I occasionally enjoy exploring alternative history events that actually could have happened and what could have happened next if they had … On this first instalment: the alternative lunar landings project: Gemini Advanced.

Alternative to Apollo
The Gemini project of the mid-sixties that sent crews of two US astronauts into low-earth orbit (LEO), and even a few more extended orbits, was a very successful stepping stone on the way to the Moon. With its use of Titan launch vehicles the Gemini capsule (left, blue)represented in many ways a conservative step up from what had been used during 1-astronaut flights of the preceding project Mercury. The capsule was augmented by a service module (left white) containing life-support and propulsive systems. During the 12 flights of Gemini a whole host of necessary techniques and technologies were tested, tried and tested again. This ranged from basic orbital manoeuvring, to space-walks, from rendezvous to docking exercises. All crucial aspects which needed to be mastered before a lunar landing could ever be attempted.

The Moon on a Shoestring

However in many ways the Gemini also represented the ‘on a shoestring’ designs of Mercury. Not only did Gemini launches assume astronauts would ‘eject’ from their seats in the case of trouble rather than use an escape system that would rescue the entire capsule, the capsule was also rather cramped and tiny for its two-person crew. One only needs to look at the comparative sizes of the rockets used on Apollo vs those used on Gemini and Mercury to appreciate better exactly what a huge leap Apollo presented.

On the picture to the right the first three vehicles depicted are the Mercury-Redstone and Mercury-Atlas combinations used in the one-astronaut Mercury flights and the Gemini-Titan combination used in all Gemini flights. The remaining two vehicles are the Apollo-Saturn 1b used for Apollo 7 and several Skylab missions and the humongous Apollo-Saturn V vehicle used on all Apollo flights (8-17) that aimed for the Moon. The Saturn launch vehicles were in a class of their own. Where Titan, Atlas and Redstone were in fact ballistic missiles adapted to spaceflight purposes, the Saturn rockets are not, and were never, in use as missiles with an military application to speak of. They were, as all 20th century rockets, designed starting on the basis of military technology but the Saturn boosters were definitely no longer in that category.

It is probably one reason why they fell into disuse after Apollo as a project was abandoned after its 6th successful lunar landing by Apollo 17 in 1971. The Skylab project basically used-up whatever space rockets and parts were left over from the aborted Apollo project. Compared to the technologically far more demanding and challenging Saturn V and Apollo command module and lunar lander, the Gemini hardware seems like from a different era.

Lets use what works

Always in Space exploration there has been the temptation to use whatever is already there rather than to go down a bold new route. So if we think of Gemini and the mid-sixties: what were the components that were already there? In order to give the Gemini missions a vehicle to rendezvous and dock with the Agena module was used. On the left here it is fitted atop an Atlas launch-vehicle. The Agena carried an assortment of instruments, a docking module and additional propulsion systems. During the second half of the Gemini missions in two instances the Agena’s engine was fired up to boos the Gemini capsule and service module into a higher orbit. This kind of orbital maneuvering needed to be mastered for the more complicated missions to the Moon. In particular as by that time the exact mission profile for the Moon missions had not yet been decided upon. The development of the humongous Saturn V came from the idea of flying directly to the Moon’s surface and back in a single launch. Mission profiles that constituted of several launches with smaller launch-vehicles, such as the Atlas or the Titan launcher used on the Gemini missions, and assembly of the Moon-vehicle in Earth orbit or Lunar orbit, or both. So one possible configuration for a Gemini-based lunar mission could be to launch something like a Agena-like Earth-departure stage into orbit and to get the Gemini capsule + service module to dock with it. In addition the service module of the Gemini would need to be expanded to cover the additional life-support needed for the longer duration flight. Evidently what was also required was an excursion vehicle to actually land on the lunar surface itself. Interestingly the “Gemini Advanced” concept had exactly such a mission design in mind.

Gemini landing vehicle

The Gemini landing vehicle-design was suited for only a single astronaut. Nowadays, with Apollo in mind, this (left) seems like an incredibly risky and fragile set-up. With 2 astronauts on a Gemini lunar mission, one would need to stay in lunar orbit while the other descended to the surface. After a short excursion on the lunar surface the two would need to rendezvous in orbit again. As one can easily spot form the design, there is no docking facility there so the transfer of the astronaut from the Gemini capsule to the lander and back would have been executed by a space-walk.  That would allow saving weight by not taking along a heavy docking-module with all its locks and safeguards and associated risks. But it would also imply that the lunar lander would be no good for anything other than its principal mission.

Crazy as this scenario might seem from a modern-day post-Apollo point of view, exactly the same mission was envisaged by the other party in the Space-race for the Moon. The Soviet lunar lander LK3 (right) was also a 1-crew landing vehicle despite its design looking a little more like the later Apollo lander. Several of these have actually been built and are now in a number of musea scattered across Russia and former Soviet republics. As with the Gemini-lander design, the astronaut exchanging between lander and Soyuz crew vehicle was supposed to do so via a space-walk. The reason for these designs is the uncertainty whether a launch vehicle could be designed that would pull off the massive weight-lifting necessary to bring a fully-fledged lunar excursion vehicle into orbit together with the crew-module. The Saturn V was capable of that but its Soviet counterpart, the N1, failed on multiple attempts at a launch and was abandoned. The Gemini Advanced set-up was abandoned as well when it became clear that with the Saturn the NASA had a launch vehicle that was capable and available for the more demanding mission. So instead of assembling a lunar vehicle in Earth orbit from multiple launches the Saturn could put the entire vehicle in LEO in one go. The only rendezvous and docking needed was to happen in Lunar orbit between Apollo crew module and lunar excursion vehicle.

What would have happened?

It is interesting to speculate what would have happened when the US had decided to go for the Gemini Advanced design. I will mention only two things. First of all let me highlight the crucial role played by the lunar lander in the near-disaster of Apollo 13 (left). With a tank explosion ripping apart the service module of the Apollo crew vehicle the astronauts had to hurry to safety inside the lunar lander. With the Apollo ship switched of to save power the systems of the lunar lander kept the crew alive and prevented them from freezing to death.  The catastrophic tank failure happened after the Apollo had started its journey to the Moon and thus an early return was not possible. Had the lunar lander been one of the Gemini Advanced type the crew would not have survived the accident. Secondly, the Gemini Advanced was a “Moon on a shoestring” design that could perhaps “get you there” but wouldn’t allow the astronaut to bring anything with them or to spend any significant amount of time on the surface of the Moon. Later versions of the Apollo lunar lander sustained astronauts on the surface for up to a week. The Gemini Advanced lander however would be good enough to jump out, stick that flag in and be on your way back. The lunar landings missions would probably have ended after the first successful attempt.

When the past becomes the future

Today NASA is once again putting all its cards on re-using old tech, “stuff that works”, for its future missions. Its Space Launch System (SLS) is merely reworked Space Shuttle technology. Its plans for missions to the Moon and beyond are mostly missions requiring multiple launches and assembly in Earth orbit. The SLS is significantly delayed in development and vastly running over budget. It could very well be that the far bolder design of SpaceX’s “StarShip” (right, middle) will be completed and flying before SLS even gets off the ground. Some will then argue that this represents private sector efficiency over state-sponsored slacking. But in reality it is more likely that it represents that boldness and mission-focus is likely to win out over relying on what you know.

You might say that what set Gemini Advanced apart from Apollo was that Gemini Advanced sought to work with what you’ve got to do whatever you can. Apollo sought to do what you wanted to do and to build for that the capacities you need. Apollo’s spare parts produced some of the most interesting LEO manned space exploration as a spin-off. It is the same philosophy but in reverse order.