Not even a week ago we witnessed the fourth flight of the Starship (IFT-4) with the Super Heavy B11 and the Starship S29 and new developments have not stopped happening in the always exciting, changing and sometimes controversial world of SpaceX. The IFT-4 mission was the first of the Starship system that we can call successful in that all the mission objectives were met: B11 landed gently in the Gulf of Mexico and Starship S29 did the same in the Indian Ocean, after survive reentry and carry out a vertical maneuver and restart the Raptor engines. For the first time in history, both stages of an orbital rocket returned to Earth in one piece. Following the lack of attitude control experienced by S28 on the third mission, SpaceX introduced several improvements to S29 to avoid this situation, including a new pair of spin control thrusters located under the cargo hatch. In this sense, and despite a very striking venting that could be observed during the suborbital trajectory, it is clear that the Starship’s attitude was controlled.
As for the heat shield, the results are a bit contradictory. On the one hand, S29 survived reentry—despite not having three tiles purposely installed on the bottom to collect data on the ship’s behavior—leaving critics who had predicted that a such an unsophisticated heat shield was doomed to failure. On the other hand, it became clear that the shield suffers from weak points, especially, and predictably, in the joints between the flaps and the fuselage. Most of the Starship’s hexagonal tiles are mechanically attached using three attachment points, but there are areas, such as the nose and two strips of segments with reinforcements of the cylindrical structure, where they are attached with glue, as on the space shuttle. And, just as happened to shuttle, these areas are giving technicians headaches. On S29 SpaceX experimented with a new red adhesive material different from the blue we had seen so far, as well as scraping the steel surface to help grip, but it is unclear to what extent these measures have been a success.
The fact is that the right front flap fulfilled its function despite the gap in the gasket and the subsequent disintegration of the rear part. The flap was even able to open during the landing maneuver. back flip before landing, although it was his last death breath and during the maneuver the forward connection failed. Despite everything, the flap was still attached to the S29 when the image was lost. The key is to know how the rest of the structure of S29 looked after the adventure. The S29 only had two external cameras to see the fuselage: the camera that gave us views of the right front flap, located inside a special tile, and another camera at the end of the left flap that had the port fuselage as a field of view. and the left rear flap. However, the left flap camera apparently did not transmit images of the final phase reentry.
In any case, Elon Musk has stated that the left flap suffered less severe damage than the right, although it was also affected by reentry (the S29 also had cameras in the engine compartment and another for the external side view, but they have not been published images of them in the re-entry). The S29 splashed down in the Indian Ocean in the middle of the night and it is possible that the FTS was activated to make the pieces sink more quickly. Be that as it may, one of the improvements that SpaceX is going to introduce in the next ship, the S30, is to change the current tiles for more resistant ones (“twice as resistant to heat”, whatever that means exactly), a process which has already started (by the way, the S30 does not have a camera to see the front right flap, although after the success of the S29 camera it would not be surprising if a similar one were added). An ablative material under the tiles will protect the fuselage if the tiles fail (it is not clear if this material was used on S29).
As for the Super Heavy B11, let us remember that it suffered the loss of one Raptor from the outer ring (the ones that are fixed and only light up once) and then one of the thirteen mobile Raptors from the second ring failed during the braking ignition (these Raptor They light up three times: takeoff, return lighting, and braking lighting for landing). In the launch day video we could see fragments breaking off from the base of the B11 during the braking burn, probably parts of the failed engine. SpaceX published a few days later a spectacular video of the splashdown of the enormous B11 filmed from a buoy. The fact that the buoy was in the right place corroborates Musk’s statements pointing out that the descent of the B11 was very precise (he did not specify how much). So much so that Musk has confirmed that on the next flight an attempt will be made to capture the Super Heavy with the arms of the launch tower (on the other hand, the S29 landed quite far from what was expected – a couple of kilometers – due to the structural failure in the flap). ; once again, no precise error figures have been given).
Of course, in the same video you can see that the B11 suffers a fire almost until it comes into contact with the water, probably due to a fuel leak caused by the failure of the Raptor in the second ring. Certainly, the announcement of capturing the Super Heavy with the turret on the next flight has surprised many, including myself, even though the maneuver is relatively safe. First, because, as is done with the returns to dry land of the Falcon 9 stages, the descent trajectory is chosen in such a way that if something goes wrong, the stage ends in the water. Second, because during the braking ignition the Super Heavy only carries a fraction of the initial propellants, so a possible explosion would not be apocalyptic. Let us remember that for the landing maneuver the Super Heavy carries propellants in a relatively small liquid oxygen tank of 3 meters in diameter located inside the base of the main oxygen tank (the lower one), while it uses the methane accumulated in the pipeline. transfer from the methane tank (the upper one) to the engine compartment (in the same way, the Starship uses the propellants from the two small front tanks, located in the cone of the vehicle, for landing).
However, the Super Heavy may suffer a failure in its Raptor or guidance system at the last moment, causing it to crash into the tower, launch pad, or other facilities. Although the damage should not be enormous, it can force the delay of subsequent missions, not to mention the possible environmental impact. In any case, many rumors suggest that SpaceX plans to totally or partially demolish the orbital launch tower and platform due to construction defects and in order to optimize it for the next version of the Starship, Starship 2, a launcher larger and more powerful that will allow us to recover the original load capacity of the system (100 tons in the reusable version) now that we know that the current version can only place about 50 tons in low orbit (it is possible that the capacity has increased in the last mission or in the next ones if the Raptor generated the maximum thrust). In that case, a crash of the Super Heavy against the tower would not be so dramatic… from Elon Musk’s point of view, of course. Musk estimates the probability of success of the maneuver on the next mission at 50%.
Meanwhile, work on the second orbital launch tower continues a short distance from the first, a tower that will incorporate several improvements and will employ shorter capture arms in the Mechazilla system to allow them to move faster (the segments of the second tower (they have been taken to Texas by barge from the SpaceX facilities in Florida). Despite rumors, this second tower will be used for launches and not just stage pickup. Curiously, just a day ago we learned from an environmental impact report that SpaceX does plan to build a tower only for stage collection on ramp 39A of the KSC in Florida. In that same report, more information is given about the characteristics of Starship 2: it will carry 35 Raptors in the Super Heavy instead of 33 and, as we already knew, 9 Raptors in the Starship instead of the current 6. Starship 3, the “definitive” version that will be able to place up to 200 tons in LEO and will be 150 meters high, will carry 4,100 tons of propellants in the Super Heavy and 2,600 tons in the Starship. The first Starship launch from 39A is planned for the end of 2025. SpaceX plans to carry out up to 44 annual Starship launches from these facilities in the future.
When will Starship 2 enter service? Well, there are Starships from version 1 to S32, so the logical thing is that from the seventh mission onwards, but there could be changes. The first Starship V2 may also be released by Super Heavy V1. We will know soon. In addition to recovery, the priority for SpaceX right now is to demonstrate that it can perform a brake burn before reaching orbit, something it should do at IFT-5, which Musk says will take place in a month (I I bet on August). On the other hand, Musk has gone up and said that he could launch a Starship to Mars within three years. This surprising statement came following the splashdown of S29. Since only the front tanks will be used to land on Mars, well isolated and safe from losses, nothing prevents trying it. Obviously, it would be an unmanned mission and its duration would be two to four months (Musk did not enter into the nightmare that will entail certifying a Starship according to current planetary protection protocols).
But the priority for NASA is not Mars, but the Moon. Starship is to launch the HLS lunar module for the Artemis III and IV missions. And to do this, it must demonstrate that it is capable of transferring fuel in orbit (remember that these missions will launch the HLS, an orbital depot and several—ten?—cargo Starships to deliver propellants to the depot, which, in turn, will finally will transfer the propellants to the HLS). In 2025 SpaceX has to demonstrate this capability for the first time through two Starship launches in a row. First, one Starship equipped with an active docking system will be launched into orbit and then another, equipped with a passive system, will be launched, which will dock with the first and transfer fuel. For NASA, this recharging capacity is an absolute priority ahead of reuse. After all, you can launch an HLS to the Moon with a set of disposable Starships. Whether SpaceX can have the HLS ready before China puts two human beings on the Moon before the end of 2030 depends on this mission and the following ones.
References:
- https://www.faa.gov/media/80626
