The Sea Dragon was a 1962 conceptualized design study for a reusable two-stage sea-launched orbital super heavy-lift launch vehicle. The project was led by Robert Truax while working at Aerojet, one of several designs he created intended to be launched by floating the rocket in the ocean. Although there was some interest at both NASA and Todd Shipyards, the project was not implemented.

With dimensions of long and in diameter, Sea Dragon would have been the largest rocket ever built. It is comparable to other unbuilt concepts such as Convair's Nexus and Super Nexus, Boeing's Large Multipurpose Launch Vehicle, Phillip Bono's series of reusable single stage launch vehicles, and various NOVA Post-Saturn launch vehicles.

Design

Truax's basic idea was to produce a low-cost heavy launcher, a concept now called "big dumb booster." To lower the cost of operation, the rocket itself was launched from the ocean and constructed in a shipyard with more standard materials. A large ballast tank system attached to the bottom of the first-stage engine bell was used to orient the rocket vertically for launch. In this orientation the payload at the top of the second stage was just above the waterline, making it easy to access. Truax had already experimented with this basic system in the Sea Bee and Sea Horse. To lower the cost of the rocket, he intended it to be built of inexpensive materials, specifically steel sheeting. The rocket would be built at a sea-side shipbuilder and towed to sea for launch. It would use wide engineering margins with strong simple materials to further enhance reliability and reduce cost and complexity. The system would be at least partially reusable with passive reentry and recovery of rocket sections for refurbishment and relaunch.

The first stage was to be powered by a single pressure-fed thrust engine burning RP-1 and LOX (liquid oxygen). The tank pressure was for the RP-1 and for the LOX, providing a chamber pressure of at liftoff. The first stage would also be equipped with an asbestos-based recovery heat shield for reuse of the vehicle. would have created an extremely challenging sonic and vibrational environment for a traditional land-based launch pad. This issue was common point of issue for vehicles around the scale of Sea Dragon. One solution, proposed by Philip Bono, was the “water-filled acoustic limiter,” which consisted of a parabolic dish filled with water installed beneath the launchpad. However, the size and supporting infrastructure required for such a system would have significantly increased launchpad construction costs. Truax’s design team avoided these construction costs by adopting the ocean-launch concept.

The second stage was equipped with a single extremely large pressure-fed hydrolox engine with a thrust of , fed at a constant lower pressure of . At the end of the entire 260s burn, the second stage would be at in altitude and downrange. To improve second stage engine performance, the engine featured an expanding engine bell which covered most of the first stage tankage, acting as an aeroshell for the first stage during ascent. During the events of staging, this expandable nozzle would go from a linear to a more conical shape, improving the second stage's expansion ratio.

To provide attitude stabilization, the second stage was also equipped with four auxiliary hydrolox engines, each producing of thrust. These engines served as the vehicle's primary Thrust Vector Control (TVC) system; they provided roll control during the first-stage burn and full attitude control (pitch, yaw, and roll) for the second stage. To ensure reliability, these auxiliary engines were ignited and monitored on the ocean surface shortly before the first-stage main engine start. They would remain active for a total of 1340 seconds, continuing to burn after the second stage main engine shutdown to provide the final velocity increment required for orbital injection., for comparison the Falcon 9 is estimated to cost ~$3,100 per kg in 2025.) TRW (Space Technology Laboratories, Inc.) conducted a program review and validated the design and its expected costs. However, budget pressures led to the closing of the Future Projects Branch, ending work on the super-heavy launchers for a proposed crewed mission to Mars.

alt=Principle of the Sea Dragon rocket|center|thumb|800x800px|Principle of the Sea Dragon (Scale is incorrect)

thumb|Composite of two NASA technical drawings, of the Saturn V rocket and the proposed Sea Dragon rocket, to the same scale. The second stage of Saturn V would fit inside the first-stage engine and nozzle of the Sea Dragon.

thumb|A composite visualization of the Sea Dragon standing in front of the NASA [[Vehicle Assembly Building for scale.]]

Sea Dragon in fiction

The Sea Dragon appears in the first-season finale of the 2019 Apple TV+ series For All Mankind, set in an alternate history timeline in which the 1960s-era space race did not end. In a scene set in 1983, a Sea Dragon is depicted launching from the Pacific Ocean on live television. Dialogue indicates that a carrier task force is present as a security measure, and that the ocean launch is intended as a safety measure because the payload includes plutonium.

See also

  • Aquarius (rocket)

Notes

References

Further reading

  • Astronautix.com, Sea Dragon
  • Truax Engineering Multimedia Archive
  • Sea Dragon Concept Volume 1 (Summary), LRP 297 (NASA-CR-52817), 1963-01-28.
  • Sea Dragon Concept Volume 2, LRP 297, 1963-02-12.
  • Sea Dragon Concept Volume 3 (Preliminary program plan), LRP 297 (NASA-CR-51034), 1963-02-12.
  • YouTube Channel Link: For All Mankind s01e10 post-credits scene. The Sea Dragon launch
  • Encyclopedia Astronautica, Sea Dragon
  • Big Dumb Rockets
  • YouTube, Sea Dragon - 8.14 TMRO - Interview show about "Sea Dragon"
  • Search "Sea Dragon Concept" at the NASA Technical Report Server to read the unclassified design study:
  • Sea Dragon Concept Volume 1 (Summary), LRP 297 (NASA-CR-52817), 1963-01-28.
  • Sea Dragon Concept Volume 3 (Preliminary program plan), LRP 297 (NASA-CR-51034), 1963-02-12.
  • Aerospace Projects Review blog about Boeing's Large Modular Launch Vehicle https://www.aerospaceprojectsreview.com/blog/?p=3774