ISS Robotic External Ammonia Leak Locator (ISS External Leak Locator ) - 10.25.17

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Leaks can be potentially dangerous for a spacecraft, especially when they affect environmental control and life support systems. Escaping fluids or gases also jeopardize a spacecraft's stability. Currently, ISS crew must do a spacewalk to find and repair leaks outside the station. A robotic method to test for and quickly pinpoint external leaks greatly reduces the time and risk for crew members with these repairs. The ISS Robotic External Leak Locator demonstrates that commercial off-the-shelf (COTS) products can be adapted for effective spacecraft external leak location. In the near future, such instruments may be further developed not only to find leaks but also verify repairs have effectively fixed them.
Science Results for Everyone
Initiation of this investigation has been affected by the loss of the Orbital-3 launch vehicle and mission in October 2014.

The following content was provided by Jesse A. Buffington, and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: Robo Ext Leak Locator

Principal Investigator(s)
Jesse A. Buffington, Johnson Space Center, Houston, TX, United States

Co-Investigator(s)/Collaborator(s)
Dino Rossetti, M.S., Conceptual Analytics, MD, United States

Developer(s)
NASA Johnson Space Center, Houston, TX, United States
NASA Glenn Research Center, Cleveland, OH, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
NASA Research Office - Human Exploration and Operations Mission Directorate (NASA Research-HEOMD)

Research Benefits
Scientific Discovery, Space Exploration

ISS Expedition Duration
September 2015 - March 2016

Expeditions Assigned
45/46

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • The International Space Station (ISS) and future manned spacecraft can be negatively affected if damage or flaws cause leaking fluids/gasses to be lost overboard to the vacuum environment. 
  • Space Station systems can monitor themselves for pressure drops which ground operators use to Detect that a leak is occurring.
  • Repair techniques have been design and built, but the critical missing link is the step between Detecting that a leak is occurring and actually installing the Repair: Locating the source of the Leak, such as the area a hole has penetrated a tube, is required before installing a Repair. 
  • There are several key questions that must be addressed to address this missing link:
1. How would leaks interact with the External Environment?
2. How would leaks interact with Spacecraft Structure?
3. What instruments are most appropriate for Leak Locating?
4. What techniques would one use to go from “sensed data” to “leak locating”?
5. What is the “smallest leak” that can be located?
  • The ISS External Leak Locator is a Technology Demonstration Payload to show that a Commercial Off-the-Shelf (COTS) pressure sensor and mass spectrometer can be used to detect the location of leaks and provide quick confirmation of a successful leak repair, mitigating the risk to ISS and future spacecraft. 
  • The payload operates by detecting increases in local total pressure and gas-specific partial pressures caused by the leaks or vents from pressurized systems on the ISS to the vacuum of space.

Description
The ISS Robotic External Leak Locator is both a Payload that conducts fundamental scientific research as well as a “Tech Demo” that demonstrates capability immediately relevant to the ISS Vehicle. In general, all human spaceflight vehicles are susceptible to failures driven by flaws or damage that allow gases such as the Crew’s breathing atmosphere or “working fluids” such as Ammonia used in Thermal Control Systems. In the specific case of the ISS, the Active Thermal Control System (ATCS) uses Ammonia (NH3) as the medium for heat transport. The ISS ATCS has experienced several leaks over the course of the life of the vehicle to date, all of which have been successfully recovered. However, there remains a risk, till the end of the ISS service life, that more severe leaks could occur or not be isolated with existing system capabilities. The Leak Locator Tech Demo Payload is useful both to ISS and future spacecraft. During the Tech Demo, the Leak Locator is passed out through JAXA’s Japanese Experiment Module Airlock (JEM A/L). Then it is picked up by ISS Robotics (the Special Purpose Dexterous Manipulator as mounted on the Space Station Remote Manipulator System – SPDM/SSRMS) and positioned/pointed around the ISS to detect relative changes in both Total and Partial Pressure as a function during motion. This allows characterization of both the natural environment as well as induced environmental effects that are caused by the interaction of the ISS with the natural environment. Leak Locator Payload Objectives can be separated into two groups: Characterize the natural background environment; Detect partial and total pressure increases On-Orbit Activities are selected to gather data needed for correlation of the Leak Locator Instruments’ perception of the environment to historical data and current analytical models. This correlation allows for the determination of the capabilities and limits of the core instruments as a Leak Locator for ISS. Data help to formulate recommendations and decisions about keeping the Leak Locator Payload for future use on ISS as well as definition of requirements and design features for future Leak Locators supporting other Programs and Vehicles operating in Low Earth Orbit and beyond.

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Applications

Space Applications
Future human missions exploring beyond Low Earth Orbit might use robotic equipment to make spacecraft repairs, including fixing leaks of fluid or gas from the spacecraft. The ISS Robotic External Leak Locator mounts on the ISS robotic arm which can be driven by ground operators to inspect the exterior of the ISS for leaks and analyze how they interact with the vacuum of space and affect the spacecraft. The investigation determines the minimum amount of leakage that can be remotely detected, and provides valuable data for future human mission destinations such as the moon, Mars, or asteroids.

Earth Applications
The ISS Leak Locator's main components are a highly sensitive commercial residual gas analyzer and a highly sensitive pressure gauge that can be used for a wide range of purposes in space and on Earth. The instruments can be used in Earth’s upper atmosphere to measure charged atoms, which helps to improve predictions of how our atmosphere interacts with the solar wind. In addition to improving climate models and environmental analysis, findings from these instruments could improve the design of satellites for Earth applications.

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Operations

Operational Requirements and Protocols

The Robotic External Leak Locator is stowed once it arrives at the ISS until the JEM Airlock and ISS Robotics (SSRMS/SPDM) as well as Crew Time for destow become available. The crew then destow the Leak Locator and install it onto the JEM Airlock Slide Table. The JEM Airlock is depressurized and the Leak Locator is passed to the External Environment. Ground Operators (JSC-MOD ROBO Console) control the SPDM, as mounted on the SSRMS, to pick up the Leak Locator from the JEM Airlock Slide table. The SPDM/SSRMS is driven to predetermined positions and points the Leak Locator to gather data at each location. Data gathered by the Leak Locator’s core instruments during the Tech Demo is down-linked and processed for display in near-real-time on the ground in a backroom environment. Once leak testing operations have been completed, the steps are reversed (ground operators use the SPDM/SSRMS to return the Leak Locator to the JEM A/L which is then repressurized, returning the Leak Locator to IVA Crew for stowage). The data are analyzed and evaluated in detail after the on-orbit operations are completed, with findings, conclusions and recommendations captured in an Detailed Test Report and provided to the ISS Vehicle Office. The Leak Locator remains stowed on-orbit at the discretion of the ISS Program for future utilization or actual Leak-Locating events. Operational Protocols [nasa.gov]: The Leak Locator is passed out through JAXA’s Japanese Experiment Module Airlock (JEM A/L) to be picked up by ISS Robotics (SPDM/SSRMS) and positioned/pointed around the ISS to detect relative changes in both Total and Partial Pressure as a function during detection motion. This allows characterization of both the natural vacuum space environment as well as changes that are caused by potential leak(s). Leak Locator Payload Objectives are divided into two groups: characterize the natural background environment, and detect partial and total pressure increases.

The Leak Locator is passed out through JAXA’s Japanese Experiment Module Airlock (JEM A/L) to be picked up by ISS Robotics (SPDM/SSRMS) and positioned/pointed around the ISS to detect relative changes in both Total and Partial Pressure as a function during detection motion. This allows characterization of both the natural vacuum space environment as well as changes that are caused by potential leak(s). Leak Locator Payload Objectives are divided into two groups: characterize the natural background environment, and detect partial and total pressure increases.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

Information Pending

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Related Websites

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Imagery

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The completed External Leak Detector flight unit. The two particle intake ports are covered by the brown plastic covers. These are removed by the crew members once the unit arrives in space. Image courtesy of Dr. Edward Cheung.

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Engineers at Goddard prepare the External Leak Detector for flight. Image courtesy of NASA.

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The view inside the glass window of the External Leak Detector vacuum piping system. The glowing filament of the ISS Robotic External Ammonia Leak Locator (ALL) Sensor can be seen.  Image courtesy of Dr. Edward Cheung.

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Dextre robotic arm is used to traverse and point the External Leak Detector along coolant lines to test for potential leaks.  Image courtesy of Dr. Edward Cheung.

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