Interplanetary Exploration :Starship’s Super-Heavy Booster Recovery Heralds A New Epoch

On Sunday (October 13), SpaceX launched its fifth Starship vehicle. The Starship super-heavy rocket took off from the company's Starbase facility in Boca Chica, Texas, at 8.25 am (EDT). SpaceX referred to this mission as Flight 5. The launch was impressive: a booster rocket, with twice the power of the Apollo programme's Saturn V, soared into the early morning sky on a bright, narrow trail of blue-tinted flames.

However, this was not the first time people have seen such an incredible launch-it has happened four times before. What made SpaceX's fifth Starship test flight truly special was the successful landing of the booster stage, which was an extraordinary achievement.

Restarting 13 of Starship's Total of 33 Engines

About a kilometre above Earth's surface, after falling back from the edge of space-and still moving at about the speed of sound-the 71-metre-long steel rocket restarted 13 of its 33 engines. A few seconds later, after slowing down to a few hundred kilometres per hour, most of the engines shut off. The rocket then balanced on the power of just three engines-it was like balancing a broomstick on a fingertip.

Those engines steered the rocket back to the 146-metre-tall (480-foot-tall) tower from which it had launched just seven minutes earlier. As the booster descended past the tower, still appearing to tilt a bit in a worrisome manner, the tower's large arms moved in and secured it. It finally stopped, hovering high in the Texas sky. Small flames still flickered around its edges. It looked a bit awkward and unbelievable-almost in every way.

The successful landing was a big win for the engineers at SpaceX, the company led by Elon Musk. This shows that SpaceX's goal of using a large reusable rocket booster to regularly launch their big reusable spacecraft, called Starship, is possible.

It also means that, in the coming years, especially in the latter half of this decade, SpaceX will be able to launch much more cargo into space. This includes missions for both its private customers and the US government. As SpaceX increases its capabilities, the number and size of things it can send into orbit will grow significantly.

And the cost of sending each ton of cargo into space is expected to drop significantly. According to an estimate from Citigroup, as reported by The Economist, SpaceX's partially reusable, and frequently flown, Falcon 9 rockets have already reduced the cost of a space launch by 90% (or 1/10th the cost). The much larger, and fully reusable, Starship is expected to lower costs even further, possibly by more than what the Falcon 9 has already achieved. It could be the biggest breakthrough in space travel since the 1960s.

More evidence that these kinds of missions could happen in the near future came when, just an hour after the super-heavy rocket landed back at its launch site in Texas, the Starship (upper-stage), itself, made a gentle splashdown in the Indian Ocean. Unlike the super-heavy rocket, the Starship has to re-enter Earth's atmosphere at speeds of over 26,000 kilometres per hour because it travels in orbit.

On this test flight, the heat shield handled re-entry better than it had done during the last test in June, but it still was not perfect. Live video showed part of the spacecraft's structure catching fire, causing concern. Despite this, the Starship appeared to complete its landing steps as planned and splashed down in the targeted area. A SpaceX camera in the vicinity captured the landing.

SpaceX Is Now Way Ahead of Its Competitors

The flight highlighted how much further ahead SpaceX is compared to its competitors. The engineers were able to bring the Starship booster back to Earth because they have gained a lot of experience returning the smaller first stages of the Falcon 9 rocket. Since late 2015, SpaceX has been successfully landing the first stages of its rockets. These stages have built-in landing legs, so they do not need to be caught in mid-air. This landing exercise has been carried out over 300 times.

Right now, no other rocket company has a reusable first stage, although two are getting close. Blue Origin, owned by Amazon founder Jeff Bezos, plans to test a reusable rocket in the next few months. RocketLab, a smaller startup, aims to launch one next year. Meanwhile, several Chinese companies are also developing similar technology.

More tests are still needed. SpaceX has to prove that the Starship can switch its engines on and off in space, allowing it to enter and exit orbit properly. Eventually, SpaceX needs to demonstrate that it can catch the Starship (upper-stage) with the arms of a gantry during landing. Unlike most rocket companies, SpaceX is comfortable conducting frequent test flights. After two tests in 2023, this was already the third in 2024, and they are likely to speed up even more.

The success of this flight suggests that, while there would, possibly, be some setbacks, SpaceX could have its Starship ready for basic operations within the next few years. When Starship becomes fully operational, there will be plenty of tasks for it to handle. NASA's Artemis programme, which aims to land humans on the Moon, relies entirely on Starship reaching orbit regularly-possibly, as often as once a week, or more.

SpaceX's own plans to expand its Starlink satellite network-which already has over 6,000 satellites-also rely on Starship. Additionally, Elon Musk's dream of colonizing Mars depends on it. He is aiming to send five un-crewed Starships to Mars by 2026, with plans to send crewed missions shortly after that. Elon Musk's goals for Mars are part of his broader vision to protect civilization. With the super-heavy rocket cooling down in its launch stand, the goal of reaching Mars now seems more realistic than ever before.

Lifting Starship: Super Heavy Booster's Might

The Starship is lifted into space by the super-heavy booster. This large, shiny steel cylinder (of the booster) is 9 metres wide and 71 metres tall-as long as a Boeing-747, but much wider, making it even more impressive in scale. When empty, the super-heavy booster weighs around 200 tons. Fully loaded, it carries about 3,400 tons of liquid oxygen and liquid methane, which fuel its 33 engines. Each Raptor engine generates roughly three times more power than the engines used on SpaceX's current rockets.

Upper Stage: Design Efficiency for Deep Space

The Starship, itself, perched atop the massive booster, is slightly shorter, but much sleeker in design. It has a pointed nose, small fins and a black underside due to the heat shield made of carbon-composite tiles. It has only six Raptor engines: three are the same as those used on the super-heavy booster, and the other three are designed specifically for operating in the vacuum of space, rather than within the atmosphere.

A Guide to SpaceX's 5th Integrated Flight Test

• At launch, all 33 engines of the super-heavy booster fires up. Once it lifts off the ground, the Integrated Flight Test-5 (IFT-5)-the fifth test flight of SpaceX's Starship system, which includes both the super-heavy booster and the Starship spacecraft-begins a slow turn towards the southeast as it climbs higher and picks up speed. This manoeuvre helps guide the rocket in the right direction for its mission.
• When the rocket reaches an altitude of over 70 kilometres and is travelling close to 6,000 kilometres per hour, the super-heavy booster shuts down all of its engines except for three. At this point, the Starship spacecraft lights up its six engines for the first time and separates from the booster to continue its flight. Once the super-heavy is no longer connected to the Starship, it changes course to head back towards the launch pad. After adjusting its path, it shuts down its engines.
• As the super-heavy falls back towards Earth, its large 'grid fins', which look like fly swatters, help steer and keep it on the correct path. Near the end of its descent, 13 of the booster's engines restart, slowing it down and stopping it in mid-air. Then, special arms on the launch pad reach out and catch the booster.
• About eight and a half minutes after launch, the Starship reaches 150 kilometres above Earth, moving at more than 26,000 kilometres per hour. At this point, the engines turn off. The spacecraft will then enter the atmosphere again over the southern Indian Ocean. The Starship re-enters the atmosphere with its belly facing down. As it passes through the air, friction slows it down. The heat shield, made of black tiles, protects the spacecraft from the intense heat created during this process.
• As the Starship gets closer to Earth, it flips upright and switches on its engines, and carries out a vertical landing similar to the super-heavy booster. But, unlike the super-heavy booster, there are no arms to catch it.

(The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach him at: [email protected])