Starship Flight 4 milestones effect changes to Flight 5’s Ship

by Ryan Weber

Following the highly successful milestones achieved by Booster 11 and Ship 29 on Flight 4 of SpaceX’s Starship, engineers are already implementing lessons learned from the mission ahead of the next flight, including widescale changes to the Thermal Protection System (TPS). Although Elon Musk thinks the next flight is a month away, the Flight 5 pairing requires the reapplication of stronger tiles ahead of its mission.

Starship Flight 4 Rundown

Launch day expectations were high, as SpaceX hoped for a soft splashdown of Booster 11 and survival of peak reentry heat for Ship 29. The tank farm’s road closure and chill down went as planned, and the weather was nearly perfect for a launch.

Ship 29 and Booster 11 lifted off at 7:50 a.m. Central Time. Immediately, Booster 11 had Engine 15, which is in the outer ring, shut down, a deviation from the past two flights, in which all 33 were running. However, this did not affect the booster’s ascent, with the booster completing the ride uphill with no other issues.

Then came staging, where Ship 29 seamlessly hot-staged away from Booster 11. Mere seconds later, Booster 11 flipped and restarted the inner ten engines for the boost-back burn.

Unlike the last flight, all 13 engines ran for the full duration of the burn before shutting down. SpaceX does this to return to the launch site for a catch, but in this case, the target was 20 kilometers offshore in the Gulf of Mexico.

Shortly after the boost backburn, SpaceX debuted a new step in the launch: Teams jettisoned the hot staging ring on top of Booster 11. This was likely done to reduce mass at the top of the vehicle to allow for a smoother glide back. To help this process, SpaceX installed a couple of pneumatic pushers to push the ring away from the booster. It works in the same way as the pusher system in the interstage of Falcon 9 to push the second stage away before Merlin Vacuum ignition. 

Next would come a ship engine cutoff and a nominal Suborbital insertion, Meaning Ship 29 hit the correct trajectory. Shortly after, Booster 11 would start up the inner 13 engines for an initial landing burn before switching to the inner three. 

However, just after ignition, Engine 8 in the inner ring of 10 exploded, but the booster kept on going. Then Booster 11 cemented itself in history as becoming the first Super Heavy Booster in the Starship Program to complete a landing in the Gulf of Mexico. After engine shut down, Booster 11 tipped over and was lost to the sea.

Looking back, Ship 29, which was in its coast phase, had camera downlink issues, but these were resolved in time for reentry. After the coast phase, the ship orientated itself for re-entry, which looked to have a high angle of attack, like the Space Shuttle. This is too slowly starting to bleed off speed with the body of the ship before pitching over and losing even more speed.

This was the start of the questions: Will the heat shield hold? Will the ship be able to maintain control during reentry? Will Starlink provide an uninterrupted signal through reentry?

Slowly, just like with Ship 28, Ship 29 started to get the glow of plasma as the ship hit the atmosphere at over 26,000 kilometers per hour. This happens because the air heats up so much due to friction that it forms into another state of matter called plasma, which is composed of charged particles caused by the incredible energy around the vehicle. 

Now, as Ship 29 passes through the atmosphere, the plasma continues to build up. This is the first time the human race has seen reentry plasma live from external cameras. Ship 29 would make it through peak heating, thus completing one of its primary objectives. However, during reentry, the starboard forward flap, as seen on the external camera, had its bottom actuation arm completely melted off, and the plasma also ate a good chunk out of it. 

However, despite the damage to the flap and to any other systems, Ship 29 would successfully make it through reentry. Next, even after everything it had been through, Ship 29 performed a flip-and-burn maneuver, which was the first time a ship had done one since SN15 over three years ago. The maneuver was a success, with the ship landing on the ocean and tipping over intact.

Flight 4 Issues and What it Means for Flight 5

Looking ahead to Flight 5, SpaceX likely won’t need to make any significant changes to the booster as it successfully landed on target, as confirmed by SpaceX CEO Elon Musk. With this success, SpaceX will try to perform a catch of Booster 12 during Flight 5. The engine out on ascent and the exploded engine on the landing burn will be investigated internally as to the causes. 

Booster 12, which has been in Mega Bay 1 since Jan 23, 2024, is awaiting its turn for a static fire. Currently, there is no timetable on when it might roll out as SpaceX has started to remove the hold-down clamps on the Orbital Launch Mount (OLM) once again.

Ship 29 to Ship 30 is another matter entirely. Now, while Ship 29 did make it through reentry and completed the flip and burn, many issues needed rectifying. First, the plasma burned through the flap seals and nearly cut a flap off. SpaceX will need to find a way to reinforce these areas for future flights. Second, while the heat shield allowed the ship to survive, there are still significant issues to be corrected. 

Because of these issues, Ship 30 is already getting its heat shield tiles and underlying blankets removed and eventually replaced. The underlying blankets would be replaced by a new ablative material that may have debuted on Ship 29. As stated by Elon Musk, the tiles are getting upgraded to a newer, much stronger design. Even though Ship 29 completed the flip and burn maneuver, it was a couple of kilometers off target due to the flap damage.

Adrian Beil for NSF got a response from the Federal Aviation Administration (FAA) in regards to a possible Mishap Investigation for Flight 4: “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.” With no mishap investigation needed SpaceX can push ahead with Starship Flight 5; however, there is no word on whether or not the current license can be used for a booster catch. Considering a landing at the launch site is not included in the current license SpaceX will likely need another modification.

Overall, the launch preparations for Flight 5 will be interesting to watch as SpaceX readies for a catch and aims for a much better performance during reentry. 

Ship 30 Tile Removal Underway (Credit: Mary/BocaChicaGal for NSF)

Orbital Launch Pad B

Construction of the next Orbital Launch Pad (OLP) is gaining speed. SpaceX has the last two sections, along with the chopstick arms and carriage, on their way from Florida. With these parts arriving, SpaceX will only be missing a Ship Quick Disconnect Arm. There is one still at Roberts Road, where SpaceX has been building OLP parts. However, this arm may need to be updated and will probably be built new from scratch at the Sanchez Site. 

Regarding when the tower might start stacking, teams have made significant progress on the foundation, with the Pile Cap of the tower being poured and parts for the crane needed to stack the tower arriving. Unlike the last two towers, SpaceX will not use the Liebherr LR11350 crane but a Demag CC 8800-1, which has more lifting capacity.

Orbital Launch pad B Pile Cap Pour (Credit: Mary/BocaChicaGal for NSF)

A new interesting note about this tower is that the foundation will have hollow steel columns filled with concrete rather than concrete that needs steel shielding added. The Orbital Launch Mount (OLM) will be placed to the south, giving some incredible views once a vehicle is stacked on this new launch pad.

Lead Image: Ship 29 and Booster lift off for Starship Flight 4. Credit: Mary/BocaChicaGal for NSF

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