  Molecular outflows are believed to be a key ingredient in the process of star
formation. The molecular outflow associated with DR21 Main in Cygnus-X is one
of the most extreme, in mass and size, molecular outflows in the Milky Way. The
outflow is suggested to belong to a rare class of explosive outflows which are
formed by the disintegration of protostellar systems.We aim to explore the
morphology, kinematics,and energetics of the DR21 Main outflow, and compare
those properties to confirmed explosive outflows to unravel the underlying
driving mechanism behind DR21. Line and continuum emission are studied at a
wavelength of 3.6\,mm with IRAM 30 m and NOEMA telescopes as part of the Cygnus
Allscale Survey of Chemistry and Dynamical Environments (CASCADE) program. The
spectra include ($J= 1-0$) transitions of HCO$^+$, HCN, HNC, N$_2$H$^+$,
H$_2$CO, CCH tracing different temperature and density regimes of the
outflowing gas at high-velocity resolution ($\sim$ 0.8 km s$^{-1}$). The map
encompasses the entire DR21 Main outflow and covers all spatial scales down to
a resolution of ~3" ($\sim$ 0.02 pc). Integrated intensity maps of the HCO$^+$
emission reveal a strongly collimated bipolar outflow with significant overlap
of the blue- and red-shifted emission. The opening angles of both outflow lobes
decrease with velocity, from $\sim80$ to 20$^{\circ}$ for the velocity range
from 5 to 45 km s$^{-1}$ relative to the source velocity. No evidence is found
for the presence of elongated, "filament-like" structures expected in explosive
outflows. N$_2$H$^+$ emission near the western outflow lobe reveals the
presence of a dense molecular structure which appears to be interacting with
the DR21 Main outflow. The overall morphology as well as the detailed
kinematics of the DR21 Main outflow is more consistent with that of a typical
bipolar outflow instead of an explosive counterpart.
