However, financing for the initiative was not forthcoming from the British government and the concept ultimately languished following the completion of the last major design study in early 1967.
[5] While the ambitions of these programmes had been tempered both by cost and a political desire to collaborate with other Commonwealth and Western nations, such as the Europa launcher, Britain retained a considerable interest in the pursuit of various space-related technologies.
that from an early stage, BAC's space-related research was being influenced by foreign space programmes, most significant of these being the United States; reportedly, the company engaged in detailed studies of various transatlantic projects and proposals.
[1] However, Smith acknowledges that in order to have continued the project through to the manufacturing stage, several billion pounds of investment would have been required, the financing of which was neither budgeted nor planned for by any entity.
Writing for the scientific periodical New Scientist, author Nigel Henbest commented that it was unlikely that Britain could pursue the development of Mustard alone, but also suggested that there was potential value for the platform if organised as a multinational European venture, similar to the conventional Europa and Ariane launchers.
Accordingly, a number of key Mustard project staff had spent the first two years of the 1970s overseas at North American Rockwell, where they contributed to the initial study which would eventually lead to the US Space Shuttle.
Around this time, the prospect of collaboration is said to have faded and, in the absence of significant interest from the British government, the Mustard project was effectively terminated.
[1] Mustard was a modular reusable space launch system, comprising multiple copies of a single vehicle design, each of which was configured for a different role as a booster stage or an orbital spaceplane.
[1] Due to the relatively low re-entry speed anticipated, it was believed that complex heat-resistant tiling could be dispensed with in favour of simpler and cheaper nickel-alloy panelling across the vehicle's underside.
According to Smith, the orbiting vehicle would have been capable of performing between 30 and 50 launches before needing to be replaced, while the booster engines, which wouldn't have been subject to as much heat and stress, would have remained usable for up to 200 times.
[1] The spacecraft would place its payload into orbit at around 1,000 nautical miles, which would be achieved roughly 10 minutes after launch, and then return to Earth via a controlled gliding descent before conducting a landing in a similar fashion to the booster units.