Although Blue Streak now had no future as a missile, British scientists intensified their work to incorporate it in a Blue Streak/Black Knight satellite-launch vehicle. The project was given the name Black Prince. The vehicle would comprise an almost unchanged Blue Streak for its first stage, a slightly modified Black Knight for its second stage, and a third stage based on the Bristol Siddeley PR-38 rocket engine. Black Prince would be capable of launching two types of satellites: a 1750 lb (794 kg) satellite into a 300-mile (480 km) orbit and a 220 lb (100 kg) satellite into an elliptical orbit with a maximum altitude of 100,000 miles (160,000 km).

Doug Millard explains the relationship between Britain and France at the time of the Cold War (1:40 min)

Black Prince became a collaborative venture between three organisations--the RAE and two private firms, Saunders Roe Ltd and Bristol Siddeley Ltd. They were keen that the knowledge and expertise gained in the Blue Streak and Black Knight programmes should be redirected into a new and challenging project to launch satellites. The government also backed the scheme in as far as it would safeguard jobs, salvage some of the money invested in Blue Streak and Black Knight and maintain Britain's prowess in long-range rocket technology. But the government was less committed to the idea of a satellite-launch system. It was not convinced that a national satellite-launch programme was needed, since it would duplicate a capability that the United States was already offering to Britain. Despite the political benefits, the government remained wary of allocating further public funds to the Black Prince proposal, and instead looked for other ways to deal with the legacy of its missile programme.

Hoping to share the costs of development, the government asked France whether it would be interested in joining the Black Prince project. The response was encouraging, but France made it clear that the vehicle's second stage should be French. The British government was prepared to accept this, perhaps because ministers thought that more cooperation with European countries would aid Britain's hopes of joining the European Common Market. France remained unhappy, however, about the way the proposal allocated costs between the two countries. It also objected because Britain refused to share Blue Streak's guidance and re-entry technologies with France. Britain was unable to share this information because it was joint US/British knowledge, and the US was concerned about the spread of missile technologies internationally.

Science Museum, London/ Science & Society Picture Library

Model of the European Launcher Development Organisation's Europa vehicle, c.1964. This model, made out of polished stainless steel, accurately portrays the Europa's external design. The Europa development teams would have referred to it during their work.

Europa
Peter Thorneycroft, Britain's minister of aviation, travelled back and forth between London and Paris in an attempt to keep the Black Prince project going. But, by the end of 1960, France appeared to be losing interest in the satellite-launch vehicle proposal altogether. And then, in January 1961, the French government suddenly dropped its objections. France was now ready to come in on the joint project, and was no longer demanding access to Blue Streak's sensitive technologies. The reversal came shortly after one of Harold Macmillan's regular meetings with the French president, Charles de Gaulle. It perhaps owed something to Macmillan's close working knowledge of de Gaulle, which went back to their days of co-operation in the Second World War, and the French president's own aims for France and Europe in the 1960s.

With Britain and France now in agreement, officials held further negotiations to bring other European nations on board. These talks enabled a European Launcher Development Organisation (ELDO) to be set up. ELDO was formally established in 1964, and its main objective was to build a three-stage satellite launch vehicle called Europa. Europa's first stage would be Blue Streak, its second stage the French Coralie and its third the German Astris. Italy would build the satellites.

Blue Streak had therefore been salvaged, but as part of a pan-European project, and with no role for Black Knight. It seemed that the big opportunity to develop an all-British satellite launch vehicle, following Blue Streak's cancellation, had been missed. This however was not the end of the story.