(This is not a crossover with Dune, nor an AU of it, just a setting which includes a substance with similar properties to the Spice melange, in a world where the first two Dune books have already been published.)
In 1973, on Skylab, an experiment that was not performed in our timeline took place. This produced a powder of tiny organic crystals, which had a very strange effect on any vaguely-intelligent lifeform (at least as smart as most lizards and many fish) that consumed them: The creature would exhibit psychic powers of some description, though which power varies from user to user, and not all are particularly obvious. While under the influence of this substance, users often have difficulty focusing on anything not related to psionics or abstract reasoning, though they consistently focus
better on those. When the effect fades, the users lose any drug-induced absent-mindedness, and tend to retain a faint echo of the power gained, which can be strengthened by subsequent doses, until the full ability becomes available without the use of this substance. How long this takes is highly variable, but it generally takes months unless the user is being highly incautious and/or the ability is a fairly weak one. This is also hampered by the fact that a user will not necessarily gain the same ability or abilities every time, though the abilities they do gain tend to be related (the scientists conclude that different people and creatures are talented in different areas of psionics). The substance is also highly addictive, and the addiction is marked by a change in the appearance of the eyes: medium-blue irises with sky-blue sclera. This makes the onset of addiction easy to spot, as the change in colour is gradual, but also makes secrecy somewhat tricky to maintain. Due to these factors, it was almost inevitable that the well-read (and nerdy) scientists working on it would name this substance 'the Spice Melange,' or PROJECT MELANGE in official reports.
The military, CIA, and others who became aware of the Spice took great interest in it, and more batches were ordered to be produced on the second Skylab expedition, once it was determined that the Spice could not be produced in Earth's gravity. Before the third Skylab mission went up, two unusual satellites were launched (and a third while the astronauts were on the station), which were intended to produce the Spice in orbit, without the cost of manned missions. Both failed, which presented a serious problem: no more Apollo capsules were being built (they were too expensive for the job of ferrying people and things around in Earth orbit), and getting Congress to authorize the funds would require telling them why, and the more people who knew the secret, the greater the chance of a leak. Worse, the Space Shuttle would not be available for years yet, and while the military could transfer some of their budgets to NASA in the name of National Security, there were limits to how much they could get away with.
After much debate (and careful examination of several influential senators and representative by CIA telepaths and ESPers using some of the small quantities of Spice they already had), it was decided to reactivate the Gemini program as a placeholder between Apollo and the Shuttle, and to include an order for some version of the planned
Big Gemini spacecraft, as well as other variants. The budget would be shared primarily between NASA and the US Air Force, though the US Army, and US Navy would also contribute. No matter what, the Spice Must Flow.
<The Spice is a psi drug that must be produced in microgravity, by sapient beings. It serves as a cross between Mind Hype (Psi-Tech p34) and a variant form of Catalyst Drug (pp33-34). After each use, the user may spend one unused character point (if available) on an ability gained during that use, or the skill or techniques thereof. The Spice is very expensive, highly addictive, and tightly controlled, so an addiction to it costs [-25], on top of the Unnatural Feature [-2] of blue-on-blue eyes. Any creature with IQ 3 or higher gains psi abilities from using the Spice. Creatures in-setting generally have either Psi Talents (often balanced by psi-related disadvantages), Psi Perks (generally from only one or two powers), and/or Features that could be described as 'level 0 Psi Talents.' Full-on psi abilities without any form of catalyst appear to be very rare.>