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SpaceX's giant rocket did much better on its second launch attempt, but it still failed [1]

['Daily Kos Staff']

Date: 2023-11-24  

On Saturday morning, SpaceX made its second attempt to launch its Super Heavy booster and Starship upper stage. While that launch went much better than the first attempt in April, it still ended with the destruction of both the booster and the upper stage, with neither reaching the goals set for this flight.

For any fan of spaceflight, it was a visceral thrill to see the enormous 394-foot-tall, 11-million-pound rocket blasting away from the launch facility in Boca Chica, Texas, and soaring upward on 33 engines with roughly twice the thrust of NASA’s legendary Saturn V moon rocket. The rocket includes several innovations and design decisions that are intended to make it not only fully reusable but also easier to build. For SpaceX and its CEO, Elon Musk, the combined rocket (which is also confusingly known as Starship) is the key to drastically reducing the cost of reaching space and eventually taking humans to Mars.

Over the last decade, SpaceX has gone from strength to strength, using a philosophy of rapid iteration and “fast failure” to go from an almost-broke also-ran to by far the most dominant company the space industry has ever seen. That philosophy appeared to be on full display Saturday morning as the second Starship attempt headed for the sky.

However, there are reasons to doubt the whole approach. And very good reasons to think that SpaceX’s attempts to revolutionize space in the long term could be a major stumbling block over the next few years, especially for NASA.

The flight

By any measure, this second flight of Starship was much, much more successful than the first.

That success doesn’t start with the rocket; it starts on the ground. On the first flight, SpaceX decided to hurry ahead with the launch even though it had not completed any kind of water deluge or trench system to reduce the level of damage done to the launch facility. The result of this horrendous decision was an infamous rock tornado that flung blocks of shattered concrete in all directions, left a gaping hole below the launch platform, and left the tanks that supply methane and oxygen to the rocket dented by impacts.

In the seven months since then, SpaceX has remediated much of that damage and installed a system that sprays a fountain of water up just as the engines come to life. The result reduces damage on the ground as well as reducing the roar and vibration of the rocket throttling up to liftoff.

Unfortunately, that period also corresponded to an increase in injuries and safety incidents at a company already notorious for lax attitudes toward worker safety. Reuters reports that since 2014, SpaceX has reportedly generated “at least 600 previously unreported injuries” including “crushed limbs, amputations, electrocutions, head and eye wounds and one death.”

The ability to watch the activities at SpaceX’s “Starbase” in Texas has given an unprecedented insight into both base operations and the construction of the Starship rockets. Thousands of space enthusiasts tune in each day just to watch the components of the ships being welded together and undergo routine tests. However, as someone who worked in heavy industry for decades, I frequently see workers positioned under suspended loads (for example, beneath engines, components, or entire rockets hanging from cables) or working at high altitudes without being connected to safety devices—either of which would have been immediate grounds for dismissal on any site where I was employed.

In the flight itself, Starship 2.0 (technically made up of Super Heavy booster prototype 9 and Starship upper stage prototype 25) came off the pad much more quickly than in the previous flight, with all 33 Raptor 2 engines burning. All engines were still burning two minutes and 29 seconds later when the booster throttled down in advance of stage separation.

Moments later, the six engines on the upper stage burst into life, and the Starship headed for space. Until that point, everything was, in spaceflight terminology, “nominal.” That is, all according to plan.

Super Heavy drops away as Starship heads for space.

But at around the three-minute mark, it was clear something was wrong with the booster. Efforts to reorient the massive Super Heavy seemed to be going poorly, and signs that one or more engines were damaged were clearly visible.

Venting from thrust section of Super Heavy indicates problems.

One of the engines that was supposed to restart in this effort never did, and over the next few seconds, a cascade of other engines winked out. There were several smaller blasts and venting of gas before the entire booster exploded at 3:20 after the launch.

Super Heavy booster explodes.

Even with the booster gone, Starship continued its flight. The plan was for it to enter a suborbital path at an altitude of around 93 miles and a velocity of about 17,500 miles per hour. Just before seven minutes into the flight, the call from the announcers was still that the status of Starship was nominal and everything was on path for the desired suborbital flight. However, visibility of Starship was becoming more difficult as it neared the 150-kilometer target altitude and moved further downrange.

Starship with everything apparently nominal 6:40 into flight.

At this point, with everything going well, the onscreen telemetry showed Starship’s speed at 15,428 kilometers per hour, with just over a third of oxygen and methane remaining. If the display is accurate, it’s also possible to see that there was slightly more oxygen than methane.

Flight telemetry at 6:40.

A few seconds after 7:00, a bright flare from the Starship indicated venting from the thrust section. All engines continued to burn, but several more bright plumes and flares were visible, especially at around 7:40. At this point, telemetry shows oxygen and methane levels to be about even.

Plumes visible around Starship at 7:40.

Finally, with Starship well down range and barely visible, there was another puff of gas or flames around 8:05 followed at 8:07 by a final burst, which seemed to be the definitive loss of the Starship.

Final loss of Starship between 8:05 and 8:07 into flight.

At this point, all further telemetry is lost. However, the final readings from Starship show that in the final minute, oxygen was consumed at a higher rate than methane. They also show (again, assuming the graphic is accurate) that only around 4% of oxygen remained.

Final telemetry for Starship

The good, the bad, and the ugly

On the good side of the sheet:

There seemed to be relatively little damage at ground level, showing that SpaceX’s changes to the launch facility were largely successful.

All 33 Raptor 2 engines not only ignited but burned through the entire flight of the Super Heavy booster. That goes a long way to resolving concerns about the reliability of this engine and shows a significant improvement over the previous flight.

The ambitious “hot staging,” in which the two parts of the rocket separated without completely shutting down the booster, appeared to go well, though it may have generated damage contributing to the failure of Super Heavy.

On the bad side:

Neither Super Heavy nor Starship completed the flight as specified.

The cause of failure for either portion of the rocket was not immediately obvious.

The first of those items on the bad side isn’t all that unexpected. This was still a prototype, and SpaceX’s whole philosophy of rapid iteration means that they are more willing to accept failure than spend months or years working problems through simulators and addressing potential issues.

However, the second bullet point on the bad side is significant, and it plays directly into SpaceX's core philosophy.

There are many industries and situations where rapid iteration is a tremendously effective approach. Nothing beats exposing systems to real-world conditions to turn up issues that were missed in planning and simulations. Any software engineer who has moved from older systems designed to test until perfect, to those that involve rapid prototyping and iterating on failure is unlikely to go back.

Here’s why it may not be the best way to handle things in this case:

First, each flight of Starship that ends in failure generates an incident report with the FAA and a requisite investigation. While SpaceX will essentially carry out that investigation itself, the FAA will need to approve the findings and determine whether any changes made to address problems are sufficient to authorize the next flight. For airplanes, these investigations can take years. That won’t be the case here because Starship is, at this point, carrying no passengers and SpaceX is not actively trying to approve the rocket for human flight. However, the investigation will take months, and there may be significant delays in negotiating the requirements. That’s not exactly the kind of system that lends itself to try, fail, repeat.

Second, SpaceX has tried to maximize the possibilities of rapid interaction at Starbase by building multiple rockets even before the first one had flown. But look again at the second bullet point in the “bad” list. SpaceX hasn’t yet announced why this flight failed. After the first flight, SpaceX bragged that it made over 1,000 changes before the second launch. Something like that could happen again before the next Super Heavy and Starship are trundled to the pad.

But it could be worse. Looking at how the booster failed, it’s clear that while the initial failure started around the engines, the final destructive failure happened about halfway down the length of Super Heavy. In the best-case scenario, that could be because systems inside the rocket detected that things were so off-course that it was time to trigger the “flight termination system” (i.e., the built-in self-destruct, which was notably one of the things that did not work as intended on the first flight). However, the point of explosion is also very close to the “common dome,” a shared bulkhead that separates the rocket’s methane and oxygen tanks. It’s possible that the failure resulted from fluid hammer or similar effect rupturing this dome shortly after stage separation. In the launch video, there are no obvious leaks or damage on the top of the rocket—the end that was exposed to the direct blast from hot staging—but the clear issues in the thrust section and the burst near the common dome could both be from the effects of pressure waves or rapidly shifting fuel moving around the rocket after the abrupt change in velocity seen at hot staging.

If Super Heavy failed because the engines were damaged by the forces generated at stage separation and the ultimate destruction came because the flight termination system was activated when computers determined it was in an unrecoverable state, it’s possible this could be addressed by changing the throttle levels of the engines on Super Heavy and Starship at staging. Few structural changes may be required. On the other hand, if it was the common bulkhead that failed, it could send every Super Heavy prototype now sitting at Starbase to the scrapyard and require a fundamental change in the booster’s internal structure.

What happened to the Starship is more mysterious, as it’s little more than a dot in the televised image when it explodes. Also, Starship was at altitude and only about 10% short of its final velocity when it blew. That seems puzzling.

However, the plume that appears at around 7:00 into the flight just as the oxygen gauge begins to drop more quickly could be a clue. This could indicate a leak developed (likely around one of the engines, not in the fuel tank), allowing excess oxygen to vent from Starship.

If that’s the case, the flight termination system on Starship may have been activated simply because it ran out of fuel too soon and the flight computer determined that it couldn’t reach the target course. That’s a best-case scenario. A bad one is that determining the cause of failure could take weeks or months.

Now what

There’s a general impression when I do these post-mortems that I hate Musk, hate SpaceX, and am pulling for the failure of Starship.

The first part of that is true enough: Musk is a misogynistic, racist, antisemitic, anti-trans, conspiracy theory-spreading asshole who daily demonstrates that he’s a giant threat to democracy. There is no greater threat to the future of SpaceX (and Tesla and every other company in which he is involved) than Elon Musk.

But I’m pulling for Starship. I want it to work. I want that low-cost access to space. I want all the possibilities that it brings. Yes, I’m terrified by the thought of how much control that gives Musk over space access, but not so terrified that I want to turn back the clock.

However, there’s one thing I do want to point out: Last year, NASA launched the first flight of the new Space Launch System. It isn’t quite as large as Starship. It’s only about half as powerful, and it lacks the innovations that allow reuse of the rocket. But SLS worked the first time, sending an Orion capsule on a deliberately long path around the moon before returning to splash down on Earth.

It was late, it cost billions of dollars, but it was also functional. Right now, NASA is prepping Artemis II for a flight that will take four astronauts around the moon. This will include the first woman astronaut and the first Black astronaut to ever fly beyond low Earth orbit. It’s scheduled to fly about a year from now, in November 2024.

A year after that, NASA wants to launch Artemis III. That’s the mission that will actually put human beings back on the moon, with two astronauts landing near the lunar south pole. But there’s a problem with that flight, and the problem is … Starship.

The landing system on Artemis III was contracted out to SpaceX and it’s based on a variant of Starship. However, before that “human landing system” can be there, SpaceX is going to need many successful flights of Starship. As in a dozen or more. It’s very hard to see how that could happen given the current status of Starship and the investigation that must happen before they can make another attempt at the simplest, suborbital flight.

SpaceX made tremendous progress between Starship 1.0 and Starship 2.0, even if both ended in the same way. There’s no doubt the investigation following this second flight will be shorter, and it’s unlikely to be seven months before a rocket is on the pad for a third attempt. Musk is even predicting they could fly again by Christmas. I wouldn’t bet on that.

Right now, it’s starting to look like plodding old NASA will be ready to go to the moon, and waiting on those speedy guys at SpaceX.

(Author’s note: Back in that last post-mortem, I predicted that the damage to Starbase would delay the second launch until after the end of the year. I was wrong about that. I can only plead that my predicted launch date was better than Musk’s.)

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