I know I’ve spent a few days brainstorming for the first Mars mission in my science-fictional alternate history, but already I can’t help but plot out things even further for the timeline of early spaceflight. In particular, after the first Mars landing in 1963, what will be the next step? When will the outer solar system be reached by human explorers?
Techniques pioneered for the journeys to the Moon and Mars as well as other expeditions to deep-space destinations (such as asteroids and comets) will prove just as useful for interplanetary journeys across the inner solar system. Flights to Venus, Mercury, and much of the asteroid belt would take well under a year, and become relatively routine by the 1970s. Jupiter starts to look doable, tempting the bold.
The truly crazy might be tempted to do a manned version of the Grand Tour track the Voyager probes went on in real life during this period. I’m thinking some eccentric reclusive mega-billionaire on a clean modernist Discovery-esque ship all alone with only a HAL-like artificial intelligence for companionship. But that’s another story…
Now that’s a tantalizing passage. What would such a journey look like? In real life Voyager 2 launched in August 1977, taking advantage of a once-in-175-years alignment to visit the four gas giant planets in quick succession. It reached Jupiter in July 1979, Saturn in August 1981, Uranus in January 1986, and Neptune in August 1989. So 12 years total. Nuclear thermal rockets, which are used for the first Mars mission as early as 1963, are very roughly twice as effective as chemical rockets (greater than that, with more advanced versions). So a manned ship with the same sort of payload mass fraction as Voyager 2, but nuclear-thermal, could probably do the trip in half the time: 6 years, instead of 12 years.
The Voyage of a Lifetime
So launching in August 1977 our explorer could reach Jupiter in July 1978, Saturn in August 1979, Uranus in September 1981, and Neptune in August 1983. Naturally this would be a fly-by mission, though if more propellant was brought I suppose it would be possible to brake and assume orbit about these worlds for a while. But I kinda like the pure romance of a solo fly-by of these four worlds.
Presumably some way would be desired to turn the spacecraft around so its occupant can return to Earth. I’m thinking if it could fly by Neptune closely enough to dip into the upper atmosphere it could use an aerogravity assist to turn around. Alternatively, an outright aerocapture maneuver might be utilized so as to assume an orbit around the planet and mine propellant from the atmosphere of Neptune itself. Nuclear thermal rockets don’t combust fuel, they expel a working fluid heated with a reactor; any substance, therefore, may be employed as propellant, though hydrogen is best for a variety of reasons. Conveniently, ambient air at Neptune is 80% hydrogen and 19% helium.
So with our brave explorer tanking up at Neptune, what would the trip back be like? As of 1983 Uranus and Saturn are still nicely aligned for a flyby, but Jupiter has moved quite far out of the way. About the same transit time, 6 years, should be viable. If it’s a reverse of the trip there, then Uranus could be reached again in 2 years and Saturn in 4 years, with the trip from Saturn back to Earth taking 2 years. Our explorer could therefore return in August 1989.
Or would there be a direct return to Earth? Temptingly, Venus is about as close from Saturn as Earth is in autumn 1989. If a Venus flyby is undertaken then going from there to Earth some time in winter 1990 would be the most direct route. Mercury and Mars are possible, if the goal then becomes to complete an eight-planet tour, but they’re much further out of the way.
It would be a historic voyage, with our intrepid cosmonaut being the first to reach Saturn, Uranus, and Neptune. Jupiter would likely have been visited first by someone else earlier in the 1970s.
As for the technical details, it’s interesting to note that manned voyages beyond Mars is the point where NASA mission planning becomes slim pickings and hard science fiction takes over. I could find a 2003 NASA presentation called “Revolutionary Concepts for Human Outer Planet Exploration (HOPE)”, which no doubt factored into the Vision for Space Exploration’s declaration in 2004 that “over the long term, a human research presence at some of these worlds [e.g. Europa and Titan] may also become desirable”. That’s about it.
Nuclear Pulse versus Nuclear Thermal
Such a timeline as I outline here, where nuclear thermal rockets are used for exploratory voyages out to Neptune, would establish that nuclear pulse propulsion doesn’t become dominant for even the longest trips until after the 1970s, but it’s just too romantic and impressive a swan song for rockets being the cutting edge to resist (rockets will remain the workhorses for far longer), and besides, the general timeline of development does check out. I do intend for Inigo Sturm and a big expedition to visit all of the Kuiper Belt planets he discovered in the 1950s before the 20th century is out, which pretty much mandates nuclear pulse propulsion take over as the most effective method by then, but that story concept fits in quite snugly in the 1980s or 1990s.
It would also fit in snugly with the very first interstellar probes being dispatched by nuclear pulse from around 1990, achieving close to the theoretical maximum of 10% of light speed. That would imply there was some sort of breakthrough in nuclear pulse propulsion around the 1980s. Another aspect of my worldbuilding that would fit in snugly with is the fact that full-scale space habitats are ferrying scientists to the inner Oort cloud by 2020; if a decade or so after the initial breakthrough there’s a concerted program to start building out “the telescope cloud” that gives two decades of development, which feels like about enough time.
On the other hand, maybe there’s not quite as much a breakthrough as it appears; maybe nuclear pulse propulsion actually is the most effective way to reach Neptune even in 1977, but the explorer is doing rockets for veritably recreational reasons. This might even fit in with her characterization.
I’m thinking she’ll be much like Carlotta von Frey from “Wings of Fire”; a girl who’s spent much of her youth sailing solo in her yacht around the world, navigating only by the stars. With Lothar Brandt having been the first person to set foot on the Moon, and Oleg Losev himself probably taking the first steps on Mars, that leaves women in the cold as far as firsts in outward exploration of the solar system goes. This particular girl will be the first woman to make a fresh outward human exploration record; indeed, at Neptune she’ll be six times further afield than Jupiter, where the previous record was set.
As a pioneering woman on a solo spaceflight, the name of Valentina Tereshkova, our real-world first woman in space (and, believe it or not, still the only woman to have ever flown to space solo), comes to mind. So I’ve got an idea for this girl’s surname to be Valentinova, as a bit of an homage. Obviously yet another Russian, but giving Russia this particular first in space was intentional from the get-go. As for her first name…perhaps Apollinaria? It would be a nice homage to the real-world Apollo space program. Apollinaria Valentinova is a rather ponderous name, but helpfully Apollinaria has a short form, Polina.
I’m thinking she’ll be very young, in her twenties or possibly even her teens, a real adventuress type. It’s very unlikely she’ll have had enough time to build a business empire or fat investment portfolio from scratch by then, especially with all that sailing, adventuring, and deep-space planning, so she’d have to be an heiress born into wealth.
A giant Spaceplane to Neptune?
As for the design of the actual ship, that’s honestly a blank page at this point. I have a clean sleek modernist design in mind for the interior, a la “2001”, but what about the exterior? I was at first thinking a bola, then a sphere, but now I’m thinking, in light of how it needs to gather fuel from the air at Neptune, why not a giant spaceplane or lifting body, something that can fly inside an atmosphere and have big jet intakes? Of course the centrifuge would have to be inside the airframe, but that goes with the “2001” vibe (the Discovery had an internal centrifuge); it would be one monstrous aircraft though. Hmm…I’m going to have to think about that one more.
I think I’ve got a pretty cool concept going here, which along with my Mars expedition story, the Venus concept, and even a Moon cycler concept will keep plenty of story potential coming for the rest of 2023.