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Pluto Mission Might Get Nuked In Growing Budget Crisis

any probe to pluto will be an expensive operation
by Bruce Moomaw
Sacramento - Aug 21, 2003
The saga of NASA's "New Horizons" Pluto flyby probe - which, earlier this year, finally received official approval and funding from NASA, the White House and Congress, and seemed assured of launch in 2006 - has now undergone yet another perilous twist, of a wholly unexpected sort.

In July, the House of Representatives startled everyone by approving a Fiscal Year 2004 budget for the unmanned spaceflight portion of the NASA budget which includes fully $143 million in additional earmarks to committee members' homestate projects (some of them not connected to NASA at all), but which compensates for this with $96 million in cuts to four programs.

The House's biggest cut by far was in the "New Frontiers" program of medium-cost Solar System missions - fully $55 million out of the requested $130 million. And virtually all that request had been for New Horizons, which was finally accepted by NASA and the White House as the first New Frontiers mission because Congress itself insisted on it and added $105 million to NASA's FY 2003 budget to initiate the program only a few months ago.

If the Senate and the White House finally approve this cut, it would force cancellation of the mission's planned January 2006 launch and its delay to Feb. 2007. And since the probe, if launched then, cannot make a gravity-assist flyby of Jupiter to catapult itself with renewed speed out to Pluto, it will take much longer to reach Pluto - arriving in August 2019 rather than July 2015.

This delay would have many serious effects. The longer flight would add about $80 million to the project's current $490 million total price tag - and (unlike a delay in any other NASA mission), it would also seriously reduce the mission's science output, since Pluto is both moving away from the Sun in its lopsided orbit and (because it "lies on its side" rotation-wise) is currently having a larger and larger share of the surface around its south pole shrouded in permanent darkness that will not be reversed for another 120 years. During that four-year delay, almost 5% more of the planet's total surface area would be thus concealed from any visiting space mission.

More seriously, Pluto's very thin but highly scientifically interesting atmosphere - one of the main scientific goals of any Pluto mission - is considered very likely to freeze out onto the planet's surface by 2020 at the latest as Pluto moves further away from its 1989 perihelion, and will not be reborn again until the planet is nearing the end of its next 248-year revolution around the Sun. And the resulting thin frost of frozen nitrogen and methane will also likely interfere seriously with any spacecraft's attempts to use near-IR spectrometry to map the composition of Pluto's surface.

So why did the House do this? Congressional staffers may have been misled by recent news reports indicating that, to the surprise of astronomers, Pluto's atmosphere actually seems to have warmed up about one degree C between 1988 and 2002. The staffers may have thus concluded that the first visit to Pluto can be safely delayed some years with little science loss.

If so, they would be mistaken. The scientists who reported this observation in the July 10 "Nature" took pains to point out that - whichever of two possible causes is responsible - it must be a temporary phenomenon that can't possibly last more than a few more years, after which Pluto's air is likely to cool down rapidly.

However, Tim Peterson - the VA-HUD Subcommittee staffer largely responsible for describing the NASA portion of its budget - tells "SpaceDaily" that other factors were responsible:

"In general, the reductions were taken against specific programs that have a large growth when compared to the previous fiscal year, or where there are significant program concerns that would rationalize the decision.. The Pluto mission is a concern because of the limited science return from a fly-by mission as opposed to a mission in the future that could use nuclear propulsion, which is fully funded in the House bill. As you are also aware, there is a finite amount of funding available to the Committee for its agencies, so this must also weigh upon our decision regarding total program funding levels."

The possibility that Peterson mentions of replacing New Horizons completely with a huge, very expensive nuclear-powered Pluto orbiter that would supposedly be more scientifically "cost-effective" was repeatedly advocated by NASA Administrator Sean O'Keefe back in early 2002 - although his arguments for it are furiously opposed by almost all planetary scientists themselves. Leonard David says in the Feb. 11, 2002 "Space.com":

"...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 [NEP-accelerated] flyby would be too fast... but slipping into orbit around Pluto instead is premature and would add huge expense,' the scientist claimed.

Indeed, engineering studies of a nuclear-electric orbiter of Neptune - now a bit closer to the Sun and Earth than Pluto is - consistently predict a flight time of 11-12 years. And such a mission to Pluto would be very unlikely to even be launched before about 2014-15 - the time at which New Horizons, as currently planned, will actually reach Pluto.

At O'Keefe's urging (again catching planetary scientists totally by surprise), the White House's latest NASA budget favors replacing earlier plans to launch a chemically-propelled spacecraft into orbit around Jupiter's biologically interesting moon Europa with a huge, NEP-powered "Jupiter Icy Moons Orbiter" (JIMO) which would use the vast delta-V provided by NEP to orbit all three of Jupiter's big icy moons sequentially.

O'Keefe is now pushing JIMO as a major bargain - but planetary scientists are once again seriously skeptical. Developing a NEP system - which requires a miniature but highly efficient spacegoing nuclear reactor, powering a dozen or so ion engines much bigger than any yet flown - is universally recognized as very difficult, although it will certainly be done at some point. Even its most basic technologies are very poorly defined right now.

Study contracts have only just been issued to three prime contractors to develop concepts for such a NEP drive, and their results won't be available until the end of this year. Alan Newhouse - the director of NASA's new "Project Prometheus" to develop NEP - says: "We've said 'please study this mission; tell us if it makes sense; tell us what the technologies are; tell us the whole package. What kind of parameters are we talking about here? What's the mass going to be? What's the trip time?"

It isn't even certain yet that such a system can be made lightweight enough to be safely launched with any booster the US has or is planning to develop. Baseline weight for a NEP orbiter - for either Jupiter's moons or Pluto - is about 20 metric tons, which could only be launched to a 300-km altitude Earth orbit by the most powerful versions of the new Atlas 5 and Delta 4 boosters. And NASA wants to put any such NEP spacecraft into an initial orbit at least 1000 km up, to prevent any risk that its reactor might fail prematurely and then reeenter Earth's atmosphere any time within the next few hundred years.

The August 11 "Aviation Week" adds: "Launch vehicle throw weight is only one of the big questions that will need answering before JIMO gets underway. No one has ever built a space-based fission reactor with the reliability to keep working long enough to make a difference on an extended mission to Jupiter in terms of transit time, instrument power and data return. It isn't clear how the heat of the nuclear reaction can best be converted into electricity on the mission. Nor is it certain how that electricity can best be converted into thrust [by some form of ion drive], and what would be the best trajectory to take advantage of that thrust.

"Finally, it isn't clear how all the parts of the whole system would work together. 'It's the integration that's the long pole,' Newhouse said. 'We just haven't done anything like this before.' "

NASA's current plans call for launching JIMO in 2012 - but most outside engineers regard this estimate as absurdly optimistic. Louis Friedman, director of the Planetary Society, calls it a safe bet that its development will take years longer than NASA hopes, "perhaps up to five to seven years longer." And - unless JIMO is replaced by the new suggested Pluto orbiter as the first NEP mission - the Pluto orbiter likely won't even be launched until 2020 at the earliest!

As for the cost, NASA freely admits it has no idea, except that Prometheus will be very expensive indeed. The White House is requesting $3 billion for the program's first five years. NASA space science director Ed Weiler says that the entire project could cost $9 billion by the time of JIMO's launch, and even this may be over-optimistic.

Back to Part Two

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Atlas V Chosen To Launch New Horizons Mission
Florida - Jul 24, 2003
NASA has chosen the Atlas V expendable launch vehicle provided by Lockheed Martin Commercial Launch Services, Inc. as the launch system for the proposed Pluto New Horizons mission. The mission is scheduled for launch to Pluto in January 2006.



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