The first mission to Mars: Can and should it happen by 2033?

These call for the first crewed missions to explore Mars! According to the evolving architecture NASA has shared – outlined in the NASA Transition Authorization Act of 2010, 2017, and 2020 – these missions will commence by 2033, with follow-up launches happening every 26 months (in 2035, 2037, 2039, and so on). According to recent statements, China plans to follow a similar timetable, with launches beginning in 2033 and extending into the 2040s. 

These mission architectures will culminate with the creation of the first surface habitats on Mars. These habitats and the accompanying infrastructure will pave the way for regular missions to Mars and be the first step in extending human space exploration beyond the Earth-Moon system. They could even lead to humanity becoming “interplanetary” and establishing the first permanent settlements on the Moon and Mars.

But are these hopes realistic, especially where the timelines are concerned? Can the human exploration of Mars really begin by 2033, or will the challenges (which are legion!) cause the missions to slip to a later date? Opinions vary, and addressing that question comes down to several caveats and uncertainties.

“Get Your A** to Mars!”

Since the NASA Transition Authorization Act of 2010 was passed, which defined the goals of NASA’s “Journey to Mars” (or “Moon to Mars”), a few things have changed. However, the overall mission plan has remained much the same. Even with the introduction of the Artemis Program and the revised timetables it contained, NASA policy is still guided by the three-phase plan they adopted in 2010. These include:

• Phase I - The continued development of the Space Launch System (SLS) and the Orion spacecraft and continued research into the effects of long-duration spaceflight aboard the International Research Station (ISS). 

• Phase II - The creation of the first permanent American presence and infrastructure on and around the Moon - the Lunar Gateway and the Artemis Base Camp. 

• Phase III - The development of the Deep Space Transport (DST) and the deployment of an orbital habitat (Mars Base Camp) and a reusable landing system (Mars Lander).

To briefly summarize, NASA’s vision is to use the SLS and Orion to send the first astronauts to the Moon since the Apollo Era (Artemis III) by 2025. The core elements of the Lunar Gateway will be launched in 2024 by a SpaceX Falcon Heavy. By 2028, the Artemis Program will have finished assembling the Lunar Gateway and established the Artemis Base Camp in the South Pole-Aitken Basin.

Between 2028 and 2033, NASA plans to validate the DST and its propulsion system – a 500 KWe Solar Electric Propulsion (SEP) system – and use it to send the modules of the Mars Base Camp and Lander to be assembled in orbit around Mars. In 2033, the first crewed mission would depart, with follow-up missions happening every 26 months (2035, 2037, 2039, etc.). These would establish a long-term base on the surface that later missions could use.

In 2021, China announced it would also send crewed missions to Mars by the 2030s. While the details have been scant so far, the Chinese government has indicated that its missions will coincide with NASA’s timetable and culminate with the creation of a permanent base on the surface.

Unfortunately, the challenges of getting to Mars have also remained the same. What’s more, the mission architecture contains several issues that have yet to be resolved. Let’s review, starting with all the challenges that any mission headed to Mars in the coming years must contend with.

Launch windows

Mars has a much wider orbit around our Sun than the Earth, ranging from 128.4 million miles (206.65 million km) at its closest (perihelion) and 154.884 million miles (249.26 million km) at its farthest (aphelion). This is equivalent to about 1.38 to 1.666 Astronomical Units (AUs), the distance between the Earth and the Sun. Mars also has a longer orbital period, taking just under 687 days to complete a single orbit around the Sun. 

This means a Martian year lasts almost twice as long as a year on Earth. Furthermore, it means that launch windows between our two planets are restrictive - at least in comparison to the Moon. To minimize the time spent in transit, missions destined for Mars must coincide with when our two planets are closest.

When Earth and Mars are at their closest, known as a Mars Opposition, they are roughly 50 to 60 million miles (~80 to 100 million km) apart. When Mars and Earth are on opposite sides of the Sun (known as a Mars Conjunction), they can be as far as 250 million miles (400 million km) apart. During a Mars Close Approach, which last occurred in 2003 (and won’t again until 2287), Earth and Mars pass Within 36 million mi (58 million km) of each other.

This means that missions bound for Mars, barring a favorable planetary alignment or next-generation propulsion systems, will be forced to launch only every 26 months to coincide with an Opposition. 

Transits

Even when Mars is closest in its orbit to Earth, it still takes a long time to send missions there. In 1975, NASA’s Viking 1 and 2 missions launched from Earth and took 304 and 333 days to reach Mars (about ten and eleven months), respectively. More recently, NASA launched two rovers (Curiosity and Perseverance) as part of their Mars Science Rover (MSR) program. The rovers took 254 and 203 days to reach Mars – about eight and six months, respectively. 

Keep in mind, however, that these were robotic missions. Sending crewed missions is far more complex, requiring larger spacecraft, more propellant, and significantly more planning. The best method of sending crewed missions to Mars involves a maneuver known as a Hohmann Transfer Orbit (HTO), where a spacecraft places itself into an elliptical flight path tangential to both the initial and target orbits. 

According to NASA, using an HTO maneuver that coincides with a Mars Opposition, it would take a crew of astronauts an estimated nine months to transit between Earth and Mars. The return trip would also take nine months, but the crews would have to wait for 16 months until Mars and Earth were closer. This means the astronauts would be away from Earth for about 1034 days (two years and ten months). 

Considering all the health and safety hazards that deep space and the surface of Mars present, a mission that lasts this long could take a terrible toll on astronauts. 

Radiation

For astronauts, one of the biggest hazards of going to space is the additional radiation their bodies are exposed to. Beyond Earth’s dense atmosphere and the planet’s protective magnetic field, the radiation environment is much more intense. According to NASA, “Space Radiation” consists of high-energy particles that originate from our Sun (solar wind) or interstellar space (cosmic rays).

Solar wind consists mainly of electrons but can also be in the form of protons and alpha particles (helium-4 nuclei). Cosmic rays, on the other hand, are protons and atomic nuclei that have been stripped of their electrons and accelerated to relativistic speeds (close to the speed of light). Elevated exposure to either source of radiation can increase the risk of cancer and damage at the genetic level.

In addition to having a very thin atmosphere, less than 1% of the air pressure here on Earth, Mars has no intrinsic magnetic field. Astronauts operating on the surface would therefore be exposed to radiation levels of up to 244.5 mSv per year – about 20 times what people in developed nations are exposed to on Earth (around 6.2 mSv per year). The situation is even worse when solar flares occur.

Even worse is the deep-space radiation environment where astronauts will spend up to a year and a half in transit. Estimates indicate that unshielded astronauts would be exposed to between 400 and 900 mSv annually. Combined with up to a year spent on the surface of Mars, that means that astronauts sent to Mars will be exposed to roughly 500 to 1000 mSv during the full mission.

This vastly exceeds NASA’s health and safety guidelines, which limit the amount of radiation astronauts can be exposed to during their entire careers to 600 mSv.

Microgravity

As if that weren’t enough, there’s also the issue of long-term exposure to Martian gravity (roughly 38% that of Earth’s, or 0.379 g) and microgravity. Several studies aboard the International Space Station (ISS), like NASA’s Twins Study, have shown that long-term exposure to microgravity can take a severe toll on human physiology. 

These studies have shown that spending up to a year in space leads to muscle atrophy, bone density loss, and impacts on cardiovascular health, organ function, eyesight, the central nervous system, and even gene expression. With transit times of six to nine months, the astronauts will spend up to a year and a half in microgravity and up to a year in lower gravity.

Combined with exposure to elevated radiation levels, there are significant concerns about crews being in good health and ready to conduct surface operations when they arrive on Mars. There are similar concerns about the state of their health upon return to Earth. There’s also a lot of uncertainty when it comes to reacclimating to Earth's gravity and what the long-term effects of all this exposure could be.

Possible solutions

To break it down, the challenges come down to launch windows, transit times, and prolonged exposure to radiation and microgravity. Fortunately, these hazards have a common solution: go faster and shorten the transits, which will decrease the health risks accordingly. Unfortunately, the options for faster propulsion systems are somewhat limited. 

Conventional propulsion, which relies on igniting chemical propellants and using the resulting exhaust to generate thrust, is subject to the Rocket Equation. This establishes that any change in velocity a rocket gets from burning fuel mass will have a corresponding decrease in the total rocket mass. Spacecraft need to carry enough propellant to achieve higher velocities, but this comes at the expense of more mass and larger propellant tanks.

Solar Electric Propulsion (SEP) is a fuel-efficient and lightweight alternative that NASA is actively exploring for missions to Mars. This method relies on Hall-Effect Thrusters (aka. Ion engines), where solar panels provide electricity to ionize inert gases (like xenon). Magnetic fields then accelerate these ions through nozzles to generate thrust. 

Unfortunately, SEP’s immense fuel efficiency comes at the expense of velocity. Not only does it take a long time for a spacecraft equipped with SEP to accelerate, but it also draws less power the farther it gets from the Sun. To illustrate, NASA’s Deep Space 1 demonstrator satellite took fifteen months to accelerate to 8,000 mph (12,875 km/h). 

Another example is NASA’s Dawn spacecraft, which launched from Earth on September 27th, 2007, and explored Vesta and Ceres (the largest bodies in the Main Asteroid Belt) between 2011 and 2018. On its way to the Asteroid Belt, the mission flew past Mars, making its closest approach on February 18th, 2009 - roughly seventeen months after leaving Earth.

Faced with these limitations, NASA and China have two options for sending missions to Mars. One idea that is currently on the table is to develop nuclear rockets that would shorten the trip exponentially. The other is to adopt mission architectures that take advantage of planetary alignments and sacrifice the possibility of landing on the surface.

The nuclear option

Nuclear propulsion offers several advantages over conventional methods. The most obvious is improved power, velocity, and almost unlimited energy density. In addition, spacecraft equipped with nuclear-thermal or nuclear-electric propulsion (NTP/NEP) systems need less propellant to achieve a Holhman Transfer maneuver between Earth and Mars. This means that spacecraft can be lighter and still powerful, thus breaking free of the Rocket Equation.

NTP and NEP rely on the slow decay of radioactive isotopes (like Uranium-235 or plutonium-238) to generate heat or electricity. In the case of NTP, the reactor heats propellant (such as deuterium fuel) to create a hot plasma that generates thrust. In a NEP system, the reactor generates electricity for a Hall-Effect thruster that ionizes gas propellants like xenon or krypton to create thrust.

A major bonus of the technology is that we know it works. Nuclear reactors for use in space have been verified by NASA and the Soviet space program, both of which created and tested prototypes during the Cold War Era. This includes the Nuclear Engine for Rocket Vehicle Application (NERVA), developed by NASA (1955-1973), and the RD-0410, developed by the Soviet Union between 1965 and the 1980s. 

In recent years, there have been renewed attempts to develop nuclear propulsion. Examples include NASA’s recent agreement with the Defense Advanced Research Proposal Agency (DARPA) to develop and test a nuclear rocket. Known as the Demonstration Rocket for Agile Cislunar Operations (DRACO), NASA and DARPA hope to have a prototype ready for orbital testing by 2027. 

Earlier this month, China conducted the first in-orbit test of a Sterling engine, a thermoelectric converter that could have applications for NTP. Researchers with the CNSA also published a paper last year that explored the possibility of a nuclear-powered mission to Neptune. 

In January 2021, the UK Space Agency (UKSA) recently announced that it was partnering with Rolls Royce to investigate nuclear power for applications in space. This announcement mirrors similar statements by the ESA and NASA to start (or restart) programs for spacecraft equipped with nuclear reactors.

NASA has also explored the use of Sterling engines and nuclear reactors in recent years, starting with the Kilopower project in 2018 that led to the Kilopower Reactor Using Stirling Tech (KRUSTY) demonstrator. These efforts have since transitioned into the Fission Surface Power (FSP) program.

Alas, the most attractive thing about nuclear propulsion systems is the way they would drastically reduce transit times to Mars (and other deep-space destinations). Based on various proposals, a nuclear-powered spacecraft could journey to Mars in about three months (100 days) or even in as little as 30 days! 

Unfortunately, there are doubts that NTP or NEP systems will be ready for crewed missions by 2033. These doubts were raised at the ninth annual Achieving Mars Community Workshop (AM IX) in Washington, D.C., in June 2021. Regarding nuclear propulsion, critics reportedly cited “studies that suggested neither NTP nor NEP would be available in the human exploration time horizon of interest.”

The orbit-only option

The other option, as noted, is to sacrifice operations on the surface of Mars and go with an “orbit-only” mission architecture. This option was explored during the Cold War by NASA and the Soviets when contemplating their objectives for the post-Apollo Era. This included the Soviet Heavy Interplanetary Spacecraft (TMK) that had a proposed launch from Earth in 1971 to conduct either a three-year or 21-month mission, including a Mars flyby. 

Similarly, Humphrey “Hoppy” Price (the chief engineer of NASA’s Mars Exploration Program) and his colleagues at NASA’s Jet Propulsion Laboratory (JPL) wrote a paper earlier this year proposing an orbit-only mission that would take advantage of a favorable alignment between Venus, Earth, and Mars in 2033. According to Price and his colleagues, the mission would last 570 days and could be accomplished using existing technology. 

While the mission would not involve astronauts landing on the surface (they would spend 30 days in orbit), the authors note that an orbit-only mission could serve as a precursor for future missions, which they estimate could begin by 2037. In much the same way that Apollo 8 paved the way for Apollo 11, or Artemis II is a precursor to Artemis III, the authors state that their proposed mission:

“[W]ould not be a one-off mission but could be a pathfinder to retire risks related to crew health and for the vehicles and systems to be used for follow-on missions that would land crews to explore the surface of Mars and conduct compelling science, such as the search for past and present life.”

But given the cost, effort, and the fact that no follow-up missions could happen for another four years, does it make sense to sacrifice surface operations for an orbit-only mission in 2033? At this very moment, there are eleven robotic missions exploring Mars (including rovers, landers, orbiters, and one helicopter!), studying its surface, atmosphere, climate, and seasonal and annual cycles.

The purpose of all this is to learn more about the history of the Red Planet. Scientists want to know how and when it transitioned from a warmer planet with flowing water on its surface to what we see today. More importantly, they want to know if Mars once had life and whether there could still be life there today.

Many scientists consider Mars the most likely place to find life beyond Earth. Given this, it is little wonder why all of our astrobiology missions (at present) are focused on Mars. Confirming that it once had life (or still does) could provide immeasurable insights into how life emerged on Earth. And given the similarities between Earth and Mars (nicknamed “Earth’s Twin”), its geology could teach us volumes about the formation of the rocky planets in our Solar System.

The chance to send missions to explore the surface, conduct extended research, and bring samples home for analysis is practically the whole reason for sending crews there in the first place! 

Funding or timing?

In an op-ed released in 2015, NASA scientists Dr. Olin G. Smith and Paul D. Spudis attempted to estimate the cost of NASA’s Journey to Mars. Smith was a former manager of Shuttle Systems Engineering at NASA’s Johnson Space Center, while Spudis was a staff scientist at the Lunar and Planetary Institute (LPI). Both men have since passed away – in 2020 and 2018, respectively.

According to Smith and Spudis, the program could cost as much as $1.5 trillion (in 2015 dollars), or $1.91 trillion today. Worse, their assessment was based on an annual budget of about $54 billion in 2015 dollars (or 1.5% of the 2015 federal budget). This would represent a dramatic increase from current funding, as the U.S. government has not allocated more than 1% of its federal budget since the end of the Apollo Era in 1972.

NASA’s budget for 2023 is $32.35 billion, slightly less than half of what Smith and Spudis’ estimates required ($68.77 billion, adjusted for inflation). Based on these numbers, it is clear that the U.S. will need to more than double down on NASA’s budget for the foreseeable future to have crewed missions ready to go by 2033. 

But perhaps we’re asking the wrong question. Instead of addressing if NASA will be ready to go by 2033, perhaps we should ask why NASA should commit to a 2033 launch date. Given the mechanics involved, launch windows are only available every 26 months (or during a favorable planetary alignment). But this leaves at least three opportunities before the 2030s are over. If key technologies are not likely to be ready by 2033, why not give them the time they need to mature and go later? 

According to an independent analysis by the Science and Technology Policy Institute (STPI), titled “Evaluation of a Human Mission to Mars by 2033” (2019), several elements will not be ready in time. This includes long-duration life support systems (LSS), 500-kWe-class SEP, cryogenic propellants, refueling, and reusability. 

They further anticipated that (even with a boost in funding) the DST would not be ready to depart until 2037 or 2039. Lastly, they stressed that parallel developments with the Artemis Program would likely complicate preparing for crewed missions to Mars. 

NASA is currently on track to have the core elements ready for the Artemis II and III missions (the SLS and Orion) and has contracted with commercial partners to develop all the additional elements – i.e., the Lunar Gateway, the Starship HLS, etc. As of 2018/2019, the DST and the Mars Base Camp are still in the study phase, and NASA has not officially proposed either mission to be included in an annual U.S. federal government budget cycle. 

Thanks to China’s recent announcement, NASA might have an added incentive to make 2033 a hard deadline. Similar to what happened during the Space Race, there’s always the argument that one’s own nation should try and “get there first.” However, it is highly unlikely China will be ready by 2033 either. Not only is China facing the exact same challenges, but its level of technological readiness is no greater than NASA’s. 

The race to Mars

To conduct missions beyond Low Earth Orbit (LEO), China must finish work on its super-heavy launch system – the Long March 9th (CZ-9). Whereas NASA has completed work on the SLS and Orion and validated both with a record-breaking flight test (Artemis I), China is still building the first CZ-9. 

Furthermore, China’s efforts to establish the ILRS may be complicated by the Russian invasion of Ukraine. In addition to economic sanctions, the ESA and other space agencies have responded to the war by terminating their partnerships with Roscosmos. Russia’s main launch facility, Baikonur Cosmodrome, was recently seized by the government of Kazakhstan because they've failed to honor their debts. 

This has thrown a wrench into many of Russia’s proposed space missions, which include sending robotic explorers to the Moon (the Luna program) and the development of the Angara-5 super-heavy launch vehicle. While there is little doubt that China can continue with the ILRS alone, losing a major partner will likely impose delays.

If there is no rush, wouldn’t a launch date of 2037 or 2039 be preferable, especially if it means that the mission crews get to perform all the lucrative research? Perhaps, perhaps not. At this juncture, only one thing is clear. Space agencies hoping to send crewed missions to Mars by the early 2030s will either have to double down on their budgets or settle for less ambitious missions.

Regardless of what they (and the taxpayers) decide, the payoff of sending the first humans to Mars will be worth the sacrifice. Whether that sacrifice means committing to more spending over the next decade or adopting a scaled-down mission remains to be seen. 

And who’s to say the political environment won’t change drastically in the next decade, allowing NASA, China, and other space agencies to pool their resources to send a crewed mission to Mars? A lot needs to happen between now and 2033, and lots of unforeseen developments will likely occur. It will be exciting to see what develops!