In the few days since Starship’s fourth flight test, we’ve received snippets of information from Musk along with the company highlighting new details and future plans. Most recently, during a livestream Musk was hosting, he talked about plans to add an additional ablative material under all of Starship’s existing heat shield tiles.
The goal here would be to add extra protection in the event that a tile breaks or falls off during any process in the launch. If that wasn’t enough, he also estimated the next launch would happen in about a month from now. Here I will go more in-depth into the highlights of what Musk said, work on the heat shield, preparing for reentry, and more.
Heat Shield Upgrade
As many have seen by now, during the last flight, Starship’s upper stage managed to make it through Earth reentry despite a weak point between the flap and the main body of Starship that nearly destroyed the flap. Starship managed to complete its landing burn anyway with the flap still actuating however that obviously is not the intended outcome going forward.
In regard to this, besides Musk saying that they predicted the area of failure and would have an easy fix, he also talked about a change to the entire heat shield of Starship as well. During his Livestream, he was quoted saying, “We’re going to replace the whole heat shield on the ship. So the new heat shield tile is about twice as strong as the ones that were on the last flight. We want to put an ablative secondary structure, basically ablative protection behind the tiles so that if the tiles crack or come loose it doesn’t cook the rocket.”
These initial comments are quite a big deal as they mark a significant change in the heat shield structure and even design. For more context, in the past the tiles were attached directly to the ship which poses a few risks in the event they fall off or break. While steel is a great material for reentry compared to other common rocket build options, it alone is not enough to keep Starship perfectly intact and capable of a controlled reentry. While this additional material will add some weight, in the grand scheme of things it should also make the vehicle much more reliable, with Musk saying it wold be twice as strong. You also have to consider that with future plans to carry humans on this spacecraft, reentry needs to be very safe and have backups in the event of a tile failure.
In another quote, Musk said, “It’s pretty incredible that the rocket made it all the way to the ocean despite the front right flap getting cooked very hard. But for the next flight, we want to not have the tiles fly off and have a skeleton flap. So the new tiles like I said about twice as strong or hopefully half as likely to crack or come off.” He continued by saying, “We ran two experiments with tiles on this flight which people may have noticed cause there were missing tiles, they were intentionally missing because we were testing the secondary heat shield material which is like a silicone felt ablative” he said. Looking at images before the flight these missing tiles were obvious toward the bottom of the ship. What wasn’t quite clear was the addition of the ablative material which must have performed well in those specific areas considering SpaceX is now adding an entire layer behind the tiles of the next ship.
Musk went on to clarify in another quote, “Its not good for reuse but it’s good for saving your butt if a tile cracks or falls off. It’s very tricky to put these tiles and have them work well because the tiles are ceramics, they are like a coffee cup or a dinner plate. So you have a whole bunch of dinner plates of a rocket that is shaking. It’s shrinking cryogenically with the propellant and then expanding under pressure and then the tiles are expanding when they get hot. So there’s a lot of expansion and contraction happening while trying to keep all these brittle tiles from cracking or breaking off” he said.
He went on to talk about the challenges of making a reusable orbital heat shield, citing the Space Shuttle taking months of work between flights to fix and repair its heat shield. What’s clear from these comments is that they are still struggling a bit with the main heat shield tiles themselves as far as keeping all of them secure and in one piece throughout the entire launch process. This being said, the new ablative material in combination with the rocket’s steel construction is expected to provide a significant safety barrier if a few tiles were to fail. As far as his comment on the ablative material not being good for reuse, this makes sense as its a safety net but forces the company to improve the primary tiles going forward. The goal for Starship is rapid reuse, this obviously would not be possible if after each landing the rocket needs repairs to the underlying ablative material and also adding back tiles that went missing.
Fortunately for SpaceX, they are still in the early stages as they continue to test and make improvements to the vehicle. Based on the last flight they seem to be on the right track which is a promising sign. Now that they can get Starship to orbit on somewhat of a regular basis, they will be able to test new materials and combinations to find the best balance of rapid reusability, weight, and consistency. Something we can expect to see on the next flight.
Launch In 1 Month
In addition to all the comments on Starship’s heat shield development, Musk also made some bold estimates relative to the next launch timeline. In the live stream, he was quoted saying, “Next launch is probably in about a month.” Considering this live stream was yesterday that would put the next flight as soon as mid to late July. While the time between Starship’s launches has been improving, this estimate from Musk might be a bit ambitious. It should definitely be taken with a grain of salt however it still helps put things into perspective. If he genuinely belives that in about a month from now, they should be ready, it means a launch in as soon as two months would be nearly guaranteed by his standards. That’s a good sign that the work needed is relatively straightforward. The main items include adding the layer of ablative material and then the tiles on top.
The other specific fix had to do with the seal where plasma initially broke through and damaged the flap. In regard to that change, he initially tweeted that they would have this nailed for the next flight and that it didn’t seem to be a very significant alteration.
He even said again that they still want to catch the booster on the next flight. Specifically, he was quoted saying, “Unless something comes up that we think is problematic we will try to bring the booster back and catch it with the giant Mechazilla arms.” He then made it clear that during the attempt excitement would be guaranteed while success not as much.
Another detail from this livestream combined with other tweets and comments from the past few days suggests that only the one flap was damaged. Whenever mentioning the damage it was always singular rather than plural. If that is the case and only the flap shown on camera was damaged, it would be an even better sign as the others held up even with the current heat shield system. With heat shields, a tiny weakness can easily become a disaster for the entire vehicle. Something similar happened on the last flight with the flap shown.
Based on everything said, we should expect to see SpaceX get very busy in the coming weeks in preparation for another launch. The launch pad seems to be in great shape including the water delgue and steel plate. This system has now been used for three launches and seems to be holding up nearly perfectly. Combine this with the added protection around the launch mount itself and all the plumbing going throughout the tower, and Stage 0 looks to be in a great state.
Funny enough, if SpaceX does end up attempting a catch next flight and it doesn’t go well, some of this infrastructure could definitely get damaged. On the bright side, by the time the booster is lighting its engines for a final landing burn, it has nearly nothing left in its propellant tanks. This would help avoid a massive explosion if things were to go wrong. It is still however a gigantic heavy metal booster so the tower or mount could easily be damaged. As we get closer to the launch date SpaceX will eventually confirm or deny the attempt to catch Super Heavy.
In a post-launch report, SpaceX said, “Starship’s fourth flight test launched with ambitious goals, attempting to go farther than any previous test before and begin demonstrating capabilities central to return and reuse of Starship and Super Heavy. The payload for this test was the data.” Musk made it clear that they got a lot of incredible data from Flight 4. He pointed out that both the soft landing of the booster and upper stage was about a 20% lucky event based on their initial expectations. With this came even more data they can apply to the next mission to try even more ambitious things. A process we can hope to see not too long from now. Once the catch process is attempted, depending on how that goes, it could become somewhat of a regular occurrence. From there we can hope to see the ship actually returning for an attempted touchdown on land. With Artemis getting closer among other missions, the faster Starship becomes operational the better.
Conclusion
SpaceX has decided to add an additional heat shield layer in the form of an ablative material under the primary heat shield tiles. The goal is to add a safeguard and ensure the ship survives reentry in the event a tile is broken or falls off. This combined with the steel body should make Starship a much more reliable vehicle. We will have to wait and see how it progresses and the impact it has on the space industry.