A New Mission for NASA: Avert Asteriod Impacts


By Chris Vuille, Associate Professor of Physical Sciences

Chris Vuille The recent Columbia disaster brought home once again just how dangerous space flight can be. Most of all, the disaster raises questions about the future of manned space flight. Sending humans into space is dangerous and expensive, and many wonder whether it's worth the cost and whether there might be better ways of getting there.

The space program was initially driven by competition with the Soviet Union. That nation's opposing political philosophy, threatening posture, and nuclear arsenal greatly motivated America's drive to space. After the Soviet program and threat faltered, though, America's own program languished for three decades, in search of a mission.

Today there is a threat far greater than that posed by the former Soviet Union.

Asteroids scattered throughout the solar system regularly cross the orbit of Earth. In the past century alone, there have been some near misses by asteroids large enough to cause damage far greater than a nuclear exchange between superpowers. An asteroid only one kilometer across would cause widespread destruction, damage Earth's thin biosphere, and drive many species to extinction.

While extinction events happen only once every 60 million years, smaller strikes are thought to happen every few thousand years.

In 1908, a boulder exploded in the atmosphere over Tunguska, Siberia, with the power of a 15-megaton bomb. Had it hit northern Europe, millions of people would have died. In 1989, the Earth was nearly struck by an asteroid about 300 meters across. The impact would have released energy equal to 100,000 Hiroshima explosions.

A major disaster caused by a collision with an asteroid or comet appears to be just a matter of time. However, if humanity spreads out to different worlds, a cataclysm on Earth would not signal the end of our kind and we'd be in a better position to detect and avert such disasters.

For this reason, manned missions in space must continue.

In addition to securing our future, it's in our nature to explore and expand, uncover new resources, and gain new knowledge. What goals, then, should we strive for, and how best can we realize them?

At enormous cost, the international community is putting up a space station. Most of the science planned for it, however, could be done better by robotic craft. Furthermore, supplies must be periodically boosted up out of Earth's deep gravity well at great expense. The Moon, on the other hand, is a giant natural space station, loaded with resources. And beyond that is Mars, with an atmosphere of carbon dioxide and plenty of other resources, including water a few meters beneath the surface. It makes sense to establish habitable, self-sufficient outposts on the Moon and Mars.

To do so, however, will require major changes in our space launch systems. We need a heavy-lift booster like the Saturn V. We also need nuclear thermal rockets, which have been around since the 1960s. These rockets are safer and more powerful than chemical rockets and could be fueled with virtually any gas or fluid, even water.

The space shuttle, however, has no role in this future expansion. It should never fly again.

The shuttle, designed to reduce the cost of reaching space, now costs more to launch than the Saturn V, in constant dollars, and has far less capability. The Saturn V was capable of sending 100 metric tons to low-Earth orbit, 60 tons to the Moon, 30 tons to Mars, and 10 tons to Pluto. The space shuttle, by contrast, can put only 30 tons in low-Earth orbit. It will take about 50 launches of the shuttle and an enormous amount of in-orbit assembly to put up the International Space Station. Using the Saturn V, the station could have been assembled on the ground and put in orbit with two launches.

Furthermore, the shuttle's segmented rocket boosters have always been a problem, as are the tiles and the lack of an effective emergency escape system. Finally, astronauts shouldn't have to rely on 20-year-old technology and refurbished parts. It's too dangerous.

Space exploration can and must happen. The threat posed by asteroids and comets is real, and only our expansion into space can reduce it. And beyond ensuring the safety of our species, other worlds and a wealth of knowledge await us. This vision - the vision of the Challenger and Columbia astronauts - will secure the future of humankind.

The views expressed in "Perspectives" are those of the writer and not necessarily Embry-Riddle's.