On Shell 5, go to the Ankaran Research Lab. Once inside
the building, go northwest. You will reach a room with some tables
and what appears to be a dismantled missile. Put your pointer
over it and you will learn that there is an item that you can
pick up. It is a "Sturdy Heart". However, if you leave
the building and return, it will be there again. You can repeat
this process to get an unlimited amount of Sturdy Hearts, which
you can sell at any store for an unlimited amount of money.