Technology for everything is constantly getting smaller and lighter. By the time something like this mission launches we may well be able to do far more than we can now.

taken to it's logical conclusion, that's a great argument to NEVER launch a mission, because by the time we're finished building it and flying it there, we could alreqdy do much better.

The key factor is the technology available NOW, when we design the mission, not what might be available somewhere in the world, the day the mission launches, having been built and tested a couple of years back, and designed in a process going back 5-10 years.

Remember how a deep a hole NASA got into with things like the X-33 where it got into the mess of developing new technology that didn't exist yet? That's right, something that doesn't exist clearly doesn't work. It MIGHT work in the future, but it doesn't work now.

So confine your plans to what can be done, now with the technology and money we've got.

And read a book on Europa before you blithely dream about multi-part penetrators. That damn ice cover is a MINIMUM of 19 km thick - that's 12 miles, the way you count over there...