Status Report

Minutes for July 18, 2000 EVA AIT

By SpaceRef Editor
July 18, 2000
Filed under

To: Distribution


From: XA/Nancy J. Patrick


Subject: Minutes for July 18, 2000 EVA AIT

The EVA AIT met at the Johnson Space Center on July 18, 2000. Boeing/Lou Ramon and XA/Nancy Patrick co-chaired the meeting. Representatives from CB/Flight Crew Operations, XA/EVA Project Office, NC/Flight Systems Safety and Mission Assurance, DX32/EVA Systems/Mission Operations, OM/ISS Mission Integration, OB/ISS Vehicle Office and Boeing-Houston (EVA and Safety) were present. Representatives from the Kennedy Space Center, Marshall Space Flight Center and Boeing Development Centers supported by telecon. Copies of presentations can be obtained from XA/Charlotte Shannon, Building 1, room 661, (281) 483-5259.

1. Introduction/AI Review Boeing/Lou Ramon


XA/Nancy Patrick

The Following Decision Package was distributed via Email, after the EVA AIT for review August 1:


PG3-AL-01-2000: Airlock Anthropometric Requirements



The Following Decision Packages were dispositioned (distributed June 27, 2000 and/or later, via Email):


PG1-P3/S3-EV&CS-27-06: Keep Out Zone & Warning Label location


Decision: The EVA AIT Approved this PIDS exception



PG1-P3/S3-EV&CS-27-07: Keep Out Zone & Warning Label Location


Decision: The EVA AIT Approved this PIDS exception



MD Robotics NC 50021920: MBS Assembly handrail interference


Decision: The EVA AIT Approved this non-compliance



ESA-Cup002: EVA Induced Loads on MCF and Round Scoop Tools


Decision: The EVA AIT approved this PIDS exception. The EVA AIT confirmed that the use of a microconical and round scoop can be used as a stabilization aid (its within the tool’s capabilities and is a legitimate method for handling on robust components). The EVA AIT noted, however that if the particular worksite and surrounding hardware does not meet EVA kick load requirements, EVA handholds are required to provide adequate stabilization to avoid damage to the hardware. For this particular hardware, ESA is tracking an open issue with the Cupola shutter mechanism not being able to withstand kick loads. If that is not resolved by ensuring the hardware meets kick load requirements, EVA handholds will be required.

The Following Decision Packages were deferred from the EVA AIT pending MOD approval, and later approved via Email concurrence on July 25, 2000


PG2-P6-2000-1: EVA Gloved Hand Clearance Requirement for P6 QDs


Decision: The EVA AIT Approved this PIDS exception

PG2-P6-2000-2: EVA Kick Load Requirement for WIS Antenna


Decision: The EVA AIT Approved this PIDS exception



The Following Decision Packages were deferred pending additional information


ESA-Cup001: Clearance around EVA Bolts (distributed as tracking number ESA-001)


Open Work: XA/Heather Mitchell will confirm with engineering that the clearances provided will accommodate the necessary tools. The EVA AIT will address this PIDS Exception on August 1.

PG1-S0-EV&CS-27-05: S0 EVA Label operational name character height for Luminaire ORUs


Open Work: PG1/Phil Peterson explain whether the font size indicated in the exception is the largest that it can be and why. This PIDS exception will be addressed again on August 1



PG1-S1/P1-EV&CS-15-16: Shroud Launch Lock Tasks


PG1-P1/S1-EV&CS-15-17: Shroud NTA Tasks


Open Work: Subject of the PIDS Exceptions will be evaluated in an NBL test scheduled for August. PG1 will resubmit the PIDS exceptions in early September pending the NBL test outcome.



NCR-ISS-052: USL Touch Temperature Exceedences, Incidental Contact


Open Work: The MMOD shields along the Lab primary translation path come very close to the absolute EMU limit of 320°
F for some beta angles above 60°
, assuming end of life properties. At temperatures above this limit, suit damage occurs with inadvertent bump or brush loads. The EVA community was not comfortable accepting the non-compliance without operational controls in place and suggested that when the ISS is above 60°
beta, a specific task thermal analysis should be performed to ensure that the temperatures are within the suit limits. Boeing Thermal is considering this option and will report back to the EVA AIT with a modified NCR. See minutes below for additional information.

The Following Action Items were reviewed:


AI-343: This action remains open and will be addressed again on August 15, after the FLAP Acceptance Review, which is currently scheduled for July 25.


AI-400: This action remains open and will be addressed again on August 15. Mr. Brady did not report on the program response to PG3’s position that level 2 ARs are not required, and Mr. Ramon did not have any new information on whether PG3 provides any hardware for which EVA is concerned.


AI-494: This action remains open and will be addressed again on August 1. Mr. Ramon thought that Huntington Beach and Canoga Park had provided inputs but is checking.


AI-507: This action remains open and will be addressed again on September 24. A stowage splinter discussion was held on July 12 and several other issues have to be addressed before this action can be answered.


AI-512: This action was deferred to August 1 prior to the EVA AIT due to time constraints


AI-513: This action was deferred to August 1 prior to the EVA AIT due to time constraints


AI-514: This action remains open and will be addressed again on August 1. Mr. Ramon is still compiling inputs from the PGs.


AI-515: This action remains open and will be addressed on August 1. Mr. Looper reported that some fit checks of the bale drive tools have been complete on P6 and the Lab.


AI-517: This action was CLOSED. PG1/Richard Gonzalez reported the following with respect to use of Loctite on Huntington Beach EVA bolts:


  1. Loctite is only used on 6B box bolts

  2. Specification is for low-torque Loctite (max is 180 in-lbs, typically comes in around 125 in-lbs or less)

  3. Current acceptance testing plans break the torque on each flight bolt after installation and application of Loctite, however the Loctite is not cured at the time of the test. The purpose of this test is not to verify the break torque for the initial launched bolt, but to verify the break torque at that interface for a replacement or re-installation of that bolt after the initial bolt has been already been broken (i.e. the second 6B box replacement in that location).

  4. Huntington Beach has some plans to test cured Loctite on 6B box bolts to determine effects of residual Loctite upon re-installation of a bolt, and to address the breakaway torque concern. The test plans are not finalized and there is not a definite decision about conducting the tests.

The EVA AIT concluded that testing a representative set of 6B bolts with cured Loctite was sufficient to conclude that the practice is acceptable, and that breaking torque on each flight bolt after the Loctite is cured is not required. The EVA AIT had the following concerns with the current test program and recommendations for the proposed testing:


  1. Verification of each flight bolt break torque with uncured (wet) Loctite is not sufficient to determine the required break torque, since Loctite can actually act as a lubricant. This test may be valuable for other reasons, but PG1 should provide additional verification of the secondary break torque.

  2. For the proposed new tests, the full range of combinations for bolt types, sizes, inserts and installation torques should be tested to ensure break torque for each case. Verification can be by similarity to these tests if all the combinations are addressed in testing.

  3. It appears that contamination from the Loctite would be of concern when the initial bolt is broken. This is not an EVA concern but it’s likely that it’s an ISS concern.

The EVA AIT requested that we be informed of the Struc and Mech actions to address the above concerns. The following action was assigned:

Action 522: Report on the ISS program plans to resolve questions with the use of Loctite on EVA bolts. Include test plans and proposed completion dates.


Actionee: OB/John Zipay


Due Date: August 1, 2000


Method for Closure: Report to EVA AIT

Ms. Patrick spoke with Mr. Zipay after the EVA AIT. He agreed to the action and agreed with the concerns and general direction for addressing those concerns as proposed by Huntington Beach.

AI-518: This action was CLOSED. Ms. Patrick reported that the subject meeting was held on July 12, with several actions resulting. The group intends to meet again in mid-August, and Ms. Patrick will keep the EVA AIT appraised of the progress.


AI-519: This action was CLOSED. Mr. Looper provided the assessment. See minutes below for additional information


AI-520: This action was CLOSED. Mr. Carlton provided the requested information. See minutes below for additional information.



2. Lab MMOD Shield Touch temperature NCR XA/M. Tullar, N. Patrick


Follow-up (NCR-ISS-052) B-Hou/M. Nicholls, L. Ramon


DX32/T. Gonzalez


Follow up to 6/27 EVA AIT discussion and 7/5 EVA AIT splinter.


XA summarize splinter meeting results and actions, including EMU capabilities and constraints. B-Hou/TCS to summarize Lab MMOD shield thermal exceedances, indicating under what conditions specific shields exceed the touch temperature requirements. Specifically indicate if the primary lab translation path exceeds 320°
F, and if so, at which stage/configuration and under what conditions (Beta angle/attitude). B-Hou/EVA indicate which tasks are in the vicinity of any shields which exceed 320°
F, and any known time criticalities associated with those tasks. DX32 to report on whether 3 minutes continuous grasp time (EMU glove limit for handling at 320°
F) is acceptable for MMOD shield operations (e.g. shield replacement).



Ms. Tullar summarized the results of the July 5 EVA AIT splinter meeting addressing this issue. Ms. Tullar reported that the absolute EMU limit is 320°
F, based on testing. As long as the EMU is never exposed to temperatures above 320°
F, it will remain in tact. At temperatures above this, TMG begins to fuse. After this initial degradation occurs the TMG cannot withstand temperatures even below 320°
F (temperature at which further degradation occurs depends on the extent of the initial degradation) without further degradation. This continues until a catastrophic failure of the EMU. It is likely that this would occur before any outward signs of the degradation are present, and before the crewmember feels excessive heat. Therefore exposing the suit to temperatures above 320°
F is unacceptable. Mr. Nichols reported that the initial temperature analysis determined that the Lab shields exceed 320°
F under the following conditions:


  1. In XVV attitude

  2. For Beta angles above 60°
    F

  3. With shield end of life properties

  4. After stage 8A configuration (due to the addition of trays and hardware around the lab which help preclude radiative cooling)

Mr. Nicholls explained that the End of Life properties are determined by the sun exposure (and other factors, but sun exposure is the biggest contributing variable from one shield to the next). The simplified analysis identifies the shield with the worst sun exposure on the lab shield and determines the EOL properties based on that shield’s sun exposure. In this case, a shield away from the translation path, toward the zenith, has the worst-case sun exposure and therefore the worst-case EOL properties. Those EOL properties are then used for all the shields’ thermal analyses. The shields that experience the highest environment temperatures are next to the translation path, and are different than the shields with the worst-case EOL thermal properties. The combination of the worst-case environment temperature and worst-case EOL properties result in temperatures that exceed 320°
F. The thermal team repeated their analysis with the EOL properties developed for the shields in question, based on their sun exposure, and the new predictions are a peak temperature of 314°
F at the end of the ISS life, for betas above 60°
.

The EVA AIT was not comfortable accepting the temperatures without operational controls, since the predictions are so close to the absolute suit limits, and since it is possible that ISS will continue to be manned long after the lifetime design requirements. The EVA AIT suggested that an operational control/flight rule be included in the hazard report/NCR which requires a task specific thermal analysis at the time an EVA is required on the lab, to ensure that the temperatures are within suit limits, if the beta angle is over 60°
. Mr. Nicholls agreed to propose this to the Lab thermal team and provide the EVA AIT with an updated NCR, if accepted. The EVA AIT agreed that the hardware is acceptable if this operational control is in place.

One additional question was raised at the splinter concerning handling of the MMOD shields themselves, at these high temperatures. The concern was whether the crew could perform an MMOD shield change out if the temperatures approached 320°
F. DX32/Tomas Gonzalez reported that the task does not require direct handling of the MMOD shields (they are handled by the T-handle attached to the fasteners), therefore handling of the shield is acceptable (assuming the temperatures are within the EMU limits per above).



Decision: The EVA AIT concluded that the Lab MMOD shields are acceptable if the ISS community accepts operations controls to perform task specific thermal analysis when ISS is above 60°
beta

3. MT/CETA Rail Deletion Follow-up Assessment B-Hou/C. Carlton


(SSCN 3730) DX32/C. Looper


Mr. Carlton information on the expected maintenance actions per year for the PV module ORUs. He also provided the location of the ORUs, size and robotic capabilities, if any. For each PV module, they expect on average, approximately 5 maintenance actions per year. The maintenance action takes into account various factors including failure rates, wear out life and other factors. Based on the number for each type of ORU, the EVA AIT concluded we can expect to perform change out of one large, EVA supported ORU per year (total for all four PV modules). The ORUs that rely most on EVA support are the blanket boxes, cable boxes, and BMRRM. Most of the other ORUs require either only EVA connections or are entirely robotically compatible.

Mr. Looper reviewed his study findings. He assessed two EVA ORU change outs on P6, one for a robotically compatible ORU (Battery) (assumes a failure of the robotic system) and one for an ORU that requires EVA support (BMRRM). For each of the assessments, he compared the case with the outboard MT/CETA rails in place and one without the rails. For the first ORU (robotically compatible), he assumed no robotic support, for the second (EVA support required) he assumed a fully functional robot. For all of the assessments, his comparison started with the crew and EVA hardware at the end of P3, with the ORU on the CETA cart. Since this is the point in the overall scenario at which the presence of the outboard rails starts to make a difference, the EVA AIT concurred with this approach.

Based on Mr. Looper’s presentation, the scenario without the rails for a normally robotically compatible ORU change out is significantly longer than with the rails in place (9 hours vs. 2 hours 40 minutes). This assumes no robotic support to the task since if the robotic system is available, this would normally be performed entirely by the robotic system. This time increase is due to the requirement to transport the ORU from P3 to P6 and the only method to do that would be with Crane-to-Crane handoffs. This scenario would be the baseline scenario once P6 is relocated and until the rails are normally installed (approximately a 2 year period).

For the scenario addressing installation of a normally EVA installed ORU, the task times are not significantly different with or without the rails (2 hours vs. 2 hours 35 minutes). This assumes the PDGF and full support of the robotic system since that would be the normal operational mode.

The EVA AIT concluded that there is no "smoking gun" that says we are the operations concepts are not viable without the MT/CETA rails, assuming a PDGF is provided. However, the EVA AIT is concerned that the program would be taking the following risks by deleting the rails at this time:


  1. Counting on the robotic system to operate with the full capability advertised today, with no on-orbit operational experience

  2. Counting on the robotic system being fully functional at all times (including MT, MBS, SPDM and all supporting systems and hardware) or there are sufficient spares to repair any failures

  3. Counting on the end to end maintenance scenarios providing the maximum EVA flexibility for moving spares from the stowed location to the ORU worksite

  4. Counting on the technical challenges of the proposed PDGF will all be overcome without any reduced functionality

  5. Counting on the PV/EPS components not failing at a greater rate than expected

  6. Counting on having sufficient on-orbit spares to maintain all the components

Decision: The EVA AIT concluded that while adding PDGFs is a benefit to EVA before the rails are installed, the rails should not be deleted at this time. The EVA AIT recommended the program continue with rail development until more on-orbit experience is available, and until the technical challenges of the addition of PDGFs are resolved. This recommendation was then presented to the EVA CCB on July 21.

Action Item Closure: AI-519, 520 were closed



4. FRAM/EVA Tools Interface Issues LMES/B. Wilkes PG3/S. Burks


Mr. Wilkes described the RIDS written at the FRAM CDR concerning the integrated FRAM/ORU and its compatibility with the EVA tools (TERA, CETA cart and Crane). Due to the off-set of the square grid on the FRAM, for at least some ORUs stored on the FRAM, the CG is off-set so much that the system cannot withstand kick-loads at the end of the FRAM/ORU, or CETA braking loads. The failure mode depends on the specifics of the unique combination, however at least some subset of ORUs will have this problem. There is another issue with access to the ORU while it is mounted on the FRAM/EVA tool, since the square grid offset can put the ORU out of reach.

One possible solution is to include a load limiter in the system. Mr. Burks noted that this is not possible on the FRAM because it precludes robotic compatibility, which FRAM is also required to provide. Other solutions. Another option is limiting the size or the ORU and/or its location on the FRAM if the ORU is supposed to be EVA compatible. Finally, identifying keep-out zones for combinations that exceed the kick-load requirements could alleviate the concern.

Unfortunately the EVA AIT did not have time to address the pros and cons of the various options and will address them in a splinter discussion. XA/Greg LeStourgeon agreed to set up the splinter discussion. At that time, EC/Lora Laurence will provide a matrix of the ORUs that had been identified as EVA compatible previously, and how those fit given the current constraints. The approach will be to identify how badly the system is broken and identify the recommended fixes based on what specifically is broken.

Action 523: Schedule a splinter discussion assessing the EVA transport and handling of ORUs using the FRAM.


Actionee: XA/Greg LeStourgeon


Due Date: August 15, 2000


Method for Closure: Report to EVA AIT



5. Upcoming Events/Future Agenda Review XA/Nancy Patrick, All


Ms. Patrick reviewed the preliminary EVA AIT agenda for August 1, 2000. Presenters are requested to confirm agenda topics by COB Thursday, July 27, 2000. Ms. Patrick noted that the EVA Standard ICD discussion would be added to the August 1 agenda since there wasn’t time to discuss it. Ms. Patrick also offered $100 to anyone who could report good news on EVA items. There were no takers.

The Following topic was deferred until August 1 due to time constraints


EVA standard ICD status follow-up discussion LMES/S. Rogge,














EC5/L. Laurence, XA/Dale Roberts, N. Patrick














PG1, PG2, PG3, B-Hou,


Review status of all open ICD PIRNs discussed at 6/27 EVA AIT. Specifically, discuss the following PIRNs and open issues:


61C: N. Patrick — Report status of signature, forward to OB


65A: PG1, XA — Report status of SSCN 3731- required to resolve this PIRN (also tied to withdrawal of PIRN 68)


67: EC5, LMES — Report status of modification to make it a non-impact PIRN


70: LMES, PG2 — Report status of PIRN revision and/or non-concurrence withdrawal from PG2


71: LMES — Report results of attempts to document existing MT/CETA stop interface capabilities without impact PG1.


All — report on any new requirements for PIRNs recently submitted or being considered for submittal which are not part of this list (i.e. PIRN 72 and beyond)


Decision Required: EVA AIT concurrence on PIRN resolution plans


Required Attendees: XA, Boeing-Houston, DX32, CB, NC, EC5, KSC/SSHIO, PGs, SLP, MSFC, CSA, ESA, NASDA


SpaceRef staff editor.