IFT 8: Spacex’s Great Filter Moment

Transcript:

IFT 8: Spacex’s Great Filter Moment

Welcome to the edge of space.

I’m your host, Randall C Kennedy.

Today’s hot topic is heat shields. Pretty much all returning orbital space vehicles have one. They are what allow these tortured vessels to survive the insane conditions of atmospheric reentry. Without them, things could get quite toasty inside as all that super-heated plasma from atmospheric friction tries its darndest to find a way over, around, or through the offending spacecraft.

In fact, an intact, functioning heat shield is quite possibly the most important piece of equipment on any space vehicle that hopes to return safely to earth. As the saying goes, you can leave this world without one, but you ain’t coming back.

Thankfully, spacecraft engineers have become quite adept at designing and building safe and reliable heat Shields – provided you only intend to use them one time. The challenge is creating one that can be used repeatedly and without significant refurbishment or maintenance.

NASA tried back in the 1970s to create a reusable heat shield for the space shuttle program. And though the vehicle itself was ultimately reusable, most of its super critical heat shield components failed to live up to that lofty reuse goal. The shuttle’s heat tiles were quite brittle and often significantly damaged or even destroyed during the reentry process, requiring lengthy replacement and refurbishment work in between flights.

Since then, most spacecraft designers have abandoned the idea of a reusable heat shield, at least for orbital craft that must return sensitive – or more importantly, living – cargo to Earth. Instead, they typically rely on ablative heat shields that burn away a bit as they pass through the hellish inferno of the planet’s upper atmosphere. In some cases, these ablative heat shields can be repaired and refurbished enough for the spacecraft to fly again – case in point, SpaceX’s dragon capsule.

However, with Starship, SpaceX hopes to overcome the nagging limitations of traditional heat shield fragility, an obstacle which threatens to hold back the entire program. You see, it doesn’t much matter if SpaceX can launch, catch, and relaunch both ship and booster if, in between those flights, they have to do time consuming maintenance on the heat bearing parts of the vehicles.

And as the Starship program has evolved, SpaceX has devoted more and more resources to tackling this sticky problem, to the point where they’ve now gotten into the heat tile manufacturing business themselves, with at least 2 dedicated factories – or bakeries – set up to produce tiles exclusively for the Starship program.

But it gets better. SpaceX isn’t just manufacturing its own tiles, it’s experimenting with different combinations of materials and chemical compounds in order to achieve the perfect balance of tile size, weight, and durability. So, SpaceX is no longer just a space vehicle manufacturer. It’s also in the materials science business – out of necessity, because no existing material or tile design has proven capable of meeting the company’s stringent requirements.

Elon Musk alluded to some of these issues as part of a fascinating sit down with everyone’s favorite podcaster, Joe Rogan. During the interview, Elon talked about the challenges of creating these tiles and how the company has experimented with all sorts of different compounds, including its latest, a mixture of silicon and aluminum oxide, which you might know as sapphire.

Now, sapphire is tough stuff. Chances are, if you own a modern smart watch, you’re wearing a piece of sapphire right now as it’s a popular material for constructing durable watch faces. Still, SpaceX’s latest iteration of its heat tile design has yet to be fully tested, because testing these tiles was among the many goals of the ill-fated IFT-7.

RIP, good buddy!

I touched on that debacle in my previous video. The failure of IFT-7 has put even more pressure on SpaceX to successfully return its next prototype in the pipeline, Ship 34, as part of the upcoming IFT-8 – at least far enough to get good data on the heat tile performance. Because, until they successfully solve the problem of creating a durable, non-ablative heat shield, the fundamental goal of the entire Starship program – namely, rapid reusability – will remain out of reach. All their work to date will have been for naught, which is why I’ve dubbed the need to overcome this nagging obstacle the “Great Filter” to orbital spacecraft reuse.

In case you’re unfamiliar with the concept of the Great Filter, it’s one of the answers posited to the question of the Fermi paradox – i.e., if the universe is full of potentially life sustaining worlds, where the hell is everybody? The great filter theory states that any sufficiently advanced civilization ultimately reaches an inflection point beyond which they either transcend to the next stage of their evolution…or they destroy themselves through some cataclysmic event or miscalculation.

During his interview with Joe Rogan, Elon Musk spoke at length about his motivations for trying to make the human race multiplanetary. He worries, as do many others, that the spark of human consciousness is one Great Filter type cataclysmic event away from being snuffed out forever. Hence why he’s so hell bent on creating a fully reusable spaceflight system that can move the million plus tons of cargo to Mars that will be required to establish a self-sustaining colony.

So far, SpaceX has achieved nearly all its goals for the design of the Starship and Super Heavy vehicle stack. In fact, the only remaining obstacle that isn’t a simple engineering problem is those pesky heat tiles and their habit of getting damaged or destroyed during ship reentry – to a point where replacement becomes necessary to ensure the continued safe operation of the system.

Now, during the interview, Musk seemed to put on a brave face when discussing the company’s progress in licking the heat tile problem. However, I can’t help but feel he was engaged in a bit of wishful thinking, perhaps driven by his strong belief in himself and the ability of his team to overcome seemingly intractable challenges. After all, these people did manage to land dozens of rocket boosters over literally hundreds of missions, something once thought virtually impossible by the spaceflight community.

But in each step towards recovering that first Falcon 9 booster, and later the 5^th and 7^th super heavy boosters, SpaceX was mostly solving engineering problems. With the heat tile issue, they’re dealing with science at a much more fundamental level – literally down to the periodic table and how various elements interact with one another in extreme conditions. And though Elon waxed confidently that the company would solve the problem this year, we still have seen no evidence that any of their designs will meet the demands for rapid reusability. Hell, we can’t even be sure that a passive heat shield solution is the correct one. Some experts believe that active cooling, using chilled propellant passing through the affected hull regions, would be a reliable and possibly more durable alternative. However, such a radical design change at this stage in the development process would almost certainly set back the entire Starship program by many months if not years.

Which is why IFT-8 may prove to be one of the most important Starship missions to date. If SpaceX’s latest formulations hold up better than their predecessors, then there’s still hope that Elon’s bravado wasn’t misplaced. But if its new tiles don’t deliver the required performance, you have to start wondering if the irresistible force of Mr. musk’s will has finally run up against the one immovable object that could thwart his noble vision for humanity.

Of course, the above presupposes that ship 34 fares better than ship 33 did. Here’s hoping SpaceX really has solved the engineering issues that sabotaged that prior flight so they can move past the training wheel stage of the Starship program and start zeroing in on the final boss level challenge – bending the laws of chemistry and physics to create the unobtainium of Space Flight: a durable, reusable heat tile material.

Anyway, thanks for watching. If you liked this content, let the world know by smashing that like button and subscribing to the channel. And don’t forget the notification bell so you’ll be alerted the next time I feel the urge to rant about something Space related.

Until then, remember: don’t look up! Because birds really don’t care where they poop!