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#1120
by
DaveS
on 24 Jun, 2008 17:00
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Not sure if that is what grakenverb was referring to. How about the spark generators that start running during the seconds prior to SSME startup, throwing sparks at the SSME nozzles?
That's the so called Radial Outward Firing Ignitors(ROFIs). They're used to burn off any residual gaseous hydrogen to prevent any explosions during SSME start.
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#1121
by
kneecaps
on 26 Jun, 2008 21:40
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Not sure where else to ask as there doesn't seem to be a 'General' Q&A thread.
This is SORT of shuttle related.
I'm looking for some figures on the perfomance of the various STDN ground stations. I'm trying to model comm coverage/performance for a typical Shuttle mission and need some figures really. Antenna information, pointing angle limitations, max slew rates etc. Also things like EIRP and g/t figures...
Thanks to anybody who may know.
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#1122
by
Jim
on 26 Jun, 2008 22:44
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There are no more STDN ground stations.
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#1123
by
kneecaps
on 26 Jun, 2008 23:59
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There are no more STDN ground stations.
Oh! Hence my difficulty in finding public information...doh.
What do things like MILA come under?
So all mission comm including S-band is always via TDRS now?
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#1124
by
Jim
on 27 Jun, 2008 00:31
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There are no more STDN ground stations.
Oh! Hence my difficulty in finding public information...doh.
What do things like MILA come under?
So all mission comm including S-band is always via TDRS now?
Except during landing
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#1125
by
kneecaps
on 27 Jun, 2008 09:39
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There are no more STDN ground stations.
Oh! Hence my difficulty in finding public information...doh.
What do things like MILA come under?
So all mission comm including S-band is always via TDRS now?
Except during landing
Thanks.....maybe I'll model the TDRS then. Would you know of a source for the kind of data for TDRS that I was looking for for the STDNs?
Also the same for the orbiters S-Band and Ku system? I'm anxious to try my own link budget calculations and such.
Peter
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#1126
by
Chris Bergin
on 27 Jun, 2008 14:02
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Moved to a more relevant thread:
would it be possible instead of letting this be the last hubble mission to place it in the same orbit as the iss? I know it sounds stupid, but why wasnt it put in the same orientation in the first place, knowing that the iss was going to be built, i wonder why it wasnt initially planned that way in the beginning.
im sure that bringing hubble back to earth, relaunching it, and so on would probably be costly and also all the movement of hubble all around and such while doing so, but with all the money invested in hubble and with all the knowledge we're getting from it, why not? that way, hubble can be nearby the iss and serviced regularly.
just curious.
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#1127
by
Jim
on 27 Jun, 2008 14:16
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Moved to a more relevant thread:
would it be possible instead of letting this be the last hubble mission to place it in the same orbit as the iss? I know it sounds stupid, but why wasnt it put in the same orientation in the first place, knowing that the iss was going to be built, i wonder why it wasnt initially planned that way in the beginning.
im sure that bringing hubble back to earth, relaunching it, and so on would probably be costly and also all the movement of hubble all around and such while doing so, but with all the money invested in hubble and with all the knowledge we're getting from it, why not? that way, hubble can be nearby the iss and serviced regularly.
just curious.
Not possible, unless it is retrieved, and relaunched into the ISS orbit. It would be cheaper to build a new telescope and launch it from an ELV. Other than the repair mission, HST servicing hasn't been the most cost effective. It would be cheaper to have launched a fleet of telescopes
The HST was never intended to be serviced from the ISS. There was no space station in the works when HST was being built.
Also being near the ISS would subject HST to contamination from the ISS
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#1128
by
psloss
on 27 Jun, 2008 14:22
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would it be possible instead of letting this be the last hubble mission to place it in the same orbit as the iss? I know it sounds stupid, but why wasnt it put in the same orientation in the first place, knowing that the iss was going to be built, i wonder why it wasnt initially planned that way in the beginning.
im sure that bringing hubble back to earth, relaunching it, and so on would probably be costly and also all the movement of hubble all around and such while doing so, but with all the money invested in hubble and with all the knowledge we're getting from it, why not? that way, hubble can be nearby the iss and serviced regularly.
just curious.
Not necessarily the last word, but has been discussed here before:
http://forum.nasaspaceflight.com/index.php?topic=9152At the time Hubble was launched, the ISS didn't exist (not sure that even Shuttle-Mir had gotten very far). The space station was still Freedom, and it was going to be launched to 28.5 inclination which helps maximize payload performance for launches from KSC.
Also, I'm not sure the shuttle was capable of getting HST to the combination of 51.6 inclination AND the desired orbital altitude.
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#1129
by
astrobrian
on 27 Jun, 2008 15:11
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Also HST was put in a higher orbit to get away from the issue of light distortion in the pictures, kinda like going away from the city lights and you can see a lot more stars out
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#1130
by
Jorge
on 27 Jun, 2008 15:12
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Moved to a more relevant thread:
would it be possible instead of letting this be the last hubble mission to place it in the same orbit as the iss?
Possible, but not practical.
I know it sounds stupid, but why wasnt it put in the same orientation in the first place, knowing that the iss was going to be built, i wonder why it wasnt initially planned that way in the beginning.
To expand on what others have written, HST was launched in 1990. At that time there was no ISS (started in 1993), no Shuttle-Mir (started in 1992), and Space Station Freedom was intended for a 28.8 degree inclination orbit.
im sure that bringing hubble back to earth, relaunching it, and so on would probably be costly and also all the movement of hubble all around and such while doing so,
Correct, it would be quite costly. It is also the easiest way to get HST to ISS orbit, if you really wanted to do that.
but with all the money invested in hubble and with all the knowledge we're getting from it, why not? that way, hubble can be nearby the iss and serviced regularly.
Cheaper to build a new HST and launch it on an ELV than to do all that.
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#1131
by
usn_skwerl
on 27 Jun, 2008 15:38
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Though the answers provided are thorough, in reference to putting the HST "near" the ISS, some of us are missing the key point about orbital mechanics. Sometimes it's difficult to understand some of the more complex variables with them. An example of that would be inclinations. Without visual aides or detailed explanations, it's tricky to comprehend how it works. Another example of difficult mechanics is rendezvous. My limited experience with Orbiter Simulator shows me that even "in plane" launches are extremely difficult to be close to accurate.
As far as shuttle questions like the one posted by NasaPhotographer, without those small details about orbit that most 'rocket scientists' may know like the back of their hands, some of us backyard spacecraft spotters don't understand.
Only slightly off topic, is another issue I have difficulty wrapping my head around is why ISS's beta angle is a problem for the STS to dock. Without visual aides, or detailed explanations, some of us don't quite get it.
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#1132
by
psloss
on 27 Jun, 2008 15:53
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Though the answers provided are thorough, in reference to putting the HST "near" the ISS, some of us are missing the key point about orbital mechanics. Sometimes it's difficult to understand some of the more complex variables with them. An example of that would be inclinations. Without visual aides or detailed explanations, it's tricky to comprehend how it works. Another example of difficult mechanics is rendezvous. My limited experience with Orbiter Simulator shows me that even "in plane" launches are extremely difficult to be close to accurate.
No answers, but this reminded me of what I thought Jim Oberg wrote about regarding a last-minute request to change the timing of the FGB (Zarya) launch to help avoid having to de-orbit Mir...can't remember where his posts or stories on that are now, but here's a NYTimes story from the time:
http://query.nytimes.com/gst/fullpage.html?res=9E0CE4DB1F3EF932A25752C1A96E958260I'm sure someone here (like Mr. Oberg, for example
) knows where that info is online, though...
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#1133
by
usn_skwerl
on 27 Jun, 2008 19:09
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Excellent article, thank you
I do have a couple questions. (I am aware that they apply to all three engines, not just the centerline (#2 engine?))
In the attached pic, C is a vent always seen releasing what appears to be a mix of liquid and/or gaseous O2 or H2. Which is it?
What is the red tubing at arrow B for? I don't think I've seen that during a launch/flight.
What is the collar used for at arrow A?
Is there anything else that might be of interest in the pic aside from the RCS/paper covers and OMS shroud?
Who can I talk to about getting one of those "REMOVE BEFORE FLIGHT" flags from the vent? I'd love to have one.
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#1134
by
Jim
on 27 Jun, 2008 20:08
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A- Holds engine protection cover on
B- Transfer duct. ducts H2 to the nozzle tubes*, which flows back up the nozzle and provides cooling
C- there are multiple ducts (6) on the SSME, which drain/vent turbopump shaft seals etc. The gases are N2 or He
Edit: (Cavities in the LPFTP, HPFTP and CCV are drained via the component fuel drain line. These cavities are purged with a 2-scfm helium flow in preparation for engine start.).
The nozzle is constructed of hundreds of tubes (1,080).
on L2,
SSME bible
http://forum.nasaspaceflight.com/index.php?topic=4413.1Get in line for a red tag
updated.
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#1135
by
usn_skwerl
on 27 Jun, 2008 20:35
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Thanks for the reply, Jim, it's cool to know what i'm looking at during the continuous topoff procedures. At T-6.6 to T-0 I see the vents venting, and they never seem to hold flame from the SSME's, making me wonder if it was He, N2, H2 or O2 with an improper "fuel/air" ratio. Very cool.
Extremely unfortunately, I've never been able to afford to get into L2, and can't afford it for another long while.
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#1136
by
eeergo
on 28 Jun, 2008 16:57
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C- there are multiple ducts (6) on the SSME, which drain/vent turbopump shaft seals etc. The gases are N2 or He
I was under the impression that particular vent duct releases oxygen, or at least that was the talk in previous launches when the cryo cloud is very apparent.
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#1137
by
mkirk
on 28 Jun, 2008 17:22
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C- there are multiple ducts (6) on the SSME, which drain/vent turbopump shaft seals etc. The gases are N2 or He
I was under the impression that particular vent duct releases oxygen, or at least that was the talk in previous launches when the cryo cloud is very apparent.
Yes the one labeled C in the previous picture - from this perspective it is on the right side of the center and right engine and on the top side of the left engine. This is oxygen venting from the turbopump drains.
Mark Kirkman
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#1138
by
usn_skwerl
on 28 Jun, 2008 17:59
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C- there are multiple ducts (6) on the SSME, which drain/vent turbopump shaft seals etc. The gases are N2 or He
I was under the impression that particular vent duct releases oxygen, or at least that was the talk in previous launches when the cryo cloud is very apparent.
Yes the one labeled C in the previous picture - from this perspective it is on the right side of the center and right engine and on the top side of the left engine. This is oxygen venting from the turbopump drains.
Mark Kirkman
Then that still leaves me a bit unsure about how that LOX or GOX doesn't ignite at T-6.6 or later. I'm quite familiar with LOX from my experience in the navy, and know that it doesn't take much to ignite it. Is the 'fuel/air' ratio not 'lean' enough for combustion of the low pressure LOX coming from the vent?
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#1139
by
Jim
on 28 Jun, 2008 19:49
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GOX or LOX is not a fuel and therefore doesn't burn. It only supports combustion once a fuel is present
) knows where that info is online, though...
