Contractors who supply hardware needed to keep the space shuttle fleet in service are starting to feel the pressure to wind down their manufacturing operations for shuttle components.

If NASA sticks to its plan to retire its three remaining shuttle orbiters by the end of 2010 after flying 28 or fewer missions, the U.S. space agency could soon have all the external fuel tanks, solid rocket motors and other shuttle components it will need.

NASA space shuttle officials told attendees of the Integrated Space Operations Summit in Nashville, Tenn., March 29-31 that the space agency already has sufficient quantities of aluminum lithium on hand to build all the space shuttle external tanks it will need between now and the end of the decade. NASA also has a full inventory of canister segments used to assemble solid rocket boosters. By 2008 the agency expects to have all the aluminum perchlorate it needs to manufacture the fuel for those boosters.

Any decision to cancel contracts or shut down manufacturing operations is complicated by the possibility that NASA could need some of these materials and components after 2010, if the United States decides to build a heavy-lift launcher that uses some of the shuttle’s major flight systems such as the main engines, external tank and solid rocket boosters.

However, NASA recently decided that it had all the External Tank (ET) Disconnects it will ever need and directed the contractor to shut down its manufacturing operation.

Located near the bottom of the shuttle’s giant orange external fuel tank, the ET Disconnect is essentially the detachable conduit that handles the cryogeni c fuel and liquid oxygen that the space shuttle’s cluster of powerful main engines burn on liftoff. NASA pays about $1.7 million for each one of the complicated plumbing assemblies.

Houston-based Boeing NASA Systems delivered its last ET Disconnect in March and moved all but eight employees off of the program.

Stephan Oswald, vice president and space shuttle program manager at Boeing, said the company has delivered 37 ET Disconnect ship sets to NASA — enough for the 28 planned missions plus 9 spares.

Boeing NASA Systems supplies the ET Disconnects as a subcontractor to Houston-based United Space Alliance, the Boeing and Lockheed Martin joint venture that maintains and operates the space shuttle for NASA. The hardware was built at a Boeing facility in Palmdale, Calif., and tested in nearby Huntington Beach.

About 20 Boeing employees were still working on the ET Disconnect program as of late last year. Boeing spokesman Ed Meme said that company plans to keep eight key people assigned to the program for the time being to continue to support the hardware until the last of it has flown.

Oswald said the decision to shut down the ET Disconnect manufacturing operation was easier than some that the space shuttle program faces, because this particular hardware design would not be used in any of the so-called shuttle-derived heavy-lift launcher concepts NASA and industry are evaluating for possible use for human expeditions to the Moon and points beyond.

Oswald said Boeing would be able to restart the ET Disconnect manufacturing operation with minimal hassle should the United States decide between now and 2010 not to retire the space shuttle fleet after all.

Oswald said Boeing has no plans to shut down its Palmdale facility. In addition to other space shuttle work, the Palmdale workforce also supports a variety of military aircraft programs and hush-hush Phantom Works projects.

Brian Berger is editor in chief of and the SpaceNews magazine. He joined in 1998, spending his first decade with the publication covering NASA. His reporting on the 2003 Space Shuttle Columbia accident was...