We introduce affine Stanley symmetric functions for the special orthogonal groups,
a class of symmetric functions that model the cohomology of the affine Grassmannian,
continuing the work of Lam and Lam, Schilling, and Shimozono on the special linear and
symplectic groups, respectively. For the odd orthogonal groups, a Hopf-algebra isomorphism
is given, identifying (co)homology Schubert classes with symmetric functions. For the even
orthogonal groups, we conjecture an approximate model of (co)homology via symmetric
functions. In the process, we develop type B and type D non-commutative k-Schur functions
as elements of the nilCoxeter algebra that model homology of the affine Grassmannian.
Additionally, Pieri rules for multiplication by special Schubert classes in homology are
given in both cases. Finally, we present a type-free interpretation of Pieri factors, used
in the definition of noncommutative k-Schur functions or affine Stanley symmetric functions
for any classical type.