How the most powerful rockets in history are speeding up a new race to the Moon
NASA and SpaceX are building two gigantic launch vehicles with massive thrust, which they hope will help humans set foot on the lunar surface again this decade
The year 1968, which began with massive protests against the Vietnam War and witnessed social revolutions for freedom, ended with other historic milestones in the realms of sports and space exploration. On the athletics tracks of the Olympic Games in Mexico, many champions achieved feats that had previously seemed unattainable and otherworldly. It took decades for the last of those world records to be broken, such as the 100-meter dash and long jump, achieved in October 1968. Two months later Apollo 8, the first crewed ship to orbit the Moon, took off. It was the first manned mission launched by Saturn V, which remained the most powerful rocket in history until the Artemis program to return to the Moon began in 2022.
On November 16, 2022 NASA broke its own record, more than 50 years later. When the Artemis 1 mission lifted off, the SLS (Space Launch System) super heavy-lift launch vehicle produced a slightly higher thrust (15%) than that of Saturn V. But everything indicates that this newest record will soon be pulverized. The prize for the most powerful launch vehicle in history is expected to go to SpaceX’s Starship (which doubles the takeoff thrust of Saturn V) as soon as it makes its first successful flight, which could happen in April, according to SpaceX owner Elon Musk’s statements on Twitter last week. Musk also wants his mega-rocket to be the first that can be reutilized again and again: “The key to expanding life beyond Earth is a fully and rapidly reusable orbital rocket,” he said in a recent interview.
Super heavy-lift launch vehicles are essential in the new space race, whose first challenge is to set foot on the Moon again in this decade, with a longer-term goal of establishing a colony on Mars. But none of this will be possible without this new generation of rockets capable of lifting around 100 tons of payload into low-Earth orbit. Once there, they will detach, leaving the spacecraft ready to shoot towards other worlds. Of the 384,000 kilometers (239,000 miles) of average distance between the Earth and the Moon, the most critical part of the trip involves reaching an altitude of approximately 200 kilometers (124 miles) to deliver the spacecraft to a low Earth orbit, which is stable and safe. And all this in less than 10 minutes, a period during which any failure could be fatal.
“That initial stage is what consumes most of the energy and fuel of a mission to the Moon, and also a large part of its astronomical budget of billions of dollars,” explains Rafael Clemente, a historian of the space race and author of several books on the subject. Escaping the pull of gravity with the heavy load necessary for the trip will require the record power of the gigantic SLS and Starship rockets, which are as tall as 30-story buildings. “These new rockets have a colossal aura about them that is reminiscent of the allure and sense of epic of the Saturn V and the Apollo program. Although that was an unrepeatable historical event, the new generations have the opportunity to experience some of those sensations,” says Clemente, who watched the launch of Apollo 15 live. “There were thousands of us in a grandstand at Cape Canaveral, five kilometers from the platform. Takeoff was a thunderous spectacle, which we felt as if it were happening right in front of us.”
To get back on the Moon, NASA has relied on its decades-tested technology. The SLS has inherited key components from the space shuttles, and its multi-module structure — on which the Orion spacecraft travels — is based on the Saturn V from the Apollo missions. That strategy has already paid off with the success of the Artemis 1: “The first launch of the Space Launch System rocket was simply eye-watering [...] The rocket’s systems performed as designed and as expected in every case,” Mike Sarafin, Artemis mission manager, said in a statement last November. NASA shared a more detailed assessment in January, confirming the excellent initial data, and it has already given the green light to use the SLS on manned missions.
A retro giant
SpaceX has chosen a very different path with its Starship: the spacecraft takes off atop a single module rocket, the result of a simplified and integrated design. The imposing ensemble is the tallest space vehicle ever built and, despite its retro appearance that evokes 1950s science fiction, it contains state-of-the-art technologies, some of them unprecedented in the space race.
With previous experience in reusable rockets, such as the Falcon, Elon Musk’s company decided to start almost from scratch to design its first mega-rocket. Their big bet is a completely new engine: the Raptor, which burns liquid methane (a fuel never used before in orbital rockets) and which its creators hope can be reused in up to 1,000 flights. This engine also innovates with highly efficient staged combustion, which allows it to reduce its size and multiply its applications. The Starship’s Super Heavy booster, for example, carries a swarm of 33 Raptor engines at its base. And in January, SpaceX successfully completed static firing for 31 of the 33 engines, the last technical hurdle it needed to clear before testing the first launch of the Starship.
Super Heavy Booster 7 completed a full duration static fire test of 31 Raptor engines, producing 7.9 million lbf of thrust (~3,600 metric tons) – less than half of the booster’s capability pic.twitter.com/cNLmp3Pn7G— SpaceX (@SpaceX) February 10, 2023
SpaceX will be a pioneer in testing these technologies on rockets, but it is not the only one working on them. Since 2017, the European Space Agency (ESA) has been developing Prometheus, its own low-cost and reusable engine, which is also powered by methane: “Methane is very cost-effective compared to hydrogen and is slightly more efficient than kerosene,” explains Jérôme Breteau, ESA’s head of Future Space Transportation Systems. The liquid hydrogen used by SLS is much more complicated and expensive to handle than liquid methane, which in turn is much cleaner than the kerosene used by SpaceX on its previous rockets. In addition, there would be the possibility of producing methane fuel on Mars.
NASA’s SLS, on the other hand, uses the same main engines of the space shuttles (RS-25), reconditioned units that had been left over after the retirement of those legendary spaceships in 2011. Despite this strategy of partially reusing components, the costs of this mega-rocket have skyrocketed and the project has also broken records in terms of delays since then-president Barack Obama first approved it in 2010. On the SLS flights, not even the side thrusters will be recoverable, which they used to be during the days of the shuttle launches when they parachuted down to Earth.
Total reuse is essential for the SpaceX Starship, and the great key to its promise to reduce the cost per flight to levels never seen in the space industry. But it is a midterm goal that the company hopes to achieve after at least two years of testing. In these first few tests, SpaceX is not promising to reuse any components, and will be happy if the rocket does not explode in the air. “I’m not saying it will get to orbit, but I am guaranteeing excitement,” said Elon Musk in his most recent statements about Starship’s first orbital mission, which he believes has a roughly 50% chance of succeeding. “So, won’t be boring!” The billionaire businessman has emphasized in his appearances that “fly, explode, learn, repeat” is the motto that has led SpaceX to lead the space cargo transport sector.
Pending final authorization from the US Federal Aviation Administration, SpaceX has announced that everything is ready for that first launch of the Starship. And NASA also wants that to happen as soon as possible, even though it is competing with Musk’s company in the mega-rocket race. The US space agency has selected a modified version of Musk’s ship (Starship HLS) as its lunar landing module for a return to the Moon in the Artemis 3 mission. For the descent to the Moon, the astronauts will be transferred to Starship HLS from the spacecraft Orion, which by itself has no capacity to land on the Moon. That’s why the success of the Starship is critical to getting the first woman to the Moon. In this new space race, the two competitors are not actually fighting to build the most powerful mega-rocket in history. That merit will go to Musk’s company. It’s more of a relay race, in which SpaceX and NASA need each other to reach the finish line on the lunar surface.
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