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Inside the Mission To Europa (arstechnica.com)
An anonymous reader writes: Ars Technica details the political and engineering battles being waged to make it possible for NASA to land a probe on Jupiter's moon Europa. They have new information about mission plans; it sounds ambitious, to say the least. "First, the bad news. Adding a lander to the Clipper will require additional technical work and necessitate a launch delay until late 2023. At that time, the massive Space Launch System rocket NASA is developing could deliver it to Jupiter in 4.6 years. Once there, the lander would separate from the Clipper, parking in a low-radiation orbit.
The Clipper would then proceed to reconnoiter Europa, diving into the harsh radiation environment to observe the moon and then zipping back out into cleaner space to relay its data back to Earth. Over a three-year period, the Clipper would image 95 percent of the world at about 50 meters per pixel and three percent at a very high resolution of 0.5 meters per pixel. With this data, scientists could find a suitable landing site. ...The JPL engineers have concluded the best way to deliver the lander to Europa's jagged surface is by way of a sky crane mechanism, like the one successfully used in the last stage of Curiosity's descent to the surface of Mars. With four steerable engines and an autonomous system to avoid hazards, the lander would be lowered to the moon's surface by an umbilical cord."
The Clipper would then proceed to reconnoiter Europa, diving into the harsh radiation environment to observe the moon and then zipping back out into cleaner space to relay its data back to Earth. Over a three-year period, the Clipper would image 95 percent of the world at about 50 meters per pixel and three percent at a very high resolution of 0.5 meters per pixel. With this data, scientists could find a suitable landing site. ...The JPL engineers have concluded the best way to deliver the lander to Europa's jagged surface is by way of a sky crane mechanism, like the one successfully used in the last stage of Curiosity's descent to the surface of Mars. With four steerable engines and an autonomous system to avoid hazards, the lander would be lowered to the moon's surface by an umbilical cord."
Constellation killed itself, massive cost overruns were pushing it into the $150 - 230 Billion dollar range. SLS is bad, but nowhere near that bad coming in at the $40 - $80 Billion price range.
My way too many hours of Kerbal Space Program make me highly qualified (joke) to say that bringing something back is way harder than just putting stuff there. If you make a later stage twice as big, you need to make every stage leading up to it twice as big as well. Getting samples back up to orbit adds some nontrivially bigger engines and more fuel, even moreso when you think about landing that extra load, and making the orbiter come back to Earth may or may not need bigger engines but will certainly need more fuel. You could get rid of some of the lander's instrument packages and just process things back home, but that's risking an awful lot on a ton of new things that could go wrong... liftoff could fail, rendezvous could fail, anything could fail along the way home, and there's lots more radiation you have to eat.
On-site analysis is much cheaper and more reliable.