A parachute fabric for aerodynamic decelerator applications is described. The fabric will permit deployment of the decelerator at high altitudes and low density conditions. The fabric consists of lightweight, highly open, circular knitted parachute fabric with ribbon-like yarns to assist in air deflection

Matthews, F. R., Jr.

White, E. C.

English

NASA Technical Reports Server

REPLY TO
ATTN OF. V»Jf
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
HOV 5 1973
TO: KS I/Scientific & Technical Information Division
Attention: Mies Winnie M. Morgan
PROM: GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. patent No. : % \] Ip L( ,
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA patent Case No.
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:yes r^  NO rjn
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words ". . . with respect to
an invention of .
Elizabeth A. Carter
Enclosure
Copy of patent cited above
NASA-HQ
https://ntrs.nasa.gov/search.jsp?R=19740001922 2020-03-17T14:17:41+00:00Z
United States Patent
_ Matthews, Jr. et al.
[in 3,764,097
[45] Oct. 9, 1973
[54] LIGHTWEIGHT, VARIABLE SOLIDITY
KNITTED PARACHUTE FABRIC
[75] Inventors: Frederick R. Matthews, Jr.,
Poquoson; Erskine C. White,
Newport News, both of Va.
[73] Assignee: The United States of America as
represented by the National
Aeronautics and Space
Administration
3,531,067 9/1970 Mitchell 244/142
2,432,920 12/1947 McKay et al 244/142
3,252,676 5/1966 Frieder 244/145
3,386,692 6/1968 Schuerch 244/145
Primary Examiner—Duane A. Reger
Assistant Examiner—Jesus D. Sotelo
Attorney—Howard J. Osborn et al.
[22]
[21]
Filed:
Appl. No.
Dec. 23, 1971
211,332
[57] ABSTRACT
o
o
523
[52] U.S. Cl 244/145
FN51 ] Int. Cl B64d 17/02
58] Field of Search 244/142, 145, 138 R;
66/169-170,202, 198
H OJ|
O '•"I
529,794
References Cited
UNITED STATES PATENTS
9/1970 Stabler et al 244/142
A decelerates particularly adapted for high altitude,
low atmospheric density operation includes a canopy
constructed of a circular knitted fabric including rib-
bon-like yarns which are twisted to provide air deflec-
tion and hence, resultant drag. A radar reflective ver-
sion of the fabric is preferably knitted of a combina-
tion of nylon filaments and metallized polyester tapes
or ribbons which, in addition to serving in deflecting
air, provide the desired reflectivity.
10 Claims, 4 Drawing Figures
Patented Oct. 9, 1973 3,764,097
2 Sheets-Sheet i
FIG. 1
DESIGN I
#
X
#
X
0
0
0
0
0
0
0
0
X
#
X
#
0
0
0
0
0
0
0
0
#
X
#
X
0
0
0
0
0
0
0
0
X
5*
X
#
0
0
0
0
0
0
0
0
#
X
#
X
0
0
0
0
0
0
0
0
X
*fr
X
#•
FIG. 3a
DESIGN 2
0 0 0
0 0 0
0 0 0 0
FIG. 31
INVENTORS
FREDERICK R. MATTHEWS, JR.
ERSKINE C. WHITE
BY
ATTORNEY
• Patented Oct. 9, 1973 3,764,097
2 Sheets-Sheet 2
<N
o
INVENTORS
FREDERICK R. MATTHEWS, JR.
ERSKINE C. WHJTE
BY
ATTORNEY
3,764,097
LIGHTWEIGHT, VARIABLE SOLIDITY KNITTED
PARACHUTE FABRIC
ORIGIN OF THE INVENTION
The invention described herein was made by employ-
ees of the United States Government and may be man-
ufactured and used by or for the Government for gov-
ernmental purposes without the payment of any royal-
ties thereon or therefor.
FIELD OF THE INVENTION
This invention is related to parachutes and like decel-
erators and to an improved support fabric for such de-
celerators.
BACKGROUND OF THE INVENTION
Aerodynamic deceleration devices or decelerators
such as conventional canopy-type parachutes and bal-
loons are generally limited to low altitudes. Such de-
vices are generally fabricated of heavy materials having
high solidity rates, that is, a low resistance to atmo-
sphere, thus preventing their use at high altitudes and
low atmospheric densities. Further, the rate of descent
of such decelerators is not constant thus causing erro-
neous results in measurements in which they are used.
Substantial improvements in the amount of drag pro-
duced at high altitudes in rarified gases, and in the con-
stancy of deceleration provided, have been obtained by
the use of a parachute canopy in the form of an open
mesh array of fibers or the like. Reference is made to
U.S. Pat. No. 3,386,692 (Schuerch) for a further dis-
cussion of parachutes of this type as well as of the prob-
lems associated with providing a device which can gen-
erate a large aerodynamic drag at high altitudes and
low atmospheric density.
Although the use of an open mesh fabric canopy has
provided considerably promise, successful develop-
ment of a workable high-altitude Stbkes-flow decelera-
tor has depended to a large extent on the availability of
appropriate mesh structures. In order to maximize the
benefits of the Stokes-flow principle of drag genera-
tion, the mesh structures should comply with require-
ments of minimum characteristic width of the filaments
making up the mesh, minimum solidity of the mesh
flection. It has been found that circular knitting pro-
vides decided advantages regarding fabric openness,
ease of preparation and processing, and the like, over
techniques such as weaving as well as over other knit-
5 ting techniques. The fabric is preferably radar reflec-
tive in which case the fabric is made from a combina-
tion of metallized polyester ribbons and synthetic plas-
tic polymeric filaments knitted together. The solidity
rate, as well as the radar reflectivity may be varied over
10 a very wide range by varying the relative percentages
of the metallized polyester ribbons and nylon filaments.
The ribbons are preferably aluminized polyester tapes
whereas the nylon filaments are preferably circular di-
ameter nylon monofilaments.
15 Other features and advantages of the invention will
be set forth in, or apparent from, the detailed descrip-
tion of preferred embodiments found hereinbelow.
BRIEF DESCRIPTION OF THE DRAWINGS
20 FIG. 1 is highly schematic perspective view of a de-
celerator incorporating the present invention;
FIG. 2 is a plan view of the knitted canopy fabric of
the deceleration of FIG. 1; and
FIGS. 3A and 3B are knitting pattern diagrams asso-
25 ciated with the knitted fabric of FIG. 2.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
Referring to FIG. 1, a decelerator or deceleration de-
vice, generally denoted 10, is shown. Decelerator 10
comprises an X-brace parachute 12 which supports a
load 14 with a central suspension line 15 and includes
an X-brace 16 and open-mesh parachute canopy 18
mounted thereon. The construction of parachute 12 is
generally conventional apart from the canopy 18 de-
scribed hereinbelow and a decelerator incorporating
the invention can take a number of different forms in-
cluding that of a simple collapsible canopy as well as
those described in the above-mentioned U.S. Pat. No.
3,386,692.
The parachute fabric used in canopy 18 is shown in
more detail in FIG. 2. The fabric is preferably made
from nylon monofilaments denoted 20 and aluminized
polyester tapes, sold under the name of "Lurex
30
35
40
structure and minimum weight per unit area of mesh, 45 TE100", denoted 22. In an exemplary embodiment the
although limitations on these requirements are dictated tapes 22 are approximately 0.00025 inch thick and ap-
by the effects of rarified gas regarding the first require-
ment and by trade-off considerations involving para-
chute size versus solidity for payload-carrying para-
chutes, regarding the latter two. The availability of suit-
ably fine meshes in quantities sufficient for use in such
canopies has been severely limited by fabrication prob-
lems and although a number of techniques, such as glu-
ing, punching, slicing, milling and weaving, have been
considered, none of these has proved to be entirely sat-
isfactory.
SUMMARY OF THE INVENTION
50
55
proximately 0.010 inch wide and include an aluminum
coating 400A. thick on both sides and a chemically re-
sistant coating on top of the aluminum. The tapes are
preferably reinforced by 15-denier nylon filaments
wrapped around the tapes in opposite directions. It will
be understood that the figures given are merely exem-
plary and it is noted that the ribbons can be relatively
wide, with widths up to about 2 inches being contem-
plated. Similarly the filaments can be several mils in di-
ameter.
The knitted fabric shown in FIG. 2 was circular knit-
ted on a 32 feed, 18 cut Singer ROF latch needle ma-
in accordance with the present invention a decelera- . chine with a cylinder diameter of 24 inches. The fol-
tor or parachute fabric is provided which is lighter in ' - - •—•-• - -•• • • - - • • ._.,....„;
weight and has a greater solidity range than the materi-
als of the prior art. The material is easy to package and
when utilized in a deceleration device provides sub-
stantial drag at high altitude and low densities
lowing table, Table I, provies the complete knitting ma-
chine specifications.
TABLE I
According to a presently preferred embodiment, the
fabric of the invention is circular knitted and includes
ribbon-like fibers which are twisted to provide air de-
65 Model — Singer ROFCut— 18
Diameter of cylinder — 24 inches
Total number of needles — 1,380
3,764,097
Total number of feeds — 32
Speed — 20 rpm
Positive feed — IRO tape
Type needles — latch
Shims — 0.040
Take-down tension — minimum
Production rate — 40 to 50 yards/hour
Finished fabric width (open) — 65 inches
A number of different canopy fabrics were knitted
and are tabulated in Table II.
TABLE II
Fabric
Designation
A
B
C
D
E
F
G
H
Fabric
Designa-
tion
Stitch
Design 1
Design
Design
Design
Design
Design
Design
Design 2
Uni-wave
Setting
35-33
35-33
35-33
35-33
35-33
35-33
35-37
35-37
Fiber Content
20/3 Semidull nylon 6 yarn
1/100 - inch supported C-25
metallic yarn
Same
Same
Same
100% 1/125-inch supported
C-25 metallic yarn
20/3 Semidull nylon 6 yarn
U100 - inch supported C-25
metallic yarn
H
Fabric
Designation
A
B
C
D
E
F
O
H
Fabric
Designation
A
B
C
D
E
F
100% 20/1 Semidull nylon 6
yarn
Same
Finished Fabric Weight
(grams/square meter)
5.57
6.42
8.65
8.19
10.19
6.33
4.56
7.35
Positive
Feed
Pulley — 6"
Wheel — 95
Same
Same
Same
Same
Same
Yarn Arrangement
For Knitting
3 feeds nylon - I feed
metallic and repeat
8X
1 feed nylon - 1 feed
metallic and repeat
16X
1 feed nylon 3 feeds
metallic and repeat
8x
3 feeds nylon - 5
feeds metallic and
repeat 4X
All feeds supported
metallic yarn
5 feeds nylon - 3
feeds metallic and
repeat 4X
AH feeds nylon
All feeds nylon
Light
Transmission
89%
88%
80%
84%
78%
88%
Construction
(Wales X Courses)
7.5 X 10
7.5 X 9
7.5 X 9
7.5 X 10.5
8 X 8.5
8 X9.5
The fabric of FIG. 2 is designated "A" in Table II and
Designs 1 and 2 in Table II are indicated in FIGS. 3A
and 3B wherein the symbol X indicates "knit", the
symbol * indicates "tuck" and the symbol O indicates
"welt" in accordance with conventional nomenclature.
As shown in Table II, the finished fabrics range in
weight from 5.6 to 10.2 grams per square meter and
provide fabric openness values between 78 percent and
89 percent. Several different tests may be used to de-
termine fabric "openness", including a light transmis-
sion test and although the results differ depending on
the test, the values given are representative.
As discussed above, in accordance with one feature
of the invention, the parachute canopy 18 is made
5 radar reflective by including reflective yarns 22. To
provide fabrics with varying reflective characteristics,
a range of fabrics were knitted using different percent-
ages of C-25 metallic yarn combined with 20/3 Nylon
6 using different feeds as shown in Table II.
10 To provide minimum weight and stabilization in cut-
ting, the polyester nylon and nylon fabrics for the de-
celerator chutes were finished. Although short samples
may be finished open width on a tenter frame, to stabi-
lize circular knit goods at predetermined widths com-
15 mercially, a stream calendar should be used. It is noted
that with both techniques particular care must be taken
to avoid rough edges from "picking"the delicate fabric
and causing runs. In an exemplary finishing procedure
for circular knit fabrics containing supported C-25
Same 20 Lurex and 20/3 nylon 6 yarn, the fabric was framed and
set on a Famatex unit at 350°F. for 30 seconds. The fin-
ished width was approximately 65 inches, as noted in
Table I. The fabric could not be fed directly onto the
frame and had to be clipped on by hand in short pieces,
25 thus producing a large number of runs in the fabric be-
cause of the excessive handling required. For these rea-
sons, as mentioned above, the use of a tenter frame for
this particular fabric on a continuous basis would be
most difficult. In a second example involving circular
30
 knit, non-reflective fabrics containing 100% 20/1 semi-
dull nylon 6, the fabrics were first processed through a
stream calendar at a tubular width of 34 inches. The
fabrics were then autoclaved in a Turbo Model FS
1200 Autoclave, in order to stabilize the fabrics for
35
 metallizing. The autoclaving involved 1 minute of pre-
vacuum, 5 minutes of steam at 250°F. and 5 minutes of
port-vacuum. The autoclaving causes fabric shrinkage
of about 30 percent.
Circular knitting provides a number of advantages as
compared with other techniques which might be used
in fabricating open mesh parachute canopies. For ex-
ample, weaving of the mesh filaments is not practical
because such an approach will not produce the desired
fabric openness. Further, other knitting techniques,
and, in particular, warp knitting techniques, have
proved unsatisfactory for a number of reasons includ-
ing the non-acceptability of the fabric produced be-
cause of the solidity and metal content as well as' rea-
sons involving processing difficulties.
As discussed above, the parachute canopy fabric of
the invention provides a number of advantages as com-
pared with prior art fabrics used for the same purposes.
For example, the fabric is lighter in weight, has a
greater solidity range and can be more compactly pack-
aged. The use of ribbons of yarn which are woven such
that the flat parts thereof are twisted as shown in FIG.
2, provides added air deflection as compared with cir-
cular diameter monofilaments and prevents the air
,„ from flowing directly through the fabric, thereby pro-
viding the necessary drag and, hence, deceleration.
Although the invention has been described in refer-
ence to exemplary embodiments thereof, those skilled
in the art will understand that variations may be ef-
65 fected in these embodiments without departing from
the scope and spirit of the invention.
What is claimed as new and desired to be secured by
Letters Patent of the United States is:
45
50
55
3,764,097
.* 1,. in a decelerates comprising an open-mesh para-
chute support fabric and means for coupling said sup-
port fabric to a load, the improvement wherein said
support fabric comprises an open-mesh knit fabric of
high porosity including ribbons the flat portions of
which are twisted to oppose air flow through the fabric
and hence produce resultant drag.
2. A decelerator as claimed in claim 1 wherein said
ribbons are fabricated of polyester film.
3. A decelerator as claimed in claim 1 wherein said
support fabric includes radar reflective material.
4. A decelerator as claimed in claim 3 wherein said
radar reflective material comprises metallic ribbons
circular knitted into said fabric.
5. A decelerator as claimed in claim 4 wherein said
metallic ribbons comprise aluminized polyester rib-
bons.
6. A decelerator as claimed in claim 5 wherein said
fabric further comprises circular diameter nylon mono-
10
15
filaments,
7. A lightweight, variable solidity, radar reflective
knitted parachute fabric comprising a circular knitted
fabric knitted from synthetic plastic polymeric fila-
ments and radar reflective ribbons, the flat parts of said
ribbons being twisted to provide air deflection in use.
8. A parachute fabric as claimed in claim 7 wherein
said radar reflective elements comprise polyester rib-
bons having a metallic coating thereon, and said metal-
lic coating is aluminum.
9. A parachute fabric as claimed in claim 7 wherein
said filaments comprise circular diameter nylon mono-
filaments.
10. A parachute fabric as claimed in claim 7 wherein
the weight per unit area of the fabric is less than 15
grams per square meter and the percentage of light
transmission therethrough is greater than SO percent.
20
25
30
35
40
45
50
55
60
65


Lightweight, variable solidity knitted parachute fabric

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