The hydrodynamic equations describing the average behavior of a one‐dimensionally expanding plasma heated by laser radiation are solved analytically. For the small parameter approximation, the hydrodynamic expansion depends on the parameter(16P/9Ml02)1/3&tgr;L, wherePis the laser power,Mis the plasma mass,l0is the initial plasma length, and &tgr;Lis the laser pulse duration. With &tgr;L=&tgr;ei, the electron ion relaxation time, it is possible to compute&phgr;max (≈5.6×10−6n04l03miT−9/2, wheremiis the plasma ion mass andTis the temperature), the maximum flux density below which the hydrodynamic expansion may be neglected. We find that a 5‐kJ 75‐nsneodymiumglass laser is capable of acheiving break‐even conditions for a 50% mixture of deuterium‐tritium gas.