Splitting Cargo and Crew
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The next generation space shuttle, like its predecessor, will serve many masters, as a cargo ship, a scientific laboratory, a docking platform, and a crew habitat. But according to Mark Fisher, Marshall Space Flight Center’s manager of Exploration Systems, the next shuttle will be designed to "separate cargo from crew."
That change is one lesson learned from flying the current shuttle for the last quarter century: human spaceflight has made cargo more expensive, and cargo can potentially make human spaceflight less safe. By splitting these basic tasks, it is hoped that a more robust shuttle, called the Crew Exploration Vehicle (CEV), will emerge for its first unmanned flight test between 2008 and 2011.
The requirements review will begin sometime around the first of next year, and will be timed to unfold just in time for the current shuttle’s 2010 retirement. A phased approach will then culminate in human flights in 2014.
Fisher unveiled this plan at the Marshall Space Flight Center’s Business Forum on September 20 at Huntsville’s von Braun Civic Center, where he solicited prime contractors to support what is being called the next shuttle’s Architecture Trade Studies.
The concepts behind the Crew Exploration Vehicle currently operate as an open design review, based on the President’s Exploration Initiative calling for a lunar robotic mission in 2008, followed by lunar manned way-stations by 2020 and an eventual Mars’ astronaut.
Fisher sounded a note of optimism about what this open design review might yield. When the first space shuttle was put out for paper studies, "hundreds" of designs poured in. But he said that the shuttle program was being restructured now with a goal of risk reduction for future Mars’ exploration, a task that was not necessarily foremost when the shuttle was first conceived as the space program’s workhorse. Splitting crew and cargo, as two of the most important specialized launch types, is one instance. Another is the way a more environmentally friendly shuttle might come to fly.
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Fisher explained by example that handling problems linked to what liquids were first chosen for shuttle thrusters have had ripple effects, both in cost and safety. "There are many cases from when the shuttle was designed, where the first answer was not always the only, or even the best, answer," said Fisher. He explained that if the 2014 flight for the Crew Exploration Vehicle was optimized now, one might imagine not wanting to include "toxic liquids" like nitrogen tetraoxide, or hydrazine, simply because of their handling challenges when crew safety is paramount. "For the Crew Exploration Vehicle, we might begin with green propellants", with an environmentally safer "retrofit of the thrusters".
Fisher borrowed a term now popular among Defense contractors, called "spiral development", which might be summarized as a graduated "build and test" approach. In previous shuttle concept studies, this was just referred to as integrated engineering, but carries a cache about how a huge program can still start small. Another linguistic addition to NASA planning is called "systems of systems", where one looks to engineer an integrated concept crossing many disciplines and goals, rather than engineering single components and then snapping them together along lines of specialty. Formerly the propellant designers might not be on the same page as the crew’s doctor. An example cited was that a great cargo vessel may not be the best crew carrier.
So, according to Fisher, NASA would like to view the bigger picture when retooling the shuttle to support lunar and martian missions.
Wernher von Braun, one of the NASA pioneers of rocketry, was among those early on who called for a shuttle to support a space station, with the goal of eventually getting over some of the heavy-launch limits required to fly a longer trip to Mars. So in spirit, the 1970′s shuttle design became a transition carrier. Its job was to support an earth-orbitting station, which is now featured among the first two goals for the NASA exploration initiative: get the shuttle back and finish the station.
How these two targets move humans closer to a lunar station or a Mars’ visit remains to be worked out, since that is the third goal for human exploration.
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Fisher highlighted some of the challenges to either a lunar way-station or a Mars’ visit. Foremost were the biomedical issues, "making sure the astronauts are healthy" when they arrive. "The space station has uncovered a host of biohazards", including microbial controls, calcium-bone loss, and radiation exposure. "It is three days to the moon for a crew," said Fisher, "but probably a year to Mars." Many of the human hazards like bone loss or radiation are either cumulative or irreversible, which raises the human health concern to a mission priority.
Even to get back to the moon by next decade, however, means re-engineering Apollo for an entirely different mission. The concerns, according to Fisher, include "surface power and mobility". To use the moon as a way-station means one would like to extract power and some resources in situ, using some advanced ideas of mining the moon for a process that yields water, methane for fuel or other power cycles based on fusion (like heavy-hydrogen fuel, or tritium). "We want to know how to support habitats, a different mission entirely, in closed loops with recycling of our more precious resources. And that human lunar mission has to happen no later than 2020," concluded Fisher.
As NASA has planned the timeline, the new shuttle will exist in a program that is being called Project Constellation: an unmanned test vehicle that depends on advances in robotics and autonomous docking flights. Project Constellation culminates in the 2011 unmanned flight, followed soon by nuclear rockets more geared to faster flights to Mars.
The nuclear program is currently called Project Prometheus. Whether Prometheus will require nuclear propulsion to get to Mars remains an open question, but deeper exploration to Jupiter’s moons or beyond is thought to need a non-chemical propellant or power source. A series of unmanned demonstrations or missions called the Jupiter Icy Moon Orbiter (or JIMO) are currently being studied for exploring Jupiter’s intriguing ice-mantled moons: Europa, Callisto and Ganymede. To get to Jupiter, JIMO will require new technologies from NASA, the Department of Energy and the Office of Naval Reactors.
Fisher concluded with some more near-term projects like the October 18th schedule for launching the 2004 "Demonstration of Automated Rendezvous Test" (or DART). This mission will attempt to guide a Pegasus rocket towards an obsolete MobileCom satellite that is otherwise uncooperative as a docking station, but which carries a video sensor for tracking. Both the satellite and its mating rocket will attempt to hook-up using software control only and navigation derived from the video sensor. "We want to find our capability gaps quickly," said Fisher, "particularly as future missions will increasingly rely on robotics taking over what we don’t want but with humans as decisionmakers when the robotics runs into unknown territory."
So while NASA looks to separate crew and cargo, the result will join machines and men closer than ever before attempted. The results: One lesson learned, another yet to be tried on a scale to reach the moon and Mars.