Hopper was a proposed European Space Agency (ESA) orbital spaceplane and reusable launch vehicle. The Hopper was a FESTIP (Future European Space Transportation Investigations Programme) system study design.
Hopper was one of several proposals for a reusable launch vehicle (RLV) developed by the ESA. The proposed reusable launch vehicles were to be used for the inexpensive delivery of satellite payloads into orbit as early as 2015. A prototype of Hopper, known as (EADS) Phoenix, was a German-led European project which involved the construction and testing of a one-seventh scale model of the proposed Hopper. On 8 May 2004, a single test flight of the Phoenix was conducted at the North European Aerospace Test range in Kiruna, Sweden, which was followed by more tests later that month.
Development
Background
From the 1980s onwards, there was growing international interest in the development of reusable spacecraft; at the time, only the superpowers of the era, the Soviet Union and the United States, had developed this capability. During the 1990s, in addition to the development and operation of several technology demonstrator programs, such as the Atmospheric Reentry Demonstrator (ARD), the ESA were also working on the production of a long-term framework for the eventual development of a viable reusable spacecraft, known as the Future Launchers Preparatory Programme (FLPP).
Under FLPP, the ESA and European industrial partners performed detailed investigations of several partially-reusable launch vehicle concepts; the aim of the program was to prepare a suitable vehicle to, upon a favorable decision by the ESA's member-nations, proceed with the production of a Next Generation Launcher (NGL). Studies determined that both the HTO and the VTO variant concepts possessed a relatively similar reentry load environment.
HTO Hopper - Selection
The HTO Hopper was adopted for further development work under another ESA initiative in the form of the FESTIP (Future European Space Transportation Investigations Programme) system design study. to be developed and produced as a portion of the wider ASTRA program of the German Aerospace Center (DLR), a project founded by the German Federal Government, EADS' Astrium subsidiary and the state of Bremen. Reportedly, EADS and the state of Bremen invested at least €8.2 million and €4.3 million respectively in the ASTRA programme. A further contribution of €16 million was sourced from partner companies on the program, such as the Bremen-based OHB-System, the DLR and the Federal Ministry for Education and Research. Construction of the prototype began in 2000.
The Phoenix RLV was long, had a weight of , and a wingspan of . During its design, an emphasis had been placed on minimizing drag by making the vehicle as small as possible. The final version of the vehicle was expected to be able to support the reentry forces and heat, and be able to glide from an altitude of . Integration and system testing works were completed in April 2004.
Longer term - Socrates
In the long term, if successful and viable, the landing technology tested on Phoenix was to be incorporated into a follow-on re-usable vehicle, which was to be named Socrates. While not envisioned to serve as an orbital vehicle, Socrates was to be capable of flying at up to 10 times the speed of sound, as well as of performing very rapid turnaround times between flights as a steppingstone towards re-usability.