In response, O'Keefe at the budget briefing spoke of future nuclear propelled craft to explore outer planet destinations. For Pluto, such a craft would get there faster, then orbit instead of scoot by that faraway world. Once on duty, huge amounts of data would be speedily transmitted, rather than information gleaned during a fleeting flyby, he said.
But the nuclear news was not welcomed in all camps.
"It should be called the Sean O'Grief budget," said one observer.
Some critics claim that O'Keefe needs a fact checker when evaluating time, risk and cost to reach Pluto via nuclear electric propulsion anytime soon. Whereas the cancelled Pluto Kuiper-Belt probe demands only a 9.5 year flight time, the NASA chief pegged that mission as taking 17 years to reach its target.
It is true that low thrust nuclear electric propulsion can gently push for years and accelerate to a great speed. But if you want to come to a stop and enter orbit around Pluto, you have to decelerate from the half-way point, so you end up with a slow transit. "You can have an orbiter, or you can have a fast transit, but not both for any system likely to be ready in the next decade," one scientist complained.
"Going faster will reduce the data because a flyby would be too fast. Slipping into orbit is premature and would add huge expense," the scientist claimed.
Old news or New Frontiers?
The proposed fiscal year 2003 budget for NASA has already received a good news/bad news report card from the Division of Planetary Science (DPS), an arm of the American Astronomical Society, based in Washington, D.C.
Among items saluted by the group was the revival within NASA of nuclear technology to enable future space missions. So too was another new initiative, the New Frontiers line of competitively procured planetary space flight missions.
The DPS, however, noted its concern about the cancellation of the outer planets program, a NASA action that killed the $488 million Pluto-Kuiper Belt project and a projected Europa Orbiter mission.
The cost-capped Pluto-Kuiper Belt mission -- also known as New Horizons -- was recently picked after an open competition. Scientists and industry partners "spent millions of dollars and months of time in good faith response to a NASA call for proposals," the DPS assessment says, only to have that effort nixed.
"This precedent discourages community participation in NASA's efforts to produce cost-effective missions through competition," letter continues. Whether New Horizons might be resuscitated under NASA's New Frontiers program is now tucked away in the to-be-determined column.
Going nuclear, but at what cost?
As for nuclear technology for in-space propulsion and power, the DPS applauded the White House-backed, NASA action. "Development of this technology was terminated in the 1970s and planetary exploration has been limited ever since to long, complex flight missions using conventional propulsion and to spacecraft barely capable of powering a single light bulb," the DPS appraisal explains.
Also backing NASA's nuclear space power and propulsion work, but with a caveat, is Louis Friedman, executive director of The Planetary Society - a public membership space advocacy group.
"Nuclear power is needed for the future of deep space exploration and we welcome the initiative in the President's proposed budget. Tying it to, or funding it by, the cancellation of scientifically approved, popular science missions does not seem right and we will continue to seek approval of the Pluto-Kuiper Belt mission," Friedman told SPACE.com.
Waiting game
NASA's space nuclear initiative is not universally embraced, and for a variety of reasons.
For example, one open letter circulating on the Internet has asked "friends of outer planet exploration" to rally against NASA's current position to derail missions to distant Pluto and Europa. As for Pluto, "there is no better time to launch than now, and there is no more economical mission than New Horizons," the letter argues.
Waiting for nuclear electric propulsion (NEP) will shorten the trip time and obviate the need for a Jupiter swing-by. But that wait means less atmosphere to analyze, more area in permanent darkness, and allows Pluto and its companion, Charon, to retreat farther and farther from scientific scrutiny, explains the letter.
Furthermore, the letter continues, NEP is not needed to mount a Europa Orbiter mission. To tie that propulsion system to Europa exploration, the open message says, means further delay and much greater cost.
Safety first
Another worry by some scientists is the ability of NASA to get any nuclear propulsion system off the ground in the first place.
NASA's Nuclear Systems Initiative is proposed to cost about $1 billion over five years.
Some of those funds would help construct a nuclear electric propulsion system that energizes a set of ion engines. NASA's Deep Space 1 successfully utilized an ion engine in its recently completed mission.
The nuclear electric propulsion system being proposed would be fabricated to stringent safety standards. For instance, the nuclear reactor would stay intact in the event of a launch failure.
Additionally, this nuclear hardware is to be launched in a "cold", non-operating state. The reactor part of any future spacecraft mission would be activated at nearly 1,555 miles (2,500 kilometers) distance from Earth. This altitude was chosen to be compliant with the NASA Orbital Debris Guidelines in case the system failed to start.
How any number of anti-nuclear or pro-environment groups could play a role in slowing down NASA's nuclear agenda is another concern shared by several scientists contacted by SPACE.com. The result could mean a waylaying of outer planet exploration, they contend.
Dialogue needed
At last week's STAIF gathering here, numbers of scenarios regarding use of advanced propulsion were presented.
Muriel Noca of the Outer Planet Mission Architecture Group at the Jet Propulsion Laboratory in Pasadena, California spelled out the benefits of solar electric propulsion and nuclear electric propulsion.
A clear winner of a mission was a solar electric propulsion craft that orbits and drops a lander onto Titan - a moon of Saturn, Noca said. That mission, when tied to aerocapture -- using a thermal protection system to dive into the atmosphere of the moon to slow down and then orbit the world -- equates to a shorter trip time and a greater payload delivered to that mysterious locale.
Nuclear electric propulsion, Noca said, could open up for exploration a host of moons circling Jupiter, such as Callisto, Ganymede, and Europa.
Spacecraft assigned multiple destinations could be accomplished by using nuclear electric propulsion, Noca said. What is needed now, she added, was a dialogue to begin between nuclear space propulsion engineers and scientists. Those discussions would be useful to help define missions of interest and types of science to be carried out.
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