Visit Olympus Mons
Poster Art from SpaceX

The year is 2070.

Or 2080, or 2090, it really doesn’t matter, but it’s decades into the future.

Poverty is at an all time low. World population is stabilizing. Every human being in the world is connected to each other through a personal smart device. Robotics are integrated into every aspect of human life, reducing the need for manual labor. Humanity is reaching another Golden Age of creativity where the value of their artistry has increased due to the automation of everything else around us.

We have a base on Luna. We have established a colony on Mars.

Wouldn’t that be something? It doesn’t have to be a large colony. But it does have to have the basic requirements needed to allow for visitors.

In fact, let’s scratch that.

We have a multi-based network on Mars, all from different delegations or research teams or private companies, forming a large unified colony on Mars. There isn’t a high population there but it’s growing steadily and they’re making advances in building this community to keep on expanding.

You, an Earther in the future, are bored shitless out of your mind with your daily job. It’s an everyday grind with no end in sight. Wake up, go to work, go home, eat, sleep, repeat. If you’re lucky, you have enough time to exercise, have a hobby, a meaningful relationship or large social life. However, there’s a hollowness in you, something that the only planet you lived on can never cure. You need a way out, an escape, an adventure, something, anything, to leave reality. You need a vacation.

Tired as you return back home to Brooklyn on what would hopefully be a Hyperloop version of the L Train, you need something to distract your mind from this endless cycle.

And then you see a poster like the following from NASA being advertised in the Hyperway.

Visit Mars by NASA
Poster Art from NASA

Or this one from SpaceX.

Visit Mars by NASA
More Poster Art from SpaceX

When I first saw those posters being released to the public such as NASA’s collection of places to visit or SpaceX’s sightseeing tours of Mars, it amazed me how just those images could inspire in me a renewed sense of exploration. They’re definitely worth checking out. Shout out to the artists who drew them for such awesome designs.

Posters like those in 2080 (I’m assuming future tech will make posters more video like) would be common because of the inevitable privatization of space travel.

So, you find in you a sense of wonder that there are humans on another planet living and exploring, and you want to be able to see all that and visit it. It’s time you took a vacation. From your terminal, you book a ticket on the next space flight going to Mars and you start planning ahead for your trip.

Months later, you find yourself in the spaceport, waiting to be called to board the next spacecraft heading to Mars. It amazes you as you look out the window at all the preparations for launch how we even reached this far.

The good news is that even in the year 2016, even if we haven’t landed a human on Mars, we still have the technology to reach the planet.

In this article, I’m going to give a tiny overview of how we reach Mars. Think of it as a mini lesson on rocket science and history, with enough information that it’ll compel you, if you’re interested, to read more on the subject.

Table of Contents

  1. Part I: The History Behind Rockets
  2. Part II: How Do Space Rockets Work
  3. Part III: Saying Goodbye to Earth
  4. Part IV: Saying Hello to Mars

Part I: The History Behind Rockets

Have you ever seen a spacecraft launch? I’m sure a lot of us have, being in the certain time where all information and data is accessible to us. But, did a rocket launch ever make you wonder how any of it was even possible.

There must be a million variables at play when considering a rocket launch, from every line of code for the launch software, every screw in place, every personnel running diagnostics and preparing in anticipation, every penny being allocated in the hope that this mission is a success. To witness such an event every time is a testament to where we are as a species, a measurement that we can use to estimate our level of intelligence compared to other intelligent beings elsewhere (statistically speaking, of course).

Our ability right now to technologically escape our planet and go to the Moon is a benchmark that we can use to show how advanced we are, or how much longer we still need to go before mattering much. Nevertheless, right now this progress is still in its infant stage, like a toddler going from a crawl to a walk, or a tribe that just invented the wheel and not foreseeing what the future for it could hold. Rockets are not a very recent invention, as much as we would like to think they are. Like the discovery of Mars, it isn’t known exactly when rocketry was invented.

Take this guy, Archytas, for instance. An ancient philosopher born in 428 BC in Tarentum, Magna Graecia, Archytas came up with the invention of the Flying Pigeon as seen in the figure below.

Flying Pigeon
Flying Pigeon of Archytas

The flying pigeon was made out of lightweight material with a hollow cylindrical shaped body. The rear of the of the pigeon was connected to an internal bladder, which in turn was connected to a heated boiler. The more the heated boiler burnt and created steam, the more that steam will fill up in the bladder and inside the cylinder of the pigeon, until the pressure created by the steam would exceed the mechanical resistance between the connection, allowing the pigeon to fly.

And fly it would, up to 600 feet away! The nerd in me really likes this early invention because historians have thought of Archytas’ pigeon as the first robot. Think of how far we have come from this very first robot.

If we travel further East, we can examine an interesting relationship the Chinese had with rocketry. It has been reported that in the first century A.D., they had a simple form of gunpowder. According to NASA, during religious festivals, they would toss bamboo filled gunpowder in the fire to create explosions. It is in those celebrations that one might guess that rockets were discovered by accident, since some might have failed to explode and instead skittered out of fires.

NASA points out that the Chinese began experimenting with the gunpowder-filled tubes. At some point, they attached bamboo tubes to arrows and launched them with bows. Soon they discovered that these gunpowder tubes could launch themselves just by the power produced from the escaping gas. The true rocket was born.

Chinese Fireworks
Ancient Chinese Fireworksfrom Buzzle

I sometimes wonder if there’s a connection between their accidental discovery of rockets and their belief in dragons. I could be wrong and there’s no relationship, since I’m no expert on ancient China. I just love dragons. Anyways, moving on.

Enough of the ancients for now and let’s fast forward to somewhat modern times, to 19th-20th Century North America. The space rockets of today owe much of their design to U.S. physicist Dr. Robert Hutchings Goddard (1882-1945). If that name feels familiar, it’s because NASA named their Goddard Space Flight Center, which was established in 1959 in Maryland, after him. Dr. Goddard is known as the “father of modern rocketry”, a pioneer of U.S. rocket propulsion which aided the U.S. in the Space Race.

Dr. Goddard
Dr. Robert Hutchings Goddard

A genius ahead of his time, his devotion for construction and successfully testing rockets using liquid fuel went largely unnoticed by government officials, and he only managed to stay afloat through modest subsidies from the Smithsonian Institution and the Daniel Guggenheim Foundation. According to NASA, he was the first scientist to not only just envision the possibilities and potentialities of space flight with rocketry, but he also had an active role in practically bringing that vision to life. He had this rare talent of being both a creative scientist and a practical engineer, yet his work and tests and contributions to space flight would be largely unnoticed till after his death, right at the beginning of the Space Age.

I also think that having a last name like “Goddard” is a benchmark of badassery, but that’s a side note.

Now, I hope in future space rocket flights to Mars that are carrying passengers and tourists aboard, the space flight company would have all this above information in a pamphlet or something. It’s not just because appreciating the history of the rocket is important for people flying in it, but because it must be ingrained into us to the point that a child would know who Goddard is the same way a child today knows who the Wright Brothers are.

As the technology becomes mainstream, so should our appreciation for its inventors. But in the case that this future space flight company you’ve bought your ticket with doesn’t have that information on a pamphlet or somewhere else (SpaceX totally would have that pamphlet), then bookmark this article and hope it can be found decades from now.

Part II: How Do Space Rockets Work

Space rockets work on a simple law written centuries ago, but to further appreciate the struggle that it took to be able to apply that law right now in the modern world, we need to make a quick stop in 17th century Cambridge University.

I know what you’re thinking, “Fuck history, man”, but it’s going to get better. Back then, a recluse that goes by the name of Isaac Newton, being recently burnt by his enemy Robert Hooke, was devoting his time to his studies and discoveries, wanting no outside contact with the world whatsoever, because of his trust issues.

Hooke was a total douchebag who humiliated Newton and kept stealing his invention, even though he came up with Hooke’s Law, which no one remembers or cares for from high school physics. You can’t beat Newton’s Three Laws of Motion, guy.

Isaac Newton
Isaac Newton

At that time, astronomer Edmond Halley -- a name we use to this day thanks to his prediction of the appearance of Halley’s Comet -- had a question that he greatly wanted to answer.

From his observations and looking up at the cosmos at night, he noticed that planets which are closer to the sun orbited it faster than those that were away from it. He wanted to know why that was the case. When he approached Newton with that burning question that’s been haunting him, Newton informed Halley that he solved that equation years ago.

Orbital Speed of Planets
Orbital Speed of Planets

Amazed by Newton, and finding out about all those other discoveries that Newton had in his study, Halley urged him to publish his works. Halley became Newton’s patron, and without his support for Newton’s works, which were published in a book called the “Philosophiæ Naturalis Principia Mathematica” or simply Principia, the world wouldn’t have seen the invention of calculus or the discovery of gravity.

Sure, some one later on might have come across and made those discoveries, but no one can predict when that would happen.

Philosophiæ Naturalis Principia Mathematica of Isaac Newton

It is thanks to Newton and his Third Law of Motion that we can escape Earth and into space. For all of you who haven’t been paying much attention back in high school physics, Newton’s Third Law simply states that “For every action, there’s an equal and opposite reaction.”

It’s a general mistake to think that rockets would work by pushing back against air, when there’s no air in space! In the simplest terms, Newton’s Third Law helps rockets escape Earth’s atmosphere by the action created when the rocket engines generates lots of hot gases that are firing away. This in turn creates the reaction that is equal in the opposite direction, pushing the rocket away from the force exerted by the hot gases.

If that seems hard to grasp, then I want you to think of a few things you’ve experienced before. One is a balloon you’ve just inflated, but once it has enough air inside it, you let go of the neck, letting the air escape. The movement of the air balloon as it rises and falls and moves around the room is essentially a poor man’s rocket.

Another example of action-reaction is the recoil from firing of a shotgun as you’ll see when you Google shotgun recoil gifs. The large kick from the shotgun onto your shoulder after you fire it is the reaction part of Newton’s Third Law.

One other way we can look at this if we think of ourselves as astronauts on a future space station (or we can just consider the International Space Station if you don’t want to do a lot of visualizations).

NASA astronaut Greg Chamitoff during a 2011 spacewalk on the International Space Station.

If you’re the astronaut performing your EVA activity and you happen to bring a baseball with you, cause hell, you wanna throw that bad boy out into the black, you might wanna rethink that idea first (depending on how strong a thrower you are). Newton’s Third Law applies here too. You throwing that baseball out into space will cause you to move in the opposite direction, so you better be strapped as close to the space station in case you go drifting out.

This is all due to the force of your throw having an equal opposite effect on where you move opposite of your throw. Force here is a product of mass multiplied by acceleration, or F = m * a. If the baseball’s mass is about 0.5 kg and your body and suit will weight about 100 kg. You accelerate that baseball from zero meters per second speed to 30 meters per second as you throw it out into the open space. The Force you exerted on it was 15 Newtons. The reactionary force, due to you having a larger mass than the ball, resulted in a reactionary acceleration from zero meters per second to 0.15 meters per second.

This is where things get interesting. Let’s say you want to increase the thrust of the baseball force, then you can increase the mass of the ball or the acceleration. The increase in thrust will have a more noticeable reactionary force on you, resulting in a more noticeable difference in the reaction. So, if the weight of the baseball remains at 0.5 kg but you throw it at a regular speed of a bullet, at 450 meters per second, resulting in 225 Newtons of Force exerted on that baseball. Now, the reactionary force exerted back on you will result in you flying at 2.25 meters per seconds in the opposite direction!

Rocket engines behave generally the same way as the astronaut in space with a baseball scenario, where the mass that they are throwing out is in the form of high pressure gas. The mass comes from the fuel being burnt, where the burning process accelerates it quickly so that it comes out of the nozzle at a much higher speed.

Test Engine
A space rocket engine being tested

Thrust is a measurement of how strong a rocket is, in a formula of T = v * dm/dt, where v is the velocity and dm/dt is the rate of change of mass with respect to time. If that seems confusing, then let’s consider this scenario.

You’re an astronaut doing an EVA outside the International Space Station, and since you are bored and want to play a game, you bring with you a huge bag of paintballs and a paintball gun. Let’s say that you are aiming your paintball gun at a target you marked earlier to see how many paintballs you can hit on point on that target (we will try to leave Dextre and other robots in space alone). You weigh 100kg with the suit included, but now your bag of paintballs adds 50kg of weight to you, and each paintball is 1 kg in mass (for the sake of the example, assume there are 1 kg weight paintballs). By shooting one paintball at the target at an acceleration from zero meters per second to 10 meters per second (acceleration of gravity is 9.8 meters per second, but let’s stick with 10 for the sake of a clean number), you will be generating 1 Newton of thrust. If you were to shoot another paintball at double the acceleration, you will be generating 2 Newtons of thrust. The more mass that you are releasing by shooting at the target and accounting for the change in mass that you have in your paintball bag, the higher your thrust becomes.

Rockets before launch have a major requirement where their thrust must be higher than their weight. For instance, the Space Shuttle has a thrust of 29.4 MegaNewtons compared to its mass of 2,040,000 kg at lift-off. The majority of the weight will come from the fuel, which makes your weight as a passenger almost insignificant. The fuel of the Orbiter on the Space Shuttle weighs 20 times more than the Orbiter itself! For further reading and understanding, you can check out the Operator's Manual

Space Shuttle getting ready for liftoff

Early models of the rocket used what was called a solid-fuel rocket. It was an easy design to build, but solid-fuel had its drawbacks. The main problem consisted of it being impossible to control. Once you ignited it, that baby is burning and there is nothing to stop it.

Solid Rocket Fuel
Design of Solid Rocket Fuel Tank

Liquid propellant rockets are more complicated than solid-fuel rockets in their designs but offer more advantages. The way they work internally can be demonstrated with the following diagram. In its simplest form, liquid propellant rockets work by making a mixture of oxygen and fuel in a combustion chamber, which will be ignited to create the high pressure gas that is released from the nozzle. It is very common to have a liquid form of oxygen or hydrogen.

Liquid Rocket Fuel
Design of Liquid Rocket Fuel Tank

However, one of the main disadvantages in the liquid propellant design is the cooling the combustion chamber and nozzle, so what happens is that the cryogenic liquid is first pumped and circulated around the extremely hot parts to cool them. Furthermore, the pumps have to generate extremely high pressures in order to push back against the pressure created by the burning fuel in combustion chamber.

All this added complication for the desired efficiency in designs results in early engine designs being a complicated network of different pipes all over the place, like the following engine here.

Liquid Rocket Engine Old
An F-1 engine on display at NASA's Marshall Space Flight Center.

Overtime however, the design has improved, such as the following Merlin engine built by SpaceX.

Merlin Rocket Engine
The SpaceX Merlin Engine

Part III: Saying Goodbye to Earth

By now, you’re done reading all about the new features of the current spacecraft you are in. You cross your fingers and hope for the best as you get strapped in to your seat and await the countdown to lift off.

When you see a spacecraft launch, you have to keep in mind that it isn’t launching straight up into the atmosphere. Bear with me here.

When a spacecraft launches, it’s exiting Earth’s atmosphere in a curve. The reason for curving is because of our good friend, Isaac Newton.

Back in the days, Isaac Newton described the idea of orbiting a planet by envisioning a really tall mountain on Earth. And by tall, I’m talking Olympus-Mons-ain’t-got-shit-on-me tall. Now, Newton envisioned as well that a cannon stood at the summit of this really tall mountain, let’s name it Mount Too Tall for now.

When the cannon is fired from the summit, we would see the cannonball following its ballistic arc until it lands back on Earth due to gravity. That’s A in the figure below. Not good enough, huh?

Let’s add more gunpowder to this cannon. We would notice when we fire the cannon this time that the cannonball travels faster and further away, yet it will fall back on Earth at the same rate as before when it had less gunpowder. That would be B in the figure below.

Now, let’s juice it up a bit and add a more insane amount of gunpowder to our cannon. This really pushes the cannon to go more further and faster in its ballistic arc, but since it is going at a much higher rate than before, it falls completely around Earth! This cannonball is now in free fall. We can say now that we have achieved orbit. We are at C now.

Cannonball newton
A diagram of Newton's cannonball

This is exactly how we perform spacecraft launches.

All launches happen in stages, or what we call a multi-staged flight. Remember the bit about a spacecraft launch when it felt like parts of the rocket where being detached during the flight and fall back to Earth? That’s a stage of the spacecraft launch being complete.

Let’s use the Saturn V as an example (it’s a damn sexy looking spacecraft, isn’t it).

Satun Aerial
Saturn V rocket

The first stage is what we can think of as a lot of fuel used to escape Earth’s atmosphere. The first stage can produce 7.5 million pounds of thrust, allowing the rocket to perform that curved launch to reach orbit.

At an altitude of 67 kilometers, here’s when things get really interesting. We first witness the interstage separation and the second stage begins operation. Why do we detach the first stage from the rocket?

It’s because it carries dead weight since all the fuel has been burnt in getting us to the 67 kilometers altitude. Since as we discussed before, we like to avoid all unnecessary weight when launching, best thing to do is shred of that extra fat, baby.

Destaging Saturn
Saturn Rocket Stage Separation

By the time the second stage starts its burn, at about 9 minutes into the launch, the second stage is separated from the Rocket and detached. Third stage comes into play, with one engine. When it gets cut off, the spacecraft has reached a speed of about 17,432 miles per hour and is in orbit around Earth at an altitude of 118.8 miles. Since we have reached the free fall orbit we wanted, we completely shut off the engine, saving on the fuel.

Shuttle Orbital Curve
Space Shuttle Launch

As we launch into space and reach the highest point of our orbital path, the apoapsis, we adjust the spacecraft’s direction with a little fuel to be able to form an ellipse orbit around the planet.

To better visualize what is going on, I took the liberty of screenshotting Ruairi Walden's videos of achieving orbit around Earth using Kerbal Space Program (also happens to be one of Elon Musk’s favorite video games). This was purely done for visualizing the orbital path achieved during launch.

As the rocket launches into space, such as the one shown here:

KSP Rocket
Kerbal Space Program Rocket Launch

It’s launching in a curve towards the apoapsis, or the highest point in its path, as shown in the following screenshot from a simulation in the game.

KSP Apoapsis
Kerbal Space Program Rocket Launch Apoapsis Lapse

Why do we care about the Apoapsis now? What does it do for us?

Remember Newton's cannonball and Mount Too Tall? That's the elevation we want to reach with our rocket, which is why we are approaching our apoapsis, since it represents the summit. Since it’s reaching the apoapsis on its orbital path, we can safely cut off the fuel to save it since we are already travelling at a high speed. We wait until we reach the apoapsis, as shown in the following screenshot.

KSP Apoapsis Closer
Kerbal Space Program Rocket Launch Apoapsis Closer

Now that we reach the apoapsis, by applying more energy over there, we will have increased the altitude of the periapsis, or the point lowest altitude in the ellipse orbit. That's the same as Newton's cannonball and Mount Too Tall, where we add just enough gunpowder to get the cannonball to continously fall around Earth, thus orbiting Earth. We couldn’t have seen the periapsis before in our ascent to the apoapsis since we would have collided with Earth before getting there. We apply energy at the apoapsis to get a nice elliptical orbit as shown below.

KSP Orbit
Kerbal Space Program Rocket Orbit

The opposite of this is also valid. If we decrease the energy at the periapsis, we will lower the apoapsis altitude as well. If we think of the cannonball passing through a forest as it flies through the periapsis, the decrease in energy would slow it down, not allowing it to climb that high an altitude as if the forest wasn’t there. At the periapsis, one way to remove energy while in space would be through aerobraking, which is the careful dip into a planet’s space, which we will cover later here when we get to Mars.

A better view and understanding of the periapsis and the apoapsis is shown in the image here.

Apoapsis and Periapsis
Apoapsis and Periapsis

The target altitude we look for in space orbitals is 150 kilometers off the surface of the Earth. The reason is that over there, the atmosphere is so thin that frictional drag isn’t a problem at all. Fun Fact: Our current altitude of 150 kilometers off the surface of Earth is one millionth the distance from the Sun to the Earth, or 150 million kilometers, better known as One Astronomical Unit, or AU. When in freefall, you don’t need to use fuel at all and save a lot on it, using it only when you want to make minor adjustments to your orbital path. In fact, you can remain in your orbital freefall for months or years, until your orbit starts slowly degrading because of the presence of thin atmosphere.

By now, as you are strapped in your chair and you are orbiting Earth in the spacecraft, you might at first sense a feeling of euphoria from witnessing how beautiful our home planet is.

Earth from ISS
Earth as viewed from ISS

You will also notice the sensation of weightlessness, as if gravity is no longer present. That is in fact not true, as gravity might be a little weaker at the height of a 150 kilometers above Earth, but it is still very present and it is the reason that the spacecraft is orbiting Earth.

The reason for feeling the weightlessness, however, is because of the free falling of the spacecraft around Earth. Think of that feeling this way. You are on a roller coaster and you’ve reached the highest point in its ascent on the tracks before slowly falling down, making you feel weightless, like you’re falling. Now that you are enjoying the sensation of freefalling in the spacecraft, the captain announces the next stage of the journey, which is Mars.

Part IV: Saying Hello to Mars

Mars or bust, baby!

I kid. Landing on Mars reminds me of a quote by a great man.

Mars Nebula
Derek Demeter's photograph of Mars between two nebulas
"I’d like to die on Mars. Just not on impact"

- Elon Musk

There are a lot of things that go into planning a trip to Mars, so it’s not like a trip that you can plan last minute. There are so many things to consider here.

One of the main chief things to consider here is the minimization of the mass propellant. If you don’t have a Science to English converter on you right now, then what I’m talking about is fuel here. It’s not efficient for us to travel to Mars when it’s on the other side of the sun in its orbit. That is a terrible waste of fuel, making the mission significantly more expensive. Whoever approves a mission like that would be the main feature of a Harvard Business School case study of how NOT to manage a multi-billion dollar project.

Since we are in orbit now around the Earth, I’d like you to assume a few things here. We must assume that the spacecraft that is launched carrying you is already in solar orbit.

Earth Mars Orbit
Earth and Mars Orbit

At this point in your flight, you’re probably thinking that the next step would be to wait until Mars is in front of our spacecraft and we can just “aim and shoot” over there in a straight line. You would be forgiven for thinking that, since that would be the way NOT to go to Mars, or any other celestial body for that matter.

Let’s say the spacecraft you are on still hasn’t departed from Earth and you finally have Mars right in your path. If you launch from Earth and aim straight “point and shoot” at Mars, Earth’s gravity will bend the trajectory of your spacecraft.

If you want to get rid of that bending from Earth’s gravity, let’s say you are already in orbit like we are right now around Earth and then decide to aim and shoot to Mars. We still have to think about orbital speed of our spacecraft around Earth, due to the fact that not only is the rocket orbiting Earth, we are also orbiting the Sun! We will call our orbital speed V0. Those two factors will give us an orbital speed that is transverse to the direction aimed at Mars.

Because of that, if we fire towards Mars, we will end up at a trajectory different than the one we had in mind, and Mars would be located somewhere else, moving on and forgetting about us.

Earth Mars Orbit Closest
Earth and Mars Orbit at their closest approach

Needless to say, Team Point-N-Shoot won’t work for our journey to Mars.

Instead, the way that we get to Mars is rather elegant, at least in my opinion. Also, it is definitely more efficient. We have to look for an orbital path, one that will take the spacecraft from Earth to Mars at a destination where by the time we arrive at the Martian orbit, Mars will be there waiting for us.

To do that, we will be using Hohmann’s Transfer to achieve this maneuver, proposed by a German engineer named Wolfgang Hohmann back in 1925.

Aphelion and Perihelion
Perihelion and Aphelion of Earth

How does the Hohmann transfer work, exactly? First, we need to keep in mind that an orbit around a sun is an ellipse. In other words, if you imagined it to be a perfect circle, then you expect too much of our universe.

With an ellipse in mind, we need to look at two points in an elliptical orbit of a planet around the sun, the perihelion and aphelion. From the figure above, you can see those two points in relation to Earth’s orbit. The perihelion is the shortest point in the elliptical orbit from the sun while the aphelion is the furthest point from the sun.

Hohmann Transfer Animated
Hohmann Transfer Ellipse

Remember back in the previous part, where we said that, in order to increase our apoapsis altitude when orbiting Earth, we must increase energy at the periapsis. Well, this is what we are doing now. As you sit back in your spacecraft waiting for some sort of action to happen while you are orbiting Earth, you will at some point notice the spacecraft firing its rockets again to adjust its trajectory.

We are increasing the energy at the periapsis to have a higher altitude at the apoapsis, or what happens in the first step of the gif above after the rocket completes its first orbit around the planet.

The new trajectory that will form an ellipse will consist of two points, which we talked about earlier, the perihelion and the aphelion. The perihelion in this new ellipse orbit will be Earth’s orbit while the aphelion will be Mars’ orbit. So many variables too keep in mind!

Now that we have fired off in the new trajectory of the ellipse towards Mars’ orbit, if you look at the gif, the rocket seems to turn around back to orbit Earth in a secondary orbit. In space missions to Mars, we don’t orbit Earth again when doing the Hohmann transfer, since we expect Mars to be in place on its orbit when we reach the first half of our elliptical orbit. The gif is just demonstrating the second elliptical orbit for you to visualize it.

Orbit Transfer
Earth and Mars Transfer Window

Now that you reached Mars’ orbit in your Hohmann transfer and Mars is there, you can hang back and orbit Mars like some of the probes do as they study it. But what’s the point to travel all this way if we aren’t going to land on Mars?

To be inserted into Martian atmosphere, we need to arrive on Mars at exactly the right time that it’ll be there, along with all the other factors we discussed. This is very hard, but not impossible. NASA compares it to aiming a dart at a moving target. Think about it this way. We always hear about an opportunity window to launch to Mars, when things are good. That happens once every 25 months, so missions prepared to Mars always have to wait for that opportunity window.

InSight Lander
InSight Lander solar arrays being constructed

To give you an idea of how important that opportunity window, a few months back, NASA had to delay the launch of its InSight lander because of problems with its seismometer. Plans were for a launch in the 26-day window opening on March 4th, but issues have caused a push back. Because of the 26 months opportunity window, NASA is looking at a May 2018 timeline for another launch.

You are nearing the end of your Hohmann Transfer, and as you have your breakfast on the spacecraft, the pilot announces that we will be inserting into Martian atmosphere. You quickly lookout the window and this is the view you see.

Mars Aerial
Aerial view of Mars and Olympus Mons

To be locked in Martian orbit, we must then decelerate relative to Mars using a retrograde rocket burn. Insertion in to the Martian atmosphere will require some retrograde rocket doing further deceleration so that the lowest point of our spacecraft’s orbit will intercept the surface of Mars.

Parachutes are often used to slow down are our landing onto the planet. Most spacecrafts, like the Curiosity, used parachutes and retrograde rockets to descend into Martian atmosphere.

Curiosity Landing
Steps in Landing the Curiosity Rover

Retrograde rockets provide a lot of advantage for a human landing on Mars, because they can be reused to exit Mars’ atmosphere and head back to Earth.

By now, as you land on slowly on Mars and wait for the all clear from your captain to start putting on your Martian suit and exit the spacecraft, I want you to imagine what a society like the one on Mars would be like.

What kind of culture would the people living there have? Do they have any sort of entertainment that can be performed in a lower gravity? What about the research? The architecture of the bases?

Martian Base
A Base on Mars

One of the few things I want to explore in future posts is the different approaches to cohabitations and bases and colonies that can occur on Mars. For those, I also want to use examples from the real world and those from fictional work.

Either way, now that you have safely arrived on Mars, you might want to stop reading this post and go help your roommate with his potato farming.