Support techniques for restraint of slender bodies such as launch vehicle

Herr, R. W.

English

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https://ntrs.nasa.gov/search.jsp?R=19690012178 2020-03-16T18:21:52+00:00Z
United States Patent 
3,421,363 
HARNESS POW VERTICALLY SUPPORTING SEEN- 
DER BODIES FOR VIBRATION TESTING 
Robert W. Herr, Mampton, Va., assignor to the United 
States of America as represented by the Administrator 
of the National Aeronautics and Space Administration 
Piled July 1, 1965, Ser. No. 449,011 
U.S. C1. 73-67.2 4 Claims 
Int. C1. GOln 29/00 
10 
ABSTRACT OP THE DISCLOSURE 
A restraint harness for a vertically oriented, long, 15 
slender body. A support structure has snpport cables tied 
to it and to the body being supported. The support cables 
are located entirely below the center of gravity of the 
body. Restraint cables are connected to the body at points 
above the center of gravity of the body, entrained over 20 
pulleys anchored to the support structure, and fixed to 
the support cables completing the harness. 
The invention described herein may be manufactured 25 
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. 
This invention relates to a restraint system for slender 
bodies standing on their end, and more particularly to a 30 
restraint system which has a mini~nal effect on the free- 
free lateral vibration mode shapes and freq~~encies of 
the slender body. 
The restraint system here under consideration has par- 
ticular use in the testing of slender bodies, such as a 35 
spacecraft launch vehicle, for their response to vibratory 
inputs. The simulation of the free-free flight condition 
during ground vibration tests is made difficult by the fact 
that a massless elastic restraint added to the vehicle at 
any location other than a nodal point generally will yield 
measured frequencies higher than the actual free-free 
frequencies. The frequency increase caused as a result of 
the restraint system is dependent upon both the location 
and the magnitude of the restraint. Thus, one solution 
to the problem would appear to be to apply the restraints 45 
only at the nodal points of the vehicle. Practically, how- 
ever, this is generally not possible, particnlarly with a 
space vehicle of the liquid fuel type which must be ori- 
ented vertically. This is true since the only part of the 
structure capable of supporting the entire weight of the 50 
vehicle is at the base where the engine thrust is trans- 
mitted to the structure. 
Since it is necessary to stand the vehicle on its base, 
it has been determined that a rotational spring constant 
equal to the product of the weight and the distance from 55 
the base to the center of gravity must be provided to 
keep the vehicle from toppling. This has resulted in a 
technique of attaching a spring at the base of the vehicle 
to provide pitch restraint and thus keep the vehicle from 
toppling. This arrangement has the advantage of requir- 60 
ing no massive extraneous structure to support the ve- 
hicle; however, this type of restraint yields measured fre- 
quencies appreciably higher than the desired free-free 
values, especially for large vehicles. Furthermore, if the 
minimum pitch spring restraint is linear with the pitch G5 
angle, any lateral force, such as a horizontal wind gust, 
can impart velocity to the vehicle which will cause it to 
topple unless caught by safety stops. It has also been 
found that with this arrangement the stiffness of the re- 
straining springs must be changed if the weight of the ve- 70 
hicle is changed, for example, a fueled vehicle as opposed 
to an unfueled vehicle. Thus, it can be seen that this type 
of restraint system is difficult to work with although oper- 
ational to a degree. 
Another restraint system which has been utilized pro- 
vides an arrangement whereby the weight of the vehicle 
is carried by two support cables attached to the bottom of 
the vehicle and to fixed overhead support structure. 
Stability is provided by two horizontal restraint cables 
tied between the support cables and the periphery of the 
vehicle at a point above the vehicle's center of gravity. 
For minimum pitch restraint, the support cables are sepa- 
rated at their attachment points to the overhead support 
structure until the vehicle will just stand erect. The sepa- 
ration distance of the cables is critical and, therefore, 
mechanism usually must be provided on the support struc- 
ture for adjustment of the support cables (such as hori- 
zontal track and dollies). Another difficulty with this ar- 
rangement is that the restraining cables, and hence the 
support cable tiedown points, must be well above the cen- 
ter of gravity of the vehicle, necessitating a tall and mas- 
sive support structure capable of supporting the entire 
weight of the vehicle. This is particularly true when test- 
ing full-scale launch vehicles. 
The invention here under consideration utilizes the 
principle of the last mentioned support system; however, 
provides a novel arrangement thereover by utilizing a 
pulley system in conjunction with the various cables. With 
this arrangement, it is possible to support the weight of 
the launch vehicle by cables that are fixed to the support 
structure at a point well below that of the previous ar- 
rangement. Furthermore, the restraining cables can be 
fixed to the vehicle at a point above the center of gravity 
thereof, thus accomplishing the desired result and over- 
coming the above mentioned difficulties. 
It  is therefore an object of the invention to provide a 
restraint system for slender bodies standing on their end 
with no danger of toppling, yet having a minimal effect 
on the free-free lateral vibration mode shapes and fre- 
quencies thereof. 
Yet another object of the invention is to provide a re- 
straining system for elongated structures standing on their 
end which act as a nonlinear spring in the pitch direction 
resulting in an extremely soft spring when in a vertical 
attitude but rapidly increasing in stiffness with increasing 
angle of tilt. 
Still another object of the invention is to ~rovide a 
restraining system for slender bodies standing on their 
end wherein the support cable tiedown points are well 
below the center of gravity of the body. 
A further object of the invention is to provide a re- 
straining system for slender bodies standing on their 
end wherein tension in the support cablses fixed to the 
base thereof is used to apply just the right amou't of ten- 
sion to restraining cables fixed to the vehicle to keep the 
vehicle from toppling. 
These and other objects and advantages of the inven- 
tion will become more apparent upon reading the specifi- 
cation in conjunction with the acco'mpanying drawings. 
In the drawings: 
FIG. 1 is a perspective view of the restraint system 
showing the restraining cables located inside the support 
cables; and 
FIG. 2 is a modified form of the invention showing the 
restraint cables located outside of the suppoat cables. 
Basically, this invention relates to a restraint system 
for tethering slender bodies resting on one of their ends. 
This is accomplished by fixing support cables to the base 
of the vehicle and anchoring the cables to surrounding 
support structure. The support cables are normally an- 
chored at or below the horizontal plane passing through 
the center of gravity of the slender body. Restraining ca- 
bles are connected to the support cables at some point in- 
3,421,363 
3 4 
termediate their extremities and tied to the slender body Operatioft 
at some point u:ell above its center of gravity. The re- 
straining cables are entrained over a series of pulleys or The restraint systems 10 and 58 operate similarly; there- 
sheaves so that the cables are permitted a limited amount fore, the operation of only the system PO will be explained 
of movement as is the slender body fixed thereto when sub- 5 in detail. The weight of the test body 12 is carried by the jected to vibrations normal to the plane of the support support cables 15 and 16 attached to the base of the ve- 
cables. Tensioning means is placed in the restraining ca- hicle. Stability is provided by the restraint cables 24 and 
bles to provide the Proper pitch restraint. Thus, the test 25 tied between the support cables and the periphery of the 
body is supported wi'thout introducing unnecessary force vehicle at points 26 and 27 above the vehicle's center of 
ComWnents by tensioning the restraining cables to the 10 gravity. For minimum pitch restraint, the length of the 
point that they just hold the test structure erect. restraining cables are adjusted with the turnbuckles 31 
Referring now more specifically to the details of the and 32 such that the tension is sufficient to just hold the 
invention, FIG. 1 shows a restraint System designated gen- vehicle erect. This keeps the test body in a vertical at- 
erally by Ihe reference numeral 18. titude with zero pitch frequency for small amplitudes of 
The system 10 is shown associated with a test 15 oscillation. The same result is obtained with the embodi- in the form of a launch vehicle 12; however, the technique ments shown in FIGS. 1 and 2. ~h~ location of the re- 
may be utilized with any slender body w!lich is resting on straint cable coupler pnlleys inside or outside of the sup- 
its end. Eyes l5 and l4 are fixed the base the port cables is primarily for ease in setting up the restraint 
vehicle 12 in a conventional manner such as by threaded system. ~ ~ t h  arrangements are equally effective in re- 
fasteners or welding. These eyes are located at opposite 20 straining the test body and have a minimal effect on the 
points on the test struc'ture. Support cables 15 and I6 are lateral vibration mode shapes and frequencies. fastened respectively to the eyes 13 and 14. These cables From the above description of the invention, the many 
are directed 'pwardly and anchored at points l7 and advantages thereof are believed readily apparent. One ad- 
On support '. The " is shown dia- vantage over the prior art utilizing the support cable tech- 
grammatically as a fixed structure. Obviously, any type of 25 nique is that the support cables can be located lower than 
may be provided it has the neces- the test body center of gravity. This greatly reduces the 
sary properties to support the test body. height of the support tower necessary to support the mass Restraining 24 and 25 are fixed to 
of the test body. Although the support tower must still be the test at points Z6 and 27 On 'pposite sides and approximately of the same height as the test vehicle, the 
mat a position well above the center of gravity of the test 30 
area thereof above the point where the support cables The longitudina1 location of points 26 and 27 may 
are anchored need not have the properties of the vary depending on the shape, size, etc., of the test body. 
This connection is made at a point approximately inter- lower portion since forces of the restraining cables on the 
mediate the ends of the restraining cables. The extremities sheaves this area are a the 
of the restraining cables 24 and 25 are both connected to forces on the supporting cables. The tensioning means turnbuckles 31 at one end and to 32 at the other end. The 35 for the restraining cables is readily accessible, eliminating 
turnbuckles in turn are connected to coupling cables 29 much of the setup time required with previous arrange- 
and 30 which are in turn fixed respectively to the support ments. Obviously, the cost of the restraint system is much 
cables 15 and 16 at a point intermediate their ends. less than previous arrangements, giving results which 
Located in the horizontal plane containing restraining 40 were heretofore difficult to obtain. Furthermore, the sys- 
cable connection points 26 and 27 are sheaves 36, 37, 38, tem simulates as nearly as feasible the unrestrained con- 
and 39. ~h~~~ sheaves are rigidly secured to the support dition of a vehicle in free fall allowing measurement of 
tower 20 in a conventional manner. The restraining cable free-free frequencies. Although the suspension 
24 is entrained over the sheaves 36 and 37, and the re- System here described has been designed primarily for 
strainig cable 25 over the sheaves 38 and 39. pulleys 40 lateral vibration testing, it may be modified for longitu- 
and 41 are rigidly connected to the support tower 20 at 45 dinal vibration testing by the addition of suitable springs 
some point below the place at which the support cables 15 in series with the 
and 16 are anchored at 17 and 18 to the support tower. While a preferred embodiment of this invention and a 
~h~ restraining cable couplers 29 and 30 are entrained modification thereof has been described, it will be under- 
respectively over the pulleys 40 and 41. stood that other modifications and improvements may be 
In the modified form of the restraining system 50, the 50 made thereto. Such of these n~odifications and improve- 
test body or launch vehicle 52 is again a slender body ments as incorporate the principles of this invention are 
supported in ma vertical attitude. The launch vehicle has to be considered as included in the hereafter appended 
eyes 53 and 54 fixed to the base thereof with support claims- 
cables 55 and 56 connected to the respective eyes. These What is claimed as new and desired to be secured by 
support cables are in turn connected to anchor points 57 55 Letters Patent of the United States is: 
and 58 located on the support tower 60. The anchor points 1. A restraining system for vibrating bodies or the like 
57 and 58 are adjacent the test body 52, since the restrain- comprising: a support StrLlctUre for a test body; a plural- 
ing cables and its pulley system are located outside of the ity of cable means fixed to the test body and to the sup- 
supporting cables as opposed to the arrangement shown in port structure at a position below the center of gravity 
FIG. 1. 60 of the test body supporting the weight of the test body in 
Restraining cables 64 and 65 are fastened at their mid- a stabilized position; a plurality of restraining cable 
points to the test body 52 at a point above the center means fixed to said plurality of support cable means and 
of gravity thereof, as in the previous embodiment. These to said test body to assist stabilization thereof; sheave and 
restraining cables are connected to turnbuckles 71 and 72, pulley means engaging with said restraining cable means 
which are in turn connected to restraining cable couplers 65 whereby said restraining cable means are directed below 
69 and 70 that are attached to the support cables at the center of gravity of the test body and to some point 
some point between their extremities. Sheaves 76, 77, 78 above the center of gravity of the test body. 
and 79 are fixed to the support tower and located in the 2. A restraint system for use with shaking apparatus 
horizontal plane of the restraint cables' connection to the or the like comprising: support structure for an elongated 
ltest body. The restraining cables 64 and 65 are entrained 70 object to be vibrated; a plurality of cable means attached 
over the pulleys similar to the arrangement shown in FIG. to the elongated object and support structure below the 
1. Couplers cable pulleys 80 and 81 are fixed to the support center of gravity of the elongated object for supporting 
tower 60 such that they are located outside of the support the weight of and stabilizing the elongated body; and a 
cables 55 and 56. The restraining cable couplers 69 and plurality of restraining cable means tied to the cable 
70 are entrained over lthese pulleys as shown in FIG. 2. 75 means and the elongated object above its center of gravity 
3,421,363 
5 6 
for maintaining the vehicle erect; and guide means fixed located at a point above the center of gravity of said 
to said support structure for directing said plurality of vehicle; said restraining cables being trained over said 
restraining cable means below the center of gravity of sheaves and tied to opposite sides of said vehicle whereby 
the elongated object and to some point above the center a spring restraint of the vehicle is affecte'd. 
of gravity of the elongated object. 5 6. A restraint system for vibrating bodies or the like 
3. A restraint system for use with shaking apparatus as in claim 5 wherein the pulleys are located between 
or the like as in claim 2 wherein said guide means in- the support cables and the vehicle. 
cludes pulley means engaged with said plurality of re- 7. A restraint system for vibrating bodies or the like 
straining cable means to facilitate positioning thereof with as in claim 5 wherein the pulleys are located outwardly 
respect to said elongated object anc! support structure. of the support cables. 
4. A restraint system for use with shaking apparatus 
or the like as in claim 2 wherein tensioning means is References Cited 
linked into said plurality of said restraining cable means FOREIGN PATENTS 
to maintain the elongated object in the proper attitude 749,445 11,1944 
with respect to the support structure without securing the 15 
apparatus in a rigid position. OTHER REFERENCES 
5. A restraint system for vibrating bodies or the like 
~ i ~ ~ ~ ~ ,  ~~h~ S. et al.: ~~~~ i~~~ of ~ ~ ~ ~ ~ i ~ ~ ~ ~ ~ l  
comprising: a towerlike support structure for supporting Vibration Characterislics Obtained from a %-Scale Mod- 
a test body adapted to be placed within said support tow- el and from a Full-Scale Saturn SA-I, Langley Research 
er; eyes fixed to opposite sides of the base of said test 20 center, pub. by O.T.S., Dept. of Commerce for NASA, 
body; a support cable fixed to said eyes and to either side Scientific Library Patent Office Receipt  NO^. 27, 1964, 
of the support structure at points below the center of pp. 2,3,7, 8, 14, 19,29 and 30. 
gravity of the test body; a pair of pulleys carried by said 
support strUcture and located in the plane of said Support RICHARD C. QUEISSER, Pl.imary Examiiler. 
cables; restraining couplers tied respectively to said sup- 25 
port cables at a point between their anchor points and BEAUCHAMP, Exarnirzer" 
being trained over said pulleys; turnbuckles connected to 
said restraining couplers and to a pair of restraining U.S. C1. X.R. 
cables; and sheaves carried by said support structure and 89-1.8; 244-110 
Jan. 14, 1969 W. W. HERR 
HARNESS FOR VERTICALLY SUPPORTING SLENDER 
3,42 1,363 
BODIES FOR VIBRATION TESTING 
Filed July 1, 1965 
FIG. 1 
INVENTOR 
ROBERT W. HERR 
ATTORNEYS 


Harness for Vertically Supporting Slender Bodies for Vibration Testing

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