Sidebar: The Tupolev OOS


A model of the OOS shuttle, believed to be from a Russian magazine in the 1990s. If you have more information about this picture, please contact the author.

During the 80s the USSR’s space program stayed remarkably focused on Energia/Buran and the Mir space station, especially when compared to the infighting that marred the years 1966-1975. It fended off or adapted to a number of distractions, whether it was Vladimir Chelomei‘s repeated attempts to regain his previous, short-lived position on top of it, or airplane design bureaus suggesting anything from conservative alternatives to the recently discussed Myasishchev M-19 nuclear scram/ramjet.

The OOS was a late Soviet-era shuttle proposal from the Tupolev bureau, an also-ran in that country’s space business despite a strong position in civil aviation and strategic bomber development. Proposed as a fully reusable replacement for Buran sometime around the year 2000, it was about the same size as that craft or the American Space Shuttle, though somewhat heavier at 100 tonnes when fuelled. With a crew of two cosmonauts. it had a payload of 10 tonnes to and from low-Earth orbit.

If you’re a long-time reader of this blog, or just sufficiently into spacecraft, you probably slotted the shuttle pictured above toward the conservative end of that spectrum. Apart from the more-rounded contours, it looks to be much like the Shuttle, particularly in the shape of the underside. There, too, we have the usual ceramic tiles for dissipating the heat of re-entry. The engines are not visible, but I can tell you that there were three, burning LH2 and LOX during the ascent to orbit (though, curiously, switching out the hydrogen with kerosene for orbital maneuvers). Knowing that would likely not change your opinion at all.

Given that it’s was to be fully reusable, the ten-tonne payload mentioned earlier may have got you wondering, though. The actual American and Soviet shuttles had payloads in the 25-30 tonne range, so alright—there’s clearly some sort of tradeoff there. You’d be well-advised to wonder about the rest of the OOS’s configuration. Side boosters but no external tank? Perched on a reusable rocket in some manner, maybe?

Well, no. “OOS” stood for Odnostupenchati Orbitalni Samolyot, ‘one-stage orbital plane’, But a single-stage-to-orbit craft the size of the Orbiter? Surely that’s not possible.

This goes to show that you don’t think like a Soviet aircraft designer circa 1989. The OOS was to have been air-launched, and the other half of the system was the Antonov AKS:


Aerospace aficionados will remember that the An-225, which was used to piggy-back the Buran shuttle around the Soviet Union, was by most measures the largest aircraft ever built. This is two of them, one wing apiece removed and replaced with a sort of aerodynamic bridge, and then 675 tonnes of spacecraft and rocket propellants attached to its underside. It had twelve turbojet engines for when it flew without the orbiter attached (the dark circles in the diagram above, at lower right), with a supplementary ten more being added during launch operations (the white circles). The Aristocrats! With a length of 83 meters (272 feet), a wheelbase of 40m (131 feet) and a wingspan of 153m (502 feet), the combination came in at a whopping 1650 tonnes. By contrast, a fully fueled late-model 747 has a maximum takeoff weight of just under 440 tonnes.

There has been only one successful air-launching system in the world to date, Orbital ATK’s Pegasus. It weighs 23.1 tonnes and can put 0.44 tonnes in orbit; it’s launched from a Lockheed L-1011, already getting into the neighborhood of large airplanes. So start with some skepticism that 20 times this in launch mass and payload are a possibility for the late-era USSR.

Further, I haven’t (unfortunately) been able to find a detailed description of the AKS/OOS’s mission profile. I’d like to see it because I’m having a hard time picturing what the moment of separation would look like. Or rather, I have an image of the support crew aboard the AKS bouncing around like ping-pong balls in a boxcar once the plane, straining to get the orbiter to altitude, suddenly cuts loose 675 tonnes. For that matter, the OOS would have to light its engines pretty quickly thereafter or defeat the purpose of an air launch. As these were in the same class as the RS-25’s on the American Shuttle—the noise aboard the AKS, now presumably not all that far above and behind it, would have been intense.

I’m on record for my begrudging appreciation of the come-what-may technological megalomania that gripped the superpowers post-WWII. The US grew out that uncritical mindset after Love Canal and Three Mile Island, while the Soviets carried on until 1989. That extra time coupled with fossilized technocrats in charge allowed awe-inspiring audacity in technology of it to grow even greater than it did in the West.

Even so, I can’t imagine anyone with the power to make the Tu-OOS happen actually doing so. It would have been an immensely expensive and difficult project right at a time when the Soviet Union was in no position to take one up, and technological limitations would have prevented anything like it at an earlier point in that country’s history. The OOS/AKS was a paper project, and would have remained so.


OOS, la bestia de Tupolev y Antonov

OOS, el sistema espacial de lanzamiento aéreo definitivo

Artist Vadim Lukashevich has numerous renders of the AKS/OOS combination on (screll down to the second half of the page).

Readers will note a lack of primary sources here. I’m convinced of this project’s existence, but any pointers to a source that’s a little more direct than what I’ve relied upon here would be most welcome.



Sidebar: The Langley Water Lander


A diagram of the Water Lander if it were full sized, as opposed to the one-eighth scale model that was built. Note the curvature of the wings as seen from the front, not coincidentally like the hull of a boat. Public domain image via NASA from Model Investigations of Water Landings of a Winged Reentry Configuration having Ourboard Folding Wing Panels. Click for a larger view.

There are two fundamental dichotomies in spacecraft design (or three, if you count the types of fuels used for their rockets). You have ballistic capsules in opposition to winged craft/lifting bodies, and you have water landings as opposed to coming in on solid ground. Three of the four possible combinations have been used by crewed spacecraft but one hasn’t: a water landing of a winged vehicle.

That’s not to say it hasn’t been examined, though. NASA studied the ramifactions of an emergency ditching of a Shuttle Orbiter (conclusion: a lot of damage to the underside, but it would stay afloat for a while as long as the wings weren’t badly holed), and the Australians famously photographed the USSR retrieving a BOR-4 test article from the Indian Ocean in 1983. Even earlier, the American ASSET, originally conceived for testing the alloys earmarked for the X-20’s heat shield, splashed down off Ascension Island after a suborbital jaunt from Cape Canaveral.


The Water Lander model in its tank. Public domain image from same source as previous. Click here for a larger view.

As far back as 1959, NASA was testing the concept using a water tank at Langley Research Center in Virginia. They had a chicken-and-egg problem, though. How do you build a water-landing spacecraft without tests to tell you what it will look like? But then how do you do the necessary tests without having it built first? Ultimately they had to just go ahead and build it based on first principles and common sense. What they came up with never had a name, so for convenience’s sake we’ll call it the Langley Water Lander.

The re-entry vehicle they posited was a light one, just 3600 pounds (1.6 tonnes), which is only a few hundred pounds more than a Mercuty capsule. Given that much of it was wings, it would have definitely seated only one astronaut, perched in a slim fuselage.

And it really was a lot of wing for its size, 27 feet from tip to tip and with an area of 263 square feet (7.0 meters and 24.4 square meters); it had no tail at all, though it did have a large vertical fin. The wing was gently curved, making a cross-section something like a boat so that the craft could rock from side to side on the surface of the water without the tips of the wings dipping below the surface. This was made even more unlikely by the fact that the wingtips were designed to fold up once the craft had gone subsonic.

On its underside were two retractable 4.7-foot × 0.67-foot (1.4m × 0.20m) water skis and a smaller triangular skid aft, roughly a foot to a side, for drag; this was found to be more stable during the final run-out than anything involving a single nose ski.

Thus configured, a one-eighth scale model was built and tested, with the conclusion that the landings were not so bad at all. The Water Lander wasn’t too sensitive to a little yaw in the touch-down, and even with small waves (eight inches high and fifty feet long, or 20 cm and 20 meters,to scale) the run-out was only three to four hundred feet with a maximum of 5.1 g deceleration. On smooth waters, it came in at under 3.0 g and 100 feet further travel after touchdown.

The Water Lander was never intended to be built for actual use, but rather was a reflection of where NASA was in late 1959. They examined a great many basic possibilities for the crewed space program, many of which have fallen into obscurity. In the case of winged water landers, the reason likely was that there’s no advantage to them. A ballistic capsule, almost uncontrolled, can benefit from a target as big as the South Pacific Ocean. But the whole point of a winged re-entry vehicle is that it can be directed once in the atmosphere, and if you can do that you might was well direct it towards a runway.


Model Investigations of Water Landings of a Winged Reentry Configuration having Ourboard Folding Wing Panels, William W. Petynia. Langley Research Center. December 1959.

Sidebar: The Intercontinental Ballistic Vehicle

Intercontinental Ballistic Vehicle schematic

A schematic of the IBV as printed in LIFE Magazine, March 7, 1955 via Google Books. Artist unknown, possibly Michael Ramus. © Time, Inc. Click for a larger view.

We’ve previously discussed Eugen Sänger and Irene Bredt’s wildly ambitious Silbervogel, a suborbital spaceplane that they worked on in Germany prior to the end of WWII. Mentioned in passing at the time was Stalin’s interest in it after the war, and Mstislav Keldysh’s unsuccessful attempt to scale back its necessary technological innovations so that the USSR could build something similar. What we didn’t look at at the time was the high-water mark of Sänger and Bredt’s craft in the United States.

Their core design paper was translated into English in 1946 as A Rocket Drive for Long Range Bombers (and is readily available today on the web), but otherwise there was not a lot of interest in it in the West. Sänger and Bredt lived in France for several years after 1945, having secured positions there, but worked on other projects.

Grigori Tokaev/Grigori Tokaty

Grigori Tokaty (to use his preferred name) in 2001, more than a half-century after revealing Stalin’s interest in rocket bombers to the West. Public Domain image via Wikimedia Commons.

Then, in November 1947, Soviet rocket engineer Grigori Tokaev defected to the United Kingdom. According to him, Stalin had become aware of the work on Silbervogel, and assigned the trio of Tokaev, Stalin’s son Vasily, and future head of the KGB Ivan Serov to the case. The Germans scientists were to be convinced to come to the USSR (Tokaev’s preferred approach) or kidnapped (Serov, naturally, for a man nicknamed “The Butcher”). The pursuers were unaware that the two they sought were no longer in Germany, though, and none of the three trusted any of the others, so nothing came of it. In 1949, Tokaev became an author under the Ossetian version of his last name, Tokaty, writing several popular articles about Soviet ambitions with long-distance airpower and other then-advanced weapons, then getting into an extended war of words about them with the hard Left in the UK.

Into this furor stepped John Earley and Garret Underhill in LIFE’s March 7th, 1955 issue, with an article named “From Continent to Continent”. Based on their own understanding of Sänger and Bredt’s work, as well as Tokaty’s story, they sounded the alarm. Keldysh’s aforementioned failure would not become known outside the USSR for many years, and the two LIFE authors felt that instead the USSR was probably working on the project with alacrity.

Their particular iteration of Silbervogel was closely based on the German design with a few variations suggesting that the authors didn’t really know what they were doing (for example, changing its trapezoidal cross-section to a circular one, which would be hell on re-entry). Launched from a rocket-propelled sled it would get up to a speed of 10,600 MPH (17,000 km/h) and 113 miles (182 kilometers) in height, then skip/glide its way around much of the planet. On a sortie from the Soviet Union, the authors thought that this craft would fly over the Arctic, bomb the United States, and then make a landing in the Pacific “for recovery by submarine”—which seems a bit optimistic but may reflect the idea in Sänger and Bredt’s original paper that WWII German Silbervogels could land in the Japanese Mariana Islands.

Really, “From Continent to Continent” is a bit of a head-scratcher until one realizes that it’s not a proposal, but is instead largely a con job, presumably written for the purpose of stirring up trouble and increasing circulation. For example, as can be deduced from the previous paragraph, the authors took the particular tack of describing how the IBV would be used to attack the United States even though the ostensible purpose of their article was to suggest that the US build one themselves, by their estimate in three years for a mere $23 million. Its mission as an American craft was left unstated, and was surely not the exact inverse of their favoured blood-curdling scenario of a Soviet attack.

There’s also the way the article’s authors are described: “[John] Earley, a rocket designer, and [Garrett] Underhill, a former Army officer who is an expert in Russian weapons” looks crafted to make unsuspecting readers think that they were insider sources for another, different LIFE correspondent. They’re almost certainly the authors of the piece themselves, even though it’s unbylined. I can find no other references to John Earley, but Garrett Underhill was the military affairs editor for LIFE in 1955 and had been out of the military intelligence business for most of a decade. Incidentally, if you’ve heard of Underhill, it’s as a minor figure in JFK conspiracy circles who committed suicide in 1964.

Taken as a whole, the IBV is more interesting as a snapshot of its time than it is as a quite ill-founded proposal. In a way it’s the flip side of the contemporary Moonship of Wernher von Braun: it was a popularization of the future military use of space, as opposed to its scientific exploration. The major difference between them is that von Braun’s fundamental vision was the one that took hold, making the way it was laid out in Collier’s and by Disney into well-known classics. Meanwhile the IBV has long since dropped into obscurity.

Sidebar: Alexeyev/Sukhoi Albatros


A conjectural diagram of the Albatros launcher, by Mark Wade of Encyclopedia Astronautica. Click for a link to the associated article. Used with permission.

Rostislav Alexeyev built the latter part of his engineering career on ground effect, which is the demonstrable fact that a wing generates more lift and experiences less drag when it’s in close proximity to the ground than it does while high in the air. In general aircraft don’t take advantage of it when cruising because of the increased risk—the ground is right therein the event of something going wrong, but Alexeyev was an expert on hydrofoil design and felt that the problem was sufficiently mitigated by flying over water to be worth attacking. Between the Khrushchev era and his death in 1980 he built his largest ekranoplan (“screen plane”), the so-called “Kaspian Monster” (KM: korabl maket, “test vehicle”) which met a watery fate in an accident not long after Alexeyev’s demise.

If you’re the sort of person who’s interested in Soviet crewed spaceflight you’re probably the sort of person who finds Russian ekranoplans and hydrofoils interesting too, but you may be wondering where the connection is between the two that would cause the latter to show up on a  blog devoted to the former. The intersection of this particular Venn diagram is the Albatros, outlined in a remarkable letter to the British Interplanetary Society’s Spaceflight magazine, published in 1983.

Long-time readers will recall that the Soviet space program was in disarray for much of the early 1970s, with 1974 being the year of crisis. Vasili Mishin was replaced by Valentin Glushko as the man in charge, and officials higher than him forced a change in focus from Moon missions to a space shuttle and space stations. For a period of time everything was in the air, and as was endemic to the Soviet space effort various other empire builders tried to get themselves a piece of the pie.

The design bureau of OKB-51 lurked on the edges of the Russian space program right from the very beginning, but never managed to convert its expertise in high-performance aircraft into any concrete projects. In 1974 they teamed with Alexeyev’s Central Hydrofoil Design Bureau to make a claim on the shuttle project, as at the time it was not yet settled that the Soviets would emulate the American Space Shuttle closely to produce Energia/Buran (consider, for example, Glushko’s MTKVP, which also dates to the same time). Their proposal was named Albatros, and it’s, so long as the source, space historian and writer Neville Kidger, got his Cold War information right, the only triphibious spaceplane ever proposed, requiring both water and air to get into orbit and land for its return.

One can see what, perhaps, they were thinking: margins are punishing on space vehicles, and it takes only a little inefficiency to turn a potentially useful craft into something that lifts a uselessly small amount of mass to orbit. Using aircraft as airborne launchers has been mooted a few times, why not use a ground effect “aircraft” to squeeze a little more oomph into your package?

The result was a three-stage vehicle, the first of which would have been a roughly 1800-ton, 70-meter long, Alexeyev-built, hydrofoilnot a full-fledged ekranoplan, alasthat could be thought of as a maritime version of the Space Shuttle’s external fuel tank. It would carry 200 tons of LOX and LH2 to feed the initial boost of the second stage’s motors.

Mounted on top of the hydrofoil, the estimated 210-ton second stage would use the first’s fuel to get up the whole arrangement up to 180 km/h over the course of 110 seconds, using the Caspian Sea (or the Aral or Lake Baikal) as a runway. Then it would disconnect and launch itself off the now-empty barge to consume its own propellants. This stage would be a high-speed reusable winged rocket plane/booster from Sukhoi that would lift the third stage—the actual spaceplane, also from Sukhoi—to a high altitude. There the latter would kick itself into orbit while the booster coasted into landing, possibly under pilot control; sources don’t say if the booster was to be manned, but with Sukhoi’s background it likely was.

The final stage was a tail-less rocket plane, about 80 tons in mass and 40 meters in length, so comparable to the American orbiter. It was estimated to have 30 tons of payload to LEO and a crew of two. It would have been larger than but was otherwise similar in appearance to some iterations of the Hermes shuttle, or to a lesser extent the later Russian/European Kliper. It was the most run-of-the-mill part of the whole vehicle, its design actually being closer to the American shuttle than the MTKVP. The air-based launcher was a radical approach, if not unique, but the underlying hydrofoil was the truly surprising suggestion.

It’s not difficult to see why the idea never went anywhere. Even putting aside the two partners’ inexperience with designing spacecraft, their proposed setup is ludicrous on its face, with tons of volatile propellant skimming over the water at triple-digit speeds, regardless of what its engineers might have actually calculated and put to paper. The likes of Dmitri Ustinov would have blanched if asked to sign off on it, as the country’s internal politics made Soviet decision makers inherently conservative. If they were eventually driven to insist on a close analog to the Shuttle over other proposals, one can only imagine what they thought about this one.


“Albatros”, Mark Wade,

Sidebar: The Multi-Role Capsule


The only contemporary image of British Aerospace’s Multi-Role Capsule—a competitor to the ESA’s Hermes spaceplane—of which the author is aware. The capsule itself is the larger aft section to the right, while the service module is in the foreground left. Originally published in Flight International magazine, October 24, 1987. Click for a larger view.

When the ESA settled on the Hermes spaceplane in November 1987 there was one dissenter from the ambitious space program of which it was part. The British government of Margaret Thatcher was in the process of killing the British spaceplane HOTOL due to its technical difficulties and weren’t keen on supporting another one. As a result one of HOTOL’s designers, British Aerospace, was about to be left out of the European initiative. Without much support from anyone they suggested just prior to the formal adoption of Hermes that Europe might want to talk a look at an expendable capsule for trips to and from the US’ as-yet-unnamed Freedom space station. They also put it forward to NASA as a possible lifeboat if astronauts ever had to leave Freedom in a hurry.

BAe knew that Hermes was the favorite, and so positioned what they called the Multi-Role Capsule (MRC) and being cheaper and quicker to build. It would also have been capable of being lifted by a modified Ariane 4, rather than the new specifically-designed-for-Hermes Ariane 5 on which the ESA was spending so much of its budget.

The spacecraft consisted of two modules, a crew cabin called the Descent Module (DM) and an ejectable Service Module (SM) for any systems that weren’t needed for re-entry and the DM’s splash-landing on Earth. This is the arrangement of many capsule-based designs, built or merely proposed, but the MRC was unusual in that the SM was considerably smaller than the capsule (796 kilograms, versus an unfuelled mass of 6204kg for the latter) and mounted on the nose of the DM instead of its tail. The SM’s low mass did mean that the MRC would not have had much maneuvering capability while in orbit.

After launch the capsule would have held four to six astronauts, or none at all if the mission didn’t need a human touch. One of the latter type would have been docking with the upcoming US Space Station Freedom for use as an escape capsule if the station had to be evacuated. BAe specifically positioned this as the MRC’s first role, hoping that a go-ahead from NASA would overcome Hermes’ momentum, or at least get the MRC developed in conjunction with the spaceplane. British Aerospace sweetened the pot further by making the DM reusable (the SM was to have been expendable) and proposing to build a full MRC for a relatively inexpensive US$183 million—after adjustments for inflation, comparable to an Apollo CSM.

Unfortunately for British Aerospace they couldn’t get the ESA to back their idea, and their fallback of building them for the US didn’t work either. NASA did study return capsules for Freedom and Alpha, but did so in house: as might have been suspected up front, they already had extensive experience building their own space capsules and didn’t see any good reason to have them designed and built out of the country. Even at that, NASA ended up deciding against capsules for rescue missions anyway because they felt that the high g-loads of a capsule re-entry would be a problem in the case of a medical emergency (though in the end not even the Americans ended up building the mini-spaceplane that would be necessary to get around that problem).

It’s also telling of British isolation from the ESA’s mainstream at the time that, after the Multi-Role Capsule had faded away, a coalition of the aerospace contractors Aérospatiale, Deutsche Aerospace, and Alenia Spazio (respectively representing France, Germany, and Italy) went ahead with an independent study of a capsule-based escape craft for the ISS, thus essentially duplicating what the British Multi-Role Capsule was to have done as its first job. The ACRV, as it was called, was also cancelled.

Sidebar: The Lunar Escape Device


The frontispiece for General Dynamics’ 1964 proposal “Study for a Lunar Escape Device”. Click for a larger view.

The LESS was far from the only suggestion for how Apollo astronauts could rescue themselves from the surface of the Moon—it was merely the best worked out. For example, in 1964 General Dynamics sent a report into NASA entitled “Study of a Lunar Escape Device”.

This was sufficiently far back in the past that the LEM (as it was still called at the time) hadn’t been fully designed yet; in the picture above it’s clearly still the first Grumman design rather than the one finally built. Even so the basic arrangement still held, and General Dynamics hit on the idea that when on the Moon even a wrecked LEM represented the best resource pool for astronauts trying to recover from a survivable crash. This approach also dove-tailed nicely with the major difference between the Apollo missions that would use the LED and the later missions for which the LESS was designed: there was no second lander to carry the escape craft and so it had to fit in the tiny weight allowance of the lander which was to carry the astronauts.


The world’s scariest IKEA instructions. How to dismantle a stricken LEM and turn it into an escape craft.

Accordingly, what General Dynamics designed was a kit of necessary extra components which would complement a number of much heavier parts cannibalized from the stricken LEM. Two of the lander’s legs would be removed and turned into a launch cradle. The LEM’s fuel and oxidizer tanks, its pressure tanks, the life support and comms equipment, and even a seat would be reclaimed too. Only support brackets for the tanks and seat, the main engine and small attitude controls, a star tracker, and a control panel would be unique to the rescue craft. Altogether the kit would come in at 49.5 kilograms and take up less than 60 liters of volume (2 cubic feet). General Dynamics’ pride at coming in at less than 0.4% of the entire LEM weight shines through the dry technical language of their proposal. Even once the cannibalized components are included the LED would have rung in at 460 kilograms (including propellant but not counting anyone on-board), which to best of the author’s knowledge makes it the smallest fully functional spaceship ever seriously proposed.


Literally flying by the seat of your pants. The crew arrangement for one and two astronauts aboard the LED.

The one-man version perched the astronaut at the end of what can only be described as some kind of high-tech witch’s broom, while the two-man version looks even more precarious. Under those circumstances, the seat was moved forward just enough for the second astronaut to stand behind the seat with his feet in stirrups attached to the bottom of its frame.

While quite clever, the concept suffers from two flaws. For one, it assumes that all the components of the LEM would be available for re-purposing, which seems optimistic when you consider that the LED would only be used if the LEM had crashed; it’s also unclear how the astronauts were supposed to remove two legs from the lander without causing further damage to it.

More subtly, the LED’s designers missed something that North American Rockwell picked up on when designing the LESS. The hard part of escaping from the lunar surface would not have been building a rocket that could do the trick—the Moon’s weak gravity and lack of air lets surprisingly dinky-looking craft make the journey to orbital heights. Rather the problem would be getting the escape craft into close proximity to the Command Module with a vector similar enough to allow the astronauts to transfer over. The later proposal spends many pages discussing how this could be accomplished, while the General Dynamics presentation merely states what the astronauts would need to do and then moves on in silence without discussing how they could possibly do it.

Sidebar: The Mercury Space Station


One of two configurations of a proposed Mercury-based space station. The other had the capsule stay in place with an inflatable tunnel running between the two hatches. Click for a larger view.

(Another little experiment along the lines of the Chief Designer posts. I’m finding a few space projects here and there that couldn’t support an entire discussion in False Steps’ usual format, but that still are worth examining. I’m thinking that perhaps they can be used as short sidebars here and there in the final product. I’ve tried two of them out on Reddit so far and they seem popular enough, so here they are for you too.)

In August 1960 McDonnell Aircraft suggested to NASA that a Mercury capsule should be extended into a small space station. This was despite the fact that a human being could just barely fit into a Mercury capsule, and couldn’t live in one for long—the final Mercury, Mercury-Atlas 9, could only last a full day because it was stripped down to hold more consumables, and even at that Gordon Cooper was only able to get it back to Earth through heroic efforts on his part.

That didn’t deter McDonnell. They suggested building a secondary, cylindrical capsule with the main Mercury capsule mounted to one end, and then sticking the whole thing on top of an Atlas LV-3B to fire it into space. Since it would be too heavy for that rocket to lift, the new capsule would have an Agena motor attached to its other end, which would finish pushing the spaceship into orbit.

They stated that the one man aboard the capsule could, with the aid of the extra living and storage space, live on board for an entire two weeks, performing experiments and whatnot until it was time to return home. As a result, they pitched it as a “space station”, but it really was no such thing. Altogether the whole thing only massed a few hundred kilograms more than the Vostok capsule that carried Yuri Gagarin into space; its internal living space was actually smaller than a modern-day Soyuz capsule. Nobody calls either of those craft space stations.

The Mercury Station never got built and likely the kicker was that the Mercury was pretty much an experimental craft. It was never intended to be upgraded and so McDonnell had to resort to a remarkable kludge just to let the astronaut onboard climb between the two pressurized volumes. Ideally there would have been a tunnel directly between the two when they were docked normally, but the Mercury’s retrorockets were in the way. So as designed, this craft would have had to take one of two approaches. Either the Mercury would stay in place and an inflatable half-toroid would join the hatch on the side of the capsule with the hatch on the secondary module, or else the Mercury would bend backwards on a hinge until its side hatch actually touched the side of the new capsule. Only then would the astronaut be able to clamber from one to the other.

NASA said no thanks and nothing ever came of it, but the basic idea seems to have evolved into the Manned Orbiting Laboratory for the US Air Force. Gemini was called “Mercury Mark II” after all, and was configured so that a tunnel could run between its base and any add-on modules behind it. It was quite natural, then to take the concept and adapt it to the newer, more capable spacecraft.