The Structure of a Series: Robert Heinlein

(i) Four stories about near future technological advances on Earth:
a "baronovitameter" or (in another edition) a "chronovitameter," for measuring the length of a life;
solar power;
moving roads;
a dangerous nuclear power plant that will be placed in orbit.

(ii) Four stories about early Earth-Moon travel:
the financing of the first Moon landing;
the construction of Space Station One;
regularized Earth-Moon travel;
old Harriman, "the Man who sold the Moon," makes it to the Moon.

(iii) Four stories about regular life on the Moon:
the Space Patrol honors a hero;
an accident;
a lost child;
a Moon-dwelling couple return to Earth but realize that they belong on the Moon.

(iv) Three stories added later about life on the Moon:
low gravity sport and romance;
a second lost child;
lost Boy Scouts.

(v) Four stories about interplanetary travel beyond the Moon:
Rhysling and others cross the Solar System, colonizing Mars and Venus;
a spaceman who knows Martians overcomes his fear of falling;
representatives of several intelligent species meet on Earth;
colonists are enslaved on Venus but a Prophet rises on Earth...(he will establish a theocracy between stories).

(vi) One novel and two stories about an interruption to space travel:
life under the Prophets and the anti-Prophetic Revolution;
after the Revolution, anti-social individualists, surviving followers of the Prophet and advocates of a strong state are sent to the ungoverned area, Coventry, beyond the Barrier;
also after the Revolution, space travel is resumed and asteroids are moved to orbits between Earth and Mars where they are adapted as space stations for refueling and rescue.

(vii) One novel and two stories involving interstellar travel:
a crisis in the Covenant leads to an interstellar round trip;
some members of the crew of the lost first interstellar spaceship learn that their large enclosed ship is not the entire universe;
some crew members escape from the ship.

(viii) Six "stories-to-told" that were never written although their proposed content informed the background of the series:
the Antarctican revolution;
resistance movements on Mars and Venus;
the First Prophet's early days;
early resistance to Prophetic rule;
a work to be called "Da Capo" that would have been set centuries later.

(ix) A Time Chart listing stories, characters, events, technologies and social backgrounds. 

That is it. Any works added later are no good. Several other works are closely related, even referring to common characters and alien races, but they do not fit into this linear sequence. Given that the Future History was never going to comprise the entirety of Heinlein's science fiction (sf) output, the question becomes: did he successfully organize part of that output into a coherent history? Yes. The integrity of the series is not compromised by the existence of closely related works that are not fully consistent with the History. In fact, several of his juvenile novels almost form a divergent though parallel history. A short story about Dahlquist, the Patrol hero, and one about Rhysling, the Blind Singer of the Spaceways, are in the Future History. A juvenile novel that refers to Dahlquist and another that quotes Rhysling's songs are not in the History. But the History as a series remains substantial.

 

Because of Heinlein's attention to technical details, the series takes six stories to reach the common sf starting point of regular space travel and even then only between Earth and Moon. The original series, collected in five volumes, comprised four groups of four stories, then two novels each followed by two shorter pieces: (4 x 4) + (3 x 2) = 16 + 6 = 22 items. The pre-Prophetic stories, about ordinary people in a common future setting, do not present a political history and therefore might not seem to comprise a future history series but they are seen to be substantial when read or re-read individually. Politics is in the background:

there is a transport strike and attempted revolution in the moving roads story;
Harriman describes Communism as "still a menace," though only to manipulate the media - he argues that a sovereign Lunar state established by private enterprise is preferable to a Lunar Soviet aiming nuclear warheads at Earth (the latter gives him nightmares...);
the UN cancels space flights that would pass too close to its orbiting nuclear weapons;
Dahlquist prevents a nuclear strike and military coup by fellow officers in the peace-keeping Patrol;
later, a planetary government convenes the multi-species conference - national legislatures like the British Parliament still exist but the confederation treaty recognizes the planetary government as sovereign.

Private investment opened space ("The Man Who Sold The Moon") and imperialist exploitation developed Venus ("Logic of Empire"). Thus, Harriman's idealism and entrepreneurship eventually led to indentured servitude. Heinlein's Future History Time Chart says that Antarctican, American and Venerian revolutions ended interplanetary imperialism. The stories show only some of the details. Free men organize on Venus. Later, the US is a theocracy. Later again, that theocracy which, according to the Time Chart, began with a US "revolution," is overthrown by the more appropriately named Second American Revolution.

The Prophets' followers, the "Angels of the Lord," must be derived from Christianity although this is not confirmed. Terminologically, they combine Christianity with Islam -

Christianity: God Incarnate;
Islam: the Prophet;
Angels: the Prophet Incarnate.

Like some Muslims, the Angels reject Church-State separation. Medieval Christendom had a Pope and an Emperor (in England, a King and an Archbishop), and conflict between them, whereas, after the election of President Scudder, the United States has only a reigning Prophet. Heinlein's other nasty Christian derivative is the Fosterite Church of the New Revelation in Stranger in a Strange Land. Both Angels and Fosterites claim direct contact with Heaven. Archangels tell the Fosterite Supreme Bishop exactly when a couple who have left their property to the Church will go to Heaven and the Church organizes a farewell party... None dare call it murder. The First Prophet is said to return in the flesh annually at the Miracle of the Incarnation. Heinlein knew that modern communications technology could be used to broadcast nonsense. We, the readers, meet neither the hedonist Foster nor the ascetic Scudder in person - but we know that Scudder's successors do not adhere to his asceticism. The revolutionary Cabal cannot take the deposed Prophet alive because his Virgins get to him first.

  

Some stories are stepping stones to later works. Escape velocity rocket fuel is developed at the end of the fourth story, "Blow-ups Happen," about nuclear power. Harriman puts a man on the Moon in the fifth story, "The Man Who Sold The Moon." A space station, necessary for regular flight between Earth and Moon, is constructed in the sixth story, "Delilah and the Space-Rigger." The seventeenth story, "The Green Hills of Earth," about Rhysling, the Blind Singer of the Spaceways, bridges the gap between passages referring only to Luna City and those also referring to colonies on Mars and Venus. Rhysling, blinded by radiation while exploring the asteroids, had regularly flown between Earth and the Moon before joining the first deep space trip, to Mars. He later visited Venusburg and wrote songs that are sung, in the eighteenth story, "Logic of Empire," by indentured men who relax in Venusburg. That story ends with a reference to the political preacher, Nehemiah Scudder, and the next work, "If This Goes On -," begins with its narrator guarding the apartments of the Prophet Incarnate. Technological, economic and social changes have at last generated a religious/political upheaval. Questions about government have moved from the background to the foreground of the series.

"If This Goes On -" refers back to a World War III, an important event not mentioned in the Time Chart, but also refers to the Federation, the UN-derived planetary government dating from the first interplanetary period which prevents wars by monopolizing nuclear weapons. When the Angels are overthrown, Heinlein conveys revolutionary turmoil: argument in the constitutional convention; the Onward Christian Soldiers' resentment of the timing of the Cabal's insurrection. The Prophets had seceded from the Federation. The latter does not immediately recognize the new regime and will not authorize nuclear weapons to end a civil war. Thus, in a few background-establishing sentences, Heinlein contextualizes the Second American Revolution. The UN had established the Patrol and become the Federation which will oppress the Families (see below) but will, according to the Time Chart, be succeeded by a mature culture.

  

After the madness of the Prophets, a sane society is built but its peace is threatened by mass envy of the Howard Families' longevity. Obliged to lead his persecuted fellow Howards out of the Solar System, Lazarus Long unintentionally provides a further fulfillment for Harriman's dream of space travel. When, after difficult experiences in two inhabited systems, the Howards discuss whether to return to the Solar System, Lazarus has Rhysling's song, "The Green Hills of Earth," played over the PA.

The Future History could be packaged in five sections not exactly corresponding to the original five volumes.

Earth: six stories set on Earth or in Earth orbit ("The Man Who Sold the Moon" is set entirely on Earth although the first Moon landing, in 1978, occurs off-stage).
Moon: six stories in the original History plus two more added in The Past Thru Tomorrow plus one more added in Expanded Universe.
Interplanetary: four stories plus possibly "Tenderfoot in Space," which I have not read, if it is set on the same version of Venus.
Interregnum: the Prophets, revolution and after.
Interstellar: the rest.

  

Appropriate volume titles for such a repackaging would be:

The Man Who Sold The Moon;
The Black Pits of Luna;
The Green Hills of Earth;
Revolt in 2100;
Orphans of the Sky.

This involves swapping two stories between collections, then splitting one volume and amalgamating two of the original five. The Moon story, "The Black Pits of Luna," is, as far as titles go, a companion piece to "The Green Hills of Earth." Rhysling's song refers to "...harsh bright soil of Luna..." The song as a whole refers not to a life spent on Earth but to spacemen's nostalgia for "...the globe that gave us birth...," as they travel beyond the Moon and further into the Solar System.

Revolt in 2100 remains unchanged in the proposed repackaging. The original Orphans of the Sky collected the two stories set in an interstellar spaceship whose crew are "orphans" because they are lost, having forgotten even where they came from. However, the title characters of Methuselah's Children, the Howards, become "orphans" when they flee from the Solar System. Therefore, Orphans... would be an appropriate title for a collection of all three works that would be a culmination of the History.

Pivotal characters in the series as a whole are:

Harriman who sold the Moon;
Dahlquist who defended freedom;
Rhysling, the "Blind Singer" who was on the first trip to Mars;
Scudder who destroyed freedom for three generations;
Novak of the Covenant;
Long who freed the Howards.

It is difficult to finalize this text because a wealth of details deserves to be mentioned. Heinlein's Preface said that this fictional history was at least as real to him as Plymouth Rock. This is true for many of his readers. 

        

The early part of a future history can set the scene for later action:

Wells analyzed then current world affairs before moving into the future (he had described a first Moon landing in a separate work);

Niven's Known Space series begins with four stories of interplanetary exploration;

Anderson's Technic History begins with one story of interplanetary exploration and one of interstellar exploration;

Blish's Cities in Flight begins with regular interplanetary travel, then describes the two discoveries that make interstellar travel possible.

All sf writers are indebted to Wells. Blish, Anderson, Niven and others are also indebted to Heinlein, particularly for his Future History.