“Big G”: Getting to Orbit Post-Apollo

big-g-schematic

A schematic of one Big G configuration. The original Gemini capsule can be seen on the left, while everything from the passenger compartment on to the right was new. The adapter on the far right was designed to allow yet another cargo module, space lab, or habitation/life3 support module depending on the mission. Public domain image from a short briefing document given to NASA in December 1967. Click for a larger view.

What it was: A 1967 proposal by McDonnell Douglas to build a new Gemini spacecraft with an extra module attached to its aft end. This would be the craft for flying astronauts to and supplying the proposed space stations—both civilian and military—that were to follow the Apollo landings. It would have been able to deliver twelve people (ten on top of the pilot and co-pilot of the original Gemini) and 2500 kilograms of cargo to low Earth orbit; with an optional extension module it could have taken 27,300 kilograms.

Details: NASA was well into post-Apollo planning by 1967 and at that early stage it was far from settled that they were going to go for a spaceplane as their next major spacecraft. Even if they did go for one, some (including Wernher von Braun) felt that an interim system was needed until what was slowly turning into the Space Shuttle was ready. Basic research on lifting bodies was still underway and while landing on land was already considered desirable, at the time NASA’s chief spacecraft designer Max Faget favoured doing so with a ballistic capsule using a device that the agency had been working on for years: a Rogallo parawing to brake its descent.

big-g-and-third-module

A clear view of the third, cylindrical module which would have been used for some Big G missions. Public domain image dating to 1969 via the NASA publication SP-4011 Skylab: A Chronology.

While there had been discussions about using the parawing with an Apollo capsule, the Gemini had the advantage in that it was the one where that program had begun; it had progressed as far as manned drop tests—Jack Swigert of “Houston, we’ve had a problem here” fame started his career as an astronaut flying a Gemini mockup under a parawing. McDonnell Douglas then sweetened the pot by reconfiguring their Gemini B so that it had the same base diameter as an Apollo capsule (making it simple to attach to a Saturn rocket) while giving twice the cargo capacity of its competitor. A modification of the Apollo CSM had studied in the years prior to Big G, and the so-called MODAP could match this increase, and even go beyond it with external cargo capsules—but then this is where the Big G’s cylindrical extension module came in and blew the Apollo derivative out of the water.

The Gemini B had begun as a logistics craft for the USAF’s Manned Orbiting Laboratory that, for the purposes of this discussion, had one important difference from the regular Gemini. It needed to be able to dock to the MOL and the most reasonable way to do so was at its aft end. This necessitated cutting a hatch into the capsule’s heat shield. While this looked like a dangerous strategy on the surface, it was proven to work and it became possible to attach other things to the Gemini B’s underside. For the basic Big G this was a truncated cone that increased the base diameter of the new craft to match that of the Apollo spacecraft, making it easier to mate it with Apollo hardware—and not just rockets. While they preferred their own cylindrical module for the third module that made a regular Big G into the nearly thirty-ton large cargo craft, McDonnell Douglas also came up with a side proposal to use Apollo Service Modules in that slot if NASA so desired.

The Big G was designed to be launched by one of three rockets. In its smallest configuration, it would be lofted by a Titan IIIM, a man-rated version of the Titan III which the USAF had started working on as a rocket for the Dyna-Soar program and then moved over to the MOL when Dyna-Soar was cancelled. This was the least powerful of the three alternatives, and would have been able to launch only the basic Big G. For one with the full complement of extra modules the choices were one of two Saturn variants that NASA was interested in building, either the Saturn INT-11 (the first stage of a Saturn V with four of the strap-on boosters used for the Titan IIIM) or the Saturn INT-20 (which would have consisted of a Saturn V’s third stage directly mated to the same rocket’s first stage).

As Big G was proposed not long after the Apollo 1 fire, it was designed to use an oxygen and helium mixture for its atmosphere, a difference from the pure oxygen of the original Geminis. The interior of the craft was also heavily reworked, with all of its systems upgraded and improved from the original’s. After all, as successful as it had been the previously flown Gemini had been only the second model of spacecraft flown by the United States.

When launched the Big G could have flown directly to a space station of short resupply or astronaut delivery-or-return missions. Alternatively the third module could be adapted to be a mini space lab, or a life support and habitation module capable of stretching the flight to 45 days; when the Big G was first being discussed, the then-record longest spaceflight of 13 days, 8 hours, 35 minutes had been achieved in an original model Gemini.

big-g-landing

Coming in for a dry-land landing under its triangular parachute, the Rogallo wing. Public domain image from McDonnell Douglas briefing to NASA, December 1967.

As previously mentioned, the end of the mission would see the re-entry capsule of the Big G bring its  astronauts home to somewhere in the United States by landing with a Rogallo wing. The capsule itself would have three landing skids that would cushion the impact of swooping into the ground, and then bring the vehicle to a stop.

Using the Big G as its transportation backbone, NASA’s hope was to have a 12-man space station in orbit by the time the Space Shuttle was ready to fly in 1975 (to use what turned out to be the optimistic estimate of 1969).

What happened to make it fail: The late 60s were an era of falling budgets for NASA, and there was a great deal of concern that the cost of launches was going to sink the manned space program—the Saturn V was notoriously expensive on a per kilogram-to-LEO basis (one figure, adjusted for inflation to modern dollars is $US22,000 per kilogram). Prices were anticipated to come down, but in general even the cheapest expendable launch vehicles have only beaten this figure by about a factor of three.

A re-usable launch vehicle had the promising appeal of bringing these costs down a great deal (projections, unfortunately based on unrealistic launch schedules, ranged as low as $US1,400 per kilogram). For crew return this made a glider of some sort necessary—either a lifting body or a winged craft—and when a high cross-range capability in NASA’s next spacecraft was cemented as desirable about 1970, wings became an absolute necessity. All possibility of a capsule, Big G included, fell by the wayside.

What was necessary for it to succeed: In retrospect the Space Shuttle looks like a mistake—its most basic reason for existence was to be a cheaper way to orbit than missions launched on expendable launchers and it never did so—most calculations pin it as more expensive per kilogram to orbit than the already expensive Saturn rockets it replaced. It’s important not to apply too much hindsight to this decision, but even in 1969 there were signs that sticking with capsules for manned spaceflight was the way to go. NASA had a strong constituency for this approach including, at first, the chief designer for the manned spaceflight program Max Faget. If he had stayed on-board with capsules, there’s a good chance that things would have turned out that way.

If they’d decided to go with a capsule, the two main options were continuing using Apollo spacecraft or building the Big G. Apollo had the advantage of still being in production, and it could have been launched on very similar rockets to the ones suggested for Big G. Big G, as mentioned, had the advantage of considerably more cargo space. Which of the two would have been picked comes down to an impossible-to-settle question of which advantage would be seen as tipping the scale.

The other possibility is that the Shuttle could have gone ahead, but that NASA could have realized just how long it was going to take before it flew: instead of going to space in 1975 its first mission was pushed back to April 12, 1981. If in 1967-69 they had had a better handle on the challenge they faced, the idea of using Big G as an interim logistics craft until the Space Shuttle was ready to fly would have been more attractive. The only problem with this scenario is that the Shuttle’s development costs put a big dent in NASA’s budget through the 1970s, so the space station that the Big G would have supported would have been hard to build while also going ahead with the orbiters.

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6 thoughts on ““Big G”: Getting to Orbit Post-Apollo

  1. I don’t know enough about Shuttle development to say how plausible it might have been to pick up on the delays and costs early enough to save the Gemini variants. The Skylab and later ASTP missions might well have been considered enough to bridge the projected gap – I assume, in fact, they were – without having to go for a space station as well.

    I know the Gemini was always the astronauts’ favourite… even with the Shuttle on the cards, perhaps it might have lived on as a heavy-lift variant that happened to have some cargo capacity as well? I know people were talking about a need for that to run side by side with the Shuttle, relatively early on.

  2. Hello ! For a long time I’m writting an alternative history where the shuttle is replaced by a trio – Big Gemini + Agena space tug + a space station

    The Big Gemini eight volume study bore the exact title of “logistic spacecraft system evolving from Gemini”
    It can be found (not on line) here

    https://docs.google.com/viewer?a=v&q=cache:yLlWtuLIymMJ:mcgovern.library.tmc.edu/data/www/html/collect/Institution/NASAAll/AllMiss.pdf+&hl=fr&gl=fr&pid=bl&srcid=ADGEESjFQzPf-m-1U-dvQQdCUHEzVlfEg6bRr5KvEOhgQgwyrcvuS5NMnMQ4hqV2ecpS3s1O_2XrtDLstgD7eAra-YCk4UqyVYzTUJabeNGVxGO_iU8cVtpY7YVvJEpHEgcHXMM0tGbf&sig=AHIEtbTwk9gCw6jx9Q0pgt6b3LEneb3Ryg

    • Thank you! I had seen some of this summary but not the whole thing before. Darned shame the whole eight volumes aren’t available on-line, though — I searched high and low for them before giving up and deciding to write this entry based mostly on secondary sources and the short McD-D handout from which I got the pictures.

      • —Which of the two would have been picked comes down to an impossible-to-settle question of which advantage would be seen as tipping the scale.—

        So true ! My own humble opinion is that Big G was similar enough to a shuttle (land landing; cargo section; eight man crew) that NASA would have picked it over Apollo had the shuttle been canned. That seem pretty obvious, BUT budget cuts might have decided otherwise.

        — I searched high and low for them before giving up –
        So true once again. I share that frustration with you (and many others)
        For my part I’ve browsed Google books over and over and found a lot of little bits of information on Big G. Cost wise, an uprated Apollo was barely above $1 billion; Big G cost was $ 3 billion, the shuttle as we knew it, $5.15 billion.
        In desperation recently I dropped a mail to Scott Lowther (a.k.a Orionblamblam – of Aerospace Project Review) asking him if he could try and seek the Big G study. I’m waiting for an answer. Damn, I’ll be ready to spend some money for the Big G study…

        • “Cost wise, an uprated Apollo was barely above $1 billion; Big G cost was $ 3 billion, the shuttle as we knew it, $5.15 billion.”

          I’m going to have to work that tidbit into the revised version for the book. Costs are paramount in space development so I always like to include them if I know what they are. For this one, now I do.

          • I’ve found respective costs of Big G vs Apollo !
            This document,
            THE SPACE SHUTTLE AS AN ELEMENT IN THE NATIONAL SPACE PROGRAM
            http://www.dtic.mil/dtic/tr/fulltext/u2/729770.pdf
            says
            “SIX-MAN APOLLO SPACECRAFT
            For those alternative space plans in which the shuttle operation
            would be delayed or in which there would be no shuttle, a six-man modified
            Apollo spacecraft would be used. This vehicle would have a gross
            weight of 20,000 ib, a development cost of $1 billion, a first-unit cost
            of $300 million, and a launch-operations cost of $73 million.”

            As for Big Gemini, a google books search result in a tidbit of information from the “HUD-space-science-veterans appropriations for 1973: Hearings”
            which says
            “…over $1.5 billion for developing the Big Gemini capsule and the Titan III-M to launch the Big G were included, along with approximately 52.25 billion in recurring operational costs”

            Big G was slightly more expensive than Apollo – but much more capable !

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