October 28, 2005Moon, Mars, and beyond
Sessions today focused on solar-system exploration. H. A. Thronson from NASA discussed the possibility of using Lagrange point 1 (L1), between Earth and the Moon, as a staging area for future missions. The libration points are where the gravitational fields of Earth, Moon, and Sun are balanced, so anything you place there more or less stays put. L1 is five-sixths of the way directly from Earth to the Moon, where "you've climbed out of the Earth's gravitational well, but haven't yet descended into the Moon's gravitational well," Thronson explained.
The idea is to use L1 as a gas/depot station, human-tended but not permanently manned. Parts stored there could be assembled into a larger spacecraft to continue on to Mars, or a large astronomical telescope. Over time, this depot might grow into a multi-use facility with both government and commercial users, and perhaps even generate revenue.
James Head of Raytheon suggested an L1 depot could store robotic ISRU equipment. Such equipment could be deployed to intercept small asteroids that pass near Earth, to mine them for propellants and other useful materials for continuing on to Mars.
Others want to go directly to Mars rather than establishing way stations at L1 or on the Moon. Robert Zubrin of Pioneer Astronautics argued the most cost-effective approach to exploration would be to land in one spot and send out a hopping vehicle to visit other places. He proposed the "Gas Hopper," a craft that can either jump 25 miles (40 kilometers) from its takeoff spot or use wings and soar up to 125 miles (200 km) at a time.
He designed the propulsion system to be the simplest possible. In one tank, carbon dioxide is compressed from the thin martian atmosphere, which is 90-percent CO2
. In another tank, pellets of magnesium oxide or another material are heated (think of the hot rocks used in gas barbecue grills) to 1,292° F (700° C) — a temperature steel can easily withstand. When the hopper's ready to take off, the CO2
runs through the hot rocks, causing the gas to expand suddenly. The hot gas is directed out a steerable nozzle, pushing the craft off the surface and letting it soar until it literally runs out of gas.
Zubrin and his colleagues showed film clips of two prototypes they flew some 1,600 feet (488m) this summer in Colorado. (The clips are available here
— click on the Gas Hopper press release).
Once on Mars, both science and mining will call for drilling into the surface for water ice, titanium, and other resources. Jose Guerroro of Swales Aerospace showed photos and reported on his company's progress in designing an ultralow-power drill. It that takes less than 200 watts a day — less power than a kitchen microwave oven uses — to drill 65 feet (20m). At only a couple feet a day, the drill is slow, but this unhurried pace does not melt or alter the sample.
And what would we do with a sample? Mark Berggren of Pioneer Astronautics discussed using sulfuric acid to dissolve martian soils. This process is more efficient than crushing or heating a sample to extract oxygen, iron, and other desired materials useful for ISRU. Even the spent residue, when compacted, produces bricks strong enough to use for buildings.
The last hour of the meeting was a lively open-mike discussion about project priorities, incentives for economic returns, and potential funding sources. Most of the meeting's participants were convinced that returning to the Moon or getting to Mars is only 20-percent technology — the other 80 percent is political will. These goals require the willingness of NASA, private companies, the public, and worldwide governments to reduce or accept the inevitable risks of pioneering throughout the solar system.