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[science] Mars and beyond

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vincent    154
NASA sets its sights on Mars

HOUSTON ? NASA's new road map for the human exploration of space would land four astronauts on the moon by 2018 as the first step toward an eventual six-person voyage to Mars.

Pioneers would build a lunar outpost, most likely at the south pole, with living quarters, power plants and communication systems. Expeditions would scavenge the desolate landscape for precious supplies such as fuel and water.

Astronauts would roam the surface in high-tech dune buggies to search for answers to scientific riddles. The crews would blast off aboard rockets derived from the space-shuttle fleet and parachute back to Earth in capsules similar to those used during the Apollo program.

The assault on the moon would be a precursor to 500-day expeditions on Mars.

Those and other specifics of NASA's ambitious plans for a new era of human space travel are outlined in a set of internal briefing charts on the agency's recent Exploration Systems Architecture Study.Support from Bushb>

Some things are subject to change, and important decisions have yet to be made. But the study is the first detailed description of how NASA intends to accomplish the goals announced by President Bush in January 2004 of returning astronauts to the moon by 2020 to prepare for later missions to Mars.

So far, the program has considerable support from the White House and Congress, but to become a reality, it will have to withstand the test of time. The study estimates the program will cost about $217 billion through 2025.

All of the hardware needed for the Apollo moon landings from 1969 to 1972 reached orbit with a single launch of the giant Saturn 5 rocket. But because Saturn 5 production ended more than 30 years ago, NASA has been looking for new boosters.

Engineers debated for months whether to develop a heavy-lift rocket from parts of the shuttle or rely on improved versions of the Atlas and Delta boosters used by the Air Force to launch satellites. According to the study, they chose the shuttle-derived option because of lower cost and superior lifting ability.Lifting offb>

The hardware and cargo required for lunar missions would lift off aboard a 40-story colossus built around the shuttle's external fuel tank. This unmanned booster would be developed between 2010 and 2018.

Five of the shuttle's main engines and larger versions of its twin booster rockets would power the launcher. The projected price tag of $540 million per launch is comparable to the cost of a shuttle flight.

The giant booster would have a powerful new upper stage. This so-called Earth Departure Stage would be used to hurl spacecraft toward the moon. Also designed from the shuttle's fuel tank, it would be equipped with an upgraded pair of the same engines used on the Saturn 5's upper stages.

NASA has decided to launch future astronauts on moon and space-station missions aboard a separate rocket derived from another piece of shuttle hardware.

Starting in June 2011, astronauts would lift off to the station atop a modified version of the shuttle's pencil-shaped solid-rocket booster. The rocket's new second stage would be powered by one of the shuttle's main engines. The gap between the initial manned launches of that vehicle and the shuttle's planned retirement in 2010 was shortened from four years to one.

The $280 million missions would free NASA from having to depend solely on the Russians for station flights after the shuttle's retirement. The same rocket later would be used to launch crews into low Earth orbit to begin trips to the moon.

New spacecraft are being designed to ride atop the new rockets.

Engineers already are developing a cone-shaped Crew Exploration Vehicle, or CEV. Initial versions of the CEV would launch aboard the modified shuttle booster rocket and carry three-person crews to the space station a couple of times per year.

The ships also could be used to transport cargo to the outpost. Larger, future versions of the capsule would take four people to the moon and six-person crews to Mars.

In June, NASA awarded a pair of $28 million contracts to Lockheed Martin and a Northrop Grumman-Boeing team to come up with designs for the new ship. The agency will select one of the two proposals in March.

NASA managers plan to review the CEV's engineering design in July 2006 with the goal of having the spacecraft ready for a manned launch to the station in 2011. Having the CEV available as soon as possible could become critical if the White House rethinks the shuttle's 2010 retirement date because of continuing problems with hazardous launch debris during shuttle Discovery's liftoff July 26.

The CEV will be strikingly similar to the Apollo command module but larger. Astronauts on future lunar flights will have more than twice the room.

In another throwback to Apollo, the 12-ton capsule would be mated to a service module that provides power and propulsion during the journey to and from the moon. Crews returning home in the CEV would jettison the service module before making a fiery plunge through Earth's atmosphere and parachuting to the ground.

The capsule then would thump down on land as Russian missions did instead of splashing down in the Pacific Ocean as Apollo flights did.

In addition to the CEV, engineers have begun looking at designs for the lander that will carry astronauts from lunar orbit to the moon's surface and back. Development is scheduled to accelerate in 2010, with a spacecraft ready for flight by 2018.

The lander's design follows the same general concept as Apollo's. It has two basic parts. The bottom descent stage is a four-legged platform with rocket engines that lower the craft to the moon's surface. A detachable upper ascent stage serves as a crew compartment and launches the astronauts back to lunar orbit when their mission is complete.

The ascent stage's engines are designed to burn liquid-methane propellant. Small amounts of methane are thought to be present in Mars' atmosphere, creating the possibility that astronauts might be able to produce their own rocket fuel instead of carrying it with them.

The lander would remain on the lunar surface for about a week. An airlock would allow a crew of four astronauts to leave the ship for moonwalks.Combining strategiesb>

One of the great technical challenges of the early 1960s was how to design the Apollo moon landings. Engineers debated a number of ideas.

One approach, initially favored by rocket visionary Wernher von Braun, was called Earth Orbit Rendezvous. This method proposed launching several smaller rockets carrying the hardware needed for a lunar mission.

The pieces would be assembled in Earth orbit, and then the larger spacecraft would travel to the moon and back.

Apollo engineers ultimately decided on another approach known as Lunar Orbit Rendezvous. A single Saturn 5 booster launched all of the spacecraft needed for the mission. After the systems were checked out in Earth orbit, the rocket's third stage restarted to propel the mission to the moon.

Next, the Apollo command module and service module separated and docked with a lunar lander housed inside the third stage. Once in orbit around the moon, two astronauts piloted the lander to the surface. An ascent stage atop the lander launched back to lunar orbit, where it mated with the command module for the astronauts' return to Earth.

In recent months, NASA engineers have been debating some of the same issues their predecessors faced four decades ago. The result is a new blueprint similar to Apollo's but with features of von Braun's early Earth Orbit Rendezvous approach.

Future lunar missions would launch aboard two separate rockets. The giant new 40-story booster would carry the lunar lander into space atop the fuel-filled Earth Departure Stage. Next, the CEV and service module would lift off aboard the smaller, modified shuttle booster.

Once in low Earth orbit, the CEV would dock with the lunar lander. From there, the mission would be virtually identical to Apollo. The Earth Departure Stage would rocket the spacecraft toward lunar orbit. Four astronauts would descend to the surface aboard the lander. A week or so later, they would lift off from the moon and dock with the CEV, which would carry them back to Earth.

"You have to take the long view and not get yourself into a situation like before where we go to the moon and aren't positioned to build on it," said David Black, an astrophysicist and head of a research association that oversees the Lunar and Planetary Institute in Houston. "This approach makes a lot of sense if you are going on to Mars."Current plans call for a minimum of two lunar missions per year beginning in 2018.b>

Astronauts would conduct long-term research in several scientific disciplines, including astrobiology, geology, astronomy and physics. Some of the studies will gauge how the human body responds over time to weaker gravity, increased solar radiation and other space conditions.

Crews also would try to take advantage of any available resources on the moon and live off the land. The goal is to eventually develop a lunar base.Dress rehearsalb>

One of NASA's main reasons for returning astronauts to the moon and living there is to master the technologies and gain the experience needed for future human voyages to Mars. Detailed development of those expeditions is expected to begin about 2020, but the broad outlines already are starting to take shape.

Four or five launches with the giant heavy-lift boosters would carry into orbit the mission's spacecraft and hardware. Before the six-person crew lifts off, however, an outpost with living quarters, power, communications and a return ship would land on the Martian surface by remote control.

The astronauts' trip would take about six months each way. Once on Mars, the crew would spend about 14 months exploring large areas of the surface and doing research, including the search for evidence of past or present life. Astronauts would attempt to tap the Martian environment for oxygen and water, two essential supplies, and liquid oxygen and methane, the two propellants that will power the landing craft.NASA's ambitious plan faces several major technical and political challenges.b>

One is keeping astronauts healthy. For years, scientists have been concerned about exposure to harmful solar radiation in space, where Earth's atmosphere no longer provides a shield. Currently, there are no radiation guidelines for missions beyond Earth's orbit, although the National Council on Radiation Protection is developing some.Gauging the risksb>

The space agency assesses the lunar missions' overall risks as relatively small, mainly because of the use of proven systems and technology.

NASA estimates the chance of a failure derailing a mission is less than 6.3 percent, with the chance of the crew dying at 1.3 percent. In contrast, a May 1962 risk analysis before the Apollo program concluded the chance of losing astronauts during the first attempted lunar landing was 22 percent.

Political challenges here on Earth over the cost pose a different threat. The estimated $217 billion price tag is only $7 billion more than the projected budget for NASA's exploration office during the next 20 years.

The money crunch will be greatest during the next five years while the shuttle is still flying. But over time, adequate funding for the plan appears likely if the projects can stay within their budgets and schedules.

NASA's overall budget is expected to reach about $17 billion in 2006. If the agency averages only $20 billion annually during the next 20 years, it will receive a total of $400 billion. The estimated $217 billion exploration cost through 2025 represents 54 percent of that total. NASA already spends about half of its budget on human-spaceflight programs.

The plan also must survive three presidential elections and five new Congresses before astronauts again can walk on the moon.

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