Author Topic: Flight Gear Space Shuttle Simulator  (Read 4103 times)

Offline Gingin

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Flight Gear Space Shuttle Simulator
« on: 09/23/2017 06:16 pm »
Good Afternoon to everybody.

I Have been a Space Shuttle enthousiast for years now , like a lot of you I guess. And I wanted to talk to you about Flight Gear and its Space Shuttle Simulator for those who don't know.
I played a lot to SSMS 2007 and Orbiter, then I discovered a few months ago Flight Gear Simulator, a kind of free and collaborative flight simulator available on Linux, Mac and Windows.

Here the link to Flight Gear :
Here to learn more about the heart of the project:

One project that had some very talented developpers was to reproduce the Shuttle, its systems, behavior and flight model
Started in 2015, the project is now reaching a mature phase, with a lot to do in a very realistic ( graphic and physical wise) Space Environment.

Here the Wiki page to see the work:

Main Forum page:

And some infos here how space environment was created in a Flight Sim:

It is really a " True" Simulator of the Shuttle, by true I mean that a lot of public and officials data from Nasa were injected into the Flight Model.
You can experience over G's, Over EAS or Over Temperature leading to destruction.

Here you can find a Launch tutorial using real Flight Data Files, from T-9mn until Post insertion actions, to see how close to Nasa procedure we can go

It is not a Mission Simulator, but you can create your own realistic scenario to reproduce a real mission, with limited payload.

You can also start everywhere on the Earth, to see the effect of a Polar Launch or  a high altitude launch in Quito performance wise  for example ( educationnal purpose,..)
It's a Golden Mine for Shuttle lovers.

Pretty much every systems are modelized and work together ( Electrical, Thermal, Environmental etc)
You can experience dozens of failures ( APU/ Fuel Cells/ Freon Loop,GPC,IMU, ...)
All the aborts (intact and contigency) are available and Autopilot well modelized, you can try a RTLS or a Contigency abort 2Engine Out Green to the Bermuda.
DPS implementation covers almost all the OPS (, both GNC and SM functions, and BFS as well.
Proximity OPS with ISS are also available, with Good use of Star tracker and RR Radar like in real, really demanding to stick by the book to a real TORVA :)

It's truly amazing how usefull becomes Nasa Workbooks with this simulator :)

Some more In Game High lights.

A morning Launch in Florida

Shadows and light game

The working office

Same but fully lighted

Aurora Borealis at 500 kfeet

On Orbit view with HD Textures

Bay lights warming up,

Some GPC work for OMS burn

System Management Major Function, almost every parameters work. Not activating cooling via FES or Radiator can lead to Systems overheating and destruction.

Houston we got a problem, OPS 6 and RTLS guidance

OMS to RCS interconnect and dump, all AFT RCS firing at the same time to dump OMS Tanks, very realistic

Or if you prefer, TAL Abort is also available

Houston, we got a real problem
Dark Cockpit after loss of two main buses 3 minutes after lift off, which led to one Engine Shut down, Engine Lock up, Electrical re organisation and shedding, and RTLS abort.

One thing that I love is the implementation of a realistic State Vector that can degrade over time if IMU are not align or Filter are not used.
I tried it during entry, no Kalmann filter ( TACAN, MLS, GPS,..), State vector degraded a bit and guidance was not optimal, you can see on the HUD where the Shuttle thinks the runway is, and where the runway really is.
Note that during, Voice update from MCC are available to fix the State Vector early on.

Let's finish with some TAEM and Landings
You can try Official,  Emergency and whatever landing sites you wish.
Calm, Stormy or Foggy conditions/  Head, Tail or Crosswind winds, no limits to your imagination :)

Here at ELS Eastern Island

Breaking the Storm at Honolulu

More conventional one at KSC

Night landing with Touch Down Zone Lights.

Space Sunset

Hope you enjoyed this small show off of what is possible to do with this sim.
Don't hesitate if you have further questions :)

« Last Edit: 09/23/2017 06:27 pm by Gingin »

Offline Rocket Science

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Re: Flight Gear Space Shuttle Simulator
« Reply #1 on: 09/23/2017 07:06 pm »
Welcome to the forum, mind blowing first post! 8)
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator, Vintage auto racer

Offline Gingin

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Re: Flight Gear Space Shuttle Simulator
« Reply #2 on: 09/24/2017 11:15 am »
Thank you Rocket :)

Offline ZachS09

Re: Flight Gear Space Shuttle Simulator
« Reply #3 on: 09/24/2017 05:55 pm »
Quick question:

Is it possible to set a random date and time on the scenario file like Orbiter?
« Last Edit: 09/24/2017 06:11 pm by ZachS09 »
Because the Falcon Heavy Test Flight was successful, it has inspired thousands of people to consider changing the future of space travel.

Offline Gingin

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Re: Flight Gear Space Shuttle Simulator
« Reply #4 on: 09/24/2017 06:19 pm »
Hello Zach,

Yes you can change the date and time in game.       

Probably possible via mission / scenario file also

Offline Gingin

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Re: Flight Gear Space Shuttle Simulator
« Reply #5 on: 09/26/2017 11:54 am »
Some updates.

A copy a full scenario I ran 2 months ago with electrical failures during first stage leading to collateral failures and RTLS.
Quite very realistic  :)

I tried a nice scenario, some failures with Fuel Cells and Main Buses, very interesting. I had a look to non normal checklist concerning those kinds of failures, quite time consuming, but interesting to have an idea of what need to be done and what system will be concerned by associated Buses.

Basically, a loss of a main Bus will lead to a shutdown of the associated Fuel Cell later on. Some Bus Tie are available to link a Good Bus to the bad one and provides power like if nothing happened. (  1 Fuel cell powering 2 Main Buses)

Consequences of the loss of a main bus will have impact also on AC Associated bus, which can impact SSME and APU powering ( double redundance "only", not triple like systems linked to Essential bus)

So loss of main is almost negligeable, loss of two begins to be critical and decision making will be essential.

Let's start our journey, by a warm evening on the East Coast, almost no clouds in the sky, beautifull sky and some Altostratus waiting to be ripped off by the Shuttle.
Launch was delayed by some false warning indications now cleared.
Final countdown begins, final adjustement are made, APU starts and IMU pre  launch alignement are completed. PASS software transfers his State Vector to the Backup System, let's hope it will not be activated.

A view from camera 1, everything looks good so far,

View from the pilot side is quite astonishing, let's have a good deep breath before the stress of the 3 G's

T-6 s, SSME ignitions, nominal thrust reached, SRB activation, We have a LiftOff.

Everything is looking good, bucket is approaching and maximal dynamical pressure is now Behind.
Master Caution comes alive, Main Bus Undervoltage, AC Voltage, and some Black MDU, Let's have a look to the SM BFS System page

All right, seems we have some issues with Main Bus A, FC 1 is still alive, and AC 1 is lost so far. MCC confirms our diagnostic, but no rush, everything else is looking good, no abort so far.
Most of the systems have double redundancy, some even triple redudancy.
Let's have a look and reconfigure the systems that are working on MnA or AC 1.

Some concerns about Avionics Bay one fan which are working on AC 1, temperature is rising.

Let's switch it on AC 2, Temperature is decreasing now, good.
Next move will be a BUS Tie on MCC call ( it's normally not recommanded before MECO, but you know curiosity...), we gonna connect Main B to Main A, switching off AC 1 and inverter switches before Cross Tie and putting them back then.

It seems to work, MDU are back, and MnA and AC 1 are alive again, taking load from  FC 2

Everything is back under control, everyone is sweating, and SRB separation happens, we are 2 mn10 sec into the flight.

And here we are again, the worst case scenario is happening, another Master Caution Alarm and blank MDU. What now? Cockpit is looking dark and stress is rising.

Let's have a quick glance on SM page: Main A and B, AC1 and AC 2 are lost, Essential Bus are still showing good voltage due to triple redudance.
FC 1 and FC 2 are shutdown as per Checklist, and no Bus Tie available.

Fuel cell 1 and 2 secured in Off position

And to top it all, as we lost two AC sources, two controllers of one engine are lost, so is the engine  and one APU is also lost, Phew. Situation is rapidly degradating

Here are the SSME controllers, we lost AC 1 and AC2, so center engine is lost

Also, on SM page we can see that APU 1 is out of service, which means a thrust lockup on center engine, hopefully, no lock up on available engines.

So we are approaching 3mn40, MCC took a decision between RTLS and TAL , two Main Buses Down mean a RTLS, It's a highly time critical failure, no time to cross the Atlantic and to wait for a complete Electrical failure.

Commander took time to select the correct Abort Mode, here we are, abort initiated and OPS 6 is alive.

Ok, now it's time to see what is working or not, so no Main A and B, no AC 1 and 2, let's have a look to the Environmental and Thermal Panel on L2 side.

So we lost for sure some systems, but let's try to save what we can.
IMU Fan is switched on C ( AC 3), Avionics Fan from bay 2 and 3 are switched to AC 3, Avionics Bay Fan 1 is lost, temperature is rising a lot

Let's continue our Diagnostic, One Water Loop is lost, hopefully Loop 2 is switched on AC 3 and Freon Interchanger will work
We lost also one Freon Loop, the other is working well.( on the picture above, Freon Flow from loop 2 sensor is alive, good )
On the next one, we see no flow on loop 1

Primary A FES is powered by Mn C, so it works. For later in the entry, Ammonia Boiler will be available on Primary B controller, good.
Air System 2 is also activated in case system 1 fails .

So, let's sum up.
We still have 2 engines and 2 APU, no lock up.
Thermal systems works, one H2O loop, one Freon loop and at least one FES and Ammonia boiler work.
IMU Bay air circulation is ok.
Air system and pressurisation ok.

So vital systems are working so far.

It's gonna be a normal RTLS, with some limited access to CRT and MDU, that's gonna be the complicated part, switching between SM and OPS 6/Spec 50/Spec51

We are heading back to KSC, MCC is on fire:

It's becoming very dark inside, Guidance convergence is optimal and PPD approaches

Alpha recovery phase

It's time for the Glide Return To Launch Site, tremendous view

Time for the probes to be out, we can see on Spec 51 what the probes are measuring under ADTA ( Altitude, angle of attack and Mach) and compared it to what IMU is displaying on ADI, then we can intregate via Spec 50 the ADTA value to the guidance loop and Altitude coming from ADTA to navigation filter to affinate the State vector.

You can notice some difference in Alpha angle and Altitude, Probes gonna affinate our Guidance value

I tried a Nav Delta update on Spec 50 ( Right Under NAV DELTA, we can enter an offset to the current state vector on X, Y ,Z axis and on speed, then load it with item 16)
Those offset will be given by MCC

We are approaching from the ground, looking for the runway

Monitoring is not easy task with just 2 MDU and on CRT :)

I was short for Runway 15, I changed to 33 with Straight in and Minimal Entry Point to Shorten a maximum, and when turning on final runway axis, following perfectly the guidance, I had the good surprise to be way closer to the Runway than expected
I forgot Kalmann Filters ( so much things to do), and State Vector was very degraded ( He thought runway was 3 km further on X axis ahah)

I managed an acrobatic non conventionnal landing, not very proud of it, but it worked out.

I was very impressed by the fidelity included into Electrical Systems. Very nice to do some scenarios like that and to have some very realistic effects on systems, especially Engines and APU's.

I hope you enjoyed my sum up, it was a lot of fun to prepare this unfortunate scenario :)

Offline Stardust9906

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Re: Flight Gear Space Shuttle Simulator
« Reply #6 on: 09/26/2017 12:30 pm »
Looks interesting thanks for the heads up.

Offline Gingin

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Re: Flight Gear Space Shuttle Simulator
« Reply #7 on: 10/03/2017 12:01 pm »
Good Morning,

I was tested lately different intact aborts, and I wanted to highlight a bit more the Return To Launch Site to KSC.
It is one of the most impressive  I find.
To fly outbound leg at Mach 7 then invert the speed to come back at Mach 7 towards Florida. It gives vertigo considering how tight  the margin is to meet all the guidance and navigation requirements to end up gliding back towards KSC.

One very important reading is the RTLS part in the Intact Ascent Aborts Workbook:
Everything happens fast in a RTLS, so it's nice to have in the head all the sequence of what will happen. It helps to monitor the AP and take over manually in case of divergence from the nominal track.

Moreover, the work on the RTLS guidance OPS6 , closed loop AP (constantly re evaluating how well it is doing and makes corrections to account for any errors), is astonishing, and very precise if the abort is not declared after the Negative Return Border ( 4 mn into the flight/ Vi around 8 kft/s) in the sim.

Here a sum up of differents boundaries, which are almost the same for every missions, plus or minus a delta Vi depending of the Orbit Inclination Targeted.

One thing with abort is that no abort will be declared until 2:30 mn in the mission.
So even if an engine fails during First Stage Ascent ( before SRB Sep), and RTLS is selected, it will not begin the guidance before 2:30mn.
That was to let the time to the Orbiter to stabilize after SRB Sep, and to damp any transient states left from SRB guidance.

Latest time to declare a RTLS is at 4:00mn, after the downrange and speed are too high, and TAL would be selected.
Usually, for a failure other than an engine, decision to take RTLS or TAL abort was delayed until 3:40 mn to let the time to MCC to evaluate the gravity of the failure, and choose the best abort to deal with it.

I) From Lift-Off to PPA

Starting on the pad, early morning

Checklists done, Final Countdown and Main Engine Ignition
The Shuttle wakes up all Florida

Tower cleared, farewell Atlantis, and safe journey

Failure on the center engine implemented after 2:30 mn

Abort initiated by the Commander,

Many things will happen, Real Checklists in game are available ( Cue Cards), with actions for both Commander and Pilot. Sometimes, a pause in the game might help when it is becoming to dynamic.

First, let's select Max throttle to allow the engines to have access to more power if required
Spec 51 PRO and Item 4 EXE

Let's talk about guidance convergence. It will indicate how well is performing the AP, and should decrease close to zero to show that the guidance is nominal and thrustworthy.
Just check the tendency first, if it's decreasing, it's good sign, if not, take manual control

Below unconverged guidance table, you will find some hints on pitch to take during outbound and inbound legs, as well as the % of propellant when to do the turn around towards KSC
It's usefull for Manual RTLS, but also to monitor what the AP is doing.
Here, failure at 2:30mn, so outbound pitch around 42 and PitchAround when Porpellant ramining is around 50 %

Next step, propellant dump in OMS tanks.
Aim here is to advance Center Of gravity to avoid Loss Of Control(LOC) during entry.
Have a look to the crossfeed valves of both RCS and OMS systems, closed prior to the dump

Automatic reconfiguration will happen during time critical phases, like abort.
OMS tanks will feed RCS thrusters and those will simuteanously fire to dump propellant.

SPEC51 PRO to call the Override Page
Item 6 EXE  Item 7 EXE to iniate the dump.
Time to Go of 132 seconds until depletion of OMS Tanks

Have a look again to RCS and OMS panel
CrossFeed Valves are now open, and RCS Isolation Tank Valves are closed.  RCS are fed by OMS tanks only to avoid back pressure into RCS tanks,  brillant piece of mechanics.

Around 7kft/s of inertial speed, we are approaching 50 pourcent of propellant ramaining.
It's time for the PPA, Powered Pitch Around, where the Shuttle Pitches Around towards KSC


Time for PPA, Guidance has fully converged, and remaining propellant around 50 % like planified, perfect.

Back to the Cap

Dump finished, red alert announcing OMS tank pressure Low
We can check deeper on the Sys 2 page, Low pressure in Helium OMS tanks and Low quantites( below 5 %)

A very impressive situation now.
We are inverting our Velocity Vector, Speed relative to Earth is null.
If we loose other engines now, we fall back straight to the sea. One of the most tricky situations during a RTLS

Stationnary position for a brief moment :)

Next crucial step is the PPD, Pitch Powered Down.
Very important manoeuver preceding MECO
Thrust will be gradually decreased and Orbiter will pitch down to an angle of attack of -2 for ET separation. And all that without degrading guidance too much

Approaching the PPD

And PPD followed by MECO, note the angle of attack

Check that the ET is well separated, if not do it manually with Manual ET Sep switches

Then check that GPC transitionned to the next guidance Phase, OPS 602 Glide Return To Launch ( GRTLS)

And also, have a look to confirm that Pitch Roll/Yaw  Speedbrake and Body flap are in Auto mode


Another tricky phase.
MECO occured, we are falling back with a high Vertical Speed into atmosphere, which we gonna it hard.
Aim here is to not break the orbiter by over G's or EAS exceedance.   
Normal limits are G=2.5 G and EAS=330 kt, which can be extended to G=4.1 and EAS=470kt for Contigency aborts.  These last ones are hard boundaries which will probably break the Orbiter or lead to LOC.

Time critical situation before entry, so ET doors and propellant dump are initiated automatically to move forward Center of Gravity

Alpha recovery phase now.
Orbiter will hold a 50 angle of attack attitude until reaching 2 G

Nz hold phase. Depending of the Vertical Speed, Guidance calculates a number of G ( Nz) to maintain to avoid structural damages.
Here it's around 2.8.  So when reaching Nz=2.8 G , Alpha will be decreased by a pitch down manoeuver to maintain Nz constant.
Nz hold is a phase where boundary between G and EAS exceedance is very tight.
Manual way to calculate it:  When Nz=1G, note the VS ( it was 2000ft/sec)  Nz to hold = Vs at 1G/1000 + 0.65

So, Nz= 2000/1000 + 0.65= 2.65 G ( quite close to the computed one)

Some visuals, no plasma, a bit of glowing tiles

Then comes Alpha transition Phase
When Vertical Speed is above -300 ft/sec and increasing, Alpha will vary accordingly to the Mach
We can see on the picture some phugoid oscillations, positive vertical accel and speed, up and down :)
Also the EAS now decreasing, quite high. We could have take Pitch in CSS to allow a bit more G during Nz Phase ( less pitch down)  to avoid speed to increase to much. Very tight border here between pushing and pulling on the stick.
We didn't break any hard boundaries, so far, so good.

Gliding back towards KSC now, back on a nominal entry profile.

On Spec50 Horizontal Display, we incorporate TACAN into Kalmann Filters to affinate the State Vector (SV), Ratio is under one and Residual low, SV is looking good.

M=5, probes are deployed

Next Guidance transition, OPS 603 ( Vert Sit 1 and 2)
We check also on Spec 51 that the Probe Data ( ADTA) are correct, cross checked with PFD value coming for now from IMU
If good, Altitude coming from probes is incorporated in Nav Software by Item 25, and Mach,Altitude, Alpha willl feed the Guidance Software and show up on PFD by pressing item 28

We can ask to MMC how is our SV by a Delta State Update, quite Ok now, ( some small divergence on X,Y, Z axis with reality)

Approaching Mach2.7, HUD power On

Around 85000 feet, MLS ( Kind of ILS for precision Landing) channels are selected correctly, number 8 for runway 15 in KSC ( 3 redundant channels)

Approaching the HAC

And it is now time to take manual control by pressing CSS for Pitch and Roll/Yaw channels
After 20 mn of Hyper Sonic Flight, Atlantis is falling below Sound Barrier again

Overhead the Runway

Entering the HAC for a full 270 right

Last turn

On final, below 15000 feet, MLS is automatically activated ( yellow MLS) and TACAN data are not feeding anymore the navigation filter
MLS is way more precise than TACAN, updating the SV in a better way.
Impressive to see how close to reality those things have been implemented

Still a bit of error with SV,but quite ok.
We could have make a GPS Sv update to have a perfect SV, but it's precise enough for a safe landing...I hope :)

Then at 2000 feet RA, Pre flare and HUD Declutter to follow the guidance
300 feet RA Gear down and Final Flare

60 kts, Drag chute dropped and Wheels stop
Welcome back, Atlantis

Small Highlight on Freon Temperature reaching 70

NH3 boilers can be activated below 120000 feet when FES system is becoming useless to cool Freon Loop, no time for Freon Cold Soaked in Radiators during Abort :)

Hope yo enjoyed it.