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The Case to Save the Shuttle
By Allen J. RichardsonPosted 10.14.08NOVA
In August of 2003 the Columbia Accident Investigation Board (CAIB) issued its report and concluded, among other things, that the space shuttles were aging, old technology, and too risky. Shortly thereafter President Bush initiated the Constellation program to retire the space shuttles and to replace them with the Ares Launch Vehicles and the Orion Spacecraft, patterned after the Apollo Program. As it stands, the space shuttles are to be retired during 2010, and the Constellation Project is well under way. This is a severe under-utilization of a valuable and still-usable national asset.
SHUTTLE ADVOCATES: SAVE THE SHUTTLE
To alert the public, my colleagues and I formed the Shuttle Advocates Team (SAT), an informal group of mostly retired Rockwell and Boeing engineers, with many years of experience working on the space shuttle Orbiter vehicle, from contract initiation through mission operation. We represent a cross section of space shuttle engineering and provide authoritative information regarding space shuttle performance and future capability. Many of us were also deeply involved in the Apollo Project and are therefore qualified to make comparisons between the space shuttle approach and the Constellation approach to space exploration. We call our team the Shuttle Advocates Team because our mission is to extend the use of the space shuttle system beyond the current end date of 2010. Much of the following information is drawn from material supplied to this writer by SAT engineers.
SPACE SHUTTLE HISTORY AND ITS CURRENT CAPABILITY
To clarify a point, what everyone commonly calls the shuttle or the space shuttle is what our team calls the Orbiter vehicle, that stubby-looking, winged spacecraft that holds the crew and payload. It is this unique United States vehicle that America and the world have come to identify with manned space travel, our "space truck," so to speak. The total space shuttle system consists of four major components: two Solid Rocket Boosters (SRBs), one External Tank (ET), and the Orbiter. The SRBs and the ET are necessary to enable the Orbiter to achieve Earth orbit. Our comments and statements primarily concern the Orbiter vehicles.
The Orbiter named Challenger was lost due to a problem with the SRB circumferential field joint seals ("O-rings") losing their resiliency during a cold winter launch. The improved SRB joint seal has solved that problem. The Columbia spacecraft was lost when a large piece of the ET's external insulation inexplicably detached from a critical area on the tank surface. The critical area is a 15-foot-wide area opposite the Orbiter, which extends aft about five feet from the forward attach point of the Orbiter. The piece of foam struck the Orbiter on the lower surface of the left wing's leading edge, causing a mortal hole that resulted in the loss of the vehicle and crew from reentry overheating. Extensive corrective actions by the ET Project have restored confidence, and successful spaceflights have resumed.
We cite these two accidents to make the point that they were caused by the other shuttle components used during ascent to orbit. The Orbiter spacecraft has never been the cause of any failures. The Orbiter has a perfect record of 123 consecutive successful missions, and we are confident that this record number will grow. We also have a dedicated team of new engineers trained by their mentors, thus insuring that the Orbiter can continue to be operated correctly.
The Orbiters are, of course, aging but have two thirds of their 100 mission design lives (per vehicle) still ahead of them. Sean O'Keefe, a former head of NASA, states in the NOVA documentary that prior to the Columbia accident NASA was planning to keep the space shuttles in operation till 2020. One of the members of SAT recently delivered a technical paper on the built-in space shuttle longevity and compared it to the Douglas DC-3, an aircraft that has been flying for over 70 years and is known for its reliability and ruggedness. The vehicles are well maintained and to this day remain pristine. If you look inside one of the Orbiters today, for example, it looks very similar to the first Orbiter on its maiden voyage back in 1981.
Each of the Orbiters was designed and qualified by tests and analysis for a minimum of 100 space missions. Many of the component test programs were extended to 400 missions to flush out any hidden or unexpected failure modes. The most-used Orbiter in the fleet has only performed 35 missions, so today there is plenty of useful life remaining for additional space missions.
Furthermore, the space shuttles are not old technology. The Orbiter is very similar to military and commercial airplanes, and only evolutionary changes have occurred in airplanes over the last 27 years, as opposed to radical redesigns. Furthermore, those changes are mostly in the avionics, which are readily updated. The more familiar examples of this are the Boeing B-52 and B-1 bombers and the Boeing 747 airliner, all of which are still flying after a longer period, and in the latter case the plane is still in production. The fact is if a spacecraft were designed today to do all the things the space shuttle can do, it would be virtually no different from the existing proven hardware.
A former Orbiter Chief Engineer and VP of Engineering reports, "Many people are unaware that NASA has long maintained an upgrade process to provide current technology to the Orbiter. Starting with the early space missions, many upgrades were installed to improve performance, enhance system reliability, and improve operational safety. More than $1 billion was spent after the Challenger accident on the SRBs, the ET, and the Orbiter. The successful flights after the Columbia accident also show that NASA keeps these shuttle components operating with technology that can meet the mission requirements, consistent with the available funding for modification kits and their installation. Over the years of shuttle operations, these upgrades have received lots of attention as recorded in Reference (1)." (The reference is to a 1999 National Research Council Report entitled "Upgrading the Space Shuttle," published by the National Academy Press.)
As summarized by a former Chief Engineer at Kennedy Space Center, "The Orbiter is the most fantastic flying machine built by man. Its retirement in 2010 is premature and shortsighted. What a waste of unique hardware and all the associated infrastructure and people skills that have been developed at Kennedy Space Center. (This applies as well to the other NASA Centers and to the Corporate Suppliers.) The knowledge base and support for complex space launches take a significant time to establish, and now we're planning to dismantle the talented workforce at that site, together with the software and procedures established over 123 flights, to begin a new program. Skills will be lost as we wait on the Constellation hardware to materialize—a situation very similar to the tough six years between the last Apollo launch (Apollo Soyuz) in 1975 and the drawn-out buildup for the shuttle that finally culminated in its first launch in 1981. Such an extended development with the Constellation elements in these days of budget shortfalls could seriously impact the first scheduled launch of Orion in 2015.
MANNED SPACE VEHICLE EXPLORATION UTILIZING THE SPACE SHUTTLE
The space shuttles, used in concert with the International Space Station (ISS), could provide a viable means of launching manned space vehicles to destinations in our solar system, such as the moon, Mars, or an asteroid. In a single launch, the space shuttle can orbit a 50,000 lb payload, a capability that has allowed us to construct and operate the ISS, which weighs one million lbs. By designing the interplanetary vehicles in modular form and assembling them in orbit utilizing the ISS, we can assemble vehicles of enormous size, if required. This capability would be of indispensable value in the case of a Trans Mars vehicle, which would require the transport of considerable energy to power the vehicle there and back. Should additional single payload launch capability (either in weight or size) be required, a Space Shuttle-C (an unmanned space shuttle variant with increased payload capability) could be built. An additional benefit of this approach is that the ISS could serve as a mission return stopping point, followed by space shuttle transport of astronauts to Earth. This could provide an extra margin of safety for astronauts with unforeseen needs.
The specific advantages of continuing the space shuttle approach to solar system exploration discussed above, as opposed to the current Constellation "space shuttle replacement" approach, are numerous:
1) The space shuttle is a proven and predictable system. In contrast, the Ares-1 Launch Vehicle (ALV) is already beset with technical uncertainties regarding weight limitations and excessive vibration.
2) The space shuttle system is a combination of launch vehicle and spacecraft. The space shuttle Orbiter's on-orbit capabilities include a remote arm capable of manipulating and repairing satellites. The Orbiter also includes an airlock to support extravehicular activities such as space repairs and component assembly. The Constellation system (the shuttle replacement) is a combination of the ALV and the Orion spacecraft. The Orion spacecraft does not have the above capability.
3) The space shuttle system can return both payloads and astronauts from orbit to Earth via a runway landing, while the Constellation approach will revert to parachuting a capsule and the returning astronauts into the ocean, as was the case with the Apollo system.
4) The space shuttle will provide uninterrupted U.S. support to the ISS. Pursuing the Constellation approach will result in a gap of five years or more, when the U.S. will have no capability of delivering supplies to the ISS or of delivering astronauts to the ISS and returning them. Relying on the Russians to fill this gap has become more problematic with the controversy over the Russian invasion of Georgia and the reluctance of the U.S. Congress to renew the legislative exemption that enables NASA to continue to purchase Soyuz spacecraft services as a backup to the space shuttle. The current exemption expires in 2011. Therefore, Congress will need to extend the exemption till the ALV/Orion system is operational.
5) The space shuttle approach will insure ongoing utilization of the ISS, a space colony that humankind should keep in place and operating for the foreseeable future.
6) With the space shuttle system, both the Orbiter and the SRBs are reusable. With Constellation, a relatively larger part of the system, the ALV, is a single-use component.
7) The space shuttle and supporting facilities are paid for!
The advantages of the Constellation approach over the space shuttle approach appear to be nil, the switch to the Constellation approach being predicated primarily on the unwarranted fear of another shuttle "accident" as put forward by the President's CAIB. Fortunately, there is time to reconsider. Even though the dismantling of the space shuttle system has begun, it probably would be more advantageous to stay with this system than to design and construct a whole new system to support the Constellation program. At a minimum, the shuttle system should be extended till its replacement is operational.
The next President and his NASA administrator should also consider a change in the next goal of the U.S. manned space program as well as a change in the hardware to achieve that goal. Scientific interest now centers on Mars rather than on the moon. Four of the five elements of a manned mission to Mars are already in place:
1) The space shuttle (the launch vehicle)
2) The International Space Station, or ISS (the assembly and launch platform for the Trans Mars vehicle)
3) Extensive experience with on-orbit assembly
4) Numerous unmanned precursor missions to Mars
The only missing element is the Mars Aerobraker Vehicle (MAV) to transport the expected three astronauts to and from Mars. Conceptual designs already exist for this vehicle. At an estimated departure weight of 400,000 pounds, a dozen shuttle flights could deliver all needed modules of the MAV to the ISS over a period of years at a cost of perhaps $10 billion. This would leave most of $200 billion (the amount currently contemplated for lunar exploration) to design, build, and assemble the MAV. This redirection would focus the attention and resources of NASA and the aerospace community on the MAV, and would sharpen skills valuable to the nation for further exploration of our solar system. With the manned space program thus redirected, the goal of landing humans on Mars within the next decade appears to be feasible.
My e-mail address is alrichardson2@aol.com
On behalf of the members of SAT, thank you for your interest.
Allen J. Richardson,
Former Orbiter Stress Analysis Supervisor
Editor's Note:
As documented in Space Shuttle Disaster, the Columbia Accident Investigation Board's report makes a strong case for the shuttle's retirement, based on the design and safety issues laid bare by the loss of both Columbia, in 2003, and Challenger, 17 years earlier. Fourteen astronauts died in those accidents. The Bush administration accepted the board's recommendations and announced that the shuttle would be retired in 2010. NASA was ordered to develop new spacecraft that could take astronauts back to the moon and beyond, and many in the space community are excited by the new vision.
But there are dissenters who fervently believe that retiring the shuttle is a mistake. The movement to delay the shuttle's retirement picked up steam in September 2008, as both John McCain and Barack Obama voiced support for extending the shuttle's operation, and a leaked e-mail written by NASA's top administrator revealed that the space agency was studying the feasibility of extending shuttle missions past 2010. It's no surprise that engineers who have worked on the shuttle and its development are among the most passionate advocates for keeping it flying. One of those engineers, Allen Richardson, who appears in the NOVA documentary as well as assisted with technical questions during the film's production, requested the opportunity to express his viewpoint.—Arun Rath, one of the producers of "Space Shuttle Disaster"
Allen Richardson was a structural engineer for Boeing/Rockwell's space operations for nearly 30 years, and worked on both the Apollo and Shuttle programs. He and the other members of the Shuttle Advocates Team will be submitting a version of this letter to Congress.
RELATED LINKS
Space Shuttle Disaster
An investigation uncovers the human failures and design flaws behind the 2003 Columbia tragedy.
A Space Age Controversy
In this opinion piece, aerospace expert John Logsdon makes the case to retire the space shuttle.
The Insider Who Knew
NASA engineer Rodney Rocha, whose warnings about the Space Shuttle Columbia went unheeded, looks back at the disaster.
TV SCHEDULE
EDUCATION
SHOP NOVA
Search NOVA Beta
SPACE & FLIGHT RESOURCES
TEXT
(46)
The Star In You
Just what do astronomers mean when they say we're all made of star stuff?
A One-Way Trip to Mars?
Initial shock aside, some space scientists argue this is the only way to go.
Saving Hubble Update: Expert Q&A
Astronauts John Grunsfeld and Mike Massimino answer questions about their highly risky 2009 mission.
The Case to Save the Shuttle
By Allen J. RichardsonPosted 10.14.08NOVA
In August of 2003 the Columbia Accident Investigation Board (CAIB) issued its report and concluded, among other things, that the space shuttles were aging, old technology, and too risky. Shortly thereafter President Bush initiated the Constellation program to retire the space shuttles and to replace them with the Ares Launch Vehicles and the Orion Spacecraft, patterned after the Apollo Program. As it stands, the space shuttles are to be retired during 2010, and the Constellation Project is well under way. This is a severe under-utilization of a valuable and still-usable national asset.
SHUTTLE ADVOCATES: SAVE THE SHUTTLE
To alert the public, my colleagues and I formed the Shuttle Advocates Team (SAT), an informal group of mostly retired Rockwell and Boeing engineers, with many years of experience working on the space shuttle Orbiter vehicle, from contract initiation through mission operation. We represent a cross section of space shuttle engineering and provide authoritative information regarding space shuttle performance and future capability. Many of us were also deeply involved in the Apollo Project and are therefore qualified to make comparisons between the space shuttle approach and the Constellation approach to space exploration. We call our team the Shuttle Advocates Team because our mission is to extend the use of the space shuttle system beyond the current end date of 2010. Much of the following information is drawn from material supplied to this writer by SAT engineers.
SPACE SHUTTLE HISTORY AND ITS CURRENT CAPABILITY
To clarify a point, what everyone commonly calls the shuttle or the space shuttle is what our team calls the Orbiter vehicle, that stubby-looking, winged spacecraft that holds the crew and payload. It is this unique United States vehicle that America and the world have come to identify with manned space travel, our "space truck," so to speak. The total space shuttle system consists of four major components: two Solid Rocket Boosters (SRBs), one External Tank (ET), and the Orbiter. The SRBs and the ET are necessary to enable the Orbiter to achieve Earth orbit. Our comments and statements primarily concern the Orbiter vehicles.
The Orbiter named Challenger was lost due to a problem with the SRB circumferential field joint seals ("O-rings") losing their resiliency during a cold winter launch. The improved SRB joint seal has solved that problem. The Columbia spacecraft was lost when a large piece of the ET's external insulation inexplicably detached from a critical area on the tank surface. The critical area is a 15-foot-wide area opposite the Orbiter, which extends aft about five feet from the forward attach point of the Orbiter. The piece of foam struck the Orbiter on the lower surface of the left wing's leading edge, causing a mortal hole that resulted in the loss of the vehicle and crew from reentry overheating. Extensive corrective actions by the ET Project have restored confidence, and successful spaceflights have resumed.
We cite these two accidents to make the point that they were caused by the other shuttle components used during ascent to orbit. The Orbiter spacecraft has never been the cause of any failures. The Orbiter has a perfect record of 123 consecutive successful missions, and we are confident that this record number will grow. We also have a dedicated team of new engineers trained by their mentors, thus insuring that the Orbiter can continue to be operated correctly.
The Orbiters are, of course, aging but have two thirds of their 100 mission design lives (per vehicle) still ahead of them. Sean O'Keefe, a former head of NASA, states in the NOVA documentary that prior to the Columbia accident NASA was planning to keep the space shuttles in operation till 2020. One of the members of SAT recently delivered a technical paper on the built-in space shuttle longevity and compared it to the Douglas DC-3, an aircraft that has been flying for over 70 years and is known for its reliability and ruggedness. The vehicles are well maintained and to this day remain pristine. If you look inside one of the Orbiters today, for example, it looks very similar to the first Orbiter on its maiden voyage back in 1981.
Each of the Orbiters was designed and qualified by tests and analysis for a minimum of 100 space missions. Many of the component test programs were extended to 400 missions to flush out any hidden or unexpected failure modes. The most-used Orbiter in the fleet has only performed 35 missions, so today there is plenty of useful life remaining for additional space missions.
Furthermore, the space shuttles are not old technology. The Orbiter is very similar to military and commercial airplanes, and only evolutionary changes have occurred in airplanes over the last 27 years, as opposed to radical redesigns. Furthermore, those changes are mostly in the avionics, which are readily updated. The more familiar examples of this are the Boeing B-52 and B-1 bombers and the Boeing 747 airliner, all of which are still flying after a longer period, and in the latter case the plane is still in production. The fact is if a spacecraft were designed today to do all the things the space shuttle can do, it would be virtually no different from the existing proven hardware.
A former Orbiter Chief Engineer and VP of Engineering reports, "Many people are unaware that NASA has long maintained an upgrade process to provide current technology to the Orbiter. Starting with the early space missions, many upgrades were installed to improve performance, enhance system reliability, and improve operational safety. More than $1 billion was spent after the Challenger accident on the SRBs, the ET, and the Orbiter. The successful flights after the Columbia accident also show that NASA keeps these shuttle components operating with technology that can meet the mission requirements, consistent with the available funding for modification kits and their installation. Over the years of shuttle operations, these upgrades have received lots of attention as recorded in Reference (1)." (The reference is to a 1999 National Research Council Report entitled "Upgrading the Space Shuttle," published by the National Academy Press.)
As summarized by a former Chief Engineer at Kennedy Space Center, "The Orbiter is the most fantastic flying machine built by man. Its retirement in 2010 is premature and shortsighted. What a waste of unique hardware and all the associated infrastructure and people skills that have been developed at Kennedy Space Center. (This applies as well to the other NASA Centers and to the Corporate Suppliers.) The knowledge base and support for complex space launches take a significant time to establish, and now we're planning to dismantle the talented workforce at that site, together with the software and procedures established over 123 flights, to begin a new program. Skills will be lost as we wait on the Constellation hardware to materialize—a situation very similar to the tough six years between the last Apollo launch (Apollo Soyuz) in 1975 and the drawn-out buildup for the shuttle that finally culminated in its first launch in 1981. Such an extended development with the Constellation elements in these days of budget shortfalls could seriously impact the first scheduled launch of Orion in 2015.
MANNED SPACE VEHICLE EXPLORATION UTILIZING THE SPACE SHUTTLE
The space shuttles, used in concert with the International Space Station (ISS), could provide a viable means of launching manned space vehicles to destinations in our solar system, such as the moon, Mars, or an asteroid. In a single launch, the space shuttle can orbit a 50,000 lb payload, a capability that has allowed us to construct and operate the ISS, which weighs one million lbs. By designing the interplanetary vehicles in modular form and assembling them in orbit utilizing the ISS, we can assemble vehicles of enormous size, if required. This capability would be of indispensable value in the case of a Trans Mars vehicle, which would require the transport of considerable energy to power the vehicle there and back. Should additional single payload launch capability (either in weight or size) be required, a Space Shuttle-C (an unmanned space shuttle variant with increased payload capability) could be built. An additional benefit of this approach is that the ISS could serve as a mission return stopping point, followed by space shuttle transport of astronauts to Earth. This could provide an extra margin of safety for astronauts with unforeseen needs.
The specific advantages of continuing the space shuttle approach to solar system exploration discussed above, as opposed to the current Constellation "space shuttle replacement" approach, are numerous:
1) The space shuttle is a proven and predictable system. In contrast, the Ares-1 Launch Vehicle (ALV) is already beset with technical uncertainties regarding weight limitations and excessive vibration.
2) The space shuttle system is a combination of launch vehicle and spacecraft. The space shuttle Orbiter's on-orbit capabilities include a remote arm capable of manipulating and repairing satellites. The Orbiter also includes an airlock to support extravehicular activities such as space repairs and component assembly. The Constellation system (the shuttle replacement) is a combination of the ALV and the Orion spacecraft. The Orion spacecraft does not have the above capability.
3) The space shuttle system can return both payloads and astronauts from orbit to Earth via a runway landing, while the Constellation approach will revert to parachuting a capsule and the returning astronauts into the ocean, as was the case with the Apollo system.
4) The space shuttle will provide uninterrupted U.S. support to the ISS. Pursuing the Constellation approach will result in a gap of five years or more, when the U.S. will have no capability of delivering supplies to the ISS or of delivering astronauts to the ISS and returning them. Relying on the Russians to fill this gap has become more problematic with the controversy over the Russian invasion of Georgia and the reluctance of the U.S. Congress to renew the legislative exemption that enables NASA to continue to purchase Soyuz spacecraft services as a backup to the space shuttle. The current exemption expires in 2011. Therefore, Congress will need to extend the exemption till the ALV/Orion system is operational.
5) The space shuttle approach will insure ongoing utilization of the ISS, a space colony that humankind should keep in place and operating for the foreseeable future.
6) With the space shuttle system, both the Orbiter and the SRBs are reusable. With Constellation, a relatively larger part of the system, the ALV, is a single-use component.
7) The space shuttle and supporting facilities are paid for!
The advantages of the Constellation approach over the space shuttle approach appear to be nil, the switch to the Constellation approach being predicated primarily on the unwarranted fear of another shuttle "accident" as put forward by the President's CAIB. Fortunately, there is time to reconsider. Even though the dismantling of the space shuttle system has begun, it probably would be more advantageous to stay with this system than to design and construct a whole new system to support the Constellation program. At a minimum, the shuttle system should be extended till its replacement is operational.
The next President and his NASA administrator should also consider a change in the next goal of the U.S. manned space program as well as a change in the hardware to achieve that goal. Scientific interest now centers on Mars rather than on the moon. Four of the five elements of a manned mission to Mars are already in place:
1) The space shuttle (the launch vehicle)
2) The International Space Station, or ISS (the assembly and launch platform for the Trans Mars vehicle)
3) Extensive experience with on-orbit assembly
4) Numerous unmanned precursor missions to Mars
The only missing element is the Mars Aerobraker Vehicle (MAV) to transport the expected three astronauts to and from Mars. Conceptual designs already exist for this vehicle. At an estimated departure weight of 400,000 pounds, a dozen shuttle flights could deliver all needed modules of the MAV to the ISS over a period of years at a cost of perhaps $10 billion. This would leave most of $200 billion (the amount currently contemplated for lunar exploration) to design, build, and assemble the MAV. This redirection would focus the attention and resources of NASA and the aerospace community on the MAV, and would sharpen skills valuable to the nation for further exploration of our solar system. With the manned space program thus redirected, the goal of landing humans on Mars within the next decade appears to be feasible.
My e-mail address is alrichardson2@aol.com
On behalf of the members of SAT, thank you for your interest.
Allen J. Richardson,
Former Orbiter Stress Analysis Supervisor
Editor's Note:
As documented in Space Shuttle Disaster, the Columbia Accident Investigation Board's report makes a strong case for the shuttle's retirement, based on the design and safety issues laid bare by the loss of both Columbia, in 2003, and Challenger, 17 years earlier. Fourteen astronauts died in those accidents. The Bush administration accepted the board's recommendations and announced that the shuttle would be retired in 2010. NASA was ordered to develop new spacecraft that could take astronauts back to the moon and beyond, and many in the space community are excited by the new vision.
But there are dissenters who fervently believe that retiring the shuttle is a mistake. The movement to delay the shuttle's retirement picked up steam in September 2008, as both John McCain and Barack Obama voiced support for extending the shuttle's operation, and a leaked e-mail written by NASA's top administrator revealed that the space agency was studying the feasibility of extending shuttle missions past 2010. It's no surprise that engineers who have worked on the shuttle and its development are among the most passionate advocates for keeping it flying. One of those engineers, Allen Richardson, who appears in the NOVA documentary as well as assisted with technical questions during the film's production, requested the opportunity to express his viewpoint.—Arun Rath, one of the producers of "Space Shuttle Disaster"
Allen Richardson was a structural engineer for Boeing/Rockwell's space operations for nearly 30 years, and worked on both the Apollo and Shuttle programs. He and the other members of the Shuttle Advocates Team will be submitting a version of this letter to Congress.
RELATED LINKS
Space Shuttle Disaster
An investigation uncovers the human failures and design flaws behind the 2003 Columbia tragedy.
A Space Age Controversy
In this opinion piece, aerospace expert John Logsdon makes the case to retire the space shuttle.
The Insider Who Knew
NASA engineer Rodney Rocha, whose warnings about the Space Shuttle Columbia went unheeded, looks back at the disaster.
TV SCHEDULE
EDUCATION
SHOP NOVA
Search NOVA Beta
SPACE & FLIGHT RESOURCES
TEXT
(46)
The Star In You
Just what do astronomers mean when they say we're all made of star stuff?
A One-Way Trip to Mars?
Initial shock aside, some space scientists argue this is the only way to go.
Saving Hubble Update: Expert Q&A
Astronauts John Grunsfeld and Mike Massimino answer questions about their highly risky 2009 mission.
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