This invention relates to reusable, low density, high temperature cryogenic foam insulation systems and the process for their manufacture. A pacing technology for liquid hydrogen fueled, high speed aircraft is the development of a fully reusable, flight weight cryogenic insulation system for propellant tank structures. In the invention cryogenic foam insulation is adhesively bonded to the outer wall of the fuel tank structure. The cryogenic insulation consists of square sheets fabricated from an array of abutting square blocks. Each block consists of a sheet of glass cloth adhesively bonded between two layers of polymethacrylimide foam. Each block is wrapped in a vapor impermeable membrane, such as Kapton(R) aluminum Kapton(R), to provide a vapor barrier. Very beneficial results can be obtained by employing the present invention in conjunction with fibrous insulation and an outer aeroshell, a hot fuselage structure with an internal thermal protection system

Davis, Randall C.

Jackson, L. Robert

Mcauliffe, Patrick S.

Taylor, Allan H.

English

NASA Technical Reports Server

United States Patent 1191 [ i i ]  Patent Number: 4,774,118 
Davis et al. [45] Date of Patent: Sep. 27, 1988 
[54] CRYOGENIC INSULATION S Y m  
[75] Inventors: Rnadnll C. Davis, Poquoson; Allan H. 
Taylor, L Robert Jackson, both of 
Newport News, all of Va.; Patrick S. 
McAuliffc, Burbank, Calif. 
[73] Assignee: The United States of Ameria as 
represented by the A- or of 
the N a t i d  Aeronautics and Space 
Admiiaistritioa, Washington, D.C. 
[21] Appl. No.: 60,182 
[22] Filed: J m  10.1987 
[Sl] 
[52] 
Int. (3.4 .......................... B32B l/W, B32B 3/26 
B32B 7/12 
US.  CI. ...................................... 428/7l; 156/297; 
428/246; 428/25 1; 428/3 16.6; 42W473.5 
[58] Field of Search .................. 220/901, 902; 428/71, 
428/76, 316.6, 473.5, 44, 47, 48. 57. 58, 246, 
251; 156/71, 297, 299,300 
1561299; 4 2 8 1 ~  428147; 428158; 428176 
1561 References Cited 
U.S. PATENT DOCUMENTS 
2,826.240 3/1958 Meier et al. ........................... 428/71 
3,425,889 2/1%9 Willits. Jr. ........................ 24W221.2 
3,619.344 11/1971 Wolinski .......................... 42W317.7 
3,769,118 10/1973 Tariel et al. ........... 42W316.6 
3,906,137 9/1975 BIUX ............................... 42W316.6 
4 , 0 4 4 . 1 ~  8 m n  ~shida e al. .................... 4 2 ~ 3 1 6 . 6  
1.1 17.947 10/1978 Androulaki 
4.124.732 11/1978 Leger ....... 
4.151.800 5/1979 Dotrs et al. 
4,316.934 2/1982 Maier et al. ...................... 428/319.3 
4,361.613 11/1982 Bogner et al. ................... 428/!16.6 
4,463,043 7/1984 Reeves et SI. ......................... 428/68 
4,188.619 12/1984 ONeill ............................. 428/316.6 
FOREIGN PATENT DOCUMENTS 
2000725 1/1979 United Kingdom . 
Primary Examiner-William J. Van Balen 
Attorney, Agent. or Firm-George F. Helfrich: John  R. 
Manning; Charles E. B. Glenn 
~ 7 1  ABSXRArn 
Cryogenic foam insulation 20 is adhesively bonded to 
the outer wall of the fuel tank structure 10. The cryo- 
genic insulation 20 includes square sheets 12 fabricated 
from an array of abutting blocks 14. Each block 14 
includes a sheet of glass cloth IS adhesively bonded 
between two layers of polymethacrylimide foam 16. 
Each block is wrapped in a vapor impermeable mem- 
brane 24, such as a polyimide-aluminum-polyimide 
composite laminate, to provide a vapor barrier. Very 
beneficial results are obtained by employing the present 
invention in conjunction with fibrous insulation 28 and 
an outer aeroshell 30, which is a hot fuselage structure 
having an internal thermal protection system. 
6 Claims, 4 Drawing Sheets 
16 
https://ntrs.nasa.gov/search.jsp?R=19890003370 2020-03-23T23:23:22+00:00Z
US. Patent sep. 27,1988 Sheet 1 of 4 4,774,118 
US. Patent sep. 27, iw 
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Sheet 2 of 4 4,774,118 
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FIGURE 2 
U.S. Patent Sep. 27,1988 Sheet 3 of 4 4,774,118 
US. Patent sep. 27,1988 Sheet 4 of 4 
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4,774,118 
4.774,118 
1 
CRYOGENIC INSULATION SYSTEM 
ORIGIN OF T H E  INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA Contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, as amended, Public 
Law 85-568 (72 Stat. 435; 42 USC 2457). 
BACKGROUND OF T H E  INVENTION 
This invention relates to thermal insulation and, more 
particularly, to reusable, low density, high temperature 
cryogenic foam insulation systems and processes for 
L 1 l ~ ~ ~  rmnufacrure. 
A pacing technology for liquid hydrogen fueled, 
high-speed aircraft is the development of a fully-reusa- 
ble, flight-weight, cryogenic insulation system for pro- 
pellant tank structures. Previously developed cryogenic 
tank insulation systems have employed low density 
polymeric foam materials with good success, however, 
they are not reusable. The current state of the art in 
insulation systems for flight-weight cryogenic contain- 
ment vessels is a spray-on foam insulation (SOFI) sys- 
tem. This material is a rigid closed cell polyurethane 
foam which has excellent insulation qualities at low 
temperatures. This material is quite fragile and is often 
reinforced and/or coated to improve its durability with 
subsequent increases in density and conductivity. Also 
the material begins to decompose at 255' F. and there- 
fore is limited to a 175' F. maximum use temperature. 
Materials of this type cannot withstand the tempera- 
tures generated by aerodynamic heating encountered 
during high speed.flight and therefore require a separate 
thermal protection system to maintain the cryogenic 
insulation below its maximum use temperature. 
The transition from current-art expendable launch 
vehicles to advanced liquid hydrogen fueled aircraft 
will require more efficient cryogenic insulation systems 
that are stronger and more thermally resistant to the 
hypersonic flight environment. Additionally, the cryo- 
genic insulation systems must provide adequate thermal 
insulation to minimize fuel boil-off, prevent the lique- 
faction of air on the outer tank wall, and most impor- 
tantly must be fully reusable. 
Accordingly, it is an object of this invention to pro- 
vide a reusable, light-weight cryogenic foam insulation 
system that can withstand cryogenic environment5 of 
-425' F. while remaining thermally resistant to hyper- 
sonic flight environments of 400' F. 
A further object of this invention is to provide a 
cryogenic foam insulation system that prevents perme- 
ation of gases and liquefaction of air on the outer tank 
wall and minimizes fuel boil-off. 
A further object of this invention is to provide a 
cryogenic foam insulation system for the inner wall of a 
cryogenic fuel tank structure that is impermeable to 
both air and the cryogenic fuel. 
Other objects and advantages of this invention will 
become apparent hereinafter in the specification and 
drawings which follow. 
SUMMARY OF T H E  INVENTION 
According to the present invention, the foregoing 
and additional objects are attained by adhesively bond- 
ing the cryogenic foam insulation to the outer wall of 
the fuel tank structure. The cryogenic insulation con- 
sists of square sheets fabricated from an array of abut- 
.La:- 
ting square blocks. Each block consists of a sheet of 
glass cloth adhesively bonded between two layers of 
polymethacrylimide foam. Each Kapton @-Aluminum- 
Kapton @ (Kapton is a brand of polyimide tape com- 
5 mercially available from E.I. Du Pont de Nemours. Inc. 
Wilmington, Delaware), to provide a vapor barrier. 
Very beneficial results are obtained by employing the 
present invention in conjunction with fibrous insulation 
and an outer aeroshell, viz., a hot fuselage structure 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is an exploded perspective view showing 
sheets of crycgciiic fciiiii inbuiarion adhesively bonded 
to the outer wall of a cryogenic fuel tank structure. and 
an enlargement of a sheet of foam insulation showing 
the individual blocks of the present invention: 
FIG. 2 is an exposed view of a representative foam 
insulation block according to the present invention; and 
FIG. 3 is a cross-section of a preferred embodiment of 
the present invention used in conjunction with fibrous 
insulation and an outer aeroshell. 
FIG. 4 is a cross-section of another preferred embodi- 
ment of the present invention showing the cryogenic 
25 foam insulation attached to the inner wall of a fuel tank. 
DETAILED DESCRIPTION OF T H E  
INVENTION 
As illustrated in FIG. 1, the present invention com- 
prehends adhesively bonding cryogenic foam insulation 
system 20 to the outer wall of a cryogenic fuel tank 
structure 10. The cryogenic foam insulation system 20 
consists of square sheets 12 fabricated from an array of 
35 abutting square blocks 14 which are essentially identical 
to each other. 
Referring now to FIG. 2, the structure of the abutting 
square blocks 14 of the present invention includes dis- 
crete layers of polymethacrylimide foam which have 
40 been heat treated to preshrink the foam and remove 
volatiles which are detrimental to further processing.. 
The layers of heat treated foam 16 are bonded together 
using a sheet of film adhesive 22 on each side of a sheet 
of glass cloth 18. The sheet of glass cloth 18 provides a 
45 vapor barrier and structurally reinforces the foam insu- 
lation system 20 to inhibit cracking. In the preferred 
embodiment, the outer corners of each square block 14 
are machined to provide recesses to accept metal corner 
reinforcements 26, which strengthen the edges to pre- 
50 vent crushing, seal the corners to prevent permeation 
by gases, and provide an impervious bonding surface 
for the vapor impermeable covering layer 24 to prevent 
ingress of gases which would increase the conductivity 
of the insulation system 20. Very beneficial results have 
55 been obtained using a covering layer 24 of Kapton 8- 
Aluminum-Kapton @ composite laminate. 
A preferred embodiment of the present invention is 
shown in detail in FIG. 3. In this embodiment, the foam 
insulation system 20 is used in conjunction with a layer 
60 of fibrous insulation 28 and an exterior thermal protec- 
tion system 30. The higher service temperature of this 
cryogenic foam insulation system 20, which can with- 
stand hypersonic flight environments to 400" F.. re- 
quires less thickness and weight for this rhermal projec- 
A further preferred embodiment of the present inven- 
tion is shown in FIG. 4. In this embodiment, the foam 
insulation system 20 is attached to the inner wall of a 
10 with an internal thermal protection system. 
2o 
3o 
65 tion system 30 than for prior art systems. 
4,774,118 
3 4 
fuel tank structure 10. An outer wall construction sys- 
tern 32 is used in conjunction therewith to provide therm 
mal protection. 
It should become obvious to those skilled in the 
3. A reusable, high-temperature cryogenic foam insu- 
lation system according to claim 1 wherein said low 
density foam is polymethacrylimide foam. 
4. A reusable, high-temperature cryogenic foam insu- 
em- 5 lation system according to claim 1 wherein said vapor 
impermeable covering layer is a polyimide-aluminum- 
p ~ ~ $ ~ $ ~ ? ~ - ~ ~ ~ ~ ~ ; u r e  cryogenic foam insu- 
lation system according to claim 1 wherein said rein- 
this invention is not limited 
bodiments shown and described. 
Letters Patent of the United States is: 
the 
What is claimed as new and desired to be secured by 
1. A reusable, high-temperature cryogenic foam insu- ,o forcing layer is a glass cloth. 
lation system for a 'Yogenic tank  structure^ said 
genic foam insulation system of 
6. A process for producing a high-temperature cryo- 
genic foam insulation sytem capable of reusably with- 
temperatures to 400' F., comprising: standing temperatures to 400' F. comprising: 
a plurality of abutting foam insulation b l o c k  
each of said foam insulation blocks comprising: 
(1) constructing a plurality of abutting foam insula- 
tion blocks, each of said foam insulation blocks 
being formed by 
(a) providing a first and second layer of low density 
(b) providing a reinforcing layer of glass cloth 
(c) adhesively bonding said reinforcing layer to 
said first and second layers of low density 
polymetharcylimide foam; 
(d) adhesively bonding the major exterior face of 
said first layer of low density polymethacryii- 
mide foam to a cryogenic tank structure: 
(e) providing a vapor impermeable covering layer: 
and 2. A reusable. high-temperature cryogenic foam insu- 
(f) adhesively bonding said vapor impermeable lation system according to claim 1 further comprising: 
covering layer to the remaining exterior faces of metal corner reinforcements for sealing the corners of u) 
said foam insulation blocks to prevent permeation the adhesively bonded low density polymetha- 
of gases and for strcgthening the corners of the crylimide foam layers; and 
foam i~~~u la t ion  blocks to Prevent crushing Of said (2) bonding said abutting foam insulation blocks to a 
corners; cryogenic tank structure, said foam insulation 
said metal corner reinforcements being adhesively 35 blocks completely covering the surface of said 
bonded to each comer of said foam insulation cryogenic tank structure. 
blocks. 
I5 
(a) a first and second layer of low density foam 
(b) a reinforcing layer disposed therebetween; 
(c) an adhesive layer bonding said reinforcing iayer 
to said first and second layers of low density 
foam insulation; 20 disposed therebetween; 
(d) said first layer of low density foam having the 
major exterior face thereof bonded adhesively to 
the cryogenic tank structure; and 
a vapor impermeable covering layer adhesively 
bonded to the remaining exterior faces of said foam l5 
insulation blocks. 
polymethacrylimide foam; 
*. 
. * . . +  
- 
45 
M 
5s 
65 


Cryogenic Insulation System

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