You may have better shelves than I do. (Though “off the self” might be more appropriate.)

As to science instruments, those are instruments that do new things. Off-the-shelf science instruments get you off-the-shelf science. Off-the-shelf science is indeed probably cheaper than cutting edge science.

As to the spacecraft, new technologies give higher capabilities and reliability than old technologies do. Certainly “every single part” isn’t new, though these parts have to be assembled in new ways that guarantee performance at Europa. Power, thermal, comm, radiation — it’s all different at Europa than at Mars or Mercury. A design architecture that works for on-orbit imaging of Mars simply won’t work for Europa.

The way I look at it is that each new mission is an opportunity to be creative with new technology. If the goal is shelf-cleaning, then that creativity isn’t exercised.

Is there no instruments that are just plugged in as an off the self design?

No shortage of those …

http://nssdc.gsfc.nasa.gov/planetary/discovery.html

It is more the case that NASA does a very poor job updating their website. That text is probably early 2000’s vintage. The AO solicitations are what count. Go read those.

You’re right, but …

“The cost for the entire mission (design, development, launch vehicle, instruments, spacecraft, launch, mission operations, data analysis, education and public outreach) must be less than $425 million.”

http://discovery.nasa.gov/p_mission.cfml

Now, it’s not as if NASA’s right hand always knows what the left hand is doing, but the words in the solicitation are what count.

No, it doesn’t. The S/C cost has nothing to do with the LV. The LV typically isn’t selected until the S/C is well into Phase C/D. During the proposal phase and Phase A/B (and we are talking NASA SMD missions here), the S/C has to be compatible with a class of LV’s. For ELV, this included Atlas, Delta, and Falcon.

“By the way, the cost cap for at least a Discovery mission is $425M, and that *includes* the launch vehicle.”

No, it doesn’t. For Discovery and NF, the cost cap explicitly excludes the LV and has for several cycles now. You need to do a little better research next time. Furthermore, the next Discovery mission will be capped at $450M based on the announcement of the release of the Draft AO that came out a couple of weeks ago. Here is the relevant text:

“Investigations are capped at a Phase A-D cost of $450M (FY 2015), excluding standard launch services. The now-standard 25% minimum reserve on Phases A-D will be required within the cost cap.”

Link is here: