Clean Discovery completes RPM and ISS docking

by Chris Bergin

Discovery has docked with the International Space Station (ISS) on Flight Day 3, as the initial TPS (Thermal Protection System) inspection images show a very clean orbiter. Prior to docking, Discovery carried out the RPM (Rbar Pitch Maneuver) for a full check of her TPS and belly.

The STS-119 crew head to the Station with no items of interest found via Flight Day 2’s TPS survey via the Shuttle Robotic Arm and the Orbiter Boom Sensor System (OBSS), as members of the DAT (Damage Assessment Team) await the host of RPM photography that has been taken by the Expedition 18 crew and downloaded to the engineers. 

The FD3 timeline had Discovery carrying out the RPM at around 8pm GMT – though that was slightly delayed by a small communication issue on the ISS, before docking with the ISS was completed just over an hour later. Hatch opening follwed less than a few hours later.

On the status of Discovery’s TPS, initial results show a very clean orbiter.

DAT have already created their opening presentation (available on L2), which was reviewed by the Mission Management Team (MMT) during their Flight Day 3 meeting.

So far, only a few minor areas of interest has been found during the inspections, none of which are of any concern for Discovery’s safe re-entry.

a214“Upper Surface Scans complete: No TPS damage by T-0 umbilical plates. Small fray detected on NLGD (Nose Landing Gear Door) forward thermal barrier,” noted the DAT presentation,” before adding that parts of the OMS Pod lacked the required lighting to gain a full view. However, the RPM photography will prove to be an able back-up.

“No tile damage or protruding gap fillers. Forward fuselage / wing glove areas inspected by the OBSS. No damage to report. Two OMS Pod gap filler protrusions noted. Portions of R (Right) OMS pod are in shadow and will require other sources to clear the leading edge tile.”

On the NLGD fray, no concern is noted, with DAT adding “based on previous flight experience/testing frayed area will “bend over” early in entry profile without causing early transition.”

Flight Day 3’s RPM – Rbar denoting along the radius vector of the ISS, downward – allows the ISS crew to perform a high resolution photo survey of the lower surface TPS tiles to screen for ascent debris damage.

a39The nine minute maneuver – which sees the orbiter commanded through a 360 degree back-flip – was debuted on STS-114’s Return To Flight mission, following months of planning by shuttle experts at the Johnson Space Center (JSC).

They were tasked with the limitations on crew and sensor visibility, maneuvers conducted about an unstable orbital station keeping position, inherently unstable attitude dynamics, thruster plume impingement on the ISS, shuttle propellant limitations, and a very tight set of lighting and geometry constraints for the inspection photography.

That photography will be downloaded to engineers on the ground, who will carry out what is now a well rehearsed exercise of checking through all areas of Discovery’s TPS for any areas of concern.

All of the current issues reported to the Mission Evaluation Room (MER) are minor and hold no mission impacts, with hardly any additions to the logs since Flight Day 2. Known as “funnies”, most of the issues will be dealt with once Discovery is back inside her OPF (Orbiter Processing Facility).

“New Funnies (since launch): Funny 1: ET Umbilical Well Camera Did Not Flash. Funny 2: Engine interface unit (EIU) #2 Intermittent Output During Ascent. Funny 3: Partial F4D Tyvek Cover Release. Funny 4: Fuel Cell 3 O2 Flow meter OSL,” outlined L2 information, and reported on Monday.

“Funny 5: Flt Deck Camcorder Configure Not working. Funny 6: Unable to download ET Umbilical well Camera Data. Funny 7: WLES Timeout Errors. Funny 8: Ergometer Pedal Restricted Movement.”

Funny number 8, which is related to an exercise machine onboard the orbiter, obviously holds no mission impact, though the availability of such equipment does hold an element of importance for the STS-119 crew to control muscle loss whilst on orbit.

a45“Problem Description: After assembly of the Shuttle Cycle Ergometer (SCE), the crew called down that the ergometer appears to be jammed or locked internally. The pedals move without problem in the reverse direction, and the crew confirmed the correct orientation of the ergometer,” noted a MMT presentation on the problem.

“The pedals are unable to move in the forward direction (with or without the Manual Control Knob, and with or without power). Crew has reported a “grinding” noise which sounds like it is coming from within the Ergometer when they attempt to pedal forward.

“Without the SCE, the crew would be unable to perform aerobic exercise when not docked to the ISS. If the SCE is unrecoverable, the Shuttle crew could use the ISS CEVIS Ergometer as an alternate method of exercise.”

The presentation noted that the most probable cause may be due to the SCE Breaking Band around the flywheel being too tight – either due to tension caused by the lever arms, the band not being aligned within its groove in the wheel, or physical interference of another internal component.

The crew still have alternative options for exercise on the orbiter, mainly via bungee cords that are stowed on the middeck.

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.

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