\n<\/p>\n
\u201cKaboom\u201d is not the sound you want a rocket ship to make, as a rule. Yet that\u2019s the problem facing the private aerospace company SpaceX and its leader, Elon Musk. Instead of going to space, their newest rocket ship keeps going kaboom.<\/p>\n
The last three flights of Starship, a two-stage, 400-foot tall behemoth, ended in fiery disaster\u2014what Musk has sometimes jokingly called a \u201crapid unplanned disassembly.\u201d In January and again in March the launch vehicle\u2019s Super Heavy booster stage made it back to a massive, pincer-equipped gantry, but Starship\u2019s upper stage didn\u2019t. In May the booster exploded just before splashdown, and Starship broke up spectacularly in the atmosphere, raining debris that commercial aircraft had to dodge. As a bonus, in June the upper stage detonated on the launchpad while Starship was getting fueled for a test firing of its engines. The tally for 2025 thus far is: explosions, four; SpaceX, zero.<\/p>\n
Today Starship\u2019s Super Heavy booster and upper stage are on the launchpad yet again. The 10th test flight is scheduled for liftoff on Sunday, circa 7:30 P.M. EDT, from SpaceX\u2019s Starbase launch site in South Texas. If all goes to plan, the booster will use its 33 rocket engines to push the whole shebang to the edge of space, then drop off, somersault, execute a \u201cboost-back burn\u201d and descend to a soft splashdown in the Gulf of Mexico. Meanwhile Starship\u2019s upper stage should be firing its rockets to reach orbit, where it will deploy some cargo before flying itself back down through the atmosphere to its own splashdown about an hour and 15 minutes after launch. \u201cExcitement guaranteed,\u201d a SpaceX announcement promises.<\/p>\n
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But there\u2019s excitement and there\u2019s excitement. Look, going to space is hard. It\u2019s even harder to do in the way SpaceX is attempting. \u201cIt\u2019s one of the biggest rockets ever. It\u2019s, for sure, the biggest rocket that has attempted reuse,\u201d says Jonathan McDowell, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, who tracks space launches in his spare time. \u201cDeveloping a vehicle this big and launching it repeatedly ain\u2019t easy.\u201d<\/p>\n
Starship isn\u2019t just an oligarch\u2019s folly. It\u2019s a launch system meant to revolutionize spaceflight by flying cargo and crews to orbit at a cost that\u2019s almost too cheap to meter. It\u2019s supposed to take NASA astronauts back to the moon and human settlers to Mars. And it represents the kind of gleaming, hardware-forward future that Silicon Valley\u2019s techno-optimists are always promising. Starship is the linchpin of a lot of plans and schemes.<\/p>\n
Over the past few months, SpaceX has acknowledged which pieces of the ship broke with each flight but hasn\u2019t gone into any great detail about why. The company didn\u2019t return requests for comment from Scientific American. But SpaceX\u2019s very online rocket-spotting fans\u2014and the half-dozen aerospace engineers I talked to\u2014have been willing to speculate what the problems might be. Mostly, they believe the company has some brilliant people who stand every chance of solving them. But they also wonder what will happen if SpaceX can\u2019t figure out what\u2019s wrong\u2014or, even worse, if some fundamental engineering issue means the idea of a reusable, reliable, workhorse spaceship stays confined to science fiction.<\/p>\n
A Starship Super Heavy booster returns to the launchpad during a test flight from SpaceX\u2019s Starbase facility in South Texas on January 16, 2025. The Starship upper stage exploded and was lost during the flight.<\/p>\n
Though SpaceX characterizes this differently, Starship had essentially the same types of mishap in all three of the most recent flights\u2014leaks, fires and explosions in the fuel system. On flight seven, there was a flash and then a fire in the unpressurized \u201cattic\u201d below the bottom of Starship\u2019s liquid oxygen tank. On flight eight, that happened near one of the rocket engines. On flight nine, fuel leaked into the nose cone.<\/p>\n
That fuel, and the plumbing to move it around, might be the problem. It\u2019s a mix of liquid methane and liquid oxygen\u2014a volatile cryogenic cocktail that\u2019s still, by rocket science standards, experimental. To stay liquid, methane has to be below \u2013259 degrees Fahrenheit (\u2013162 degrees Celsius), and oxygen has to be even colder\u2014below \u2013297 degrees F (\u2013183 degrees C). That means a lot of mechanical effort to keep it cold, to move it around on the ground and on the vehicle and to accommodate it as it shifts from liquid to gas and gets lit on fire. Going back and forth from supercold to hot is called thermal cycling; without careful design and maintenance, almost anything under those conditions will break.<\/p>\n
In a Muskian science-fiction future, that\u2019s all worth it. Cryogenic fuel is a pain in the asteroid, but it has more oomph per pound as go juice\u2014what engineers call \u201cspecific impulse.\u201d And fuels like methane offer the tantalizing possibility that they could be harvested \u201cin situ\u201d on another world\u2014that they could be synthesized from carbon dioxide and frozen water in Martian regolith or, say, slurped up from the roiling methane seas of Titan. That makes \u201cliving off the land\u201d in space seem feasible, even though nobody really knows how to do it yet. \u201cMethane is a new rocket propellant for space launch, so we\u2019re still learning how to do the methane plumbing. The fact that they\u2019ve had leaks, the fact that they\u2019ve had overheating, doesn\u2019t really surprise me,\u201d McDowell says. \u201cIt\u2019s a different-sized molecule, bigger than liquid hydrogen but smaller than kerosene, so it leaks differently in different circumstances. Its chemistry is different.\u201d<\/p>\n
But the cryogenic chemistry here might be less relevant than cold mathematics. Anything going to space has to carry its own fuel, but that fuel itself has mass. \u201cThat\u2019s the tyranny of the rocket equation,\u201d says Hassan Saad Ifti, an aerospace engineer at Texas A&M University, referring to the calculation that vexes every would-be space jockey. \u201cYou need to carry more to deliver what you want, but more fuel means more fuel for the fuel.\u201d<\/p>\n
That\u2019s why rockets often have stages or external boosters: when they run out of fuel, you drop those components so that the rockets will have less mass to lift. Musk\u2019s ambitious goal is for Starship to carry between 110 and 165 tons of payload to orbit\u2014five times what a NASA space shuttle could handle, by way of comparison. But to make that work, the vehicle itself\u2014the \u201cdry mass,\u201d without propellant, rocket engines and all the plumbing\u2014has to be extraordinarily light. SpaceX is aiming for a structural ratio\u2014the dry mass divided by the sum of the dry mass and the propellant\u2014of 0.05 for both stages. \u201cMost typical rocket designs, that ratio is around 0.1,\u201d says John Dec, an aerospace engineer at the Georgia Institute of Technology. In other words, Starship is on a pretty extreme weight-loss regime.<\/p>\n
Some observers and engineers speculate that diet might be the problem. After the failure on flight seven, SpaceX\u2019s official blog reported that the cause of the leaks and fire was a \u201charmonic response several times stronger than had been seen during testing, which led to increased stress on hardware in the propulsion system.\u201d That is, some of Starship\u2019s hardware shook itself apart.<\/p>\n
Dec was previously at NASA, and his specialty there was entry descent\u2014bringing space probes down to the surface of Mars. It\u2019s one of aerospace engineering\u2019s hardest challenges. For one thing, the atmosphere gets thicker as you get closer to a planet\u2019s surface. So the force of drag on a descending vehicle changes depending on both the density of the air and the speed of the vehicle; drag becomes, in the language of engineering, a dynamic load. \u201cIf dynamic loads are changing fast enough, they can cause the vehicle to start to vibrate,\u201d Dec says.<\/p>\n
Vibrate all that complicated cryogenic plumbing too much, and very bad things happen. After flight seven, SpaceX hardened fuel lines to the engines and added vents and a nitrogen-gas purge system to the attic where the leaks happened to deal with the possibility of fires. After flight eight, SpaceX insisted that the problems that Starship faced were completely different\u2014but bloggers and Redditors passed around a purported leak from an insider saying that the root issue hadn\u2019t changed. It was \u201charmonic oscillations\u201d\u2014vibrations, again, this time busting methane lines running through the liquid oxygen tank again: When the tank was full of liquid oxygen, it dampened the vibrations. But as the tank emptied, the shaking got worse.<\/p>\n
Starship\u2019s two stages have to structurally support nearly 11 million pounds of fuel; the upper stage is meant to carry as much as 330,000 pounds of payload. So the vessel itself has to be as light as possible\u2014yet still withstand the buffeting forces of launch and reentry. So far, it has not. \u201cThey\u2019ve designed their structure light enough to perform when the rocket ignites and wants to fly, but maybe\u2014and this is speculation\u2014when they\u2019re loading the fuel, that\u2019s causing cracking,\u201d Dec says. \u201cWhen a structure is cooled, it shrinks. If it\u2019s rigid and can\u2019t move, that\u2019s going to cause a stress, and it\u2019s going to break.\u201d<\/p>\n
A couple other pieces of evidence fit this theory. One reason the booster may have survived flights that the upper stage did not is that the booster doesn\u2019t go all the way to space, and it comes back to the ground at only about 4,600 miles per hour. Starship\u2019s upper stage goes all the way to orbit and reaches 17,500 mph. That\u2019s a lot of kinetic energy to get rid of on reentry\u2014usually as heat. \u201cThis is the physical constraint,\u201d Ifti says. \u201cWe can\u2019t get away from it. We have to manage this energy being generated through heating.\u201d<\/p>\n
An early version of Starship tried to bleed off that kinetic energy with a kind of aerodynamic belly flop that ended in a catastrophic loss of control. Now the vehicle uses its control surfaces and rockets to slow its descent and relies on heat-resistant tiles (which, of course, add weight). One persistent critic of SpaceX, Will Lockett, has argued that Starship simply must use more propellant than its builders expected for its return flights, adding even more weight. \u201cThis puts incredible pressure on SpaceX to save weight anywhere they possibly can,\u201d Lockett wrote in his newsletter in March. \u201cSpaceX is having to make the rockets too light, resulting in them being fragile, meaning that just the vibrations from operation with a fraction of its expected payload would be enough to destroy the rocket.\u201d<\/p>\n
Kaboom.<\/p>\n
\n
Maybe this build-test-destroy-rebuild cycle is what you\u2019d expect from a cutting-edge company like SpaceX, which owes much of its astonishing success to iterating like a software start-up. The version of Super Heavy that\u2019s set to launch on Sunday has some major design changes, increasing the size and strength of the winglets called \u201cgrid fins\u201d but reducing their number from four to three and aiming for a more controlled, higher angle-of-attack descent. Starship\u2019s upper stage will also test several new kinds of tiles to protect against the ferocious heat of reentry. This is what coders call \u201cagile.\u201d<\/p>\n
In practice, though, this Silicon Valley\u2013style approach forces SpaceX to play a very expensive game of Whac-A-Mole. \u201cThe way I read what Elon\u2019s trying to do, wow, is it complicated. And when you deal with a very complicated device, there\u2019s multiple modes of failure,\u201d says Joseph Powers, an aerospace engineer at the University of Notre Dame and editor in chief of the Journal of Propulsion and Power. \u201cWith a rocket, that almost always results in detonation.\u201d<\/p>\n
Each failure is supposed to be an opportunity to learn to avoid disaster the next time. \u201cThey\u2019re facing challenges, but I don\u2019t see any showstoppers,\u201d McDowell says. \u201cI don\u2019t want to minimize the problems they\u2019re having. It is embarrassing for SpaceX, and they do have to fix these things, but they are making progress.\u201d<\/p>\n
So there\u2019s an easy solution: reduce the weight of the payload Starship can carry and charge more per pound. But even if SpaceX and its customers can absorb the higher price, not all of Starship\u2019s planned missions can necessarily wait for a more reliable spacecraft. NASA\u2019s Artemis III is supposed to use Starship to land astronauts on the moon\u2019s south pole in 2027. That\u2019s practically tomorrow, in aerospace time. Plus, even if you didn\u2019t already think that ionizing radiation and toxic regolith make Musk\u2019s dreams for Mars settlement about as likely as finding canals there, a reduction in Starship\u2019s cargo capacity and rapid reusability would seem to doom the plan. One model for making the trip in three months instead of the usual six or nine requires four cargo Starships and two crew Starships and assumes a total of 45 launches\u2014a mere fraction of the 1,000 Starship launches per year SpaceX foresees.<\/p>\n
Even McDowell, who\u2019s more sanguine about the tech, acknowledges the possibility that there\u2019s something more existential at play. \u201cEvery time you add a widget to fix something, you increase the mass and decrease the payload capacity,\u201d he says. \u201cThat\u2019s the key question we don\u2019t know in the public domain: To what extent are the fixes causing performance losses?\u201d Musk and SpaceX share a reputation for bold technological wins\u2014they blew up a lot of Falcon 9 rockets before that vehicle became the ultrareliable, game-changing satellite launcher it is today. But investors and customers won\u2019t wait for Starship forever. For a would-be rocket builder, the only thing worse than a kaboom is silence.<\/p>\n","protected":false},"excerpt":{"rendered":"
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