SpaceX Starship's fourth test flight: What you need to know

SpaceX is getting ready for the fourth test flight of Starship, currently scheduled for Thursday, June 6 with a launch window opening at 7 AM CT (but this is, of course, pending a launch license from the FAA). Let’s go through what went right (and what didn’t) with the third flight, the plan for this upcoming flight, and my thoughts for what needs to happen for this flight to be successful.

Starship is SpaceX’s super heavy lift rocket and spaceship combo — it will be the biggest and most powerful operational rocket ever constructed when we are past these flight tests. Starship is also crucial to NASA’s Artemis program to return humans to the moon because HLS, the lander that will take astronauts from lunar orbit to the surface of the moon and back again, is a variation on Starship.

What happened during Starship IFT-3

Starship’s third test flight was back on March 14. For that flight, ascent for both stages went smoothly. The stage separation was successful, and Super Heavy started its boostback burn to return to Earth for a controlled landing in the Gulf of Mexico, while Starship continued its flight.  Well, during the boostback burn, initially all 13 engines first properly, but six shut down early. That triggered a shutdown of the boostback burn early, and then when the rocket tried to initiate the landing burn, those six engines were disabled and therefore didn’t fire. 

SpaceX has determined that those six engines shut down early due to a filter blockage where liquid oxygen is supplied to the engines. It’s notable because this has been an ongoing problem — during Starship’s second test flight, when Super Heavy initiated its boostback burn, several engines shut down because of this exact problem. SpaceX implemented hardware changes within the booster’s oxidizer tanks after that second test flight to hopefully correct the issue.

SpaceX credits these changes for the reason that the booster was able to make it to the landing burn, and is now making additional hardware changes within the oxidizer tanks to hopefully ensure that this doesn’t happen again. Additionally, SpaceX is making hardware and software changes to further support relighting the Raptor engines during the boostback and landing burns.

Meanwhile, Starship entered its coast phase successfully but it lost attitude control a few minutes later. This wasn’t a big deal, in that Starship’s trajectory ensured that it would land in its landing zone without any further intervention, but SpaceX additionally noted that there was much higher than expected heating on both protected and unprotected areas upon re-entry because they weren’t able to control the attitude of re-entry. 

SpaceX has generally had problems with Starship’s heat tiles — they’re reusable but they’ve fallen off the vehicle in surprising amounts during these test flights. According to the broadcast for IFT-3, the vehicle has around 18,000 heat tiles and the heat system is fully reusable (unlike the Space Shuttle, which had heat tiles that had to be fully replaced between each flight). 

Believe it or not, SpaceX thinks this issue was also related to a blockage — in this case, a clog of the valves responsible for roll control. SpaceX added roll control thrusters and upgraded the hardware to hopefully avoid blockages in the future.

The plan for IFT-4

So that’s where we stand for this fourth test flight. SpaceX has made clear that the plan for flight 4 is to successful splashdown of both the Super Heavy booster and Starship, with the company’s eye turning now to return and reuse, rather than achieving orbit — because they did that on flight 3. They’ve incorporated multiple hardware and software changes to achieve this.

Interestingly, one of those changes is jettisoning Super Heavy’s hot staging ring after the boostback burn to reduce the mass of the booster for that last part of the flight. Hot staging is when the second stage ignites its engines to move away from the first stage before separation is complete to pull away from the booster. This was an upgrade made after Starship’s first test flight, when the two stages failed to separate. 

My guess is this is temporary while they work to achieve a successful return of the booster, because jettisoning this across the long term this would impact SpaceX’s plans for rapid reusability.

The profile for the fourth test flight is similar to the third.

The landing zone for Super Heavy is in the Gulf of Mexico, while Starship will land in the Indian Ocean. Neither will be recovered for this flight, though SpaceX’s CEO did say that if they achieve a successful return for Super Heavy, the fifth test flight might include a Super Heavy landing back at Starbase. 

But wait! We still need a launch license

As I mentioned before, this is all dependent on getting a launch license from the FAA. The FAA still hasn’t closed their mishap investigation into IFT-3 (which is absolutely routine when a mission doesn’t complete its objectives, it isn’t a signal that anything went wildly wrong with that third test flight), but SpaceX has argued that they don’t need to for the purposes of this launch. Because there was no debris outside the hazard areas and public safety wasn’t impacted, it’s possible the FAA will just modify the existing Starship launch license and allow them to launch on June 5. It’s also possible the FAA won’t, so we’re basically just waiting to see what happens on that front.

Why I consider a test flight different than an operational flight

It’s interesting because the company draws such strong opinions, I’ll get harsh criticism no matter what I say — but I do honestly think that third was successful, even if they didn’t achieve a successful return for either the booster or the upper stage. One thing that SpaceX is doing that most rocket companies don’t is iterating and testing in public. Let me explain — for Artemis I, NASA’s first mission of their Artemis program, that was the first flight of SLS. Ever. There were no demonstration or test flights for that launch vehicle.

But, it’s important to note: That was not a test flight, it was an operational flight. For an operational flight, you expect everything to go relatively smoothly. While yes the first flight of any rocket or spacecraft is going to have little unexpected issues crop up here and there, if it’s an operational flight the expectations are just very different than if it’s a test flight.

In contrast, this is the fourth test flight of SpaceX’s Starship. They handle testing very differently than what we’re used to from NASA — and that’s ok. It clearly works for them. But that also means that my expectations for a Starship uncrewed test flight at this stage are very different than, say, the Boeing Starliner crewed flight test. (There were uncrewed flight tests for Starliner, to be clear, as is necessary for crewed flight — and if you’re putting people on a rocket, that thing had better be safe.)

This is not me being a SpaceX apologist, as I’ve been accused of. I have no problem criticizing the company when I think things are messy (and they are messy a lot). This is just how spaceflight and rocket testing works.  So if SpaceX gets further than they did on the third test flight, and accomplishes more objectives, I’ll probably consider this fourth test flight successful, even if they don’t nail every part of it.

However, it’s about time to figure out the re-entry element

That being said, I DO think at this point they need to demonstrate successful re-entry. Part of the reason many of us are watching Starship so closely is what I mentioned before, that HLS, or the human landing system, that will take astronauts from lunar orbit to the surface of the moon on Artemis III (currently scheduled for September 2026) is a modified version of Starship. For more on the timeline of the Artemis program, check out my newsletter. This means that SpaceX has to get Starship operational in order for NASA to land humans on the moon. 

NASA already delayed Artemis II and III earlier this year — the timeline was too aggressive internally, but also NASA cited delays from partners like SpaceX in getting their spacecraft ready.

I guarantee you NASA is going to be watching this fourth test launch very closely to see if there’s progress, and in some ways it feels like there’s more pressure on this launch than previous ones because of that. On May 23, NASA Administrator Bill Nelson participated in a congressional hearing about NASA’s FY 2025 budget request, and his choice of language about Artemis III was very interesting — he basically said that whether Artemis III landed on the moon would depend on if SpaceX had HLS ready for the mission.

That means that NASA is likely having internal discussions about not having the Artemis III crew make the moon landing, and instead pushing that to Artemis IV (currently scheduled for 2028). I highly doubt anything will be decided for sure before next year, but if SpaceX doesn’t achieve successful re-entry on this flight, it may start to have larger repercussions.