TThe SLS is designed to hoist the Orion Multi-purpose Crew Vehicle, along with science experiments and critical supplies, to Earth's orbit and, eventually, way beyond. See more space exploration pictures.

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Introduction to How the Space Launch System Will Work

On Sept. 14, 2011, NASA announced plans to construct and launch the most powerful rocket ever to match its might against Earth's gravity. In various forms, this blasting behemoth will constitute the driving force behind the American space program for the foreseeable future.

Rising from the ashes of the U.S. space shuttle program, which flew its final mission in July 2011, and its stillborn successor, the Constellation program, which was cancelled in February 2010, the Space Launch System (SLS) will inherit characteristics of both of its predecessors. Its technological lineage extends further down the family tree as well, to the former heavyweight champ, the Saturn V workhorse that launched Americans moonward more than 40 years ago.

The plan promises a launch vehicle made up of one part tried-and-true rocket know-how and one part state-of-the art technologies and materials. A dash of modularity will enable mission planners to tailor individual SLS builds to the demands of various missions, which NASA says will range from near-Earth milk runs to Mars exploration and beyond.

If you think that sounds like a lot to ask from a single system, you're not alone. The SLS has been mandated by Congress to serve so many masters in so many ways, it's a wonder it's not required to sing, dance and make great waffles to boot. This extraordinarily broad vision, combined with the underlying political dealing driving the system's design, has led critics to question whether the SLS can succeed at all.

In this article, we'll take a peek under the hood of this new heavy lifter. We'll also look at why some consider the SLS to be less of a phoenix and more of a turkey.

The Orion Multi-Purpose Crew Vehicle (MPCV)

Like the Apollo program's Command and Service Module, the Orion MPCV will serve as home, workspace and spaceship for its crew. The 16.5-foot (5-meter) wide, 25-ton (22.7-metric-ton) craft is larger, more versatile and more technologically advanced than its venerable predecessor, however, particularly with respect to computers, electronics, life support, propulsion and heat protection. Its crew module -- the only component that returns to Earth -- will squeeze two to six astronauts, with food and equipment, into 316 cubic feet (8.9 cubic meters) of habitable volume. That's one-third more elbow room than Apollo's crew compartment. Behind it, a service module will provide fuel and thrust, mount instruments and store air, water and cargo. Another callback to Apollo will crown the MPCV during launch: It's a small launch-abort system rocket (LAS) ready to boost the crew module to safety in an emergency. The LAS also protects the crew module from hazardous atmospheric loads and heating.

Under the Hood

Targeted for an unmanned test flight in 2017 around the moon, the first Space Launch System (SLS) will stand 320 feet (97.5 meters) and weigh in at 5.5 million pounds (2.5 million kilograms). Three space shuttle main engines (SSMEs) and two solid rocket boosters (SRBs), both inherited from the space shuttle program, will provide the 8.4 million pounds (3.8 million kilograms) of liftoff thrust necessary to propel the rocket's lower stage, interstage and six-person Orion Multi-Purpose Crew Vehicle (MPCV) into space. Imagine a tube taller than the Statue of Liberty, weighing as much as 24 fully loaded 747s and kicking out the horsepower equivalent of 13,400 locomotives, and you begin to get the picture.

At build-out, the SLS will tower an additional 80 feet (24 meters) and tip the scales at another 1 million pounds (450,000 kilograms). It will sport two additional RS-25 engines on the lowest stage, and a new upper stage will carry the J-2X, an updated version of the rocket engine that thrust Apollo's Saturn Vs into history. This taller, beefier SLS will boast rocket boosters that might burn solid or liquid fuel. Altogether, these lifters will churn out 1 million extra pounds (450,000 kilograms) of thrust, which will translate into 130 metric tons (286,000 pounds) of cargo lifting capacity -- nearly double that of the first SLS to be built, and 109 percent of the lift capacity of the Saturn V. Hauling all that extra cargo calls for some extra trunk space so, instead of an interstage, the late-model SLS will be spacious enough to carry nine school buses.

By design, the SLS will undergo component and equipment changes throughout its operational life span. In part, this is because it was conceived as a modular, multipurpose craft, reconfigurable according to mission requirements, but it's also because NASA is required by Congress to initially rely on shuttle vendors and incorporate leftover space shuttle components, such as the reusable SSMEs and SRBs. Later, they will be replaced by disposable engines and a five-stage booster rocket originally designed for the Constellation Program.

NASA plans to use the early, smaller version of the SLS to ferry cargo and astronauts to low-Earth orbit, primarily to service the International Space Station. Later configurations might support missions to space beyond Earth orbit, including missions to the asteroid belt or Mars.

Impressive? You bet, but as we'll see in the next section, when it comes to politics and multibillion-dollar spacecraft, the devil is in the details.

The Multi-Purpose Crew Vehicle being assembled and tested at Lockheed Martin's Vertical Testing Facility in Colorado

Photo courtesy Lockheed Martin/NASA

The Senate Launch System?

Someone once described a camel as a horse designed by committee. The Space Launch System is a camel designed by NASA to specifications set down by Congress, with legs from Canoga Park, Calif.; withers from Brigham City, Utah, Huntsville, Ala. and Titusville, Fla.; and a hump and a head from New Orleans.

That adds up to a lot of jobs for a lot of constituencies, but does it make for the best possible spacecraft?

From the beginning, the SLS has been as much a political football as a vehicle to the stars. Ever since the Obama administration announced in February 2010 that the Constellation Program was cancelled and would not be replaced for five years, the clock has been running in a scrimmage between the White House and Capitol Hill. Ultimately, the congressional blitz proved to be too much for the administration, and it punted -- first by agreeing to take the Orion crew capsule out of mothballs, then by proposing an Ares-inspired knockoff to serve as the lift vehicle.

Nor did the pressure end there. Instead of merely approving agency goals and funding, members of Congress went further, directing NASA on what kind of vehicle to design and even which parts and vendors to use. Moreover, their requirements even included contracts and contractors to be retained without a bidding process [source: Simberg, "3 Questions"; Simberg, "NASA's Space"]. Sen. Kay Bailey Hutchison, a Texas Republican and ranking member of the U.S. Senate Committee on Commerce, Science and Transportation, and Sen. Bill Nelson, a Florida Democrat and chairman of the commerce committee's science and space subcommittee, played influential roles in this process and in pressuring NASA to comply with it quickly. NASA Mission Control is located in Houston, Texas, and Florida is home to the agency's launch facilities.

Given the august body's heavy hand in the project, its derisive nickname, the Senate Launch System, was inevitable. 

Some critics have characterized the new program as a job-retention plan dressed up in a spacesuit. They point to how Sen. Richard Shelby -- ranking member of the NASA appropriation committee, whose home state of Alabama houses the Marshall Space Flight Center -- reversed his call for competitive bids on solid rocket booster contracts after two Huntsville-based firms began working on a competitive SRB design [source: Simberg, "3 Questions"].

Defenders of the Space Launch System have argued that it is a solid, versatile design; more lukewarm commentators have expressed relief that America is keeping its hand in the space game and tepid enthusiasm for the program's use of existing personnel and technologies, which some argue will keep costs down.

In response, critics point out that retaining a legacy workforce with long years of seniority and accrued benefits will in fact cost more than hiring new workers, citing a report by consulting agency Booz Allen Hamilton. The report also found that NASA's current budgetary data, while adequate for short-term planning, will poorly predict the project's long-term fiscal needs, casting a pall over a program on which NASA is expected to spend $18 billion over the next six years [source: Chang].

As we'll see in the next section, the program's lack of a clearly defined mission or timeline has only lent ammunition to that fusillade.

Will the SLS ever make it to the moon, Mars and more? We hope so.

Image courtesy NASA

The Great Leap ... Backward?

It remains too early in the game to predict the ultimate fate of the Space Launch System (SLS), but that has not stopped some commentators and politicos from prophesying doom for the program. They argue that the SLS, like Constellation before it, will shine brightly and briefly, sucking billions from the budget before collapsing under the accumulated mass of cost overruns, poor planning and rampant political maneuvering.

The primary argument for concern revolves around the lack of a solid plan. Currently, the early SLS is slated to make near-Earth orbital flights. Later missions have been vaguely described as targeting asteroids, Mars missions and "deep space" exploration; details, however, remain sketchy, and no explicit plans have been set out for fulfilling these disparate mission profiles. Nor is there a blueprint for how to connect them in a logical series of research and developmental steps.

Critics have further argued that the design specifications remain in such a state of flux that they endanger the mission timetable. The requirement of reusing shuttle engines and boosters, for example, means that initial SLS missions will require shuttlelike conditions, structures, equipment and designs for launch, which could conflict with the launch conditions required for later missions, implemented after the shuttle program spares run out and are replaced by newer designs.

In other words, early progress in the program could be in the wrong direction.

Then there are the missions. Although some balk at having to spend tens of millions of dollars per seat for American astronauts to "hitch a ride with the Russians" to the International Space Station (ISS), particularly in light of recent launch problems, the SLS might not be a better alternative [source: Simberg, "3 Questions"; Simberg, "NASA's Space"]. Commercial companies developing near-Earth orbital craft capable of servicing the ISS are well under way; NASA helps fund their development. Critics point out that, once active, these ships will run several times a year, whereas the SLS is predicted to launch once or twice annually, if that. Indeed, on Sept. 13, 2011, Rep. Dana Rohrabacher of California directed NASA to assess an alternative plan to the SLS, one involving parking a fuel depot in orbit to support commercial rockets.

With near-Earth missions in limbo, that leaves the SLS to carry out missions to asteroids or Mars, both prospects with iffy long-term political backing. Even assuming the program can survive the long years and political wrangling necessary to bring such missions to fruition, the question still remains: Would such projects have been better served by a more focused program -- or programs?

With too many cooks, fickle congressional and administration support, and no actual missions currently planned or funded, can NASA pull off the Space Launch System? If not, can the American space program withstand another false start? Only time will tell.

For now, it's comforting for space enthusiasts to know that the continuity of 40-plus years of astronautical engineering know-how will not be lost and that America has not entirely abjured its role in space.

Lots More Information

Related ArticlesMore Great LinksSources
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