Spacewalkers Troubleshoot Ammonia Leak
Kennedy Supporting Effort to Develop Satellite Servicing Capabilities
Mars Longevity Champ Switching Computers
 |
| Commander Suni Williams (right) and Flight Engineer Aki Hoshide participate in Thursday's spacewalk outside the International Space Station |
Expedition 33 Commander Suni Williams and Flight Engineer Aki Hoshide wrapped up a 6-hour, 38-minute spacewalk at 3:07 p.m. EDT, yesterday i.e. on Nov. 1, 2012.
During the spacewalk which began at 8:29 a.m., Williams and Hoshide ventured out to the port side of the International Space Station’s truss to configure the 2B solar array power channel’s photovoltaic thermal control system (PVTCS) to support ground-based troubleshooting of an ammonia leak.
The spacewalking duo isolated the photovoltaic radiator on the P6 truss from the PVTCS, shutting off the flow of ammonia in and out of it and rerouting the ammonia flow through a spare radiator so the PVTCS can continue operation. Over the following weeks and months, flight controllers at Mission Control Houston will monitor telemetry to see if the leak continues.
If rerouting the ammonia through the spare radiator stops the leak, mission managers will evaluate whether to leave the fix as-is or replace the photovoltaic radiator on a future spacewalk. If the leak continues, additional troubleshooting will be required.
Williams now has a total of 50 hours, 40 minutes of spacewalking time over seven spacewalks. Thursday's spacewalk puts her fifth on the all time list of cumulative spacewalking time. She holds the record for total cumulative spacewalk time by a female astronaut. This was the third spacewalk for Hoshide, who now totals 21 hours and 23 minutes. He holds the record for total cumulative spacewalk time by a Japan Aerospace Exploration Agency astronaut.
This was the 166th spacewalk in support of station assembly, totaling 1,049 hours and 1 minute -- the equivalent of 44 days.
Protective Paint Tested on Space Station Makes for 'Curious' Ride to Mars
 |
| This photo shows the coated fins, center, on Curiosity's Multi-Mission Radioisotope Thermoelectric Generator. The protective coating on the fins was tested as part of the MISSE-2 investigation aboard the International Space Station. (NASA) |
A coating that survived long-term exposure on the International Space Station took an even longer journey on the Mars Curiosity Rover and is protecting the craft's critical power unit as it collects data on Mars. Not all space environments are the same, but if a material can survive for a long time in one space environment, it may prove useful for longer exploration missions.
Curiosity's paint-like spray coating, AZ-2100-IECW, was exposed to the harsh space environment for four years as part of the Materials on International Space Station Experiment (MISSE) investigation. The coating, tested and developed by AZ Technology in Huntsville, Ala., met stringent outgassing requirements and withstood temperature extremes and thousands of hours of ultraviolet radiation from the sun, making it an ideal candidate for the cooling fins on Curiosity's power unit.
"It's exciting to be part of the Mars Science Laboratory mission and see our work on the surface of Mars," said Lynn Leeper, AZ Technology president and chief executive officer. AZ Technology has been developing spacecraft paint and coatings for more than 20 years and has been involved in a number of successful spacecraft and space materials experiments. The company provided 19 different paints, including the AZ-2100-IECW, for the MISSE-2investigation, which flew from August 2001 to July 2005.
The MISSE materials test bed has provided data on the durability of materials that have helped spacecraft designers shorten the development time for satellite hardware components by 50%. Shorter development times result in more affordable spacecraft and ensure materials perform as expected in challenging space environments.
The EC in the coating used for Curiosity stands for electrically conductive. Static electricity can build up on a spacecraft as it is exposed to proton and electron radiation. Electrically conductive or static-dissipative coatings can help protect the electronics from getting zapped. AZ Technology's coating was applied on the Multi-Mission Radioisotope Thermoelectric Generator, or MMRTG. This power unit converts the heat from decaying plutonium-238 into electricity that the Curiosity rover needs to survive.
"Our company has coated parts for many satellites, the International Space Station, and extra-orbital missions, but typically we do not get to see pictures of our work in such an amazing setting," added Leeper. "It makes us feel much closer to the adventure."
The potential for future exploration projects to benefit from space station technology continues to expand, thanks to ongoing use of the orbiting laboratory as a technology test bed. Currently MISSE-8 operates externally aboard the space station, continuing to aid in developing advanced materials to Mars and beyond.
 |
| artist's concept shows a servicing spacecraft, left, approaching satellite needing assistance. NASA is developing technology needed to bring a high- technology "gas pump, robotic mechanic and tow truck" to satellites in orbit. |
With satellites playing increasingly important roles in everyday life, NASA is developing the technology to build Earth-orbiting, roving "service stations" capable of extending the life of these spacecraft. Engineers at the Kennedy Space Center in Florida are assisting the space agency's Goddard Space Flight Center in Greenbelt, Md., in developing the concept for bringing a high-technology gas pump, robotic mechanic and tow truck to satellites in space.
There are 149 government-owned spacecraft and 275 commercial satellites currently in geosynchronous Earth orbit, or GEO, around the Earth. Placed 22,300 miles above the Earth, these satellites play key roles in communications, science, defense and weather monitoring. GEO permits these spacecraft essentially to stay over the same point, allowing for constant coverage of a designated position. This is crucial for satellites relaying meteorology and television signals covering specific portions of the globe.
According to Tom Aranyos, technical integration manager in NASA's Fluids and Propulsion Division at Kennedy, engineers at the Florida spaceport are supporting the hypergolic propellant refueling portion of the Goddard-led study examining how free-flying servicing spacecraft could expand options in orbit for government and commercial satellite owners.
"America depends on satellites in geosynchronous orbit," said Aranyos. "These expensive spacecraft eventually develop systems failures or run out of propellant. Servicing and refueling these satellites can keep them operating longer and in the correct orbit, giving the nation and their owners more value for their investment."
 |
With his feet secured on a restraint on the space station
remote manipulator system's robotic arm, NASA astronaut
Mike Fossum holds the Robotics Refueling Mission payload.
The four tools on the test device cut and manipulated wires,
unscrewed caps, opened and closed valves and transferred
fluid demonstrating that a remote-controlled robot can
service and refuel a satellite.
|
Preliminary work with a technology demonstrator is underway on the International Space Station. The crew of space shuttle Atlantis' STS-135 flight delivered the Robotic Refueling Mission, or RRM, hardware to the station in July 2011.
During a spacewalk, astronauts Mike Fossum and Ron Garan transferred the RRM onto a temporary platform on the Special Purpose Dexterous Manipulator, also known as Dextre, a two-armed robot developed by the Canadian Space Agency that serves as part of the station's Mobile Servicing System. RRM now resides on the Express Logistics Carrier 4 platform outside the station. More
NASA's Mars Odyssey orbiter, already the longest-working spacecraft ever sent to Mars, will switch to some fresh, redundant equipment next week that has not been used since before launch in 2001.
Like many spacecraft, this orbiter carries a pair of redundant main computers, so that a backup is available if one fails. Odyssey's "A-side" computer and "B-side" computer each have several other redundant subsystems linked to just that computer. The Odyssey team has decided to switch to the B-side computer to begin using the B-side's inertial measurement unit. This gyroscope-containing mechanism senses changes in the spacecraft's orientation, providing important information for control of pointing the antenna, solar arrays and instruments.
"We have been on the A side for more than 11 years. Everything on the A side still works, but the inertial measurement unit on that side has been showing signs of wearing out," said Odyssey Mission Manager Chris Potts at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We will swap to the B side on Nov. 5 so that we still have some life available in reserve on the A side."
In many potential problem situations, the Odyssey's autonomous fault-protection response would switch the spacecraft from the active side to the other side. By preserving the capability of switching back to a fully functional A side, the mission continues to have the available protection of switching sides temporarily and correcting any fixable anomaly on the B side.
"The spare inertial measurement unit is factory new, last operated on the day before launch," Potts said.
Odyssey launched April 7, 2001, began orbiting Mars on Oct. 24 of that year, began systematic science observations of Mars in early 2002, and broke the previous record for longest-working Mars spacecraft in December 2010.
The side swap on Nov. 5 will intentionally put Odyssey into a reduced-activity status called "safe mode." As the team and the spacecraft verify all systems can operate well over the following several days, the orbiter will return to full operations, conducting its own science observations, as well as serving as a communications relay for NASA's active Mars rovers Opportunity and Curiosity.
The Mars Reconnaissance Orbiter, which shares the data relay return responsibility for the rovers at Mars, will carry the full burden of relay support for both rovers -- Opportunity and Curiosity -- during Odyssey's side-swap period. There will be a reduction in the total amount of relay data returned from Mars. The rover teams will reduce the amount of data planned for downlinking until Odyssey returns to full capacity after the side swap is complete, and will maintain near-normal tactical operations in the interim.
Odyssey's longevity enables continued science, including the monitoring of seasonal changes on Mars from year to year, and continued communication-relay service.
Odyssey is managed by NASA's Jet Propulsion Laboratory, Pasadena, for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver built the spacecraft. JPL and Lockheed Martin collaborate on operating the spacecraft. For more about the Mars Odyssey mission, visit: http://mars.jpl.nasa.gov/odyssey.
