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FG Shuttle: Triple Engine Failure and High Energy Gander TAL

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FG Shuttle: Triple Engine Failure and High Energy Gander TAL

Postby GinGin » Sat May 04, 2019 12:54 pm

A sum up of my last sessions with the Shuttle.
I was looking for an exotic situation to work on, recoverable if possible with some smart NASA procedures.

Triple Engine failure seems to be a good one, with a TAL to Gander, but a particuliar one where we will have too much energy to let the AP fly it all along.
A bit of manual input wil be required. A nice and rewarding challenge.


But first thing first, a quick chat about 3 engine out procedures.
Up to an inertial speed of 18000 ft/ish, we would fall into contigency abort for such a failure. AP would try to minimize the falling speed into the atmosphere to have " the smoothest" entry possible.
Past 18000 ft/s, speed is high enough to transition towards a TAL and be able to do a "normal" entry to land somewhere.


On the graphic below ( 51.6° inclination launch), we can see that past 18 kft/s, some canadian Airport are accessible ( YQX for Gander, YYT and YJT)
Between 20200 ft/s and 22000 ft/s, there was a blank.
Speed too high for Gander and too low for Shannon ( INN)

That is why NASA developped a procedure called High-Energy Gander. Aim was to close the Gap between end of nominal Gander capability and the beginning of low energy capability to Shannon.
Very specific procedure for a window of 1500 ft/s of Speed.
That was specific to ISS launch to avoid excessive crossrange to Gander.
Before this procedure was developped, MECO velocities between 20.4 and 22 kft/s led to a bailout in the cold Atlantic Ocean


Image



A view of our trip.
Indeed, a bit of water between Gander And Ireland.

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Let's go for our journey.
Almost a CAVOK morning here in Florida. Sun slowly rising.

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Lift off and roll program Houston

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Almost at the end of the first stage, Shuttle trajectory is bending after the climb through the high density atmosphere layers

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Five mn into the flight, first alarm on the right engine.
We lost it, overpressure of the LOX part.
We passedthe press to ATO boundary, good enough.
ATO declared

Image


And OMS assist up to 83 % of the total OMS propellant

Image



Approaching 20 kft/s
Second engine failure and TAL to ZZA declared ( we passed the single engine TAL boundary ie. 14 kft/s)

Image



Then shortly after ( 21.2 kft/s), third engine failed.
Well into the high energy Gander zone.

To sum up, we are at 21000 km/h, 2000 km away from Gander. 350 kft ish of altitude falling at 1500 ft/s max in the atmosphere.
Not a lot of time to act and quickly do the right actions that might save our lives.

First, ET doors closure and Propellant and OMS dump after transitionning to OPS 3 software for entry

Image



A nice view on the ET falling with us

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Time for the specific procedure
Left for the Commander, right for the Pilot

Image


We are high on energy. A normal AP entry will not be enough to bring us safely at destination ( though for speed around 21 kft/s, AP is working pretty well at dissipating energy)
Idea here will be to fly manually the Entry with CSS and to take a higher than usual Angle of Attack with no bank at first ( 50 ° for us as we are below 19.9 kft/s of Earth Relative Speed)

This higher than usual AOA will dissipate quicker the high energy situation.
Vertical speed is usually between 1000 and 2000 ft/s for the first pullout


Image


Heating hard during the first pullout

Image



We are still way above the profil and far right from Gander.
Vertical Speed is decreasing. Time now to bank to catch a specific descent rate and to decrease our Delta Azimuth with the field
When vertical speed reaches -800 fps, we roll the vehicle left towards Gander with the same AOA of 50 ° initially.
Then we hold 3 G's ( -350 fps roughly of vertical speed)
That is why AP can't really properly fly it for really high energy situations ( max G's for nominal ops is 2.5)

We have to stay below 3.5 G's. So manual skill will require there to play with angle of attack and bank to control the catch up rate and the G number ( linked to the vertical speed)
Basically, we hold 70 to 80 ° of bank towards Gander and we slowly decrease the angle of attack to maintain 3 G's ( pull on the stick to decrease the load factor and vice versa)
But if we decrease it too much, it will produce a too high thermal stress on the Orbiter. A kind of win-win situation with life in the loop.

So it would have require in real an excellent coordination within the cockpit to stay within that thin layer of acceptable parameters ( G below 3.5, Nose Temp below 3000 °F and EAS below 470 kt)



Here in game, -800 ft/s and increasing, bank to the left, 3 G holding by decreasing AOA.

Image



An example of tricky situation below.
Thermal stress Ok, G's also ( 2.6) but EAS really high due to AOA which is too low.
That would have required an increase of AOA by pulling on the stick
Quick and smart visual circuit to develop there :)

Image




Back to our entry.
Once the Orbiter is reaching a Nominal entry path ( back on the curve), we can switch the AP back to ON.
The high energy state is dissipated, and AP can fly the rest of the entry nominally now.
It can happen anywhere from Entry Traj 2 to Entry traj 4 for the highest MECO velocities ( 22 kft/s)

Traj 3 for us

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Entry is then a well known thing, less exotic.
Scenics are breathtaking in that part of the world though.

Arrival over the Far East of Canada


Image

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Mach 5, probes deployed and Nav filters implemented into the navigation soft

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HAC in sight, quite high.
Fortunatly, we have a lot of room to extend a bit the downwind before coming back on the final axis to bleed extra energy during TAEM

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Hello Gander

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Convective day, but not really the choice of field and weather after a triple engine failure

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A tiny white point seen from the tower, Atlantis is now subsonic

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Those forest are hyptonic, aren't they ?

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Long final, a bit low on energy now ahah
My downwind leg was a tad too long

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Pre Flare over the trees

Image

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And Touch after 30 mn of a terrific flight

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Not too bad

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Another amazing exotic situation to test in that sim
And that works nicelly.
Always interesting to follow Nasa procedures and see working effects in game.

I tried a lot ot High Energy situtations.
Those close to the boundary at 22 kf/s are really a thing with almost no room for mistake during the first step of entry.

A really rewarding scenario.
I still think that those exotic situations would have been really tricky in real.
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby Johan G » Sat May 04, 2019 2:28 pm

I really enjoy the reading and the screenshots. Thank you! :D
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby Thorsten » Sat May 04, 2019 5:09 pm

Sweet... I wouldn't have taken the bet that the thermal stress modeling is up to the task of flying with a higher AoA without additional tweaks (the AoA dependence is pretty much a guesstimate), but the lower initial velocity of course helps.

I've never tried the marginal TALs much, seems to be an interesting exercise. 8)
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby wlbragg » Sat May 04, 2019 5:25 pm

No tiger stripes on the fuselage is a good sign as to how well you managed the high energy during the reentry.
Makes you wonder how many time a pilot/commander performed that same simulation in their simulators?

As always, a very educational and motivating story.
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby GinGin » Sat May 04, 2019 5:57 pm

Thanks guys. Glad you like it, I had tons of fun.


I wouldn't have taken the bet that the thermal stress modeling is up to the task of flying with a higher AoA without additional tweaks (the AoA dependence is pretty much a guesstimate), but the lower initial velocity of course helps


Thermally, it works well if the first pullout is respected with no bank or no delay in it ( 2800°F) max.
I tried with a bit of bank towards Gander and 55 ° of AOA, it was glowing a bright orange at 3500 °F


But yes indeed, Low initial MECO speed helps here, and limitating factors are G/EAS when trying to dive too fast into atmosphere for a really high energy one ( at 22 kft/s of Vi, it becomes really tough, better to bailout and let it over)



I've never tried the marginal TALs much, seems to be an interesting exercise


Yes, really educative.
Also the High energy TAL ( past 24 of Vi) is pretty interesting with a 180 ° of Pre Bank.
And it is really well explained in the Ascent/abort Handbook.


No tiger stripes on the fuselage is a good sign as to how well you managed the high energy during the reentry.


Ahah, I had a lot actually.
I didn't have time to take picture during the TAEM, so I loaded a final approach scenario with a clean Shuttle for the pictures :mrgreen:


Makes you wonder how many time a pilot/commander performed that same simulation in their simulators?


Not so much for those kind of aborts.
It was really situationnal and unexpected.
It would require a triple engine failure really between 21 and 22 kft/s ish.

Reading behind the lines of Handbook, no more than one or two sims about those marginal stuff. I guess that is why the checklists are so detailled with all the actions in it
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby wlbragg » Sat May 04, 2019 8:12 pm

Ahah, I had a lot actually.
I didn't have time to take picture during the TAEM, so I loaded a final approach scenario with a clean Shuttle for the pictures :mrgreen:


Well, that explains it.
So what your telling me is a picture isn't always worth a 1000 words, or even a sentence. :lol:
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby eatdirt » Sun May 05, 2019 2:56 pm

Another fantastic adventure, well done and thank you!
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby GinGin » Wed May 08, 2019 9:47 am

Thanks , back to Earth in one piece but a bit fried :)
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby ORZMUD » Wed May 22, 2019 6:07 am

Great narrative!
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby GinGin » Fri May 24, 2019 3:33 pm

Thanks Orzmud.
I had a lot of fun doing that and the research to be as close as possible at what reality would have been :)
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby TheEagle » Fri Jan 14, 2022 8:11 am

Very nice ! :) And "guesstimate" is my favourite word from today on … :mrgreen: Sadly I can barely do any Shuttle flying … my PC just about allows it at 5 to 10 FPS, but the Canvas SVG loadings take half an hour for me :cry:
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby Hooray » Mon Jan 17, 2022 6:00 pm

TheEagle wrote in Fri Jan 14, 2022 8:11 am: but the Canvas SVG loadings take half an hour for me :cry:


that has been previously discussed, and we talked about a number of potential improvements - it's affecting other aircraft, too:

Subject: SVG parser performance (from Cessna C182T)
stuart wrote:I had a quick chat with James about this. We suspect just shifting more of the svg.nas code into C++ would provide good enough "bang for the buck" to improve the load time without needing anything more complicated.



So, if you care about this, please file a ticket at the issue tracker: https://sourceforge.net/p/flightgear/codetickets/

For some background info, please refer to:

Subject: SVG parser performance (from Cessna C182T)
Subject: Update to canvas API and SVG parser
Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
Thanks & all the best,
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby Thorsten » Tue Jan 18, 2022 7:17 am

but the Canvas SVG loadings take half an hour for me


You realize there's a startup option to only load three screens rather than all of them - that's usually enough to fly and loads quite a bit faster.
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby TheEagle » Tue Jan 18, 2022 9:01 am

@Thorsten: no, thanks for the tip - how do I enable that option ? :)
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Re: FG Shuttle: Triple Engine Failure and High Energy Gander

Postby Thorsten » Tue Jan 18, 2022 11:57 am

Look into the Manual, I don't remember this by heart.
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