Cylindrical detonations propagating in free space characterized by different activation energies were cornputationally studied. It is found that unstable detonations with the 2-D cellular structure have more velocity deficit than those without the cellular structure computed with the 1-D simulation. The weakening is due to lengthening of the detonation structure and the unreacted pocket behind the cylindrical front, while propagation sustenance depends strongly on the re-amplification and regeneration of transverse shocks and triple points. For low activation energies, cellular detonation can be initiated in free space through the subcritical initiation path due to absence of unreacted pockets, and the propagation is not very sensitive to the attenuation of transverse waves and triple points. However, for high activation energy the unreacted pocket aggravates initiation such that even a cellular detonation first established is prone to quench due to the lack of re-amplification of the transverse wave and the triple point. When considering confinement, it is demonstrated that a detonation that quenches in free space can be reinitiated in confined space. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.