test flight of a part of the system capabilities as early as 2023. Relativity Space, with their Terran R beginning development by 2021, is aiming to make an initial orbital launch test by 2024. Blue Origin, with Project Jarvis, began development work by early 2021, but has announced no date for testing, nor even been public with their plans. Stoke Space is also developing a rocket which is planned to be reusable. Earlier plans to run tests of enhanced reusability on the second stage of the SpaceX Falcon 9 were set aside in 2018. Partially reusable launch systems Partial reusable launch systems, in the form of multiple stage to orbit systems have been so far the only reusable configurations in use. Liftoff stages Existing reusable launch systems use rocket-propelled vertical liftoff. Other than that a range of non-rocket liftoff systems have been proposed and explored over time as reusable systems for liftoff, from balloons to space elevators. Existing examples are systems which employ winged horizontal jet-engine powered liftoff. Such aircraft can air launch expendable rockets and can because of that be considered partially reusable systems if the aircraft is thought of as the first stage of the launch vehicle. An example of this configuration is the Orbital Sciences Pegasus. For suborbital flight the SpaceShipTwo uses for liftoff a carrier plane, its mothership the Scaled Composites White Knight Two. Orbital insertion stages So far, launch systems achieve orbital insertion with multistaged rockets, particularly with the second and third stages. Only the Space Shuttle has achieved a partial reuse of the orbital insertion stage, by using the engines of its orbiter. Reusable orbiter Launch systems can be combined with reusable orbiters. The Space Shuttle orbiter, SpaceShipTwo, Dawn Mk-II Aurora, and the under-development Indian RLV-TD are examples for a reusable space vehicle (a spaceplane) as well as a part of its launch system. More contemporarily the Falcon 9 launch system has carried reusable vehicles such as the Dragon 2 and X-37, transporting two reusable vehicles at the same time. Contemporary reusable orbital vehicles include the X-37, the Dream Chaser, the Dragon 2, the Indian RLV-TD and the upcoming European Space Rider (successor to the IXV). As with launch vehicles, all pure spacecraft during the early decades of human capacity to achieve spaceflight were designed to be single-use items. This was true both for satellites and space probes intended to be left in space