Overview of reusable space systems with a look to technology aspects

Rocket reusability dates as long as rockets. Since the beginning of space age, the possibility to reuse the full vehicle or some stages has been a matter of engineering. But this was directly opposite to mass ratio efficiency, the key for a well-designed rocket. Since as soon as a stage has to be recovered, subsystems to provide this function and additional inert mass are needed. Even if reusable systems are only a small part of the worldwide rockets, they flew operationally since the space shuttle age. However, full reusable vehicles are not yet operational and only partially reusable launch vehicles have been flown until now. The preliminary space shuttle design consisted of two stages both liquid and reusable (booster and orbiter stages). The consolidated design retrieved the orbiter (upper stage, the cargo and propulsion bay) and the solid rocket boosters. On Russian side Energia-Buran only retrieved the upper stage with its cargo bay and the same approach was adapted for the original design of Ariane 5-Hermes. Europe investigated and developed different reusable systems, set up test facilities and flew the IXV demonstrator in 2015. More recently, the preferred strategy consists in reuse of unwinged booster stages (e.g. Falcon 9 of SpaceX) or of only the orbited spacecraft (e.g. NASA-USAF X-37). France and Europe are preparing propulsion and reusable rocket stage demonstration bricks for next generation launchers. The purpose of this paper is to provide an overview of some reusable space systems with emphasis on the different design strategy and skills mainly focused on European heritage. The systems are split into low and high energy with a view to technology aspects and in-flight experiments. •Reuse of space vehicles skills and technology are outlined depending on the energy level of the vehicle.•In-flight experiments learning is examined as a basis for preparation of future programs.•Examples of technology maturation and testing approach are given on the basis of European and worldwide testing heritage. Capsules have been widely used since the early space age. A number of capsules is currently operational or next to be operational, such as Soyuz, Shenzhou (and the next generation crew vehicle - NGCV), Orion, CST-100, Dragon-2 and a lot owns to the past, such as Vostok, Mercury, Gemini, and Apollo.