  Shell-wise orbital slotting in Low Earth Orbit (LEO) can improve space
safety, simplify space traffic coordination and management, and optimize
orbital capacity. This paper describes two methods to generate 2D Lattice
Flower Constellations (2D-LFCs) that are defined with respect to either an
arbitrary degree or an arbitrary degree and order Earth geopotential. By
generating shells that are quasi-periodic and frozen with respect to the Earth
geopotential, it is possible to safely stack shells with vertical separation
distances smaller than the osculating variation in semi-major axis of each
shell or a corresponding Keplerian 2D-LFC propagated under an aspherical
geopotential. This helps mitigate the single inclination per shell requirement
in prior work by admitting more shells for a given orbital volume while
retaining self-safe phasing in each shell. These methods exploit previous work
on the Time Distribution Constellation formulation and designs of closed
2D-LFCs under arbitrary Earth geopotentials using repeating ground track
orbits. Factors that influence the widths and shapes of these frozen shells are
identified. Simplified formulas for estimating shell geometry and thickness are
presented. It is shown that sequencing shells to group similar or ascending
inclinations improves capacity versus arbitrary inclination ordering.
