 Teller proposed scheme after scheme, but Bethe rejected each one.The fusion idea was set aside to concentrate on producing fission bombs.Teller also raised the speculative possibility that an atomic bomb might "ignite" the atmosphere because of a hypothetical fusion reaction of nitrogen nuclei, but Bethe calculated that this could not happen, and a report co-authored with Teller showed that "no self-propagating chain of nuclear reactions is likely to be started".