NASA - Study Finds Human-rated Delta IV Cheaper
Click here for more news / Clique aqui para mais notícias
By Frank Morring, Jr.
A NASA-funded study found that a human-rated Delta IV heavy rocket could be a cheaper route to the International Space Station than NASA's Ares I crew launch vehicle.
But the human-rated United Launch Alliance rocket would be less expensive only if the Ares V heavy-lift moon rocket development is deferred, the Aerospace Corp. study reports. And the Delta IV alternative could add two years or more to the "gap" in U.S. human access to orbit if it starts this year, according to the unreleased study obtained by Aviation Week.
Ordered by Richard Gilbrech, the former associate administrator for exploration, the $500,000 study evaluated six different versions of the Delta IV heavy as an alternate to the Ares I, which NASA is developing in-house based on the solid-fuel first stage space shuttle boosters, the shuttle external tank, and the J-2 engine used in the upper stages of the Saturn V.
The study did not address the other U.S. Evolved Expendable Launch Vehicle (EELV) - a heavy-lift version of the Atlas V - because of "no clear advantages and several disadvantages," including the difficulty in obtaining human-rating data on its Russian RD-180 engines.
It found that a Delta IV heavy with an upper stage powered either by a variation of the Ares I J-2X engine or four engines derived from the RL-10-4A-2 engine could meet NASA's requirements for getting humans to low Earth orbit.
Aerospace Corp. engineers deemed it technically feasible to give the two Delta IV configurations the necessary redundancy and reliability for human rating, and found that both would permit "significant mass growth" in the Orion crew exploration vehicle or other elements.
For the Delta IV heavy using a modified J-2X upper stage engine, the study found no real cost savings over the Ares I. But for the version using four RL-10s, Aerospace Corp. estimated design, development, test and evaluation would come in at about $2 billion less in fiscal 2009 dollars than the Ares I projections. Life-cycle costs for 14 flights of that version of the Delta to low Earth orbit would be about $16 billion, $3 billion less than Ares I in today's dollars, the study found.
"Carrying cost is incurred for capabilities needed for Ares V that are developed under Ares I but not required for [the Delta IV heavy]," Aerospace Corp. found. "Total cost equivalency depends on carrying costs."
The Ares V capabilities that are being developed for Ares I include the stretched shuttle solid-fuel booster that will serve as a first stage for the Ares I, and the J-2X engine that also will power the Earth Departure Stage (EDS) to send the Orion crew vehicle, the Altair lander and other heavy hardware to lunar orbit from orbit around the Earth.
NASA is now targeting a March 2015 first flight of the Ares I/Orion stack with a crew inside. If the shuttle fleet retires as planned by the end of 2010 that would leave a gap in U.S. human access to space of about five years. The Aerospace Corp. estimates it would take from five-and-a-half to seven years to develop the hardware necessary to human-rate the Delta IV heavy.
Artist's concept of Ares I: NASA
