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#160 by Chris Bergin on 06 Sep, 2006 15:48
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Svetoslav - 6/9/2006 4:26 PM
Sometimes NASA amazes me with the decisions! Why did they have to scrap Atlantis knowing that Discovery is older than Atlantis? They should scrap Discovery, and keep Atlantis alive
As for the fuel cell, if it's performing OK, I see no reason to have more delays.
Atlantis HAS to retire first as she's next due for the Major Modification Period (which is a two year process that would make it pointless with the 2010 retirement for all orbiters). -
#161 by MKremer on 06 Sep, 2006 15:53
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You don't want to commit a mission this critical to a "Maybe it will work OK, now?" premise.
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#162 by psloss on 06 Sep, 2006 16:07
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Svetoslav - 6/9/2006 11:47 AM
That's OK -- most of us don't completely understand NASA-ese, either.
Yeah, that's right. Knowing the fact that there's a probability that a bigger failure is comming, I won't commit a mission before I'm sure everything is OK.
And the Atlantis that HAS to be scrapped - that's a mistake of my language and lack of english grammar knowledge.
PS: Offtopic caused by me should better be deleted.
If you don't understand, why not ask a question? I think that comes across much better than jumping to conclusions.
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#163 by Chris Bergin on 06 Sep, 2006 16:17
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One hour to go for MMT and sources say there are still presentations being uploaded for MMT evaluation. This could get really interesting.
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#164 by vt_hokie on 06 Sep, 2006 16:19
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Chris Bergin - 6/9/2006 10:09 AM
Vendors involved: UTC + Kearfott
Kearfott...haven't heard that name in a long time! Didn't know the company still existed... -
#165 by rdale on 06 Sep, 2006 16:21
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Will you know anyone with a laptop in that meeting?
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#166 by Chris Bergin on 06 Sep, 2006 16:22
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Some updates will be less important than others, but want to make sure the experts on here get to see everything....
Cameras and other GFE (-------)
Cameras and all other GFE were powered/checked when they were installed in/on Atlantis within the last 6 months. No cameras/GFE are powered/checked as part of S0007. Unless there is a known issue with any of this equipment, (----------------) do not believe there is any need to try to power up this equipment during the scrub. -
#167 by Chris Bergin on 06 Sep, 2006 16:22
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rdale - 6/9/2006 5:08 PM
Will you know anyone with a laptop in that meeting?
I would never answer that on a public thread. -
#168 by Mark Dave on 06 Sep, 2006 16:23
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So for a 24 hour scrub what is thetime they chose to launch?
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#169 by DaveS on 06 Sep, 2006 16:27
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Window opens at 11:58 EDT with in-plane being at 12:03 EDT.
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#170 by jacqmans on 06 Sep, 2006 16:31
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#171 by Chris Bergin on 06 Sep, 2006 16:33
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We're being told the reccomendation (current status) is rollback
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#172 by Chris Bergin on 06 Sep, 2006 16:35
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12 more documents going to the MMT being uploaded into L2.
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#173 by DaveS on 06 Sep, 2006 16:36
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Chris Bergin - 6/9/2006 6:20 PM
Damn. Looks like late October is the earliest they could do another attempt, right?
We're being told the reccomendation (current status) is rollback -
#174 by charlieb on 06 Sep, 2006 16:38
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Roll back?? LOL! A no brainer since the restart of FC-1 was pretty 'dismal' for a fuel cell. See my comments in L2.
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#175 by jacqmans on 06 Sep, 2006 16:43
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Fuel Cell Power Plants
Each of the three fuel cell power plants is reusable and restartable. The fuel cells are located under the payload bay area in the forward portion of the orbiter's midfuselage.
The three fuel cells operate as independent electrical power sources, each supplying its own isolated, simultaneously operating 28-volt dc bus. The fuel cell consists of a power section, where the chemical reaction occurs, and an accessory section that controls and monitors the power section's performance. The power section, where hydrogen and oxygen are transformed into electrical power, water and heat, consists of 96 cells contained in three substacks. Manifolds run the length of these substacks and distribute hydrogen, oxygen and coolant to the cells. The cells contain electrolyte consisting of potassium hydroxide and water, an oxygen electrode (cathode) and a hydrogen electrode (anode).
Read more:
http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/eps/pwrplants.html
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#176 by edkyle99 on 06 Sep, 2006 16:43
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Here is link with some diagrams of the Electrical Power Distribution and Control system.
http://klabs.org/DEI/Processor/shuttle/sp-504/section_4/section_4_10_electrical_power_distribution_control.htm
AC power is distributed to motors through motor controllers called "Motor Control Assemblies". There are ten MCAs that feed power to 250 (!) AC motors in the orbiter.
EDIT: It turns out that the fuel cell contains its own built-in three-phase ac "motor controller" for the coolant pump. The problem must, as a result, be internal to the fuel cell.
Here is the description of the orbiter's AC system.
"Alternating Current Generation and Distribution
Each forward avionics bay contains three power static inverter modules, which are connected in a phase-locked array to produce 117/200-volt, 400-hertz, three-phase, y-connected, four-wire ac power. Direct current input power to drive the inverter arrays is furnished by the respective forward PCA's, which contain circuitry to limit in-rush current to an acceptable level when the highly capacitive inverters are activated. Output current is limited to 20 amperes by circuitry within the inverters. The inverters are synchronized by an internal oscillator.
The output of each three-phase inverter array is monitored and controlled by an inverter distribution and control assembly (IDCA). Relays within the IDCA's connect the inverter arrays to the respective three-phase buses. These relays can be controlled manually by the crew, remotely from the ground during checkout, or automatically by internal circuitry in the event of an overload or an overvoltage. This automatic disconnect feature may be inhibited by the crew during critical mission phases to avoid disconnects caused by spurious signals or transients. Normal C&W monitoring and alarms will continue to operate when in the "inhibit" mode.
Each of the three redundant three-phase ac buses is isolated, is capable of supplying nominal power of 2.25 kilovolt-amperes, and is grounded to structure in a single point. All current is confined to the bus wiring except for some navigation equipment which uses an internal chassis ground. No provisions have been made for cross-tying the ac buses to accommodate inverter failures. Power reliability for critical ac loads is obtained either by providing a switch which allows access to more than one bus or by providing duplicate hardware operating off separate buses.
Ten motor control assemblies (MCA's), three each in the fore and aft avionics bays, and four in the midbody area, provide power and control to motors and other three-phase and single-phase loads in the Orbiter. Approximately 250 three-phase motors are required to drive deployment/retract mechanisms, latches, actuators, motorized valves, positioning devices, etc. Remote switching capability is provided by three-phase hybrid relays, which can be controlled by MDM commands."
- Ed Kyle -
#177 by c.steven on 06 Sep, 2006 16:49
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If rollback is the path chosen, what is the status of the VAB? Will the STS-116 stack have to be moved to the hurricane safe haven to make room for Atlantis, or is the other buildup high bay that was unavailable last week now availble? If I remember correctly, the unavailable bay was having some door R&R.
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#178 by Chris Bergin on 06 Sep, 2006 17:06
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Not sure when the press conference will be. We're up to 21 documents on L2 which they are about to go through at the MMT.
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#179 by Svetoslav on 06 Sep, 2006 17:06
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Oh, and it seems that the press conference is 10 minutes from now ( If I calculate the time zones properly ), am I right?
