1. EVA: Don’t Leave Earth Without It
Presented by J. Scott Cupples and Stephen Smith
NASA, Johnson Space Center
FISO Telecon

2. Introduction
Modern manned space programs come in two categories: those that need Extravehicular Activity (EVA) and those that will need EVA.
EVA was used to save payloads, enhance on-orbit capabilities, and build structures in order to ensure success of National Aeronautics and Space Administration (NASA) missions
The Extravehicular Mobility Unit’s (EMU) design, and hence, its capabilities evolved, as its mission evolved
Lessons can be drawn from these case studies so that EVA compatibility is designed into future vehicles and payloads.
Cupples
Five categories of EVA
Satellite Repair/Rescue
HST
ISS construction
Vehicle Repair and Maintenance
EVA Development
First four will be discussed, EVA hardware development could be the subject of a different talk

3. Satellite Repair & Rescue Planned satellite capture with Manned Maneuverability Unit (MMU)
STS-41C MMU rendezvous with Solar Max
Smith
At advent of Shuttle Program, only one EVA mission existed: closing PLB doors
Shuttle managers recognized utility of having an expanded EVA capability
Between 1983 and 1997, thirteen EVAs over eight missions to repair and rescue satellites
STS-41C in 1984 was first attempted satellite capture EVA
Capture failed due to an interfering grommet on satellite that was not reflected in drawings
Instead, Solar Max was berthed in PLB via RMS and the EVA crew repaired the satellite
It was relaunched from PLB and was operational again within a month
The next satellite repair mission was STS-51A in November 1985, which used the MMU to retrieve two satellites, Westar and Palapa.
Those satellites were brought back to Discovery and returned to Earth.
After the mission, the satellites were refurbished and relaunched.
STS-41C Training with MMU at the Weightless Environmental Training Facility (WETF)
STS-51A MMU Capture of Palapa B-2 Satellite

4. Satellite Repair & Rescue First Un-scheduled EVA from Shuttle
Flyswatter affixed during EVA to RMS with help of Payload Retention Device (PRD)
STS-51A MMU Capture of Palapa B-2 Satellite
STS-51A MMU Capture of Palapa B-2 Satellite
STS-51A MMU Capture of Palapa B-2 Satellite
STS-51A MMU Capture of Palapa B-2 Satellite
Satellite Repair & Rescue First Un-scheduled EVA from Shuttle
Flyswatter affixed during EVA to RMS with help of Payload Retention Device
STS-51D WETF Evaluation of Flyswatter installation on Shuttle Robotic Manipulator System (RMS)
Smith
LEASAT-3 was launched from the PLB on STS-51D in April 1985
Its kick motor failed to ignite
Engineers and technicians on the ground worked to build a tool which could allow the RMS to activate the kick motor switch
The crew performed the first unscheduled EVA to install ‘flyswatter’ paddles on the end of the RMS
The paddles worked, but the kick motor didn’t
Flyswatter in position to engage Sequencer Start Lever on LEASAT-3

5. Satellite Repair & Rescue Human Grappling/Capture of Satellites – External Loads into Suit
STS-49 Three-crewmember EVA grapple of Intelsat
Cupples
In August of 1985, the crew of STS-51-I retrieved the satellite, repaired it, and redeployed it
STS-49 in 1992 featured the first – and only – three-person EVA.
The two-person EVA crew spent the first two EVAs trying to mate a capture bar to Intelsat, but it was not possible
Three person EVA was conducted on EVA three to enable the crew to manually grapple Intelsat and mate it to its perigee kick motor
As a result of the experience of these EVAs, engineers recognized upgrades that could be incorporated to improve the EMU
Redesigned HUT
Improved axial restraint system in arms, waist, legs, boots
Dual seal bearings
3000 series gloves
Improved flexibility
Improved palm material for enhanced tactility
Very robust glove
4000 series gloves
Eliminated excess bladder material
Eliminated pressure points
Early STS EVAs gave NASA valuable experience working with large space structures
Allowed NASA to refine the EMU design and tools based on real-world use
These lessons were carried forward
STS-51I Syncom IV EVA Capture

6. Hubble Servicing Missions Realization of intricate on-orbit EVA Capabilities
STS-61 WETF training for Wide-Field Planetary Camera (WFPC) removal/installation
Smith
HST one of the first truly EVA-compatible satellites
23 EVAs were conducted over the span of five Shuttle missions from 1993 to 2009
The HST missions are the best example of EVA repairing a malfunctioning satellite
HST launched in 1990, and astronomers immediately noticed a problem called spherical aberration due to mirror being ground incorrectly
STS-61/SM 1 (1993)
Five EVAs conducted to install the Corrective Optics Space Telescope Axial Replacement (COSTAR) to correct spherical aberration
Upgraded gyroscopes, solar arrays
Original solar arrays shuddered every time HST transitioned from day/night or night/day
After gyro install, crew had difficulty closing latches on doors – engineers and ground controllers devised a solution and overcame problem
STS-61 was complete success and allowed HST to return imagery designers intended
Five EVAs in one mission is record that has been matched but not surpassed
STS-61 On-orbit removal and temporary stowage of WFPC

7. Hubble Servicing Missions HST enhancements and increased capability
Smith
STS-82/SM 2 (1997)
Five EVAs
Swapped two spectrograph instruments for Near Infrared Camera and Multi Object Spectrometer (NICMOS) and Space Telescope Imaging Spectrograph
Both instruments included correction factor for flawed optics
Repaired thermal insulation
STS-61 COSTAR installation
STS-82 NICMOS preparation for installation

8. Hubble Servicing Missions
Smith
STS-103/SM 3A (1999)
Three EVAs
Replaced all six gyroscopes after a subset began to fail
Upgraded computer to a unit that was 20x faster and had 6x more memory
Installed battery protection kit to prevent overheating and overcharging
Replaced failed S-band transmitter, allowing HST to communicate w TDRSS
Installed spare solid state data recorder, replacing original reel-to-reel unit (and increased storage from 1.2 GB to 12 GB
Upgraded fine guidance sensor
Lubricated door hinges and repaired degraded thermal insulation
STS-82 Manipulator Foot Restraint (MFR) and tool preparation for EVA
STS-103 Use of Pistol Grip Tool (PGT) to secure bolted fastener on HST Flight Support Equipment

9. Hubble Servicing Missions
STS-109 Solar Array preparation for FSE removal and HST installation
Cupples
STS-109/SM 3B (2002)
Five EVAs
Upgraded solar arrays
Installed new Power Control Unit which is compatible with solar arrays
Replaced Faint Object Camera with Advanced Camera for Surveys
Removal of FOC and install of ACS eliminated need for COSTAR
Installed cryocooler for NICMOS
STS-125/SM 4 (2009)
Removed COSTAR
Installed Cosmic Origins Spectrograph
Installed Wide Field Camera 3
Repaired ACS and STIS
Upgraded thermal insulation
Installed soft-dock mechanism to allow deorbit motor to mate with HST
In each HST mission, EVA crew repaired, replaced or upgraded systems to improve HST’s condition
Improvised workarounds and adaptively solved problems real-time during spacewalks
The real-time adaptability is often overlooked when trading EVA capability against robotic capability
HST EVAs also demonstrated astronauts were capable of performing complicated assembly and maintenance tasks during EVAs, helping to pave the way for ISS construction
STS-109 HST Connector Tool is ready to assist with connector removal/installation

10. ISS Assembly Pre-ISS Shuttle Missions to Validate Hardware and Capabilities
STS-61B ACCESS/EASE demonstration of EVA Construction Capabilities and Techniques
Smith
Developmental EVAs in early years of Shuttle experimented with construction techniques (STS-61B with EASE/ACCESS and STS-49 with ASEM) and translation concepts (STS-37 with CETA)
And test concepts that could be used later.
STS-37 Evaluation of Crew and Equipment Translation Aids (CETA)

11. ISS Assembly
STS-64L Detailed Test Objective (DTO) evaluating EVA SAFER
Smith
In early 1990s, as ISS assembly was being planned, it became clear that a large number of EVAs were going to be required to complete the task
Large number of EVAs was called ‘The Wall of EVAs’
98 EVAs were conducted during Shuttle missions out of both STS and ISS airlocks to assemble
650 hours of spacewalks
25 of first 26 assembly EVAs were conducted out of Shuttle airlock
After Quest Joint Airlock was installed on STS-104/7A, EVAs originated from ISS
Shuttle was still vital to the success of EVA, though, because Shuttle provided the EMUs for the ISS EVAs
Preserved EMUs on ISS, which have a limit on the number of times they can be used prior to servicing
STS-64 conducted DTO on MMU replacement called SAFER
Implemented SAFER, because Orbiter could not undock to rescue separated crewmember
SAFER uses hand controller to ‘fly’ N2 propelled jetpack and gyroscopic sensors to maintain attitude control
ISS construction began with STS-88 with power and avionics cables being connected from PMA1 to FGB
STS-88 View from Mid-deck as avionics connections are completed between PMA1 and Node1

12. ISS Assembly
STS-113 EVA Crew completes assembly tasks for ISS Truss Segment P1
Cupples
In preparation for all the EVAs, EMU went through a major upgrade program called EMU Enhancements
Goals:
Provide on-orbit logistical options to minimize amount of EMU hardware launched
Can’t send an entire closet of suit parts to orbit
Need to optimize components to allow them to fit widest range of sizes possible
Reduce time to resize suit
Baseline EMU required about three hours for pair of arms or legs
Required lacing cord and needle
Enhanced design involves screw on arms, legs, sizing rings
Cams on axial restraints allow for smaller adjustments
Resize of a suit could be accomplished in as little as 15 minutes
STS-123 Linnehan pauses from SPDM Robotic Arm assembly to take a photo of the Space Shuttle

13. ISS Assembly
Assembly Complete: STS-134 docked to ISS as seen from Soyuz 25S departure
Cupples
Other changes added On-Orbit-Replaceable features to major components of the EMU
HUT
PLSS
SOP
DCM
Arms
Allowed all components to be changed out on orbit with a minimum of tools
Haven’t used capability on orbit as of yet, but efficiencies were realized in ground processing
Prior to enhancements, only CCC and Batt could be changed by crew
Maintenance
Original EMU maintenance interval was seven EVAs conducted over a two-week period
Not practical to fly new suits to orbit every two weeks
Extended to 25 EVAs conducted over six months
The Space Shuttle and EVA were integral components in the construction of ISS
The Shuttle brought the largest elements to Low Earth Orbit and a combination of robotics and EVA successfully mated these elements and their associated fluid lines and power and data cables
The Shuttle Program and EVA successfully demonstrated that large, complex space structures could be built in space.

14. Vehicle Repair & Maintenance Mir Spectr Module attempted leak repair after collision from Progress
STS-86 Space Station Mir and docked Shuttle seen reflected in self-portrait photo
Smith
At various times throughout the Shuttle Program, EVA has been called upon to perform maintenance tasks or restore a function of a vehicle
In a few cases, EVAs were performed to ensure survivability of a manned vehicle
STS-86/Mir (1997)
Following the collision of a Progress resupply module with Mir, astronauts attempted to seal a leak in the Spektr module
Ultimately, attempted repair failed and Spektr remained unpressurized for remainder of Mir project
STS-86 Damaged Mir Spectr module in which sealing cap was installed during EVA, but did not correct leak.

15. Vehicle Repair & Maintenance ISS Mechanisms not designed (or anticipated) to need EVA Repair
Smith
STS-97 (2000)
EVA crew inspected and repaired ISS solar array tensioning mechanism which failed during deployment
Crew adapted EVA Contingency Tools from Shuttle to effect repairs, as no suitable tools were available on ISS
This repair exemplifies the value of having an adaptable EVA capability on orbit
This was a task that no one envisioned, and employed tools and techniques no one knew in advance to develop
STS-97 Re-positioning of tensioning wire onto pulley of P6 Solar Array Wing (SAW) Blanket Box

16. Vehicle Repair & Maintenance Shuttle Thermal Protections System (TPS) Repair
STS-114 Robinson on SSRMS (out of view) moving to protruding Gap Filler location
STS-117 EVA Repair of OMS Pod Blanket separation (before and after).
STS-114 EVA Gloved-hand removal of Gap Filler between heat shield tiles
Cupples
Following the Columbia Tragedy, NASA aggressively pursued an EVA capability to assess and repair damage to the Orbiter Thermal Protection System (TPS), including
the Reinforced Carbon-Carbon (RCC) leading edge sections on the wings
the thermal tile heat shields
blanket sections.
EVA repair capability of the TPS and RCC was critical to NASA’s Return To Flight effort.
Without the assurance that EVA repair was possible, the Shuttle might not have flown again.
The Space Shuttle TPS was inspected and repaired on two separate missions
STS-114 (2005)
Protruding gap fillers on Orbiter forward belly
STS-117 (2007)
EVA repair of torn and peeled blanket on OMS pod

17. Vehicle Repair & Maintenance Un-scheduled EVA Task to provide strain relief to ripped Solar Array
STS-120 Parazynski on OBSS maneuvered to position to repair torn Solar Array Blanket with improvised Cuff-links
Smith
STS-120 (2007)
EVA crewmembers inspected, repaired and supported the redeployment of the ISS solar array.
STS-120 Cuff-links installed prior to Solar Array tensioning

18. Vehicle Repair & Maintenance Functional Recovery of Damaged Solar Alpha Rotary Joint (SARJ)
Smith
STS-126 (2008)
Maintenance work was performed on the ISS power generation system when the EVA crew spent four EVAs to clean debris, lubricate the solar array race ring and replace the trundle bearing of the ISS Solar Array Rotary Joints.
STS-126 EVA Crew prepares SARJ for application of lubrication on race-ring bearing surfaces

19. Conclusions EVA was not originally part of the Space Shuttle Program.
Once EVA was adopted as a core capability of the Shuttle, its true potential as an asset to NASA was realized.
EVA holds significant, unique advantages over other methods of working in the space environment.
EVA crewmembers can provide real-time feedback on worksite conditions and problems being encountered.
EVA crewmembers have provided solutions to problems such as stuck bolts and jammed hinges that would have otherwise been impossible for robots to solve.
EVA crewmembers have improvised real-time procedures and adapted tools while on-orbit.
One important legacy of the Shuttle Program is that EVA was successfully employed to achieve national, program and mission goals. Managers, engineers and designers of future spacecraft systems would do well to remember this EVA legacy.
Cupples
However, managers soon saw the value of an EVA capability for some contingency scenarios such as shutting Payload Bay doors and closing External Tank doors.
Of the 166 US EVAs performed during the Shuttle Program, 144 of them were dedicated to inspecting, retrieving, maintaining, repairing or rescuing a spacecraft in some manner or other.
Improvised procedures and tools real-time to deploy stuck antennas and furl solar arrays that used mechanisms that were never expected to fail.
These invaluable skills, tools, techniques and lessons learned should be considered for both manned and un-manned future vehicle applications.