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#1120
by
ChrisGebhardt
on 16 Oct, 2007 02:53
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DaveS - 15/10/2007 6:58 AM
Jorge - 15/10/2007 12:55 PM
The-Hammer - 15/10/2007 5:32 AM
I have a question regarding STS-115 and 117. The wikipedia article on STS-115 states that the crew was limited to 6 because of the mass of the P3/P4 Truss Segment. (One of the links is to a NASA podcast that backs up this claim.) However, STS-117, which carried the S3/S4 Truss Segment, was able to carry 7 astronauts. Both missions used Atlantis.
Why was STS-117 able to carry 7 when STS-115 could only carry 6? Did 115 have more cargo beyond the Truss Segment than did 117? Was NASA being conservative in regards to launch mass with 115? Something else entirely?
NASA had to offload about 400 lbs of middeck cargo from 117 to accommodate the seventh crewmember.
Also, STS-117 was a 6-member crew flight. The addition of Clay Anderson was a late addition made when Atlantis was in the VAB for ET hail repairs. If STS-117 had launched in March as originally planned, Clay Anderson would have flown up on STS-118 as originally planned.
I think Wayne Hale said that it also had to do with the time of year the missions were launched... something abaout gaining extra performance with a June launch than a March launch. I'm not 100% on this. Please correct me if I'm wrong or thinking of something else.
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#1121
by
Lee Jay
on 16 Oct, 2007 03:12
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Trekkie07 - 15/10/2007 8:53 PM
I think Wayne Hale said that it also had to do with the time of year the missions were launched... something abaout gaining extra performance with a June launch than a March launch. I'm not 100% on this. Please correct me if I'm wrong or thinking of something else.
Please look at my post and the answer that followed on page 52 of this thread.
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#1122
by
ChrisGebhardt
on 16 Oct, 2007 03:31
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Lee Jay - 15/10/2007 11:12 PM
Trekkie07 - 15/10/2007 8:53 PM
I think Wayne Hale said that it also had to do with the time of year the missions were launched... something abaout gaining extra performance with a June launch than a March launch. I'm not 100% on this. Please correct me if I'm wrong or thinking of something else.
Please look at my post and the answer that followed on page 52 of this thread.
OK. Thanks. The search functon doesn't work on my computer. Chris is aware of the problem.
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#1123
by
zerm
on 16 Oct, 2007 22:24
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I've been watching the STS112 onboard launch video and in the process of cleaning up the voicetrack I heard the PLT make the call "mini-bucket" a few seconds after liftoff. I've searched the Q&As here and not found a referance. Although I know what the term "bucket" refers to- I was wondering the exact meaning of the "Mini-bucket" call.
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#1124
by
mkirk
on 16 Oct, 2007 23:05
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zerm - 16/10/2007 5:24 PM
I've been watching the STS112 onboard launch video and in the process of cleaning up the voicetrack I heard the PLT make the call "mini-bucket" a few seconds after liftoff. I've searched the Q&As here and not found a referance. Although I know what the term "bucket" refers to- I was wondering the exact meaning of the "Mini-bucket" call.
As you probably already know the throttle bucket is a reference to the main engine throttle down sequence that occurs early during the first stage ascent to minimize aerodynamic loading. The engines are throttled back for a brief time before returning to the normal power setting of 104.5%. The term bucket comes from the way a graph that plots the throttle setting over time would look, in other words the reduced power area of the graph would look like a bucket.
Typically shuttle ascents are planned with a single throttle down event known as a single stage bucket. However dispersions in the performace of the SRBs (solid rocket boosters), either hot or cold, as assesed by the shuttle's guidance system at about the twenty second mark in the ascent, may dictate either a shallower bucket than orginally planned or a two stage bucket. The two stage bucket for example might result in a reduction of power to 80% then a few seconds later the engines would throttle back further to 72%.
This change from the planned power setting (determined pre-launch) as seen on the Main Propulsion System Chamber Pressure Gauges is what Pam was referring to.
Mark Kirkman
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#1125
by
dking023
on 17 Oct, 2007 03:33
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I am a space flight fan, I always have been...however my knowledge of science (particularly astrophysics) is very limited. A question that I have always wanted answered is whether the space shuttle could manuever and survive in open space rather than in the earth's orbit. I understand the it is called an "orbiter", however I was just curious if the shuttle could even though it was not designed for such an event.
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#1126
by
Ankle-bone12
on 17 Oct, 2007 04:03
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dking023 - 16/10/2007 10:33 PM
I am a space flight fan, I always have been...however my knowledge of science (particularly astrophysics) is very limited. A question that I have always wanted answered is whether the space shuttle could manuever and survive in open space rather than in the earth's orbit. I understand the it is called an "orbiter", however I was just curious if the shuttle could even though it was not designed for such an event.
If a propellant tank, RCS, OMS, and extra life support could be stored in the payload bay, Possibly. Maybe the OMS pods could be fired long enough for the orbiter to escape earths gravity, and head for lunar orbit. This is not an answer to your question but more of an expansion on it.
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#1127
by
Stowbridge
on 17 Oct, 2007 04:04
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dking023 - 16/10/2007 10:33 PM
I am a space flight fan, I always have been...however my knowledge of science (particularly astrophysics) is very limited. A question that I have always wanted answered is whether the space shuttle could manuever and survive in open space rather than in the earth's orbit. I understand the it is called an "orbiter", however I was just curious if the shuttle could even though it was not designed for such an event.
Welcome to the site.
No, orbiters can do all manner of movement in space, but only along her actual LEO (Low Earth Orbit). Someone asked the other day if orbiters could go to the moon. Problem is, even if they could, on the way back into Earth's atmosphere they'd be travelling so fast, they'd break up, unlike a capsule.
Shuttles are space planes and LEO is their domain.
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#1128
by
rdale
on 17 Oct, 2007 04:13
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#1129
by
Jorge
on 17 Oct, 2007 04:56
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Ankle-bone12 - 16/10/2007 11:03 PM
dking023 - 16/10/2007 10:33 PM
I am a space flight fan, I always have been...however my knowledge of science (particularly astrophysics) is very limited. A question that I have always wanted answered is whether the space shuttle could manuever and survive in open space rather than in the earth's orbit. I understand the it is called an "orbiter", however I was just curious if the shuttle could even though it was not designed for such an event.
If a propellant tank, RCS, OMS, and extra life support could be stored in the payload bay, Possibly. Maybe the OMS pods could be fired long enough for the orbiter to escape earths gravity, and head for lunar orbit.
No, not even close. An orbiter weighs ~ 200 klb and can carry a ~ 55 klb payload. Even if the entire payload were OMS prop (Isp 316 sec), you'd still have a much worse mass fraction than an Apollo stack (CSM+LM+IU+dry S-IVB weighs about 145 klb, S-IVB prop ~ 160 klb, and J-2 Isp 421 sec). At best you could reach a somewhat higher Earth orbit - probably lower than 1000 n.mi.
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#1130
by
HIPAR
on 17 Oct, 2007 05:57
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...'and voila, answer to the question'
At the risk of aggravating the experts, I'll have to say I don't like that answer. That answer is rather shallow because it assumes an unaugmented STS for the lunar mission. Certainly the shuttle will need some extra help in the form of extra propulsion for leaving and retuning to earth. No one here proposes to to land a shuttle on the moon.
So the question should be, 'What would be required to configure a shuttle-centric lunar mission'? How do we impart additional energy for the escape trajectory? How do we slow the spaceship on its return before we ask it to plunge and take the heat?
The consensus here is a shuttle lunar mission is impossible because it was designed to be an orbiter. Certainly, during the 25 years the shuttle has been flying, someone must have performed an analysis (maybe a thesis) on configuring it for a different mission. It's an obvious question and there is always someone out there with unconventional insight.
I'm perfectly aware that feasibility doesn't imply practicality.
--- CHAS
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#1131
by
brahmanknight
on 17 Oct, 2007 12:30
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Are sonic booms audible when the shuttle breaks the the speed of sound during liftoff?
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#1132
by
DaveS
on 17 Oct, 2007 12:34
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brahmanknight - 17/10/2007 2:30 PM
Are sonic booms audible when the shuttle breaks the the speed of sound during liftoff?
Pretty much no. They happen over water and is directed downwards towards the water so, no you can't hear them.
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#1133
by
Lee Jay
on 17 Oct, 2007 12:54
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HIPAR - 16/10/2007 11:57 PM
At the risk of aggravating the experts, I'll have to say I don't like that answer....
Certainly, during the 25 years the shuttle has been flying, someone must have performed an analysis (maybe a thesis) on configuring it for a different mission....
I'm perfectly aware that feasibility doesn't imply practicality.
And that's why I'd be surprised if anyone ever looked at it in-depth. Since it's totally impractical, why would anyone look at it? It would be far less expensive to construct a new vehicle that's actually designed for lunar operations. The Shuttle would be about the worst lunar vehicle anyone could dream up.
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#1134
by
Jorge
on 17 Oct, 2007 14:13
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HIPAR - 17/10/2007 12:57 AM
...'and voila, answer to the question'
At the risk of aggravating the experts, I'll have to say I don't like that answer.
Fair enough. I'll hazard a guess that you won't like my answer either.
That answer is rather shallow because it assumes an unaugmented STS for the lunar mission. Certainly the shuttle will need some extra help in the form of extra propulsion for leaving and retuning to earth. No one here proposes to to land a shuttle on the moon.
So the question should be, 'What would be required to configure a shuttle-centric lunar mission'? How do we impart additional energy for the escape trajectory? How do we slow the spaceship on its return before we ask it to plunge and take the heat?
The consensus here is a shuttle lunar mission is impossible because it was designed to be an orbiter.
No. The consensus here is that it may be possible but it's not worth wasting brain cells analyzing because it would be far more expensive than a purpose-built lunar craft and would not perform as well. It's just a silly idea all around.
I'm sure I could convert my car into a boat if I really wanted to. All I'd need is to waterproof the bottom and add gearboxes converting the steering wheel into a rudder and the driveshaft into a propeller shaft. And I'm equally sure it's not worth wasting brain cells on because I'd wind up spending more money doing that than it would cost to just go out and buy a freaking boat, and that boat would perform better as a boat than my converted car would. It's a silly idea.
Certainly, during the 25 years the shuttle has been flying, someone must have performed an analysis (maybe a thesis) on configuring it for a different mission.
I'm sure someone has written a thesis about it as well. I have long ceased to be amazed at the silly things academics write theses about, especially if they can get a government or industry grant to do it. Mating habits of Norwegian blue parrots, why smoking really isn't bad for your health, how to send a shuttle to the moon... the list is endless.
The only way that makes sense for my car to make a boating trip is to tow the boat to the slip and put the boat in the water. Likewise, the only way that makes sense to use a shuttle on a lunar mission is to launch components of a purpose-built lunar craft into LEO and assemble them there.
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#1135
by
joncz
on 17 Oct, 2007 14:36
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Jorge - 17/10/2007 10:13 AM
I'm sure someone has written a thesis about it as well. I have long ceased to be amazed at the silly things academics write theses about, especially if they can get a government or industry grant to do it. Mating habits of Norwegian blue parrots, why smoking really isn't bad for your health, how to send a shuttle to the moon... the list is endless.
Beautiful plumage, the Norwegian Blue!
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#1136
by
zerm
on 17 Oct, 2007 15:56
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mkirk - 16/10/2007 6:05 PM
zerm - 16/10/2007 5:24 PM
I've been watching the STS112 onboard launch video and in the process of cleaning up the voicetrack I heard the PLT make the call "mini-bucket" a few seconds after liftoff. I've searched the Q&As here and not found a referance. Although I know what the term "bucket" refers to- I was wondering the exact meaning of the "Mini-bucket" call.
Typically shuttle ascents are planned with a single throttle down event known as a single stage bucket. However dispersions in the performace of the SRBs (solid rocket boosters), either hot or cold, as assesed by the shuttle's guidance system at about the twenty second mark in the ascent, may dictate either a shallower bucket than orginally planned or a two stage bucket. The two stage bucket for example might result in a reduction of power to 80% then a few seconds later the engines would throttle back further to 72%.
This change from the planned power setting (determined pre-launch) as seen on the Main Propulsion System Chamber Pressure Gauges is what Pam was referring to.
Mark Kirkman
Looks as if you hit this answer directly on target- in looking at the time on the sound-track, she calls "Mini-bucket" at 23 seconds after SRB ignition- so the 20 second update would have been displayed, read and called in that 3 second period.
Thanks! That answers my question 104% ;-)
BTW- I'd advise everyone to go to L2 and watch this STS112 onboard video. There are a ton of little moments that will really tickle you. The crew CDR waving to the camera as the whiteroom retracts and then being given "major style points" by the PLT for doing so for example. Also, the 4 way handshake as they pass through 50 NM and the rookies become "rookies no more" really touched me. These folks were a real happy crew and it's is fun to watch them on the adventure. I only wish we had a lot more such videos. If your are not an L2 member- JOIN! This is just a sample of the really cool stuff kept there.
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#1137
by
swhitt
on 17 Oct, 2007 17:56
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I have looked around and not really found an answer to the following questions.
If you can point me to the docs on the following that would be great.
Is the OMS 2 burn the same as the NC1?
How long is the typical OMS 2 burn?
Are all NCx burns RCS burns?
Are all NCx burns determined after launch, based on the performance of previous burns, or are any of them of predetermined length?
And finally, what would be the typical numbers for NC1, NC2, NC3, and NC4 burns?
Thanks.
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#1138
by
Jorge
on 17 Oct, 2007 18:38
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swhitt - 17/10/2007 12:56 PM
I have looked around and not really found an answer to the following questions.
If you can point me to the docs on the following that would be great.
Is the OMS 2 burn the same as the NC1?
No. OMS-2 is the final orbital insertion burn. It is performed at or near apogee of the post-MECO suborbital trajectory to raise perigee at least above "Safe HP" (80 nmi). Beyond that, on non-rendezvous flights it is typically used to circularize the orbit, and on ground-up rendezvous flights (which all shuttle flights are these days) it can be used as a rendezvous phasing (NC) burn, but it is never labeled as NC.
NC1 is a separate burn, though it is sometimes designed as a post-OMS-2 correction burn and can be deleted if not required.
How long is the typical OMS 2 burn?
Varies widely. For ISS flights, typical post-MECO orbit is 122x30 nmi, so OMS-2 will always be at least long enough to raise perigee above 80 nmi. Beyond that depends on the mission and (for rendezvous flights) the phase angle. For historical data, see:
http://spaceflight.nasa.gov/shuttle/reference/green/ascorb.pdfAre all NCx burns RCS burns?
No, it is not uncommon for NC burns to be OMS burns. The last NC burn (NC4 for flight day 3 rendezvous, NC6 for FD4 RNDZ) is almost always an OMS burn unless the phase angle is very small.
Are all NCx burns determined after launch, based on the performance of previous burns, or are any of them of predetermined length?
The former. An NC burn is a rendezvous phasing burn designed to put the orbiter at some downrange distance (or phase angle) with respect to the target at some future time. So it depends on tracking of both the orbiter and the target. Flight Design makes pre-flight predictions for each NC burn based on a predicted target state vector and a reference liftoff date/time, but the actuals usually differ.
And finally, what would be the typical numbers for NC1, NC2, NC3, and NC4 burns?
Nothing "typical". The only thing you can say with certainty is that they are all "horizontal" burns (delta-V parallel to the velocity vector) and further, for a ground-up rendezvous profile, they will all be posigrade (delta-V in same direction as velocity).
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#1139
by
Danny Dot
on 17 Oct, 2007 19:40
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swhitt - 17/10/2007 12:56 PM
snip
Are all NCx burns RCS burns?
snip
If I recall correctly the break over to use the OMS is about 4 feet/second on the burn amount.
