The world's largest rocket was destroyed without completing the mission; telemetry data will be used for improvement
On Thursday, April 20, 2023 at 08:33 CST (13:33 GMT), SpaceX conducted its first orbital launch of the Starship system (S24 spacecraft) and Super Heavy "booster" (B7 rocket). The 119-meter, 4,997-ton rocket successfully lifted off from the Launch Pad, ascended, went supersonic, and crossed the Max Q zone - the point of maximum dynamic pressure - but was destroyed just over four minutes after launch. Starship 24 was the first orbital prototype, and the B7 booster was the first to be equipped with 33 Raptor engines, according to the project. This test flight was not intended to reach orbit but instead sent the spacecraft on a long suborbital trajectory, crashing near Hawaii 90 minutes after liftoff. The Starship and the Super Heavy, which crashed in the Gulf of Mexico off Boca Chica, could not be recovered. SpaceX has several other Starship and Super Heavy vehicles in various stages of production, and they have already incorporated some design changes. "Learned a lot for the next test in a few months," SpaceX President and Chief Executive Elon Musk tweeted shortly after the flight. SpaceX is analyzing the telemetry and will make a test report to be delivered to NASA, as the American space agency intends to use the Starship spacecraft to land astronauts on the Moon.
It's true that SpaceX downplayed the failure of the flight's formal objectives, such as the first stage flight phase, spacecraft separation (staging), vacuum ignition of S24's engines, its fractional orbit, and subsequent crash into the Pacific ocean. However, it should be noted that the Starship did achieve a significant milestone by climbing to a 39km apogee over the Gulf of Mexico, which was the highest of any Starship to date. During the flight test, the vehicle did experience several engine shutdowns, lost altitude, and began to roll over. The flight termination system (FTS) was commanded both on the booster and on the ship, resulting in the destruction of the spacecraft.
It is true that a few days before the test, CEO Elon Musk expressed contentment if the rocket only did not destroy the firing table and the integration and capture tower. This may have been due to warnings from engineers that the chances of success were low. However, relative to the planned schedule, the flight can be considered a failure, even though the telemetry data is crucial for the development of the project. It's important to note that failures provide opportunities to examine poorly designed or improperly executed designs and procedures, and it's through these failures that progress can be made.
Despite the failure, SpaceX employees who watched the launch at headquarters in Hawthorne, California, celebrated the progress made on the flight. The narrators faced the failure as a “spectacle”.
In a later update, SpaceX said the rocket reached an altitude of 39 kilometers before engine failures caused it to lose altitude and crash. "With a test like this, success comes from what we learn, and we learn a lot about the vehicle and ground systems today that will help us improve Starship's future flights," the company said. The media department emphasized before and immediately after the launch that this flight was a test run designed to gather data to improve the design.
“This was a developmental test … Starship's first test flight,” said Insprucker.
Takeoff “off nominal”
By the time the Starship left the turret behind, the first sign of trouble was when three of the booster's engines had already failed. This type of pre-launch failure would have terminated the launch of most rockets which are only released from the launch pad when all systems are functioning The loss of three engines while a rocket is attached to the firing table is not considered rated or safe.
The fact that the rocket was allowed to take off without all the engines running is unusual in launch practice. Since the early days of spaceflight, rockets were not allowed to fly unless all engines were running. The reason is that if the engines are not running as intended after ignition, there is a significant problem that is only likely to get worse if the vehicle takes off. If the failure is verified in the initial moments, the procedure is to let the rocket move away from the sensitive installations and allow it to fall in the desert or in the ocean – if a catastrophic explosion does not happen before.
The failure of guidance and control to detect that the rocket was off in its normal climb path, that it was making a turn during and to terminate the state in which, for one full 19 seconds, the rocket performed three somersaults is another issue that will have to be analysed. Such a delay in the self-destruct system could have catastrophic consequences. For example, the location of Port Isabel is only 8 km away from the Starbase, a distance that could be covered by a Starship in a fraction of the time it took the FTS to finally activate. An even more severe aspect to plans for a future manned flight is the lack of Starship's emergency system to abort when the rocket malfunctions during ascent or when it strays from its nominal trajectory.
Data displayed on the webcast showed that at T+15 seconds, three motors, two in the fixed outer ring and one in the center section, which are capable of tilting, were not working. A third engine on the outer ring stalled at T+40 seconds, followed by others 20 seconds later. At the T+100 second mark, six engines were not running, although one restarted a few seconds later and others failed. According to the chronology offered by the company, the engines on the Super Heavy were supposed to shut down at T+02:49, followed by the Starship separating and firing its six Raptor engines. Instead, the pile began to fall as the engines continued to run. "This doesn't appear to be a nominal situation," SpaceX's John Insprucker said on the webcast, stating the obvious 'As per standard procedure'.
The unfolding of the Starship test flight
When the engines fired a few seconds before takeoff, three of them discharged unburned fluid – which may have happened because they were shut down due to failed last-second checks. As the rocket left the pad, the plume's color appeared somewhat enriched (green with flashes of orange) and there was at least one burst a few seconds into flight with a plume of smoke indicating a more destructive breakdown.
Operation continued relatively 'nominal' for the next 25 seconds, when something unexpected seemed to happen in the first stage engine bay: at T+ 00:29, and within approximately two seconds, an explosion occurred at the base of the ''booster''. There was speculation that it was an exploding hydraulic power unit (HPU), which was confirmed. It also looked like some of the aerodynamic fairing on the tanks and pipelines had been ripped off by the judder of the event. Within a minute of takeoff, another three engines failed, for a total of six out of commission. What was not known at this time was whether the additional failures of the Raptor engines were due to possible problems with their pumps, controllers, valves and pipelines - or they were damaged by debris from the damage the firing table suffered on takeoff.
During the flight, the Speed and altitude barely increased after Max Q at T+ 01:20, while the rocket went into supersonic flight at about T+01:31, and within two minutes acceleration was almost non-existent with speed decreasing by about 2,157 km/h. and then decrease from there until LOX exhaustion. The rocket loses momentum and performance drops at the 02:25 minute mark.
The engine controller tried to keep the flight attitude stable even with asymmetric thrust, but the situation got worse beyond the system's capacity: the simple tipping of the Raptors' nozzles did not compensate for the rotation. According to SpaceX's telemetry graphs on the youtube screen, the speed was above 2000 km/h and then started to fluctuate up and down as vehicle control began to degrade.
At T+02:40, moments before the so-called “main engine cut-off” (BECO, booster engine cut-off), the Super Heavy began its arc to orient itself towards the ship's separation. However, that arc continued in a "loop". The booster's guidance and control (GN&C) system did not seem to interpret the situation as a failure in the guidance algorithm. The ''booster'' completed more than three turns over the course of one minute and 19 seconds, after which the flight termination system (FTS) was triggered at 03:59. There was imaging evidence that the Starship was partially detached from the Super Heavy, but this was likely due to the effects of the somersaults during the last 1 minute and 19 seconds of the flight. At the end of the flight there was almost no LOX in the tank, but a considerable amount of CH4. At T+04:00, the vehicle broke apart when the automatic control circuit activated the flight termination systems (self-destruct).
Flight summary
The rocket managed to take off with thirty of the 33 engines available (it is estimated that with up to 91% thrust).
As the traction forces were lower than expected, the exposure time of the firing table to the engine exhaust and acoustic loads increased; The shutdown of the engines was not accompanied by explosions and did not lead to the destruction of the rocket; Debris lifted from the floor and deck structure damaged the engines and caused fluid leaks. The sound barrier and the Max Q zone were successfully passed; The total number of engines out of action increased to five, with obvious problems: asymmetrical thrust resulting from the failure of engines in the outer ring; more engines went out, reaching eight; the thrust vector control was compromised due to the failure of at least one engine (telemetry open to the public did not show data such as the thrust curve of the engines, so it was not possible to know if the performance of all was nominal). For the same reason, it was impossible to know whether the initial turn was due to uncorrected asymmetrical thrust or to triggering the somersault procedure foreseen in the separation of the 2nd stage, with the consequent stress preventing the separation; the control system kept the rocket for the next 1 minute and 33 seconds of flight (till T+03:59), despite the asymmetry of the failed engines; during the uncontrolled fall, the rocket did not break due to dynamic stress – the structure resisted the tensions both in the nominal flight and at the moment when the uncontrolled rotations in the three axis began and eventually breaking at 29 km, when the self-destruction system worked. The attitude control system functioned both in authority over the behavior of the pile on normal rise as well as during failures of faulty engines. The flight was aborted at T+234 seconds, taking into account that the ascent route was between Cuba and Florida, and a fall in either of these regions would be extremely undesirable.
The problem with the Launch platform
For some reason, neither officially nor explained in detail, the annular firing table was not equipped with a channeling and jet deflection system to disperse the flow of hot gases at high speed, high temperature that came out of the nozzles, causing not only thermal stress such as sonic and vibrational. The explanations were that there was enough distance between the table and its base, a hexagonal block of Fondag RS concrete armed supporting six cylindrical columns of steel and concrete, anchored in the sandy soil of Boca Chica; others said that the heat from the buoyancy would be short-lived, as the rocket would leave the table in good time. In particular, the Fondag RS is capable of withstanding temperatures of up to 1,100°C. This feature would supposedly allow SpaceX not to have to replace the concrete lining under the platform after each static test, as the material would withstand the stresses caused by the thrust of the Raptor 2 engines.
The impact was not only ballistic, but also high-speed trajectories that destroyed cars parked more than 200 meters away. After the dust settled, there appeared to be chunks of concrete strewn all over the area.
Images from the base show intense underground digging that resulted in large rocks and debris being thrown for ten seconds to get high enough. Tank farm tanks were also hit by debris.
For the last three years, there have been concerns expressed that the Starship launch pad lacks any of the systems used by NASA and others to lower the energy of a launch, such as a flame trench, flame deflector and water sprinkler system. The lack of these energy absorption systems appears to have severely affected the launch pad. After the flight, it became evident that erosion in the platform area was extensive. A crater several meters deep has been excavated almost the width of the stand. The concrete panels around the platform had been torn off or shattered. There was extensive damage to Starbase launch facilities, including a liquid oxygen tank that was heavily dented. Debris and pieces of concrete were ejected up to several hundred meters from the platform.
Musk had long advised that the absence of a flame trench or a deflector was “possibly a bad choice”, and indeed a set of '''booster''' parts and armor was already in production and mount on Starbase – it just wasn't installed.
The Failure to adequately absorb and dampen energy around the platform, causing destruction of the underlying concrete, ejection of that concrete and underlying soil, resulting in a large crater being excavated under the platform will require a lot of infrastructure work before the next flight. Part of this work may, and probably will, require additional input from the US government – in the form of environmental permits and oversight from agencies interested in the structural and mechanical segment (NASA, FA etc).
Debris allegedly found over the shores of South Texas
Hours after the flight ended, possible debris from the rocket began to appear on the shores around the launch facility in Boca Chica. Local county officials were quick to order the temporary closure of roads and beaches to help with "anomaly cleanup efforts", but as the vehicle was well over the Gulf of Mexico and reached an altitude of approximately 40 kilometers the precautions extended. just a relatively small area where fragments could end up.
"Look what I found!" at 6:30 pm CDT (2300 GMT), about nine hours after launch, in social media people captioning photos of themself holding what appeared to be about half of one of the 18,000 hexagonal heat shield blocks. "I'm not sure but I suspect more will come ashore in the coming days," wrote Joe Tegtmeyer, who describes himself as "interested in all things space related, SpaceX."
Tegtmeyer wasn't the only person to find a possible piece of the craft: Photos shared on social media showed that at least one other person had found a smaller shard of black and white pottery. For its part, SpaceX issued a warning to the public, warning against attempting to handle or retrieve the debris directly. Instead, the company invited findings to be reported on its hotline or through email.
Although the test flight was a privately funded activity, it was conducted under a launch license from the Federal Aviation Administration, and performed with US government oversight. As part of the Outer Space Treaty of 1967, protections are extended so that any spacecraft components found anywhere on Earth (or in space) remain the property of the launch operator until such time as the entity explicitly relinquishes them. As such, all Starship debris remains the property of SpaceX, even if found on private property or in the Gulf of Mexico.
Features of the Superheavy Booster stage
Musk noted that the Super Heavy's dry mass should stay below 200 tonnes, although that's a tough target. The engines, including the mass of their supports, are 2 tons; fuel and liquid oxygen tanks weigh approximately 80 tons; and the interstage is about 20 tons, including the four grid fins that weigh approximately 3 tons each. Musk noted that he hopes to be able to cut the mass of each grid fin in half and that the current design is very inefficient. He also noted that currently everything is very heavy, including avionics, fins and batteries.
The rocket is designed to carry 3,600 tons of propellant, of which approximately 78% is liquid oxygen. The Raptor engine burns at a mixture ratio of 3.5 to 3.7, which is rich in fuel. A fuel-rich mixture burns cooler than stoichiometric ratio, which would melt the engine. The Super Heavy's excess propellant(the amount of fuel that cannot be used without risking damage to the vehicle) is on the order of 20 tons, which is significantly higher than the Falcon 9's excess fuel of one-ton. noted that the final dry mass of the Super Heavy should be between 160 and 200 tons.
The grid fins on the Super Heavy do not bend like the Falcon 9, as the Falcon 9 has another mechanism that adds unnecessary complexity, mass and failure modes. Furthermore, the increase in drag from the extended fins during climb is small, assuming they are not at a high angle of attack. The fins are not evenly spaced 90° apart like on the Falcon 9. Musk said the reason for this change is that the Super Heavy requires more heading control authority, so they positioned the grid fins closer together to increase that control. The grid fins are currently electrically powered, using a modified Tesla Model 3 motor to drive them. In continuation of using Tesla parts, batteries are currently optimized for power rather than energy, as a car needs several hours of power, while grill fins only need two or three minutes. For these reasons, Musk noted, like much of Starship's design, batteries are temporary and battery mass can drop by a factor of roughly ten.
SpaceX had long ago decided to remove the Super Heavy's hot gas engines. To replace them, it uses the gas coming out of the tanks for attitude control, having four vents spaced at 90°. By venting the tanks through these openings, they can control the booster's attitude during rotation. This has the advantage of using the flash gas, which would need to be vented anyway, to do useful work.
Raptor 2 engine
Compared to older versions, the Raptor 2 features a larger nozzle, which lowers the area ratio; this causes a decrease in specific impulse of about 3 seconds, but increases the impulse significantly. Despite having a lower ISP, this allows '''booster''' motors to be more efficient, as it reduces gravity losses. Musk noted that the Raptor 2 will be significantly cleaner looking than the Raptor 1 as it will remove a large amount of plumbing. The Raptor Vacuum has a brazed steel tube wall nozzle extension that has an expansion ratio of around 80, giving the engine a specific impulse (ISP) of 378 seconds. Musk noted that teams hope to get the expansion rate up to 90, which would increase the ISP to 380 seconds. In the long term, SpaceX will have three variants of the Raptor: sea level engine with gimbal, sea level engine without gimbal, and vacuum level engine without gimbal.
Starship Orbiter
Starship's Thermal Protection System (TPS) has tiles mechanically mounted so they can move slightly, ensuring they are not damaged during expansion and contraction during supply and re-entry temperature changes. Currently, Starship tiles are manufactured in Florida, in the “oven”. While not all tiles are uniform, SpaceX is able to mass-produce them due to the fact that they are largely the same shape and size, a significant advantage over the space shuttle system. Furthermore, Musk described the tiles as having "no significant limit" to their lifespan, and stated that the most difficult parts of the vehicle to protect against re-entry heating would be the canard hinges. Ensuring that hot plasma does not enter these hinges and destroy the vehicle is essential as the seal must simultaneously not damage the tiles and survive the heat of re-entry; this means that a metal seal is required. With a full heat shield, Starship's dry mass is "expected not to exceed 130 tonnes". Musk added that adding a ton to the spacecraft removes about two tons of payload capacity, after taking into account the added mass and the increase in propellant required.
Staging Sequence
Just before the main engine shutdown, the Super Heavy would have to tilt its engines, causing the vehicle to start spinning (the “flip”). The locks between the Starship and the Super Heavy would then come loose, causing the vehicles to pull away; the whole process is similar to how SpaceX ejects its Starlink satellites. This serves dual purposes, as it separates the stages when starting the booster spin, which it needs to drive for boostback ignition.
Musk wanted Starship to have no active separation mechanism as he decided that was totally superfluous; and that the same effect could more or less be replicated using existing systems in Super Heavy. By using the booster's tilting motors to give the rocket a small but significant spin moments before separation, the Super Heavy could pull away from the Starship and let the components drift apart thanks to centripetal forces. Since Starship is five times heavier than Super Heavy at separation, the ship would float away from the rocket in a straight and steady line, and the use cold gas propellants to orient itself, and fire its six engines to launch into orbit. In exchange for the slightly unorthodox ejection profile, if this new approach works, SpaceX could entirely dispense with developing a piston and spring system capable of pushing a craft weighing approximately 1,300 tons away from the Super Heavy. This approach is possible on Starship in large part because the ship's six engines are concealed within the aft skirt, meaning there is no chance of the nozzles being damaged by impact on the booster interstage.
SpaceX has already changed the Raptor design several times and should continue to work to make these engines more reliable, both on ignition and throughout the flight, given that SpaceX has extensive data on the in-flight performance of the liquid oxygen supply system (LOX ) and liquid methane. SpaceX could rapidly manufacture these engines at a rate of nearly one a day.
Defects will impact US lunar program
NASA, in particular, now has to deal with difficult situations arising from the choice of Starship as its only official landing module for the Artemis III mission. There is little doubt that the lunar module is already behind schedule, will now be significantly delayed. The lunar landing test flight of a simplified prototype of the craft is unlikely to take place in 2024 as planned. There were never plans to test the Starship module with a crew in Earth orbit, as NASA did with its Lunar Module on the Apollo 9 mission, or in orbit of the Moon, as on Apollo 10. 2024, the next SpaceX lunar module flight would take place on Artemis III, already with a crew will be launched on SLS - Orion spacecraft.
Whether this failed test flight will force a delay in the launch of Artemis III depends on whether Artemis itself is already so far behind schedule that a delay on the Starship would not make a difference. NASA doesn't have a viable near-term alternative to SpaceX's lunar module. For the first time in the history of American spaceflight in the space program's goals, a crucial mission like Artemis III is tied to the progress of a single space enterprise over which NASA has little or no control. Previously, as in the days of Apollo, the government agency directly supervised the contractors, who acted under its direct command.
Another aspect is that the Starship in the lunar module version does not have the ability to abort the descent. This means that if any essential procedure goes wrong in the lander during the descent to the surface, the crew will face multiple problems. This means an unprecedented risk that the American space agency, by taking the Artemis III crew to the lunar soil.
Another sore point is the engine: the Raptor 2 has never made it into space yet. The Raptor is all-new and relies on cutting-edge emerging technology. Metalox engines are a very recent practical development, allied to the full-flow staged combustion cycle turbopump system, a well-established technology but complex to use.
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In recent news, there has been discussion of the SpaceX Starship prototype, which experienced several technical difficulties during a test launch. The information in this article is based on a transcript of Twitter spaces hosted by Elon Musk, posted by a user who claims to have listened to the launch recording. While there may be some inaccuracies in the transcript, we will try to correct any obvious errors as necessary.
One issue with the Starship prototype was that the FTS system (flight termination system) took too long to activate. This is a concern that needs to be investigated further. Additionally, three of the rocket's engines were shut down at liftoff due to underperformance, not debris impact.
At T+27, an "explosion" occurred which caused damage to the heat shields for engines 17, 18, 19, and 20. Some debris resulting from this event can be seen in videos of the launch. Furthermore, visible fires could be seen intermittently from the aft end of the rocket for the rest of the flight. At T+62, additional heat shield damage was observed near engine 30, although the engine continued to function.
At T+85, the thrust vector control was lost. The vehicle was close to staging, but underperformance and loss of thrust vectoring prevented it from reaching that point. It is important to note that the spin was not part of an attempted staging procedure.
In hindsight, it would have been possible to compensate for the losses by throttling up the remaining engines. During the test, the engines were not running at full throttle. However, since so many engines were out, it was likely necessary to throttle up the remaining engines to achieve staging. There is currently no direct evidence that debris damaged the vehicle, but this possibility has not been ruled out.
Looking ahead, the next booster should be more durable in terms of engines to reduce the likelihood of a single engine failure impacting others. Furthermore, an electric thrust vectoring system will be less vulnerable. One possible explanation for the concrete failure during the launch is that the thrust of the rocket compacted the sand under the pad, causing the concrete to distort and crack apart.
During the launch, the lateral movement of the vehicle was due to three engines being shut down. The Starship prototype did not attempt to "save itself" after FTS activation.
For the next launch, the goal is to get off the pad much faster. It is projected that the cost of Starship development for this year will be around 2 billion dollars. Finally, it is worth noting that Raptor production has been temporarily slowed down as they are stockpiling.
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