WASHINGTON--NASA intends to conduct its final Delta 2 launch around the end of the decade and then shift more of its launch traffic in that payload class to the Atlas 5 or Delta 4 launch vehicles, the U.S. space agency?s chief rocket buyer said in an Aug. 8 interview.

Bill Wrobel, NASA assistant associate administrator for launch services, said the decision to phase out use of the Delta 2 came down to money. Delta 2 launch prices, already on the rise, are expected to jump sharply once the U.S. Air Force abandons use of the reliable workhorse as soon as next year so it can make greater use of the Atlas 5 and Delta 4, which the service helped develop under the Evolved Expendable Launch Vehicle (EELV) program.

?The Air Force is basically going full steam ahead with EELVs,? Wrobel said. ?And since they are a user of [the EELV rockets] we thought maybe we should become more of a user of it too.?

That policy position is consistent with an agreement NASA signed with the Air Force in 2005 when the space agency agreed to make greater use of the EELV rockets. In exchange, the Air Force endorsed NASA?s decision to build new shuttle-derived launchers rather than upgrade EELV for human missions to the Moon and beyond.

Wrobel said the U.S. Defense Department was informed last month of NASA?s decision to start directing the space agency?s medium-lift launch traffic toward EELV. Wrobel would not discuss current or projected prices for Delta 2 launches. However, he did say that an internal study NASA completed in July concluded that EELV would represent the more cost-effective solution for the agency?s medium-lift launch needs after 2010 ? even if the substantially more capable rockets are launched with a single undersized satellite on board.

?It turns out in the future, if you were to wrap everything up ? and I?m talking about launch site infrastructure, restarting the line, the basic cost of the vehicles, etc. ... it really isn?t more expensive? to use EELVs, he said. ?That?s part of what we were facing and what this really gets down to. As with anybody else, it?s all about money ... That?s where we all came to the decision that it made more sense for us to go down the EELV road in the future.?

Delta 2 prices, which sources said already have pushed past the $65 million per launch mark, are projected to rise even higher once the Air Force conducts its last Delta 2 mission ? a GPS 2RM satellite launch slated for September 2008 ? and leaves NASA to shoulder the cost of operating the rocket?s California and Florida launch pads and keeping United Launch Alliance?s Delta 2 assembly line in Decatur, Ala., up and running.

NASA took the Air Force?s impending departure from the program into account last year when it told bidders for the next Mars Scout mission to count on spending $120 million for a Delta 2 launching in 2011. Bidders for the next Discovery-class planetary science mission, meanwhile, were told to bank on paying around $130 million for a Delta 2 launching in 2013, according to sources and documents. Those two missions now are included among the 12 to 15 medium-sized payloads NASA anticipates launching between 2011 and 2020 on an Atlas 5 or Delta 4. In addition, NASA anticipates launching about 10 other spacecraft during that same timeframe ?which were already kind of in that EELV-class to begin with,? Wrobel said.

Prior to NASA?s decision to direct more launch traffic toward the EELV, United Launch Alliance was projecting an EELV launch rate of five to 10 launches a year between 2010 and 2020. The addition of NASA?s Delta 2-class payloads could mean an additional 1.5 launches per year for EELV. Mike Rein, a spokesman for Denver-based United Launch Alliance (ULA), confirmed NASA?s decision to stop using Delta 2 once the agency?s current launch services contract runs out. Rein said the company would continue to market Delta 2 launches to U.S. government customers and support Boeing Launch Services? commercial Delta 2 sales at least through 2012. ?ULA understands the combination of a reduction in the demand for launches from the NASA science community and the conclusion of the [U.S. Air Force] contract for GPS Delta 2 launches has made it difficult for NASA to justify the business case for continuing Delta 2 support beyond currently contracted missions,? Rein said in a written statement. ?ULA is required by our current NASA Launch Services contract with NASA to offer Delta 2 launches through launch year 2012.? NASA has used the Delta 2 twice so far this year and plans to use it a third time when it launches the asteroid-bound Dawn spacecraft in September.

Including the upcoming Dawn mission, NASA has nine remaining Delta 2 launches on its manifest with the last being a November 2009 launch out from California ? of the Wide-field Infrared Survey Explorer, or WISE, spacecraft.

Additionally, NASA is on the hook for a tenth Delta 2 that has not been assigned a payload. If NASA were to walk away from the rocket, which is already in production, the agency would have to pay United Launch Alliance a substantial termination fee. Exactly how much, Wrobel would not say. ?Let me put it this way, we are going to work pretty hard to try to find a home for it,? he said.

One candidate for the surplus Delta 2, according to Wrobel, is the Landsat Data Continuity Mission, a land-imaging satellite NASA is procuring on behalf of the U.S. Geological Survey for a 2011 launch. But a Landsat source said the program would rather launch on an EELV than go on what could be the last flight of Delta 2.

Wrobel said NASA has set an internal deadline of December for finding a payload for the surplus rocket.

Keeping the Delta 2 line open much beyond 2010 would be more complicated than giving United Launch Alliance a contract for a new batch of rockets beyond the 10 currently on order, Wrobel said. NASA also would have to cover significant one-time costs to restart production of certain Delta 2 components that remain in inventory but no longer are being built, including strap-on motors and the RS-27 main stage engine, Wrobel added.

?Restarting a line is nontrivial. You have things that have been out of production for a while,? Wrobel said. ?It?s a matter of restarting everything ? [and] we just don?t have the money.?

While using EELV for medium-class payloads is not expected to be more expensive for NASA than being the sole government customer for Delta 2, that still means the space agency is facing higher launch bills than it has today for launching Delta 2-class payloads.

Alan Stern, NASA?s associate administrator for science, said his launch costs would go up in either scenario.

While co-manifesting ? putting two spacecraft on a single rocket ? could help defray those costs, Stern said it is not a perfect solution. ?Co-manifesting has both pluses and minuses,? Stern said. ?In some circumstances it works. In others it is detrimental. There will be some places where it will help us and many places where it?s not to our benefit to do. Our challenge is to determine in each mission cases what makes the most sense.?

Wrobel said co-manifesting would be encouraged where appropriate but not required. Recognizing NASA?s best shot at keeping launch costs down could be a new rocket, several U.S. companies are looking to field Delta 2 alternatives priced more in line with what the agency traditionally has paid to put up medium-sized payloads.

El Segundo, Calif.-based Space Exploration Technologies? Falcon 9 rocket, which is slated to debut next year, could carry Delta 2-class payloads. And Orbital Sciences Corp. of Dulles, Va., has begun early development of a Delta 2-class launcher its calling Taurus 2.

?We will continue to talk to NASA about some ideas we have for a Delta 2-class launch vehicle that is conceived to be significantly less in terms of cost than the current Delta 2 design,? Orbital Sciences spokesman Barron Beneski said Aug. 9.

Wrobel said NASA has not ruled out directing some or even all of its future medium-class missions to new providers. ?We wouldn?t preclude using them in the future if they become available,? he said. NASA issued a request for information Aug. 7 intended to capture feedback from these companies and what they have to offer. He said the request for information is also an opportunity for companies to make suggestions for how the agency could improve its processes for qualifying new launch service providers.

Comments: bberger@space.com