The Mars 2020 rover is a large spacecraft designed to carry human life support supplies on their surface, such as food, water, and oxygen. As you can see from the table above, Mars 2020 is only $3 billion dollars, while Mars 2020S will cost $4.5 billion. We’re looking at a $100 billion price tag for the Mars 2020 crewed project, not only because of the cost of constructing the spacecraft, but because the cost of sustaining those crew members for a time on the surface is almost entirely the project’s costs.
These costs are not negligible: the mission is estimated to cost $800 million per year for a year, which takes $90 million out of the entire Mars program until 2020. At that point, as of the time of writing, NASA is still funding the first two Mars spacecraft with roughly equal funds: $4.5 billion and $3 billion, on average. It’s true that Mars 2020 is the cheaper of the two, and as it has been demonstrated, using larger spacecraft can get significantly better results; one of these large spacecraft could carry people and the other could only act as a sample-return container. Mars 2020S will cost more, and probably will require funding well beyond the $4.5 billion mark, but overall it is a better idea when you compare them head-to-head. And while it may seem like there is no way to do it more efficiently, one way to do it efficiently is to use as many components as possible. If people are going to be onboard the spacecraft for a year and live and breathe on it, there is very little difference between a large and a small spacecraft. In other words, the cost difference between Mars 2020 and Mars 2020S is not just a result of the mission size, but also the costs, and so its efficiency is more limited than on the Mars 2020S. Additionally, since we’re talking about an upper-limb experiment, only humans are going to be onboard for a year; with that, the “efficiency” of the Mars 2020S isn’t as dramatic as an upper-limb experiment would be.
Mars 2020S with the rover
The Mars 2020 mission is interesting for two things: first, it is a significant step in the “deep space” exploration history of NASA. Mars was discovered, studied and explored by the US between 1950 and 1972 (roughly when the Mars exploration effort began), and it was one of the earliest missions ever proposed. The missions to Jupiter and Saturn were not proposed until the 1970s. The current space program is not very deep, and so we have only two, as-yet-un-determined, missions to Mars that were planned as long ago as 1967: Curiosity and the US-Russian Solar Probe to Jupiter. Since Curiosity has a much more complicated mission structure, we won’t be able to compare it to Mars 2020S at length, but it already has proven that even a relatively simple mission is just as simple as a lunar voyage; that said, it’s important to keep in mind that Curiosity is currently in the middle of the third year of its mission. If it falls off the target orbit, the mission will likely result in a landing the very next day, as the atmosphere was too thin. (If it’s a one-day landing, the mission will likely have to fly close to Mars before, if it wasn’t already, since the atmosphere is much thicker than we’re used to on the Red Planet.)
And second, to fully appreciate the idea of a Mars 2020 mission, one has to appreciate how different the US space program was back in the 1950s and 1960s, with missions such as Apollo/Mercury and the Moon landing effort and the Viking landers or the Skylab/Apollo space station, and in the late 1970s and early 1980s, with the early shuttle program and the shuttle-Soyuz mission. If you examine those specific programs, it’s clear that what made them more efficent than a larger, more complex spacecraft is for the following factors: the availability of hardware. For example: Apollo/Apollo-Soyuz was flown between 1975 and 1978, and the missions lasted only a few days, but for the crew to get safely out of Earth orbit and to a surface landing they required spacecraft that were capable of extended periods in low-Earth orbit. For each mission, they either used the Saturn-Soyuz booster-vehicle that was launched with them, or the Shuttle, and while the Soyuz is a more reliable spacecraft than the other two, it was still quite difficult to get out of Earth orbit with the other three, since the Soyuz couldn’t fly beyond 1,000 km. They also required the use of the shuttle, but if they went to orbit on the Shuttle, they still needed four additional payloads to make that orbit (I believe