Space Shuttle - STS 62 A Polar Express high altitude journey

[GinGin]

I decided to go for a long haul mission with saves and resumes to go through all the nominal operations that we can accomplish with the Shuttle.
Seeing the last screens from EatDirt and Thorsten, I wanted to go high both in inclination and in altitude, at the limits of what would have been the Vandenberg Department of Defense missions.

I chosed to try to replicate STS 62 - A, which would have been the first Polar Mission from Vandenberg in 1986.

https://en.wikipedia.org/wiki/STS-62-A
https://www.nasaspaceflight.com/2005/12/sts-62a-the-polar-express/



A veteran crew with Robert Crippen as Commander




Part 1: A tough journey began with thorough preparations

First challenge was to set up a proper mission file to have some reliable insertion parameters and intact abort sites.
A bit of inter/extrapolation here and there from SCOM performance chapter datas.
No need to say that the Final Performance Reserve which is usually around 15000 pounds of LH2/LO2 (1%) will not be met there





Parameters chosen

Payload: 33000 pounds (Spartan as a small spy satellite and 30000 pounds for the OMS kit offering 1000 fps of extra Delta Velocity ( https://cp3.irmp.ucl.ac.be/~ringeval/upload/spaceshuttle/PBK/shuttle_perf_with_omskit.pdf)
Orbital Insertion Parameters: : Inclination 80° / Apogee 320Nm / MECO flight path angle 1.35° / MECO Inertial Speed 26125 ft/s / OMS assist of 60 seconds ie. 120fps // Throttle up at 109%
Abort Sites: Vandenberg for RTLS, Easter Island for TAL, Edwards for AOA
Insertion OMS burn: OMS 2 000/00:40:00.0 / 800fps / Orbit 500 x 320 Nm




Sun is rising up above California, strong storm let the area wet and humid with no smog at the horizon




Hold of 10mn is over, no complications, MCC gave the Go for Launch and the 9 mn countdown starts




Commander Crippen watches the last ground crews leaving the launch tower, letting them alone with their 800 tons of explosives




Go for APU start, pressure is rising , nominal hydraulics at 3000 PSI
Soon the nozzles gimbal check will make the Shuttle shake from all its bolts and nuts.




Time now to close the Sun visor, and to see the life a bit brighter





MPS ignition soon followed by the 6000 kilopounds produced by the two SRB





Let's aim South Commander




In the bucket, pressure is building up fast and our negative AOA will alleviate the strong load from the wings





The thrill of the 2 first minutes is now over, going from 3 Normal G's to 1 in a few seconds : SRB sep




The two engines TAL boundary is now reached, Easter Island might welcome us in case of an engine failure







The rest of the ascent is uneventfull, Main Engine Cut Off (MECO) time with 0.2% of propellant remaining.
MECO parameters are optimal, and a quick check on the BFS System Management tells us that Freon is cooling normally the Shuttle (53°F)







Post MECO MCC analysis: Nominal post MECO Orbit 323 x 31 Nm with a near perfect 80°of Inclination
No underspeed, we can proceed with OMS2 actions.




Let's secure the APUs and reactivate the Heaters for Flash Evaporators feedlines ( Heavy load on ac buses, hence not enabled during ascent to avoid shortcut)
The AC bus sensors are moved to Auto Trip, important step there. In case of AC overload, the affected AC bus will be from now automatically disconnected to avoid further damages.




OMS 2 is uplinked from the MCC.
8 mn of burn, and Time of Ignition ( TIG) set up 4 mn before Apogee : 22 mn remaining.
800 ft/s to add by pushing in our Prograde Vector, almost all the OMS kit reserve.




Some more unpowering actions to unload the Fuel Cells from unnecessary devices.





Preparation of the OMS feedlines.
Crossfeed valves activated to use first the OMS kit ( better to spare the aft pod OMS in case a RCS X-feed would be needed with a Low RCS propellant condition for example)





50 Shades of white while coasting trough our burn window




Splendid Antartica




Stunning Mission Specialist rear view





Burn time, and intense monitoring during those 8 minutes with all the displays available






Post burn analysis, no need for RCS trimming.
505 x 324 Nm for the Orbit and 1100 fts of delta velocity remaining





We start the Post Insertion fastidious checklist while crossing Madagascar




The important GPC OPS transition, to get rid from Ascent/Insertion Softwares and transition towars another batch of Orbit softs.




Payload Operations





OMS 3 burn over Alaska to rise our Perigee up to 460 Nm.
That will leave us with 900 ft/s remaining from which we need 750 ft/s to Deorbit.
We will have a 150 ft/s to play with later




Time to get out the Cameras for those breathtaking Hadley Cell Thunderstorms




or that Aurora Dust






Meanwhile the pilots are busy to take care about heaters thermal management




Four hours into Orbit, and already time to take the first rest in the lower mid deck





Part 2: First observations and routine checks

After a short nap of 1h30 mn, everyone is on the Main Deck again.
Almost 6 hours into the mission, lightings are adjusted and screens brightened



An almost endless day at that Inclination, Day and Night, Angels and Demons in a single view.




Some documentation refreshers before further operations




Mission Specialists work on their Payload deployement checklist while admiring the Earth Lung






Fuel cells have been purged and IMU's aligned.
Approaching 10 hours, time for another OMS adjustement to circularize the Orbit.

Left picture: before the OMS burn, 70 ft/s of Dv at next Apsis
Right picture: OMS burn monitoring.






We are now on our final Orbit, 516 x 505 Nm after 26400 pounds of Ergols spent into the vacuum.
Remains on board 830 ft/s of delta velocity capability.


Time now for the real sleep event, and next action during Flight Day 2 for Payload Operations

[wlbragg]

That last image is compelling. Or maybe your psychic!

[wlbragg]

Do you have some code for the light or is that a doctored image?

[Thorsten]

Looks like flashlight pointed at the spot (?)

[GinGin]

Do you have some code for the light or is that a doctored image?

It is your flashing light in the dark indeed
The only doctored image is the one with the Sun Visor at the beginning.

[GinGin]

First post updated with today small events

[eatdirt]

Beautiful , I am always learning things when reading your missions! Thank you!

[GinGin]

Part 3: RMS awakening and malfunction management


Almost 16 hours into the mission when the crew is awaken by a strident class 2 alarm with a red Master Caution warning and a light on the F7 Cautions and Warnings panel.
A massive Storm is in action right below the tiny Shuttle, at the other far side of the world.




The Master Caution and associated alarm are cancelled by the Commander, and the faul messages are analyzed.
It means a lower than normal voltage on one fuel cell and its associated Main DC Bus (1/A)




That might mean a lot of things.

We first tried a Main Bus Tie like directed by one of the Orbit Pocket checklist. That will allow to have the extra load leading to an undervolt on the fuel cell 1 to be splitted.
That seems to work, FC volt 1 is a bit higher and the load is shared with the fuel cell 3




To go even deeper to know from where is coming that extra load that causes an undervolt, we can go through some more extensive investigations.
A big book is available in Orbit, the Malfunction (MAL) book which allows to go into some details with some simple conditionnals to follow , even within FG for some of them that are simulated.

Left Side of the left picture, the alarms we had S67 Main V S69 FC Volts and the Backup C/W Alarm. We have the good initial conditions then to entered in that non-normal check list.

1)FC Shutdown (NO) --> 3)FC Volts and Main Bus volts below 28 V (YES) --> 4)FC and Main Bus are within 1 V -- > Step 13: Affected bus was not tied before the Low Volts alaram (NO) --> Step 15

Right picture for the step 15 onwards

15)fuel cell amps > 360 (YES) --> 19) Affected fuel cell is not connected to payload bus (NO) --> Step22: we perforem a power down ( load shedding) to find the culprit --> Final verdict: step 29 Excessive FC Loading





And indeed, I actually made a small mistake with the recirculation hydraulic pumps that are heavy on electrical loads.
I put them on all the time instead letting the computer activating them when it was needed.

Back to the GPC position then, and we decrease the total AMPS from 550 to 450 with no more overloads/undervolts in affected FC





Time to continue with more normal operations.
After some preparations and warm-up time, Mission Specialist starts his lengthfull procedures to awake the Canadian Arm and perform checks on it once unberthed from its stowed position.




We can see the RMS through the Pilot seat




Checks are sucessfull , and the RMS will be soon required to do much more




A quick glance to our recirculation pumps, that now are activated just when needed as expected ( here the number 3)




We can start to proceed with the RMS operations for Payload unberthing.




But before, the Mission Specialist will need to read another time the manual

[GinGin]

Part 4 : Payload and Proximity Operations

Finally time to unberth the small spy satellite.
Funny enough, we are just overhead our Launch base, California under storms




After a bit of RMS manoeuvring, the Lacrosse Spartan satellite is grappled and ready to be unlatched





Payload rentention latches are released.
We can follow that operation under a System Mangement Display page, Spec 97 Payload Retention.




Overhead Groenland's Glaciers




Spartan is now released, and we have to switch the logic frrom a Payload object to an Orbital object to have some relative motion informations about Spartan (If we want to perform a Rendez Vous later on, proximity operations don't require that)
A bit of relative position insertions in the save file, and we have something quite coherent.

On the left, a bit behind Spartan (5 km) with a negative catch up rate, same inclination.
On the right, position two hours after Spartan was released, 135 km behind her now




We have a very thin propellants margin to play with ( we need 80 % of propellant to deorbit)
A small phasing burn of 15 ft/s to decrease the Perigee by 10 Nm, from 501 to 491Nm
That will almost null our catch up rate with Spartan allowing us to maintain a quite steady position over time 150 km behind her.

On the left, burn in progress.
On the right, burn results.




Time now for some rest before the next events.



Part 5: Deorbit Preparation


One of the last Sunrise for the crew, over Siberia.




Overhead the main Headquarters, Florida down there. Not for us today, we are aiming towards the inconspicuous Edwards AFB lakebed complex.





Deorbit preparations have been started 4 hours prior to perform the Deorbit burn.
The full thing there: https://wiki.flightgear.org/Flying_the_Shuttle_-_Deorbit_Burn_and_Final_Entry_Preparation_Advanced

Deorbit burn datas have been calculated by the Mission Control Center.
PEG 4 guidance converged well.
800 ft/s to loose to decrease the Perigee to 20 Nm (8mn of burn)
Range at entry interface of 4397 Nm and cross range of 700 Nm.

Time of Ignition forecasted at a Mission Elapsed Time of : 1Day 23 Hours 12 Minutes 48 Seconds
The purple square represents the entry flight path targeted by the PEG 4 guidance, at the limits of the flight envelop.





2 hours before the burn.
Purple arrow indicates our present Orbit. Blue arrow indicates the one where we will be in entering the atmopshere, banking left to steer towards Edwards and decrease the 700 Nm of cross range.
On the right, we can see that strange relative motion plot. As targeted by our earlier phasing burn, our position is almost constant ( slightly retrograde) regarding Spartan ( Our total Orbital energy is still slightly higher)




Fuel Cells purge, a lot of contaminants in there as I overlooked that procedure for almost 2 in sim days.
Hence some low voltage alarms due to bad FC performances

Left before Purges, Right after. Day and Night.





Cold Soaked Freon Procedure.
Freon stucked in the radiators is over cooled for a short while; to be used later during the entry for additionnal cooling when the Flash Evaporators will be inefficient.




Payload doors closing




Another extensive GPC reconfiguration phase, to transition from Orbital softwares to Entry softwares.
Each GPC from 1 to 4 drive some critical strings, essential to have a feedback from all the datas that will be used by the Guidance, Navigation and Control softwares.
GPC 5 as usual is the ugly duckling working alone; and carrying the Backup soft in case of major failure of the former GPC.




Finally, we check the good health of the IMU's.
Star Alignement using two Stars which the inertial positions are known. A good angle between them ( 82.1° there) is mandatory to have one of them in each Star Trackers.
Real known present position of the 2 Stars is compared to the current position given by the IMU (where the IMU's think the Stars are), and the deltas between those two positions are nulled.



Good to proceed then with the final Entry preparation ( in Yellow) 45 mn before the burn

[GinGin]

Part 6 : Deorbit burn and final Entry preparations

Almost at the end of our journey, but still some intense phases to come.

We received from the MCC the final datas for our Manoeuver Pad. It contains all the datas that we should see in the Deorbit manoeuver page ( Major Mode 301 then 302)

-Two OMS burn.
-The payload bay facing the Earth ( Thrust Vector Roll of 180°)
-Trim settings for the OMS nozzles ( Pitch 0.4°; Yaw +/- 5.7°)
-Weight of 216000 pounds
-TIG : 001/23:12:49
-PEG 4 parameters that will output the more readable prograde and radial speed values we talked earlier
-Burn attitude
-Entry Range estimated (4400 Nm)
-Time between Deorbit Burn and Entry Interface ( 33mn )
-Total velocity to lost ( 804 ft/s)
-That velocity decomposed on the Shuttle body axes frame ( OMS nozzle are mounted with an angle of 15° regarding the X body axe, hence a component on the Z body axe of 25% * Total velocity)
-Targeted Apogee (511) and Perigee (021) after the burn





Datas are then entered in the computer, outputting something coherent with what we received earlier on.
The Entry Interface distance REI (5706 Nm) is disregarded there, not as relevant as the one we had with MCC computation tool for long duration burns.



We check our targeted airfield and the associated charts





Let's highlight another important cue card that will help the crew in case of OMS malfunctions.
It is called the Deorbit Entry Landing Preliminary Advisory Datas (DEL PAD).

First the part for the Pre-Deorbit and Deorbit burn.

Pre-Deorbit

APU start strategy.
Before the deorbit burn, one APU is started to be sure to have some hydraulic pressure for flight controls during entry.
There, we will try 2 attempts, APU 1 then 2.
If it does not work, we will delay the deorbit burn to have a new deorbit and entry strategy ( contigency one probably)

Deorbit

The aim here is to have values that will help us to know what do to in case of an engine failure or a propellant leak or a double engines failure during the Deorbit burn.
Should we continue ? Should we stop ? What are our propellant margins ?
A kind of decision point cue card ( like several V1 speeds in aviation, before we stop , after we continue in case of engine failure during take-off)

I will go briefly line by line.
Everything is deeply described there in case you are interested: https://gandalfddi.z19.web.core.windows.net/Shuttle/JSC-11542%20-%20Flight%20Procedures%20Handbook%20Rev%20E%20200504.pdf

*OMS TIG SLIP: It means that if we miss the TIG for the burn, we can extend it to a max of 5 mn passed that time without degrading our Entry.
*RCS Downmoding: If we decide to Deorbit using the aft RCS, we can extend the TIG to a max of 2 mn passed the initial TIG time

*Stop/continue Cues

We can loose an engine for two reasons: a proper failure ( ENGINE fail) or a leak (PROPELLANT fail)

-Engine fail is "easy", we finish the burn with the good engine/RCS and we can use all the propellant available in the engine failed Pod with a cross-feed.

-Propellant fail is a bit more tricky. If a prop pod leaks, we loose its ergols, hence a delta velocity capability.
We then have to decide if we stop the burn, or if we continue ( enough propellant remaining in the good OMS + afterward RCS + Forward RCS pods to reach the targeted Perigee).

The limit where we have to decide is expressed in terms of height of Perigee (HP) when the leak starts and that we declare a propellant fail condition.

For our scenario, that propellant OMS fail HP ( same for Left and Right OMS as we have the same initial ergol quantities) calculated is 398 Nm, I spare you the computations.
If a leak is declared before our current Perigee reached 398 Nm, we stop the burn. We will have to recalculate another entry angle with a shallower entry flight path in order to use less velocity during the burn ( plus some special procedures for low entry angle atmosphere capture).
If a leak is declared after our current Perigee reached 398 Nm, we can continue the burn on one OMS, then use the aft RCS up to a certain quantity (30% intially to have some RCS fuel during entry), then use the forward RCS to reach the targeted Perigee.


Eng fail and safe HP next to double failure are for double OMS engine failure condition.
If both engines are failed without propellant leakage, we can use all the OMS prop with the aft RCS via a cross-feed. Hence the Eng fail HP of 500 Nm ( the double failure can happen at the start of the deorbit burn and we can continue with a RCS only deorbit).

If both engines failed and there is at least one OMS pod with a leakage, the boundary is the same than the propellant fail scenario ie. 398 Nm. Only difference is that it will be a RCS only deorbit without transitioning through the single OMS burn phase.


*Tot Aft Qty 1 (%) : the minimum Aft RCS quantity we want for a normal Entry ie. 30 %
*Tot Aft Qty 2 (%) : the minimum Aft RCS quantity we want for a No Yaw Jet Entry ie. 10 % . That would give 20 % more aft RCS prop to be burned in case we need some extra delta velocity for contigency procedures ie. 20 ft/s ish or 10 Nm of decrease in the Perigee.

*PreBank/Flip HP: 33 // Aft HP: 29 // B/U Site: NOR (Boundaries for RCS deorbit burn)

Our nominal targeted Perigee is 20 Nm.

We can extend that one to 33 Nm in case of severe off-nominal conditions (13 Nm mean a decrease of 25ft/s ish from the total velocity needed to be lost).
We will need to PreBank the Orbiter during the first part of the entry up to 130 ° to have a Lift vector that will steer us initially downward ( Perigee too high, Entry angle too shallow conditions)
The "Flip" word means that either we stop the burn at a Perigee of 33 Nm (and do a prebank ), or we continue with a forward RCS deorbit burn up to 20 Nm ( we flip the Orbiter to use the fwd RCS thrusters if prop is available there)

Aft HP is a boundary where we can continue with an aft RCS deorbit burn up to the nominal targeted Perigee if a failure occurs below 29 Nm of current Perigee ( we get rid of some extra reserves, a kind of really commited to deorbit thing)

Back Up stands for a diversion field in case of last minute changes after Deorbit burn occured, due to too high Perigee or Weather related things.
Here, it is NOR ie. White Sands AFB

*FRCS dump: Not used for our scenario. That would be a fwd RCS dump post deorbit burn for center of gravity considerations ( forward CoG)







Start of one APU 5 mn before the burn like mentionned




Let's proceed with the burn then
On the right checklist, you can see the boundaries and procedures that we described above





8 mn to go





Burn was nominal.
10% of OMS propellants remaining ( 100 ft/s). We have been on the safe side.
Targeted Perigee within 2 Nm of current one, no need for prebank procedure // Initial flight path should be nominal




The center of gravity is also nominal, and we have now a coherent Entry Range displayed








We secure the OMS valves, all the RCS valves are opened.





Hydraulic pumps and remaining APU's are switched on a few minutres before the Entry.
SSME nozzles are moved in the correct position to allow the drag chute extension later on.




A final check of all the switches before going for the big dive

[wlbragg]

This is really fascinating, and so much appreciated, thank you!

[GinGin]

@Wlbragg: Glad you appreciate the journey, I really enjoyed that trip.
Big dive soon

[GinGin]

Final Part: Entry and Terminal Area Energy Management


A few minutes before reaching the Entry Interface at 400 000 feet.
Time to review one last time the last cue card from the DEL PAD we talked about.

Entry/Landing

Easier to read through than the deorbit cue card. We have some relevant informations about the different steps of the Entry first, and gliding TAEM phase then.

Entry

*EI LVL ATT: Initial Attitude of the Shuttle in the Local Vertical Local Horizontal frame (Similar to an airplane PFD) // 40 ° of pitch up ie. Angle Of Attack
*MM304 PreBank: PreBank value we saw before in case of too high Perigee after deorbit burn // Not needed.
*Altm Set: QNH at Edwards
*CLG Init: Cloosed Loop Guidance initialisation // When Drag is greater than 3 ft.s² (5 mn after Entry Interface usually), Entry guidance kicks in to manage the Drag required vs Distance profile.
*VREL 1st Reversal: Earth Relative Speed at the moment of the first roll reversal

TAEM/Landing

*XCG at TD: Center of Gravity at Touchdown
*Land Site / Rwy: Land site number in data base for spec 50 (90) and Runway selection ( 23 left lakebed)

*L / R OVHD/ STRT / MLS / TAC

All the informations relative to the HAC we will fly
For us: left overhead HAC of 220°, MLS frequency of 8 and main TACAN frequency of 111X (used for Nav filters and state vector accuracy)

*Max Nz / Nz Limit: Max radial G's that we should experience (1.6G during HAC turn / 50° of bank) and Max G's allowed for guidance (2.2 G's during pullout to decrease speed before HAC)
*Aimpoint Nominal (7000 feet before the runway for the Pre-Flare)/ Speedbrakes Nominal setting at 3000 feet ( they should retract to 20 % during Flare prior to touchdown)





400 kfeet.
4500 Nm to go, Inertial Flight Path Angle of 2° like forecasted by datas and LEO tool




Closed Loop Guidance initiation.
Some new cues appear on the Entry display showing the Shuttle at the top right.
3rd Line by starting from the left is the nominal Entry line that will be targeted by the guidance.




And we start to descent through the Atmposhere upper layers.
Speed decreases and plasma starts to show up while we are flying towards (or through) an Aurora.




An usual arrival corridor, and a good occasion to do some sightseeing above Alaska's coast.





A tiny alarm rings, SM alert for an APU.
APU is a bit low on fuel ( below 35 %) as it was started earlier compared to the two others. Nothing anormal there.




50 Shades of Entry displays.
A sum from the entry corridor we followed through those archaic greenish displays.
From 26000 ft/s to 2500 ft/s, from 4500 Nm to 60 Nm at TAEM interface.
Guidance did the job.




Edwards and its sandy environment is now visible




TAEM transition ,another batch of softwares take the relay.
Some different energy management and another lateral and vertical guidance are expected.
As forecasted by the DEL PAD cue card, we are aiming for a Left Overhead HAC for runway 23.




Ten seconds before entering the HAC, we have a countdown cue going from right to left ( as we are going to do a left turn in the HAC)




Into the HAC.
Small changes in the display. Lateral crossrange at the top of the Spec 50 and bottom of the PFD. Vertical deviation at the right of both Spec 50 and PFD.
A lot of cues, we can't miss the runway.





On final now. Scale on the lateral and vertical ladder is tighter.
Guidance worked well, we are 7 Nm inbound at 12000 feet QFE (19° path)
Let's focus.




2000 feet Pre Flare and Gear is armed.
300 feet Gear Extension on the 1.5° final path.
We can see the 20% Speedbrakes setting as forecasted from 3000 feet until Touchdown




Touched and wheels stopped.
Neither a kiss landing nor a firm one.
After two days in Space, that will do it.