Pathfinder to Blaze the Way to Missions in Deep Space

It is the year 2010 and after more than 14 months hurtling through the deep night of space, an American spaceship slams into the atmosphere of Mars at nearly 11,000 m.p.h.

“Entry interface plus 20 seconds,” the navigation officer says moments later, straining against the now-unfamiliar sensation of deceleration-induced weight. “Right down the pipe.”

High-speed photonic computers fire maneuvering jets in staccato bursts to make minute adjustments to the ship’s flight path as it plows down through the thin air, keeping the vehicle centered in a narrow corridor that means the difference between success and failure.

On the ground below, it is just after sunset. A spacesuited Soviet geologist, startled by a flash of light, pauses in his work to watch the meteoric streak of the American ship’s maneuver, called aerocapture.

The flight computers pull the ship out of its dive at an altitude of a little more than 30,000 feet above the red planet. A few minutes later, the craft pitches up and it soars back out of the atmosphere and into space.

By using the Martian atmosphere as a brake, the spaceship cuts its velocity about 40%, eliminating the need for a heavy rocket system to slow it down to an orbital speed of about 7,000 m.p.h.

“Houston, Columbia-2 here. That was some ride,” the commander radios to distant Earth after a small rocket firing puts the ship in a circular orbit.

Soon, the commander and her crew mates will leave the ship behind and descend to the ruddy surface to begin laying the groundwork for a permanent outpost on the red planet.

Although such a flight is the stuff of science fiction today, the National Aeronautics and Space Administration is working to develop the technology required to turn the dream into reality.

Called Project Pathfinder, the program has the blessing of the Reagan Administration to the tune of $100 million for fiscal 1989. Although NASA’s budget has not been finalized, the agency hopes that Congress and the next administration will continue funding for at least five years and possibly longer.

“Pathfinder looks toward exploration of the solar system and the technology that is needed for that,” said John Mankins, manager of the project at NASA headquarters in Washington.

“We’ll develop the critical technologies that we need if we are ever going to be able to implement any one of a variety of ambitious missions of exploration.”

On Feb. 11, President Reagan unveiled a new national space policy that calls for sweeping changes in the way NASA does business on the high frontier.

The President re-emphasized support for the agency’s embattled space station project and called for increased commercialization of space. He also endorsed Project Pathfinder.

Project to Provide Knowledge

A White House statement said the project “will give the United States know-how in critical areas” and “provide a base for wise decisions on long-term goals and missions.”

In his State of the Union address to Congress, Reagan said he is “deeply committed” to the “long-range goal of expanding human presence and activity beyond Earth orbit and into the solar system.”

“I invite Congress to join with me in endorsing and supporting this new long-term goal,” he wrote.

The only realistic targets for deep-space manned exploration are the moon and Mars, although many areas of research will benefit operations in Earth orbit as well.

Former astronaut Sally Ride submitted a report to NASA Administrator James Fletcher last year that called for a phased approach to deep-space exploration beginning with a manned outpost on the moon that ultimately could be used as a steppingstone to Mars.

Ride’s report and another by Reagan’s own National Commission on Space, submitted in 1986, concluded that a permanently manned space station was anessential first step on the road to manned deep-space voyages.

Although the new national space policy does not set concrete mission objectives beyond the space station program, Project Pathfinder will lay the groundwork for such flights should a future Administration give the go-ahead for a return to the moon or a flight to Mars.

“The question is not to go back to the moon for a quick sprint, which is what Apollo did,” Mankins said, referring to the Apollo program, which landed humans on the moon for the first time. “The mission scenarios involving the moon that Pathfinder looks at are long-term utilization.

“If we are going to send people to Mars, we are looking at a two- or three-year mission. That’s challenging. The longest mission the Soviets have done is, I think, one year in Earth orbit where, if anything went wrong, they were right next to home.”

Pathfinder is concerned with four general technology regimes: exploration, operations, life support and spacecraft propulsion and design.

James French, a former engineer at the Jet Propulsion Laboratory and an expert on the aerocapture technology required for a Mars mission, said he was pleased a project like Pathfinder is finally getting off the ground.

“The only thing I’m not happy about is that it was this year,” he said. “We should have done this 10 years ago.”

A major element of Pathfinder exploration technology involves refining concepts for systems that would be needed for unmanned planetary rovers that would precede manned expeditions.

Such automated, moving science labs would have to be able to cope with different terrains, avoid hazards and collect soil samples, all at the direction of on-board computers. Experiments on board would have to analyze those samples and relay the information to Earth.

“If we are going to really develop an understanding of the geology of Mars, its history, the possibility of whether or not there was ever liquid water, life at one point, we need to have a mobile laboratory,” Mankins said.

Part of the utility of Pathfinder, he said, is that the technology developed for a Mars rover would be applicable to other deep-space missions, such as exploration of moons around Jupiter or Saturn.

Optical Communications

Other areas of exploration technology targeted for refinement are new electrical power systems and optical communications gear that would use light rather than radio waves for high-capacity data transmissions.

In the operations arena, Pathfinder focuses on automated rendezvous and docking technology, space construction techniques, nuclear power systems and designs for pilot plants that could operate on the moon, for example, to extract oxygen from the lunar soil for use as rocket propellant.

“One of the key challenges is rendezvous and docking where the vehicles involved are remote or inaccessible to ground control,” Mankins said. “The Soviets have robotic docking (in Earth orbit), but they don’t do it (as far away as) Mars where the whole process happens autonomously.”

Life-Support Problems

A major element in Pathfinder life-support technology is work on closed-loop life-support systems and exploring ways to minimize the physical effects of prolonged exposure to weightlessness.

Current life-support systems, such as those used in the shuttle program, are “open” in that food and water are carried on-board and waste products are discarded. In a closed-loop system, air, water and liquid wastes could be recycled to some degree.

In a shuttle mission, which typically lasts a week or so, each crew member requires a daily ration of 60 pounds of food, water and oxygen and another 20 pounds of chemicals to keep the air pure, “for a total of 80 pounds of logistics per day for each astronaut,” Mankins said.

Lunar Outpost Cost-Effective

“Closing the loop on life support is going to be essential for truly deep-space piloted missions, like missions to Mars, and it’s going to make the idea of a lunar outpost or long-duration Earth orbiting operations cost-effective.”

Advanced new propulsion system technology also is required for deep-space missions and it is in this realm of Pathfinder that high-energy aerocapture is under study.

Without aerocapture, a spaceship would have to use rockets to slow down enough to go into orbit around Mars. The problem is compounded for the return to Earth when the initial velocity would be much higher because of the planet’s greater gravitational pull.

“The penalty for the heat shield and all the other stuff in an aerocapture vehicle is maybe 15% of the total mass” of the spaceship, French said. “If you did this with propulsion, you’d be lucky if you could do it for less than 50% and more likely, closer to 60% to 70%.”

Aerocapture, he said, effectively doubles the useful payload that can be delivered into orbit. But major technology questions must be answered before such systems will be practical.

“In aerocapture coming back from another planet like Mars, there are very high velocities involved,” Mankins said. “So there are key issues in terms of the heat shield, in terms of materials, the thermal protection system in general.”