Aviation Week & Space Technology, 03/27/2006, page 54

Frank Morring, Jr., Greenbelt, Md.

Exploration plans advance for ground ops, lunar reentry

NASA engineers are digging in on the details of human exploration missions to the Moon and Mars, figuring out how to modify 40-year-old launch facilities in Florida for another 40 years of service, and simulating lunar reentry trajectories that will bring the planned Crew Exploration Vehicle (CEV) to the same landing site in the Western U.S. every time.

They are also taking another look at using the RS-68 rocket engine to power the big heavy lifter they are planning to carry expedition hardware to the Moon and Mars, trying to save money while easing the transition away from the space shuttle main engine (SSME) that was originally picked for the job.

"That transition issue is out there," says Daniel L. Dumbacher, deputy director of the exploration launch office at Marshall Space Flight Center. "We have to deal with that in terms of what it mean[s] to the shuttle program between now and 2010 with SSMEs being used on the [new vehicle's] core stage, and how we work through the supply chain issues, the obsolescence issues, personnel issues--it's really a skill-retention question."

Just as the engine decision will affect exploration operations for at least a generation in the future, decisions made a generation in the past are shaping work on the facilities that will be used to launch the CEV and the Cargo Launch Vehicle (CaLV) from the Kennedy Space Center. Engineers there are trying to make the most of what NASA has on the ground as U.S. human spaceflight moves between the last shuttle flight no later than the end of 2010 and the first flight of the CEV and its Crew Launch Vehicle (CLV) a few years after that.

P.E. (Pepper) Phillips, deputy director of the Constellation Project Office at KSC that is planning ground infrastructure for the Project Constellation exploration-mission launches, says the massive structures originally built in the 1960s to launch the Apollo missions to the Moon and later adapted for the shuttle will be heavily used by the exploration missions. Processing the CEV and related hardware will take place in the same high-bay where International Space Station (ISS) hardware is processed today, Phillips says, and the shuttle pads and processing facilities probably will be modified for the new shuttle-derived launch vehicles.

http://www.aviationnow.com/media/images/awst_images/large/AW_03_27_2006_1307_L.jpg

NASA's tight-money exploration plans envision using 40-year-old Kennedy Space Center launch facilities for another 40 years to return to the Moon and move on to Mars.Credit: NASA

Under one possible option, the early CEV/CLV flights--known as the Ascent Development Flight Test (ADFT)--will use an existing mobile launcher platform to move from the Vehicle Assembly Building (VAB) to the Launch Complex 39B pad. As the CLV matures, new mobile launcher platforms will be built that may have fixed service structures mounted on them alongside the vehicle stacks.

"What we're having to trade off in these particular studies are weight trades and whether or not it gets too cumbersome to transport that much weight on a mobile launcher platform and have all the services, including crew access, on the platform," Phillips says.

While the CEV begins its test flight program, the shuttle is still expected to be flying. The KSC Constellation office is studying how to transform the VAB, completed in 1966 for the Saturn V Moon rocket, from a shuttle-stacking facility into one that can handle both the CLV and CaLV far enough into the future to send missions to Mars. Options are still under study, but basically, the idea is to convert the four high bays in sequence to accommodate, first, the ADFT, then the CLV and ultimately the CLV and CaLV. The two shuttle launch pads, also originally built for Apollo, would be modified gradually as well (see diagram).

Although the CLV would launch from the historic complex at KSC, the CEV probably will land at a new facility in the Western U.S., says Charles W. Dingell, acting deputy manager of the CEV project office at Johnson Space Center. Engineers there are refining a quasi-aerobraking maneuver that would allow the CEV to return from the Moon with a four-member crew to a single landing site in the West at any time in the lunar month.

Computer simulations of the technique--known as skip-entry--suggest that it will not require much maneuvering fuel as the CEV skips out of the atmosphere to line up on the landing site. "We have a very simple, robust vehicle, but using some innovative targeting and guidance techniques, we're able to get a lot out of that," says Dingell.

The approach gives the simple ballistic capsule NASA chose as the CEV shape some of the maneuverability that the lifting-body shapes the agency rejected would have provided. It also allows the partially reusable CEV to fly into the same environment each time it returns to Earth from the Moon, rather than experiencing varying heat and mechanical loads.

The agency has already started running wind tunnel tests to gather data that will feed into the detailed flight-control algorithms that will be needed to make skip-entry work (AW&ST Mar. 13, p. 30). The early results are encouraging.

"We're really enthusiastic right now," Dingell says. "[In the] latest guidance algorithm that we're running, six [degrees of freedom], fully dispersed, we're showing that we're nailing the target without doing any sort of trim burn during that exoatmospheric period, so we're optimistic we're going to be able to reduce the Delta V [fuel] allocation for that."

DINGELL AND OTHER NASA exploration managers outlined the status of their work at a Mar. 14 session of the annual Robert H. Goddard Memorial Symposium here, sponsored by the American Astronautical Society. With NASA scientists and their Capitol Hill supporters howling over cuts to their programs in the Fiscal 2007 NASA budget request, cost control continues to be a big driver of the agency's exploration planning. The second look at the Pratt & Whitney Rocketdyne RS-68 symbolizes that approach (AW&ST Mar. 20, p. 23).

"There is probably less development work associated with an RS-68 than there is getting to a low-cost SSME," Dumbacher says. "We're working through that trade. We're working through the trade of what the actual unit cost [goes] to."

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Aviation Week & Space Technology, 03/27/2006, page 39

Frank Morring, Jr., Washington

Early work underway on refitting J2 Saturn upper-stage engine for new exploration role

Propulsion engineers at NASA's Marshall Space Flight Center are leaning toward an older version of the Rocketdyne J2 engine that powered Apollo missions to the Moon for the upper stage on a new generation of exploration launch vehicles.

But even though time is short and Pratt & Whitney Rocketdyne owns the drawings for the original engine, NASA is still working on its procurement strategy for the Crew Launch Vehicle (CLV) and apparently hasn't decided to go sole-source on the engine job. While its engineers like the original gas-generator version of the engine for the development time it will save, there is also more up-to-date technology that could find its way into what the agency has come to call the J2X before it flies.

"We're taking the best from the Saturn era [and] incorporating modern manufacturing techniques from all the engines we've built . . . to build the best cycle," says Jim Snoddy, upper-stage engine element manager at Marshall.

As it stands now, the new engine would meld turbomachinery from the newer J2S variant of the engine with the gas-generator approach from the original version to drive it. The J2S--"S" for "simplified"--was developed at the end of the Saturn program in the early 1970s to produce higher chamber pressure and thrust. It used a tap-off cycle, which draws hot gas directly from the combustion chamber to drive the engine turbines, instead of the gas-generator approach that burns propellant in a separate chamber to drive the turbines.

The J2S turbomachinery later found its way into the XRS 2200, the big linear aerospike engine Rocketdyne built for Lockheed Martin's planned X-33 reusable single-stage-to-orbit testbed, which NASA canceled in 2001 before its first flight. Still, that heritage cuts a lot of development time off the J2X engine, and time is money.

"It typically takes about 10 years to develop an engine from scratch," Snoddy says. "We already have the turbomachinery 90% [developed], because they took the turbomachinery from J2S."

Work on the J2X started only about two months ago, when NASA's exploration systems mission directorate adopted what it has come to call its "lunar sooner" approach to save money. The agency dropped plans to develop a new version of the Space Shuttle Main Engine (SSME) for the CLV upper stage, opting instead to bring the J2 out of mothballs for the job, even though it added at least six months to the CLV development schedule (AW&ST Jan. 30, p. 36).

In the long-term, the move should save money because the J2 is also baselined for the Earth departure stage that will eventually take humans back to the Moon. NASA also may drop the throwaway version of the reusable SSME planned for the heavy-lift Cargo Launch Vehicle (CaLV) in favor of the RS-68 engine that powers Boeing's Delta IV (see p. 54).

While both the J2 and SSME are human-rated, the lower thrust of the J2 required NASA exploration planners to add a fifth segment to the space shuttle Reusable Solid Rocket Motor (RSRM) that will be the first stage of the CLV. Last week, the Exploration Launch Office at Marshall outlined its basic CLV upper-stage concept in a request for information (RFI) from industry on the best way to procure the new stage.

According to the RFI, NASA plans to hire a contractor to build the upper stage at the Michoud Assembly Facility (MAF) in New Orleans, where space shuttle external tanks are built, using aluminum- lithium (Al-Li) originally ordered for the shuttle program (AW&ST Feb. 13, p. 42). Measuring about 83 ft. from the interstage that links it to the five-segment RSRM to the spacecraft adapter that will hold the Crew Exploration Vehicle (CEV) at the top of the 309-ft. vehicle, the upper stage will house friction stir-welded Al-Li tanks for liquid hydrogen and liquid oxygen propellant for the J2X.

It will also carry hypergolic bipropellant (MMH/NTO) thruster modules to provide roll control for the whole vehicle while the solid-fuel first stage is firing. Each module is currently baselined with four hefty 800-lbf. thrusters, mounted 180 deg. apart on the interstage. Two more reaction-control modules, each carrying six 100-lbf. thrusters, will be mounted on the upper-stage thrust structure assembly aft skirt for roll control when the J2X is firing after separation from the first stage, and for attitude control in three directions when the engine isn't firing.

NASA plans a "substantial" in-house development effort for the CLV upper stage, and will provide the J2X as government-furnished equipment to its production contractor, according to the RFI.

"The final integrated upper stage will be the product of numerous partnerships among industry participants and NASA, for the delivery and operation of the integrated upper stage," the document states. "NASA plans to maintain data rights on the design and the resulting upper stage hardware."

Snoddy says his office is also receiving industry input on the procurement strategy for the engine, with a final decision likely in the next two months. "Right now, the government's leading the study to go figure out what's the best acquisition strategy," he says.

In that study, NASA must balance the short development time allotted it--about five years--against applying the latest technology already available. "We can't afford to have any new technology in this because we only have five years, so we have to get all of the unknowns out of the equation quickly," Snoddy says.

NASA has scheduled an industry update on the upper-stage development at the MAF in New Orleans Apr. 18-19. Among questions likely to be posed there is whether the J2X will be acquired sole-source from Pratt & Whitney Rocketdyne, or through another mechanism like the joint venture that worked on the reusable 600,000-lbf. Cobra rocket engine earlier in this decade. In that project, which Snoddy also managed, Aerojet formed a dedicated joint venture with Pratt & Whitney (before it acquired Rocketdyne), and would like to do so again.

"IN RESPONDING TO NASA Administrator Mike Griffin's industry challenge to bring forward initiatives and concepts to help NASA achieve its Exploration objectives more quickly and cost-effectively, Aerojet believes a joint venture between the two large U.S. propulsion suppliers to develop new large engines is one such initiative," says Aerojet President J. Scott Neish. "We have established joint venture cooperative agreements for NASA in the past. We believe it provides NASA an efficient and cost-effective means to access the full range of design, development, manufacturing and test expertise across the industry."

Although "all of the trade space is open," Snoddy says, the engine is shaping up as a gas generator cycle with about 294,000 lb. thrust in a vacuum and a specific impulse of 448 sec. "We're looking at two walls for the regenerative nozzle section," he says. "We're looking at channel wall nozzle. We're looking at milled channel for the chamber. We're looking for all those things."

The engine will provide all of the pressurization for the upper stage and work on both the CLV upper stage and the Earth departure stage for missions to the Moon and, eventually, Mars. Plans call for a preliminary requirements review and a systems requirement review this summer to clear the way for procurement of long-lead materials and other items.

Subscale testing of some engine elements, including ignition and injector designs, has already started at Marshall. Planning is also underway for a power pack test at Stennis Space Center with the turbomachinery and gas generator. By late fall, modifications to the A1 Test Stand at Stennis should have begun for power pack testing next year.