The extravehicular activity (EVA) ratchet wrench was developed. Shortly after Space Telescope (ST) maintenance simulations began, the need for a specialized maintenance tool arose. With inputs of tool requirements and design recommendations, several development model wrenches were tested in conjunction with ST neutral buoyancy simulations. The wrench design was modified and refined

Loughead, T. E.

Vanvalkenburgh, C. N.

English

NASA Technical Reports Server

 ESSEX 
FINAL REPORT
FABRICATION OF ESSEX EVA RATCHET WRENCHES
Contract NAS8-34925
Prepared For:
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama 35812
Prepared By:
Charles N. VanValkenburgh
Tomas E. Loughead
ESSEX CORPORATION
3322 South Memorial Parkway
Huntsville, Alabama 35801
July 1982
H-82-03
https://ntrs.nasa.gov/search.jsp?R=19820022678 2020-03-21T07:43:25+00:00Z
ESSEX
FOREWORD
This final report is submitted to NASA/MSFC to complete the
requirements of NASA Contract NAS8-34925 for the fabrication and
delivery of flight-qualified EVA ratchet wrenches. The report describes
the end item deliverables as well as the tasks performed in support of
the deliverables.
ESSEX>
FOREWORD
TABLE OF CONTENTS
1.0 INTRODUCTION
2.0 TASK DESCRIPTION
2.1 Fabrication of Three Wrenches
2.2 Establishment of Quality Assurance Plan
2.3 Acceptance Testing
2.4 Cleaning Procedures
2.5 Packing and Shipping
2.6 Design Modifications and Drawing Deviations
3.0 SUMMARY
4.0 CONCLUSIONS AND RECOMMENDATIONS
Page
ii
 ESSIBX 
1.0 INTRODUCTION
The extravehicular activity (EVA) ratchet wrench is the culmination
of over two year's of NASA development work, with the Essex Corporation
performing much of the initial development as well as the final design.
Shortly after Space Telescope (ST) maintenance simulations began, the
need for a specialized maintenance tool arose. With inputs of tool
requirements and design recommendations from Bruce McCandless and
others, Essex fabricated several development model wrenches which were
tested in conjunction with ST neutral buoyancy (NB) simulations. The
wrench design was gradually modified and refined to its present state.
The wrenches will be used on STS-5 and possibly on future flights
including the Solar Max Repair Mission and the Space Telescope
deployment and servicing mission.
This final report describes Essex' fulfillment of the requirements
of NASA contract NAS8-34925. The contract was granted for the
fabrication and delivery of two Essex-designed, flight qualified EVA
ratchet wrenches per drawing number ESEX-82-27-10 for use on STS-5 and
one flight-like prototype for test and evaluation at Johnson Space
Center (JSC). Contract requirements in support of the wrenches included
a quality assurance plan to be administered to the units as well as
acceptance tests, cleaning and packaging to NASA standards, complete
documentation, and appropriate DD 250 forms.
The contract called for one prototype unit to be delivered to JSC
via Marshall Space Flight Center (MSFC) on May 15, 1982, which was
accomplished with the delivery of EVA ratchet wrench serial number 1004.
However, due to minor design changes agreed to by NASA, it was decided
that a second prototype would be delivered identical in design and
fabrication to the two flight wrenches for more accurate translation of
test results to expected flight unit performance. Therefore, EVA
ratchet S/N 1004 was returned to Essex. When the two flight wrenches
{S/N's 1005 and 1006) were delivered to NASA/MSFC on June 25, 1982, a
third wrench (S/N 1007) was sent to replace the S/N 1004 prototype
wrench. The S/N 1007 prototype wrench bore the engraving "NOT FOR
FLIGHT" to distinguish it from the other two wrenches.
I
ESSEX 
2.0 TASK DESCRIPTION
2.1 FABRICATION OF THREE WRENCHES
Three EVA ratchet wrenches were fabricated, finished and assembled
per released Essex Corporation drawing ESEX-82-27-10 (sheets i through
8). All individual parts not purchased from manufacturers were
fabricated in the Essex Machine Shop. Heat treating, engraving, bead
blasting, anodizing, passivating and electropolishing were performed by
local shops on a subcontract basis. The units were assembled by shop
personnel under supervision of MSFC Reliability and Quality Assurance
(R&QA) personnel and the COR.
2.2 ESTABLISHMENT OF QUALITY ASSURANCE PLAN
A quality assurance plan was established by Essex under the
supervision and approval of the MSFC Reliability and Quality Assurance
Office. This plan was implemented in the fabrication and delivery of
three EVA ratchet wrenches for the control of materials, to verify that
drawing requirements were met, and to provide permanent records to this
effect.
Quality assurance efforts on the part of Essex began with the
development of a quality assurance manual. A locked material control
area was constructed, and a material inventory control system was
implemented, including numbered tags for all raw materials and purchased
parts as well as stowage of all material certifications and invoices.
As individual wrench parts were fabricated and finished, they were
inspected by the shop supervisor using the Essex-developed inspection
report. All approved parts were cleaned and placed in a locker for
later retrieval, and all nonconforming parts were bagged with a card
labeled "Rejected" on which a description of the nonconformance was
written.
2.3 ACCEPTANCE TESTING
Following assembly, the three wrenches were tested in the presence
of NASA R&QA personnel, the NASA COR and Essex personnel according to
the Essex EVA Ratchet Wrench Acceptance Test HD-82-01. The acceptance
test included the use of all functional parts and a proof load test of
65 ibs/ft which is approximately 150% of the maximum load expected to be
encountered by the wrench. Steps in the acceptance test were repeated
at least four times.
2.4 CLEANING PROCEDURES
Following assembly, the three wrenches were cleaned in MSFC
Building 4705 clean room in accordance with SN-C-0005, VC Level i. The
units were then double bag sealed with appropriate identification sealed
between the inner and outer bags.
ESSIBX
2.5 PACKING AND SHIPPING
The three bagged wrenches were placed in plywood shipping
containers with custom molded foam packing. The containers were then
sealed and labeled for shipment to JSC.
Also packed for shipment to JSC was a data pack including six sets
of engineering drawings, material certifications, inspection reports,
test reports, blank test sheets (for JSC testing), and a Deviation
Approval Request sheet.
As the wrenches and data pack were shipped to JSC, DD 250 forms
were distributed at NASA/MSFC.
2.6 DESIGN MODIFICATIONS AND DRAWING DEVIATIONS
Following delivery of prototype ratchet S/N 1004 to JSC, several
design modifications were decided upon by Essex and agreed to by NASA.
The most prominent of these changes included:
o Replacement of the pawl detent ball with a plunger--to tension
direction pawl with less chance of binding
o Addition of bronze bushing to direction pawl shaft--to
provide a more free running surface in wrench head
o Addition of shoulder on push button--to prevent excessive play
in push button
o Elimination of sleeve to retain quick release ball--to allow
easier disassembly and reduce chance of accidental dislodging.
All design changes implemented are reflected on released engineering
drawings.
A few deviations in the delivered wrenches were not reflected on
the released set of drawings. These deviations are described below.
o Two helicoil inserts and two set screws on each wrench were
too long as delivered by the manufacturer. Therefore they
were shortened enough to allow positioning flush with wrench
outer surface.
o One dimension on the palm wheel called out as .700" ± .004"
actually measured .715" which is .011" out of tolerance.
This deviation was approved for use on the non-flight
(S/N 1007) wrench only. The deviations mentioned above
were approved by the proper NASA authorities and are reflected
in detail on the Deviation Approval Request sheet included in
the data pack.
4 3
ESSEX>>
3.0 SUMMARY
In fulfillment of this contract, Essex has produced and delivered
to JSC via MSFC:
Two flight qualified EVA ratchet wrenches (S/N's 1005 & 1006)
One flight-like prototype (S/N 1007)
Data pack including:
six sets of engineering drawings
material certifications
inspection reports
test reports
three blank test sheets (for JSC testing)
deviation approval request sheet.
Delivery of the contract end items listed above was made on
June 25, 1982 rather than the June 15 delivery date called for in the
contract. The I0 day overrun was acceptable to the C0R and other NASA
officials due to the unusually short contract time alloted and the extra
time required for setup of the quality assurance system.
 IESSEX 
4.0 CONCLUSIONS AND RECOMMENDATIONS
In the production of the flight hardware described in this report,
which is Essex' first flight hardware contract, a few noteworthy
observations were made as are described below. In the purchase of raw
materials and manufactured parts which must be stored in a controlled
area with inventory records and test reports, it was found that
over-purchase was the best policy. In purchasing more materials than
are needed for the job, it is possible to remake nonconforming parts or
remake parts due to design changes without the extra paperwork involved
with purchasing additional certified materials. Similarly, in
fabricating more parts than are actually needed for a job, the chance of
a bottleneck in assembly caused by nonconforming parts is reduced.
In the fulfillment of contract requirements, Essex has developed
the capability for the production of flight hardware, particularly small
equipment such as the EVA ratchet wrench. With knowledge gained from
flight hardware production, an in-house quality assurance capability,
and an on-hand inventory of certified materials and parts, Essex is now
capable of producing EVA ratchet wrenches with streamlined efficiency.


Fabrication of Essex EVA ratchet wrenches

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