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#1400
by
klausd
on 04 Nov, 2010 00:55
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What was the reason for only can doing 3 launch attempts in a row? fuel-cells?
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#1401
by
TheFallen
on 04 Nov, 2010 00:58
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What was the reason for only can doing 3 launch attempts in a row? fuel-cells?
The main reason being that by November 8 the ISS will start being at an unfavorable angle to the Sun (Beta angle cutout) where it can't generate enough electricity and support a docked shuttle at the same time.
NASA has a limited launch window to send off Discovery before it has to wait till early December to try again.
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#1402
by
rdale
on 04 Nov, 2010 01:03
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What was the reason for only can doing 3 launch attempts in a row? fuel-cells?
A little bit of expendables, a little bit of fatigue. If you scroll up, you'll see there is a slim chance that they can use Monday if absolutely necessary.
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#1403
by
klausd
on 04 Nov, 2010 01:07
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thx, but I know about the beta cutout and the launch-windows. But if they try thursday, friday and Saturday, they can't go for sunday.
What is the main reason for that limit? You said expendables? So no refuelling for the fuel cell tanks necessary on Sunday if that happens?
where it can't generate enough electricity
I thought the reason was cooling. Because the shuttle would be exposed to the sun too much and it cannot cool itself enough...
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#1404
by
Alboita
on 05 Nov, 2010 08:39
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Hi all,
I have a question about the fuel used.
Where is stored the H2 and O2 before tanking operations?
And from where it come, where is produced?
Thanks
Alberto from Italy
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#1405
by
Jim
on 05 Nov, 2010 14:51
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1. There are two separate OMS systems. Double failure is unlikely
2. There is RCS backup
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#1406
by
MarsMethanogen
on 05 Nov, 2010 15:10
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Hi all,
I have a question about the fuel used.
Where is stored the H2 and O2 before tanking operations?
And from where it come, where is produced?
Thanks
Alberto from Italy
I know that this has been covered previously in this or the preceeding lineages of this thread. Pictures were provided, too. It's stored in (separately located) tanks near, but not too near the pad. At some time shortly before a launch, a convoy of tanker trucks comes in from "local" area cryo vendors and fill these holding tanks. Someone has even captured an image of this arriving convoy on past launches IIRC.
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#1407
by
Jim
on 05 Nov, 2010 15:14
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LH2 comes from Louisiana
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#1408
by
rbfnet
on 05 Nov, 2010 21:54
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Relating to the issues from earlier this week on the main engine controllers, at what point in the countdown would the failure of an engine controller no longer trigger a cutoff or hold? That is, if the backup engine controller for one of the SSMEs failed before T-31 would they not go past T-31? Inside of T-31 would RSLS cutoff automatically? After main engine ignition but before SRB ignition, would it trigger a pad abort? Some other point?
Is it the same answer if it's the primary, rather than the backup, engine controller that fails?
(I realize at the presser they said the transient they observed couldn't trigger a pad abort, because it wasn't severe enough to shutdown a controller. I'm asking about a hypothetical case where it is severe enough to cause a controller to fail.)
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#1409
by
psloss
on 05 Nov, 2010 22:07
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Relating to the issues from earlier this week on the main engine controllers, at what point in the countdown would the failure of an engine controller no longer trigger a cutoff or hold?
After liftoff, I believe.
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#1410
by
racshot65
on 06 Nov, 2010 12:11
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#1411
by
DaveS
on 06 Nov, 2010 21:07
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Just checking here: the monoball on the bipod yoke, is that one is ejected along with the rest of the yoke structure at ET sep? Or does it remain with the orbiter and is removed post-flight in the OPF during turn-around ops?
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#1412
by
MP99
on 07 Nov, 2010 13:13
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#1413
by
chempilot
on 07 Nov, 2010 14:56
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there' is a lot of info on Emergency Orbiter Egress procedures, but not a whole lot about Emergency Ingress/Rescue procedures. I was wondering this because on the side hatch of the orbiters have the following Rescue instructions:
1. Insert Tool-Unlock
2. Rotate to Vent Detent
3. Wait 2 minutes
4. Rotate to Hard Stop
anyone know who carries the special tool (if it is a special tool)? also why wait two minutes....that's a long time in an emergency!
thanks!!
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#1414
by
HelixSpiral
on 07 Nov, 2010 16:11
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Not sure who has the tool, but seeing as how the two minute wait comes after the "Rotate to Vent" step, the wait is most likely to let the crew module pressure to equalize with the outside pressure.
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#1415
by
chempilot
on 07 Nov, 2010 16:16
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thanks for the reply! that's what i thought too, but aren't the orbiters pressurized to 14.7psi (1atm), the same as outside pressure?
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#1416
by
JayP
on 07 Nov, 2010 16:40
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there' is a lot of info on Emergency Orbiter Egress procedures, but not a whole lot about Emergency Ingress/Rescue procedures. I was wondering this because on the side hatch of the orbiters have the following Rescue instructions:
1. Insert Tool-Unlock
2. Rotate to Vent Detent
3. Wait 2 minutes
4. Rotate to Hard Stop
anyone know who carries the special tool (if it is a special tool)? also why wait two minutes....that's a long time in an emergency!
thanks!!
The tools are kept at the TAL sites as part of the emergency kit.
http://www-pao.ksc.nasa.gov/nasafact/talsup.htmI couldn't find a description of the tool itself but it is probably some sort of socket wrench with an extention and the correct sized drive on it. you could probably buy the makings of one at a hardware store. Interestingly, the soyuz also uses a hatch opening tool, but they mount 3 of them on the bottom of the vehicle, behind the heat shield, so that anybody who gets to the capsule first can get the crew out.
As far as the two minutes thing, the latches on the hatch go over-center and are loaded by the cabin preasure, so it is probably impossible to actually unlatch them until the preasure is equalized.
I always thought it was a little strange that, after they added the tunnel thrusters, they did not add an external hatch jettison mechanism or at least tie it in to the ovehead panel jetison handle on the right side of the vehicle, but I assume there was a good reason.
Edit, 08-11-2010: On second thought, the latches probably can be unlatched under preasure. Otherwise, whats the point of having an outward opening hatch? The reason to wait until the preasure is equalized maybe because the location where the tool is inserted is on the face of the hatch and therefore, whoever is opening it will be standing right in front of it and could get smacked by it. The hatch weighs a few hundred pounds.
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#1417
by
JayP
on 07 Nov, 2010 16:51
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thanks for the reply! that's what i thought too, but aren't the orbiters pressurized to 14.7psi (1atm), the same as outside pressure?
They could have landed at a high altitude site. Zaragoza is 863 ft above sea level. Combine that with a local low preasure area and the preasure differential could be 2 or 3 psi easy.
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#1418
by
chempilot
on 07 Nov, 2010 17:04
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thanks JayP! that makes sense about the different landing sites. sounds like the russians have the right idea about having the tool attached to the vehicle.
i was thinking the two minutes was for decompressing of the gasket that seals the hatch or maybe a reset of the hatch pyro separation system.
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#1419
by
Fequalsma
on 08 Nov, 2010 11:20
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The monoball stays with the bipod. As I understand it, the pyro bolt fractures to permit separation, then the Orbiter internal fitting rotates so that the bolt fracture surface is parallel to and part of the Orbiter OML for re-entry. There are photos and diagrams out on the interwebs somewhere.
F=ma
Just checking here: the monoball on the bipod yoke, is that one is ejected along with the rest of the yoke structure at ET sep? Or does it remain with the orbiter and is removed post-flight in the OPF during turn-around ops?