 In 1963, the Aerojet Corporation presented to NASA a report detailing a rocket that was 400 feet long and was designed to launch out of the ocean vertically and could put a payload totaling 1.1 million pounds into low Earth orbit. Let's meet the unrealized Sea Dragon. Before we get into the details of Sea Dragon, let's put it into context against a few of its contemporaries, namely what the Soviet Union and the United States were launching at the time. The Aerojet Report was published in 1963. At the time, the U.S. was using the Atlas-D version of the Atlas ballistic missile to launch Mercury missions into orbit. In the Soviet Union, variations of the R7 rocket were launching the Voskhod missions into space. Both of these rockets stood about 100 feet and could put no more than about 3,000 pounds into low Earth orbit. Then comes along the Sea Dragon. Not only is it four times taller than either of these rockets, it can put so much more payload into low Earth orbit, 3,000 pounds versus 1.1 million pounds. And then there's the fact that Sea Dragon launches vertically out of the water as opposed to off a launch pad on the ground. And the final thing that makes Sea Dragon an incredible rocket of the early 1960s, it was designed to be almost entirely reusable, whereas Atlas and R7 were both expendable. The Sea Dragon was a two-stage rocket and each stage only had one engine. This was an attempt to make it simpler. The simpler the rocket, the fewer fail points, and the more likely it is to work beautifully. There was an interstage between the first and second stage, as well as one between the second stage and the payload stage. At the very top of the rocket would be an Apollo-style spacecraft, either an Apollo command service module or, if the mission was simple enough, a Mercury or Gemini-style spacecraft. The guidance and navigation and control for the entire mission would come from that spacecraft, the NASA heritage one. That's because it already existed, so why not make use of what NASA was already developing? It was also a way to have the Sea Dragon potentially double as a manned launch vehicle, not just for unmanned cargo. The Sea Dragon was designed to be built using classic shipbuilding methods, after all for Aerojet. If submarines could exist underwater for months at a time with complex electronics and even life support systems on board, why could the same methods not apply to a giant rocket? So the Sea Dragon would be constructed either at specially designed facilities for things that didn't yet exist or in existing dry docks for the parts that were a little bit easier to build, like the fuselage. Then the rocket would be constructed in a specially dredged lagoon near Cape Canaveral. This would allow technicians to actually mate the rocket vertically instead of horizontally like was done in the VAB for the Saturn V. It was a simple matter of keeping all exposed components above the waterline, rotating the rocket as need be to access certain components. The lagoon was also designed to give technicians calm waters in which to work, which meant that most of the pre-launch checkouts could be done in this lagoon with the rocket horizontal. It could also be fueled while floating at sea in these controlled waters. Once the rocket was completely mated, the portions were checked out and everything was ready to go, it would be towed out to its launch location, some 40 miles off the coast of Florida. At that point, the ballast unit would come into play to help upright the rocket. The ballast unit would be filled with fluid to kill its buoyancy. And by virtue of sinking, because it would weigh some million pounds on its own, it would move the rocket from its horizontal position into an upright position. This would be the point of highest stress on the rocket. Not only would it be dealing with mild waves, the force of moving it upright would put so much stress on the body of the rocket that it risked buckling. But the Sea Dragon's own construction was designed to counteract that. Both the first and second stages of the rockets used pressure-fed engines. That meant that the fuel and oxidizer tanks in both stages would be pressurized with a third gas to force the propellant and the oxidizer into the combustion chamber for a stronger reaction. It also meant that because the tanks were pressurized, they were more rigid. That meant that not only while the rocket was being towed and popped upright, the sheer structure of the rocket helped with its rigidity. But the internal pressurization helped keep it that much more rigid so that it could resist any kind of buckling from being uprighted. Once the final checks were done, the cape would sign off on launch, and the actual launch sequence would be ordered by a tugboat standing nearby, or floating nearby, the launch location. The ballast unit surrounding the first-stage engine would create a sort of casing. Now, of course, the engine was still exposed to water. It was going to start launching under water regardless. But the ballast unit sort of protected it from heavy flows of either currents or waves or anything that might hit it and jostled the engine at the moment of ignition such that it would destroy the launch. Four auxiliary engines on the second stage would fire just a fraction of a second before the main engine started. Then the rocket would fly smoothly out of the water, separating from the ballast unit which would start to sink. And from there, the launch was fairly standard. After 81 seconds of flight, the rocket would be at an altitude of about 125,000 feet. At that stage, the first engine would cut out, and the second stage would ignite almost immediately such that there was very little coasting. The second stage main engine, as well as those four auxiliary engines, would burn for an additional 260 seconds. Once the second stage main engine cut off at about 911,000 feet, or 150 nautical miles, it all came down to those four auxiliary engines. They would fire for an additional 22.4 minutes. This was a low thrust period, but once sufficient enough to give the rocket payload just that little bit of extra velocity it needed to get into orbit. The final orbit would be about 300 nautical miles. The payload that would reach orbit was initially conceived as being a giant tank of liquid hydrogen, something that could refuel deep-space missions before leaving the Earth. As for recovery, the ballast unit would sink initially, but inflatable flotation bags would bring it back up to the surface. Then it could be towed back to the assembly lagoon where it could be mated to another rocket. The first and second stages were both recovered at first using just simple aerodynamic braking as they fell through the upper atmosphere. But the active stage of recovery would be using an aerodynamic deceleration device. This decelerator was a reliable and very easy system. It was a large conical flare, 300 feet in diameter, that could be pressurized with the same pressurizing gas as was used in the pressure-fed engines for each stage. This also ensured that both stages would hit the water at the correct nose-down orientation, a way that would minimize the forces and stresses on the body such that it could be refurbished easily and reused, as opposed to building a new one. After the first and second stages both splashed down, they would be recovered and towed back to the assembly lagoon. There they would be refurbished, and any parts that needed replacing could be replaced. But at the end of the day, most of the rocket could be just refurbished, mated together again in that lagoon, and used again on another Sea Dragon launch. As Aerojet noted in its 1963 report, the Sea Dragon definitely represented a massive leap in technology, but it wasn't one that was completely impossible. Every challenge with the Sea Dragon was actually just an engineering challenge, and engineering challenges could be solved. And it wasn't even that expensive. Aerojet predicted the cost would be about $2.8 billion over about six years to have the system operational. It all came down to the cost saved in reusing most of the rocket parts. But as we know, the Sea Dragon never flew. It was just not something NASA could work into its Apollo decade. Getting to the moon was just more important than building a 400 foot long rocket that would just put fuel into orbit. But it's a pretty compelling idea, so it might be something that we could see pop up one of these days. That is the absolute cold notes version of the Sea Dragon. There is so much more to the story, including the intricacies of how it was built, the things like fuels it would use, and pressurizing gases, and all the decisions that led to the aerodynamic decelerator. All of that is in my companion blog post over at Discover. So be sure to check that out if you want an even deeper dive into the Sea Dragon. But in the meantime, are there other early rocket concepts you've heard of that you'd like to see a video about? Because I love digging into these things for you guys. Let me know all of those things in the comment section below. And of course, questions you might have about the Sea Dragon, other big rockets, or anything old timey space. 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