Sacramento - Aug 21, 2003
Startlingly, 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 undergone yet another perilous twist, of a wholly unexpected sort.
In July, the House of Representatives' Appropriations Subcommittee startled everyone by approving a Fiscal Year 2004 budget for "Science, Aeronautics and Exploration" (the unmanned spaceflight portion of the NASA budget) which includes fully $143 million in additional earmarks to committee members' home state projects (some of them not connected to NASA at all), but which compensates for this with $96 million in cuts to four programs.
$20 million was cut out of the Bush Administration's $255 million request for the 2011 James Webb Space Telescope (the Hubble Telescope's successor, formerly called the "Next Generation Space Telescope"); $8 million out of the requested $80 million for the 2010 "Space Interferometry Mission", NASA's second biggest space astronomy project; and $13 million out of the $75 million requested for the Earth Sciences Applications program (which stores, distributes and analyzes the data sent back by America's Earth-resources mapping and climate-observation satellites).
But the House's biggest cut was in the "New Frontiers" program of medium-cost Solar System missions - fully $55 million out of the requested $130 million. And all but $2 million of 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.
This new NASA science budget has already been approved by the full House. If finally approved by the Senate and the White House as well, it would force cancellation of the mission's planned January 2006 launch and its delay to the backup opportunity in 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 almost three years longer to reach Pluto - thus arriving in August 2019 rather than July 2015.
This delay would have a whole series of 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 (and a similar amount of the surface area of its big moon Charon) 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? There has been speculation that its Congressional staffers - who do most of the work of actually examining the details of the federal budget and making recommendations to their Congressmen themselves - may have been misled by recent news reports presenting new scientific evidence 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 two teams of scientists who reported this observation in the July 10 "Nature" took pains to point out that it must be a temporary phenomenon - caused either by a natural "time lag" between Pluto's post-perihelion drop in sunlight intensity and the actual cooling effect this has on its air, or by the fact that Pluto's northern hemisphere, now exposed to more direct sunlight, may have more large patches of dark carbon-compound surface material which absorb sunlight and re-emit it as heat than the southern hemisphere does. In either case, the effect 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 - now 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. We continue to have concerns about the overall cost and schedule for JWST and SIM, and 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 - and his arguments for it were, and continue to be, furiously opposed by almost all planetary scientists themselves. To quote an article by Leonard David in the Feb. 11, 2002 "Space.com":
"O'Keefe... 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 [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 propelled orbiter of Neptune - now a bit closer to the Sun and Earth than Pluto is - consistently predict a flight time of 11-12 years, unless the spacecraft also uses "aerocapture" (braking into orbit around its final destination by actually brushing through the upper layers of that world's atmosphere). Even in that case, an NEP Pluto orbiter could not possibly reach the planet in less than 5-6 years. (And by that time, Pluto may well have lost any atmosphere that could even be used for aerocapture at all!)
And such a mission is 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 themselves 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 that NEP can provide to orbit all three of Jupiter's big icy moons sequentially.
O'Keefe is now pushing JIMO as a major bargain, scientifically speaking - but planetary scientists are once again seriously skeptical. Developing a NEP system - which requires an actual miniature but highly efficient uranium-fueled space going nuclear reactor, powering a set of 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 the basic technologies that would be necessary for it are very poorly defined right now.
Study contracts have only just been issued to three major 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 currently 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 uranium fuel in the reactor presents virtually no danger by itself - U-235 is thousands of times less radioactive than plutonium, until it is piled up into a critical mass and the reactor starts producing power - but any NEP spacecraft will have to run its ion engines, and the reactor powering them, for some time to boost itself out of Earth orbit to escape velocity, and during that time the reactor will start producing dangerous waste products.
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.' "
For all these reasons, there are extremely serious questions about both the cost and the time needed to develop a NEP system. 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 - who generally supports the project - calls it a safe bet that its development will take years longer than NASA hopes, "perhaps up to five to seven years longer."
As for the cost, NASA freely admits it has no idea, except that Prometheus will be very expensive indeed. The White House is requesting $279 million for it this year alone, and $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 projected 2012 launch date, and even this may be over-optimistic. Newhouse says, "I don't know the cost to build JIMO, because until I get the industry studies back, I can put numbers in, but they don't mean anything. They're not real."
These questions of major cost - and of possible safety risks - have, predictably, stirred up a great deal of unease about the project in Congress. Rep. Edward Markey (D-Massachusetts) proposed an amendment to the FY 2004 NASA budget that would pull $115 million out of this year's Prometheus budget and transfer it instead to the EPA's "Superfund" for cleanup of seriously polluted industrial sites. The amendment lost by a 309-114 landslide, but almost half of House Democrats voted for it.
And, during the Feb. 27 House Committee on Science hearing shortly after the Columbia tragedy, Rep. Ralph Hall of Texas (one of Congress' most conservative Democrats) complained that, while NASA was cutting funds for Shuttle upgrades and aeronautics research, "...At the same time, the budget request finds room, I see, for some expensive new missions. A year after OMB canceled the $1 billion Europa Orbiter mission because it was too expensive, NASA is now proposing to take a $4 billion mission to Jupiter's icy moons."
Conservative Republican Rep. Dana Rohrabacher of California agreed, adding: "I noticed in the budget... that it seemed to be a rather expensive project going to the ice moon of Jupiter. And I noticed in the budget it's a $3 billion project. But that's only for the first five years, and it's not scheduled to go up for another 11 years. And I would wonder how much more money we're going to spend on that project."
They ended up voting for it this year; but Joseph Alexander, director of the National Research Council's Space Studies Board, says that as a result of America's current serious fiscal problems and the need to provide additional money to NASA to overcome the continuing very serious problems with its manned space program, Prometheus could well end up sucking most of the money out of NASA's other space science projects - even assuming that Congress is willing to continue the project over the next few years of rapidly growing budget deficits.
O'Keefe's own enthusiasm for JIMO seems to be largely a result of the combination of his earlier experience as Secretary of the Navy (during which he became a strong advocate of nuclear reactors for other purposes than submarines) and his now-apparent serious lack of actual engineering and scientific knowledge on aerospace, which has led him to make such embarrassing mistakes during his recent Congressional testimony as his 7-year overestimate of New Horizons' travel time to Pluto - and more seriously, his testimony just a few days after the Columbia disaster that the detached foam fragment could not possibly have done damage to the Shuttle because it hit at "50 mph... about the speed of a picnic cooler lid blowing off a car ahead of you on the freeway", although news stories for several days had routinely pointed out that the fragment actually hit at about ten times that speed and thus with 100 times that much kinetic energy.
For all these reasons, planetary scientists have serious doubts about JIMO as the next Europa mission (a subject which I will discuss in an upcoming article), and are vehemently opposed to the use of NEP for the first Pluto mission. Last summer's "Decadal Survey Report", which NASA itself commissioned from the National Academy of Sciences to recommend the best form for the Solar System exploration program through about 2013, was enthusiastic about the potential of NEP for Solar System missions in the moderately distant future - with the first perhaps being a Neptune orbiter, an important mission which is hard to do any other way and might be advisable for launch around 2015-20.
But it was highly skeptical about using it for the nearer-future Europa orbiter. And the Survey Committee listed a New Horizons-type mission to flyby Pluto, its moon Charon, and one or more smaller Kuiper Belt objects as by far the most important non-Mars mission to be initiated during this period, and added:
"This mission is ready now, has no requirements for new technology, and can use one of the few remaining RTGs. This is a multiple-object flyby mission designed as the first reconnaissance of a number of Kuiper-Belt objects including the largest and most well studied example, Pluto/Charon. It is premature to consider an orbiter for any of these objects.
"For this reason, and because of the low relative flyby velocities required and the requirement to reach Pluto at the earliest possible date, an NEP option with the necessary advanced ion engines is not appropriate. There is no confidence that both can be developed in time, nor are they necessary for this mission."
The Committee emphasized that Pluto - being a tiny world for which an orbiter would be much less scientifically productive than an orbiter mission to any of the giant planets and its system of moons - instead requires a flyby as early as possible:
"The science at Pluto and Charon is time-critical because of long-term seasonal changes in the surfaces and atmospheres of both bodies. The mandatory objectives of surface mapping and surface composition mapping of Pluto and Charon established by the Science Definition Team would be significantly compromised without an early mission. This is due to Pluto-Charon's ongoing approach to a steep solstice geometry that increasingly hides in shadow large expanses of polar terrain on each object (~200,000 square km of terrain will be lost to imaging and spectroscopic mapping on Pluto alone for each year of arrival delay between 2015 and 2025).
"Beyond the proportional damage this does to the global geology and composition mapping objectives that the SDT set for the mission, this loss of terrains will also severely affect the ability to answer key questions about the extent and nature of the polar volatile reservoirs on Pluto, the origin of the polar cap dichotomy on Pluto, and the possibility that volatiles capable of generating an atmosphere on Charon are sequestered in polar regions.
"Concerning atmospheric science, Pluto's withdrawal from perihelion is widely anticipated to result in a substantial decline, if not a complete collapse, of its vapor pressure supported atmosphere. Searches for an atmosphere around Charon, an extremely desirable mission objective called out in the SDT report, will also be adversely affected, or wholly lost, as will be the opportunity to study atmospheric transfer between Pluto and Charon-something unique in the solar system as far as we know.
"Among the other atmospheric science that will be lost at Pluto if the atmosphere collapses or significantly declines before arrival will be the ability to:
"(1) Test for hydrodynamic escape (a mandatory objective).
"(2) Determine the base pressure and vertical haze/temperature structure of the atmosphere that has been under study since the 1980s (another mandatory objective).
"(3) Pin down volatile transport rates (an extremely desirable objective).
"(4) Sample the atmospheric chemistry and the production of organics and nitriles during its maximum pressure (i.e., perihelion) state (another mandatory objective)."
Regarding NEP, the Survey concludes: "The outer planet missions recommended for flight in this decade (e.g., the Kuiper Belt/Pluto Explorer) can be accomplished without NEP. The development of nuclear technologies, while clearly enabling for many planetary missions, will be controversial in its application and in the public mind. This new initiative was announced too late for the SSE Survey to assemble all of the required expertise and consider all the ramifications of the proposal. The fission-based technology will take a decade to develop in any case, so we have devised a flight program for the next decade that does not require it.
"In the meantime, the SSE Survey recommends that a series of independent studies be undertaken immediately to examine the scientific, technical, and public issues involved in the use of nuclear technologies on planetary spacecraft. A science study should be conducted to determine which mission types are enabled by nuclear technologies and which are not. An engineering study should be undertaken to consider the design and safety aspects of the proposed nuclear technologies. And a study should be conducted to examine public attitudes toward this technology, how to provide the public with an understanding of the issues, and means for mitigating public acceptance problems due to fear and misunderstanding of these issues."
Earlier, in March 2002, NASA's own Solar System Exploration Subcommitee reached a similar conclusion. And, in an open letter circulated through the planetological community in Feb. 2002, outer Solar System experts William B. McKinnon and Jeff Moore were even more forceful:
"Beyond the waste of people's time and resources...there is THE TERRIBLE LOSS TO SCIENCE [emphasis theirs] entailed by waiting for years for new propulsion technologies.
"One does not need nuclear electric propulsion (NEP) to mount a Europa Orbiter mission, nor is there any compelling reason to do so (you're only going to Jupiter, and the technological hurdle is the radiation environment at Europa). The only conceivable results of waiting to do so are a further delay in an overall Europa exploration program, and much greater cost.
"As for Pluto, there is no better time to launch than now, and there is no more economical mission than New Horizons. The whole mission concept has been competitively scrubbed and rescrubbed, and it won't get any cheaper than ~$500 million.
"Waiting for NEP will shorten the trip time and obviate the need for Jupiter, but the wait means less atmosphere to study, more area in permanent darkness, and simply allows Pluto-Charon to retreat farther and farther from scientific scrutiny. Pluto passed perihelion in 1989; it will never be so favorably situated for a long, long, time. And if we wait for NEP, we will surely incur much greater cost.
"Both missions to Pluto and Europa have been repeatedly vetted by the SSES and related advisory NASA structures. Both are strongly supported by the DPS community and Planetary Society members. In particular, no better and more economical first mission to Pluto-Charon and Kuiper Belt can be imagined than New Horizons. In fact, it fits easily within the 'New Frontiers' $650 million cost cap. Derailing the Pluto mission, after it has come this far, is to us, nothing short of criminal."
In short, the planetary science community itself is not only skeptical of any possible move to cancel New Horizons and replace it with a tremendously more expensive Prometheus-type Pluto mission that would take off much later (even if the government replaces JIMO with it as the first NEP mission) - they can accurately be described as furious at the idea, with good reason.
Whether the possibility mentioned by Tim Peterson is the idea of Administrator O'Keefe or of the House Subcommittee's own staff, it can safely be described as an extremely bad idea - whether Project Prometheus is also funded right now or not.
Another possibility hinted at by Tim Peterson in his note - simply canceling New Horizons to cut government's total cost, and replacing it with a later Pluto flyby mission - can also be called a very bad idea. Such a mission would, again, involve considerably higher total cost (it might even require a still very expensive solar-powered ion drive module to replace the Jupiter flyby) and much less science return.
In any case, if the House truly wants to cut NASA's space science budget, two courses of action suggest themselves as being better. The first is to delay the start of Project Prometheus and somewhat stretch out the current over-hasty plans for the development of nuclear-electric propulsion to a more sensible schedule.
The second is for Congress to drop its habit of bleeding off large amounts of funds from the requests by NASA and other federal scientific agencies to fund a seemingly endless parade of small earmarks which those agencies and the White House never even requested, as home-state pork for individual committee members. This Congressional habit, for some reason, has suddenly and massively grown in just the past few years, and is now rousing increasing complaints both from the White House and from scientists.
It remains to be seen whether the Senate will block some or all of the House's new reshuffling of NASA funds - the final NASA budget won't be set until Congressional negotiations are completed late this year or even early next year. But if the House's moves aren't reversed - especially its sudden new attack on New Horizons, less than a year after adding $105 million to NASA's previous budget to start this project - many scientists are going to be very angry, and US citizens in general may also take note of the huge waste of money.
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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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