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#520
by
Danny Dot
on 02 Sep, 2009 02:37
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What is the whirring noise heard usually at about T-15 seconds? it sounds like what you'd expect the high-pressure turbos to sound like but this is much too early for them, so I can only guess its air being forced through the pipes and out of the nozzles as water runs through the sound suppresion system?
The ROFI systems powering up.
I think it is the SRB's Aux Power Units powering up. And they are turbines.
Danny Deger
SRB HPU start is T-27secs with SRB nozzle steering checks at T-21secs
I thought they started at T-19. I am certainly not a reliable source on this though, so you are probably correct. But I do recall STS-51 "aborted" at T-19 because one didn't start.
Danny Deger
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#521
by
Danny Dot
on 02 Sep, 2009 03:10
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snip
The fear of going into a spin - potentially a hypersonic spin.
snip
Hypersonic delta wings actually
love high alphas. They actually go out of control due to dutch roll at low alphas and the shuttle has a lower hypersonic alpha limit for this reason. For example, the shuttle flies a hypersonic alpha 57 on an RTLS. Like I said, the autopilot is fully certified to alpha 60 hypersonic. It is in the SODB that I know is in L2 here, but I can't find it.
Danny Deger
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#522
by
Danny Dot
on 02 Sep, 2009 03:59
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So no downsides?
Only need to look harder for a landing site.
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Faget's orbiter had a high drag profile pushing stability - was it due to perceived TPS limitations or fear of entering a flat spin. Also, was dynamic, adaptive profiles and aborts to other landings considered or not.
I am not familiar with this design. Post a link here and I will take a look.
Do you have any idea of the figure of merit of how much -meaning are we talking a drastic decrease or a linear relationship?
Drastic decrease in heating. On a high energy TAL, the orbiter bug is WAYY past the high temp line on the TRAJ display. And, this is at alpha 50. I think it is linear with coeficent of lift because, but I am not sure. I derived the effect once, but it is late and I have my own spaceship to get past SDR by Sept 22.
snip
The pilot was I think aware of the issue soon into entry - too late to change profile (e.g, adaptive), although I think I heard he altered yaw and pitch to attempt to mitigate. It doesn't seem like he had much other in the way of options to mitigate.
Too late to change in the middle of the entry, but it could be done. Rick Husband took control just before data was lost. It is obvious he was reacting to the un-commanded roll the left. He reacted exactly as I trained him to.
Even the theory of a crack or deformation from laminar flow on the leading edge is a significant issue for entry, so you would want to fly a profile to unstress it in a safety culture. Was the high alpha entry more likely to be distrusted because of it being untried, or simply considered ineffectual for a potential issue -e.g. the cure being worse than the disease?
Remember the official answer was Columbia wasn't hurt. We didn't even need to ask DOD to take pictures. I have no doubt the people that invented high energy TAL would have figured this out if asked. I had even seen flight controller make a call real time in a sim to increase alpha to reduce heating. Increasing alpha to reduce heating was not a secret. It is now though
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When was the commit to do the procedure? Prior to entry or during entry?
Before the entry.
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That's very creepy.
Dying in the sim was not uncommon. That is what they are for. I asked John Young once about him dying during training during a sim that they didn't get the LM up and running in time. He responded he died so many times, he wouldn't have a chance to remember.
snip
Danny Deger
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#523
by
nooneofconsequence
on 02 Sep, 2009 04:12
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#524
by
ChrisGebhardt
on 02 Sep, 2009 04:45
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What is the whirring noise heard usually at about T-15 seconds? it sounds like what you'd expect the high-pressure turbos to sound like but this is much too early for them, so I can only guess its air being forced through the pipes and out of the nozzles as water runs through the sound suppresion system?
The ROFI systems powering up.
I think it is the SRB's Aux Power Units powering up. And they are turbines.
Danny Deger
SRB HPU start is T-27secs with SRB nozzle steering checks at T-21secs
I thought they started at T-19. I am certainly not a reliable source on this though, so you are probably correct. But I do recall STS-51 "aborted" at T-19 because one didn't start.
Danny Deger
"There are two self-contained, independent Hydraulic Power Units (HPUs) on each SRB. Each HPU consists of an auxiliary power unit (APU), fuel supply module, hydraulic pump, hydraulic reservoir and hydraulic fluid manifold assembly. The APUs are fueled by hydrazine and generate mechanical shaft power to drive a hydraulic pump that produces hydraulic pressure for the SRB hydraulic system. The two systems operate from T-28 seconds until SRB separation from the ET."
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#525
by
Danny Dot
on 02 Sep, 2009 05:11
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#526
by
Jorge
on 02 Sep, 2009 05:27
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#527
by
usn_skwerl
on 02 Sep, 2009 06:40
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What is the whirring noise heard usually at about T-15 seconds? it sounds like what you'd expect the high-pressure turbos to sound like but this is much too early for them, so I can only guess its air being forced through the pipes and out of the nozzles as water runs through the sound suppresion system?
The ROFI systems powering up.
I think it is the SRB's Aux Power Units powering up. And they are turbines.
Danny Deger
SRB HPU start is T-27secs with SRB nozzle steering checks at T-21secs
I thought they started at T-19. I am certainly not a reliable source on this though, so you are probably correct. But I do recall STS-51 "aborted" at T-19 because one didn't start.
Danny Deger
"There are two self-contained, independent Hydraulic Power Units (HPUs) on each SRB. Each HPU consists of an auxiliary power unit (APU), fuel supply module, hydraulic pump, hydraulic reservoir and hydraulic fluid manifold assembly. The APUs are fueled by hydrazine and generate mechanical shaft power to drive a hydraulic pump that produces hydraulic pressure for the SRB hydraulic system. The two systems operate from T-28 seconds until SRB separation from the ET."
I thought at T-15 or so, the high pitched sound was the sound suppression system pumps kicking up, or air coming out of the waterbirds as well.
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#528
by
ginahoy
on 02 Sep, 2009 07:01
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I apologize for inserting a new question in the midst of an interesting discussion, but...
When viewing the Shuttle MCC on NASA TV, what are the narrow amber displays on both ends of each console? The ISS MCC consoles have them as well.
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#529
by
elmarko
on 02 Sep, 2009 09:26
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They are the DVIS system, essentially the voice loops that everyone listens to. You can turn on or off various ones to listen to, and then talk on those loops if required.
Actually, that's a request for L2, potentially. Is there any kind of documentation about the DVIS system? I'd be really interested, as someone who sometimes deals with audio routing and the like (we have radio studios at my university job).
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#530
by
elmarko
on 02 Sep, 2009 09:27
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Sorry for bringing up the prebank again, but surely a 180 degree prebank puts your TPS facing upwards, and the crew cabin directly into the face of hot burny firey danger?
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#531
by
GLS
on 02 Sep, 2009 10:37
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no it doesn't, the prebank it done BEFORE EI (not alot of heat there). And it's not a roll, but a banking. If alpha is positive, you can bank all you want and the bottom will still be facing forward.
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#532
by
elmarko
on 02 Sep, 2009 11:05
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
Also, I know the banking is done pre-EI, so when does it come out of the prebank after EI?
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#533
by
Danny Dot
on 02 Sep, 2009 13:32
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Sorry for bringing up the prebank again, but surely a 180 degree prebank puts your TPS facing upwards, and the crew cabin directly into the face of hot burny firey danger?
Not at all. You are upside down, but still at any alpha you choose to be at. The belly is still taking the heat, not the top.
Take the case of flying fighter aircraft. If I needed to go down fast, I would never just push over. I would roll over and pull. This way I was upside down with positive angle of attack and positive Gs. I hated negative Gs because all of the crap on the bottom of the cockpit would float up and get in my eyes. It is really hard to thoroughly vacuum out the cockpit of a fighter aircraft.
On getting the voice loops here. That would be great. They are controlled by "Houston Voice". They are a great bunch of guys to work with. Someone contact them by calling JSC information 281-483-0123 and ask for Houston Voice. My guess is they would be all for it, but others will not like the flight loop and such available to people like us. It is even closely controlled inside the center. Only "special people" have a flight loop speaker on their desk.
Danny Deger
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#534
by
Danny Dot
on 02 Sep, 2009 13:46
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
Also, I know the banking is done pre-EI, so when does it come out of the prebank after EI?
The pre-bank is taken out by the crew simply selecting "auto" roll as soon as guidance wakes up as the orbiter gets in the atmosphere and the IMUs sense drag on the airframe. Before I took over entry training, the crew manually flew out the pre-bank, but they routinely died by either not rolling at all (thus burning up) or rolling to wings level and staying there until I had to stop the sim and ask then why they wanted to back into orbit instead of completing the entry
When I told the flight controllers the procedure at the time had something like a 50% mortality rate built into it, I was told we needed to continue to use it anyway to keep the roll rates down. They didn't like it when I asked them if the auto commanded rates would result in a mortality rate greater than 50%. I did their job for them and found a forgotten feature in the auto-pilot to limit roll rates at high Mach numbers and my change to let auto fly out the prebank finally got approved.
And yes I was not happy that the flight controllers didn't take quick action when the Entry Training Flow Supervisor alerted them that an established and documented procedure had a 50% mortality rate due to crew error.
Danny Deger
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#535
by
Lee Jay
on 02 Sep, 2009 13:49
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
It might be facing the ground but it's still facing away from the direction of travel. Travel is more-or-less parallel to the ground, so upside down with nose pointing down at a steep angle still puts the heat on the belly.
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#536
by
Danny Dot
on 02 Sep, 2009 14:50
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Can someone get me the shuttle's Cl and Cd vs. alpha at hypersonic Mach numbers? I want to quantify the reduction is heat load and heat rate for an alpha 60 entry. It will not be hard with these numbers.
I am starting to think Columbia might have held together with an alpha 60 entry. She did hang in there until something like Mach 18. This is about the time she was starting to cool down anyway.
There is no way the people that invented the very effective 50 alpha high energy TAL didn't look into this. I am also very certain that these people would have instantly recommended a high alpha entry for Columbia, if they had known about the potential of TPS damage. Enough people knew about the debris strike, such information had to get the heating guys.
I can't tell the effect in that room when I asked where the alpha 60 entry data was in looking at mitigating TPS damage. It sucked the air right of me. Did somebody's dissenting opinion get quashed -- once again? I know mine did.
Danny Deger
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#537
by
Jorge
on 02 Sep, 2009 19:04
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
It is actually very easy to visualize. Take a foam orbiter toy. Shove a stick into the belly at a 40 degree angle below the nose. That is the relative wind vector. It is also the X axis of the stability axis frame. That is the key. The bank is performed about stability axes, not body axes.
Now orient the toy so that you're looking down the stick at the belly. You're seeing the orbiter from the relative wind point of view. As long as the relative wind is aligned with the stick, the proper angle of attack (alpha) of 40 and sideslip angle (beta) of zero are maintained.
Now rotate the orbiter toy about the stick so that the belly is on top and the nose is pointed 40 degrees down. That's a prebank of 180. But the relative wind is still looking at the black belly, not the white tiles.
That's the key. When you perform a "roll" during entry you are rolling about the stability axes (the stick) and not the body axes (the nose). If you rolled 180 about the body axes you'd wind up with the top (white tiles) facing the wind. But a roll about stability axes always keeps the black side facing the wind.
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#538
by
elmarko
on 02 Sep, 2009 21:12
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
It might be facing the ground but it's still facing away from the direction of travel. Travel is more-or-less parallel to the ground, so upside down with nose pointing down at a steep angle still puts the heat on the belly.
Perfect, that makes sense now. I guess I still had the idea of the flight path angle being aimed down somewhat, but of course it's not that bad.
Re the DVIS, Danny, I wasn't advocating getting access to the loops or anything, just any kind of documentation on it's use for MCC personnel, or anything that might be interesting to those of us who happen to work with audio technology.
If Chris is reading, you can consider this an L2 request, but I'll post it in there as well just to make sure.
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#539
by
elmarko
on 02 Sep, 2009 21:15
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It's really hard to visualise it.
I don't suppose anyone fancies a crack at drawing a diagram or something, because to me all I can think of is the orbiter banking past 90 degrees and then after 90 the white stuff is facing the ground...
It is actually very easy to visualize.
Oh that's a great help too, thanks!
