Earthsearch: A Ten-Part Adventure Serial in Time and Space is a British science fiction radio series written by James Follett.

Other cast (across the series): Three crew-generations previously, the starship Challenger - a vast ten-mile-long survey vessel – was launched from Earth on an interstellar mission to search the universe for an Earth-type planet to colonise.

From infancy, the four third-generation crew members (now in their early twenties) have been raised by robots and by the Angels – mysterious unseen beings who run the ship and who only manifest as disembodied voices.

Unrevealed to the crew, the Angels (who are the ship's control computers; their name being an acronym of ANcillary Guardian of Environment and Life ) have their own agenda.

This situation is changed when Darv and Astra enter an uncontrolled zone within the Challenger and locate a space shuttle previously unknown to the Angels.

Opting to work in the ship's farm galleries for a while, Darv develops a taste for unprocessed fruit, and the hormone suppressants which keep him sexually undeveloped begin to wear off.

Their stories of the past of Earth and their mission are considered a threat to the position of the Solaric Emperor Thorden, who is persuaded by his ruthless chief prosecutor, Helan, to have them executed.

He plans for his own security and future dominance over the mission by ensuring that the space ferry which he brings to and docks within the Challenger as personal transport is heavily armed.

Sharna and Telson go over in the shuttle to investigate, and discover that the Challenger II is still populated by the descendants of its original crew but has been crippled by civil wars between them.

While welcoming, the female-dominated Underpeople have chosen to stabilise their society by keeping their men almost permanently in suspended animation, reviving them only temporarily to serve as sperm sources for impregnation.

Abandoning the too slow shuttle, the crew carries out a harrowing pursuit in the ferry, constantly trying to produce enough velocity to cut down on a fatal time and oxygen shortfall.

Wishing to maintain control of a future crew – and already wary of the rebellious Darv – the Angels plan to deliver Astra's baby secretly.

However the Angels block the Challenger's controls, and attempt to change the crew's minds by admitting to the existence of Paradise but also overstating its difficulties, for example the electromagnetic radiation that lights up the polar sky.

Unhindered by the Angels, Telson and Sharna follow Astra and Darv to settle on Paradise, successfully landing on the planet with appropriate supplies and resources to begin their colony.

While the Angels departed Paradise orbit to continue the Earthsearch mission (and to achieve their aim of dominating an entire civilisation), the humans began their new life on their new homeworld.

Earthsearch 2 begins four years later, when Telson, Sharna, Darv and Astra have settled into their life on Paradise (assisted by two androids, the agricultural machine George and the argumentative general-purpose service unit Tidy).

Sharna's loss of what would have been her second child raises questions about the sustainability of the small colony as well as bringing up differences of opinion on how (and whether) to use the remaining technology and resources (including their surviving planetary shuttle).

Noticing the appearance of an unidentified artefact in planetary orbit, Telson and Darv fly up towards it in the shuttle, to discover that it is an eight-mile long spaceship called Voyager 30 and apparently part of an Earth-originated survey mission.

The Angels are now being attacked by mysterious transmissions apparently aimed at damaging or destroying organic computers such as themselves and the Challenger's higher intelligence androids.

When rejected by the suspicious humans, the Angels resort to sabotage on a planetary scale, using terraforming equipment from the Challenger to melt Paradise's polar ice caps and thus raise the sea level in an attempt to get their former crew to rejoin them on the ship.

They make the best of things by demanding a concession in the shape of a reversal of the flood (so that the animals can be released and survive), following which they fly their shuttle up to the Challenger.

En route to the source system of the attacks, the Challenger encounters a free-floating fifty-mile wide parabolic dish which the Angels decide to use as raw material for shielding.

Attempts to escape from the black hole are hampered by the fact that the human crew have no access to the Challenger's control room, where Android Surgeon-General Kraken has had his reasoning capacity damaged by the continuing attacks and is no longer responding to or obeying instructions.

With the Angels drastically weakened by the attacks and unable to assist, the humans attempt to storm the control room, which is defended by android warriors.

They discover that they have in fact landed unharmed on an enormous artificial construct - a "gravity platform" which merely resembles a black hole and forms part of Earth's long-range defences, acting as a trap for potentially hostile vessels.

With the inexperienced and insecure Bran unable to cope (and undermined by Elka, who secretly dominates him and dictates his actions at the prompting of the Angels), Telson regains command of the Challenger and succeeds in organising the crew to deal with the problems.

They discover that the Earth's civilisation has collapsed a long time ago, and the human race is reduced to eking out a meagre living from a tiny spring that grows weaker every year.

Unfortunately, Earthvoice's abilities do not include weather control, so although he has successfully defended Earth's legacy of knowledge he has been helpless to deal with the deterioration of the planet's environmental conditions.

This episode (also penned by Follett and first broadcast on BBC Television on 28 January 1980) features an artificial black hole which draws in the Liberator and in which the crew wake up surrounded by captured ships.

The plot of the first series is also somewhat similar to the Space:1999 episode "Mission of the Darians", in which the Alphans discover an enormous spacecraft whose inhabitants have descended into barbarism after an environmental disaster on board the spaceship.