  We study the properties of jets launched by a neutron star spiralling inside
the envelope and core of a red supergiant. We propose that Thorne-Zytkow
objects (TZO) are unlikely to be formed via common envelope (CE) evolution if
accretion on to the neutron star can exceed the Eddington rate with much of the
accretion energy directed into jets that subsequently dissipate within the
giant envelope. We use the jet-feedback mechanism, where energy deposited by
the jets drives the ejection of the entire envelope and part of the core, and
find a very strong interaction of the jets with the core material at late
phases of the CE evolution. Following our results we speculate on two rare
processes that might take place in the evolution of massive stars. (1) Recent
studies have claimed that the peculiar abundances of the HV2112 RSG star can be
explained if this star is a TZO. We instead speculate that the rich-calcium
envelope comes from a supernova explosion of a stellar companion that was only
slightly more massive than HV2112, such that during its explosion HV2112 was
already a giant that intercepted a relatively large fraction of the SN ejecta.
(2) We raise the possibility that strong r-process nucleosynthesis, where
elements with high atomic weight of $A \ga 130$ are formed, occurs inside the
jets that are launched by the NS inside the core of the RSG star.
