Why is it so difficult to get to Mars?
Note to speaker: Do not pronounce what is marked in yellow, are notes to the editor.
In addition to Earth, Mars is the planet with the best conditions to host humans. Space agencies
such as SpaceX or NASA are planning to take the next generation of astronauts to the red planet,
but it has not yet been achieved, Why is it so difficult to get to Mars?
let's start!
During the space race in the 60s, NASA successfully took six missions to the moon that
placed 12 astronauts on the surface of our natural satellite. Having gone to the moon several times
nearly five decades ago and is used to seeing astronauts travel to space almost routinely,
having extended stays on the International Space Station, it's tempting to think that sending
humans to Mars could be perfectly plausible today. However, to the current date, in 2022, seeing the
first humans on the red planet still seems to be distant. Science and technology tell
us that sending human beings to Mars constitutes a challenge of enormous difficulty and complexity
that is far from everything that has been done so far in the history of human exploration of space.
But the reason almost all others are derived from is one: distance.
Mars is far away We see astronauts
frequently travel to space, to the International Space Station (ISS); before that, for years,
cosmonauts traveled to the Mir station aboard Soyuz ships, and currently, taikonauts travel
frequently to the Tiangong space station in China. Popularly one has the impression that the place
to which one travels in these missions is very distant; however, the typical altitudes at which
these stations and spacecraft orbit Earth are a few hundred kilometers. The ISS, for example,
orbits the Earth at an altitude that is equivalent to the distance in a straight line between Madrid
and Almeria: about 400 km. This space region to which humans routinely travel is within
the so-called "region of low Earth orbits," and technically, we call it LEO (Low Earth Orbit).
Lunar manned travel involves traveling beyond LEO orbits since the Moon orbits our planet at
an average distance of about 380,000 km, which is about 1,000 times farther than the altitudes
of these low orbits. A crew and their spacecraft are put into orbit around the Earth shortly after
launch, while the distance to the Moon was covered on the Apollo missions in about three days.
In the case of Mars, the situation is very different. Going to Mars involves moving from
a geocentric mission to a Sun-centered orbit, or heliocentric, which is a massive leap in the
distances involved. Although the maximum and minimum distances between Earth and Mars vary
within a specific range, the minimum possible distance is about 55 million km; this distance
is achieved every 26 months when Mars and Earth have an approach gap that lasts a few weeks.
These are huge distances compared to all manned missions to space so far.
The maximum distance to Mars is 1,000 times greater than that between the Earth and the
Moon and approximately 1,000,000 times greater than the distance separating
the Earth's surface from the LEO orbits to which one travels typically, in other words,
a single trip to Mars is equivalent to 1 million trips to the ISS space station.
Without needing to know anything else, the data about the distance to Mars
already constitute an excellent clue to glimpse the magnitude of the problem.
To appreciate it better, and without going into details related to propulsion methods or orbital
dynamics, we will compare two human-crewed missions in round numbers: An orbital mission
around the Earth for a single crew member and a lunar mission for three crew members.
We start with the first orbital mission of the Mercury Program of the early '60s: John Glenn's
Mercury 6. In this mission, a 120-ton Atlas rocket was used, with a height of 29 meters, it managed
to put a useful mass of 1.2 tons into orbit at an average altitude of 200 km around the Earth,
the cargo was a Mercury capsule with its only crew member, who remained in space for 5 hours.
Let's see what changes the situation by having the Moon as a destination about
1,000 times farther away. In the case of Apollo 17 -the last lunar exploration mission-its command
and service module plus its lunar module, adding everything are about 50 tons, were launched to
the Moon by the mighty Saturn V rocket of about 3,000 tons and 110 meters high for a mission of
a total duration of about 12 and a half days in which 2 of its crew remained on the lunar surface
Just over three days. In contrast, the third remained inside the ship throughout the mission.
We see that the quantitative leap needed when we want to go to another
world that is 1,000 times beyond the low orbits of the Earth is enormous.
On the one hand, the useful load to be launched happens to be 1.2 to 50 tons, while the size of
the launch rocket goes happens to be 120 to 3,000 tons. Compare all this to a mission to Mars.
For a mission to Mars, the crew will consist of 6 astronauts, and its duration,
taking as an example the approaching gap in 2037, would be 174 days for the outbound and 201 days
for the return, with a stay of 539 days on Mars. Such an extended stay on Mars would be necessary
for the hope that the relative position between this planet and Earth would be optimal for the
return with minimal fuel expenditure, which saves the shipment of hundreds of tons of fuel.
This represents 914 days of stay on the red planet or approximately two and a half years.
As we can see, the jump between the Moon and Mars is enormous since doubling the crew and extending
the duration to about 73 times that of the longest lunar mission means the need to provide and
transport about 150 times more supplies. On the other hand, a longer duration of interplanetary
travel means the need to provide the crew with more excellent protection against radiation,
which is achieved in part by adding even more mass to the ships;
currently, this problem is not entirely solved. Another problem with long-lasting is that things
break down for so long. Either the durability of the equipment will have to be substantially
improved, or they will have to be able to be replaced by spare parts that will also have to be
transported, which implies a greater mass. Cargo spacecraft visiting the ISS can stock up on spare
parts when something goes wrong on board, but this option will not be possible on a mission to Mars;
anything that can break will have to be repaired or exchanged for the same parts on board.
Tons of Fuel for a single trip Experience tells us that braking a train is
much more complex than braking a truck because the former has more mass and therefore needs more time
to brake. Sending more mass to Mars also means transporting more fuel to accelerate all that
cargo to Mars, but it also means carrying more fuel to stop when the ship reaches the planet,
in addition to all the fuel necessary to return to Earth;
We are talking about hundreds of tons of fuel that we will have to carry to Mars in some form.
One option that some scientists propose is to use the minerals and gases trapped in the subsoil of
Mars to produce fuel, but so far, no system has been tested that can do this, so until
we prove that something like this is possible, the only option will remain to use our fuel.
And for the distances we've talked about, as well as for the round trip, in total,
the Mars mission will require carrying between 850 and 1,250 tons of fuel.
This is a massive amount if we consider that the ISS has a mass of about 420 tons and that a ship
with which we are familiar, the Space Shuttle, could only send into space between 15 and 25
tons approximately, depending on the altitude of the final orbit. The Ariane 5 can put about
20 tons in low orbit around the Earth, like the Russian Proton rocket; with the most powerful
ships of the time, taking all that fuel into space would take us about ten trips at least.
Thus, we can already intuitively anticipate that a single rocket will not be able to be
used to go to Mars but that several rocket launches will be required – as powerful or
more powerful than the Saturn V of the '60s – to assemble in space different propulsion elements,
fuel modules, habitats, and ships, which will have to be sent to Mars separately and
in advance. In addition to the spacecraft with the crew, which would be sent last.
Although it depends on various factors, they will require, in fact, ten rocket launches with the
capacity of the Saturn V or similar; but recall, l the total number of Saturn V rockets sent to
the Moon in the entire Apollo Program was 9. The Saturn V was retired from service after the
Apollo Program but holds the record, even today, as the most powerful operational rocket ever,
capable of putting just over 120 tons into low orbit around the Earth and sending 50
tons to the Moon. It had to be specifically designed and built in its day to reach the Moon.
The only rocket capable of dethroning the Saturn V could be the SLS rocket (Space Launch System),
which will have a similar or perhaps somewhat superior performance than the Saturn V.
The effects of weightlessness A time of 539 days out in weightlessness
profoundly affects human physiology, especially worrying when arriving on a planet where no one
can assist you. The ships that can be seen in the movies, with spacious and comfortable
cylinder-shaped cabins rotating to simulate the acceleration of gravity, do not exist today,
so astronauts who go to Mars will suffer from weightlessness throughout the mission,
it is not yet known precisely how they will recover when they reach Mars.
For psychological reasons, two and a half years is a very long time. Earth will be seen by the
crew as a star-like point of light for most of the voyage and barely noticeable on Martian night. The
crew will have to live in a condition of permanent confinement in a small space in a situation of
great stress and with the impossibility of maintaining fluid conversations with loved
ones on Earth due to the signal's travel time. Remember that radio signals travel at the speed of
light, which is the speed limit in the universe. Still, even at that speed, communications have a
delay of 8 minutes between message and message due to the enormous distances the signals must travel;
conversing with a loved one in real-time from Mars will be practically impossible.
To these problems must be added all the technical, technological, and operational
difficulties involved in taking a human-crewed ship to such a remote place. No human being has
ever experienced a journey of such large. The astronauts will spend months
in weightlessness, subjected to radiation from interplanetary space.
Once on Mars, they will face other challenges that are very difficult to overcome, such as
the fact that they will be locked 24 hours a day in a cabin probably equal to or even
smaller than the ship they used to get there. Although some enthusiastic and optimistic
people about interplanetary travel say that humanity already has the technology
and everything it takes to go to Mars, science tells us that we are not ready yet.
The difficulties and challenges that arise from interplanetary travel are still considerable
and difficult to overcome, but we may have the technology to achieve it. we only need
the budget and time to plan things well. NASA has estimated that with modern science
and technologies, it will be possible to take the first humans to Mars before the
end of this century; others think that, in reality, there is much more to be done than
that and the most optimistic think that it will be achieved in the coming years.
What do you think? Do you think we will be able to get humans to the moon very soon,
or do we still have many problems to solve? Let us know what you think in the comments of this video.