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A Plutonic Commitment To Space

Lost Horizons or High Frontiers
by Bruce Moomaw
Los Angeles - Feb 11, 2002
Yet another chapter has begun in the saga of the on-again off-again US-funded mission to Pluto and beyond it to the Kuiper Belt -- but this time, despite the fact that the outlook for such a probe in the near future looks bad, it may not actually be not be so grim.

As promised, the Bush Administration's Fiscal Year 2003 budget for NASA completely cancels both the increasingly expensive Europa Orbiter and the proposal (re-inserted last year by Congress over the wishes of both the NASA administration and the White House) for a Pluto and Kuiper Belt flyby probe.

The decision to cancel the Pluto flyby comes despite the fact that NASA has already selected the Applied Physics Laboratory's relatively low-cost "New Horizons" design for a Pluto probe if it actually is launched as early as January 2006 to reach Pluto via a Jupiter gravity-assist flyby.

As foreshadowed, the Bush budget replaces these missions with a new program of Solar Systems missions -- formerly dubbed "Discovery Plus", but now formally enacted as the "New Frontiers" program. With funding caps of $650 million, each mission will be competitively selected from proposals offered by various teams in response to a request every three years from NASA.

New Frontiers would differ from the existing, less expensive Discovery Program of competitively selected planetary probes in one major respect.

Within the Discovery competition, different teams propose not only different solutions but different target worlds and/or scientific goals. With New Frontiers, however, NASA will assign the scientific goal in advance, allowing competition only in how to achieve that goal.

The New Frontiers concept has met with general enthusiasm from planetary scientists, since such competition is likely to reduce total costs as it has done with Discovery missions. But the new program has one serious flaw: it won't begin in time to allow inclusion of the New Horizons mission.

This flaw is serious because it has now been made clear by planetary scientists that they do place a very high value on a Pluto probe launching by mid -decade.

NASA has announced that the selection of the first New Frontiers mission's goal will be "responsive to the results of the Solar System Exploration Decadal Survey" -- an ongoing effort by the National Academy of Sciences to come up with a firm priority list of Solar System exploration goals and NASA missions for the next decade, whose final results will be published this summer.

NASA space science chief Ed Weiler confirmed that during a recent press conference, that NASA might be willing to change its own inclinations and plans in response to such a report.

And, as a central input for their decision, the Decadal Survey Committee asked the members of the Division of Planetary Sciences -- America's main organization of planetary scientists -- to give their own lists of the three most important goals for the Solar System program for the next decade. A total of 44 members responded, providing 132 votes -- and the just-announced results are as follows:

  • Exploration of Pluto and Kuiper Belt objects: 18 votes
  • Physical characterization of asteroids and comets, including Kuiper Belt objects: 15 votes
  • Rendezvous, lander, and sample-return missions to Mars, asteroids and comets: 14
  • Discovery and investigations of other planetary systems (around other stars): 13
  • Continued exploration of Mars (and its moons), with emphasis on the connection with life: 11
  • Continued exploration of Europa: 8
  • A broad Solar System exploration program, with robust support of ground-based telescopic studies: 8

No other category got more than five votes. Even given the considerable blurring between categories in this list, it's clear that the general exploration of Mars for life, and missions to small bodies such as asteroids and comets, are very high on the DPS' priority list -- but among individual missions, the scientists' highest priority for the next decade is clearly a probe to explore Pluto and the Kuiper Belt.

It seems very likely that the final Decadal Survey report will follow suit with a very forceful recommendation that NASA will find it hard to ignore -- and that the first New Frontiers mission is thus very likely to be a Pluto-Kuiper flyby mission.

But in NASA's current plans, the first request for New Frontier mission proposals will come this spring, with the selection of a team in 2003 -- and the mission (whatever it is) not launched until 2007. And this is too late for a Pluto probe to take advantage of Jupiter for a gravity-assist flyby to reach Pluto -- instead, it would have to use an ion drive to fly directly from Earth to Pluto.

NASA and the White House are great enthusiasts for development of such a system -- the new NASA budget also includes $62.5 million for such "in-space propulsion systems" in general, and $46.5 million more to start development of a "Nuclear-Electric Propulsion System", in which a small nuclear reactor would fire such an ion drive continuously even in the dark reaches of the outer Solar System, tremendously increasing both the speed with which outer worlds are reached and the amount of maneuvering and scientific study that could be carried out at the destination.

Even a solar-powered ion drive, firing only until the craft had entered the Asteroid Belt, could accelerate a probe enough for it to fly directly from Earth to Pluto in about a dozen years.

But a nuclear-powered ion drive, even if Congress approves its development, won't be fully flight tested and ready to power deep space missions for close to a decade.

Furthermore a Pluto probe propelled by a solar-powered ion drive would cost a good $150 million more than a simpler one using Jupiter gravity assist.

Secondly, it would start a year later than the current New Horizons plan, and take two years longer to reach Pluto, and consquently increasing the risk that by the time the probe arrives Pluto's atmosphere will have frozen out onto the surface. In addition, Pluto's extreme axial tilt is also causing its south pole to become increasingly hidden in a 50-year-long shadow.

By contrast, New Horizons would reach Pluto by 2015 or 2016 (depending on the booster chosen for it) -- and its total cost is $500 million, as against the $650 million cost limit for a New Frontiers mission.

It will also be able to fly past one to five Kuiper Belt objects during its 5 to 10 year lifetime afterward.

By The Numbers
At this point, commonsense would favor New Horizons - already selected by a New Frontiers-type competitive process - to go ahead as the first "New Frontiers" mission and launch it in January 2006 as planned.

The problem remains the money -- or, more specifically, the funding cycle.

To make it to the launch pad in time, New Horizons needs fully $122 million in funding in Fiscal Year 2003, while the New Frontiers program is assigned only $15 million for that year.

Furthermore, even if all the money NASA plans to spend next year on development of in-space propulsion systems and other new technologies for planetary exploration was diverted to New Horizons, it wouldn't be enough. So this plan would seem, at first, to be impossible.

But is it?

Consider the total funding profiles of New Horizons and the New Frontiers program over the next four years.

New Horizons is intended to cost $122 million in both FY 2003 and FY 2004, but $90 million in FY 2005 and only $30 million in FY 2006. (The other $136 million of New Horizons' cost is for flight operations over its total 11-year lifetime.)

By contrast, funding for New Frontiers is currently set for only $15 million in FY 2003 -- but skyrockets to $155 million in FY 2004, and $240 million in FY 2005 and 2006.

This raises an interesting possibility: could much of the money NASA intended to spend on New Frontiers in 2004 through 2006 be frontloaded instead to the 2003 budget?

A transfer of less than $36 million from each of those three years would allow full funding of New Horizons as the first New Frontiers mission to launch in early 2006 -- and at the same time leave over $280 million additional money in the New Frontiers account to start work on the second New Frontiers mission this decade.

That second mission (presumably picked in 2003 in response to the Announcement of Opportunity already set for this year) could thus get off the ground earlier than now scheduled, in 2008 -- or, at the latest, 2009 -- rather than 2010.

Alternatively, the total $150 million saved by the selection of New Horizons in its current form could be used instead to allow a one-time boost in funding for the second New Frontiers mission to $800 million, rather than $650 million.

This could be important if NASA decides to make the second New Frontiers flight a Europa orbiter -- a scientifically very important mission which will, however, also be a difficult and expensive one.

At the time the current Europa Orbiter was canceled, the Jet Propulsion Laboratory's estimate of its cost had risen to fully $1.2 billion. Competition could probably knock down that cost substantially, but it's hard to see how it could be reduced to $650 million without seriously stripping away many of its science payloads.

In short, selecting the 2006 version of New Horizons by reshuffling the funding schedule in this way seems to be an all-around "win-win" proposition.

It would greatly increase the scientific value of the first Pluto mission by raising the odds that it will arrive before the atmospheric "freeze-out" -- and at the same time, it would save fully $150 million for the New Frontiers program, at precisely the time when that program might need it most.

The big question, of course, is whether Congress (which provided only $30 million last year to start the Pluto mission) would be willing to dramatically boost the 2003 NASA budget by over $100 million against the current wishes of the White House, even if it meant a corresponding drop in NASA's expenses over the next three years.

The possibility of such a move may well depend on just how forcibly the Decadal Survey recommends it.

In a possible omen, the Division of Planetary Sciences issued an official statement on Feb. 8 complaining angrily about the cancellation of the Pluto mission: "[ New Horizons] was recently selected after an open competition in which scientists and their industry partners spent millions of dollars and months of time in a good-faith response to a NASA call for proposals.

"This precedent [by the White House] discourages community participation in NASA's efforts to produce cost-effective missions through competition. Whether New Horizons may be resurrected in the New Frontiers program will depend on its ultimate prioritization in the Planetary Decadal Survey."

Meanwhile, time is running out -- and the seemingly endless "Perils of Pauline" saga of a Pluto probe fast enough to reach the planet before its scientific interest seriously decreases for 250 years is finally coming to a conclusion one way or the other.

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Out To The Horizon Of Sol
Cameron Park - Dec 10, 2001
The saga of NASA's mission to fly by Pluto and its moon Charon continues as NASA selects a spacecraft for design development while still saying the mission will never be funded, but which many in Congress say will. SpaceDaily's Bruce Moomaw reports that the funding impasse might be solved by a new class of Discovery Plus missions.

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