Musk's new Starship flight test postponed at the last minute

It must serve, in Musk's plans, three specific tasks. Firstly, to bring as many new satellites into low orbit to complete the Starlink constellation, 25,000 of which are still missing, so it is understood that it will have to be launched many times for this. As a second task, it will have to bring men, robots and material of all kinds to the Moon, to build and maintain the lunar city desired with the Artemis programme. When fully operational, we are talking about dozens of launches per month. Finally, when all this is well underway, if it goes ahead as the US president wants, it will have to shuttle to Mars to bring the million human beings, plus everything else that is needed, to populate the red planet, as envisaged in SpaceX's original plans. For this, an upgraded version, reaching a height of 150 metres, will be used.

The next launch, in a few hours ultimately, will therefore be very important to understand whether the Artemis programme, in the latest version radically modified by NASA administrator Iared Isaacman, will be able to keep to the schedule and bring us back to our natural satellite within the decade. We must also highlight another, very important novelty, following the change of tanks and the upgrade of the powerful engines: during the flight, Starship will observe itself 'from outside' thanks to two small 'inspector' satellites, brought into orbit together with 22 mockups of Starlink satellites, in essence non-functional but realistic models.

In the flight description, the SpaceX website states precisely, "The last two satellites released will scan Starship's heat shield and transmit the images to operators to test methods of analysing the suitability of Starship's heat shield for re-entry to the launch site on future missions. Several tiles [of the heat shield] have been painted white to simulate missing tiles and serve as imaging targets during the test."

This is very important: when the vehicles return to earth through the atmosphere, temperatures of hundreds and hundreds of degrees are produced; therefore protecting the spacecraft from this heat that would destroy them is a difficult but unavoidable task.

If in the case of a spacecraft, such as the Orion that returned a few weeks ago from the roundabout around the Moon, it is difficult, in the case of Starship it is much more difficult and at the same time fundamental: the large space capsule, which constitutes the 50-metre second stage, is in fact conceived and designed to be completely reusable in a short time. On the other hand, even without thinking of the Moon or Mars, it is easy to see that if SpaceX has to put 25,000 Starlink satellites into orbit to complete the constellation, the pace of launches will necessarily have to be very frequent, even more than one a week.

While our eyes are therefore on the rocket, SpaceX engineers are anxious about the heat shield of the second module, the Ship, which consists of a gargantuan number of protective tiles: 40,000.

"No one has ever made a reusable orbital heat shield," Musk said in an interview in February, "so, the heat shield has to get through the ascent phase without peeling off tiles, and then it has to re-enter without losing a bunch of tiles or overheating the main structure."

So far, the heat shield has held up well, in previous flights, but it has lost a lot of tiles; therefore, it was not reusable in a few hours. At SpaceX they talk about arrival, refuelling and restarting in a few hours to keep up the pace, almost thinking of Formula 1 motor racing, but of course if the tiles fall off, they need to be inspected and perhaps replaced, and then it takes days, not hours, to replace them. And the launch chain jumps.

That is why, although we spectators will be interested in seeing the take-off and re-entry phases, which are always spectacular, the technicians' eyes will be on the heat shield tiles. 

If all goes according to plan, Starship's first stage will return to land in the Gulf of Mexico about seven minutes after take-off.

The spacecraft, the 'ship' part, will instead ditch in the Indian Ocean, 65 minutes after launch. The two control craft released into orbit will tell us if and how the tiles can hold up to this tight schedule.

These flights, not just those of SpaceX, which are by far the most frequent anyway, are increasingly threatened by the pollution they cause. While we, with our cars or industry, pollute the lower atmosphere by emitting soot, which goes away in the first downpour, rockets carry their produced soot directly into the stratosphere, between 15 and 50 kilometres above the ground. There, there are no major mechanisms to somehow rid us of these particles and the carbon remains suspended for an average of two to four years. We don't breathe it, probably, but it certainly stays there and continues to absorb solar radiation, helping to warm the atmosphere. Which we certainly don't need. One of the many problems to be solved if we want to keep going into space.

If all goes well, however, the Moon will finally be a little closer as a goal.