But the ARPS development process was "an expensive and total failure", eating up tens of millions of dollars and requiring a large increase in the amount of very expensive plutonium-238 that NASA must buy from the Department of Energy.

This meant that Pluto Express would have to use a regular RTG, while Europa Orbiter was replanned to use a new "Sterling" nuclear generator design which would use less plutonium, but whose total weight would be the same as that for a regular RTG. And so this problem -- along with other weight increases -- forced a significant increase in the weight of both craft, requiring that they be launched on bigger and more expensive boosters.

In the case of Pluto Express, the cost of the required "EELV" booster actually doubled -- which finally forced JPL to drop its long-held plans to model the Pluto Express after the Europa Orbiter after all. (By switching to a completely new design, 70 to 80 kg of weight could be trimmed off the Pluto probe, allowing it to be launched on a smaller Atlas 3.) And various other engineering cost overruns occurred in addition to the nuclear and booster problems.

NASA space science chief Ed Weiler indicated that he was scandalized by the huge initial underestimate of costs by JPL. He also said that while missions proposed by JPL and the Goddard Space Flight Center have not previously had to go through the "Independent Cost Review" process routinely applied to proposals by independent companies, "they definitely will after this year."

During this year, NASA frantically tried to cope with the problem by delaying the launch of the Europa Orbiter and the Solar Probe. (Indeed, the Solar Probe has finally been removed completely from the Outer Planets program -- on the grounds that its scientific goals are just too different -- and the plan is now for JPL to run it as a separate project, under the management of David Lehman.)

In fact, the indications were that the Pluto-Kuiper Express could still be launched on schedule in 2004 if the Europa Orbiter was delayed until 2008 -- and that a small amount of additional funding would allow the Europa probe to be launched in 2007. But at this point, the third factor intervened:

(3) At the meeting, the SSES was stunned to hear from NASA management that NASA has actually decided to drastically cut the Outer Planets program's yearly funding from $250 million per year down to only $150 million per year, apparently largely to cover the increase in Mars program spending -- and that this cut is the main reason it has decided to eliminate the 2004 Pluto Express.

Ed Weiler stated that the Pluto cancellation was on explicit orders from the White House and the Office of Management and Budget -- but, on skeptical questioning by SSES member Stamatios Krimigis, he admitted that it was possible that the White House had reached this decision only because of advice from NASA management itself (and that he himself did not know).

Despite the fact that missions to the outer Solar System are obviously and necessarily much more expensive than Mars missions, the new plan is to set yearly Outer Planets funding at only one-third the level of Mars program funding!

Weiler and JPL's Outer Planets program manager John McNamee both said that NASA's new design for the Outer Planets (or "OP") program is to make its first mission a 2006 launch of Europa Orbiter, with a second OP mission set for 2009-10.