In the early 2000s, Bristol Spaceplanes Limited was an unsuccessful entrant in the Ansari X-Prize competition to be the first private crewed spaceflight vehicle to launch and relaunch in a week, losing out to Mojave Aerospace Ventures' Tier One combo of SpaceShipOne and WhiteKnightOne.

[4][5][needs update] In late 2014, the company was conducting bench testing of rocket engine designs for Ascender and is seeking funding to build a working model via crowdfunding.

[7][8][9] Ascender is a proposed small two-seater suborbital horizontal-takeoff, horizontal-landing (HTHL), jet- and rocket-powered spaceplane concept which is designed to be able to achieve altitudes of up to 100 kilometres (62 mi) via a steep sub-orbital trajectory.

[10] The Spacecab spaceplane design concept consists of a large crewed "carrier" aircraft with a smaller "orbiter" attached on top, both of which are derived from Ascender.

Despite requiring a new Ramjet design and significant developments with the heatshield, rocket engines, hydrogen fuel system, and transparencies, Spacebus is still claimed to be more feasible than other ongoing spaceplane projects.