Migration, most commentators agree, is a major issue shaping politics, if not at a Scottish level then certainly in terms of the forthcoming elections to the UK parliament.

The growth of a far right, populist party, in the increasingly unpleasant shape of Ukip, is driven to a considerable extent by the demonisation of "economic migrants".

What if the distinction between economic migrants (bad) and refugees (good, or at least tolerable) is a false one? What if, in a world in which millions of people are in transit in their attempts to shelter themselves and their families from conflict or poverty, most migrants should be considered brave pioneers, risking their lives in journeys into the unknown?

These are the questions posed by Last Dream (On Earth), the latest work to be presented by the National Theatre of Scotland. Created by stage designer-turned-theatre maker Kai Fischer, the piece draws a fascinating parallel between a modern-day journey of migrants leaving North Africa for Europe and the famous mission which made Yuri Gagarin the first human being to travel into outer-space in 1961.

"Personally, I don't make the distinction between a refugee and a migrant," explains Fischer, who, in researching for his piece, travelled to the Italian island of Lampedusa and Malta, both destinations for many migrants trying to reach the European mainland.

"It seems almost impossible to define where an economic need stops, and where it becomes a need to survive," he continues. "In terms of a lot of the people I spoke to, their journeys started out with one purpose, which then turned into another. People who came from, say, Eritrea, Ethiopia or Cameroon initially made it to Libya to work. Then the situation in Libya turned extreme, and they became refugees halfway through their journeys."

Whether migrants' often perilous and - as we see with heartbreaking regularity in the Mediterranean - sometimes fatal journeys are motivated by fear of persecution or hunger, or a combination of the two, they have, Fischer suggests, something fundamental in common with Gagarin's great voyage.

"Both journeys are driven by circumstance," he says. "In the case of migrants, often people travel because other people want them to. Sometimes families even decide who will go, choosing the person they think has the best chance of success. I think it was the same for Gagarin. It was a mission for a nation. The space race was going on, and he represented the hope of building a society that people could believe in."

The production, in which audience members will wear headsets, as Gagarin did in his spacecraft, combines audio work, live music and stage performance. Just how it interweaves the experiences of the most famous cosmonaut and the many migrants currently traversing our blighted planet is, says Fischer, ultimately down to the theatregoer. In engaging with the piece, it is, appropriately enough, the individual audience member who completes the journey.

Last Dream (On Earth) opens at the Tron Theatre, Glasgow, April 1-4, and then tours until April 18. For details, visit www.nationaltheatrescotland.com