 It can also be necessary to be able to ignite engines in a variety of conditions potentially including vacuum, hypersonic, supersonic, transonic, and subsonic.The additional weight of fuel, larger tank, landing legs and their deployment mechanisms will usually reduce the performance of a soft landing system compared to expendable vehicles, all other things being equal.The main benefit of the technology is seen in the potential for substantial reductions in space flight costs as a result of being able to reuse rockets after successful VTVL landings.