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#1720
by
kraisee
on 09 Apr, 2009 12:20
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And another curio I've always wondered about, just how heavy is that Forward RCS pack in the nose of the Orbiter?
Ross.
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#1721
by
mkirk
on 09 Apr, 2009 13:31
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Can someone riddle me this:
What are the maximum "rates" for the Shuttle during ascent? I'm talking about pitch & yaw, how fast is the stack allowed to turn, as and when it has to.
It looks pretty slow based on the activity just after launch as she turns and pitches after clearing the tower. Eyeballing it, it looks somewhere around 1 degree per second, perhaps even less.
Anyone know what the limits actually are?
Ta,
Ross.
Are you talking about the maximum allowable rates/design constraints or the actual roll and pitch rates during the various flight maneuvers? For example, the “roll to heads up” is performed at 5 degrees per second.
I can probably dig up the max allowables – I really don’t remember any of them off the top of my head since it has been such a long time – but as you know they are different throughout the ascent (various parts of 1st stage, 2nd stage, SRB Sep, ET Sep, etc…). Loading and dynamic pressure are the limiting factors and as I am also sure you know a given roll/pitch or yaw command will produce a different load at different points in the trajectory.
Mark Kirkman
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#1722
by
mkirk
on 09 Apr, 2009 13:32
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And another curio I've always wondered about, just how heavy is that Forward RCS pack in the nose of the Orbiter?
Ross.
I might still have some of my old Mass Properties tables at home that might have good numbers for the pods. In the Shuttle Mission Simulator we would try to model as accurately as possible each shuttle orbiter and orbiter configuration. To accomplish that we had mass properties tables that among other things would give us the weight and ISPs for each of the OMS and RCS pods in the shuttle fleet that could then be used in the simulator model.
Mark Kirkman
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#1723
by
Mach25
on 09 Apr, 2009 14:42
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Anyone know what the limits actually are?
The IMUs are capable of measuring angular rates up to about 35 degrees/sec. Anything above that and the onboard navigation system won't know which way they're pointed.
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#1724
by
mkirk
on 09 Apr, 2009 20:02
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Can someone riddle me this:
What are the maximum "rates" for the Shuttle during ascent? I'm talking about pitch & yaw, how fast is the stack allowed to turn, as and when it has to.
It looks pretty slow based on the activity just after launch as she turns and pitches after clearing the tower. Eyeballing it, it looks somewhere around 1 degree per second, perhaps even less.
Anyone know what the limits actually are?
Ta,
Ross.
I still don’t know or recall what the vehicle is structurally capable of withstanding but I can tell you that the Flight Control System is capable of commanding rates of just under 12 degrees/sec for Pitch, about 12 degrees/sec for Roll, and around 6 degrees/sec for Yaw.
When practicing manual flying techniques in the Shuttle Mission Simulator, we trained to keep the rates under 10 degrees per second because that was the most that the Rate/Error needles on the Attitude Direction Indicator (ADI) could display. If you were above 10 degrees the needle would be “pegged out” and you would have no feedback regarding your true rates. For example the “Pitch-Around Maneuver” during an RTLS occurs at right about 10 degrees/sec in Auto but if you were to fly it manually the technique is to move the stick until you get a rate of about 8 degrees/sec.
We had specific rate excursions that if they were exceeded you were to engage the BFS or manually take over control of the spacecraft but I don’t recall those numbers off the top of my head – can look it up if you need.
What the vehicle can actually tolerate is something I will have to research if nobody else gives you an answer you are happy with.
As for what is actually flown I can say that the Roll after "Tower Clear" is done at about 9-10 degrees/sec (in Auto) and the Roll to Heads Up, like I said earlier, is done at 5 degrees/sec.
Mark Kirkman
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#1725
by
kraisee
on 09 Apr, 2009 23:15
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Wow Mark, that's a fair bit higher than I thought it would be. Obviously, just after clearing the tower they aren't under as much stress as they would be around max-Q, so I would expect that rate limits to drop to a minimum value around there -- possibly also lower as the vehicle approaches MECO under maximum g-load too. I would be curious to know what those limits are, if you can rustle them up from anywhere
Thanks,
Ross.
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#1726
by
kraisee
on 09 Apr, 2009 23:20
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And another curio I've always wondered about, just how heavy is that Forward RCS pack in the nose of the Orbiter?
Ross.
I might still have some of my old Mass Properties tables at home that might have good numbers for the pods. In the Shuttle Mission Simulator we would try to model as accurately as possible each shuttle orbiter and orbiter configuration. To accomplish that we had mass properties tables that among other things would give us the weight and ISPs for each of the OMS and RCS pods in the shuttle fleet that could then be used in the simulator model.
Mark Kirkman
Every time I hear things like that it awes me as to the amount of detail and precision which goes on behind the scenes of the Shuttle Program. That you accurately monitor the mass of each of the semi-interchangeable individual RCS Pods, and perform your simulations with the mass properties of the actual one intended to be flown... I can't imagine that there is more than a few hundred pounds of mass difference across the fleet WRT the Fwd RCS Pods. To accurately model that in the flight simulator is a remarkable level of attention to detail. Truly "expert" and very impressive.
Ross.
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#1727
by
Fequalsma
on 09 Apr, 2009 23:38
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Ross -
From JSC-26098, page D-84,
RCS FWD MODULE ENGINE INST 869.0 (lbs)
RCS FWD PRESSURIZATION SYSTEM 148.0
RCS FWD PROPELLANT SYSTEM FUEL 265.3
RCS FWD PROPELLANT SYSTEM OXID 248.7
Cheers,
F=ma
And another curio I've always wondered about, just how heavy is that Forward RCS pack in the nose of the Orbiter?
Ross.
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#1728
by
Aobrien
on 10 Apr, 2009 16:46
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How deep is the crawler way in gravel?
Thanks
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#1729
by
ChrisGebhardt
on 10 Apr, 2009 17:39
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How deep is the crawler way in gravel?
Thanks
Crawlerway Statistics
Length from VAB to Pad LC-39A - 5,535 meters (18,159 ft)
Length from VAB to Pad LC-39B - 6,828 meters (22,440 ft)
Width: Overall 40 meters (130ft). Each lane is 12 meters (40ft) with a 15 meter (50ft) median.
Depth: Average depth is 2 meters (7ft); 0.8 meters (2.5 ft) hydraulic fill, 0.9 meter (3ft) graded limestone, 0.3 meters (1 ft) selected fill, asphalt sealer; 10.16-20.32 cm (4-8 in) of river rock on top to reduce surface friction.
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#1730
by
eeergo
on 10 Apr, 2009 18:15
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Quick question about the ROFIs: how are the sparks produced? Is it some kind of metal-on-metal grinding mechanism, pirotechnics...? Can they be restarted whenever needed?
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#1731
by
Jim
on 10 Apr, 2009 18:51
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one shot pyros
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#1732
by
MarsMethanogen
on 10 Apr, 2009 18:58
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one shot pyros
By "one shot" do you mean they are initiated and used only a single time and then have to be replaced? I ask because the "sparks" continue for several seconds just prior to SSME ignition. They remind of what is referred to as a "Roman candle" type of firework in the US.
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#1733
by
Jim
on 10 Apr, 2009 19:01
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one shot pyros
1. By "one shot" do you mean they are initiated and used only a single time and then have to be replaced?
2. I ask because the "sparks" continue for several seconds just prior to SSME ignition. They remind of what is referred to as a "Roman candle" type of firework in the US.
1. yes
2. That would be a fountain. "Roman candles" fire projectiles
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#1734
by
MarsMethanogen
on 10 Apr, 2009 19:03
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one shot pyros
1. By "one shot" do you mean they are initiated and used only a single time and then have to be replaced?
2. I ask because the "sparks" continue for several seconds just prior to SSME ignition. They remind of what is referred to as a "Roman candle" type of firework in the US.
1. yes
2. That would be a fountain. "Roman candles" fire projectiles
You're absolutely correct!
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#1735
by
eeergo
on 10 Apr, 2009 19:18
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Thanks for the answer Jim. Do they last long enough so that they can be useful in an abort after SSME start or is there some other system (apart from the water dissipation sprayers) I seem to recall they were still firing the STS-68 pad abort but I'm working from memory here...
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#1736
by
brahmanknight
on 10 Apr, 2009 19:26
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I don't know if this would belong in an EVA QandA thread, but...
On STS 102, Voss/Helms performed a 8 hr 56 min EVA. Is that the absolute limit for EVA in US suits?
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#1737
by
kraisee
on 10 Apr, 2009 19:42
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Ross -
From JSC-26098, page D-84,
RCS FWD MODULE ENGINE INST 869.0 (lbs)
RCS FWD PRESSURIZATION SYSTEM 148.0
RCS FWD PROPELLANT SYSTEM FUEL 265.3
RCS FWD PROPELLANT SYSTEM OXID 248.7
Thank-you for that -- and for the file too.
Ross.
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#1738
by
DaveS
on 10 Apr, 2009 20:28
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This is something that has had me wondering for quite a while:
How was the OTS transported from VAFB to KSC? By aircraft? Barge like the two Payload Canister transporters in 2000?
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#1739
by
psloss
on 10 Apr, 2009 21:33
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Thanks for the answer Jim. Do they last long enough so that they can be useful in an abort after SSME start or is there some other system (apart from the water dissipation sprayers) I seem to recall they were still firing the STS-68 pad abort but I'm working from memory here...
No, they start at T-10 seconds and run for 10 seconds. If you watch the STS-68 abort (or an FRF or any count that gets inside T-10), you can see the ROFIs "run out."
You might recall that part of the reason for the 48-hour recycle after the cutoff on the first STS-93 launch attempt was to re-service the ROFIs.
