  We construct a covariant description of non-critical superstrings in even
dimensions. We construct explicitly supersymmetric hybrid type variables in a
linear dilaton background, and study an underlying N=2 twisted superconformal
algebra structure. We find similarities between non-critical superstrings in
2n+2 dimensions and critical superstrings compactified on CY_(4-n) manifolds.
We study the spectrum of the non-critical strings, and in particular the
Ramond-Ramond massless fields. We use the supersymmetric variables to construct
the non-critical superstrings sigma-model action in curved target space
backgrounds with coupling to the Ramond-Ramond fields. We consider as an
example non-critical type IIA strings on AdS_2 background with Ramond-Ramond
2-form flux.
