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Cassini illustration
Cassini once appeared to be the last giant planetary science mission, but NASA is now planning two such large missions next decade. (credit: NASA)

The next battlestar

It will be weeks, months, or perhaps longer until we get an accurate picture of why the head of NASA’s Science Mission Directorate, Alan Stern, unexpectedly resigned last week, along with the agency’s chief scientist. One suspects that the reasons are budget related, but frankly, at this stage no one other than those directly involved really knows. The long-term science program that Stern and Griffin had proposed in the 2009 budget submission was as realistic as any government plan could be. It took into account the situation of the agency as a whole and gave the scientists some—but not all—of what they wanted.

It was disappointing to see that NASA would have to cut out some of the Mars missions that it had hoped to fly, but the big and very ambitious Mars Sample Return mission is now planned for the end of the next decade. Developing the technology and building the infrastructure for this project will strain future budgets and make extraordinary demands on the skills of academia and industry.

Without a larger science budget envelope for the years 2015–2020, trying to do both the flagship mission and the Mars Sample Return is going to be almost impossible.

In contrast, the proposed “flagship mission” to either Jupiter or Saturn, which is now scheduled to launch in 2017, will not require any fantastically heroic feats of engineering. Designing and building any spacecraft that can survive such a trip and effectively gather useful scientific information is not going to be easy, but will not push the state of the art the way the Mars Sample Return will.

Paying for both missions at about the same time will not be easy, especially if NASA continues to be kept on what is, in relation to what they are expected to do, a near starvation diet. The idea that a major flagship mission can be launched, even with support from European and Japanese partners, with a US expenditure of $2 billion is just not realistic. If that sum could be doubled then NASA would be able to begin work on the project with a reasonable expectation that politically damaging cost overruns and delays could be avoided.

The bad habit of low balling out-year estimates persists not only throughout the US government, but throughout the democratic world and probably the non-democratic world as well (though they are much better at hiding it). This is due to the need to make all the vast number of programs and expenditures that any modern government performs fit within an official fantasy known as a budget. Sometimes programs can be cut, but only by exceptionally ruthless leaders, such as former US Defense Secretary Donald Rumsfeld. He forced the Army to cancel both the new Crusader self-propelled artillery system and the RAH-66 Comanche helicopter—for which he was never forgiven.

Most of NASA’s programs can be seen as an expression of America’s “soft power”. By leading a program that expands our knowledge of the solar system and the universe, the space agency contributes to a global sense that America is the world’s leader in science and technology. Others have reached the same conclusion: ESA’s Rosetta mission to the comet Churymov-Gerasimenko can be seen as an attempt to grab some of that soft power for the EU.

Without a larger science budget envelope for the years 2015–2020, trying to do both the flagship mission and the Mars Sample Return is going to be almost impossible. Yet within the planetary sciences community, and inside the larger space industry, there is powerful pressure to do both. Congressman Bart Gordon’s recent statement that NASA is being asked to do too much with too little is all too true, but it’s hard to see what he can do to fix it. After all, he is just the chairman of one not-very-powerful committee. An increase in today’s overall NASA budget from $17.6 billion to about $20–21 billion would need the sustained attention of the House Speaker, the Senate Majority Leader, and the President, and even then it would be difficult to push through.

One problem that the planetary scientists might soon face is public boredom. After the first few Apollo Moon missions the public and the media basically lost interest. It’s hard to get most of the public excited about the latest construction activities on the International Space Station, but the public did get excited about the Mars Pathfinder rover in 1997 and managed to put pressure on NASA to fly the final Hubble repair mission, now planned for late August of this year. Yet the spectacular pictures from Saturn’s moons from Cassini have barely raised a ripple of interest outside the space industry.

Could it be that the only way to reignite interest in space exploration is to give the public images of people landing on other worlds? It could be that a cycle of public interest is emerging: in one generation the emphasis is on human exploration and the next one is on robots, followed by another one interested mostly in humans. If so, it will be decades before anyone knows this for certain. The only long-term safe bet is to maintain a balanced US space civilian space program.

It could be that a cycle of public interest is emerging: in one generation the emphasis is on human exploration and the next one is on robots, followed by another one interested mostly in humans.

The choice that NASA will make as to the destination of the flagship mission will probably not have that much effect on the gross price. The need for a nuclear power source (which will almost certainly be a new RTG) and the cost of the launch vehicle, the spacecraft’s bus, the communications and flight control hardware, in-space propulsion, ground hardware, and the salaries of the Earth-based humans who will design, build, and operate the spacecraft as well as those who will analyze the data, will dwarf the cost of any specially-built sensors.

So where will NASA choose to go? Indications are that there are only three serious possible targets: a mission to Jupiter’s moon Europa with some sort of lander that might be able to determine if there really is an ocean under all that ice, a mission to Saturn’s moon Titan to follow up on what was learned thanks to the European Huygens probe, or a large spacecraft that would make multiple visits to the bigger satellites around Saturn. These last two missions would need to carry a great deal of fuel if they are to enter orbit around these moons.

The now-canceled Jupiter Icy Moon Orbiter (JIMO) mission showed how difficult such a program would be. Even without nuclear propulsion developing the hardware for such missions is going to be quite a challenge. Getting the systems to be a reliable on these kinds of missions is an exceptionally difficult problem. Doing so with the trickle of electricity that even the best RTG can produce just makes things harder.

Back in 2004 I wrote that Cassini Huygens was going to be the “last battlestar” (see “Cassini-Huygens: the last battlestar”, The Space Review, June 21, 2004). I was wrong. NASA and its partners will continue to build and launch large missions to the outer planets, just not very often and with relatively little new technology. Even with a reasonable budget increase one “battlestar” mission every 20 or 25 years is the best we can expect.