I've googled extensively and failed to find anyone talking about the details of this, so for the record:

The outline Spider Robinson used as the basis for Variable Star is in the Heinlein Archive as part of "story ideas part 1" ().

It can be purchased for $2. The archive's description of the contents is a bit inaccurate, so let me say it contains: the Star Clock outline; 19 pages of worldbuilding for Stranger, dated 1949; two lengthy letters on race relations, one to "Sarge" (on whether or not blacks are inferior to whites), one to "Buz" (more specifically on whether outlawing racial housing discrimination is a good idea), both dating from the early-mid 60's; two articles by Jerry Pournelle (one MS, one journal reprint); some hard-to-decipher handwritten pages; and a slew of newspaper and magazine clippings that Heinlein evidently found evocative or inspirational in some way, and thus put into his story ideas file.

Be warned that some of the pages of the PDF appear to have been made from bad scans or corrupted files, making the page look blurry and very hard to read; this affects several of the Star Clock notecards, and three pages in the race relations letters. I've written the archives to ask them if anything can be done.

As far as "Star Clock" goes, there are 12 index cards and 8 typewritten pages, comprising pages 115-136 of the PDF. Evidently the missing last page that Robinson talks about in his afterword went missing from the photocopy that was given to Robinson, because the outline in the archive is complete.

Robinson stuck very closely to the first five pages of the outline, which takes us up to the point where the protagonist Joel embarks on his interstellar trip. The sixth page is brainstorming for things that will happen on the voyage, of which Robinson used very little, and he didn't use page 7 at all.

By page 7, Joel has aged 3 years and, has returned to Earth 60 years later. The top half of page 7 has Joel meet the secretary of the club for relativistic starship time travelers, where you can meet people who were born in your own era, and where you can get help learning how to deal with the vastly changed culture, language, and customs of Earth, since in the year or three you've been away, decades or centuries have passed on Earth. The second half of page 7 has Joel visiting the Conrad home, where he hopes to once again meet Jinny, the girl he ran away from, whose memory haunts him yet (so he still has not married despite numerous opportunities during his voyage), and who he imagines is now 80 years old.

On page 8, we get the big reveal that Jinny married, gave birth to the requisite Conrad heir, was widowed and orphaned very shortly thereafter, and so she went out on a starship too. Instead of being 80, she is now the same age as Joel. They fight, they make up, they "clinch," and the outline ends with them planning to buy Joel's old starship and head out again, not to make money or to explore so much as to use relativistic travel to time travel into the future; maybe they'll check back on old Earth once in a century, just to see what's changed.

The marketing for "Variable Star" implied that Heinlein's sticking the outline in a drawer was inexplicable, but I think it's reasonable to guess that once he wrote down the idea, he decided that centering the plot on a boy-girl romance was not going to pass muster in the (then very sexless) boy's juvenile market. Also, it's possible that he looked it over and decided that there were too many big ideas here to fit them all into one book. So he took the relativistic travel part of the outline and turned it into "Time For the Stars"; he reworked the "poor boy gets entangled with super ultra rich family" angle to form the last act of Citizen of the Galaxy; and finally, he took the "boy thinks he has lost girl due to time travel into the future, only to discover that she time travelled as well and is still young" business and made it the basis for "Door into Summer."

I can post a more detailed summary of the outline here if there is interest.

Count me in. That was fascinating.

Ok, I actually typed this up earlier so just pasting it in, the detailed summary:

The MS begins "Notes for a novel - 5 Nov 1955," which places it (going by publication dates) after Tunnel in the Sky and before Double Star or Time for the Stars. The second line gives a working title "The Stars are a Clock," and then there are several other titles handwritten at the top of the page:

Dr. Einstein's Clock
The Starship Nautilus
The Starship Naughty Girl
The Star Clock
The Einstein Clock

It's not clear whether the two "The Starship X" ones are meant to be subtitles for "Dr Einstein's Clock" or standalone titles in themselves. Page 2 is headed "Star Clock (The Star Clock, maybe)" and the rest of the outline has "The Star Clock-[page number]" as a running head.

The only named characters are Joel Johnston, age 18, the protagonist, Jinny Jones/aka Jennifer Conrad (Joel's steady high school girlfriend, age 17), and "Mr. Conrad," Jinny's grandfather and head of the Conrad financial empire. A few other characters are described in terms of the real-world people the character should be modeled after (eg, in speaking of the starship, he says "I think maybe Ron Hubbard is her skipper").

Page 1: Joel and Jinny are in love, but Joel is an orphan with no money and he thinks he needs to get through college and start a career before he can get married. If Joel can't get the scholarship he's applied for, then it's going to take even longer, since he'll have to work his way though school.

Having gotten Joel to admit that he would like to marry Jinny if only there was a way, Jinny lets him know that he surname is not Jones but Conrad, and that she is not just a Conrad, but the "'crown princess' of the Conrad industrial empire... which is larger than the Hanseatic League, Rothschild family, and General Motors combined and just smaller than space itself."

Two paragraphs in a row start with a variation of Joel "finally gets it through his head" that Jinny is wealthy enough to pay his way though school, so Joel is yet another variation on the "smart but slow witted youth" that Heinlein used as protagonist several times in his juveniles.

There's a couple of paragraphs mentioning the marriage and courtship customs of the time, which again probably would not have been acceptable in a novel for the juvenile market: "some discussion of 'student contract,' the trial marriage used" by most college students who wish to get married before they graduate, rejected by Jinny, ("marriage isn't a ticket to an amusement park") who wants an old fashioned life long marriage.

Jinny doesn't "park, diddle, go on no-chaperone weekends... she is old-fashioned and chinchy [sic]" because she has been taught since age three that she has a responsibility to the Conrad family to produce an heir with an acceptable father - and she has decided that Joel is that man.

Joel "finally gathers" that he has been tapped not just to marry into the Conrad family but to produce its heirs, and is dubious about being a kept man/prince consort. Jinny says "it isn't like that at all!" and makes him promise to go talk to her grandfather about it.

All this takes just over a page of the outline.

The next morning, Joel is summoned to an audience with Mr. Conrad. There is only one "Mr. Conrad" at any one time, all the other male Conrads go by "Mr. Joseph, Mr. Robert" and so on. Conrad takes Joel's consent for granted and proceeds to tell him how he will live his life from then on -- he will be educated, trained, and groomed to take a top executive position. Joel was thoroughly investigated before Jinny was given permission to propose to him. Mr. Conrad knows all about him - including confidential medical/psychological records.

Joel objects, respectfully, saying that having his life planned out for him like this is not for him. Conrad brushes his objections aside and leaves for his next appointment, still failing to realize/unable to comprehend that he's just been turned down.

Joel is unable to contact Jinny after this ("she has been gently kidnapped, of course - family stuff"), and once he fails to respond to further messages from Conrad, the screws start to turn: his scholarship (controlled by the Conrad foundation) is turned down.

Unable to continue school, sore at Jinny for not contacting him, and at his wits end, "he sees the ad for 'gentlemen adventurers'" applies, is accepted, and is shortly on his way to "Beta Aurigae."

All this takes a page and a half of outline, most of it devoted to a detailed summary of Mr. Conrad's interview with Joel.

Now there's just under two pages of background material, detailing several things:

First, the economics of space travel in this future society - relativistic starships that go out on voyages of exploration often fail to come back, but those that do return invariably show an immense profit, more than enough to pay for the lost ships. Starship exploration is one area where the Conrad empire has competitors, and the ad Joel sees is not affiliated with the Conrad conglomerate.

Second, the nature of Joel's poverty - he has an "orphan's allowance" which ran out on his 18th birthday. Joel's father bought some stock for him but the market shifted and Joel had to sell it low to pay for his last (post 18th birthday) semester at prep school. WIthout the scholarship, Joel has no money at all. He could do many things at this point, from indentured service to a stint in the military, but he's so "discombobulated" by the whole Jinny/Conrad business that he is in a "what the hell frame of mind" and signs up for this star voyage.

Third, the starship in question is "a pile of junk," old and poorly equipped, carrying low value cargo (emigrants), with low likelihood of returning, but Joel doesn't know that. "She will be a quaint mixture of madhouse and hellship." Subjectively, the trip out and back (to a star 10 light years away) will take a year, but 40 years will pass on Earth.

Fourth, there's a half page of brainstorming, with Heinlein throwing out multiple ideas as to what may happen (is the skipper incompetent, or is he in on a stock market manipulation scheme to delay the ship's return? Perhaps Joel still has some stock his father bought in an old starship that is long overdue, which he instructs his solicitor to invest in Joel's starship if it ever pays off? Perhaps they pay off, but his solicitor put them in a "safe" investment instead, and Joel is penniless - again! - at the end of his trip?)

Joel applies to go on the starship, along with a large crowd of "down-at heels rabble" and he is among the few provisionally accepted. They'd like him to marry one of the single women who have also been provisionally accepted, but he'll have none of that. "He is accepted anyhow and we rush him aboard."

And then there's a bit more than a page of further brainstorming about what happens aboard ship - with an note that "we've got plenty to happen when he gets back; what we need now is adventure and humor" and plot twists on the ship and on some alien planet.

Heinlein makes several mid-course changes in the story: the back-at-home duration of the voyage gets increased to 60 years, with Joel aging just three years; the ship goes through two names (Nautilus and Naughty Girl) and goes from making an out-and-back voyage to making a 4 or 5 leg journey. He tosses out the idea that an emigrant on the original trip out from Earth (then a 5 year old girl) grows up to be someone Joel might want to marry on his return to that colony world, and another idea that another girl from Joel's high school is on the crew of the ship, and he falls for her, but she marries one of the officers instead.

One thing he seems certain of is that while Joel's ship is still traveling, FTL ships are perfected and the relativistic starships become obsolete. He also mentions that Joel will find a "space bat" as a "cute and cuddlesome and smart e.-t." pet.

Eventually Joel has to go back to Earth (whether his stocks end up making him well-heeled or broke Heinlein waffles on), still single. A page is devoted to discussing the "Out-of-Phase Club, Anachron Lounge, etc" and Joel's meeting with the secretary of the club, who explains to him the club's purpose of helping relativistic starship crew by acting as translators and as a place where they can meet people from their own time period, since they are almost always going to find Earth's society, language, and customs to be bafflingly different from when they left.

Finally, the last page and a half of the outline is devoted to Joel's arranging to meet Jinny (who he imagines is now almost 80), the girl he ran away from and who has continued to haunt him, keeping him from marrying any of the "half a dozen other nice girls" he met on his travels. After getting to the Conrad house, he first sees Jinny's granddaughter and great-granddaughter, who confuse him with their cryptic talk ("'But Does He Know?' ... 'mind your own business, he's not calling on you'"). Jinny herself walks into the room at the bottom of page 7, and is revealed to be Jinny at the top of page 8.

Joel is (once again) is slow to realize that this is Jinny, still young - did Heinlein ever write a juvenile protagonist who was socially savvy and fast on the uptake? Anyway, I already summarized the last page above, no sense repeating that here.

I'm trying not to do a compare-and-contrast of Variable Star with the outline - that's not fair to Robinson, who is a talented author and who had to make it a living breathing Spider Robinson novel instead of a revivified zombie Heinlein. But I will say that I think it's unfortunate that Robinson lost sight of the Chekov's Gun rule - because he adhered so slavishly to the first half of the outline, then wrote his own ending, there are a lot of plot threads in the beginning of the novel that just trail off into nothing, while the ending of the novel just seems to come out of nowhere.

[fx Spock raising eyebrow and remarking "Fascinating"]

But it is, in a train wreck sort of way. The general tenor when "Variable Star" was released originally from those in a.f.h on the Usenet who read it was "If you like Spider Robinson, buy it; if you're looking for a long lost Heinlein work brought belatedly to life, run away." I was one of the latter. Even as a Robinson fan [not rabid, but not lukewarm either], enough came out at the time that I knew I would find it wanting. What has been said here, and in a few of the reviews I just googled on the current Amazon listing, confirms that early thought.

The summary of those notes were what was really fascinating. Your post of it was my first look at something like that of Heinlein's. And I now see the reasoning behind your speculation that RAH just "filed off the serial numbers" and turned those notes into three books.

Thanks.

Spider's website hasn't been updated in a while, but the news item that he had sold sequels to Variable Star is still up there. Anyone heard of progress on the next book by other sources or possibly from Spider directly?

I'm a frequent listener to Spider's "podcast", and he's indicated he's deep into working on his next novel. I don't recall that he's mentioned that it's a Variable Star sequel, just that it was contracted to be done soon/in the past/ maybe he's late, so he's got his head down concentrating on it now.

Hey glaurung, just a note: loved the above!