SpaceX Flies IFT-4, Achieves Super Heavy, Starship Controlled Splashdowns

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SpaceX Flies IFT-4, Achieves Super Heavy, Starship Controlled Splashdowns


SpaceX’s fourth fully integrated Starship/Super Heavy stack roars out of Boca Chica, Texas, on Thursday morning. Photo Credit: SpaceX

SpaceX dramatically launched its fourth Integrated Flight Test (IFT-4) of a fully stacked Starship/Super Heavy combo out of Starbase in Boca Chica, Texas, on Thursday. The 394-foot-tall (120-meter) behemoth—the mightiest rocket ever flown, twice as powerful as NASA’s long-retired Saturn V and current Space Launch System (SLS)—took to the South Texas skies at 7:50 a.m. CDT and ticked off a set of important milestones for the program, including the first controlled splashdown of a Super Heavy booster and the first successful re-entry and controlled splashdown of the Starship.

With 16.7 million pounds (7.5 million kilograms) of thrust, the Super Heavy’s liftoff thrust is higher than any other launch vehicle. Photo Credit: SpaceX

It has already been an impressive week for SpaceX, which last Saturday evening and late Tuesday flew a pair of Falcon 9 boosters—laden with dozens of Starlink low-orbiting internet communications satellites—out of storied Space Launch Complex (SLC)-40 at Florida’s Cape Canaveral Space Force Station. They saw the Hawthorne, Calif.-headquartered organization wrap up May as its first month with as many as 13 and 14 launches and June dawned with the shortest-ever turnaround of Falcon 9 payload fairing halves.

IFT-4, the fourth outing of a fully integrated Starship/Super Heavy stack, would layer extra icing onto the cake. Powering aloft under 16.7 million pounds (7.5 million kilograms) of thrust from the 33 Raptor engines at the Super Heavy’s base, SpaceX is adding incremental goals to each test flight as it strives to progressively mature the program.

All but one of Booster 11’s 33 Raptor engines performed nominally during first-stage ascent. Photo Credit: SpaceX

Starship’s maiden flight on 20 April of last year saw the stack attain the greatest liftoff thrust of any booster in history. It greatly surpassed the 7.5 million pounds (3.4 million kilograms) of the long-retired Saturn V, 8.8 million pounds (3.9 million kilograms) of the SLS during November 2022’s Artemis I launch and even the Soviet Union’s N-1 rocket, which reportedly produced 10.2 million pounds (4.6 million kilograms) during its four failed flight attempts between February 1969 and November 1972.  

But although IFT-1 cleared the Boca Chica launch pad and attained altitude, it suffered a multitude of technical maladies and the premature shutdown of several Raptor engines, which led to an untimely—though visually spectacular—demise. Last 18 November’s IFT-2 launch saw all 33 Raptors burn successfully through Main Engine Cutoff (MECO), followed by a “hot-staging” exercise as the 233-foot-tall (71-meter) Super Heavy was jettisoned and performed a flip maneuver plus an (almost) nominal burn profile of the six Raptor engines aboard the 164-foot-tall (50-meter) Starship itself.

IFT-2 powers uphill on 18 November 2023. Photo Credit: Mike Killian/AmericaSpace

But as the IFT-2 stack headed out over the Gulf of Mexico, the Autonomous Flight Safety System (AFSS) issued a destruct command to destroy the vehicle. This led to a raft of corrective actions, including the implementation of an all-electric Thrust Vector Control (TVC) system and improvements to pre-launch propellant loading protocols.

Last 14 March’s IFT-3 completed a full-duration Raptor burn for both stages and the Starship successfully trialed in-space propellant transfer and the actuation of its payload bay (or “pez”) doors. However, a planned relight of the Starship’s Raptors did not occur and the vehicle re-entered the atmosphere for a “hard” splashdown but was lost before impacting the waters of the Indian Ocean. The Super Heavy’s attempted “boost-back” and “landing” burns were also troubled and the giant booster was lost at an altitude of 1,500 feet (460 meters) above the Indian Ocean.

IFT-3 in March successfully completed full-duration Raptor engine burns for both the Super Heavy and the Starship. Photo Credit: Mike Killian/AmericaSpace

Preparations for IFT-4 got underway last month, with a static fire test of the six Raptors on the Starship—designated “Ship 29”—and a rollout to the pad at Starbase on 11 May for an all-up launch day dress rehearsal on the 20th. SpaceX initially aimed for an opening launch attempt as soon as 5 June, “pending regulatory approval”, a date which subsequently moved 24 hours to the right, with an expansive two-hour “test window” that extended from 7:00 a.m. CDT through 9:00 a.m. CDT.

Last week, the entire stack—with Ship 29 mounted atop the Super Heavy, designated “Booster 11”—was loaded with ten million pounds (4.5 million kilograms) of liquid oxygen and liquid methane propellants for a final test ahead of IFT-4. And early Thursday morning, teams at Starbase received a “Go” for fueling at 6:45 a.m. CDT, by which time a new T-0 of 7:50 a.m. CDT was targeted. Weather conditions stood at 95-percent favorable and fueling of the Starship and the Super Heavy commenced shortly after 7 a.m. CDT.

With all but one of the 33 Raptor engines on the Super Heavy burning, IFT-4 makes its way towards orbit. Photo Credit: SpaceX

“The fourth flight test turns our focus from achieving orbit to demonstrate the ability to return and reuse Starship and Super Heavy,” SpaceX explained. “The primary objectives will be executing a landing burn and soft splashdown in the Gulf of Mexico with the Super Heavy and achieving a controlled entry of Starship.

“To accomplish this, several software and hardware upgrades have been made to increase overall reliability,” it was added. “The SpaceX team will also implement operational changes, including the jettison of the Super Heavy’s hot-stage following “boost-back” to reduce booster mass for the final phase of flight.” Notably, the Starship was also intentionally outfitted with one “thin” heat shield tile and two others were removed entirely to measure the effects of increased re-entry heating across Ship 29’s airframe.

After separation at 2.5 minutes into flight, Booster 11 continues its long descent back towards the Gulf of Mexico. It successfully splashed down less than a minute after this image was taken. Photo Credit: SpaceX

Beginning at T-4 seconds, IFT-4’s ignition regime got underway as the Super Heavy’s Raptors came alive in distinct “banks”, ramped up to maximum thrust and powered away from Boca Chica. The stack blazed through peak aerodynamic turbulence—colloquially known as “Max Q”—a minute into the flight and with all but one of its 33 Raptors burning the Super Heavy shut down on time a little past 2.5 minutes after liftoff.

This time, the giant booster completed a satisfactory boost-back burn to commence its return to the Gulf of Mexico and a landing burn which allowed it to execute the program’s controlled splashdown at 7.5 minutes after launch. It marked the first successful water landing of a Super Heavy.

Beautiful view of the Starship in space during today’s half-hour coast phase, prior to re-entry. Photo Credit: SpaceX

Meanwhile, Ship 29’s Raptors shut down precisely on time at 8.5 minutes into the flight and the spacecraft coasted for more than a half-hour. Re-entry got underway 49 minutes after launch, with spectacular views transmitted via Starlink as the Starship’s flight surfaces glowed a kaleidoscope of color and temperatures across its skin of 18,000 hexagonal thermal protection tiles climbed to 1,400 degrees Celsius (2,500 degrees Fahrenheit).

And despite damage incurred by a hypersonic grid-fin and a cracked camera lens, Ship 29 survived re-entry, completed its landing burn and executed a controlled splashdown in the Indian Ocean. Today’s success, like March’s IFT-3, allows SpaceX to once again confidently tick off a fully successful launch and ascent profile and for the first time add a successful controlled re-entry and landing for both Ship 29 and Booster 11.

Spectacular view, acquired via Starlink connectivity, of Ship 29’s fiery re-entry through the high plasma regime. Photo Credit: SpaceX

Next up, IFT-5 later this summer—and perhaps as soon as late June—may attempt the program’s first “Tower Catch” of the Super Heavy. Recovering the booster via mechanized arms (dubbed “Mechazilla”) on the Starbase launch tower, rather than touching down via landing legs as does the Falcon 9, favorably serves to reduce mass and part counts.

And it certainly seems that Elon Musk is in favor of a Tower Catch on IFT-5. “I think,” tweeted Mr. Musk in the minutes after today’s success, “we should try to catch the booster with the “mechazilla” arms next flight.”

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