1966 Paper on Manned Mission to Eros Using Apollo-Derived Hardware

Selections from the Blog entry on a March 1966 paper by Eugene Smith on a manned mission to Eros...

German astronomer Gustav Witt discovered the asteroid Eros on August 13, 1898. Eros was both the first asteroid found to orbit entirely outside of the Asteroid Belt and the first known planet-crosser; its path crosses that of Mars. In March 1966, Eugene Smith, an engineer at Northrop Space Laboratories in Hawthorne, California, presented a paper on a piloted Eros flyby mission at the Third Space Congress in Cocoa, Florida. In it, he wrote that Eros exploration might help scientists understand Main Belt asteroids and small planetary moons (for example, the martian satellites Deimos and Phobos). He noted that Eros would pass within 14 million miles of Earth in January 1975.

At the time Smith presented this paper, NASA and its contractors studied piloted free-return Mars and Venus flyby missions based on Apollo technology. The first of these was expected to leave Earth in 1975. Among other expected benefits, a Mars flyby would provide interplanetary flight experience ahead of 1980s piloted Mars landings. Smith noted, however, that a Mars flyby mission would likely be so heavy that placing all of its components and propellants into space would need either a Saturn V rocket with a nuclear upper stage or multiple all-chemical Saturn Vs followed by assembly in Earth orbit. He called instead for a 1975 piloted Eros flyby that would provide experience applicable to Mars landings, yet could depart Earth on a single uprated Saturn V rocket.

Smith argued that "the value of the Eros mission to subsequent manned planetary flights having a higher level of difficulty and complexity is of no small consequence." He added that "interplanetary experience comes only from interplanetary missions: less difficult flights, such as that to Eros, could significantly enhance experience acquired in Earth orbital and lunar activities, and could thereby increase the probability of success for the missions to follow."

Smith's 527-day Eros flyby mission would begin with launch and Earth departure on May 3, 1974, at the opening of a 30-day launch window. Upon arrival in 100-nautical-mile parking orbit, the Eros Flyby Spacecraft Vehicle (EFSV) would comprise a 33.6-ton Eros Command Module/Eros Service Module (ECM/ESM), a 33.2-ton Eros Mission Module (EMM), and a 98.6-ton Apollo Saturn V S-IVB stage, for a total mass of 165.4 tons. The ECM would be based on the conical Apollo Command Module design.

At the time Smith presented his paper, the Apollo Saturn V had yet to fly, but NASA expected that it would be able to launch about 130 tons into 100-nautical-mile parking orbit. Smith cited studies that proposed boosting Saturn V launch capacity to 165 tons by uprating the four J2 engines in its S-II second stage. Alternately, the rocket's S-IC first stage could be fitted with twin 260-inch-diameter solid-propellant strap-on boosters so that it could launch about 215 tons. This, Smith wrote, would provide ample margin for EFSV weight growth during development.

Link: Blog entry on 1966 Paper on Eros Manned Mission