  The discovery of transiting "super-Earths" with inflated radii and known
masses such as Kepler-11b-f, GJ 1214b and 55 Cnc e, indicates that these
exoplanets did not lose their nebula-captured hydrogen-rich, degassed or
impact-delivered protoatmospheres by atmospheric escape processes. Because
hydrodynamic blow-off of atmospheric hydrogen atoms is the most efficient
atmospheric escape process we apply a time-dependent numerical algorithm which
is able to solve the system of 1-D fluid equations for mass, momentum, and
energy conservation to investigate the criteria under which "super-Earths" with
hydrogen-dominated upper atmospheres can experience hydrodynamic expansion by
heating of the stellar XUV (soft X-rays and extreme ultraviolet) radiation and
thermal escape via blow-off. Depending on orbit location, XUV flux, heating
efficiency and the planet's mean density our results indicate that the upper
atmospheres of all "super-Earths" can expand to large distances, so that
besides of Kepler-11c all of them experience atmospheric mass-loss due to Roche
lobe overflow. The atmospheric mass-loss of the studied "super-Earths" is one
to two orders of magnitude lower compared to that of "hot Jupiters" such as HD
209458b, so that one can expect that these exoplanets cannot lose their
hydrogen-envelopes during their remaining lifetimes.
