Wed. Sep 28th, 2022

Again, on Tuesday afternoon, a prototype Starship rose in the clear skies over South Texas like something out of the pages of a science fiction novel. Again, after reaching a great height, the spaceship leaned into a “belly flop” maneuver, making a controlled descent back to the planet.

And then, again, a problem in the last few seconds caused the Starship prototype to spectacularly crash near its launch pad.

Seven weeks have passed since the first complete Starship prototype, SN8, completed its high-altitude flight. Now SN9 has suffered a similar fate. It turned out that one of the two Raptor rocket engines intended to power the final controlled descent failed to re-ignite (see a great slow-motion display† As a result, when the vehicle began to reorient to a vertical position, it never stopped swinging. Than, TREE

So how about a second high-profile failure of the Starship program? Is this a program that is about to fail?

“Stupid difficult”

We probably need to step back to better understand what SpaceX is trying to do with Starship. This vehicle is the second stage of a launch system with a large booster called Super Heavy. With its Falcon 9 program, SpaceX has shown that it can launch and land a rocket vertically. But the real trick is in Starship – specifically, bringing it back from orbital speed and through the atmosphere safely so it can be launched a short time later with minimal refurbishment.

In late 2019, while I was working on a book on the origins of SpaceX, founder Elon Musk invited me to attend technical meetings so I could get a sense of his leadership style. During one of these meetings with the Raptor engine team, Musk pushed back on a decision his team wanted to make that would fractionally reduce the specific impulse (ISP) of the engine. He wasn’t happy. As Musk well knows, if you build a rocket, if you add mass or lose performance, you lose the battle against gravity.

“That’s why we fight for masses, and we fight for every split second of ISP,” he told his team at one point. “Especially with a reusable upper staircase, which no one has ever managed to do. FYI. It’s not as if they were huge idiots trying to throw their rockets away all the time. One of the hardest technical problems known to man is creating a “Reusable orbital rocket. It’s crazy hard to have a completely reusable orbital system. It would be one of the greatest breakthroughs in human history.”

As he delivered this little speech to his engineers, Musk’s mood steadily mellowed. Soon he was joking with the team. His point was made. Yes, he understood what he was asking of them. It was damn hard. It would hurt their brains. It hurt him. But they had no choice but to face the technical challenges.

SpaceX has come a long way in the 16 months since then, going through about 10 different Starship test vehicles and tank designs to reach SN8 and SN9. Much of the time of the Starship program, since late 2019, has been focused on building a factory in South Texas to produce Starship prototypes. The company can now run these stainless steel spaceships at the rate of a few per month. SN10 is already approaching readiness to take its turn on launch and landing. The flight can come as early as the third week of February.

This is an advantage of running a hardware-rich program, like the one SpaceX built with its Starship assembly line. It also helps that Musk has adopted a failure-is-an-option mentality. He can, of course, still get angry about failures. But they are an acceptable part of an iterative design program that allows him to act quickly.

Iterative vs Linear Design

The question is whether we celebrate these SpaceX failures too often. After all, when NASA first fired its Space Launch System rocket in January, failure to meet its test targets was met with criticism rather than approval. Is this hypocrisy? Another sign that the Musk cult has run amok? Not really.

NASA and its prime contractor, Boeing, spent literally ten years designing and building the SLS rocket, and they produced a single core phase at that time. The American taxpayers have footed the bill for all this, nearly $20 billion. NASA didn’t even have to build the engines — the SLS rocket uses the space shuttle’s main engines that have flown several times. That’s not to say it isn’t hard — building a rocket is.

However, by following a linear design methodology and satisfying Congress, NASA cannot afford to fail. With linear design, years are spent designing and testing small pieces of a project, and only after much analysis are the components assembled and tested. This is the safest way to build a vehicle that has the best chance of success the first time. But it is also expensive and long-winded.

The test program that NASA is conducting for its SLS rocket is therefore not so much a development campaign, but a validation campaign. If there is a problem with this core phase, the second will leave its factory in southern Louisiana by mid-2022 at the earliest.

Meanwhile, in South Texas, SpaceX has half a dozen Starship prototypes. None is a refined or finished product like the SLS rocket. They are rough prototypes. But each probably cost a few million dollars to build, plus the cost of the engines. This is an essential part of an iterative design campaign: each vehicle improves on its previous model, contains lessons and allows errors. This process allows a company to act quickly and make mistakes.

And SpaceX has so much more to learn about Starship. This top-stage rocket doesn’t simply have to fire its engines for eight minutes and then fall into the ocean, like the SLS nuclear stage. It must be able to make multiple relights of its engines, survive weeks or even months in space, and re-enter Earth’s atmosphere with minimal effects to ensure rapid reusability. And then it has to stick to a landing. This isn’t an easy to-do list for something several times the size of a school bus traveling 25 times the speed of sound.

So SpaceX still has a long way to go. In the words of SpaceX engineer John Insprucker, who commented on Tuesday’s launch attempt, “We still need to work a little bit on that landing.” Yes. That and a million other things before satellites, let alone humans, fly into space on Starship.

It’s crazy hard work. But is anyone doubting whether SpaceX will get there?

List image by Trevor Mahlmann

By akfire1

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