SpaceX finally revealed its Starship & Super Heavy landing trick!

This episode is sponsored by Brilliant. For the first time, we fully explain, how and why SpaceX will try to catch the largest rocket ever built out of mid-air. My name is Felix, and I am your host for today's episode of What about it!? And as always, there's been a lot going on in the space industry lately, so let's dive right in! Why take the risk? This time, it's all about the truth. Since Elon Musk and SpaceX announced the idea of planning to catch Starships and Super Heavy boosters out of mid-air, the space enthusiast's world has been wondering and speculating, how exactly it will happen. Now, Elon Musk has unveiled the first real and hard data, which for the first time gives us the means to fully explain, how exactly a Mechazilla catch works and why the heck SpaceX is daring so much in the first place. Why risk it all to perform the largest party trick ever? Let's dive right in! The real deal. Directly from SpaceX's internal simulations. We have all the data now. Body acceleration and body rates on XYZ and the corresponding altitude. Suppose, you're not familiar with the XYZ coordinate system. In that case, it is a way of precisely showing a position in a three-dimensional space. Also referred to as the Cartesian coordinate system, it shows X and Y as the position on a plane and Z refers to the height. And Musk didn't just show the movement from directly above Mechazilla, but all the way from the beginning of the final landing burn. So, the first exciting thing to note here is, that the landing burn starts at roughly 1800 meters above Mechazilla. Back on Episode 200, I compared Super Heavy with a Falcon 9 booster. So, let's take a look at which point a Falcon 9 booster starts that re-entry burn. There you go. 1800 meters. So, it's almost exactly the same as what's planned for Super Heavy. Same tech. Same results. Super Heavy basically is a Falcon 9 on steroids. We can also see, that the booster very much comes in at an angle. This is likely, because SpaceX will do a so-called dogleg maneuver to protect orbital launch mount and Mechazilla if something goes wrong in the early approach phase. And to use as much lift from the booster's body as possible to further slow down the descent, as can be seen in an official SpaceX graphic depicting a Falcon 9 launch and landing. Aerodynamic guidance. Grid fins steer. Lift produced by first stage. Again, SpaceX wants to do exactly the same thing as they do with Falcon 9 boosters right now. Then, at around 800 to 700 meters above the pad, the booster switches from using 13 center engines down to only three, creating a massive bump in the body acceleration graph. Since there's an engine shutdown, the TVC of the remaining three engines has to fight to keep the booster on track. The same can, for example, be seen on every high-altitude Starship flight test. It doesn't matter, if the rocket is going up or down. Whenever an engine shuts down, the remaining ones have to compensate for the sudden change in thrust with their thrust vector control or TVC, also called engine gimbal. Raptor engines have clearly demonstrated, that the current avionics and TVC hydraulics can do it on Starship flights. This is also when the booster becomes too slow to produce any meaningful lift. So, it turns its engine section straight down as it positions itself above the Mechazilla chopsticks. I cannot wait to see this in reality. Even watching this simple animation gets my heart rate up. Shedding more and more velocity using the three remaining Raptor engines on the final approach, the booster carefully positions itself right in the middle of the chopsticks and with its grid fins pointing left and right. Ryan Henson Space released a spectacularly detailed animation just two days ago. He worked with Ova from SpaceX 3D Creation Eccentric and showcased how SpaceX will be lifting booster 4 onto the orbital launch mount utilizing the Mechazilla chopsticks. Now, this animation is not about landing. Still, it does show the chopstick mechanics like no other animation before, and those are the same no matter if you lift or catch a booster. This is what I want to point out. The booster will come to rest on the chopsticks with these lift arms or anchors here. And those are positioned in the middle of and directly under the grid fins on either side of the booster's hull. So, in the end, it will be absolutely vital for the booster to come down with the grid fins oriented towards the chopsticks on both sides. But again, we do have something to compare Super Heavy to. Falcon 9. So, is SpaceX capable of controlling the rotational movement of their boosters on descent? Here we go. One of the best landing footages ever presented by SpaceX. Saocom 1B from October 8th of last year. Uninterrupted footage all the way from space to LZ1 at Kennedy Space Center. And at the very end, just meters above the pad, we can see rotational movement. Still, we can also notice, that this very much seems to be under control. The booster can rotate back and forth and on the final meters it doesn't rotate at all. This is because the rotational movement should be relatively easy to control using grid fins. And since Super Heavy will be using exactly the same system, it should be precisely the same process. In theory. And what if it's not in the absolutely perfect position? Mechazilla already has a system in place to tolerate a few degrees of the rotational axis. Over from SpaceX, 3D Creation Eccentric has made a great animation to show, how this will work. Pushers close in on the booster after the catch and guide it on both sides to that perfect center position to be able to precisely place it on the orbital launch mount again. Rapid reusability. SpaceX has one huge advantage. They already know about all this. After 101 landings of an orbital class rocket booster, they are still the only launch provider in the world to possess this know-how. And it's precisely as predicted on Episode 210 days ago. In theory, the chopsticks wouldn't have to move much up or down at all during the catch. It is not a crazy agile robotic arm moving along with the booster's path for several reasons. The orbital launch integration tower or Mechazilla is enormous. The chopsticks alone likely weigh around 100 tons each. Even though the drawworks used to move them up and down has 6000 horsepower, the inertia of such a super heavy setup alone would be enough to stress the cable connection between winch and chopsticks immensely if it were to move abruptly. And last but not least, Falcon 9 doesn't need the drone ship to have any sort of dampening besides the honeycomb crush blocks inside the Falcon legs. These are the legs of a Falcon 9 booster after a landing and as you can see, there is a measurement on the lowest point of the leg dampeners. That is there because there is a honeycomb structure block inside those legs, dampening the landing each time a Falcon 9 sets down on a drone ship or at the landing zones at the cape. These crush blocks are non-reusable and require SpaceX to refurbish the legs each time a booster has landed. For a Starship or Super Heavy, that's not an option as there simply are no legs. So, what does SpaceX do instead of moving the Mechazilla arms down to dampen that last bit of vertical movement? The bars to work as the landing surface for the booster's catch points are movable. Up and down. It's not much, but the travel distance is comparable to what a Falcon 9 leg solves with its crush block. This is not confirmed yet, but this might be the last puzzle piece that we're still missing. That last bit all the way from space down to z plus zero really needed to be as soft as possible. It's not much at all. Just a few centimeters in theory. That's all that's needed from 100 kilometers above the planet down to the resting position. If that last tiny bit was soft, it would work. Is that all it takes? What's your thought? As always, tell me in the comments! And it's that tiny movement that's needed for the WAI team too. Just a few centimeters below this video, there are two buttons. So, before we continue, like and subscribe! That's all that's needed to help us with our channel! And if you're crazy enough about our content, click join or follow the Patreon link in the description to get access to early and ad-free releases of every episode and access to our Discord server! Or get yourself the latest WAI shirts like the ones I wear on every show! Thank you for your support! You Rock! Jumping back into our booster catch simulation directly from Elon's development team, let's take another look at the very last part of the catch. Notice, how long the booster hovers in the air. That's at least 5 Mississippi's of hovering. It's not a suicide burn like what we're used to seeing on a Falcon 9 landing. Every Falcon 9 booster uses the same technique to achieve zero velocity. It's called a suicide burn. SpaceX does this for two reasons. One is fuel consumption. If you do a suicide burn, you use as little fuel for the landing as possible, as hovering basically is wasted energy. Secondly, a Merlin 1D engine as used on the Falcon 9 booster has too much thrust and by design can't throttle down enough. The booster on its own is so light before touching down as its tanks are almost completely empty, that a Falcon 9 can't hover. If the engine continued its burn, the booster would come to a standstill and then start going up again. Even when completely empty, a SpaceX Super Heavy booster weighs far more than a Falcon 9 booster. Around 200 tons. The minimum throttle range of a Raptor engine will likely be somewhere around 40% of its total thrust. From Elon Musk, we already know that currently the thrust should be at around 220 tons when running at 300 bar chamber pressure. 40% of that would be 88 tons. Times 3, we'd be at 264 tons. A bit too high, but SpaceX could in theory shut down two additional engines and do the hover with one engine, which would be risky, or the throttle range of a Raptor 2 is even lower than 40%, which would make the trick work as well. Either way, the simulation shows that Super Heavy can hover and that SpaceX intends to use it. Very much similar to what New Shepard from Blue Origin does before touching down. Hopefully with less sideway movement involved and a much larger booster, but at least comparable. As a final move, the chopsticks move inwards, maybe even slightly pushing the booster and grabbing it. That's it. Booster caught. Then the mentioned alignment system kicks in, centering the booster in the perfect position. Now, here's what I talked about in the beginning. There's one question I hear a lot from you. Why risk it? Why not just build legs and land it normally? Why risk all this in the first place, build a complicated Mechazilla and enter completely uncharted and new territory with the largest rocket ever built by trying to catch it out of mid air? It's a valid question. Legs would undoubtedly be easier. To answer the question, we have to look at the main goals of the Starship launch system. Full reusability and rapid reusability. As we discussed earlier in this episode, full reusability is hard to achieve with legs. It's the rocket doing the landing on its own. It's the leg taking the beating and they need to be checked and parts need to be replaced on every landing. So, getting rid of the legs all together is one possible solution. But in theory, you could come up with a leg design that doesn't need checking after every flight. A leg that doesn't need crush blocks or maintenance. So, what about the second reason? Rapid reusability. By landing the booster and later even the Starship itself on the chopsticks and catching it with Mechazilla, the Super Heavy booster and the Starship are instantly back in the launch process pipeline. Mechazilla can just lower it back down onto the orbital launch mount, making it ready for refueling. In theory, this way, it would be prepared for the next launch in an incredibly short amount of time. Now, this won't work with a prototype. But later on, if SpaceX actually manages to design a rocket booster that doesn't need maintenance after each flight, which is the current goal, it would speed up the launch cadence exactly to what Musk has been proposing for a long time. Three launches per day and per booster. Over and over again. At day and at night. So fast, that right now this sounds like science fiction. Working similar to a modern airliner. Landing, being refueled and launching again right after that last flight. That's the goal and Mechazilla might just be the missing element. If it works, that's the reason for taking the risk. Since there is no rocket in the world right now capable of performing such a fast launch cadence of multiple launches per day, SpaceX is forced to go new ways to achieve it. If it was possible with current designs, other launch providers would already do it. And if that doesn't satisfy your need for knowledge yet, maybe today's sponsor can help you out. If you've heard me talk about Brilliant before, then you know that it's a website and app built of the principle of active problem solving. Because it takes more to learn something than just watching it. To really learn something, you have to do it. 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