What does SpaceX want to do with its Starship?

Oct 11th 2024

Editor’s note: On the morning of October 13th Starship's fifth test flight met all the goals detailed in this explainer.

Elon Musk’s rocket company, SpaceX, launched the fifth test flight of its Starship rocket on October 13th. The 100-tonne Starship is flying halfway round the world from its launch site in Texas, if all goes well to a controlled landing in the Indian Ocean. The massive booster rocket which sent it on its way returned to the launchpad, caught in mid-air by a huge pair of robot arms.

Starship, the first launch system designed to be fully reusable, is central to SpaceX’s plans for the expansion of Starlink, its satellite data constellation; to NASA’s plans to return Americans to the Moon; and to Mr Musk’s vision of a human settlement on Mars. What does this test flight reveal about the company’s capacity to deliver on these long-term goals?

The Starship is launched by a “Super Heavy” booster. This shiny steel cylinder is nine metres across and 71 metres high; it matches a Boeing 747 in length and comfortably outdoes it in girth. It weighs about 200 tonnes when empty; when full it carries about 3,400 tonnes of liquid oxygen and liquid methane to burn in its 33 engines. Each of these, called Raptors, delivers about three times the thrust of the engines used on SpaceX’s existing rockets.

The Starship proper, which sits on top of this beast, is a little shorter but far more stylish; sharp of nose, stubby of fin and, thanks to the carbon-composite tiles of its heat shield, black of belly. It has just six Raptors: three exactly like those on the Super Heavy; three optimised for work in the vacuum of space rather than the atmosphere.

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At lift off, the 33 engines on the Super Heavy ignite. After vertical lift off, IFT-5 will turn gently towards the south-east as it gathers height and speed.

At an altitude of over 70km, flying at almost 6,000kph, the Super Heavy shuts down all but three of its engines. The Starship ignites its six engines for the first time, pulling away from the booster.

No longer attached to the Starship, the Super Heavy changes direction, putting itself on a trajectory that will take it back to the launch pad, and turns off its engines.

As the Super Heavy plummets towards the Earth its fly-swatter-like “grid-fins" keep it on course. At the end of the descent 13 of the booster’s engines fire back up, halting it in mid air, and the launch-pad arms grab it.

Eight and half minutes after launch, 150km above the Earth’s surface and now moving at more than 26,000kph, the Starship shuts off its engines. It will re-enter the atmosphere over the southern Indian ocean.

The Starship re-enters the atmosphere belly first. Friction robs it of its speed; the black tiles of the heatshield insulate the spacecraft from the heat that process generates.

As it nears the surface, the Starship flips itself back to the vertical and starts its engines, performing a vertical landing burn very like the Super Heavy’s—but with no arms waiting to grasp it.

On the first test flight the Super Heavy and the Starship failed to separate. On the second, they separated, but the Super Heavy broke apart and the Starship caught fire. On the third the Super Heavy accomplished the manoeuvres in space needed to bring it down to a designated spot in the Gulf of Mexico where, if it came in out of control, nothing would be harmed. It did indeed come in out of control. The Starship broke up during re-entry.

On the fourth test flight, the Super Heavy managed a controlled vertical “landing” in the Gulf, which is why the company planned to try to bring it back to the pad this time. And despite sustaining a great deal of damage during re-entry, the Starship stayed intact during the last test, flipping itself upright and turning its engines on for a landing burn before it hit.

If this fifth test flight meets all of its goals Mr Musk will have an achievement which actually deserves trumpeting on X, the social-media platform he increasingly uses as an amplifier for his support of Donald Trump and a means of profiting from the spread of disinformation. But it will still be some time before the system is ready for routine operation. The next step will be to send the Starship into orbit before returning it to Earth (which will require it to turn its engines on and off a few more times). Then comes the challenge of bringing the Starship, too, back to the giant robotic arms at Starbase. Once that is done engineers will be able to see how well, or badly, its tiles survive re-entry and so work out what more they need to do to make the craft fully reusable.

If they eventually succeed it will greatly increase the amount of mass SpaceX can launch in a year (an amount which already far exceeds that of any other company or country). That will allow it to put up more numerous and more massive Starlink satellites, greatly increasing the system’s capacity for providing high-speed internet access. It will also allow it to create propellant depots in orbit at which some starships would be able to refuel on their way to the Moon, as required by NASA, and perhaps one day to Mars, as deeply desired by Mr Musk. ■

Sources: SpaceX; The Economist

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