**Lesson Info**

-   **Lesson Number:** FPPD-LL-0005

-   **Lesson Date:** 26-jul-2000

-   **Submitting Organization:** Swales Aerospace, Inc. (GSFC 491)

-   **Submitted by:** Michael J. Cully

**Subject/Title/Topic(s):**

EO-1 Solar Array Cable Wrap Damage Problem Report 1045-40-1

**Description of Driving Event:**

Final inspections of EO-1 Spacecraft prior to T/V#2 revealed a hair line
mark on the Solar Array Cable Wrap Bundle. Further inspection at 10-20X
magnification indicated cut insulation of seven wires approximately 0.75
inches off the face of panel 5. Geometry of the cut (alignment,
cleanliness, etc.) indicated damage due to a sharp object.

Corrective Action was as follows:

1)  Made use of current internal Bay 5 SADA cabling interface connection
    and spare wires.

2)  Fabricated "Connector Bracket Assembly" which essentially swapped
    wires (J2-7, J2-37, J2-19 & J2-27) with the spares. Parts were
    simple & made use of the existing bolt & hole pattern for brackets.

3)  Milliohm & insulation resistance (cross pin) testing conducted on
    entire cable to verify all wires prior to initiation of the change &
    rework of damaged cables.

4)  Although J 2-7, J2-37, J2-19, & J2-27 wires were being abandoned,
    the exposed copper & insulation wiring needed to be covered. Guard
    wires also needed to be reworked.

5)  All work was performed to Certification Logs, Work Order
    Authorizations (WOAs), & released drawings.

6)  Milliohm & HiPot tested entire cable following rework. (Connector
    Bracket Assembly testing which also included HiPot testing was
    performed prior to delivery to Spacecraft).

7)  Integrated Connector Bracket Assembly with Cable Wrap Assembly.

8)  Verified all SADA signals after the Connector Bracket Assembly was
    installed.

9)  Performed full SADA functional following rework.

10) Performed S/C Aliveness Test following completion of S/C bay
    closure.

Other Global actions were as follows:

1)  Inspected all external cabling prior to blanket installation.

2)  Fabricated Red Tag Item to cover critical area of Solar Array cable.
    To be removed prior to Solar Array installation.

3)  Verified Mechanical Margins of Safety for new bracket and inserts
    (no test factors).

4)  Determined that the Deployment Hinge has \>4x torque margin for
    worst case environmental effects.

**Lesson(s) Learned:**

Further investigation of probable cause is as follows:

1)  It is believed that this damage occurred while in the 238 T/V
    chamber in the preparation of the Spacecraft for T/V (October '99)
    or while clearing out the GSE blankets in and around the SADA . This
    cannot be verified and it is more than likely an accident which went
    unnoticed. The SADA and cable wrap were thoroughly inspected via
    bore scope shortly before T/V and was found to be nominal.

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a)  Prior to T/V #1, a thorough inspection was performed in this area
    without issue.

b)  No work has been done in this area since leaving T/V, until
    recently.

c)  Cutting instruments are generally used in chamber operations (TC
    number cutting, GSE MLI clearing, etc.).

d)  One T/V GSE cable was found damaged in similar manner following T/V.

e)  Configuration in chamber was not conducive to "ideal working
    conditions for technicians" due to extremely tight configuration and
    poor lighting.

f)  QA oversight was from a distance during T/V buildup and T/V teardown
    due to continuous monitoring of oxygen level at chamber door due to
    concern over nitrogen purge in closed chamber. Safety of personnel
    was first priority! Also there was insufficient room to have two
    people in the same general physical area.

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2)  Other post-T/V activity required use of razor blades (radiator tape
    cutting, excess adhesive removal/trimming, etc.) however this has
    been limited and is under constant monitoring by QA.

**Recommendation(s):**

Recommendations to prevent a similar event are as follows:

1)  Critical external harness (SA Cable Wrap, Deployment Harness, etc.)
    that are vulnerable during the I&T process if possible should be
    protected.

2)  Evaluate the incorporation of amble spare wiring for Solar Array
    Cable Wrap wiring. This will allow quick recovery if damage does
    occur, as in the case of EO-1.

3)  Minimize to the extent possible the use of sharp objects around the
    spacecraft. This is common practice for flight thermal blanket work
    however for ground support blanketing (removal operations) it is not
    standard practice.

4)  Limit the extent of test Thermal Couples and Heaters termination
    work \"in the chamber\" following the test. Typically terminating
    TCs in the chamber is quick versus breaking the connections at the
    chamber bulkhead and coiling up the wiring. However this can
    potentially expose flight hardware to damage if cutting tools are
    mishandled.

5)  GSE fixturing should be inspected for sharp edges that could
    potentially damage GSE cabling. Corrective action would be tapping
    edges as required.

6)  Evaluate lighting and general work conditions in the chamber prior
    to the start of flight hardware work. If required develop ways to
    increase light in the chamber.

7)  Amble time must be provided for chamber operations. Technicians
    involved in chamber operations are working in a very constrained
    environment (limited lighting, space constraints, clean suits, etc.)
    and therefore sufficient time must be alloted to perform their work
    safely.

8)  Route spare cable wrap wires to an access location conducive to
    rework.

**Evidence of Recurrence Control Effectiveness:**

A number of the above recommendations where implemented prior to the
second Thermal Vacuum test on EO-1. The satellite was removed from the
chamber and no issues have arisen to date in this regard.

**Applicable NASA Enterprise(s):**

**Applicable Crosscutting Process(es):**

**Additional Key Phrase(s):**

Facilities

Safety & Mission Assurance

Spacecraft

Test Article

Test Facility

Test & Verification

**Can this lesson be included in the International Safety Lessons
Learned (ISLL) Database?** No

**Submitted by:** Michael J. Cully

**Mail Stop/Code:** Swales Aerospace, Inc.

**Lesson Author (if different):** N/A

**Phone Number:** 301-902-4356

**E-Mail Address:** mcully@swales.com

**Lesson Date:** 07 / 24 / 2000

**Reference:**

EO-1 Test Readiness Review to Code 300 June 23, 2000

Thermal Vacuum #2 -- Solar Array Cable Wrap Damage