Design and construction of satellite appendage tie-down cor

Madey, J. M.

Travis, E. W.

English

NASA Technical Reports Server

REPLY TO 
ATTNOF GP 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON. D.C. 20546 
March 27, 1971 
TO : USI/Scientific & Technical 1nformation.Division 
Attention: Miss Winnie M. Morgan , * 
Counsel for Patent Matters 
FROM s GP/Office of Assistant General 
SUBJECT: Announcement of NASA-Owned 
U.S. Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8 ,  1970, 
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. : 3,350,034, 
Corporate Source : Goddard Space Flight Center 
Supplementary 
Corporate Source . 
NASA Patent Case No.: X6S-02554 
,/ 
Gayle Parker 
copy or racenc 
2 -  
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710011589 2020-03-17T02:55:07+00:00Z
Oct. 31, 1967 J. M. MADEY €TAL 3,350,034 
SATELLITE APPENDAGE TIE-DOWN CORD 
Filed Oct. 23, 1965 2 Sheets-Sheet 1 
F1G.I 
INVEN TOR5 
ELMER W. TRAVIS 
JESSE M. MADEY 
Oct. 31, 1967 J. M. MADEY ETAL 3,350,034 
SATELLITE APPENDAGE TIE-DOWN CORD 
Filed Oct. 23, 1965 2 Sheets-Sheet 2 
FIG.2 
BY 
lNVEhTOR!S 
ELMER W. TRAVIS 
JESSE M. MADEY 
e ates Patent Patented Qct. 31, 1967 
1 
3,350,034 
Jesse M. Madey, Hyattsville, and Elmer W. Travis, Clarks- 
ville, Md., assignors to the United States of America as 
represented by the Administrator of the National Aero- 
nautics and Space Administration 
SATELLITE APPENDAGE TIE-DOWN CORD 
Filed Qct. 23, 1965, Ser. No. 504,266 
8 Claims. (CL 244-1) - 
ABSTRACT OF THE DISCLOSURE 
A tie-down cable for spacecraft appendages having an 
elastic nylon cord within a fiberglass covering of slightly 
longer length to absorb, in the event of cord failure, cir- 
cumferential expansion of the spacecraft rocket booster 
and maintain the appendages in a packaged condition. 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
The present invention relates to a seouring mechanism 
of a tie-down cord type for physically and mechanically 
securing or tying down the various appendages which may 
protrude or extend from a satellite or space-craft, and 
more particularly to  a securing mechanism of this type 
that may be used to fasten space craft booms, solar pad- 
dles, and the like, to the surface or face of the last stage 
of a rocket booster so that tie-down of the appendages is 
established during the launch and the initial flight of the 
satellite and so that release thereof occurs at some time 
after the space-craft has left the atmosphere of the earth. 
The prior art devices that have been commonly used 
for tie-down mechanisms have been nylon parachute 
cords, fiberglass ropes, or nylon cords reinforced at local 
or predetermined hot spots with fiberglass. The disadvan- 
tage of many of these prior art devices is that, in in- 
stances where they do have a desired elasticity, they are 
inherently limited by the fact that they tend to fail when 
they are subjected to extreme temperature conditions, 
such as approximately 200” F. Conversely, where the 
prior art devices may have a desired temperature quality, 
then they are not sufficiently elastic for stretching at such 
time as the last stage rocket booster expands in its cir- 
cumferential dimension as a result of and due to  internal 
pressure and temperature conditions that exist during the 
operation of the rocket booster. 
A further disadvantage with many prior art tie-down 
devices is the absence of “fail-safe” features in that a 
portion thereof attains a temperature in the range of 400- 
500” F. due to any number of possibilities, such as the 
rocket booster case burning through in one spot or local 
excessively hot spots. Also encountered in the prior art 
devices is the difficulty of joining different types of cords 
together such as fiberglass types to nylon types. It has 
been observed that when two different types of cord ma- 
terials are joined together, they are generally unreliable 
as a tie-down mechanism inasmuch as they are subjected 
to failure at the joint thereof in being exposed to high 
temperatures. 
The present invention relates to a tie-down cable com- 
prising a nylon cord housed within a woven, braided Tef- 
lon-treated fiberglass covering which is selected to be 
longer than the nylon cord. This cable is formed approxi- 
mately into a circle or loop under tension about the last 
stage of the rocket booster with the ends thereof being 
joined together under compression by a copper retaining 
sleeve (Nicopress sleeve), so that the cable holds the 
appendages securely in place. Since the braided fiberglass 
2 
sleeving is longer than the nylon cord, only the nylon 
cord is pre-loaded when the cable encircles the rocket 
booster and has its ends securely joined by the copper re- 
taining sleeve. With the cable constructed in this manner, 
6 the rocket booster can expand several inches before the 
fiberglass covering carries any load at all. Explosive ac- 
tivated guillotine means cooperate with the cable to sever 
it at a predetermined time to thereby permit the ap- 
pendages to be extended upon the release of the cable. 
It is therefore an object of the present invention to pro- 
vide an appendage tie-down mechanism that precludes 
premature erection of appendages. 
It is another object of the present invention to provide 
a tie-down mechanism useful in retaining satellite append- 
15 ages, and that can withstand high temperatures and yet 
be capable of possessing a high degree of elasticity. 
It is a further object of the present invention to pro- 
vide a satellite appendage tie-down mechanism that pre- 
cludes premature erection of appendages and that pos- 
20 sesses “fail-safe” features should abnormally high tem- 
perature or pressure conditions exist. 
The above and other objects and advantages of the in- 
vention will become apparent upon full consideration of 
the following detailed description and accompanying draw- 
FIGURE 1 is an isometric view of a rocket booster 
and satellite combination with the satellite appendages re- 
tained to the booster by the tie-down mechanism of the 
present invention; 
FIGURE 2 is a plan view of a preferred embodiment 
of the tie-down mechanism formed into a circle about 
the last stage of the rocket booster of FIGURE 1; 
FIGURE 3 is an enlarged view of the cut-away portion 
taken along line 3-3 of the tie-down mechanism of FIG- 
FIGURE 4 is an enlarged, partial cross-sectional view 
of the joint of the tie-down mechanism of FIGURE 2 
taken along line 4-4 thereof. 
Referring now to the drawings, there is shown in FIG- 
4 0  URE 1 a space vehicle 2 including a satellite 3 having 
booms 4 and solar paddles 5 affuted thereto, and a rocket 
booster 6 formed as an integral part therewith. Tie-down 
mechanisms 10 and 10’ of the type shown in FIGURE 2 
and described in more detail hereinafter, are used to hold 
45 booms 4 and solar paddles 5, respectively, against and 
alongside rocket booster 6 during the launch and powered 
flight of space vehicle 2. 
Tie-down mechanism 10, as shown in FIGURE 2, com- 
prises a cable 11 formed into a circle about the ap- 
50 pendages to  be tied down, such as the booms and/or solar 
paddles (not shown), and in which there is a joint 12 in- 
cluding a retaining sleeve 13 to connect the ends of cable 
11. Two cutting devices 15 are positioned relative to cable 
11 to sever the cable at a predetermined time. 
Cable 11, as illustrated in FIGURE 3, is essentially a 
nylon cord 14 housed within a loose fitting, woven, 
braided, Teflon-treated, fiberglass covering 18. As used in 
FIGURE 1, and more clearly depicted in the cut-away 
portion showing of FIGURE 3, under normal operating 
60 conditions nylon cord 14 is held under tension by the 
compression action of retaining sleeve 13 at joint 12. On 
the other hand, the fiberglass covering 18, which is se- 
lected to be longer than the nylon cord 14 housed there- 
within, is loosely fitted and under no tension. 
Nylon cord 14, under ideal operating conditions of the 
space vehicle, serves to hold the appendages in place. 
However, as already explained above, under abnormal 
conditions, such as excessive temperature variations or 
booster case failures (burn through), the nylo? cord 
70 could very well give a d &  break, thereby releasing the 
appendages prematurely. m e n  such a condition exists, 
the fiberglass covering, which has not been previously 
10 
26 ings in which: 
30 
35 URE2;and 
55 
65 
3,350,034 
3 4 
under tension and which can withstand up to approxi- derstood that while two cutting devices 15 are shown in 
mately 1000” F., takes over to hold the appendages in FIGURE 2, the same result can be achieved with one. 
place. By the cable 11 being constructed in this manner, The second cutting device is included as an added insur- 
a “fail-safe” feature is provided in the form of fiberglass ance feature. 
covering 18. In addition, by fiberglass covering 18 being 5 While the tie-down mechanism 10 has been described 
loosely fitted about nylon cord 14, the nylon cord is able as generally having an inner nylon cord 14 and an outer 
to elongate or stretch as the casing of the booster expands fiberglass covering 18, it should be noted that the cord 
due to heating and/or pressure during normal operating can be of any one of a number of materials which are 
conditions. In other words, fiberglass covering 18 does elastic and can withstand such temperature and pressure 
not restrain the circumferential movement of nylon cord 10 conditions as are associated with rocket boosters in 
14. flight, and the covering can likewise be of a material that 
Fiberglass covering 18 also provides protection for has strength and can withstand rather abnormally high 
nylon cord 14 by acting as a thermal insulator therefor. temperature and pressure conditions as are concerned 
It is worthwhile to note that it is both braided and woven with rocket boosters in flight. 
to provide extra strength and is treated with Teflon to 15 It should be understood that various changes in the de- 
reduce the friction between it and the appendages. Ac- tails, materials, steps and arrangement of parts, which 
cordingly, it can be stated that during normal operation of have been described and illustrated to explain the nature 
tie-down mechanism 10, nylon cord 14 serves to hold the of the invention, may be made by those skilled in the art 
appendages against booster 6 and fiberglass covering 18 within the principle and scope of the invention as ex- 
acts as a thermal insulation therefor and, at such time 20 pressed in the appended claims. 
when abnormal conditions exist and nylon cord 14 fails, What is claimed is: 
fiberglass covering 18 takes the place of the nylon cord 1. A tie-down system for restraining various appendages 
and thereby prevents premature erection of the appen- of a space vehicle against the surface of a rocket booster 
dages. attached thereto, comprising: an elastic cord of sufficient 
FIGURE 4 illustrates an embodiment of the copper 25 length to  fit around the circumference of said booster, 
retaining sleeve 13 used in maintaining nylon cord 14 a woven, braided, Teflon-treated fiberglass covering 
under tension and having two apertures 17, 19 therein, adapted to  overlie said elastic cord and being slightly 
one for each end of cable 11 to pass through and be re- longer in length than said elastic cord when said cord is 
tained upon retaining sleeve 13 being swaged or crimped. in its unloaded condition, and a retaining means for 
In the use of this particular retaining sleeve, for example 30 joining the ends of said elastic cord and the ends of 
a Nicopress, it has been found that the most reliable grip said fiberglass covering into a composite joint such that 
is achieved when both ends of cable 11 are prepared as said outer fiberglass covering is under conditions of no 
follows: load, while said elastic cord is pre-loaded. 
The fiberglass covering 18 is bunched up to expose the 2. The tie-down system of claim 1 wherein said elastic 
extremities of nylon cord 14. Then, an inner silicon rub- 35 cord is nylon. 
ber collar 16 is inserted between nylon cord 14 and fiber- 3. A tie-down system for restraining satellite booms 
glass covering 18, and an outer silicon rubber collar 22 and solar paddles to a rocket booster comprising: a cable 
is placed over fiberglass covering 18. These two collars having an elastic cord of nylon adapted in length to fit 
are chosen to have a length slightly longer than the length around the circumference of said rocket booster, and 
of the apertures within retaining sleeve 13 and diameters 40 a woven, braided, fiberglass covering overlying said elas- 
such that they can easily be formed with cable 11 and tic cord, said fi’berglass covering being treated with Teflon 
still, at the same time, form a snug fit therewith. In addi- to reduce friction between said fiberglass covering and said 
tion, the total diameter of cable 11, with the collars, must booms and solar paddles; an inner shrinkable collar posi- 
be such that cable 11, with the collars, can be inserted tioned between said elastic cord and said fiberglass cover- 
into apertures 17, 19 of retaining sleeve 13. 45 ing at the ends of said cable: an outer shrinkable collar 
Collars 16 and 22 are used to enhance the friction fit positioned about said fiberglass covering in the vicinity 
of the various elements of cable 11 with the apertures of of said inner shrinkable collar and having a length sub- 
retaining sleeve 13 and also to assist in preventing the stantially that of said inner shrinkable (collar; and a re- 
edges of retaining sleeve 13 from rupturing or cutting taining means having a length slightly smaller than said 
fiberglass sleeve 18. 50 collars and having a pair of longitudinal apertures there- 
Once both ends of cable 11 are prepared in the manner in, each being adapted to have an end of said cable to pass 
just described, they are inserted in apertures 117, 19 as therethrough and to be compressed so as to join the 
shown, and the extremities of nylon cord 14 are pulled two ends of said cable whereat said shrinkable collars are 
so that nylon cord 14 is put under tension. Then retaining positioned SO that said elastic cord is pre-loaded while 
sleeve 13 is crimped so that those portions of cable 11 55 said fiberglass cover is under a no-load condition, 
within apertures 17, 19 are gripped tightly and prevented 4. A tie-down mechanism for restraining various ap- 
from moving. Finally, the exposed extremities of nylon pendages of a space vehicle to a rocket booster until 
cord 14 are tied together into a square knot which, in such predetermined time as when said appendages are 
conjunction with retaining sleeve 13, forms joint 12. to be extended, comprising: a cable having an elastic 
In summary, it can be stated that tie-down mechanism 60 cord member that can withstand such temperature and 
10, because of nylon cord 14 being elastic, compensates pressure conditions as are generally associated with said 
for the expansion of rocket booster 6 about which it is rocket booster in flight, and a strong covering material 
disposed, due to variations in temperature and pressure loosely surrounding the length of said cord member and 
when the space vehicle is in launch and flight phase. On capable of withstanding rather abnormally high tempera- 
the other hand, should nylon cord 14 fail for any reason 65 ture and pressure conditions as exist when said rocket 
whatsoever, then the appendages will open very slightly booster is in fight, said covering material being slightly 
and fiberglass covering 18 will take over to restrain longer than said elastic cord member when said cord 
these appendages from erecting. Accordingly, fiberglass member is in its unstretched condition, 
covering 18 provides the “fail-safe” feature for the tie- 5. The tie-down mechanism of claim 4 further includ- 
down mechanism 10. 70 ing a means for joining the ends of said cable sulch that 
At a predetermined time and just prior to the separa- said elastic cord member is pre-loaded and said covering 
tion of satellite 3 from booster stage 6, cutting devices 15 material is under a no-load condition. 
sever cable 11, thereby permitting -yelease of solar cell 6. The tie-down mechanism of claim 5 further includ- 
paddles 5 and booms 4 so dhat’they can assume their ing a cutting means associated therewith for severing 
desired position relative to the satellite. It should be un- 75 said cable at said such predetermined time. 
3,350,034 
5 6 
7. A tie-down means comprising a cable having an ends of said cable, placing an outer shrinkable collar over 
elastic inner member and an outer temperature-resistant, said cover at each of said ends of said cable and sucbstan- 
essentially non-elastic covering member surrounding said tially 'coaxial with said inner collar thereat, inserting said 
inner member and extending slightly beyond the length ends of said cord through apertures in a retaining mem- 
of said inner member when said inner member is in its 5 ber such that said collars are contained in and extend 
unloaded condition; and a retaining means for tightly slightly out of said apertures, and crimping said retain- 
'gripping the ends of said cable and forming a joint such ing member to tightly grip said ends of said cable. 
that said inner member is pre-loaded and said covering 
is under a no-load condition. References Cited 
UNITED STATES PATENTS 8. A method of forming a tie-down mechanism of a cable type for restraining satellite appendages to a rocket 
booster, wherein said cable includes an elastic ,cord sur- 2,712,509 711955 Biefeld _ _ _ _ _ _ _ _ _ _ _ _ _ _  57-140 
rounded by a woven fiberglass covering slightly longer 2,768,925 10/1956 Fay _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  57-140 
than said elastic cord, said method comprising the steps 3,047,259 7/1962 Tatnall et al. _ _ _ _ _ _ _ _ _  244-1 
of: bunching said covering to expose the extremities of 16 3,078,755 2/1963 Chace __________-._-___ 87-6 
said cord, inserting an inner shrinkable collar between 
said cord and said covering substantially at each of the FERGUS S. MIDDLETON, Primary Emminer. 


Satellite appendage tie down cord Patent

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