This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

06 May 2009

Recap of 1996 Paper from E. Smith: "A Manned Flyby Mission to Eros"

"A Manned Flyby Mission to Eros"
Eugene Smith, March 1966, Northrop Space Laboratories (Hawthorne, California), Presented at the Third Space Congress in Cocoa, Florida.

A manned flyby mission to Eros (Technical feasibility of 1975 manned flyby mission to Eros and examination of lesser bodies of solar system), SMITH, E A, THE CHALLENGE OF SPACE, PROCEEDINGS OF THE THIRD SPACE CONGRESS, COCOA BEACH, FLA ; United States; 7-10 Mar. 1966. pp. 137-155. 1966

From David S. F. Portree's Beyond Apollo Blog:

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.

Upon arrival in parking orbit, the six-man crew in the ECM/ESM would check out the EFSV's systems. Assuming that all appeared normal, they would ignite the S-IVB stage engine at perigee to raise the ESFV's apogee and gain over 90% of the velocity needed to depart Earth orbit for Eros. The crew would then separate the ECM/ESM, turn it end for end, and dock with the EMM.

After jettisoning the spent S-IVB, they would transfer to the EMM, their main living and working space during the Eros flyby mission. They would deploy the EMM's eight disk-shaped solar panels, a steerable "sensor turret," a large dish antenna, and a "support structure" for shielding the ECM from sunlight and micrometeroids. After linking the EMM and ECM/ESM electrical and control systems, they would check out all systems a second time.

If the EFSV failed checkout, the astronauts could abort their mission by separating from the EMM in the ECM/ESM and firing the ESM's twin liquid hydrogen/liquid oxygen-fueled RL-10A-3 main engines at perigee to reduce speed so they could reenter Earth's atmosphere in the ECM. If the spacecraft checked out, however, the astronauts would fire the ESM engines at perigee to add enough velocity to place the EFSV on course for Eros.

On January 18, 1975, the astronauts would begin tracking Eros using radar, a five-foot-long reflecting telescope with a 30-inch primary mirror, and other instruments mounted in the EMM's sensor turret. On January 23, 1975, they would fire the ESM engines to ensure an Eros close-approach distance of about 50 miles and begin gathering Eros science data. About eight hours before closest approach, the astronauts would catapult a 200-pound automated probe toward the asteroid. The EMM's dish antenna would relay to Earth data from the probe's TV camera and other instruments.

Closest approach to Eros would occur about 14 million miles from Earth on January 28. The piloted spacecraft would spend about 90 seconds within 200 miles of asteroid's sunlit side and about 30 seconds within 100 miles. On January 30, 1975, the crew would end Eros tracking and fire the ESM engines to correct course deviations imparted by the January 23 maneuver, the automated probe launch, and the weak tug of Eros' gravity.

The astronauts would load the ECM with scientific data and check out its systems on October 10, 1975. On October 12, they would abandon the EMM and use the ESM engines to place the ECM on course for Earth atmosphere reentry. They would then jettison the ESM, reenter Earth's atmosphere at about 40,000 feet per second, and descend to the surface on parachutes.

Congress killed NASA's plans for piloted Mars and Venus flyby missions in August 1967. Smith's Eros flyby proposal received little attention. The only U.S. piloted mission of 1975 was the Apollo-Soyuz Test Project, which saw the final Apollo spacecraft dock with the Soviet Soyuz 19 spacecraft in low-Earth orbit. When NASA at last explored a near-Earth asteroid, it explored Eros. The $112-million Near-Earth Asteroid Rendezvous (NEAR) mission - the first mission in NASA's new low-cost Discovery Program - left Earth on February 17, 1996, more than 20 years after the planned launch date of Smith's piloted Eros flyby.

On December 20, 1998, NEAR failed to enter Eros orbit because its computer aborted a crucial engine burn. Three days later, after some quick reprogramming, NEAR flew past the 22-mile-long, 13-mile-wide asteroid at a distance of 2375 miles, returning 222 images.

On February 14, 2000, after an additional revolution about the Sun, NEAR at last orbited its target. NASA renamed the spacecraft NEAR Shoemaker in March 2000 to commemorate renowned planetary geologist and comet discoverer Eugene Shoemaker, who had died in a car crash in Australia in 1997. In the year that followed, the spacecraft radioed to Earth more than 160,000 close-up images of Eros.

Though designed as an orbiter, NEAR Shoemaker succeeded in landing on Eros on February 12, 2001. It returned gamma-ray spectrometry data from the asteroid's surface until February 28, 2001.

"A Manned Flyby Mission to Eros," Eugene A. Smith, Proceedings of the Third Space Congress, "The Challenge of Space," pp. 137-155; paper presented at the Third Space Congress in Cocoa Beach, Florida, March 7-10, 1966.

Link: Beyondapollo Blog Entry by David S. F. Portree

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