Bondi-Sachs metrics and Photon Rockets
  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. 
Huabin Ge, Mingxing Luo, Qiping Su, Ding Wang, Xiao Zhang
gr-qc hep-th math.DG