FRR clears STS-119 for March 11 launch, pending SRB resolution
As expected, the Flight Readiness Review (FRR) has cleared Discovery to target a launch at 9:20pm on March 11, following a final review of the Flow Control Valve (FCV) flight rationale. One constraint – relating to the left SRB (Solid Rocket Booster) Range Safety System – will be worked over the weekend.
Engineers will replace cable and hardware in the left SRB and re-test the system over the weekend, after the FRR decided flying “as-is” would be unacceptable. Both SRB’s incorporate a range safety system, that includes a battery power source, receiver/decoder, antennas and ordnance.
“An anomaly was observed in the range safety system that could be attributable to the left hand Command Receiver Decoder (CRD),” added notes from the FRR.
“Therefore, the decision was made this morning to R&R the box tonight. Schedule for the retest after the R&R is dependent on when Delta launch occurs (launch scheduled for tonight) but is not expected to affect our launch date.”
Pending a successful re-test, engineers will begin full preparations to enter the launch countdown, known as S0007, on Sunday. Only one other “exception” was noted at the FRR, related to Ground Support Equipment – which will be resolved in time for the L-2 MMT (Mission Management Team) meeting.
“Call-to-stations (CTS) for launch countdown is currently scheduled for 1830 EDT on Sunday for the March 11 launch,” noted Friday processing information on L2.
“S1006 LH2 dew point and conditioning was completed yesterday. Orbiter aft closeouts continue and should finish up tonight.
“GH2 flange bolts were R&R’d yesterday and the bolt thread protrusion is now within specification. S0071 MPS/SSME and OMS/RCS pressurization for flight picks up tonight on 3rd shift and will complete on Sunday.
“Weekend work: S0071 HYPER/MPS pressurization for flight, IPR-0051/52 range safety troubleshooting, and launch countdown preps.”
Sunday will also mark the arrival of Discovery’s seven crewmembers at the Kennedy Space Center (KSC), with an expected arrival time of 3pm local.
The launch window will range from the 11th to the 16th – the latter resulting in a major reduction to the mission content, notably with space only for one EVA.
“KSC’s scrub turnaround plan reflected two consecutive attempts but they are receptive to three consecutive attempts,” added the FRR notes. “ISSP (International Space Station Program) is willing to launch as late as 3/16 (local time) and accept the loss of EVA content.”
The FRR approved the launch with only minor dissent, related to previous reservations regarding the decision not to install a special doubler plate to the 90 degree elbow bend, which is in the direct path of an impact from a liberated piece of FCV.
Click here for NASASpaceflight.com articles on the FCV issue since STS-126.
“The Shuttle Program poll to go for launch on 3/11. We are deciding to go without installing the doubler, but there is some dissent from those who would like to install the doubler,” noted one memo ahead of the FRR. “GO” for launch on 3/11, without the doubler, will be the Shuttle Program recommendation to the NASA Agency FRR.”
Confidence is high that none of the reinstalled valves on Discovery are threatening to suffer from a liberation, following an extensive check of the three valves – all of which have previously flown with Discovery four to five times.
The checks were based around signs of cracking, which was observed on some of the inspected stock of FCVs. Consistent test results via an “eddy current screening’ technique proved the ability to ensure the valves were free of cracks, and thus highly unlikely to liberate part of its poppet for at least the next flight – allowing for the single launch flight rationale.
“The FRR went very smoothly today and we have a go decision for a target launch date of 3/11/09, with potential opportunities through 3/16/09 pending range coordination. L-2 is scheduled for Monday at 9am EDT,” added notes from the FRR, acquired by L2.
“The entire community was comfortable with FCV rationale for flight, which is based on:
“1) mitigation of eddy current inspections showing no detectible cracks on installed poppets, 2) bounding analysis showing 125 deg. max particle size, if a poppet should fail, and 3) low likelihood and overall acceptable risk of critical failure consequences after extensive analysis and testing. Any further work to complete gimbal testing and the integrated PRA were deemed unnecessary.
“There were a couple dissenting opinions voiced about not flying a doubler on the elbow downstream of the FCV exit, but the community was uncomfortable with the residual risk of the doubler until final design verifications are complete.
“Although the recent focus has been squarely on FCV, the entire OPO team has done a terrific job getting us ready across the board to fly STS-119.
“A very special thanks to everyone working FCV for all the outstanding work as well as late nights and long weekends, just a remarkable job! Now get some rest this weekend before we go fly.”
L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.