NASA

Technical

Memorandum

NASA TM- 100395

DEFINITION OF LARGE COMPONENTS ASSEMBLED

ON-ORBIT AND ROBOT COMPATIBLE MECHANICAL JOINTS

By J. Williamsen, F. Thomas, J. Finckenor, and B. Spiegel

Structures and Dynamics Laboratory

Science and Engineering Directorate

April 1990

(NASA-IH-IO0399) OEFINITION OF LARGE

COMPONENTS ASSEM_EED ON-ORBII AND ROBOT

COMPATIBLE MECHANICAL JnINTS (NASA) 4_

CSCL

N/ A

Nationa! Aeronautics and

Space Ad min,stration

George C. Marshall Space Flight Center

P

13I

G.t/J7

N90-22043

MSFC- Form 3190 (Rev. May 1983)

Report Doc u m e ntatio n-

',t ., ,,,trt,+,, .h +1, q+

1. Report No. 2. Government Accession No+

NASA TM-100395

4. Tith. and Subtith;

Definition of Large Components Assembled On-Orbit and

Robot Compatible Mechanical Joints

7, A.thor(s)

ft. Williamsen, F. Thomas, J. Finckenor, and B. Spiegel

Performing Organization Name and Address

George C. Marshall Space Flight Center

Marshall Space Flight Center, Alabama 35812

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546

i15.

3. Recipient's Catalog No.

5. Report Date

April 1990

6. Performing Organization Code

8. Performing Organization Report No.

10. Work Unit No.

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

Supplemenlary Notes

Prepared by Structures and Dynamics Laboratory, Science and Engineering Directorate.

16. Abstracl

One of four major areas of project Pathfinder is in-space assembly and construction. The

task of in-space assembly and construction is to develop the requirements and the technology

needed to build elements in space. _ _

This paper identifies _ 120-ft diameter tetrahedral aerobrake truss as the focus element.

A heavily loaded mechanical joint is designed to robotically assemble the defined aerobrake element. Also, typical large components such as habitation modules, storage tanks, etc., are

defined, and attachment concepts of these components to the tetrahedral truss are developed.

17 Key Words (Suggested by Authorls))

Mechanical Joints

In-Space Assembly

Large Components

18. Distribution Statement

Unclassified/Unlimited

19. Securily Classil. (ol lhi5 report)

Unclassified

20. Security Classif. (of this page)

Unclassified

I 21. No. of pages 22 Price

4 2 1 NTIS

NASA FORM 1626 OCT 86

For sale by the National Technical Information Service, Springfield, VA 22161-2171

TABLE OF CONTENTS

1. INTRODUCTION ......................................................................................

II. AEROBRAKE STUDIES .............................................................................

1II. TRANSITION TRUSS .................................................................................

IV. LARGE COMPONENTS ..............................................................................

V. MECHANICAL JOINTS ..............................................................................

VI. CONCLUSION .........................................................................................

REFERENCES ..................................................................................................

BIBLIOGRAPHY ..............................................................................................

APPENDIX A--STRESS ANALYSIS ......................................................................

Page

1

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11

16

20

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29

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PRECEDING PAGE BLANK NOT FILMED

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_,__,..IN_NTJONAUZ BLANK
LIST OF FIGURES

Figure

!.

2.

3.

4.

5.

6.

7.

8.

9.

10.

!1.

12.

13.

14.

15.

16.

17.

18.

Title Page

Vehicle definition study ............................................................................ 3

Pathfinder aerobrake configuration ............................................................... 4

Aerobrake truss element loading definition ...................................................... 5

Aerobrake truss element loading definition detail ............................................... 6

Four-point payload constraint ...................................................................... 7

Eight-point payload constraint ..................................................................... 8

Axial load versus element number, four-point payload constraint ............................ 9

Axial load versus element number, eight-point payload constraint ........................... 10

Variation of axial load .............................................................................. 12

Transition truss - aerobrake support structure ................................................... 13

Transition truss - spherical components .......................................................... 14

Transition truss- cylindrical components ........................................................ 15

Threaded screw joint ................................................................................ 2 l

Threaded screw joint mating sequence ........................................................... 22

Grip joint configuration ............................................................................. 23

Grip joint ............................................................................................. 24

Clevis joint mating sequence ....................................................................... 26

Slip joint .............................................................................................. 27

iv
LIST OF TABLES

Table

1.

2.

3.

Title Page

Large components required for Earth departure ................................................. 17

Large components required for Earth return from Mars ........................................ 18

Large components thermal and radiation protection ............................................ 19

V

TECHNICAL MEMORANDUM

DEFINITION OF LARGE COMPONENTS ASSEMBLED ON-ORBIT

AND ROBOT COMPATIBLE MECHANICAL JOINTS

I. INTRODUCTION

The Pathfinder Project was conceived to develop the technology required for future space

flight missions, such as establishing a permanent presence on the Moon, a manned mission to

Mars, or a combination of both. There are"four key areas to Project Pathfinder: in-space assembly

and construction, extraplanetary exploration (including remote surveillance and surface exploration,

humans-in-space (including closed-loop life support and space medical science), and transfer vehicle

technology (providing the means for leaving and returning to low Earth orbit).

The Pathfinder in-space assembly and construction activity focuses on the technology that is

needed to construct large, massive, and complex vehicles in space. The program is intended to

provide a wide range of design options that are independent of any particular vehicle or platform

concept. There are four main objectives for this task:

1. Define methodologies for constructing generic spacecraft components, such as aerobrake

shells, backbone trusses, and pressurized modules, that can be applied to a variety of different

missions.

2. Develop processes for joining components in space, including welding, bonding, and

mechanical fastening.

3. Develop the ability to manipulate and precisely position elements and large components

so that they can be joined.

4. Define the facility layout and infrastructure that would be required to support the construction of entire large space vehicles and platforms in orbit.

NASA/Marshall Space Flight Center (MSFC) is responsible for defining generic large spacecraft components and the methods for building them on orbit, including welding and mechanical

joining processes. The primary purpose of this report is to document (1) the definition of some

"typical" large components in space, and (2) the development of joint load requirements and concepts for use in assembly of large space components.

Ih AEROBRAKE STUDIES

The Structures Division at MSFC had previously performed several studies to further define

"typical" configurations, loads, and packing requirements for aerobraked vehicles. This work was
doneprimarily to support mechanical joint detailed design for in-space assembly and construction.

During this early work, a search for mission studies utilizing aerobraked vehicle concepts was

performed. The studies of greatest interest and value are listed in the bibliography.

Through analysis of these reports and discussions with Langley Research Center (LaRC), the

"generic" vehicle concept shown in Figure I emerged as the baseline for the studies. As can be

seen, this vehicle concept is based upon a 120-ft (36.57-m) diameter aerobrake with a spherical

surface. This aerobrake would be assembled on-orbit using hexagonally shaped thermal panels

attached to a tetrahedral truss structure. Large components would be attached to the back side of

the aerobrake truss through an intermediate or "transition" truss (see Section III, Transition Truss,

and Section IV, Large Components). Figure 2 shows a detail of the basefined aerobrake structural

assembly. The concept, while not intended to represent an optimized design, did make possible a

derivation of first-order requirements for heavily loaded structural joints which were used in the

MSFC detailed design efforts (see Section V, Mechanical Joints).

A finite element model of the baseline aerobrake structure was then developed in order to

identify loads at mechanical joints within the aerobrake truss using MSC Pal, a personal computer

version of NASTRAN. For the purpose of this model, the spherical aerobrake profile was approximated as fiat, as shown in Figure 3. Figure 4 outlines further assumptions made in the configuration and exterior loading of the aerobrake model. The hexagon size chosen for the thermal panels

was 14.5 ft (4.42 m) from comer to comer, the maximum size that could be stacked within the

space transportation system orbiter bay. From this, the total number of thermal panels for the

aerobrake was derived as 61, yielding a total aerobrake area of 8,330 ft 2 (773.88 m2). The length

of each of the aerobrake struts, 12.55 ft (3.83 m) from node center to node center, was also

derived from the size assumed for the aerobrake panels (with three struts forming the equilateral

triangular support base for each aerobrake panel). The thickness of the overall aerobrake structure,

10.25 ft (3.12 m), results from the geometry of placing struts of this size within a tetrahedral

arrangement. It is important to note that a spherical aerobrake profile would result in a number of

different sizes of struts within the aerobrake truss (rather than the one size determined for the flat

truss) with an accompanying increase in assembly complexity.

The point loads applied to all of the "front" aerobrake truss nodes (facing the "windstream"

during aerobraking) were derived from the vehicle mass and decelerations quoted in Reference 1,

as pictured in Figure 4. While these loads were applied to the "front" of the aerobrake, the modc_

was constrained from motion at the "rear" of the aerobrake truss in three different constraint cases,

modeling three different payload attachment conditions. Case ! was a four-point "payload" constraint of model motion at the nodes shown in Figure 5. Case 2 was an eight-point "payload" constraint of model motion at the nodes shown in Figure 6. Case 3 was a multipoint constraint of all

model nodes in the lower half of the aerobrake model.

The results from constraint Cases ! through 3 are shown in Figures 7 through 9. Figure 7

shows that for the four-point payload constraint (Case 1), maximum loads in the truss members

varied from +200,000 lb (887.6 kN) to-!20,000 lb (-533.76 kN) with the largest loads concentrating in the members around the four nodes of constraint. Fi.gure 8 shows that for the eightpoint payload constraint (Case 2) maximum loads in the truss members were lower, varying from

+240,000 lb (1,067.52 kN) to -140,000 lb (-622.72 kN) with the largest loads concentrating in

the members around the eight nodes of constraint. Case" 3, the multipoint payload constraint,

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showed a roughly equal load in all aerobrake truss members of 13,000 lb (57.82 kN). Loadings for

all three cases are broken down by percentages into several ranges and are shown in Figure 9. It

was noted that most of the truss member loads (>90 percent) were below 100,000 lb (444.80 kN)

in magnitude, even for the worst case constraint (Case 1). This finding, combined with the reasoning that more than eight points of payload connection were probable in the case of a "real"

aerobrake, led to the establishment of a 100,000-1b (444.8 kN) load as the preliminary load criteria

for mechanical joint design (see Section V, Mechnical Joints).

III. TRANSITION TRUSS

The purpose of the transition truss task was to develop concepts and requirements for

attaching large components to an aerobrake truss. A transition truss is defined as the arrangement

of structural members that support and connect large components to an aerobrake truss. The

components selected for attachment to the aerobrake were typical large and heavy components

representative of the data in Section IV, Large Components. The aerobrake configuration for this

study was a 120-ft (36.57-m) diameter tetrahedral truss as described in the Aerobrake Study. The

plane view of the tetrahedral truss, upon which large components would be attached, is shown in

Figure 10. Two types of large components were used to characterize typical transition truss configurations--a 12.91-ft (3.94-m) diameter spherical, liquid oxygen (LOX) tank, and a 42-ft (12.80-

m) long by 14.5-ft (4.42-m) diameter Space Station Freedom laboratory module. Figure II shows

the 12.91-ft (3.94-m) LOX tank and how it is mounted and restrained on the aerobrake. The tank

is arranged, and the transition truss structure designed, so that it would easily attach to the

aerobrake truss. The LOX tank is connected to the aerobrake truss by six transition truss members

at 60-degree locations that correspond to six node locations on the aerobrake truss. Diagonal

members are placed between alternating transition truss members to provide for torsional stiffness.

Figure 12 shows the Space Station Freedom laboratory module and how it might be

mounted and restrained to the aerobrake truss. The module is arranged, and the transition truss

structure designed, so that it would easily attach to the aerobrake truss. The module is connected to

the aerobrake truss with four transition truss members and at one keel location, similar to its structural attachment to the space transportation system (STS) cargo bay. The keel attachment is made

at the front of the cylinder to an aerobrake truss node.

Preliminary axial loads were determined by building a three-dimensional finite element

model of a 12.91-ft (3.94-m) 80,356-Ib (357.42-kN) sphere and a 42-ft (12.80-m) long by 14.5-ft

(4.42-m) diameter 64,328-1b (286.13-kN) cylinder. The transition truss members were attached to

the components and attached to the appropriate location on the aerobrake. The aerobrake, for this

analysis, was assumed to be infinitely rigid. The aerobrake node end of the transition truss

members was restrained in various configurations to determine which method of constraining would

result in the lowest axial loads. A 3.0-g deceleration in the vertical direction and a 1.0-g deceleration in each of two transverse directions was applied to the sphere and to the cylinder. The nodes

restrained as shown in Figures I1 and 12 resulted in the lowest axial loads in the transition truss

members for this transition truss configuration. The axial loads on the spherical tank and the cylinder struts range from -71,000 lb (-315.81 kN) to 160,000 lb (711.68 kN) and -34,000 lb (-151.23

kN) to 35,000 lb (155.68 kN), respectively.

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IV. LARGE COMPONENTS

The purpose of the large components task was to determine possible vehicle components for

aerobrake attachment, including such components as fuel tanks, cryogenic tanks, pressurized habitation modules, liquid storage tanks, and unpressurized storage tanks. Once these types of

components were identified, the size, shape, volume, mass, and thermal and radiation protection

were determined as shown in Tables 1, 2, and 3. These components will be used in defining the

axial loads in the transition truss that connects the components to the aerobrake (see Section III,

Transition Truss). The specific details of the large components described were taken from previous

interplanetary mission studies [2,3] that defined the size of tanks, modules, descent stages, etc.,

required for particular missions and aerobrake sizes. The propulsion system used on all the studies

was LOX and liquid hydrogen (LH2) with a mixture ratio of six to one. The tank weights include

the total propellant used plus the additional amount needed to compensate for propellant boiloff

during the assembly, checkout, and travel time to and from Mars.

The optimum pressure vessels for use in space vehicles are spherical but are limited in size

by the existing transportation vehicles. In the aerobrake vehicle studies evaluated, the transportation

vehicle varied with each study. To get a representative database, a single cargo vehicle (the

Advanced Launch Vehicle) was baselined for use in this study which features a 43- and 45-ft

(13. l 1-and 13.72-m) diameter cargo bay. Table 1 shows typical large components that might be

required for a manned mission to Mars. These components would have to be assembled to the

vehicle in low Earth orbit, checked out, transported to Mars, and then be used for the return trip to

Earth. Table 2 shows typical large components that might be used to propel a manned vehicle

toward Mars. These components would be attached to the vehicle, checked out on-orbit, then

expended when the desired specific impulse was achieved. Tables 1 and 2 show the variation in

sizes of LOX tanks and LH2 tanks required to contain the "typical" volume of propellant required

for planetary exploration missions, according to the referenced studies. These charts show the size

difference between using a single LOX tank and LH2 tank using a number of smaller diameter

tanks that would carry the same propellant weight. Given these "typical" propellant volumes and

tank sizes, the tank thickness and weight were then determined by assuming a low pressure pumpfed propellant storage tank. The design pressures for the LOX tank and LH2 tank were 23 psi

(158.58 kN/m 2) and 50 psi (344.75 kN/m2), respectively.

Table 3 shows the typic_il insulation required for the propellant tanks for the journey to

Mars. The tanks used to propel the vehicle out of low Earth orbit would require less insulation

because the boiloff rate is comparatively small and the time these tanks are in use is comparatively

short to those used in deep space.

ttr.

V. MECHANICAL JOINTS

Much work has been devoted to the development of mechanical joint concepts for in-space

construction and assembly. Initially, these concepts for attaching struts to truss nodal points were

required to satisfy only two major criteria. First, the joint designs had to maintain sufficient

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strength in order to withstand aerobrake induced loads of 100,000 lb (444.80 kN) in tension or

compression. Second, they had to have the capability of being assembled from the side. These

preliminary conditions are still valid; however, more mechanical joint requirements have evolved

and have been incorporated accordingly into the following joint designs. All joints are composed of

two parts: the connector and receptacle. The connector is attached to the strut and the receptacle is

attached to the node.

A. Threaded Truss Joint

The first mechanical joint, the threaded truss joint, that was designed is displayed in Figure

13. In this particular design, an outer alignment joint surrounds a stronger mechanically driven

threaded joint. This joint was designed to meet the 100,000-Ib (444.80-kN) axial load and robot

assembly requirements. The assembly of this joint requires the robot to perform two operations--place the element near the attachment location and turn a bolt. A temporary outer alignment

feature holds the position of the element after it has been placed near the receptacle, then a robot

turns a standard hex head bolt. However, after this joint design was in its final stages, a new

requirement was established. The mechanical joint needs the capability to adjust node centers from

a ---0.020-in (+--0.0508-cm) axial misalignment within a truss structure to a "true" position. This

joint was modified (Fig. 14) to meet this requirement by redesigning the temporary alignment

sleeve, and providing tapered surfaces to push the element into position. As the threaded section is

rotated, the tapered surfaces on the threaded section force the element end up or down against the

tapered surfaces on the tube end. The tapered surfaces on the tube transfer the force into an axial

load, pushing the element into the correct position. These modifications required an excessive

number of parts, and made the assembly torque prohibitively high, approximately 4,000 in-lb

(45,192 N-m) Also, these redesigns made the joint longer and consequently heavier. For these

reasons the threaded truss joint was deemed too complicated and was shelved.

B. Grip Joint

The second concept, the grip joint, was designed to the requirements of robotic assembly,

___100,000-1b (444.80-kN) axial load and a _+0.020-in (_0.0508-cm) misalignment correction and

is shown in Figure 15 and 16. The assembly of the joint requires a robot to perform the same two

operations as for the threaded truss joint--placing the element and turning a bolt. As the robot

brings the element near its final position, the bolt engages a "zip nut©, '' and the joint's grooves

become roughly lined up. Then the robot turns a standard hex head bolt aligning the connector and

receptacle to the final "true" position.

The "zip nut ©'' is an independently designed and patented nut, in which the threads are cut

into three segments and spring loaded. This allows a bolt to be pushed into it, then tightened by a

single rotation. This not only reduces assembly time by saving the robot 30 or 40 revolutions of an

end effector, but saves weight by eliminating a temporary alignment feature such as that in the

threaded truss joint.

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As the bolt is tightened, its tension pulls the axisymmetric inclined planes of the grooves

together. The inclined planes transfer the vertical force to the bolt into an axial force which

stretches or compresses the element until it is in the correct position. The maximum axial load

required to position the elements is about 5,000 lb (22.24 kN), found by the elastic deformation of

a beam under axial loading.

There were several design considerations in this joint: shear area of the grooves, stress concentrations caused by the grooves, bolt loading and torque requirements, bending moments along

the axis of the gripper sections, and bending moments acting to open the semicircular gripper

sections (large moments could be countered by adding tabs on the edges of the element and node

that would prevent gripper section deformation past a certain point).

The grip joint, while not having been optimized, is now being built out of several materials

including 2219-T87 aluminum, titanium 6AI4V alloy, and an "isotropic" 20-percent silicon carbide

aluminum 2124 metal matrix composite. The grip joint is being fabricated from these materials to

determine which material will optimally meet the strength, weight, and coefficient of thermal

expansion requirements established for in-space assembly and construction. Tension and torque tests

are scheduled to be performed in early CY 1990. Tension and compression tests in a thermal

vacuum chamber may be scheduled if preliminary test results are positive.

C. Clevis Joint

The third mechanical joint, the clevis joint, is displayed in Figure 17. This design incorporates a tang and clevis concept. As the bolt engages the "zip nut©, '' the two cones are pulled

into a locked position, thus producing a double wedge effect. Further analysis of this joint yielded

mechanical and fabrication complexities which resulted in shelving the concept.

D. Slip Joint

The fourth concept, the slip joint, is pictured in Figure 18. This design is still undergoing

preliminary analysis and feasibility studies. Both halves of the joint are conically shaped and are

wedged into a locked position by the bolt engaging a "zip nut©. '' Two new mechanical joint

requirements are being applied to this current concept. First, the joint must be disassembled as

easily as it is assembled. Second, not only should the joint possess the capability of being assembled by a robot, but by an astronaut as well. Much more work is required to solidify this concept.

Vh CONCLUSION

A generic space structure for studying in-space assembly and construction was developed by

NASA to determine the technology required for building large structures in space. The space structure defined was a 120-ft (36.57-m) diameter aerobrake, i.e., thermal insulation supported by a

tetrahedral truss with manned facilities and engines attached to the tetrahedral truss. An analysis of

25
INITIAL

PLACEMENT

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26
TRUSS ELEMENT

NODE

Figure 18. Slip joint.

27
the structure was performed to define load requirements for the design of mechanical joining

methods. Four methods of mechanically connecting truss elements via a robot were investigated.

One, the grip joint, was designed and is being built.

Research was initiated to define the types of large components that might be attached to the

aerobrake for interplanetary missions. A task was performed to determine an optimum method of

attaching the components to the tetrahedral truss. Two large components, a 12.91-ft (3.94-m)

diameter LOX tank and a 42 by 14.5-ft (12.8 by 4.42-m) Space Station Freedom laboratory

module, were used to define loads and attachment schemes for connecting these components to the

tetrahedral truss.

28
REFERENCES

lo

,

.

.

Boeing, Marshall Space Flight Center, "Analysis of Technologies for Manned Lunar and Mars

Missions." Contract NAS8-137. NASA-Marshall Space Fight Center, 1989.

NASA-Marshall Space Flight Center, "Mars Exploration--Split Sprint Mission Low Earth

Orbit Assembly Versus Ground Assembly." NASA-Marshall Space Flight Center, April 1989.

Martin Marietta, NASA-Marshall Space Flight Center, "Orbital Transfer Vehicle Concept

Definition and System Analysis Study." NASA-Marshall Space Flight Center, October 1985.

FED-STD-H28/2A, April 1984. Table II.B.I Formulas for Screw Thread Strength Factors.

BIBLIOGRAPHY

Boeing, NASA-Ames, "Engineering Analysis for Assembly and Checkout of Space Transportation

Vehicles in Orbit." NASA-Ames Research Center, October 20, 1989.

Dauro, V.A.: "Aerobraking." NASA Report No. N87-17784. Marshall Space Flight Center, 1987.

Hill, O., and Wallace, R.: "Manned Mars Mission Vehicle Design Requirements for Aerocapture."

NASA-Johnson Space Center, Report No. N87-17781.

Hoffmen, S.J.: "A Comparison of Aerobraking and Aerocapture Vehicles for Interplanetary Missions." NASA Headquarters contract No. NASW-3622.

Meenes, G.P.: "Aeroassisted-Vehicle Design Studies for a Manned Mars Mission." 38th Congress

of the IAF, Report No. IAF/IAA-87-433, NASA Report No. A88-16097.

Park, C.: "A Survey of Aerobraking Orbital Transfer Vehicle Concepts." AIAA 25th Aerospace

Sciences Meeting, Report No. AIAA-87-0514, NASA Report No. A87-22619.

29
APPENDIX A

Bolt

A

100,000 Ib

Flat Plate Analogy

View A

Px=100,000 ib

Py=BOLT LOAD

0=60 °

3O
R=1.529 inches

3/4" bolt, Ftu = MINIMUM TENSILE STRENGTH 126,758 psi per

MS90727

Assumption: I_ = .10

T_,Fx=O P x-P nSlN e-!_ P nOeS 0=0

Pn= Px

en=

SINe+I_ COSe

100,000

= 109,167 Ibs

SIN 60 ° + .I(C0S 60 °)

T_Fy=O Py+_PnSIN0- PnCOSe=0

Py= Pn(COSe-_ SINe)

P y = 109,167 (COS (600) - (.1) SIN (60°))

P y = 45,129 Ibs

Calculation of the bolt load, P y, assumed a flat plate.

the part is actually a circle.

However,

31
i

Pr (Ibs/in)

de Py ---Pr (2 = R )

-_r = 45,129

i

Pr = 4,698 Ib/in

Py* is defined as the actual bolt load on the circular section of

the joint.

m n

Py*= P r COS e ds = P r COS 0 R de

m

Py* = 4P r R 1"90COS e de = 2 Pr R

0

Py* = 4(4,698 Ibs/in)(1.529 in) = 28,733 Ibs

Margin of Safety (Bolt):

_tu bolt = 56,000/[= (.3752)]= 126,758 psi

_*= Py*/Area of 3/4" bolt=28,733/[= (.3752)]=65,038 psi

M.S.= _tubolt -1 = 126,758 1 =+0.39

F.S. _* i.4(65,038)

32
where:

SHEAR AREA OF EXTERNAL THREADS (NUT):

Area = ]-[nLeKn(max)[1/(2n) + 0.57735 (Es(min)-Kn(max))] (4)

n = Number of threads per inch = 16

L _ Length of thread engagement ---3/4 in (scaled)

cKn(max) = Maximum minor diameter of internal

threads = 0.6908 in

Es(min) = Minimum pitch diameter of external

threads = 0.7079 in

Fsu = 0.57 (Ftu) = 0.57 (126,758) = 72,252 psi

Area = ]-[ (16)(3/4)(0.6908)[1/(2(16)) + (0.57735)

(0.7079-0.6908)]

= 1.07 in2

(_= Py* / Area = 28,733 Ibs / 1.07 in2 = 26,850 psi

M.S. = 72,252/[(1.4) (26,850)] -1 = +0.92

SHEAR AREA OF INTERNAL THREADS (BOLT):

Area = ]-[nLeDs(min)[1/(2n) + 0.57735 (Ds(min)- En(max))]

where: Ds(min) = minimum major diameter of external

threads =0.7406 in

En(max) = maximum pitch diameter of internal

threads = 0.7179 in

33
Area = ]](16) (3/4) (0.7406)[ 1/(2(16) + 0.57735 (0.7406-

0.7179)] =1.238 in2

c = py* / Area = 28,733 Ibs / 1.238 in2 = 23,209 psi

M.S. = [72,252 / (1.4) (23,209)]- 1 = +1.22

SHEAR AREA OF INTERNAL THREADS .(NODE TUBE):

Area = RnLeDs(min)[1/(2n ) + .57735 (Ds(min)- En(max))]

n=2

Le = 1.341 in

Ds(min) = 3.115 in

En(max) ) = 2.9325 in

Fsu = 34,000 psi per MIL- HDBK-5E, table 3.2.6.0 (c)

Area= _(2)(1.341)(3.115)[ 1/(2(2)+ 0.57735 (3.115 - 2.9325)]

=9.327 in2

= F / Area = 100,000 Ibs / 9.327 in2 = 10,722 psi

M.S. = [34,000 / (1.4) (10,722)] - 1 = +1.26

SHEAR AREA OF EXTERNAL THREADS (NODE TUBE):

Area = RnLeKn(max)[1/(2n ) + 0.57735 (Es(min)-Kn(max)) ]

n=2

Le = 1.341 in

34
Kn(max) = 2.745 in

Es(min) = 2.93 in

Fsu = 34,000 psi per MIL- HDBK-5E, table 3.2.6.0 (c)

Area = ]-[(2)(1.341)(2.745)[ 1/(2(2)+ 0.57735 (2.93 - 2.745)]

=8.2525 in2

= F / Area = 100,000 Ibs / 8.2525 in2 = 12 118 psi

M.S. = [34,000 / (1.4) (12,118)]- 1 = +1.00

THIN TUBE SECTION (NODE TUBE)

3.5 in 4.0 in

Area = ]-[/4 [ (4.0) 2- (3.5) 2 ] = 2.9452 in2

= 100,000 Ibs / 2.9452 in2 = 33,954 psi

F.S. = 1.1 on yield

Fcy = 40,000 psi

(for T852)

per MIL-HDBK- 5E, table 3.2.6.0 (c)

35
M.S. = [40,000 / (1.1) (33,954)]-1 = +.07

SHEAR AREA OF EXTERNAL THREADS

Area = ]-[nLeKn(max)[i/(2n ) + 0.57735 (Es(min)-Kn(max))]

n=8

Le = 1/2 (2.5) = 1.25 in (assumed 1/2 of length of

threads)

Kn(max) = 4.0 in

Es(min) = 4.125 in

Fsu = 34,000 psi per MIL- HDBK-5E table 3.2.6.0 (c)

Area = _(8) (1.25)(4.0)[ 1/(2)(8) + 0.57735 (4.125-4.0)]

=1 6.923 in2

(_= F / Area = 100,000 Ibs / 16.923 in2 = 5,909 psi

M.S. = [34,000 / (1.4) (5,909)]-1 = +3.11

STRESS AROUND BOLT HOLE;

b 4.5°

Z

a

t

I _ 100,000 tbs

I R = 2.125 in

R = 1.623 in

36
b = 9/16 in (.5625) scaled from drawing

Area = Area a + Area b

Area = 1-[ { [ (2.125) 2- (1.623) 2 ] + [ (1.623) 2- (1.623- .5625)2]}

= 10.65 in2

= F / A = 100,000 / 10.65 = 9,389 psi

Assuming a stress concentration factor of 3.0 around the hole,

_hole = 3.0 (9,389) = 28,170 psi

for Ftu = 56,000 psi

M.S. = [ 56,000 / (1.4) (28,170) ]-1 =+ .42

for Fcy = 40,000psi

M.S. = [ 40,000 / (1.1) (28,170) ]-1 =+.29

37
APPROVAL

DEFINITION OF LARGE COMPONENTS ASSEMBLED ON-ORBIT AND ROBOT

COMPATIBLE MECHANICAL JOINTS

By J. Williamsen, F. Thomas, J. Finckenor, and B. Spiegel

The information in this report has been reviewed for technical content. Review of any

information concerning Department of Defense or nuclear energy activities or programs has been

made by the MSFC Security Classification Officer. This report, in its entirety, has been determined

to be unclassified.

JAM_¢_S C. BLAIR

Director, Structures and Dynamics Laboratory

38 _U.S. GOVERNMENT PRINTING OFFICE 1990--731 061/20089