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I have had multiple people ask me to make a prediction for tomorrow's scheduled SpaceX launch. I don't want to do this again, but I suppose I'll oblige.
My prediction last time that SpaceX’s Starship would cause “A Lot More Damage Than Anyone Thinks” wasn't based on any inspired divination about rocketry but rather because I correctly observed the company's actions in context of the law. I am a neophyte in the dark arts of aeronautics and rocket science, but knowing a little about the manner in which people act when under pressure, as well as having experience in fields like process and civil engineering, helped me make some reasonable projections.
SpaceX didn't eschew installing a deluge system or flame diverter prior to launch #1 because the company had confidence these safety protections were not needed. SpaceX insisted all was well because they *had to* in order to launch quickly. Safety on this front wasn't part of the equation because SpaceX had neither the physical space nor the authority to install what they needed.
The result: I made a prediction that turned out a lot better than many so-called experts did.
SpaceX's Texas Rocket Caused a Big Mess - What's Next?
SpaceX now has a brand new water sprinkler/metal pad to launch from that (while very illegal to operate under Environmental Law), which will prevent another catastrophe like we saw in April. Or at least that’s what the FAA and SpaceX insist.
I still know the NEPA environmental impact study for Starbase is nonsensical number fitting. SpaceX's launch site is far too small to operate reasonably safely, and it sits far too close to protected habitats that SpaceX will degrade the more time they spend doing their thing. But what about the launch? Here are my thoughts:
Water will help a lot. Provided there is sufficient flow and total volume of water present under the white-hot, powerful engines, this should alleviate lots of issues. Yes, the water that flows off site is an illegal discharge. But the physical properties of water, specifically its high heat capacity and incredible sound and energy dampening abilities while in liquid, droplet and vapor forms is critical.
Is there enough water? I don’t know, but it is much less than used at other mega-rocket pads for a launch event at Kennedy Space Center.
Stainless steel has some helpful (and concerning) physical properties. Before launch #1, SpaceX insisted that heat-resistant Fondag concrete would work as a launching surface. In the real world, Fondag did not do the trick at all, as it was easily ablated much like smashing styrofoam with a hammer.
This time, the star of the show is thick steel. Steel cannot be blasted into chunks. That's good. But the incredible forces and heat of methane combustion exerted would destroy the pad, and it “would need to be replaced after each launch attempt,” per SpaceX's own admission, in the absence of sufficient water.
Another issue with steel that no one wants to discuss is how easily it reflects sound. A few studies suggest that such a thick smooth steel plate would have a sound absorption coefficient of effectively zero. These studies are predicated on sound at frequencies and intensities well outside the swirling caterwaul of a rocket engine, so caveats apply here, but it's safe to say that a flat face of steel would rather reflect sound back than absorb it. It’s one of the worst materials imaginable for dampening sound (hence the water). Given that there is no diverter to deflect sound away from the rocket, these rebounded forces would bounce back onto the rocket itself, especially if there isn't enough water present. That could cause some issues if there isn’t enough water.
SpaceX employees are probably freaking out. I'm not talking about normal pre-flight jitters. I really do not think there is any confidence the steel plate will work. If it doesn't, that might be game over for Starbase.
But, even beyond that, the real issue is the very idea of a safety factor. Former and current NASA employees I've spoken with have often told me that the agency uses extreme overkill on building safety factors. If a reasonable safety factor exists for something at a dimensionless value of 1, NASA will insist on having a factor of 2-3x when implemented for flight. This can be for redundant equipment, safety protocols, or the volume of water needed for adequate vehicle protection. Doesn’t matter. NASA says, “Double it.1”
SpaceX has succeeded, in large part, because it insisted on ratcheting these safety factors back. This isn’t inherently bad, though. Spending two times the amount of resources on something for little to no incremental gain in risk-adjusted safety is absurd. The fear here isn’t that SpaceX has dialed back the safety factor back to 1. It’s that they’ve now gone to 0.5. The water-cooled plate is probably in that safety margin neighborhood. It doesn’t mean rockets launched from the Starbase sprinkler will always blow up. Or even that they’ll blow up most of the time. It’s just that risks are far higher than the public believes and more significant than projected by the company.
Tomorrow's flight is a suborbital mission. With less thrust needed to get the rocket off the pad, even a nominal success shows very little about the durability of the pad. No doubt SpaceX will learn plenty during the flight about how the rocket performs in air, and as a non-expert in rocketry, that sounds great, I think.
The other question people ask me is this: if the Rocket clears the pad, will the rest of the flight be a success? My answer: I have no idea, and you'd get an equally informed view by flipping a coin. That's probably a good call for considering the opinion on the matter for most internet commenters as well.
All I can say about the launch tomorrow is: “Enjoy the show 🍿🍿🍿”
It’s obviously more complex than this. The numbers used here are for illustration purposes only.