Sea-Launched Space Booster Studies

 In the late 1950s, the idea of launching rockets directly out of the ocean emerged. Ignition of the first-stage engine(s) was to take place underwater. 
The US Navy initiated the HYDRA program to demonstrate the feasibility of launching rockets that were partially submerged and floating vertically in sea water. The 32-meter (105-foot)-tall solid propellant HYDRA-1 was launched in March 1960, directly out of the ocean off Point Mugu, California. The Navy conducted approximately 60 launches of rocket simulators and actual rockets over the course of the project, using mostly solid propellant propulsion systems. HYDRA validated the concept of launching directly from the sea, with the rocket's initial exhaust gasses being expelled directly into water.

 During the same time that the Navy was conducting the HYDRA tests, Aerojet-General Corporation accomplished a series of tests to study the feasibility of sea-launched liquid propellant rockets. The Aerojet effort, called the Sea Launch Program, was dubbed "SeaBee" because it used a modified Aerobee 100 sounding rocket for its test vehicle. Aerojet conducted a number of demonstrations of ocean launching techniques to evaluate handling, propellant servicing, checkout, and sea launch operations. Aerojet also evaluated recovery, refurbishment, and relaunch of the test vehicle, with an eye toward future reusable launch systems.

 Aerojet successfully launched the SeaBee test vehicle on 24 October 1961 from a floating position off Point Mugu. It reached an altitude of 1.5 kilometers (5,000 feet), deployed a parachute, and was safely recovered after a water landing. Having sustained no damage, the SeaBee was refurbished and relaunched on 2 November 1961. The success of SeaBee helped substantiate the concept of sea launch and recovery for a much larger launch vehicle proposal.

 Aerojet used some independent research and development funding in the early 1960s to explore various cost aspects of space launchers. Through these studies, the corporation developed a set of five design rules for low-cost launch vehicles. The low-cost booster must be big, simple, and reusable. 
Also, the design must not push for the absolute maximum reliability, and it must not push the state of the technological art.
 Aerojet combined data derived from the SeaBee program with the newly developed low-cost booster design rules to define a colossal launch vehicle. Called Sea Dragon, it was intended to support NASA's manned exploratory assault on Mars and interplanetary space (see Table 9).
 
The Sea Dragon was to be a simple, reusable launch vehicle. Like the SeaBee, it was to use a pressure-fed propulsion system; but it was scaled to represent perhaps the largest space booster ever conceived. It was to have a lift-off thrust of 356 million Newtons (80 million pounds) and a lift capacity to low earth orbit of 544,000 kilograms (1,200,000 pounds). The Sea Dragon was to be 168 meters (550 feet) tall and to have a diameter of 23 meters (75 feet). Construction and transportation of such a booster was more amenable to a shipyard than an aerospace factory, and the vehicle's simple steel design with water launch and recovery made shipyard manufacturing appropriate and practical.
 
Figure 7. The Sea Dragon launch vehicle concept,
illustrating the first stage recovery via water splashdown
 
Aerojet designed the Sea Dragon to have two stages. The first stage would use liquid oxygen and RP-1; the second stage, liquid oxygen and liquid hydrogen. Both stages would be pressure-fed, and both would use a single-engine thrust chamber. The first stage engine would be rated at 356 million Newtons (80 million pounds) of sea-level thrust--certainly the largest rocket engine ever seriously postulated.
 Aerojet settled on single-thrust chamber stages because their studies indicated it would be less expensive to develop and integrate single large engines than to develop and cluster sets of smaller engines. Also, analysis showed that even with near-exponential increases in the size of simple engines and airframes, there is only a linear increase in cost. The analysis results made a strong case for the economy of very large and simple boosters with large engines, and Sea Dragon was the consummate embodiment of this design philosophy.

 Sea Dragon was to be constructed-and transported to the launch location (at sea) in a manner that was closer to a seagoing tanker than an airplane. The vehicle would have been built horizontally in a commercial shipyard, then staged out of a US coastal site. It was to be fueled with RP-1 in a dry dock, then towed horizontally to the launch point.
 Upon its arrival, propellant transport ships would have loaded the vehicle with cryogenic propellants, and technicians would have flooded a ballast device to position the booster vertically. The booster would jettison the ballast at lift-off.
 
The first stage, which was to be recovered several hundred kilometers downrange, would use an inflated drag chute to decrease its water-impact velocity. The rigidity and strength of the heavy steel tankage, which was designed for the pressure-fed propulsion system, would have lent itself to surviving repeated water impacts with little damage.
 The second stage had an optional reusability design that would have employed retro-rockets, an ablative nosecap, and a drag-inducing device for controlled reentry to a point close to the refurbishment site.15
 
Cost estimates for using the Sea Dragon to place a payload in low earth orbit ranged from $59 per kilogram ($27 per pound) to $620 per kilogram ($282 per pound).16 The booster researchers were able to project these low costs because the booster had the benefit of a significant economy of size, it depended on shipyard-type (as opposed to aerospace) construction techniques, and it was reusable.
 
The Sea Dragon was designed prior to formal codification of the classical design-for-minimum-cost (DFMC) methodology by The Aerospace Corporation. 
Nevertheless, its design contained the essence of the DFMC philosophy and therefore represented the first detailed launch vehicle concept that was designed for minimum cost.
 
After Aerojet proposed the Sea Dragon concept, NASA's Marshall Space Flight Center contracted Space Technology Laboratories, Inc. (a subsidiary of TRW) to evaluate the proposal and re-accomplish the cost estimates. Space Technology Laboratories largely confirmed Aerojet's cost data and the soundness of the design.17 However, NASA's interest in the concept was primarily driven by the vehicle's massive lift capacity rather than its low cost.

 As the scope of NASA's interplanetary ambitions shrank, Sea Dragon was shelved and virtually forgotten.

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excerpt from the book "Great Mambo Chickens and the Transhuman Condition"
 The Sea Dragon was a launch vehicle of stupendous proportions that Truax had designed back when he was director of advanced development at Aerojet General. The best perk of that high office was the $1 million budget that he could spend any way he wanted to. Truax used it to test his pet theory that the *cost* of a rocket had nothing to do with how *big* the rocket was. You could make a given rocket just as big as you pleased and it would cost about the same as one that was about half the size, or smaller.

 This went against conventional wisdom and common sense, but at Aerojet Truax collected enough facts and figures to prove its truth beyond a doubt. Indeed, he'd been assembling the necessary data from the time he'd been in the navy, where he'd had access to all sorts of cost information.

 Take Agena versus Thor, for example. These two rockets were identical in every way: each had one engine, one set of propellant tanks, and so forth; the only significant difference between them was size. The Thor was far bigger than the Agena, but the surprise was that the *bigger* rocket had cost *less* to develop.

 "I was shocked to discover the Agena cost more than the Thor," Truax said later. "The Thor was between five and ten times as big! I said to myself, We've been tilting at windmills all this time! If all rockets cost the same to make, why try to improve the payload-to-weight ratio? If you want more payload, make the rocket bigger."

 The same anomaly cropped up again in the case of the two-stage Titan I launch vehicle: the upper stage was *smaller*, a miniature version of the lower stage, yet the smaller stage cost *more* to make.

 It seemed irrational, but all of it made sense once you went through the costs item by item. Engineering costs, for example, were the same no matter what the size of the rocket. "You do the same engineering for the two vehicles, only for the bigger rocket you put ten to the sixth after a given quantity rather than ten to the third or whatever," Truax said.

 The same was true for lab tests. "The cost of lab tests is a function of the size of your testing machine and the size of the sample you run tests on, not the size of the product."

 Ditto for documentation, spec sheets, manuals, and so forth. The cost here was a function of the *number* of parts and not the *size* of the parts.
 "There are absolutely no more documents associated with a big thing than a small thing, as long as you're talking about the same article."

 By this time Truax had accounted for a healthy chunk of the total cost of a given launch vehicle. About the only thing that *did* vary directly with a rocket's size was the cost of the raw materials that went into making it, but raw materials constituted only *2 percent* of the total cost of a rocket. "Two percent is almost insignificant!" he said. "And even with raw materials, if you buy a ton of it you get it at at lower unit price than if you buy a pound. And this is especially true of rocket propellants."

 So if all this was true, if engineering, lab tests, documentation and so forth didn't determine a launch vehicle's price tag, *what did*?
 Essentially, three things: parts count, design margins, and innovation.
 Other things being equal, the more parts a machine had, the more it was going to cost. The more you wanted it to approach perfection, the more expensive it would end up being. And finally, the newer and more pioneering the design, the more you'd end up paying for it.

 "We came up with a set of ground rules for designing a launch vehicle,"
 Truax said. "Make it big, make it simple, make it reusable. Don't push the state of the art, and don't make it any more reliable that it has to be. And *never* mix people and cargo, because the reliability requirements are worlds apart. For people you can have a very small vehicle on which you lavish all your attention; everything else is cargo, and for this all you need is a Big Dumb Booster."(emphasis mine -J.F.)

 Winged vs. Ballistic Recovery of Reusable Space Launch Vehicles
http://www.spacecoretech.org/coretech2000/Presentations/Systems/winged_vs_ballistic/Winged%20vs%20Ballistic%20Recovery%20of%20RLV.html
 or
http://makeashorterlink.com/?Y5C223BB5

 http://web.wt.net/~markgoll/rse10.htm
 The ultimate BDB was the Sea Dragon design of Aerojet. This was to be a rocket 550 ft tall, and 75 ft in diameter. The first stage had one engine, 80 million# thrust! The second stage was of course smaller, 14 million# thrust. It was to be launched from the ocean and put a really huge amount of payload into orbit. This super tanker sized rocket never found a market in the limited world of NASA.

http://astronautix.com/lvs/searagon.htm
http://astronautix.com/lvfam/truax.htm

Discussion thread
Of Sea Dragons and other such monsters
http://groups.google.com/group/sci.space.tech/browse_thread/thread/411e34416958131c/084ef6a2c134d515#084ef6a2c134d515