[BLOG-LIKE POSTING] Let's go to Eros

[rfmcdonald]

In his recent announcement on the United States' retooled space program, President Obama announced that the United States would send a manned mission to a near-Earth asteroid by 2025. 80 Beats' Andrew Mosemen pointed out that such a mission would be considerably more difficult than a lunar mission, although scientifically rewarding.

One week ago today, in response to heavy criticism for killing the Constellation program begun under his predecessor, President Obama presented his revised vision for NASA: To build a new heavy lift spacecraft that will go beyond low Earth orbit and land on an asteroid by around 2025. This goal is far more ambitious than going back to the moon. Space experts say such a voyage could take several months longer than a journey to the moon and entail far greater dangers. “It is really the hardest thing we can do,” NASA Administrator Charles Bolden said [AP].

NASA doesn’t know which of the nearby asteroids it might pick for a visit, but the main candidates are around 5 million miles from Earth. The moon, by contrast, is a little less than a quarter-million miles away. The asteroids are about a quarter-mile across; the moon is more than 2,000 miles in diameter. And a trip to an asteroid could take 200 days, as opposed to the Apollo 11 lunar round-trip, which required little more than a week.That means NASA may have to devise new radiation shields and life-support systems for the asteroid-bound astronauts.

Once you get there, it’s no picnic either. You can’t actually land on an asteroid because it has so little gravity. Astronauts would have to somehow tether themselves to the rock to keep from floating away. (DISCOVER blogger Phil Plait cheered this bit of science fact in the 1998 disaster movie Deep Impact, in which the heroes encounter this problem while visiting a comet.)

Despite the challenge, there are several great reasons to go. The chemical composition of asteroids can give scientists clues about era of the planets’ formation, roughly four and a half billion years ago. And on a practical level, an asteroid mission would be a Mars training ground, given the distance and alien locale. “If humans can’t make it to near-Earth objects, they can’t make it to Mars,” said MIT astronautics professor Ed Crawley [AP].

The idea of sending a manned mission to a near-Earth asteroid--one of a population of asteroids orbiting well inside the asteroid belt, closed to the inner terrestrial planets--has been alive for decades, with the relatively large, well-studied, and culturally prominent asteroid 433 Eros frequently named as a possible target. Subject of a recent NASA feasibility study, a 1966 conference paper proposed that NASA use retooled Saturn rockets to send a manned mission to Eros in 1975, when the asteroid would be only 14 million miles away.

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.

[. . .]

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.

This didn't happen, obviously. Equally obviously, it's a nice idea. If something like this Eros expedition is made with early 21st century technology, I'll be happy.