As IFT-4 prepares for launch, Starship's future is coming into focus - NASASpaceFlight.com

Following the successful static test firing campaigns of the ship and booster, both vehicles are in the Starbase production area being worked on to prepare for the upcoming fourth flight of Starship itself.

Ship 29's static test firing at Starbase suborbital pad B on March 25, 2024. (Credit: BocaChicaGal for NSF/L2)

Ship 29 fired all six engines for a few seconds during a static fire test at the suborbital launch pad B on March 25, to test the ship's systems and engines for flightworthiness.

This test was followed two days later by a single-engine Raptor firing from Ship 29's header tanks, possibly to test the process for firing an engine in space during IFT-4. Once this firing was done, Ship 29 returned to the Starbase production site on March 29 for its flight preparations.

Booster 11 was rolled out to the orbital launch pad on April 3 and lifted up onto the orbital launch mount (OLM) overnight. After Booster 11 successfully conducted a 33 engine static test firing on April 5 it was rolled back to the production site two days later. Both vehicles are currently being prepared for flight, but some work remains before they can come back out to the launch pad.

Booster 11 conducted a successful 33 engine static fire test on April 5, 2024. (Credit: BocaChicaGal for NSF/L2)

The hot staging ring for Booster 11 is still not installed on the vehicle as of the time of writing, and Ship 29 has had many of its tiles stripped off after it was rolled back. Some areas of the ship have been seen with adhesive patches, as these areas require the tiles to be glued on.

Other areas of the ship can have tiles mechanically attached. As of mid-April sizable areas of Ship 29 were still devoid of tiles. However, new nose tiles have been added, and work is proceeding for a rollout in a matter of weeks.

The main goal of IFT-4, as stated by Elon Musk in a post on the social media app X (formerly Twitter), was to have Ship 29 reenter the atmosphere and to have all of its systems working past the point of maximum heating. SpaceX wants to give Ship 29 its best chance of reentering the atmosphere intact, and additional work on the heat shield is being done to that end. 

A section of Ship 29 with visible adhesive, awaiting tile replacement. (Credit: BocaChicaGal for NSF/L2)

IFT-4 is planned as a near-copy of IFT-3's flight, with a similar flight path and reentry over the Indian Ocean. One important goal of IFT-3 that was not achieved was an in-space restart of a Raptor engine, so that is something to watch for on this flight. Another item to watch is how well the booster's return to a point in the Gulf of Mexico near the launch site goes. On IFT-3, Booster 10 made it most of the way down before facing control issues during the final moments of the flight.

During the Super Heavy booster's return to Earth, 13 engines initially fire to slow the vehicle down. Only three engines will be firing during the final descent and landing. For IFT-4, Booster 11 is planned to conduct a return to a "virtual tower" in the Gulf of Mexico, testing the entire procedure of flying within reach of the launch tower and its "chopstick" arms without risking the actual tower or launch infrastructure at Starbase. If this test works well enough, it is possible an actual catch attempt will be made at the Starbase orbital launch tower during the fifth test flight of Starship sometime this summer.

The Mechazilla "chopstick" arms during a recent upgrade to prepare for booster catch attempts. (Credit: Sean Doherty for NSF/L2)

Another aspect of IFT-4 preparations is underway at the orbital launch tower and OLM. Work is underway to prepare the OLM, launch tower, and the Mechazilla "chopstick" arms for IFT-4 and flights beyond. Mechazilla in particular has had much work done to it, including to its hydraulic actuator, which was replaced with an upgraded actuator very recently.

This upgrade presumably is to prepare the "chopstick" arms to catch the booster by enabling them to close more quickly during booster catches.

The quick disconnect (QD) arm for the booster is being worked on and some parts are being replaced, while the hold down clamps on the OLM have been removed for additional work. The ship QD arm also now has had some work done on it, and tank farm piping has been flushed.

The concrete berm has had maintenance work and refurbishment. In addition, more concrete is being poured at the tank farm to construct a new wall. This wall will reduce visibility into the site. The tank farm may also have its vertical tanks removed in the coming months as horizontal tanks more suitable for the storage of methane needed to be installed in their place.

Tanker trucks have recently delivered consumables to the site, such as liquid nitrogen, liquid oxygen, and liquid methane, in preparation for IFT-4 as well. Additional tankage was installed at the launch site prior to IFT-3 to allow more flexibility in operations.

Frame of an animation showing a booster coming in for a catch attempt by the "chopstick" arms on the launch tower. (Credit: SpaceX)

UPCOMING FLIGHTS

If everything goes well on IFT-4, the fifth Starship launch could happen sometime this summer. IFT-5 may feature the first ever attempt to catch a booster at the launch tower, but SpaceX is not ready to attempt this with the ship just yet. The company requires two successful soft landings on water before an attempt will be made to catch the ship with the launch tower, so it is not likely that will happen this calendar year.

The boosters and ships for flights after IFT-4 are being worked on at the production site, and Ship 30 has been seen in Mega Bay 2 with all six of its engines now installed, while Booster 12 is now in Mega Bay 1 undergoing engine installation. The Ship 30 and Booster 12 combination is expected to fly on IFT-5, or whatever it ends up being called.

Booster 12 and Ship 30 at Masseys. (Credit: Sean Doherty for NSF)

Ship 31 is stacked inside the High Bay, and is awaiting future testing at the Masseys test site. Booster 13 is in the back of Mega Bay 1 and is fully stacked. This combination could fly on the sixth test flight of Starship, while Booster 14 is expected to fly on the seventh test flight. This test flight may be done with Ship 32 on top. That ship, the last Starship before version 2 of the system is introduced, is in the "rocket garden" while Booster 14 is being stacked in Mega Bay 1.

SpaceX has been planning for as many as nine Starship flights this year, as per the FAA's Administrator for Commercial Space Transportation Kelvin Coleman. IFT-4 would be the second Starship flight of 2024, while five Starship flights per year are currently allowed from Boca Chica after the final programmatic environmental assessment for the site was passed in mid-2022. The company has applied for a waiver from the FAA.

Ignition as Starship begins the IFT-3 mission. (Credit: BocaChicaGal for NSF)

The time between Starship launches has shortened from nearly seven months between IFT-1 and IFT-2 to just under four months between IFT-2 to IFT-3, while Booster 11's static test firing took place just 22 days after Booster 10 launched from the OLM on March 14. IFT-4 is being targeted for sometime in May, and could fly just two months after IFT-3.

A cadence of one Starship launch every two months for the rest of the year could see IFT-7 - or whatever it is to be called - taking place in November for the fifth Starship flight in 2024, so further improvements in processing - plus the FAA waiver - would be needed to make nine Starship flights this year.

A new office building under construction at Starbase. (Credit: BocaChicaGal for NSF/L2)

STARBASE INFRASTRUCTURE

Besides the work on ships and boosters, Starbase itself is getting upgrades. Starbase, which was a small site with makeshift production tents just a few years ago, is now a very important facility for SpaceX. A key part of the company's future plans for Starship is a giant factory known as the "Starfactory", which is under construction at Starbase but has already started production of Starship elements.

An office building is under construction by the Starfactory, while a parking garage is being built near the "rocket garden" where several ships are stored. It is not yet known which SpaceX work groups would use the new office building.

Masseys Site (Credit: Jack Beyer for NSF)

While the production site's skyline is changing, segments of a new launch tower are waiting at the Sanchez site for assembly. This new tower, to be built where suborbital pad B is now, would also be a dramatic change to the skyline. 

The Masseys site, a former gun range purchased by SpaceX, is also being upgraded. Already capable of conducting cryogenic proofing tests on boosters and ships, Masseys is being equipped to handle static test firings of ships. A flame trench is being installed to allow Masseys to replace suborbital pad B as the engine testing area for new ships, possibly by the end of this year. 

At Starbase, @ElonMusk provided an update on the company's plans to send humanity to Mars, the best destination to begin making life multiplanetary pic.twitter.com/PiX8XOgQs5

— SpaceX (@SpaceX) April 6, 2024

STARSHIP'S CURRENT CAPABILITY 

Starship itself - and the Raptor engine that powers it - is also being upgraded, with versions 2 and 3 of the system in work. The Starship launch system, for all its size and power, is still a work in progress. Although Starship is designed to launch at least 100 tons to orbit and still be fully reusable, Booster 10 and Ship 28 together were only capable of carrying 50 tons to orbit for IFT-3 - similar to the capability of Falcon Heavy - if there had been a payload.

New information shown on a slide during a talk by Elon Musk at Starbase shows that the IFT-3 stack's Super Heavy booster stage only produced 7,130 tons of thrust - 216 tons of thrust per Raptor - rather than the 7,590 tons that would be produced if each Raptor were generating its rated 230 tons of thrust for the sea-level Raptors used on Super Heavy.

For IFT-3, the engines would have been throttled back to 94 percent at liftoff, likely to save engine wear and increase chances of a successful flight.

A slide showing performance numbers for Starship versions. (Credit: SpaceX)

Ship 28 also showed reduced performance on IFT-3, when compared to its rated capability. The SpaceX website lists a rating of 258 tons of thrust for the vacuum-optimized Raptor engines as well as 230 tons of thrust for the sea-level Raptors. Since Ship 28 - and all other ships up to and including Ship 32 - have three sea-level and three vacuum-optimized Raptors each, the total thrust should be well over 1,450 tons. 

However, Ship 28's total thrust was listed on a slide as being just 1,250 tons. This means that there was an average of just 208 tons of thrust per Raptor engine, with the sea-level engines generating even less than this figure. If these figures on the slide were correct, that means that Ship 28's engines would also have been throttled down in comparison to what they are capable of.

Shutdown of a Raptor vacuum engine in slow motion. The engine's nozzle is sized for use by Starship in the Earth's upper atmosphere and outer space, so operation at sea level and low chamber pressures results in flow separation creating visible rings in the exhaust pic.twitter.com/1Z42WIRnX7

— SpaceX (@SpaceX) April 10, 2024

STARSHIP UPGRADES

While Starship is currently capable of flying a payload similar in mass to Falcon Heavy - and to fly up to 100 tons to orbit in expendable mode with an upper stage similar to the finless and tile-less Ship 26 - that is not the objective of the system.

Therefore, version 2 of Starship is about to start flying as early as later this year or early next year, and version 3 of the system is in development for the future. Starship version 2's ship, featuring uprated engines and increased propellant capacity,  and possibly modified fins, likely will make its debut with the eighth flight of Starship. This flight could happen later this year or early next year, if the presumed booster and ship pairings for the upcoming flights are correct.

This appears to be a development tank dome. (Credit: Jack Beyer for NSF/L2)

The next versions of the ship and booster will both have modest stretches, but also possibly redesigned tank domes to help them carry more propellant. The next version of the booster may not make its debut at the same time as the next version of the ship.

The full Version 2 vehicle is intended to bring Starship's payload capability back to over 100 tons in fully reusable mode. To achieve the needed performance gains, this version's booster - just over one meter taller than the current booster - is intended to carry up to 3,650 tons of propellant compared to 3,300 tons on the current version of Starship. In addition, the booster's thrust would increase to 8,240 tons from 7,130 tons for the current version. This implies that the booster's Raptor engines would generate 250 tons of thrust each.

Close up of a Starship section showing a changed payload bay door location. (Credit: Jack Beyer for NSF/L2)

The version 2 ship, just under 2 meters taller than the current ship, is currently intended to carry 1,500 tons of propellant as opposed to 1,200 tons on Ship 28.

The stretch alone is not enough to account for all of the propellant increase, so the tanks would need to be extended to the point where they would encroach into space where the payload bay currently is. A development section has, in fact, been seen with the payload bay door moved forward compared to the current design, along with a flatter tank dome.

Version 2's ship will have three sea-level Raptors and three vacuum-optimized Raptors, the same as on Ship 28 and its siblings. However, the ship's total thrust is going to increase to 1,600 tons of thrust from 1,250 tons on Ship 28, with an average of 266 tons of thrust per engine. Either an uprated version of the current Raptor 2 engine or a throttled down Raptor 3 engine would be needed for both the ship and the booster to meet version 2's performance targets.

VERSION 3 - THE BEAST

Starship version 2 is not the ultimate development for the Starship program. Version 3, designed to be capable of around 200 tons to orbit in fully reusable mode, is on the drawing board though no timeline is yet known for its introduction into service. 

Starship version 3, to meet its lofty performance goals, is going to be powered by upgraded Raptor engines and will be substantially taller than earlier versions of Starship. Launch and testing infrastructure at Starbase and in Florida will need to be upgraded to handle this version - and likely the upcoming version 2 - as well - which explains the need for a flame trench at Masseys.

From left to right: Starship versions 1, 2, and 3. (Credit: SpaceX)

Version 3's booster, over seven meters taller than Booster 11 and its siblings, is intended to have a propellant capacity of 4,300 tons. In addition, the total thrust generated by the booster would be a whopping 10,000 tons, which would mean around 300 tons of thrust per engine. To put this in perspective, the Saturn V generated just under 3450 tons of thrust from its first stage.

Raptor 3 currently is stated to produce 280 tons of thrust per for the sea-level version or 306 tons of thrust for the vacuum-optimized engine, so an upgrade of Raptor 3 or a new version of Raptor after Raptor 3 would be needed to meet the performance required for this level of total thrust from the booster. Besides the Raptor 3's thrust increases, this version also features a simplified, more compact design allowing boosters that use it to dispense with engine shields.

Falcon Heavy launching the Psyche asteroid probe on Oct. 13, 2023. Starship version 3's ship will generate more thrust than the Falcon Heavy at liftoff. (Credit: Sawyer Rosenstein for NSF)

Version 3's ship is going to be stretched by over 18 meters and will have nine engines - six vacuum-optimized Raptors as well as three sea-level versions. This version is to be capable of carrying up to 2,300 tons of propellant and is listed as being capable of generating up to 2,700 tons of thrust. To put that into perspective, the version 3 ship - just the ship - will generate 16 percent more thrust than the Falcon Heavy can generate at liftoff. 

The full Starship version 3 stack will be 150 meters tall, much taller than any rocket that has come before it. What infrastructure upgrades will be needed to accommodate this vehicle remain to be seen. As SpaceX strives to make life multiplanetary, versions of Starship with different uses are being developed and likely will have performance numbers optimized for their missions.

(Lead image: Booster 11 at the orbital launch site at Starbase with the "Gateway to Mars" sign. Credit: Sean Doherty for NSF/L2)