After the most recent test flight, SpaceX is already getting ready for the next with ship heat shield upgrades underway among other prep. Comments from Musk suggest they will be ready in about a month from now with upgraded hardware for flight 5.
While very ambitious, SpaceX does have a few developments going in their favor for a quick turnaround including no mishap investigation from the FAA. That being said, acquiring a possibly modified launch license, replacing a new heat shield, and preparing to launch again is no easy feat. Here I will go more in-depth into new developments that impact Starship’s timeline, how realistic a launch in one month is, what to expect in the coming weeks, and more.
Busy Timeline
A few days ago Musk during a livestream was quoted saying that the “Next launch is probably in about a month.” This is a bold statement but there are a few big things going in SpaceX’s favor. For one, only yesterday it was reported that the FAA will not be requiring a mishap investigation for IFT-4. Specifically, the agency was quoted saying, “The FAA assessed the operations of the SpaceX Starship Flight 4 mission. All flight events for both Starship and Super Heavy appear to have occurred within the scope of planned and authorized activities.”
In other words, the last launch from a technical standpoint didn’t produce any shocking results and despite the ship landing about 6km off its target, this was acceptable and likely accounted for beforehand in a possible scenario. With the booster landing right on target as confirmed by the company, the FAA decided that no investigation was needed. When it comes to launching Starship, the FAA plays an extremely big role in whether it takes a long time or the turnaround is very quick. Since the first launch, both the results of the Integrated Flight Tests and the efficiency between SpaceX and the FAA have improved.
After Integrated Flight Test 1, it took 212 days of work, FAA approval, and preparation until the second launch in November. After that, it only took 117 days to launch a third time after the second attempt. Most recently, SpaceX managed to launch Starship again after only 84 days. Combine this trend with the recent launch meeting just about all expectations and a launch in a month or so doesn’t seem too crazy.
However, there are a few important constraints that could push the optimistic month launch timeframe back. The first has to do with the heat shield replacement. Right now SpaceX is in the process of stripping every single heat shield tile off of S30. Once they are all removed, teams will then add the new ablative material layer which will act as a backup in the event a tile fails at any point during the launch. So far they have made some impressive progress by taking off about 1/3 of the ship’s tiles in close to a day. This suggests complete tile removal in only a few more days and then the new application process would start.
Although, it’s important to point out that removing the tiles is one thing, adding a brand new ablative material across the majority of S30’s body is another. This is a completely new process and something teams have not yet done at this scale. Depending on the exact style of ablative material and how it interacts with the tiles placed on top will help determine if it’s a relatively smooth and simple process or something that takes a lot of time. In the next few days, we might see SpaceX start adding it which would answer a lot of these questions. Either way, the tile and general heat shield change is going to be a time-intensive process that could impact the next launch date.
Another important consideration that could take some time would be a launch license modification. In addition to Elon saying the next launch would be in just about a month, he has also stated multiple times that they want to try and catch the booster on the next attempt. While this is still somewhat up in the air, if they decide to try a catch, it will require a modification involving the FAA. Here the agency would make sure that the booster returning to the launch site for an attempted catch wouldn’t pose any risk to public safety. Since the flight profile would be changed from the previous attempt, this process would take some time and could hold back IFT-5 as they wait for approval. On the other hand, if SpaceX decides to hold off on the catch attempt it would make the process much simpler and faster which is something to consider.
The final factor involves Stage 0 and the Orbital Launch Mount in particular. While the water deluge and steel plate combination have been helping keep everything intact, withstanding 33 Raptor engines is not easy. If SpaceX decides to replace any clamps or relevant infrastructure it could take some time. Thankfully there are plenty of teams and work can be done on multiple projects at once.
Starship’s Heat Shield
Relevant to the next launch, how long it takes, and Starship’s future is the heat shield. Musk recently talked about the challenges of creating a truly rapidly reusable orbital heat shield that could survive reentry and soon after be ready for the next launch. He made comparisons to the Space Shuttle which definitely had some complications related to both safety and time between missions. Specifically, NASA used two categories of Thermal Protection System tiles on the Orbiter—low- and high-temperature reusable surface insulation. Surface coating constituted the primary difference between these two categories. High-temperature reusable surface insulation tiles used a black borosilicate glass coating and covered areas of the vehicle in which temperatures reached up to 1,260°C (2,300°F). Low-temperature reusable surface insulation tiles contained a white coating with the proper optical properties needed to maintain the appropriate on-orbit temperatures for vehicle thermal control purposes. The low-temperature reusable surface insulation tiles covered areas of the vehicle in which temperatures reached up to 649°C (1,200°F).
Unfortunately, tiles often fell off and caused much of the delay in the launch of STS-1, the first shuttle mission, which was originally scheduled for 1979 but did not occur until April 1981. Each tile used cement that required 16 hours to cure. After the tile was affixed to the cement, a jack held it in place for another 16 hours. In March 1979 it took each worker 40 hours to install one tile. Thousands of tiles failed stress tests and had to be replaced. By fall NASA realized that the speed of tiling would determine the launch date. The tiles were so problematic that officials would have switched to any other thermal protection method, but none other existed. The tile TPS was an area of concern during shuttle development, mainly concerning adhesion reliability. Some engineers thought a failure mode could exist whereby one tile could detach, and resulting aerodynamic pressure would create a “zipper effect” stripping off other tiles. Whether during ascent or reentry, the result would be disastrous.
On Starship, when the entire heat shield is installed, there are right around 18,000 tiles in total. The Shuttle for comparison had around 25,000 tiles. The big difference however is that the Shuttle’s tiles were unique requiring extreme precision and complex replacements and refurbishment. SpaceX is using basically a completely uniform tile across almost the entire body of the vehicle. This helps a lot in the time department. The specific material is also more advanced improving the overall process.
Even so, that’s not to say that more work isn’t needed. Musk was quoted saying, “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 on 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. The good news is that even as SpaceX works to improve and alter the heat shield, it still managed to keep Starship mostly intact on the last launch. The steel and now the addition of the extra ablative will give them some leeway going forward.
Before IFT-4, SpaceX took some time to upgrade the vehicles based on flight data from the previous Integrated Flight Test. For example, the company said in a statement, “SpaceX implemented hardware changes ahead of Flight 3 to mitigate this issue, which resulted in the booster progressing to its first-ever landing burn attempt.” As far as upgrades, they said, “Super Heavy boosters for Flight 4 and beyond will get additional hardware inside oxygen tanks to further improve propellant filtration capabilities. And utilizing data gathered from Super Heavy’s first landing burn attempt, additional hardware and software changes are being implemented to increase startup reliability of the Raptor engines in landing conditions.” With how well the last flight went, necessary upgrades could be minimal. This supports a quicker turnaround and a launch that’s not too long from now. No matter the case, SpaceX is going to be very busy over the next few weeks as they prepare for IFT-5. As time goes on we should get even more relevant information and a better idea of when the launch will take place.
Conclusion
SpaceX has already started working on Starship’s heat shield and the process of removing all of its heat shield tiles. The next step involves the application of a new ablative and then attaching the tiles back onto the new surface. This combined with the FAA requiring no mishap investigation and the next launch could be quite soon. We will have to wait and see how it progresses and the impact it has on the space industry.