Just when you thought that brand spanking new J2x engine was going to start getting a work out on that brand spanking new test stand at Stennis Space Center, along comes the ECO sensor problem on the shuttle to move those tests to the right. How, you ask, is that possible?
Well, if the ECO sensor problem is not solved, than a back-up to sensing fuel empty conditions in the shuttle fuel tanks is to sense how much LH2 and LOX you are using and to shut down the engines when nothing more comes through the pipe. That sensor has seen limited production and has been placed on some, but not all of the SSMEs. Because the program is winding down (unless you ask Rep Weldon), a decision was made awhile back to terminate further production of those flow sensors and fly with what is in the inventory. After all, the ECO system was "understood" and would make it to the end.
Of course, we all know now that the ECO system is not understood and will probably glitch a fair percentage of shuttle missions in the remaining queue. Each glitch results in one or more retankings of the External Tank, further stressing the touchy foam sprayed onto its exterior. Not a real good thing to do. So minion Hale is in the process of deciding to re-open the flow sensor production line and see to it that every SSME, from here to 2015, oh sorry, we meant 2010, has a means of watching the fuel coming into its chambers....or not.
And that's where the space shuttle program will help to further delay the testing of the J2x. Because every one of those sensors needs to be "green fired" to see if it operates properly, the only place those tests can readily be done these days would be on the J2X test stand at Stennis.
Just repeat after Hanley..."1-in-3 by 2013!" Uh-huh.