Less than a year ago, the final report of NASA‘s sweeping Exploration Systems Architecture study squashed the idea of using technology developed under the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) program on the agency’s moon/Mars Cargo Launch Vehicle.

"No RS-68-powered variant of an EELV-derived heavy-lift cargo vehicle demonstrated the capability to meet the lunar lift requirements without a new upper stage and either new large liquid strap-on boosters or shuttle RSRBs [reusable solid rocket boosters]," the report said. "The considerable additional cost, complexity and development risk were judged to be unfavorable, eliminating RS-68 powered" vehicles from the competition.

In May, NASA reversed course, announcing it was replacing the moon-bound heavy lift launch vehicle’s spacer shuttle-derived first-stage engine with the Pratt & Whitney Rocketdyne RS-68. The engine was developed under the EELV program to power Boeing‘s Delta 4 family of rockets. "Recent studies examining life-cycle cost showed the RS- 68 is best suited for NASA’s heavy-lift cargo requirements," NASA said May 18.

The switch was well received by NASA observers who have been advocating that the agency abandon the shuttle-derivative idea in favor of EELV technology. NASA already has made similar changes in other areas.

The Crew Launch Vehicle second stage originally was to be based on the space shuttle main engine but has been replaced by the J-2X, a new version of the J-2 used in the Saturn 5 third stage. Meanwhile, the heavy lift launch vehicle first stage is no longer a stretched space shuttle external tank. In order to provide enough fuel to power five RS-68 engines, a new tank will have to be developed.

With EELV technology becoming a larger part of NASA’s mission to again send humans beyond low-Earth orbit, some EELV proponents are increasing their push to have NASA qualify the vehicles to launch humans into space.

NASA’s current plans calls for using a five-segment solid rocket booster, built by ATK Thiokol and derived from the already man-rated four-segment space shuttle booster. The booster would give the crew vehicle the capability to deliver 55,000 pounds to low-Earth orbit when combined with the J-2X, the company said.

The Delta 4 can carry more than 50,000 pounds to orbit, but it would cost time and money to man-rate the rocket, which was developed as an unmanned heavy lift vehicles to loft satellites into various orbits.

As a vehicle developed to put unmanned payloads into orbit, the flight profiles of the EELV rockets are too rough for human passengers. "Both [Lockheed Martin] Atlas and Delta single-engine upper stages fly highly lofted trajectories, which can produce high deceleration loads on the crew during the abort and in some cases exceed crew load limits," the Exploration Systems Architecture study said. "Depressing the trajectories flown by these vehicles will require extra stage thrust to bring peak altitudes down to levels that reduce crew loads enough to have sufficient margins for off-nominal conditions."

ATK spokesperson George Torres said, "The flight profile is so dramatically different on the two types of vehicles [the EELVs and the solid rocket boosters] that it raises safety issues for the crew."

NASA previously has taken unmanned rockets and developed them for crew use, such as with the Redstone, Atlas and Titan 2 launchers used in the agency’s early days of manned space, flight but the process to qualify EELV rockets for such duty would be more complicated, said Jeff Foust, launch industry analyst for Futron Corp. "Because of an increased aversion to risk, man-rating today is a lot different than it was in the 1960s," he said. Man-rating today can mean "being able to trace components right back to who made the metal they were made of."

In a written statement, Boeing said the RS-68 "is reliable and capable of being adapted to a variety of payload requirements. The Pratt & Whitney Rocketdyne RS-68 engine originally developed for the Delta IV and the EELV program has been selected by NASA to power the heavy-lift Cargo Launch Vehicle that will support lunar exploration efforts in tandem with the Crew Exploration Vehicle, demonstrating synergies between the programs. Should NASA determine there is value in exploring the use of the Delta IV launch vehicle family for its exploration initiatives, Boeing would be proud to support these efforts."

The biggest obstacle Boeing must overcome is the desire to keep the space shuttle production lines open after the vehicle is retired, said John Pike, director of Globalsecurity.org. "If NASA chose the EELV over the ATK [solid rocket booster], then what would everyone who makes their living from shuttle technology and equipment do once it’s retired?" he told Satellite News. "You just don’t understand how this town works!"

–James Careless

In the June 26 issue of Satellite News we will examine the benefits of using ATK’s solid rocket booster for the CLV and consider the arguments for repurposing space shuttle technology for the moon/Mars program.