SpaceX Starship: What’s the Big Deal?

Photo by Hotel Marmot in Wikimedia Commons

It’s May 5th, 2021. The sky over Boca Chica, Texas, is gunmetal grey, with a hazy mist creeping lazily over the surrounding nature reserve, stretching out towards the beach and into the Gulf of Mexico. But this is no ordinary day in southern Texas. There’s a sense of suspense hanging in the air, an electricity, that emanates from a little spaceport known as Starbase. Operated by spaceflight industry giant SpaceX, Starbase serves as the testing ground for the company’s newest, biggest, most ambitious rocket: the Starship. Once ready, it could shuttle humans to Mars and help them establish a colony there. But so far, almost every attempt to launch and especially land the thing has caused it to blow up in a most spectacular fashion.

Will today be any different? As the rocket’s latest prototype waits patiently on the pad, it looks more like a glorified tin can with some patches and flaps stuck onto it than the majestic spaceship of the future depicted on the company’s promotional material — and yet, its time to shine is now. Suddenly, with a metallic gush, the ship breathes orange fire and begins a tentative climb into the low-hanging gloom. Onboard cameras show its flaps bathed in sunlight as the rocket punches through the clouds; once it reaches its desired altitude, it flips onto its side, using a so-called belly-flop maneuver to slow itself down as it falls back to Earth. So far, so good — but now for the landing. With two engines, the rocket flips back into position and, with a slightly awry-looking angle, sticks the landing… and doesn’t explode.

They had done it. The test’s success made waves throughout the spaceflight community, with its video reaching almost seven million views. Since that 2021 test, the rocket has been grounded due to bureaucratic issues — such as waiting for the site’s environmental review and launch license — and developments on the vehicle itself. Now, almost two years later, the rocket has all but completed its required testing ahead of its first orbital launch attempt, scheduled for April 2023.

Despite the long hiatus, Starship has amassed a legion of devoted fans who watch over goings-on at Starbase via a 24/7 live feed and chat, as well as devoted Twitter pages broadcasting the factory’s every move; some fans have even uprooted their lives to move closer to Starbase. NASA seem impressed, too, and have contracted SpaceX with providing two modified Starships to land humans on the moon as part of the Artemis program. The reason for Starship’s popularity? Together with its booster, the rocket — dubbed the ‘Holy Grail’ of space travel by SpaceX CEO Elon Musk — would be the biggest, most powerful launch vehicle in history.

Mighty as it may be, the crux of the vehicle’s design is its reusability. Reusing rockets drastically lowers the cost of spaceflight, already proven by SpaceX’s very own Falcon 9 boosters. Packing more fuel in order to land the rocket stages makes the approach less efficient than expending them, but the price drop made possible by frequently reusing the vehicles more than cancels this out. Also, reusability will prove vital for colonies on Mars and beyond — SpaceX’s ultimate goal — so even the earliest plans for such a rocket, announced by Musk in 2012, made it a priority.

This preliminary design, called the Mars Colony Transport, was to be powered by new methane-guzzling engines called Raptors. Methane, while not quite as efficient as the notoriously fickle liquid hydrogen fuel favored by NASA, is relatively dense, easy to handle, and does not cause buildup on the engines, making it suitable for reusable rockets. In addition, colonists in the distant future could use Martian resources to create this fuel for a trip home; Musk also has plans to convert atmospheric CO2 into methane fuel on Earth to reduce the vehicle’s environmental impact.

In 2016, Musk decided that Mars was not enough, and renamed the rocket Interplanetary Transport System (ITS), which could carry either 450 tons of cargo or 100 or so people to Mars — or beyond. As listed here, it was to be comprised of two stages — a booster and a spaceship — both made out of carbon fiber. The whole thing would have stood 122 meters tall, making it tower over even the 111-meter-tall Saturn V. Still, the design never really came to fruition, with Musk announcing a new yet similar vehicle called Big Falcon Rocket — BFR — in 2017. This rocket’s design was further tweaked, with changes including a switch from carbon fiber to stainless steel; the upper stage was renamed Starship — and its booster christened Super Heavy — in 2018. And now, its first proper test flight is just around the corner.

Though development is ongoing and designs are constantly changing, here’s a basic overview of the rocket:

Super Heavy booster

• Standing 69 meters tall, this stainless-steel giant would launch the vehicle into the skies before separating from the ship and coming back down to Earth.
• Though it will ditch into the water for its test flight, the ultimate plan is for the booster to return to the launch site and be caught by mechanical arms on the launch tower, ready to be restacked and take off again. The booster has so-called hardpoints to help the tower grab it.
• The booster is powered by 33 Raptor engines, which produce 7,590,000 kilograms of force at launch: more than twice the thrust power of the Saturn V.
• Super Heavy will carry about 3,400 tons of propellant; about 78% of this will be liquid oxygen (LOX). As fire cannot burn in space without air, rockets carry an oxidizer with them, which in this case is LOX. The actual fuel is liquid methane, or CH4.
• Four grid fins — spatula-like appendages at the top of the vehicle — and cold-gas thrusters allow Super Heavy to steer itself, much like the Falcon 9’s booster.
• All together, the booster’s dry mass — or mass without propellant — is below 200 tons.

Starship Spacecraft

• This is the second stage of the rocket, and would also house crew and cargo.
• The ship is 50 meters tall, and the whole vehicle comes in at a record-breaking 120 meters. In the future, the ship might grow to be another 10 meters taller.
• The ship has a payload volume of 1,000 cubic meters, into which one could fit an entire disassembled Eiffel Tower.
• Using the booster, the ship could carry 150 tons of cargo into orbit while remaining fully reusable; if expended, the capacity rises to 250 tons.
• The payload area can be customized for satellite launches with a clamshell-like door.
• For crewed missions, this payload bay would be pressurized and could hold up to 100 people; it would include ‘private cabins, large common areas, centralized storage, solar storm shelters and a viewing gallery’.
• The ship can hold 1,200 tons of propellant, which, again, is LOX and CH4.
• To maximize efficiency for deep space missions, SpaceX is developing in-orbit refueling methods, which could involve orbital fuel depots or even one ship delivering fuel to another. If this becomes a reality, it would allow the ship to carry its full payload to the moon and perhaps even Mars.
• Starship has six Raptor engines: three for sea level and three tuned to be more effective in the vacuum of space. Three more vacuum engines are likely to be added in the future.
• During atmospheric reentry, the vehicle slows itself down by assuming a belly-flop position to increase its surface area, which in turn increases atmospheric drag. Four body flaps further increase surface area.
• Reentering from orbit can positively toast spacecraft, since they experience temperatures equal to their hair-raising velocities — cubed. To help the ship survive the blistering heat, one side of it is covered in hexagonal heat tiles, which can withstand temperatures of 1,377 degrees Celsius.
• The plan is to catch not only the booster with the mechanical arms on the launch tower, but the ship, too; the latter therefore also has hardpoints.
• Depending on the purpose of a ship, its specifications may change; the Lunar Lander Starship, for example, has landing legs but no body flaps.

Raptor Engines

• As explained in detail by Everyday Astronaut, Raptors are the first flown rocket engines to use a so-called full flow staged combustion cycle, making them extremely effective. A quick summary on what that means:
• To spew all that propellant out of the rocket fast enough to propel the vehicle, most rocket engines use something known as a turbopump, which is powered by a ‘mini rocket engine’ called the preburner. A small amount of propellant is used to power this preburner, but in so-called open-cycle systems, this small fraction of propellant is wasted, and not used for the actual propulsion of the rocket, so it is less effective.
• In closed-cycle systems, this propellant is redirected so that it contributes to the propulsion, but there’s a problem: in order to not melt the turbopump, the preburner needs to run at less-than-optimal efficiency. This means either cutting down on oxidizer (fuel-rich) or fuel (oxidizer-rich) at this stage in propulsion. Fuel-rich is not great for carbon-based rockets as the extra fuel will turn into black soot (known as coking), while oxidizer-rich systems produce staggering amounts of hot oxygen that destroys everything in its path.
• Raptors use methane as fuel, which burns clean, so no coking here. SpaceX also managed to develop a ‘superalloy’ called SX500 for the engines that can withstand the flow of hot oxygen. Therefore, for maximum efficiency, Raptor engines use two turbopumps: one for each propellant, powering each other (meaning one is fuel-rich, the other oxidizer-rich).
• Since all the fuel now passes through the turbopumps, these can spin faster and spew much more out. In addition, less fuel/oxidizer is needed for each respective turbopump, lowering the ratio and therefore heat of the preburner and extending its lifetime.
• Raptors’ specific impulse, or efficiency, is as high as 363 seconds, trumped only by the Space Shuttle’s RS-25s (which have the downside of using liquid hydrogen, and that comes with its own set of problems).
• The ship’s three vacuum-tuned engines are bigger since the nozzles should typically match external pressure; since space has no pressure, the nozzle technically must expand infinitely for maximum efficiency (which is obviously impossible), so rocket scientists strike a compromise with space by making the engines bigger than sea-level ones.
• Most engines on the ship and booster are gimbaled — meaning they can turn to change trajectory — but the outer ring on the booster is fixed in place to save on mass.

‘Stage Zero’, including Orbital Launch Mount (OLM) and Mechazilla

• Though not technically part of the rocket, the extensive ground systems at Starbase play a significant part in the vehicle’s operations, and are therefore often referred to as Stage Zero.
• The Orbital Launch Mount (OLM) is a stool-like structure on which the entire rocket sits, used in lieu of a launch pad. It is enveloped in stainless steel shielding and contains a water deluge system, which sprays water onto the flames to suppress sound and minimize damage to the launch mount. Though not in place yet, parts for a flame diverter have recently arrived at Starbase.
• The launch tower — nicknamed Mechazilla by Musk — play an important part in the vehicle’s reusability. All going well, the ship and booster should one day land exactly so that they can be caught by the tower’s robotic arms, or ‘chopsticks’, and stacked back onto the launch mount.
• The company aims to launch Starship/Super Heavy several times a day, much like an airplane, to further reduce costs. Musk has stated that at least for Super Heavy, turnaround could be as short as one hour.
• This efficiency and rapid reusability led Musk to predict a cost as low as $10 million per launch (or even $1 million) — steep, but practically nothing compared to the $4.1 billion of NASA’s expendable Space Launch System.

This efficiency, payload capacity, and relative affordability could allow small space stations, orbital factories, or even entire constellations of satellites to be deployed at once, changing the space industry for good. It is also entirely possible that a few of these rockets could be used to send humans to Mars with enough supplies to set up a preliminary colony. That’s all fine and good… but now it just has to launch. Despite its first human flight being announced for 2023, the rocket, at the moment, is far from being able to carry anything safely, what with its impressive track record of pyrotechnics on the pad.

But those aren’t always a catastrophe; they are simply part of SpaceX’s way of doing things. In a process known as iterative and incremental development, Musk tweets, more progress can be made by building more rockets, seeing what goes right or wrong, and rapidly improving each one as they go along. As opposed to NASA (who spend years honing every detail to perfection for one launch; they rely on Congress and their image for funding and cannot afford a fiery crash), SpaceX were able to figure things out pretty quickly and make unheard-of technology relatively functional in a span of years.

Once up and running, the rocket has its work cut out for it. Customers including NASA, billionaires Yusaku Maezawa and Jared Isaacman for their respective dearMoon and Polaris projects, the US Space Force (who are looking into using it to rapidly move cargo from one point on Earth to another), and, of course, SpaceX’s internet company Starlink are already lining up; but that’s all peripheral to Starship’s main purpose.

SpaceX, after all, was founded in response to the lack of rocket capable of bringing humans to Mars. According to Musk, the first crewed missions could take place in 2029, though his timelines tend to be somewhat optimistic. If all goes to plan, though, a fleet of a thousand Starships would one day be sent to our planetary neighbor to establish a colony, and a ticket for the trip, so Musk, could be yours for the low, low price of $100,000. Though tackling In-Situ Resource Utilization (ISRU) — using locally available resources to maintain the colony, instead of relying on Earthly shipments — is a major obstacle to overcome, SpaceX ultimately hopes that Starship, in bringing humans to new worlds, could sustain the existence of life were disaster to strike on Earth.

A bold vision, sure, but it is exactly that which sets SpaceX apart — and earns them one hell of a fanbase. As described here, some of Musk’s most devoted fans even believe he ‘is delivering a future to humanity’. Set aside the hype, though, and you’re left with a sleek, powerhouse rocket that, provided it doesn’t crash and burn, could change the landscape of the sector forever. Plus, it simply smells like the future. And that might be exactly what the space industry, which is still largely rooted in the past, needs.

Inmarsat, a British satellite telecommunications company, recently conducted ‘the largest ever survey of public perceptions of space globally’. According to CEO Rajeev Suri, ‘those aged 18 to 24 seem to be guided more by science fiction and movies than a real understanding of what is happening in space’. Older generations that saw the space age firsthand are generally more excited about what’s going on in the sector, says the study, but younger people have witnessed no such breakthroughs. Could the futuristic yet still-suborbital Starship — which looks like sci-fi come to life — change that?

If predictions from the space fever of the 1960s were anything to go by, we would’ve long established colonies on Mars and beyond by now; today, with decades of delay, we might have a sleek, stainless steel-finished starting point. As computer researcher Alan Kay said, ‘the best way to predict the future is to invent it’. Will Starship prove him right?

Originally published at https://notrocketscience.substack.com on April 9, 2023.