On September 27, 2016, the world changed forever.
Elon Musk, the man behind PayPal, SpaceX, Tesla, and SolarCity, unveiled an ambitious game-changer plan that will make us an interplanetary species. As climate change levels rise and finite resources are being consumed, which will eventually make Earth an uninhabitable planet, we must find ways to colonize other planets and make them suitable for life.
If the words “interplanetary colonization” come to mind, the first thing you would probably think of is Mars. Mars is our closest neighbor in the Solar System and evidence from NASA’s MAVEN probe indicates that it used to have an atmosphere and a magnetic field, which was slowly stripped away by the solar wind over time. Because of this, terraforming Mars (transforming a planet so that it somewhat resembles Earth) is considerably much easier than terraforming other planets.
The only question is whether we can do that affordably or not.
Even though we have sent many missions to Mars over the past several decades, the cost for sending stuff to Mars is ridiculously high. For example, the cost for the MSL (Mars Science Laboratory, also known as the Curiosity rover) mission was approximately $2.5 billion. How are we, a species numbering over 7 billion, going to terraform Mars if the cost of sending something smaller than a Jeep will burn a hole in the economy?
SpaceX aims to change all of this.
Born in a suburban Los Angeles warehouse in 2002, SpaceX has quickly proved itself to be one of the world’s most successful launch providers. By building everything in-house and developing a partially reusable capability on its Falcon 9 rockets, SpaceX was able to lower the price of launching satellites (particularly heavy communication satellites commonly known as “commsats”) by more than 50%. Musk stated that the reusability capabilities currently developed by SpaceX will “revolutionize access to space” and is the key to “making human life multi-planetary.”
But how will they do it?
Enter the Interplanetary Transport System (ITS), essentially a very large rocket stage topped by a very large spacecraft. The ITS is big enough to carry as many as 100 people to Mars and beyond.
The ITS is composed of three components: the ITS launch vehicle, the Interplanetary Spaceship, and the ITS tanker. All three components work in tandem to make humans an interplanetary species, 100 people at a time.
The ITS launch vehicle is a super-heavy launch vehicle that will be powered by 42 Raptor hydrocarbon-fueled engines. The booster is 39 feet in diameter, 254 feet tall, and will be capable of holding up to 6,700 tons of densified liquid methane (the fuel) and liquid oxygen (the oxidizer). 28,730,000 pounds of thrust (approx. 130 MN) will power the booster and the spacecraft off the launch pad, and the booster will have the ability to fly back to its launch mount using advanced navigation technologies, similar to the Falcon 9.
In a sense, the Interplanetary spacecraft will function as the second stage of the ITS. Six vacuum-rated raptors (basically a raptor with an extended nozzle that will make it more efficient in a vacuum) and three regular sea-level raptors will lower the second stage, giving it a total of approximately 7 million pounds of thrust. The spacecraft will first fire its engines to reach a parking orbit, which will consume most of its fuel reserves.
How are we going to get to Mars with only a few minutes of fuel left?
The ITS tanker is spacecraft essentially a modified Interplanetary Spaceship with the crew compartment stripped and extra fuel/oxidizer tanks installed in its place. The tanker will rendezvous with the Interplanetary Spaceship in Low Earth Orbit (LEO) and will replenish its fuel reserves. The tanker will then conduct a de-orbit burn in order for it to land back at its launch site, while the Interplanetary Spaceship will conduct a trans-Mars injection (TMI) burn to put it on a trajectory that will intersect Mars. Depending on the planetary alignment window, which takes place approximately once every 26 months, it could anywhere from 80-150 days to arrive at Mars.
This might seem like a very expensive concept, and will likely cost many billions of dollars for development, but the ultimate goal set by Musk is to bring the cost down so that each person willing to go to Mars will only have to pay $100,000-$200,000 for the trip.
The key to the lower prices, according to Musk, is reusability. After each launch, the ITS booster will conduct a series of propulsive manoeuvres using a subset of its 42 engines to fly back to the launch pad. While in the atmosphere, three grid-fins will deploy to steer the booster to a precise landing on the launch mount. All of this will utilize about 7% of the propellant in the first stage booster. According to the official introduction video released by SpaceX, a crane will then lift a fully-fueled tanker on top of the booster while ground support systems replenish the fuel load on the first stage. The booster will take off again once the rendezvous window arrives, putting the tanker on course to dock with the Interplanetary Spaceship. The tanker will then return to Earth for a propulsive landing enabling it to be used again. SpaceX’s goal is for the ITS booster to be reused up to 1,000 times and for the tanker to be reused up to 100 times.
In addition, the choice of liquid methane as the fuel and liquid oxygen as the oxidizer makes the rocket self-sustaining, in a sense. On Mars, the vehicle will be able to extract Carbon Dioxide from the atmosphere and utilize the Sabatier reaction to produce methane and oxygen. The in-situ propellant production method will allow the Interplanetary Spaceship to return the Earth to be reused. Also, the two solar arrays aboard the spacecraft can generate up to 200 kW of power in order to make propellant production possible. SpaceX is targeting each Interplanetary Spaceship to be reused up to 12 times.
Musk forecasts that by the mid-2020s the cost of launching or a ton of cargo to Mars will hover somewhere between $100,000 and $200,000. That’s cheap enough for many people to sell their properties and move to Mars, where terraforming will be taking place to transform Mars into an “earth-like planet.”
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