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#700 by TheMadCap on 31 Dec, 2006 19:15
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Jim - 31/12/2006 9:27 AM
QuoteTheMadCap - 30/12/2006 12:47 PM
I don't think anyone answered this one:
Question regarding the zinc chromate putty in the field joints of the SRBs. The putty seals cracks in the connection between two cases, so it does in fact have to come into contact with exhaust gases?
How can this putty stand up to the heat and pressures involved?
The SRM burns from the inside outward.
OF course, duh huh! And since the less fuel remaining, the less thrust and pressure, it helps the seal stay intact as well, correct? -
#701 by Jim on 31 Dec, 2006 19:53
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pressure (and thrust) are, for the most part, constant* until near burnout.
* for this example, the actual thrust vs time curve doesn't matter -
#702 by TJL on 31 Dec, 2006 23:55
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On the Pratt & Whitney (SSME) chart it seems that all Block 2 engines are being used except SSME # 2048 which was last flown in October 1998 on STS-95. Was that engine retired?
Chart can be viewed here: http://collectspace.com/review/sts115_ssmechart-lg.jpg
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#703 by James Lowe1 on 31 Dec, 2006 23:58
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I 'believe' that question is answered in the L2 SSME "bible". There's 100mb of documents there, so I'll have a look through today.
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#704 by psloss on 01 Jan, 2007 00:30
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TJL - 31/12/2006 7:38 PM
Different powerheads, according to the chart. It's listed as 2038 / 2048 using the 6007 powerhead through STS-95 (October, 1998), and then listed as 2048 using powerhead 6021 beginning with STS-92 (October, 2000).
On the Pratt & Whitney (SSME) chart it seems that all Block 2 engines are being used except SSME # 2048 which was last flown in October 1998 on STS-95. Was that engine retired?
Chart can be viewed here: http://collectspace.com/review/sts115_ssmechart-lg.jpg
(Note that the 2038 / 2048 engine with the 6007 powerhead is not listed as active.)
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#705 by TJL on 01 Jan, 2007 01:32
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psloss..I missed that..thank you. So, Powerhead # 6007 is no longer active.
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#706 by Felonator on 03 Jan, 2007 19:25
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I have a question. I have searched the forums to make sure i aint asking same question, so sorry if i am.
At what speed during the landing stage do all the control surfaces become usable? And does the control stick feedback to the pilot? or does he/she just feel a dead stick? Hope they arnt stupid questions for the shuttle geniuses on here
Thanks
Mike -
#707 by kneecaps on 03 Jan, 2007 19:53
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Felonator - 3/1/2007 8:08 PM
I have a question. I have searched the forums to make sure i aint asking same question, so sory if i am. At what speed during the landing stage do all the control surfaces become usable? And does the control stick feedback to the pilot? or does he/she just feel a dead stick? Hope they arnt stupid questions for the shuttle geniuses on here
Thanks
Mike
Hi and welcome!
The orbiters aerosurfaces (or control surfaces) become active at different points during Entry. At EI (Entry Interface ~400k ft), the RCS provides control in all axes. During entry as dynamic pressure (q-bar) increases during entry various aerosurfaces are 'blended' in as they are able to provide more control authority than the RCS. Various documents (SCOM , Shuttle Crew Operations Manual) can give you more info but the first initial aerosurface control begins at about EI+3:00 (Entry Interface + 3:00 mins) and the surfaces are elevons and ailerons. By EI +28:00 the RCS Yaw jets are deactivated, these are the last jets to be deactivated in the Entry so at this point the aerosurfaces have total control.
No, there is no 'feedback' to the pilot from the stick besides its physical position, its totally fly by wire and sitck deflections are monitored by microswitches, probably feels much like a standard computer joystick prehaps.
I'm just an armchair astronaut but I'm sure somebody will jump in with some better info on this for you.
Pete -
#708 by Felonator on 03 Jan, 2007 20:07
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WOW! thanks for that Pete. Answers alot of questions Does anyone have a idea about the actual speed? Or guess at the mach number? I have messed with a supersonic wind tunnel and the force needed to move a control surface is unbelievable.
As for the control stick that must feel extremely odd for someone that has flown aircraft for along time. or not?? Does the STA simulate this too?
Cheers again
Mike -
#709 by mainengine on 03 Jan, 2007 20:18
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TJL - 31/12/2006 8:15 PM
psloss..I missed that..thank you. So, Powerhead # 6007 is no longer active.
Since this chart is actual a powerhead chart it is a little bit confusing.
Besides there were 47 engines flown on the shuttle in the 115 launches mentioned (look at the engine chart). -
#710 by kneecaps on 03 Jan, 2007 20:33
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Felonator - 3/1/2007 8:50 PM
WOW! thanks for that Pete. Answers alot of questions Does anyone have a idea about the actual speed? Or guess at the mach number? I have messed with a supersonic wind tunnel and the force needed to move a control surface is unbelievable.
As for the control stick that must feel extremely odd for someone that has flown aircraft for along time. or not?? Does the STA simulate this too?
Cheers again
Mike
Most modern aircraft high performance aircraft are fly by wire, but having flown various aircraft (none fly by wire though!) you tend to adapt pretty quickly to the feel of the stick, think about driving a car (if you do and its manual, ('stick-shift' for our American friends), it doesn't take long to get used to operating a different clutch.
If you have the SCOM look at section 5.4-6 it gives a breakdown of the mach numbers and what happens when. If not here they are:
+2:39 -29:35 Automatic elevon trim begins at a q-bar = 0.5 psf.
+3:32 -28:42 Aerosurface control begins at q-bar = 2.0 psf. CDR, PLT monitor elevon and aileron deflection angles on surface position indicator
+5:00 27:14 Roll RCS jets deactivated at q-bar = 10 psf.
+8:04 -24:10 Pitch RCS jets deactivated at q-bar = 40.
+20:03 -12:11 VREL=10 k fps
(Mach = 10) Alt = 150 k ft Speedbrake opens to 81 percent
+27:53 -04:21 (Mach = 1.0) Alt = 54 k ft RCS yaw jets are deactivated.
Some of the data sheets over at Bill Harwoods CBS pages show entry velocity, time info, so you could cross reference with these.
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#711 by Felonator on 03 Jan, 2007 21:08
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Thanks for all that. Thats more into what i was after As for the fly by wire. All the aircraft i have flown too have not been fly by wire and to me i think it must take alot to get used to it, IE over compensating when in control? But you will know more than me. Would be intresting to ask a shuttle pilot.
And again that leads me onto the STA, i take it that is all fly by wire so its exactly the same to the shutle??
Cheers again
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#712 by Jorge on 03 Jan, 2007 21:18
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kneecaps - 3/1/2007 2:36 PM
QuoteFelonator - 3/1/2007 8:08 PM
And does the control stick feedback to the pilot? or does he/she just feel a dead stick?
No, there is no 'feedback' to the pilot from the stick besides its physical position, its totally fly by wire and sitck deflections are monitored by microswitches, probably feels much like a standard computer joystick prehaps.
The Rotational Hand Controller (RHC) is an analog controller, not digital, so it uses potentiometers, not microswitches, to measure stick deflection. (Technically, there are microswitches in it but they are used for BFS engage, trim, PTT, etc, not flying). Like a PC joystick, the RHC has centering springs that provide increasing resistance to larger deflections: 1.45 in-lb per deg in pitch, 2.1 in-lb per degree in roll, and 0.7 in-lb per degree in yaw.
The Translational Hand Controller (THC) is digital and does use microswitches, but it's not used during entry.
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JRF -
#713 by Felonator on 03 Jan, 2007 21:24
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Excellent. Thanks for that Jorge. So there is some resistance. That would defo help to control it IMO. Kinda like a Force Feedback stick or not to that extreme? LOL sorry if noone has a clue. dont want to ask impossible questions.
Thanks again
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#714 by Jorge on 03 Jan, 2007 21:29
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Felonator - 3/1/2007 4:07 PM
Excellent. Thanks for that Jorge. So there is some resistance. That would defo help to control it IMO. Kinda like a Force Feedback stick or not to that extreme? LOL sorry if noone has a clue. dont want to ask impossible questions.
Thanks again
Just to clarify, the resistance is purely a function of deflection, it's not any kind of actual force feedback from the control surfaces.
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JRF -
#715 by Felonator on 03 Jan, 2007 21:36
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[/QUOTE]
Just to clarify, the resistance is purely a function of deflection, it's not any kind of actual force feedback from the control surfaces.
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JRF[/QUOTE]
Could you expand on that. Some of the terms i dont think i am 100% on. I understand that nothing is fed back to the pilot through the stick but there is a force applied against the pilots controls. Is that just to "center" it? Or from your answer before i understood it as, the more the angle of pitch, roll or yaw applied the harder the force applied back to the pilot. Is this to help simulate feedback through the controls?
Thanks again and sorry to keep askin
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#716 by kneecaps on 03 Jan, 2007 21:44
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JRF[/QUOTE]
Could you expand on that. Some of the terms i dont think i am 100% on. I understand that nothing is fed back to the pilot through the stick but there is a force applied against the pilots controls. Is that just to "center" it? Or from your answer before i understood it as, the more the angle of pitch, roll or yaw applied the harded the force applied back to the pilot. Is this to help simulate feedback through the controls?
Thanks again and sorry to keep askin[/QUOTE]
Its fine!
From what I can see of its design/construction it wouldn't feel much different to any other stick, probably better if anything. It doesn't seem to have much 'travel' compared with a aircraft though.
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#717 by Jorge on 03 Jan, 2007 21:58
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Felonator - 3/1/2007 4:19 PM
Just to clarify, the resistance is purely a function of deflection, it's not any kind of actual force feedback from the control surfaces.
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JRF[/QUOTE]
Could you expand on that. Some of the terms i dont think i am 100% on. I understand that nothing is fed back to the pilot through the stick but there is a force applied against the pilots controls. Is that just to "center" it? Or from your answer before i understood it as, the more the angle of pitch, roll or yaw applied the harder the force applied back to the pilot. Is this to help simulate feedback through the controls?
Thanks again and sorry to keep askin[/QUOTE]
It's ok, I could be more clear with my answers. The pitch, yaw, and roll in question are hand controller axes, not vehicle axes. The torque is applied to center the stick, but the amount torque varies by hand controller axis.
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JRF -
#718 by Felonator on 03 Jan, 2007 22:18
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I have found this page that is full of info
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rhc.html
Now the only question as of yet is...... And i hope i make sense as i just write as i think it.
You were talking about the axis of the rotational hand controller. Now as i understand it there are three yeah? and this "Yaw" imput that your talkin about, is this imputed by a twist of the stick? like clockwise/counter clock wise by a few degrees? and also is this just for the OMS. Which to be honest would make sense. But as for the Landing stage. This yaw imput into the RHC (ie twist of the wrist) if thats correct is only used until as Kneecaps informed me before "+27:53 -04:21 (Mach = 1.0) Alt = 54 k ft RCS yaw jets are deactivated." and at this stage do the rudder pedals become usable for controlling yaw.
Let us know if i need to ask my questions in a more infomed way. As i am trying to learn so much its easy for me to wonder off to something that totally might not make sense.
oh and cheers again
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#719 by Jorge on 03 Jan, 2007 23:24
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Felonator - 3/1/2007 5:01 PM
You were talking about the axis of the rotational hand controller. Now as i understand it there are three yeah? and this "Yaw" imput that your talkin about, is this imputed by a twist of the stick? like clockwise/counter clock wise by a few degrees?
That's right, the RHC has three axes, and yaw corresponds to clockwise/counterclockwise twist of the stick.Quoteand also is this just for the OMS. Which to be honest would make sense. But as for the Landing stage. This yaw imput into the RHC (ie twist of the wrist) if thats correct is only used until as Kneecaps informed me before "+27:53 -04:21 (Mach = 1.0) Alt = 54 k ft RCS yaw jets are deactivated." and at this stage do the rudder pedals become usable for controlling yaw.
The behavior of the RHC does depend on phase of flight. During powered flight, all three axes are available when manual control is selected. RHC inputs are used to control the SSME and SRB gimbals. Manual control during ascent has never been done in flight, and Flight Rules forbid it prior to 90 seconds after launch.
In orbit, all three axes are available when manual control is selected. RHC inputs are used to control the RCS jets, or the OMS gimbals when an OMS firing is in progress.
During entry, only RHC pitch/roll is available. The Entry Digital Auto Pilot (DAP) provides automatic turn coordination so that yaw inputs should not be necessary for banking maneuvers, though the rudder pedals become active for yaw control below Mach 5. RHC inputs are used either to fire RCS jets or deflect aerosurfaces, according to the qbar/Mach milestones posted earlier.
After touchdown, the rudder pedals are used to control nose wheel steering and brakes.
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JRF
At what speed during the landing stage do all the control surfaces become usable? And does the control stick feedback to the pilot? or does he/she just feel a dead stick? Hope they arnt stupid questions for the shuttle geniuses on here 