[FPSPACE] NASA evaluating cutting shuttle flights to ISS
zirconic1 at earthlink.net
Fri Oct 29 21:40:56 EDT 2004
NASA mulls early retirement for space shuttle
Preliminary studies look at off-loading station building to rockets
By James Oberg
NBC News space analyst
Special to MSNBC
Updated: 9:45 p.m. ET Oct. 28, 2004
HOUSTON - Even as NASA gears up for the space shuttle's return to flight next year, officials at the space agency are quietly studying the possibility of cutting back its number of missions and retiring the spacecraft years ahead of schedule, MSNBC.com has learned.
With the shuttle's main objective being the completion of the international space station, such an early retirement would mean either transferring major station assembly and supply jobs to expendable rockets and/or dropping some station components entirely.
No decisions have been made and it is not unusual for NASA to study several courses of action. Any change to the shuttle program's current schedule would have significant economic and diplomatic repercussions at home and abroad, however, which makes even such tentative discussion a touchy topic at the battered space agency.
On condition of anonymity, one current and one former high-level NASA employee, each with direct knowledge of the studies, provided MSNBC with details of the discussions. In addition, two former astronauts and a senior space policy expert, also requesting anonymity, said they had been told of the shuttle discussion by current NASA officials.
NASA spokesman James Hartsfield, who works out of the Johnson Space Center in Houston, repeated Thursday night the space agency's promise to keep flying the shuttle until the space station was completed. He said he was not aware of any studies to reduce the scheduled 28-flight shuttle manifest, but said it was possible that the concept of "completed" could be negotiable.
Fate of space station at stake
The official plan is to retire the space shuttle only after the international space station is completed sometime around 2010. While Russian spacecraft have continued to ferry crew members to and from the station, major construction was effectively halted when the U.S. shuttle program was grounded in the wake of the Columbia tragedy in February, 2003.
At least four more pressurized modules are set to be flown up by the space shuttle: two science labs, one built by Japan, the other by Europe; and two Italian-built service nodes. Current plans also call for the shuttle to deliver a centrifuge module, an observation module, a power platform and additional trusses and solar arrays.
Once the shuttles begin flying again, about 28 more flights will be required to complete these tasks, NASA officials have stated, with servicing of the station expected to eventually be taken over by smaller spacecraft launched on expendable rockets.
As they do now, Russia will continue to send people to the space station aboard its Soyuz vehicles, and may, if construction continues on pace, double the current launch rate of two flights per year. Supplies can be brought up inside robot Russian vehicles and aboard two new vehicles now being developed by Europe and by Japan. If the Chinese are invited into the partnership, they also can transport personnel aboard their Shenzhou manned spacecraft, whose second orbital flight is expected next year.
And at some point during the continued U.S. exploitation of the space station's research capabilities, the new-generation NASA human space vehicle, the "Constellation," may become available for crew and cargo transport. Such missions, however, remain undefined.
What NASA is considering
Retirement of the current U.S. space shuttle fleet is a matter of when, not if.
Specifically, the Columbia Accident Investigation Board has directed NASA to not continue the shuttle program beyond 2010 without a thorough requalification of its aging hardware. Such an effort would be enormously expensive and difficult, if possible at all. The factories where the shuttles were built no longer exist, for example.
It is unlikely, however, that NASA's current 28-flight shuttle manifest could be completed by that date. Typical mission "growth" would likely push the mission number past 30 and even at the best of times, NASA has averaged about five shuttle flights a year.
What some officials at NASA are studying, sources told MSNBC.com, is whether the current mission manifest could be cut back. The cold calculus of space budgets state that for every four or five shuttle missions eliminated, the shuttle program can be terminated a year earlier. And at current operating costs, that frees up about $5 billion a year for future development.
One option being studied would have the shuttles fly 20 missions, the current and former high-level NASA employees told MSNBC. This scenario would retain the Japanese and European science modules aboard shuttle flights, but just barely. In addition, serious studies might still be needed to discuss transferring the most important science consoles from both vehicles into a common, smaller module.
Many officials within NASA believe that a slimmed-down station could still be a very useful place to conduct research. But according to the current NASA employee, "options that limit the shuttle to less that 20 flights make it impossible to live up to existing international agreements."
Those agreements commit the United States to sending up modules built and paid for by Russia, Japan, the European Space Agency, and several individual European nations. Some of these are already years in development, with millions of dollars already spent.
Still, the NASA employee added, "it's unclear that scientific gains are in step with the extra cost of completing the full-up station."
An Apollo-era astronaut told MSNBC that current NASA officials had told him the agency was "studying an 18-flight [manifest] for the shuttle and even asking questions about 11 missions." Another former astronaut confirmed he had been told a similar account.
The senior space policy expert said he had also been told of the studies by a current NASA official and that the studies were showing that NASA could get "a good final configuration with twelve more [space shuttle] flights." In this scenario, according to the expert's source, the shuttle would be used to install all planned pressurized modules but leave off the long trusses and most of the additional solar arrays. Items such as the Centrifuge Accommodation Facility and the much-vaunted Cupola viewing module would get left permanently back on Earth.
The fundamental technical issue facing any replanning effort for completing the space station is to find ways to take cargo currently allocated to the space shuttle and modify it to fly on expendable rockets. The Russian Proton-M and the European Ariane-V booster rockets, as well as the forthcoming U.S.-made "Delta-IV Heavy" rocket are each capable of carrying about twenty tons of cargo into orbits that reach the space station.
Space cargo, however, does not fit neatly into nautical-like shipping containers, stackable and robust. Modules designed to be carried by the space shuttle are being deliberately built to fit the shuttle and rely on its very special support structure.
For example, the shuttle's payload bay contains a series of attach points along both sides and along the keel, and it is here that its structure is reinforced for bearing loads. Special "trunnion pins" on cargo modules are designed to allow the module's mass to hang from them, and to allow the unit to be easily detached or re-inserted in space. To emulate this structure, an entirely new and very strong framework would have to be installed on the front end of an expendable rocket, significantly reducing its performance.
Even more critically, the space shuttle provides an excellent delivery service, bringing the cargo right up next to the space station, where the station's robot arms can remove it from the cargo bay and attach it to the desired location on the station. Without the shuttle's services, a station-bound cargo module would need its own hefty rocket and guidance package that would need years of expensive testing before it could be trusted with irreplaceable station components.
True, robot supply ships have been servicing space stations for decades and will continue to do so. But only about one half of the mass launched is useful equipment and supplies for the station. And because they must attach directly to small Russian docking ports, everything inside these ships must fit through a hatchway less than three feet in diameter.
One powerful argument for retaining shuttles is their ability to bring back large volumes and weights from space -- the so-called "downmass capability". But many within NASA believe that the amount of weight returned can be substantially reduced through careful planning. Furthermore, European and Russian space engineers are testing inflatable heat-shield designs for use with return payloads of varying sizes that could reduce shuttle-based downmass needs further -- and even eliminate the need for a shuttle to conduct this activity entirely.
NASA is not alone in looking at these numbers and wondering if there isn't another option. Earlier this month, Russian space engineer Sergey Shaevich, the space station program director for the Khrunichev Center in Moscow, proposed to NASA that his company's Proton rocket be used for all but two of the currently scheduled shuttle missions.
"The shuttle may not fly so often, and this is a proposal for a solution," he told journalists at the International Astronautical Congress in Vancouver, Canada, early in October. "Only the Columbus [European science lab] and the JEM [Japanese science lab] cannot be delivered" by his company's rockets, he insisted. At the very least, he offered to sell his rockets for any off-loading of cargo made necessary by recent shuttle delays.
The Planetary Society, a California-based space advocacy group, recently proposed its own strategic plan to accelerate U.S. progress in space. The plan, developed by a team chaired by former astronaut Owen Garriott, states that the key to significant advances was shortening the lifetime of the shuttle program.
"Orbiter retirement would be made as soon as the ISS U.S. Core is completed (perhaps only 6 or 7 flights) and the smallest number of additional flights necessary to satisfy our international partners' ISS requirements. Money saved by early [shuttle] retirement would be used to accelerate the CEV development schedule to minimize or eliminate any hiatus in U.S. capability to reach and return from [low Earth orbit]."
Too late to change course?
The sources who spoke with MSNBC for this report said that while it would be very challenging to change the station plan at this point, they consider it doable. They point out that a smaller station could still yield impressive scientific results; the station already provides a significant amount of remote control by scientists back on Earth.
In the end, these studies have shown that the use of expendable launch vehicles is indeed a viable means to reduce the number of shuttle flights, which in turn will accelerate the availability of new-generation human space access both to low Earth orbit -- and potentially beyond. Currently, neither the NASA leadership, nor congressional overseers, nor the White House, are paying serious attention to these plans, but participants believe the engineering logic is growing and new political realities may force consideration of such options.
Meanwhile, the space station program will continue beyond whatever point the shuttle program stops supporting it. The space station can be expected to be expanded and modified with new structures for as long as it orbits Earth, possibly for decades. The end of shuttle support will only close a chapter, not the book, on the international orbital outpost.
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