NASA has announced that the proposed Europa mission, officially included in the space agency’s FY2015 budget request, will be capped at a cost of $1 billion. This makes the mission far cheaper almost any other mission to the Outer Planets and loss costly than the Europa Clipper, which would cost $2.1 billion, or the original Europa Orbiter, which would cost $4.7 billion. This announcement brought a sharp response in a March 5, 2014 post at the Planetary Society blog.
“Why is a billion dollars for a mission ‘cheap’? Mainly because Europa is a particularly difficult destination to explore. The moon orbits within Jupiter's extreme radiation field, which degrades and disrupts electrical equipment on spacecraft. To mitigate the radiation, spacecraft need to carry heavy shielding. This extra shielding adds weight; and weight adds cost. So does a long cruise out to Jupiter, which usually takes around six years, unless this mission launches on the SLS, which can reduce that to less than three. Plutonium, which the spacecraft would likely require for electrical power, also costs a decent amount of money to procure and launch due to the numerous safety reviews and permits. So we're already facing a decent amount of cost just to keep a spacecraft functioning in the Jovian environment. Only one mission has ever been sent to Jupiter with this price tag, Juno, which orbits Jupiter's poles and therefore avoids most of the nasty radiation. A Europa mission won't have that luxury.
“So where does this leave the science? I would be heartbroken to waste a to waste a once-in-a-generation opportunity to explore Europa by skimping on the science. There is so much to learn about this moon and its potential for habitability, that I feel it deserves a big investment if we want to see big returns.”
Without knowing what NASA’s thinking is for a “cheap” mission to Europa, it is difficult to know whether the cost cap will compromise the science or not. It is possible that ongoing advances in materials science will allow a degree of radiation protection that hitherto has not been possible except with heavy materials. It is also unknown whether the $1 billion includes launch costs. Launching a Europa mission on a heavy lift Space Launch System will certainly cut down trip times, as it removes the necessity for multiple gravity assist maneuvers.
On the other hand the $1 billion cap may be a bureaucratic ploy by the space agency to deal with a mission that it did not propose, but rather was mandated by Congress. The idea is that if experts find that it is impossible to do a meaningful mission to Europa for the cost imposed, the idea will be quietly dropped.