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#1160
by
C5C6
on 20 Oct, 2007 01:22
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DaveS - 19/10/2007 2:02 PM
C5C6 - 19/10/2007 5:57 PM
DaveS - 19/10/2007 12:48 PM
C5C6 - 19/10/2007 5:45 PM
while ETs are delivered to KSC by barge, how would it have been delivered to VAFB???
Barge.
then it should have gone through the panama canal??? that would have taken weeks!!!
Bingo. That is the route that it would have taken.
are you aware how much time it would have taken to do the whole trip?? wasn't there any other way ever considered??
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#1161
by
Jim
on 20 Oct, 2007 13:18
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C5C6 - 19/10/2007 9:22 PM
DaveS - 19/10/2007 2:02 PM
C5C6 - 19/10/2007 5:57 PM
DaveS - 19/10/2007 12:48 PM
C5C6 - 19/10/2007 5:45 PM
while ETs are delivered to KSC by barge, how would it have been delivered to VAFB???
Barge.
then it should have gone through the panama canal??? that would have taken weeks!!!
Bingo. That is the route that it would have taken.
are you aware how much time it would have taken to do the whole trip?? wasn't there any other way ever considered??
just a few weeks. The second stage of the Saturn V had to almost make the same trip the other way.
There really was no alternative
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#1162
by
DaveS
on 20 Oct, 2007 13:28
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Jim - 20/10/2007 3:18 PM
There really was no alternative
Just to throw it out there: Early in the program they investigated the possibility of carrying the ET atop the SCA. But this idea died quickly after a set windtunnel tests showed that the buffeting off the ET was too severe for the SCA to handle.
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#1163
by
ChrisGebhardt
on 21 Oct, 2007 05:49
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DaveS - 20/10/2007 9:28 AM
Jim - 20/10/2007 3:18 PM
There really was no alternative
Just to throw it out there: Early in the program they investigated the possibility of carrying the ET atop the SCA. But this idea died quickly after a set windtunnel tests showed that the buffeting off the ET was too severe for the SCA to handle.
But what a site that would have been! :cool:
Also, in relation to a post about the second stage of the Saturn V almost making the trip from California, was the second stage originally to have been manufactured out in the CA?
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#1164
by
Jim
on 21 Oct, 2007 14:53
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Trekkie07 - 21/10/2007 1:49 AM
DaveS - 20/10/2007 9:28 AM
Jim - 20/10/2007 3:18 PM
There really was no alternative
Just to throw it out there: Early in the program they investigated the possibility of carrying the ET atop the SCA. But this idea died quickly after a set windtunnel tests showed that the buffeting off the ET was too severe for the SCA to handle.
But what a site that would have been! :cool:
Also, in relation to a post about the second stage of the Saturn V almost making the trip from California, was the second stage originally to have been manufactured out in the CA?
It wasn't almost. The S-II was built in Seal Beach, CA
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#1165
by
nsf-rt
on 22 Oct, 2007 23:44
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On the STS-120 Live thread I've just seen:
* Activate the orbiter's fuel cells (8:23 p.m.)
This got me wondering why they're starting them so far before launch, if they need power why not use power from the ground?
Just before launch we're going to get:
"Fuel cells to internal reactants (T-2:35) "
So presumably now they're on "external reactants" - how are they supplied and why not just supply power?
I've found lots of information at:
http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/eps/pwrplants.htmlThis let me know that warming the fuel cells up to operating temperature takes 25 minutes, so that can't be the reason for starting them so early.
I'm also aware that we get the famous step that we hear on the launch commentary:
Orbiter transfers from ground to internal power (T-0:50 seconds)
Perhaps the fuel cells are "active" but there is no - or little power drawn from them between now and T-50 seconds?
Perhaps that "little" power is just the fuel cell's internal systems?
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#1166
by
mkirk
on 23 Oct, 2007 00:08
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nsf-rt - 22/10/2007 6:44 PM
On the STS-120 Live thread I've just seen:
* Activate the orbiter's fuel cells (8:23 p.m.)
This got me wondering why they're starting them so far before launch, if they need power why not use power from the ground?
Just before launch we're going to get:
"Fuel cells to internal reactants (T-2:35) "
So presumably now they're on "external reactants" - how are they supplied and why not just supply power?
I've found lots of information at:
http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/eps/pwrplants.html
This let me know that warming the fuel cells up to operating temperature takes 25 minutes, so that can't be the reason for starting them so early.
I'm also aware that we get the famous step that we hear on the launch commentary:
Orbiter transfers from ground to internal power (T-0:50 seconds)
Perhaps the fuel cells are "active" but there is no - or little power drawn from them between now and T-50 seconds?
Perhaps that "little" power is just the fuel cell's internal systems?
There is actually a lot to those questions but I will start with a simple answer and if you need more detail after that then I, or someone else, will provide it.
The simple answer for the apparently early activation is that the launch team needs to ensure the fuel cells are on line and working properly. The launch team evaluates the performance of the individual cells (96 per fuel cell) as well as the overall ability of the fuel cells to provide the correct electrical loads to the vehicle. Performance calibrations are conducted and a purge of the fuel cells is performed to ensure the fuel cells are free of contaminants that could degrade performance. Activating the fuel cells at this point also provides some time to trouble shoot any issues that may arise.
Total power to the vehicle is shared between the ground support equipment and the fuel cells until the switch to internal power at T-50 seconds. The lswitch over is a gradual process (i.e. the load on the fuel cells is slowly increased) that is completed at T-50 seconds.
During the count, as systems are activated and brought online, the folks in the launch control center monitor the performance of the fuel cells and the entire shuttle electrical power and distribution system. I should also point out that the Ascent Flight Control Team in the Mission Control Center, while not actually responsible for the vehicle until liftoff/tower clear, are also watching the fuel cells and electrical system closely during the count.
Ground support equipment continues to provide reactants for the fuel cells until late in the countdown because this ensures the maximum amount of reactants available to support the requirements of the mission.
Mark Kirkman
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#1167
by
nsf-rt
on 23 Oct, 2007 00:27
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Thanks for that - does the fact that the fuel cells need to be online and working for so long to check they're OK indicate they're a in some way temperamental / unreliable / inconsistent?
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#1168
by
mkirk
on 23 Oct, 2007 00:40
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nsf-rt - 22/10/2007 7:27 PM
Thanks for that - does the fact that the fuel cells need to be online and working for so long to check they're OK indicate they're a in some way temperamental / unreliable / inconsistent?
No, not in my opinion. I wouldn’t characterize them that way at all.
It is just that the Fuel Cells and electrical power system are mission critical systems that operate 24/7 during the mission; the time to ensure they are up to the task is while you are still on the ground.
Mark Kirkman
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#1169
by
Davejfb
on 23 Oct, 2007 10:10
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i have a other question, and i hope this is the right spot to ask. And i hope my English is good enough.
When, at the end of the count, they say: 3, 2, 1, booster ignition and ........ Then they say a line. Who comes up with those lines? Does the PAO selected them or someone else? I collect all the calls on tape. So i was wondering who makes them?
Thanks.
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#1170
by
Jim
on 23 Oct, 2007 10:59
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Pao
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#1171
by
hutchel
on 23 Oct, 2007 23:25
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I did some searching and didn't see any discussion about this... The External Tank Camera - How long can it operate for? Typically we see them discontinue the feed shortly after the shuttle clears its field of view. How long after that can they take a video feed from it. I would imagine it would be sureal to continue the feed up until which time the tank starts to dissintigrate around it as it burns up. That would be a film worth seeing!
Lee
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#1172
by
MKremer
on 23 Oct, 2007 23:55
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It could operate and transmit as long as its batteries last. Wouldn't do much good, though, because the ET starts to tumble following separation (slowly, then faster as it begins designed propellent venting for that pupose). Tumbling disrupts the video signal reception, so the camera and transmitter turn off soon after separation.
(The camera has its own batteries, electronics box, and transmitter/antennas; it's a separate self-contained system by itself. see:
http://www.eclipticenterprises.com/products_overview.php )
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#1173
by
Jim
on 24 Oct, 2007 00:03
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Also the ET goes out of range of ER assets
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#1174
by
psloss
on 24 Oct, 2007 00:24
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#1175
by
STS-500Cmdr
on 24 Oct, 2007 01:07
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Is it me or have they done away with what was for a long time the traditional cake on the crew breakfast table with the mission emblem?--i've noticed this these last several flights now. Now i just see the emblem hanging on the front of the table
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#1176
by
Namechange User
on 24 Oct, 2007 02:42
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nsf-rt - 22/10/2007 7:27 PM
Thanks for that - does the fact that the fuel cells need to be online and working for so long to check they're OK indicate they're a in some way temperamental / unreliable / inconsistent?
Not at all but with all things in the count there is a time to do things so that things can continue to progress in an orderly fashion. The fuel cells are powered on the ground via external reactants being fed through the T-0 connections, so they are not using any of the LH2/LO2 loaded into the PRSD system. Since they are not using any onboard consumables this is not a limiting factor. Also the fuel cells share the electrical load with the ground power system. Once the fuel cells are put through their paces, via high/low load calibrations everything is then at nominal levels and the ET is loaded. Finally, you can't go anywhere without electrical power so it would be a real shame and a waste if the ET was loaded and you were much further into the count and then found an issue with the fuel cells.
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#1177
by
Avron
on 24 Oct, 2007 02:55
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#1178
by
MKremer
on 24 Oct, 2007 03:23
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Avron - 23/10/2007 9:55 PM
psloss - 23/10/2007 8:24 PM
Jorge covered a lot of this, so hopefully his answer will "stick" for a few pages:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=9814&start=1#M186120
Any idea as to the range from orbiter to tank at breakup? and the angle, i.e would it be aft of the orbiters orbit?
It'd be interesting to see what the average range would be.
As far as which is ahead, the tank is peaking at apogee and descending in a ballistic freefall while the orbiter is doing its OMS 2 burn. The tank should be trailing by a number of degrees by the time it starts to heat and break up.
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#1179
by
Jorge
on 24 Oct, 2007 03:51
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MKremer - 23/10/2007 10:23 PM
Avron - 23/10/2007 9:55 PM
psloss - 23/10/2007 8:24 PM
Jorge covered a lot of this, so hopefully his answer will "stick" for a few pages:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=9814&start=1#M186120
Any idea as to the range from orbiter to tank at breakup? and the angle, i.e would it be aft of the orbiters orbit?
It'd be interesting to see what the average range would be.
As far as which is ahead, the tank is peaking at apogee and descending in a ballistic freefall while the orbiter is doing its OMS 2 burn. The tank should be trailing by a number of degrees by the time it starts to heat and break up.
Actually, the tank will be leading by a fair amount. The OMS-2 burn raises the orbiter's orbit, resulting in a longer orbital period and causing it to fall behind the tank. But the amount will vary depending on the size of the OMS-2 burn, which is different on every rendezvous mission.