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
A view of our trip.
Indeed, a bit of water between Gander And Ireland.
Let's go for our journey.
Almost a CAVOK morning here in Florida. Sun slowly rising.
Lift off and roll program Houston
Almost at the end of the first stage, Shuttle trajectory is bending after the climb through the high density atmosphere layers
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
And OMS assist up to 83 % of the total OMS propellant
Approaching 20 kft/s
Second engine failure and TAL to ZZA declared ( we passed the single engine TAL boundary ie. 14 kft/s)
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
A nice view on the ET falling with us
Time for the specific procedure
Left for the Commander, right for the Pilot
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
Heating hard during the first pullout
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.
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
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
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
Mach 5, probes deployed and Nav filters implemented into the navigation soft
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
Hello Gander
Convective day, but not really the choice of field and weather after a triple engine failure
A tiny white point seen from the tower, Atlantis is now subsonic
Those forest are hyptonic, aren't they ?
Long final, a bit low on energy now ahah
My downwind leg was a tad too long
Pre Flare over the trees
And Touch after 30 mn of a terrific flight
Not too bad
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.