Progress Fails to Raise ISS Orbit According to Plan

NASA Space Station On-Orbit Status 22 November 2004

"Update on reboost underperformance: The Russian Commission looking into the 11/17 reboost underburn has unanimously determined that both onboard hardware and software involved in the maneuver were not at fault, and that the underperformance was caused by human error. Whether an additional reboost is needed to make up for the delta-V deficit, with a commensurate slip in Progress 16P launch, still needs to be determined by a joint ballistics team. [It appears that a new onboard computer setting controlling fuel flow, installed about a month ago, should have been inhibited for the reboost maneuver, but the single command to do so was left out of the uplinked command sequence.]"

NASA Space Station On-Orbit Status 19 November 2004

"Update on 15P reboost: The official findings of the special investigational commission looking into the underperformance of Progress 15P propulsion during the ISS reboost maneuver on 11/17 is not yet available. U.S. readings from GPS (global positioning system) and the ISS onboard MAMS (microgravity acceleration measurement system) confirm that the reboost burn greatly missed its target values. While burn duration was about nominal (9 minutes), thrust acceleration data averaged only slightly more than half of the expected value, resulting in a total accumulated delta-V of 1.6 m/sec, instead of 2.6 m/sec. Actual mean altitude increase was 2.9 km, instead of 4.4 km target value. [According to preliminary evaluation by NASA HSG (Houston Support Group) in Moscow, working with Russian colleagues, one of the two Progress tanks, with ~30 kg of fuel remaining, was depleted first (the second tank still retains the propellant for the undocking and re-entry operations). Propellant was then drawn from SM tankage, whereupon thrust level dropped when a pressure regulator in the propellant feedthrough line from the SM restricted the flow to the thrusters, resulting in thrust reduction and underburn. Questions to be answered by the joint investigation, besides failure cause identification, include whether an additional reboost is required to make up the difference (either using SM prop or waiting for the next Progress, 16P) and possibly having to change the date of the 16P launch to meet the station's current altitude schedule (any launch date change will likely remain quite small due to the onboard consumables need).]"

NASA Space Station ISS On-Orbit Status 18 November 2004

"Update on 15P reboost: A special troubleshooting team convened by Moscow/RSC-Energia continues to investigate yesterday's Progress-350 thruster underburn, which yielded a delta-V of only 1.63 m/s as opposed to the expected 2.6 m/s. Resulting altitude increase was 2.4 km instead of 4.4 km. Preliminary reports are that both Progress hardware and software performed nominally. One of the aspects under investigation is available propellant supply. Also under study is the issue how soon to conduct a second reboost (which Progress-350 apparently would not be able to perform for lack of prop)."

NASA Space Station On-Orbit Status 17 November 2004

"Station reboost occurred at 9:12am EST as scheduled, producing a delta-V of 1.6 m/s, against an expected value of 2.6 m/s. Resulting altitude increase was 2.9 km instead of 4.4 km expected. MCC-Moscow (TsUP) is investigating the underburn of the Progress thrusters."

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This page contains a single entry by Keith Cowing published on November 22, 2004 1:00 PM.

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