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Beyond Apollo (1970)
HOW TO REPLACE THE APOLLO LUNAR LANDING SYSTEM (1976)

Between 1960 and 1970 there were countless studies exploring what NASA was supposed to do after Apollo 11 and the nine landings planned, up to Apollo 20. Nothing was carved in stone, and truth be told, future was pretty murky. There were studies of steps backwards – into low Earth orbit – or studies of step forward, onward to Mars. Also was statu quo – with Apollo exploring the Moon, why go elsewhere at all ?

One can ask whether or not Apollo was an efficient manned lunar landing system. Surprise: it was not, and that's the reason why it was brutally cancelled post Apollo 17, in 1972. Apollo largest sins were two-fold: nothing in the 5000 tons Apollo-Saturn lunar stack was reusable, and thus nothing was cheap. Every Apollo shot to the lunar surface cost a billion of dollar or so.

Now let's consider three monuments of sci-fi: Hergé Explorers of the Moon; Clarke and Kubrick 2001; and the mostly forgotten Continent in the Sky by Paul Berna, a French writer and a friend of Clarke. All three novels features lunar transportation systems very unlike Apollo. Tintin nuclear V2, Berna Astrospheres, and Kubrick Aries 1B doesn't stage nor expend bits and bits of spacecraft to reach the lunar surface. They are more akin to lunar airliners. The fact that – admittedly – they are not technically realistic doesn't change the bottom line, which is: in order to support a lunar base, you need an airliner to the Moon. The absence of such system explains why the only atempt at funding Apollo through private money (project Harvest Moon) imediately fell by the wayside. The whole Saturn - Apollo system just can't be handled to any private entity, it is just too cumbersome and expensive.

Thus one can ask whether, at some point after 1969 and Apollo 11 - did NASA considered a more efficient, cheaper to operate, manned lunar landing system ? Fasten your seat belts and forget Mars; forget the aborted space shuttle and forget the Liberty space station. Also, forget the 1966 AAP: Apollo Application Systems, which was a mere extension of the Apollo hardware, hence had the same sins.
NASA vision of Apollo replacement system featured two major aspects: a) reusable spacecrafts flying a large number of missions to save money and b) outposts everywhere to sustain the reusable systems who, unlike Apollo, needed refueling and refurbishment to keep flying.
By outposts we mean space stations and propellant depots – in Earth orbit, then in cislunar space. Here we are going to detail the reusable components in the shape of a short alternate history – how things might have happened after in the summer of 1975 the Apollo 20 mission concluded the first phase of lunar exploration – Apollo.

The year is 1976 – of the United States of America bicentennial, obviously.

Launch Complex 39A – Cape Canaveral, Florida

Even the mighty thrust of five F-1As is not enough – the Saturn INT-21 can't haul a fully-fueled Nuclear Shuttle into Earth orbit, so some tanking will be needed once in Earth orbit to perform a roundtrip to lunar orbit. Unlike the old S-IVB translunar stage the nuclear shuttle is reusable; after delivering a payload to lunar orbit it will brake itself back into low Earth orbit, ready for another mission.

Launch Complex 39B – Cape Canaveral, Florida

The 747-sized spaceplane lights its five huge F-1A engines and rapidly climbs into the Florida sky. Somewhat an aircraft – delta wing, vertical tail, cockpit, undercarriage and a handful of jet engines - has been wrapped around the mighty S-IC to make it reusable and save a large amount of cash. Forget a 140 ton empty can splashing and crashing in the Atlantic ocean thousands of kilometers away from The Cape. Albeit reusable the so-called flyback S-IC never reach orbit – it is way too heavy for that. It instead rocket into a suborbital flight and release the large payload stuck to its back.
Usually it is another winged, piloted space plane: the shuttle orbiter would haul itself into Earth orbit thanks to voluminous internal tankage and a trio of LH2/LOX rocket engines.

But today the payload stuck to the flyback S-IC is an enormous, non-reusable fuel pod; a fat tanker crammed with liquid hydrogen and liquid oxygen propellants. The winged S-IC reaches the apex of its suborbital parabola and release the fuel pod. After release the manned booster re-enter Earth atmosphere, gliding back to 30 000 ft. There it lights four big turbofans than pump kerosene from the rocket fuel tank. The two-man crew fly the S-IC back to The Cape, where it lands like an ordinary airliner.

Meanwhile the tanker fires its own shuttle-orbiter rocket engines and hauls itself into Earth orbit. There, a Reusable Nuclear Shuttle (RNS, powered by the infamous NERVA nuclear thermal rocket engine) awaits the tanker. It needs the propellant for a roundtrip to the Moon orbit and backwith a crew of four.


Launch Complex 39C – Cape Canaveral, Florida

The Saturn INT-21 is a two stage booster, essentially a cut Saturn V of Apollo fame. That peculiar Saturn INT-21 carries a payload of five LM-B, also known as space tugs - the RNS little brother. Two of the five space tugs features a cylindrical crew cabin; they are aimed to the lunar surface, replacing the expensive and cumbersome Apollo CSM-LM stack. The other three space tugs won't go to the Moon: they will be stored into orbit and later used for different missions, such as satellite repair or boosting a robotic probe into the solar system.


Up in Earth orbit the RNS is refueling from the fuel pod, topping its large hydrogen tank. The RNS is to carry the two LM-B tugs into lunar orbit so that one piloted tug can land on the lunar surface. The other tug awaits in lunar orbit for an eventual rescue flight. Unlike the LM-B the RNS doesn't burn its hydrogen fuel with liquid oxygen. Instead the hydrogen is heated by the nuclear core and then expelled through an exhaust. That was supposed to get twice the performance of the classic rocket engine – on paper at least.

So there is the reusable, cheap system that links Earth surface to Moon surface, replacing old Apollo. The flyback S-IC hauls a reusable orbiter that flies out to Earth orbit and meet a reusable nuclear ship there. The nuclear shuttle rockets to lunar orbit and delivers a piloted chemical space tug to the lunar surface. End result: four reusable vehicles – flyback S-IC, shuttle orbiter, lunar nuclear shuttle and chemical space tug / LM-B. Just compare that with Apollo seven expendable stages – S-IC, S-II, S-IVB, Apollo's Command Module and Service Module, the Lunar Module's descent stage and ascent stages.
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