Moving Fast and Breaking Starships

Not being retired, I can't drop everything I'm doing and run down to Boca Chica at the southern tip of Texas and wait till Elon Musk's SpaceX organization decides to launch a Super Heavy booster with a Starship on top of it.  But I'd like to, as it's a shorter trip than the drive to Florida to watch launches at the Cape. 

 

But it turns out that if I was looking for a spectacular aeronautical display, Florida would have been the better place to watch last Thursday's launch from, which took place after sundown that evening.  The Super Heavy booster did its job, successfully separating from the Starship second stage, and even returned safely to the launch pad as designed.  But an "energetic event," as the controllers termed it, happened inside the Starship shortly thereafter, shutting down several of its engines, destabilizing it into a spin, and causing it to explode.  Numerous posts to social media from Florida and the Caribbean show a constellation of flaming objects streaking across the night sky.  According to Reuters, a car in the Turks and Caicos Islands was slightly damaged by a piece of the rocket that fell out of the sky.  But not to worry—SpaceX says there were no toxic materials in the debris.  Nevertheless, the Federal Aviation Administration stopped flight takeoffs from several Florida airports briefly because of "space launch debris," and launched its own investigation into the failure. 

 

According to a Wikipedia article on the Starship, there have been eight flight tests so far of the integrated Super Heavy booster and Starship orbital vehicle, beginning in 2022.  Three (the fourth, fifth, and sixth) were entirely successful in the sense that both rockets took off and landed intact under control.  The first three and the last two, including last week's test, ended with at least the Starship blowing up, although the booster seems to be working more reliably. 

 

Characteristically, Musk termed the latest test a "minor setback."  Maybe it's minor to one of the world's richest men, but to people in Florida and the Caribbean, a small but non-zero chance of having a piece of rocket come down on your head is perhaps something more than minor. 

 

Comparisons between SpaceX's exploits and the NASA manned spaceflights of the 1960s are inevitable, at least to someone like me who lived through them both.  The Falcon 9 spacecraft, which was the first significant rocket to be introduced by SpaceX, was first launched in 2010, and it was not until ten years later that the company risked putting people on it.  By then it had proved to be one of the most reliable orbital workhorses ever designed, so the risks were reasonably well known. 

 

Although the U. S. space program started off with an embarrassing failure—the December 1957 attempt to orbit a satellite after the Soviet Union beat us into space—it quickly recovered and to my knowledge, there were no major rocket explosions, certainly none with people aboard, until the famous Apollo 13 lunar-orbit service-module failure, which almost left the astronauts stranded. 

 

So we can regard the last two Starship failures as growing pains, perhaps, and look forward to many more before the track record improves to the extent that anyone smart enough to train as an astronaut will be willing to step aboard for a ride.  The question now is whether we should put up with falling space debris indefinitely while SpaceX works the bugs out of its rockets.

 

So far, no one seems to have raised any show-stopping objections.  SpaceX and Musk are formally at the mercy of the FAA, which has to approve each launch and has the power to shut down the entire operation if they decide that the hazards to the public are too great.  Fortunately for Musk, Floridians are used to having rockets around, and there are enough former space-business employees and military personnel in Florida that having a few fireworks fly over now and then doesn't seem to bother them in any major way.  If SpaceX had chosen an orbital path over New York or California, on the other hand, we would probably have heard a lot louder protests and a call to cease and desist.

 

As long as Musk doesn't run out of money, SpaceX will keep trying with the Starship, and once the bugs are worked out the rocket's built-in advantages will come into play.  The goal is to get the cost of each launch down to $10 million or less, which is a factor of ten less than it currently costs.  But there are a lot of fundamentals in place already.

 

Take fuel, for instance.  Instead of using exotic and hazardous fuels such as hydrazine, the engines burn liquid oxygen and liquefied methane, which is the same stuff that people with natural-gas hookups burn in their stoves.  Both the fuel and the oxidizer are relatively cheap and common industrial products. 

 

The rockets themselves are reusable, and ideally will return to the launchpad like all the old sci-fi stories said they should.  What isn't commonly appreciated these days is the spectacular recent advances in automated control systems that both make autonomous drones possible, and amazing feats like rockets landing themselves on launch pads without human intervention.  Such tricks simply weren't safely possible in the 1960s or 1970s, but we have the technology to do it now and SpaceX is using it.

 

I hope that the SpaceX engineers figure out exactly what's making the Starship blow up, and remedy things so that we can have a row of ten or more flawless takeoffs, orbital trips, and landings.  I suspect something on the order of that kind of track record will be required before any humans are allowed on board.  By then, maybe I'll be retired and have the time to go down to Brownsville and hang out for a few days, waiting to see the next successful launch of a Starship.  And if I want to see any fireworks, I'll just buy them myself.

 

Sources:  I referred to the Reuters report on the latest Starship launch and failure at https://www.reuters.com/technology/space/spacex-launches-eighth-starship-test-eyeing-ships-mock-satellite-deployment-2025-03-06/, and the Wikipedia article "SpaceX Starship."

Space Flight: A Risky Business

The commercial space flight business suffered a one-two punch last week.  On Tuesday, an unmanned rocket carrying supplies for the International Space Station and launched by Orbital Sciences Inc. failed a few seconds after launch, falling back to the launch pad and exploding to make a spectacular nighttime video that must have been shown on every TV outlet in the U. S.  It was the company's third commercial launch of a contract to supply the Space Station, whose residents will now have to wait a while longer for the next garbage pickup.  (A side benefit of the long-distance unmanned deliveries is that the Space Station folks can cram the vehicle with their trash and let it burn up in the atmosphere.) 

And then Friday, Virgin Galactic's SpaceShipTwo, manned by two experienced test pilots, broke up high above the Mojave Desert in California, killing pilot Michael Alsbury, 39, and injuring the other, Peter Siebold.  The crash scattered debris over a five-mile-long area and initiated an investigation by both Virgin Galactic and the U. S. National Transportation Safety Board which could take as long as a year.

Any time anyone is injured or killed in a space-related accident, engineers are obliged to get to the bottom of the technical whys and hows of the mishap.  But beyond the specific technical causes of these particular accidents, tragic as they were, is the question of how reliable commercial manned space flight is going to be.  And a little history can throw some light on that question.

A man named Ed Kyle maintains an extensive statistical study of space-flight launches at a website called www.spacelaunchreport.com.  He compiles both unmanned and manned flights, although in the nature of the business, the vast majority of launches are unmanned.  Bearing that in mind, we can look at a convenient summary table he provides of success rates of launches by decade, going all the way back from the infancy of space flight in the 1950s to the 2010s. 

America's first attempt to launch a satellite into orbit, the Vanguard launch on Dec. 8, 1957, was a highly publicized failure, exploding after reaching the breathtaking altitude of four feet (1.2 meters).  And overall, only about half the launch attempts by all parties in the 1950s were successful.  But aerospace engineers began climbing that long haul called the learning curve, and by the 1970s the average success rate was around 95%, where it has hovered ever since.  In the last two complete years, for example (2012 and 2013), Kyle logged 159 launch attempts and 9 failures among them, for a failure rate (for the pessimists among us) of 5.6%.  So even today, forty years after the space-rocket business reached maturity, there is about one chance in twenty that your satellite will not end up in space, but in a watery or earthy grave.

Despite all the fuss about NASA turning space flight over to commercial interests, satellite launches have been commercial transactions for decades.  And it appears that a failure rate of 5% is an acceptable level to support a generally prospering space industry.  The companies and their insurers can handle that level of failure and still accomplish what they want to do, most of the time. 

But launching cans of beans for a space station, and launching people who have paid a quarter of a million dollars for the ride (as prospective passengers in the Virgin Galactic rocket have coughed up in advance), are two different propositions.  Commercial airlines would not have many customers if it were well known that one out of every twenty flights was going to crash.  It took the business of aviation twenty years or so to be safe enough to offer commercial passenger service, but by 1930 or so the risks of commercial scheduled flights to the individual passenger were largely imaginary, and today you take more of a risk of dying on your drive to the airport than you take in the air. 

It may be harder for the space-flight engineers to drive their failure rates down to the level at which people could buy space-flight life insurance for a few dollars, like you used to be able to do for commercial aviation flights at airports.  Rocket hardware operates at the outer limits of materials science.  The engines run so hot that liquid-fueled nozzles have to be cooled continuously to keep them from melting, and the fluid dynamics of the combustion of rocket fuel is still so complex that an exhaustive, essentially complete mathematical model of a rocket in flight, including vibration modes and so on, is quite possibly still beyond our abilities.  So rocket designs are a combination of science-based modeling and engineering intuition, added to a large measure of experience of what has worked in the past.

I think it is significant that the Virgin Galactic flight was using a different type of fuel than they had used in previous flights.  Such a major change, even if tried out on the ground with similar hardware, can lead to unpredictable results, and may turn out to have contributed to the disastrous crash of SpaceShipTwo.  Rocket engineers, at least the successful ones, tend to be highly conservative in their designs.  Anyone who has seen both an old V-2 rocket engine in a museum and the massive Apollo engines used to launch men to the moon can see that Wernher von Braun found something that worked at Peenemunde, Germany in the 1930s, and stuck with it all the way through the 1960s. 

Such conservatism is increasingly rare among engineers in general today, influenced by innovations in hardware and software which happen so fast that you can squeeze an entire product life cycle, from introduction to obsolescence, into six months.  But the adage "if it ain't broke, don't fix it" applies in spades to space travel.  And as we find out in the coming months what caused SpaceShipTwo's failure, we may find that experimenting with a different fuel was a bad idea. 

Unless we colonize the Moon or Mars to a great extent, space travel will always be an exotic, low-volume business, like tours to the Antarctic are today.  And it is by no means clear to me that even the super-rich will be willing to take the kind of risks that simple statistics tell us space travel entails—at least, not for quite a while yet.

Sources:  Ed Kyle maintains his Space Launch Report at http://www.spacelaunchreport.com.  I referred to an article carried by the BBC on the Virgin Galactic disaster at http://www.bbc.com/news/world-us-canada-29869070

and by www.space.com on the Orbital Sciences launch failure at http://www.space.com/27615-antares-rocket-explosion-timeline.html.  I also referred to the Wikipedia article on the Vanguard (rocket).