  When a high dimension system of ordinary differential equations is solved
numerically, the computer memory capacity may be compromised. Thus, for such
systems, it is important to incorporate low memory usage to some other
properties of the scheme. In the context of strong stability preserving (SSP)
schemes, some low-storage methods have been considered in the literature. In
this paper we study 5-stage third order 2N* low-storage SSP explicit
Runge-Kutta schemes. These are SSP schemes that can be implemented with 2N
memory registers, where N is the dimension of the problem, and retain the
previous time step approximation. This last property is crucial for a variable
step size implementation of the scheme. In this paper, first we show that the
optimal SSP methods cannot be implemented with 2N* memory registers. Next, two
non-optimal SSP 2N* low-storage methods are constructed; although their SSP
coefficients are not optimal, they achieve some other interesting properties.
Finally, we show some numerical experiments.
