200 sar to usd

Jun 16

200 sar to usd

Assuming that works, the M3 line will be removed, clearing the way for Wheelock to disconnect the five electrical cables and loosen the four bolts holding the failed pump module in place. Caldwell Dyson, meanwhile, will prepare a spare pump module on external stor


200 sar to usd


فيديو 200 sar to usd

EUR/USD and GBP/USD Forecast February 20, 2017

مقالة عن 200 sar to usd

Astronaut Douglas Wheelock, applying brute force to shake a balky connector loose, successfully demated a final ammonia line from a failed coolant pump module today, setting the stage for the pump's removal and eventual replacement.

Because of a significant ammonia leak in the M3 connector during a spacewalk Saturday, Wheelock and Tracy Caldwell Dyson were unable to complete preparations for the pump's removal, leaving the line in place pending additional troubleshooting.

Today, the astronauts planned to first close a quick-disconnect fitting on the outboard end of the S1 truss to isolate the line leading to the M3 connector. But Caldwell Dyson was unable to depress a release button, preventing her from closing the outboard quick-disconnect.

Flight controllers then told Wheelock, anchored to the end of the space station's robot arm, to press ahead with an attempt to simply close the leaking M3 connector in hopes that lower pressure in the line, the result of earlier ground-commanded nitrogen venting, would reduce the leakage enough to disconnect the line from the pump.

To the relief of anxious flight controllers, the connector closed easily and no major leakage was observed.

"I don't see anything leaking," Wheelock reported.

"Excellent," replied Oscar Koehler from mission control in Houston. "And Wheels, if you see any leak, we're comparing this leak to what you saw when you first did the SPD on EVA-1.

"OK, I see a couple of little snowflakes," Wheelock reported a moment later. "But I don't see anything leaking around the white band like last time. ... OK, here they start to come out now by the white band, just little snowflakes."

The leakage quickly diminished and flight controllers told Caldwell Dyson there was no need to continue work to close the outboard quick-disconnect.

"That's great news," Wheelock said.

"It's awesome," Koehler agreed.

A few moments later, with no observable leakage, engineers decided there was no need to install a vent tool to release any residual ammonia that might be trapped in the line. Wheelock was then cleared to remove M3 from the pump module.

But in keeping with M3's now-familiar behavior, Wheelock was initially unable to pry the fitting apart using a lever tool.

"We believe there may be ice in there that's keeping it from releasing," Koehler advised. "So you've got a go to ... move the QD left to right to try to shake some of that ammonia ice out of there."

After working the fitting from side to side with no success, mission control told Wheelock "you've got a go to shake violently, that's the words I was given, in all directions."

Television views from Wheelock's helmet camera showed him energetically shaking the fitting from side to side. After multiple attempts, the connector finally released and Wheelock pulled the M3 line away from the pump at 10:23 a.m.

There were no obvious signs of problems with the connector and the astronauts were cleared to press ahead with their pump removal work. Five electrical cables will be demated by Caldwell Dyson before the astronauts loosen four bolts to free the pump from the S1 truss.

If all goes well, the pump will be mounted on an attachment fitting at the base of the station's robot arm transporter.

Astronauts Douglas Wheelock and Tracy Caldwell Dyson, floating in the Quest airlock module, switched their spacesuits to internal battery power at 8:27 a.m. to officially kick off a planned six-hour spacewalk. The primary goal of the excursion is to remove a shorted ammonia pump module so a replacement can be installed during a spacewalk Sunday.

This is the 149th EVA devoted to space station assembly and maintenance since construction began in 1998, the 13th so far this year, the fifth overall for Wheelock and the second for Caldwell Dyson. Going into today's outing, ISS spacewalk time stood at 929 hours and 38 minutes, or 38.7 days.

For identification, Wheelock, call sign EV-1, will be wearing a suit with red stripes around the legs and use helmet cam No. 19. Caldwell Dyson, EV-2, will wear an unmarked suit and use helmet cam No. 20.

The astronauts attempted to remove the faulty pump during a spacewalk Saturday, but one of four ammonia line quick-disconnect fittings leaked, presumably because of problems with an internal valve on the outboard side of the fitting.

Today, Wheelock will make another attempt to simply close the M3 quick-disconnect fitting. If the leak persists, the astronauts plan to close quick-disconnect valves at the inboard and outboard ends of the starboard one, or S1, truss where the pump module is located to isolate the ammonia line leading to the leaking connector.

Flight controllers earlier lowered pressure in the system and after the astronauts install a vent tool to get rid of any residual ammonia trapped in the line, the M3 quick disconnect will be closed and removed. That should clear the way for disconnection of five electrical umbilicals. After loosening four bolts, the failed pump module will be removed and temporarily mounted on a powered attach fitting at the base of the station's robot arm transporter.

If all goes well, a spare pump will be installed and reconnected during a third spacewalk Sunday.

Here is an updated timeline for today's spacewalk based on the official start time (in EDT and elapsed time; best viewed with fixed-width font):

EDT........HH...MM...EVENT  08:27 AM...00...00...Suits to battery power 08:32 AM...00...05...Post depress/airlock egress 08:47 AM...00...20...Setup 09:12 AM...00...45...EV-2: Close S1 outboard QD  09:27 AM...01...00...EV-1: Vent line routing 09:57 AM...01...30...EV-1: S0/S1 inboard jumper QD closed 10:12 AM...01...45...EV-2: M1 ammonia line restrained 10:27 AM...02...00...EV-2: Start venting 10:37 AM...02...10...EV-1: Close M2 ammonia line 11:07 AM...02...40...EV-1: Close vent tool 11:12 AM...02...45...EV-2: Vent tool cleanup 11:22 AM...02...55...EV-1: Close and demate M3 ammonia line 11:32 AM...03...05...EV-2: Cover and restrain M3 11:42 AM...03...15...EV-1: Break torque on failed pump module bolts 12:02 PM...03...35...EV-1: Retrieve adjustable grapple bar 12:02 PM...03...35...EV-2: Release failed PM electrical cables 12:32 PM...04...05...EV-2: Release failed PM bolts 12:47 PM...04...20...EV-1: Remove failed PM with AGB 12:57 PM...04...30...EV-2: Remove failed PM 01:32 PM...05...05...EV-1: Move failed PM to POA 01:42 PM...05...15...EV-2: Break torque on new PM; cleanup 02:02 PM...05...35...EV-1: Cleanup/airlock ingress 02:27 PM...06...00...Airlock pre-pressurization

NASA managers Tuesday approved plans for a second spacewalk Wednesday to deal with an unexpected ammonia leak that blocked removal of a faulty coolant system pump aboard the International Space Station during a spacewalk Saturday. If the plan works, the old pump will be removed and a new pump installed and hooked up during a third spacewalk Sunday.

Astronauts Douglas Wheelock and Tracy Caldwell Dyson planned to spend the night in the station's Quest airlock module at a reduced pressure of 10.2 pounds per square inch to help purge nitrogen from their bloodstreams before the planned 6:55 a.m. EDT start of the six-hour spacewalk.

NASA managers decided late Tuesday, however, to delay the start of the EVA by one hour, letting the astronauts get a bit more sleep and giving engineers more time to fine-tune robotics procedures. Under the revised timeline, Wheelock and Caldwell Dyson will switch their spacesuits to battery power at 7:55 a.m. to officially kick off the excursion.

For identification, Wheelock, call sign EV-1, will be wearing a suit with red stripes around the legs. Caldwell Dyson, EV-2, will wear an unmarked suit. This will be the fifth spacewalk for Wheelock, the second for Caldwell Dyson, the 13th station EVA so far this year and the 149th since assembly began in 1998.

The ammonia pump in coolant loop A failed July 31, leaving the space station with just one coolant system to dissipate the heat generated by the lab's electronics. The loop A failure forced the astronauts to implement a widespread powerdown to prevent critical equipment from overheating.

Four spare pump modules are on board and NASA planners quickly developed plans for two spacewalks to remove the old pump and install a replacement. But those plans went awry Saturday when the spacewalkers ran into major problems disconnecting one of four ammonia lines.

After struggling to close a quick-release fitting on the M3 line, the astronauts reported a significant leak. The quick-disconnect was reopened and the spacewalkers headed back to the airlock for routine decontamination procedures. Engineers suspect a problem with one of two internal valves on the outboard side of the pump module.

For the second spacewalk, Wheelock and Caldwell Dyson first will close quick-disconnect valves on both ends of the starboard one, or S1, truss segment where the pump module is mounted. With those valves closed, the ammonia line leading to the leaking connector will be isolated.

Flight controllers planned to reduce pressure in the line before the spacewalk began, clearing the way for Wheelock and Caldwell Dyson to install a vent tool to release any residual ammonia trapped in the pump and its plumbing.

Then, if all goes well, the now-evacuated connector can be disconnected and moved out of the way. After unplugging five electrical cables, Wheelock and Caldwell Dyson will loosen four bolts and remove the old pump module, temporarily mounting it on a stowage fixture at the base of the station's robot arm transporter.

The replacement pump module would be installed and reconnected during a third spacewalk Sunday. The quick-disconnect valves that were closed to isolate the leaking connector would be reopened at that point and flight controllers would be free to re-activate coolant loop A.

Flight controllers are considering an alternative scenario for Wednesday's spacewalk that includes an initial attempt to simply close the M3 quick disconnect in hopes that whatever caused the leak Saturday is no longer present. If no leak is observed, Wheelock could detach the M3 ammonia line straight away and press ahead with the pump's removal.

If the leak reappears, the astronaut would reopen the quick-disconnect and press ahead with work to isolate that section of the line. It is not yet clear whether flight controllers will, in fact, clear Wheelock to spend the time needed to reach the M3 valve as opposed to simply isolating the line right away as currently planned.

Here is an updated timeline of major events (in EDT and elapsed time; best viewed with fixed-width font):

EDT........HH...MM...EVENT  03:00 AM.............Crew wakeup 03:35 AM.............Crew hygiene break 04:45 AM.............EVA preps continue 06:15 AM.............Spacesuit purge begins 07:20 AM.............Airlock depressurization begins 07:55 AM...00...00...Suits to battery power 08:00 AM...00...05...Post depress/airlock egress 08:15 AM...00...20...Setup 08:40 AM...00...45...EV-2: Close S1 outboard quick-disconnect 08:55 AM...01...00...EV-1: Vent line routing 09:25 AM...01...30...EV-1: Inboard S0/S1 jumper QD closed 09:40 AM...01...45...EV-2: M1 ammonia line restrained 09:55 AM...02...00...EV-2: Start venting 10:05 AM...02...10...EV-1: Close M2 ammonia line 10:35 AM...02...40...EV-1: Close vent tool 10:40 AM...02...45...EV-2: Vent tool cleanup 10:50 AM...02...55...EV-1: Close and demate M3 ammonia line 11:00 AM...03...05...EV-2: Cover and restrain M3 11:10 AM...03...15...EV-1: Break torque on failed pump module bolts 11:30 AM...03...35...EV-1: Retrieve adjustable grapple bar 11:30 AM...03...35...EV-2: Release failed PM electrical cables 12:00 AM...04...05...EV-2: Release failed PM bolts 12:15 AM...04...20...EV-1: Remove failed PM with AGB 12:25 AM...04...30...EV-2: Remove failed PM 01:00 PM...05...05...EV-1: Move failed PM to stowage fixture 01:10 PM...05...15...EV-2: Break torque on new PM; cleanup 01:30 PM...05...35...EV-1: Cleanup/airlock ingress 01:55 PM...06...00...Airlock pre-pressurization

Flight controllers are revising plans for a second spacewalk Wednesday to replace a coolant pump aboard the International Space Station, adding work to isolate an ammonia leak that should clear the way for installation of a new pump during a third spacewalk Sunday.

A formal decision on whether to proceed with the Wednesday spacewalk is expected after NASA's space station Mission Management Team reviews preparations during a meeting Tuesday at the Johnson Space Center in Houston.

The pump module, one of two in independent coolant loops, circulates ammonia through huge radiators to dissipate the heat generated by the lab's electronics. The loop A pump shorted out July 31, forcing the six-member crew to implement an extensive powerdown to prevent equipment from overheating.

The station can operate safely with just one coolant loop, but both are needed for normal operations. Adding a bit of urgency is the lack of redundancy in a critical system. If the loop B system should suffer a shutdown before loop A is repaired, the space station would face a much more serious problem with little time to resolve it.

Astronauts Douglas Wheelock and Tracy Caldwell Dyson conducted the first of what was expected to be a two-spacewalk repair job Saturday. They had hoped to disconnect the old pump, demating five electrical lines and four ammonia quick-disconnects, before installing a spare pump at the end of the excursion. Ammonia lines were to be reconnected during a second spacewalk Wednesday.

But Wheelock and Caldwell Dyson ran into major problems with a quick-disconnect fitting on one of the ammonia lines attached to the failed pump. After struggling to simply disconnect the M3 fitting, they ran into a significant leak that forced them to leave the line in place while troubleshooters considered what to do next.

Because of the leak, the spacewalk ran eight hours and three minutes and required a decontamination procedure at the end to make sure the astronauts did not bring any toxic ammonia back into the station's pressurize modules.

Engineers believe the leak is due to problems with one of two valves in the quick-disconnect fitting. The valve in question is outboard of the pump module and cannot easily be vented to stop the leak.

As a result, engineers have come up with a revised plan for the crew's second spacewalk Wednesday, one that would require them to first open a quick-disconnect between the central S0 truss segment and the starboard one, or S1, segment. Another QD near the outboard end of the S1 segment also must be opened.

To lower pressure in that segment of the line, flight controllers plan to activate a pressure relief valve before the spacewalk begins to make it easier for the astronauts to close the S0/S1 segment quick disconnect. Wheelock and Caldwell Dyson then can use a vent tool to release any residual ammonia trapped in the line leading to the M3 quick-disconnect.

Assuming that works, the M3 line will be removed, clearing the way for Wheelock to disconnect the five electrical cables and loosen the four bolts holding the failed pump module in place. Caldwell Dyson, meanwhile, will prepare a spare pump module on external stor

Source: http://www.cbsnews.com/network/news/space/recent.html


مزيد من المعلومات حول 200 sar to usd 200 sar to usd