of the exterior surface. The study technique used the behavior of fall-
off reflectance of sunlight across a surface when the shape of the surface, the sun angle, camera
position angle, and image exposure values are known. Two separate images of the completed blast
doors at Delingha SSM Launch Site I on were used. The
behavior of the reflected light matched values predicted for concrete. The values were very differ-
ent from those which would be expected from a steel-surface, the other principal possibility. Copies of
the study may be obtained, on request, from NPIC.'
IMAGERY ANALYST'S COMMENTS
9. (TSR) The weight of each half of a pair of blast doors is about 24,000 kilograms. The
Many specialized types of concrete have been developed. The blast doors may require both a
quick-drying concrete and a concrete mixed with steel pellets to help attenuate electromagnetic
pulse effects from a nuclear detonation. Concrete mixed with steel pellets can have a specific density
twice that of ordinary concrete.
10. (TSR) Detailed analysis indicates that the clamshell blast doors at CSS-3 rollout launch
sites are constructed of steel framework filled with concrete. A similar construction process is
being used for the silo door at launch sites for the CSS-X-4 ICBM. Most other strategic SSM bases
and complexes in China were constructed in the late 1960s and early 1970s. The caves and tunnels
at these areas also have clamshell blast doors, but very little high-resolution imagery was obtained
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during door construction. When the clamshell doors at these complexes are imaged without cam-
ouflage covers or materials over them, the doors appear lighttoned, indicating an outside surface
of concrete-the same material used on the facing and walls surrounding the cave entrance.
11. (TSR) Clamshell-shaped blast doors have also been observed in China
and at underground storage facilities at several airfields.4 The doors
at thel site appear similar to those at SSM facilities. The blast doors at airfields
are of several types and sizes, not all clamshell shaped, and many appear to be entirely composed of
steel without concrete.
12. (TSR) Onl I at least one set of clamshell-shaped blast doors was subjected to
the effects of a nuclear detonation. The test, designated CHIC 12, was conducted at the Lop Nur
at surface level and had a recorded yield of Clamshell
doors, 11 meters wide by 16 meters high, were positioned 433 meters from ground zero and oriented
directly toward the blast.6 No posttest damage was apparent.'
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(TSR) All applicable KEYHOLE imagery acquired through was used in the preparation
of this report.
2. Merritt, Frederick S., Standard Handbook for Civil Engineers, 2d ed, McGraw Hill, 1976 (UNCLAS-
SIFIED)
3. CIA. IIR, Construction of Gates for Submarine Pens and Other Submarine Related Work at Chinchou
Mining Machinery Plant Including " Mission 09," 16 Jul 73 (SECRET
4. DIA.
SECRET
6. NPIC.I RCA-14/0040/72, Pretest Analysis of Effects Items at GZ-4, Lop Nor Nuclear
Test Site China, Apr 72 (TOP SECRET
(S) Comments and queries regarding this report are welcome. They may be directed to~ ~ Asian
Forces Division,
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