  We study the Bondi-Sachs rockets with nonzero cosmological constant. We
observe that the acceleration of the systems arises naturally in the asymptotic
symmetries of (anti-) de Sitter spacetimes. Assuming the validity of the
concepts of energy and mass previously introduced in asymptotically flat
spacetimes, we find that the emission of pure radiation energy balances the
loss of the Bondi mass in certain special families of the Bondi-Sachs rockets,
so in these there is no gravitational radiation.
