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Spaceships That Never Were
What Might Have Been
Since the inception of the U.S. space program there have been many novel launch vehicles and spaceships that were designed and seriously considered by NASA, but for one reason or another fell by the wayside. Whether they were scrapped due to lack of funds, lack of a perceived need, or simply because they lost out to other programs or vehicles that they were competing against, government archives are full of detailed plans for a fascinating variety of space hardware that was deemed feasible but never built. This article examines some of the more interesting might-have-beens.
Sea Dragon was a colossal launch vehicle designed by Aerojet, the company that built the Command/Service Module for the Apollo program. Sea Dragon dwarfs any other launch vehicle that has ever been seriously considered; while the mighty Saturn V could deliver 118 metric tons to low Earth orbit, Sea Dragon was designed for a payload capacity of over 550 metric tons - more than the entire mass of the International Space Station.
Although incredibly ambitious in terms of size and lifting power, Sea Dragon was also designed to be relatively inexpensive and simple to construct. It had only two stages, the first of which was fueled by liquid oxygen and kerosene, and the second with liquid oxygen and hydrogen. Liquid hydrogen and oxygen fuel was to be generated at sea by a support ship (most likely with a nuclear reactor) via electrolysis. Sea Dragon was designed to be built with "shipyard tolerances," making its construction more analogous to the creation of an ocean-going vessel than a high-tech rocket.
Since at 150 meters in height and 23 in diameter the rocket was far too large for any existing launch facility, Aerojet came up with the novel solution of launching from the ocean. Sea Dragon rockets were to be built at costal shipyard facilities. Once completed, Sea Dragon would be towed horizontally to a safe distance from shore and fueled. After fueling, water tanks at the base of the rocket would be flooded, causing the center of mass to shift and tilting the rocket vertically. Although the Sea Dragon concept might sound far-fetched, it was reviewed independently by the TRW Corporation, who issued a report agreeing that it was feasible.
By combining massive lifting power with a relatively simple design that was inexpensive to build and required minimal support facilities, it was estimated that the cost per kg launched into space with Sea Dragon would be 1/4 or less that of the Saturn V. NASA engineers envisioned the construction of truly massive space stations, or launching manned Mars missions with all the necessary hardware in a single payload. Unfortunately Sea Dragon fell victim to budget cuts in the late 1960s, and lack of a perceived need for such massive payloads has caused a general lack of interest in the project ever since.
The X-20 Dyna-Soar was a U.S. Air Force "space fighter" prototype project contracted to Boeing in the late 1950s and early 60s. Unlike the "capsule" designs that dominated manned space flight at the time, the X-20 was designed with wings so that it could be controlled by a pilot while in the atmosphere and land on conventional runways rather than relying on a parachute recovery system. It was to be launched into orbit on a Titan III booster, but incorporated its own rocket engine for maneuvering while in orbit.
The Air Force pinned its hopes for a manned military space program on the X-20, and planned to use it as a platform for the development of space weapon systems, military reconnaissance, and basic aeronautical research. In addition to potential combat in space, the Air Force envisioned using the X-20 to bomb ground targets. The X-20 would have had many advantages over both conventional fighter aircraft and unmanned ballistic missiles. Since it traveled in orbit, it would be almost impossible for a hostile country to shoot it down with conventional anti-aircraft weapons. It could also be used to attack mobile targets that couldn't be accurately targeted with pre-programmed intercontinental ballistic missiles. It would also have a human in control until the moment the bombs were released, allowing the pilot to make intelligent decisions or change plans in a way that wasn't possible with ballistic missiles. It was hoped that the design would eventually be used as the basis for a larger version of the craft that could be used to cheaply supply space stations.
Although the X-20 was in many ways much more sophisticated than the capsule designs of its time, the program was cancelled in 1963 due to lack of a clear need. The U.S. government was reluctant to simultaneously fund development of two separate manned space vehicles (the other being NASA's Gemini), especially since it seemed that a Gemini-based vehicle could fulfill many of the intended missions of the X-20. Also, many simply didn't believe that the X-20's advantages over more conventional, unmanned missiles or reconnaissance satellites were sufficient to justify the program's cost. The first prototype of the craft was partly assembled when the program was cancelled.
Although the X-20 never flew, the program provided a wealth of information about winged reentry vehicles that later proved useful in the design of the Shuttle orbiter.
The VentureStar program was an ambitious Lockheed Martin project to build the sort of spaceship that NASA has originally intended the Shuttle to be. It was to be a single-stage-to-orbit craft that had about the same cargo capacity as the Shuttle, but was fully reusable and required minimal maintenance between flights. Although NASA had originally dreamed of a fully reusable craft when designing the Shuttle in to 1970s, it proved impossible to build a fully reusable craft that met NASA's needs with the technology of the time. By the late 1990s Lockheed and NASA felt that advances in aeronautics and materials science should make such a craft possible. Chief among these advances were the development of new lightweight composite materials, a new thermal protection system that would be much safer and easier to maintain than the Shuttle's tile system, and "aerospike" engines that could efficiently operate at any altitude. With a fully reusable craft that didn't require extensive refurbishment between flights, it was estimated that launch costs could be reduced to about 1/10 of those associated with the shuttle.
Because the proposed craft incorporated so many new design elements, it was decided to build a test craft using the new composite materials, thermal protection system, and aerospike engine. Designated the X-33, this technology demonstrator was to be approximately 1/3 the size of the VentureStar.
Although the advanced aerospike engine was successfully tested, problems with the new composite materials cropped up as soon as construction of the craft began. Engineers had trouble making acceptably lightweight fuel tanks out of the composites that were strong enough to withstand the stresses of launch. The program fell behind schedule and over budget, and was cancelled in 2001. At the time of its cancellation, 85% of the prototype craft had been constructed. Over $1.5 billion was spent on the project.
No failed spacecraft has ever come as heartbreakingly close to success (but still failed) as the Soviet Buran Space Shuttle. The project was started in 1974 as the Soviet answer to the U.S. Shuttle program, and was intended to serve as U.S.S.R.'s principle scientific and military space vehicle into the 21st century.
Although the Buran looked very similar to the U.S. Shuttle - they both consisted of an orbiter mounted on the side of a large fuel tank, which was itself attached to smaller booster rockets - the overall design was substantially different. Unlike the U.S. Shuttle, which mounts its engines in the body of the orbiter, the Buran's engines were mounted under the central tank. The central rocket, called Energia, was a complete launch vehicle in it own right; the Buran orbiter itself had no major engines, and was essentially cargo that was carried up by the Energia rocket. Since the engines were not integrated into Buran, they could not be recovered and reused. Buran's 30 metric ton payload was also slightly higher than the U.S. Shuttle's 25 ton payload.
The U.S.S.R. conducted a successful test flight of an unmanned Buran prototype in 1988. Buran orbited the Earth twice and landed automatically. The prototype was only partly completed, and lacked a working life support system and cockpit controls
Despite its initial success, Buran was cancelled in 1993. The prototype that orbited the Earth twice in 1988 was destroyed in 2002 when its storage hanger collapsed.