Shuttle Atlantis to prove her worth

by Chris Bergin

NASA have one final launch opportunity in the current window to get Atlantis into orbit to restart International Space Station assembly missions.

The launch attempt has to be successful, or the STS-115 mission will be pushed back to either late September, or more likely, late October.

**L2 STS-115 Coverage: L-2 and L-1 MMT Notes. ALL related handbooks, from Final Flight Plan to EVA Presentations (550mb of 115 presentations downloadable)**

**STS-115: LIVE COUNTDOWN AND LAUNCH Update Page** – One stop LIVE updates.

KEY EVENTS: (Colour code: Red ‘No Go’ – Green: ‘Go’)
External Tank Weather Orbiter Range.

60-plus presentations from MMT meetings now available.

Key Points/Newsflashes: Edwards Air Force Base incident – runway now cleared after F-22 emergancy landing. Very smooth count and no ECO sensor issues at this time. ET has no issues. A few weather concerns on the thickness of clouds in the region (now clear for launch). Small concerns about ice on the ET (minor – no constraint). All go for launch so far. God Speed Atlantis.

Refer to live update thread for up to the second updates.

Friday’s launch attempt was scrubbed, following a poll of managers and engineers on whether to launch with a 3/4 ECO (Engine Cut Off) sensor LCC (Launch Commit Criteria. This came about after the ‘failure’ of the LH2 ECO #3 sensor (failing WET) during tanking, at the fast fill stage. 

The ECO sensors are responsible for the indications on when the External Tank (ET) is running out of propellant, thus allowing the Orbiter to gauge when to power down its three main engines. Too early, and the Shuttle might not make it to its planned orbit, too late and the Orbiter could be ripped apart as the engine turbines overspin without their supply of fuel.

This sensor will not cause another scrub, as it will be deselected as part of a recent plan put forward by NASA. This pre-planned contingency procedure to allow 3 of 4 LCC, if failure repeats on the same sensor, calls for a 24 hour scrub – which won through during yesterday’s debate.

What would be deemed an issue is if another ECO sensor suffers a problem during the countdown. SIM troubleshooting would come into play, although it would likely end the opportunity for Atlantis to launch.
One interesting note from sources mentioned that some engineers do not believe the ECO sensors themselves are to blame, pointing at wiring between the Point Sensor Box (PSB) on Atlantis and the ET. How that may come into play during the countdown is yet to be understood.
As far as NASA are concerned, the reasons for their recent issues with the sensors was put down to a known sensor swage process and tooling control issues noted on sensors fabricated during 1996 timeframe, as a possible cause of ‘erratic’ sensor behaviour.’

The sensors in question on Atlantis’ tank have been classed as the ‘best available’ – which would also complicate the issue, should there be another problem during this countdown.
This article will be updated during the countdown.

(Video section is FREE, but you need to sign up as a member of the forum to enter the video section of the site. We only use your e-mail to send you your password. It will not be used for spam etc.)

** Job Opportunities** 

              LIVE UPDATE PAGES


Related Articles