The Dreamers

The Dreamers Early Mars mission architectures

As long as humanity knew of its existence, we have dreamed of going to Mars. It's no surprise then, that detailed plans for early Mars expeditions date back to the 1950s, even earlier in some cases. Lets start off with the original Mars Expedition plan: Wernher Von Braun's The Mars Project. Conceived in 1948, and first published in 1952, this book is considered the father of every planned Mars expedition since.

In The Mars Project, Von Braun outlines an "enormous scientific expedition" consisting of a fleet of 10 spacecraft, each carrying 70 crew members. They would be assembled in low orbit using reusable space shuttles, before departing for Mars. Von Braun calculated that for the entire journey, the ships would each need 5.32 million tons of propellent. Once in low orbit over Mars, a manned, winged, landing craft would undock from one of the orbital ships and make the perilous journey down to the surface, landing on the smooth ice at Mars's poles.

They would then travel, according to Von Braun, 6,500 km overland using tank like contraptions, before building a landing strip at the equator so that the rest of the crew could descend to the surface in their own descent ships (or "landing boats" as he called them). Using cables and a lot of work, the ships would then be turned upright, and their wings would be blown off. That would enable the crew to use the ships as conventional ascent rockets to return to low orbit and use the orbiting fleet to get home. The crew would end up spending a total of about 443 days on the Martian surface.

While this mission plan was revolutionary at the time, only sections of it (admittedly big ones) hold up today. Mars's atmosphere turned out to be too thin to glide through, and the dangers of cosmic radiation were not known at the time.

Nevertheless, The Mars Project remains the most influential conceptual Mars mission ever published.

The next major work on Mars missions was carried out by General Atomics, with Project Orion. Project Orion was a proposal for a huge nuclear powered spacecraft that would use nuclear detonations behind the ship to generate thrust. The actual use of a so called "Orion Drive" was far greater than just Mars expeditions, with plans for giant space battleships and even voyages to nearby stars being drawn up. This project actually got very far into development, with several test flights using conventional explosives being performed. Unfortunately, the project only ran from 1957 to 1965, and was cancelled after the introduction of the Partial Nuclear Test Ban Treaty.

In the timespan from the early 60s to the late 70s, hundreds of varied Mars mission plans were drawn up by companies including TRW, North American, Philico, Lockheed, Douglas, General Dynamics, and many more, including NASA itself.

After the success of the Apollo program, Von Braun started again advocating for Mars missions, using several Saturn V boosters to assemble an interplanetary spacecraft in low orbit, powered by NERVA (Nuclear Engine for Rocket Vehicle Applications) nuclear rocket motors (not Orion drives, just conventional nuclear rockets). Nixon however made it clear that the Space Shuttle was the direction NASA was headed, and so Von Braun proposed a variant on his plan that used Shuttles to assemble the spacecraft, reminiscent of his original plans in 1948. But it was never to be. After all of his proposals were rejected, Von Braun retired from NASA in 1972, upset with the direction the agency was taking now that the Moon landing goal had been accomplished.

Fun Fact:

In a follow-up book to The Mars Project, Von Braun hypothesised that the title given to a leader of the new Martian colonies wound not be The President, but rather The Elon.

8 In 1989, the Space Exploration Initiative was announced, with the aim of establishing a long term plan for the exploration of space. Part of this was the development of an eventual Mars mission.

While working for Martin Marietta, Robert Zubrin (who was working on designing interplanetary mission architectures) came to the conclusion that NASA's official space policy was fundamentally flawed. NASA wanted to perform a Mars mission by trying to make the most complex spacecraft possible, utilising as many advanced technologies as they could. Zubrin perceived this as "The exact opposite of the correct way to do engineering". (Quote from the documentary The Mars Underground, which can be found on YouTube and is highly recommended)

Zubrin started looking into alternative mission architectures, and came up with one that he believed was considerably better than NASA’s. It involved extending the surface stay to allow the astronauts time to explore the Martian surface, switching to a conjunction class mission to reduce travel times, using In Situ Resource Utilisation systems to reduce the launch weight of the ascent vehicle by several orders of magnitude, and he thew out the orbital assembly approach completely, favouring a direct ascent strategy.

His mission plan involved the following:

The development of a super-heavy lift booster named Ares. This would utilise already-existing Space Shuttle (also known as STS) hardware as much as possible. The core stage would consist of a STS external tank paired with two STS solid rocket boosters, in the same configuration as on STS. The STS orbiter would be replaced with an engine pod with three Space Shuttle Main Engines (SSMEs), which would be slung on the side of the core stage to allow it to interface with the already existing STS launch pads. Mounted atop the stack would be a hydrogen-oxygen upper stage, and in total it could place 110 tons into low orbit, or 47 tons on a trans-Mars injection orbit. The entire thing would be comparatively cheap to develop since it would be based on Shuttle hardware.

The plan would also require the development of a spacecraft named the Earth Return Vehicle (ERV), and another named the Habitation Module (Hab). Both would weigh 40 to 47 tons and would be designed with the intention of being mated to an Ares booster, sent to Mars directly, performing an aerocapture into low Mars orbit, and landing on the Martian surface.

The ERV would be a two stage craft with a large teleoperated rover carrying a small nuclear reactor slung underneath it. When the ERV lands, it drops the rover which drives a few hundred meters away, and places the nuclear reactor on the ground, preferably with a small hill between it and the landing site. The rover is then used to scout out the surrounding area while the ERV sets to work collecting CO2 from the Martian atmosphere (which is only half a percent as thick as Earths). This CO2 is reacted with 6 tons of hydrogen brought from Earth over the course of 6 months to make methane and water. The water is electrolysed into hydrogen and oxygen, and you would then have all of the necessary materials to make methaneoxygen rocket propellant, which is used to refuel the ERV for the trip back to Earth.

The Hab is a bit different. It's a tuna-can shaped module that will house the crew on their journey to Mars and during their stay on the surface. It has two decks, the upper one has living quarters and a solar-storm shelter, while the lower one has laboratories, workshops, and a "garage" for a large pressurised rover. Said rover is powered by a methane-oxygen internal combustion engine, and has a one way range of 1000 km, or a two way range of 500 km.

Launch One, Year 1 - An Ares rocket boosts an uncrewed ERV towards Mars. It lands 6 months later and begins making propellant.

Launch Two, Year 3 - Another ERV is sent towards Mars, arriving 6 months later.

Launch Three, Year 3 - A Hab is launched to Mars. Unlike the previous two launches, this one is carrying a crew of four. The Hab is landed next to the ERV sent there on launch 1, and the crew settles in for a one year long stay on the Red Planet. If they land too far away from the ERV, the second ERV, launch 2, can be redirected to land next to them. As it is, the second ERV lands a few thousand km away, and starts prepping for the next mission. After the crew finish exploring the surrounding area in the pressurised rover, they use the ERV to return home.

Launch Four, Year 5 - Another ERV is launched to Mars, arriving in 6 months.

Launch Five, Year 5 - The second Hab is launched to Mars, and like its predecessor it also is crewed. Upon landing next to the ERV sent there in Year 3, they do the same thing as the first mission again, in a new location.

From here on it repeats. To maintain this architecture would require 2 launches every 2 years, meaning there would be opportunities between launches to Mars where you could launch, say, a Lunar base using slightly modified versions of the same spacecraft.