Multilayer insulation of prefabricated panels is developed for cryogenic storage tanks. System utilizes panels of aluminized Mylar separated by sheets of low conductivity polyurethane foam. Panels are self-evacuated by cryopumping of gaseous carbon dioxide at time of use

Dengler, R. P.

Niendorf, L. R.

Nies, G. E.

Perkins, P. J., Jr.

English

NASA Technical Reports Server

December 1970	 Brief 70-10646 
.
	
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Lightweight, Self-Evacuated Insulation Panels 
An extremely efficient system of thermal insulation, 
developed for a rocket's fuel tanks, may be adaptable 
to many uses in industry. Liquid-hydrogen fuel tanks 
require highly efficient insulation to prevent excessive 
boil-off losses during storage. They are readily pro-
tected thermally for several days in space by low-emis-
sivity multiple radiation shields aided by the vacuum 
of space. But thermal protection is also needed while 
a vehicle is in the atmosphere, both on the launching 
pad and during its boost into space.
•	 r- _
Adhesive 
Seal	
qL -i: ; CO2 Gas  
Separator	 1110 
• Radiation	 _I _
Shield
Vacuum 
Casing 
tA Section A-A 
Figure 1.	 Details of Panel
complete loss of vacuum around the entire tank. 
Development of such an insulation system has 
required the solution of such problems as provision of 
(1) a lightweight and flexible material to hold a 
vacuum of roughly 10 4 torr while the vehicle remains 
in the atmosphere; (2) convenient means of evacuation 
shortly before service, since a lightweight vacuum-
retention material, perhaps not completely imperme-
able, may hold the required vacuum only relatively 
briefly; and (3) lightweight, thermally efficient, multi-
Cryogen	 Panels 
Tank	 I Condensed Wall 
Adhesive	
- 
Attachment
Seal Strip 
Section A-A 
Figure 2. Shingle Arrangement of Panels 
For thermal protection in the atmosphere to be. 
comparable to that in space, insulation by multiple 
radiation shields must include an integral vacuum 
system. Since insulation imposes a weight penalty and 
structural problems in its application to the tank, the 
materials used must be lightweight, and the overall 
structure (including the vacuum system) must be ade-
quately fastened to the tank and conveniently evac-
uated before use. Moreover the evacuated insulation 
should be arranged in small sections around the tank 
to improve the system's reliability by preventing a 
small leak from causing catastrophic failure through
layer insulating materials properly conditioned to pre-
vent outgassing in a vacuum. 
A new insulation system employs panels of multi-
layer. aluminized Mylar for thermal-radiation shields, 
with each shield separated from the next by a 0.020-in. 
sheet of low-conductivity polyurethane foam. The 
many layers are enclosed in a vacuum-tight, flexible, 
four layer laminated casing of thickly aluminized 
Mylar film (Fig. 1). Prefabricated insulating panels 
are arranged over a tank like shingles, with adjacent 
rows of panels overlapping (Fig. 2).
(continued overleaf( 
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The panels are self-evacuated by cryopumping at 
the time of use. Gaseous carbon dioxide, under slight 
positive pressure in a panel at ambient temperature, 
is condensed on the panel's inner surface adjacent to 
the cold tank; thus the panel is self-evacuated when 
the tank is cooled during filling with hydrogen. The 
very low vapor pressure of solid CO 2 at cryogenic 
temperature makes the required vacuum readily 
achievable. 
In comparison with earlier insulations, tests have 
shown heat transfer by the new insulation to be less 
by from 90% (on the ground) to 99% (in space). 
Notes: 
1. The following documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-TN-D-4375 (N68-18046), Self-Evac-
uated Multilayer Insulation of Lightweight 
Prefabricated Panels for Cryogenic Storage 
Tanks
2. Technical Questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B70-10646 
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,379,330) and royalty-free license rights 
will be granted for its commercial development. In-
quiries about obtaining a license should be addressed 
to:
Patent Counsel 
Mail Code 500-311 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, OH 44135 
Source: L. Niendorf and G. Nies of

Union Carbide Corp. 
under contract to

Lewis Research Center,

and P. J. Perkins, Jr., and R. P. Dengler

Lewis Research Center

(LEW-90361)
S 
Brief 70-10646	 Category 03


Lightweight, self-evacuated insulation panels

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