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The SpaceX Starship: Elon Musk’s Gateway to Mars

Telescopes on the moons of Neptune, violin concerts in Lunar orbit, a Martian city of over a million inhabitants. If Elon Musk has his way, these concepts won’t be science fiction for long.

His plans require a pretty big rocket, though. That’s where Starship comes in. The two-part vehicle, consisting of a lower Super Heavy Boost and the upper Starship spacecraft, scrapes the sky some 120 meters or nearly 400 feet above SpaceX’s Starbase where it’s currently under development. That makes it roughly 9 meters or 30 feet taller than Saturn V, the rocket that sent American astronauts to the Moon and current record holder for height.

Once it’s finished, Starship’s massive construction will be the least of its record-setting feats. With the power and thrust to carry both crews and equipment into various transfer orbits and the toughness and durability to do it over and over, Starship will play an essential role in giving humanity a toehold beyond Earth.  

KNOWN BY MANY NAMES

Starship | Artist Rendering by Official SpaceX Photos is licensed under CC-BY-NC

Elon Musk first hinted at his plans for Starship in 2005 at a conference for Students for the Exploration and Development of Space at the University of Illinois Urbana-Champaign. This was still two weeks before the first launch of Falcon 1 with Falcon 5 and 9 still only in development, but Musk was making it clear those weren’t the end of his ambitions.

When a student pointed out that SpaceX’s test stand in Texas was capable of handling over 16 million Newtons of thrust, or 3.5 million pounds, five times that expected from Falcon 9, Musk revealed his ideas for the Merlin 2 rocket engine, which would be a scaled up version of the Merlin engines used in the Falcon series. He suggested multiple Merlin 2s could power his envisioned “BFR” rocket, B standing for “big,” R for “rocket, and F you can figure out for yourself.

At the time, Musk didn’t seem to have it figured out much farther than that. Who would fund the rocket and who would buy it still seemed up in the air, but one thing was clear: Musk had his eye on Mars.

In 2012, SpaceX revealed more concrete plans in the form of the Mars Colony Transport, or MCT, a spaceflight system consisting of reusable rockets and transport vehicles to take humans to the Red Planet and set up a permanent colony. SpaceX engine development head Tom Mueller gave more details in 2014 by explaining that the spacecraft would use new Raptor class engines, potentially even 27 of them, to take 100 metric tonnes (220,000 pounds) of crew and cargo to Mars.

After the conceptualization of MCT, it went through a bit of an identity crisis. First, Musk decided to rename it “Interplanetary Transport System,” or ITS, in 2016 because Mars wasn’t the only goal. However, later in a Reddit AMA, he revealed he didn’t really like that name either and was still using “BFR” internally.

Finally, Musk just made BFR official, albeit with a small tweak. Now it would stand for Big Falcon Rocket instead of the more expletive previous nickname. The carbon-fiber rocket would be designed for both Earth-orbit, Lunar and Mars missions.

SpaceX began testing Raptor engine burn and even had plans to start manufacturing the BFR in Los Angeles in 2018. The plan was then to transport it by barge through the Panama Canal to the launchsite and the Kennedy Space Center in Cape Canaveral, Florida.

Then, at the end of 2018, Musk announced one more name change. BFR would now be Starship. Not only that, the rocket would be stainless steel instead of carbon fiber, something Musk claimed would cut costs while not actually adding weight due to steel’s increased strengths at “cryogenic” temperatures. Later in January of 2019, SpaceX decided to move manufacturing from the Port of Los Angeles to Boca Chica, Texas, where construction and testing have continued to this day.

THE WORLD’S THRIFTIEST ROCKET

Starship | First test vehicle by Official SpaceX Photos is licensed under CC-BY-NC

“Starship” technically refers to the upper spacecraft which sits on top of the lower Super Heavy Booster that holds the Raptor engines that launch the vehicle into space. Once it reaches the needed velocity, Starship will detach from the Super Heavy Booster, which will return to Earth and land vertically by being caught by a giant mechanical arm, making it reusable. Starship will then be capable of docking with tanker ships to refuel and prepare for lunar or interplanetary missions.

When fully stacked and fueled, Starship isn’t just taller than Saturn V, it’s heavier too, weighing in at around 5,000 metric tonnes, over 11 million pounds. Saturn V weighed a mere 6.2 million pounds.

The Raptor engines themselves are constructed of SAE 304L Stainless Steel, an alloy containing large amounts of chromium and nickel. They can reach internal pressures of up to 300 bar, or roughly 4,400 psi, more than 100 times the pressure in most car tires, thanks to their groundbreaking full-flow staged combustion cycle. 

In traditional open-cycle rocket engines, turbopumps spun by what are basically mini rocket engines called preburners keep fuel and oxygen moving into the combustion chamber. This is the design used by the Merlin engines on SpaceX’s Falcon rockets. However, since these turbopumps must use fuel themselves, they cost the engine efficiency. 

Moreover, since they’re made of complex mechanical parts, the turbopumps can melt, meaning the fuel must be burned at less than optimal temperatures by increasing the ratio to fuel-rich or oxygen-rich. Either way, you’ll be wasting some of your propellant.

To solve these problems, rocket scientists came up with the “closed cycle,” which returns the exhaust and unused propellant from the turbopump back into the engine. But this isn’t as easy as it sounds. 

If you run the turbopump fuel-rich, traditional carbon-based rocket fuel produces soot in a process called “coking,” and if you return this to the engine, it’ll just gunk it up. Meanwhile, if you run the turbopump oxygen-rich, the superheated oxygen will quickly corrode the metal of your engine.

The Soviets conquered this problem by developing a new alloy that could withstand an oxygen-rich mixture while the Americans opted to run their turbopumps fuel-rich but with a different, non-carbon-based fuel: hydrogen. This eliminated the coking problem but demanded an elaborate sealing system for the hydrogen that requires regular maintenance and rebuilding, not suitable to SpaceX’s plans for reusability.

The Raptor engines’ full-flow design basically combines the two approaches by having two turbopumps, one running fuel-rich and the other oxygen-rich. This doesn’t just eliminate wasted propellant. It also means that both the oxygen and the fuel are traveling through a turbopump before reaching the combustion chamber, allowing for better combustion and higher temperatures in the engine. 

Plus, the mixture in either turbopump is highly oxygen- or fuel-rich, meaning they run at lower temperatures. This increases their lives significantly. Musk has even stated he plans to get 1,000 uses out of each Raptor engine.

Although two other rockets have been designed with full-flow engines, neither ever left the launch pad. With the success of the Raptor engines in the Starhopper test vehicle, it makes them the first.

To accomplish this, SpaceX had to develop an entirely new steel alloy to withstand the corrosive environment in the oxygen-rich turbopump. This is called SX 500, and along with being oxidation-resistant, it can maintain pressures of up to 800 bar or 12,000 PSI, the equivalent of a column of water eight kilometers high.

As for the fuel-rich turbopump and its “coking” problem, SpaceX also broke ground by deciding to use methane fuel in their Raptor engines, making them the first rocket engines to do so. On top of allowing for the full-flow design, methane also burns efficiently, is inexpensive, and could be produced by colonists on Mars to allow for refueling for return trips. This makes it an ideal fuel for Starship.

With its innovative design, a Raptor engine produces around 2 million Newtons of thrust (or about 500,000 pounds). Super Heavy Booster will potentially have 35 of the engines to launch Starship, meaning a total of nearly 70 million Newtons of thrust (or upwards of 16 million pounds). This is roughly the power generated by 170 Hoover Dams, or double that of the Saturn V rocket. Then, when it detaches, Starship itself will have six of its own Raptor engines to insert itself into orbit.

The Raptor engines contribute to Starship’s economic viability as well. Long term SpaceX wants to manufacture the engines for about 2 million US Dollars a piece and hopes to be able to reuse them 50 times before they require refurbishment. For reference, the Merlin rockets cost about $1 million a piece and can be reused 10 times. In other words, a Raptor costs about $40,000 per launch versus $100,000 for the Merlin. 

And the F-1 rocket engine used on the Saturn V rocket? $30 million to make and single use only.

Still, though. This isn’t even the economic metric Musk and SpaceX like to use. Instead, they prefer to look at what they call “the thrust-to-dollar ratio,” basically how much power the engine is getting for the cost of manufacturing it. At roughly $1,000 per kiloNewton, the Raptor engine is set to be the thriftiest engine ever made, about 10% less expensive than the Merlin and less than a quarter the cost of the F-1.

Altogether Musk has stated he believes he can get the cost per launch for Starship down to $2 million.

PRACTICE MAKES PERFECT

SpaceX has taken things slow with Starship in order to test and ensure the feasibility of every aspect of the spacecraft’s design.

Starship SN8 High-Altitude Flight Test by Official SpaceX Photos is licensed under CC-BY-NC

The first step was to test the Raptor engine using the Starhopper module. The ship, whose only purpose was to test the engines, launched in July 2019 and “hopped” about 20 meters or 65 feet into the sky. It really jumped in its final test the next month, reaching 150 meters, or 500 feet.

After that, SpaceX ran tests with several SN-designated prototypes until the first full Starship SN8 began testing in 2020, though this was still only the upper Starship spacecraft without the Super Heavy Booster. After several unsuccessful static tests that involved damage to the launch pad, SN8 finally took off for the first time in December 2020. It reached an altitude of 12.5 kilometers or about 8 miles. It then belly flopped and attempted to use its fins to land vertically, but a fuel supply problem caused it to crash into the landing pad and explode. 

SN9 suffered a similar fate. In fact, it wasn’t until SN15 in May 2021 that the first Starship prototype launched, performed the same maneuvers, and landed vertically successfully on the launch pad.

In July of 2021, SpaceX started with the Super Heavy Booster prototypes with Super Heavy BN3 performing a static test with 3 engines. Super Heavy BN4 was then the first capable of attaching to a Starship spacecraft, eventually mated with SN20 to create Ship 1.

The first orbital test of Starship is currently awaiting FAA approval, which they are hoping to receive at the end of February. The proposed flight trajectory will see the vehicle launch from Starbase in Boca Chica after which the Super Heavy Booster will detach and land in the ocean 30 kilometers or about 20 miles from the Texas coast. The Starship spacecraft itself will continue in orbit before finally landing 100 kilometers or 60 miles south of the Hawaii coast. 

JACK OF ALL TRADES

The list of proposed uses for Starship never seems to stop growing.

At the moment, the most financially viable purposes seem to be those in Earth orbit, even though Starship will be capable of much more. This includes transporting gear and equipment for NASA, launching military satellites, and even cleaning up space debris.

Perhaps more lucrative, SpaceX can use Starship for their own business purposes by launching Starlink satellites. It’s estimated that a single Starship launch could place 400 Starlink satellites in orbit, versus 60 for Falcon 9.

Arguably cooler applications include carrying telescopes and robotic landers to the Moon or outer regions of the Solar System. For example, it’s been proposed that Starship could carry a probe to the moons of Jupiter and telescope to Neptune’s moon Triton to study exoplanets. Additionally, Starship would be capable of carrying heavy drilling equipment that could be used to extract rock samples from the Moon or other bodies in the Solar System.

Interestingly, there are even proposals to use Starship for non-space applications. For instance, SpaceX COO Gwynne Shotwell has argued that the “Earth-to-Earth” application could be competitive with business-class air travel. The idea is that a Starship spacecraft could launch from one spaceport on Earth with passengers and land in another. SpaceX claims it could fly from New York to Shanghai in 39 minutes. The US military’s Space Force has also discussed using Starship to transport military equipment and personnel in a similar way.

Space tourism is another profitable and likely future application. In September 2018, Japanese billionaire Yusaku Maezawa announced his dearMoon project, in which he plans to take a crew of eight civilians in addition to himself and one or two professional astronauts on a six-day trip around the Moon in 2023 using Starship. The civilian crew will consist of artists, though as of yet no one has been confirmed.

Of course, the primary and most lofty goal for Starship is human exploration of other bodies in the Solar System. By 2025, NASA wants to land humans on the Moon again through its Artemis program, and it plans to do so in Starship.

This particular Starship model will be called Starship HLS (Human Landing System) and is somewhat different from the standard design because it won’t have to re-enter the Earth atmosphere and therefore doesn’t need heat shields or the flaps used by other Starships to adjust to wind force. Rather, it’s designed to transport astronauts from orbit to the practically atmosphere-less lunar surface and back.

After launching into low-Earth orbit, multiple Starship tankers will refuel it. Then it will go on to meet NASA’s Orion spacecraft. The crew will move onto Starship, which will transport them down to the Moon for several days and then take them back up. 

Altogether, NASA is paying SpaceX $2.89 billion for Starship HLS.

However, SpaceX and Elon Musk’s real goal for Starship is the colonization of Mars to ensure the long-term survival of the human species. Musk has stated 2024 for the first uncrewed mission and 2026 for the first crewed mission, though skeptics doubt a crewed mission is feasible before 2029.

While the colony would obviously involve a small group of people at first, Musk has expressed the long-term objective of a million-person city. The reusability and economic affordability of Starship would be fundamental to this because Musk was quoted as saying:

“Excluding organic growth, if you could take 100 people at a time, you would need 10,000 trips to get to a million people. But you would also need a lot of cargo to support those people. In fact, your cargo to person ratio is going to be quite high. It would probably be 10 cargo trips for every human trip, so more like 100,000 trips.”

That’s a lot of ships launching repeatedly, making the 80-to-150-day trip between Earth and Mars, so if you think you might like to retire to a Martian metropolis, there might just be room for you. Make sure you start saving now, though, as Musk has pegged Starship ticket prices at just $200,000.

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