News The Space Shuttle for Flightgear 3.6

Thorsten

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An early morning low-inclination launch, it's still dark on the ground, but the bright SRB flame lights up the clouds...

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Separation, and the Shuttle proceeds onward into the dawn light, everything nominal so far...

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... but we lose an engine. TAL abort is declared immediately, and the OMS propellant dump is started. The Shuttle starts to proceed towards Banjul, the standard TAL site for low inclination. Two engines are quite enough to keep us on the desired trajectory, so Africa, here we come!

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Leaving the US coast, there's already light on the clouds over the Atlantic ocean. If you look closely, you can distinguish the bright OMS and RCS flames of the propellant dump and the nearly invisible flame of the main engines.

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Darn - we've lost a second engine. Droop guidance engages automatically, pitching the Shuttle up steeply to avoid letting the trajectory fall below 275.000 ft (at this altitude, the ET might blow due to heating). To assist the maneuver, the last engine is throttled up to 109% performance. As the engine consumes propellant, the Shuttle gets lighter so eventually even a single engine can keep us from falling down. Likewise Single Engine Roll Control (SERC) has engaged - by gimbaling the last engine we can control pitch and yaw, but no longer roll, so the RCS jets now fire to do the job. The resulting roll is very very sluggish, so we do not roll to heads-up attitude with the ET attached.

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... and droop guidance has disengaged we're back on the trajectory. But the droop maneuver costs a lot of propellant, so we won't be able to make it even to Banjul. We're going to have an OPS 3 entry into the atmosphere, which is good, they're less wild than the OPS 6 version, but still - a bailout somewhere over open water is going to be a really rotten prospect, but there's Cape Verde a few hundred miles before Banjul - so we change the TAL site to there and keep our fingers crossed.

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MECO with little propellant to spare - the next minute is very hectic and shows why there's a commander and a pilot needed - the commander rolls the Shuttle to proper entry attitude, the pilot checks that the ET umbilical doors are properly closing, that the MPS propellant dump is initiated, and then the commander changes to OPS 3 before the atmosphere is felt too much.

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The heat shield is already glowing before we reach proper entry attitude.

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Turns out we're still a bit far off - the last resort is to activate low E flight rules. This means rough phugoids - the Shuttle bounces into the atmosphere, back out and falls back in - but this way we squeeze every mile we can possibly get out of the energy we have. The display flashes a high-g warning, entry is still on the rough side...

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ENTRY TRAJ display shows the rather strange signature of the phugoids...

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... but eventually we reach the nominal trajectory and can de-activate low E flight rules - back to a nominal entry then - we're going to make it to a solid runway after all, no bailout over open water.

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The Shuttle banks sharply using nominal entry guidance.

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Clouds over water seen from the Commander perspective... also note that on the SPI we can see trim is really off, we need lots of ailerons to keep in attitude. That's because we're flying an abort, there was no time to dump the FRCS propellant... About now is the time to activate the ammonia boilers to provide cooling of the systems at lower altitudes...

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TACAN of Cape Verde is acquired, air data probes are out, QNH at the landing site has been transmitted, a rather surprised controller at Amilcar Cabral International Airport has been told that he'll soon see a Shuttle coming in, all traffic around the airport has been diverted - and the Commander is seeing a nominal TAEM

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Turning into the HAC, morning light playing across the displays...

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It's a bit cloudy, broken cover, but we can't be picky now, can we?

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Descending into final approach...

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... and landing at Amilcar Cabral International Airport... Well, we were hoping to get into space today, but at least we didn't end up swimming in the Atlantic...

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A very short flight in the Shuttle with a wet end - 2EO BLUE contingency abort:


Two main engines fail during stage 1, that's in the BLUE contingency region. Guidance immediately lofts the trajectory while the SRBs are still on to get some extra time.

Directly after SRB separation, the Shuttle rolls using single-engine roll control (SERC) via the RCS. That is rather busy doing the OMS propellant dump at this point, because we need to get rid of the extra weight shifting the CoG in a hurry, so it works by extinguishing the jet opposite to the one you'd usually fire.

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The remaining engine is throttled to 109%, nevertheless the trajectory prediction looks bleak as we roll into entry attitude...

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All the remaining time with the good engine is used to blast towards the horizon and build up some speed to improve the entry phase:

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A quick ET separation, of course the propellant dump is not quite finished, so the separation looks a bit unusual...

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During Nz hold, we pull some 2.8 g, could be worse, initially elevons are fully deflected without reaching the desired AoA, but luckily that's still enough and as the atmosphere gets denser the control issues get better. Of course there's nowhere to go with the remaining energy, so after the Shuttle gets subsonic, bailout AP is activated to hold a constant descent, and after the call to coast guard, everyone abandons the Shuttle and jumps into the ocean.

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Gingin

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A quick overview of the last part of Entry preparations done before returning to Earth after our long polar trip.

MCC sent the Deorbit burn datas to the crew.

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Pre-Deorbit and Deorbit lines from the Deorbit Entry Landing Preliminary Advisory Datas (DELPAD) are filled.
APU start up sequence and decision altitudes in case of engine failure(s) or leakage are now known for a more efficient crew reaction in case of off-nominal Deorbit burn.


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Burn in progress

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Entry and TAEM/Landing data’s are summed up on another cue card.
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Entry interface with a steep Reentry Angle of 2 ° and nominal range to Edwards.

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Closed loop guidance flying through an Aurora.

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Alaska sightseeing Tour.

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4440 Nm later, while approaching Mach 2.5 , Software goes from Entry soft to TAEM guidance.

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And after 5 mn of iron gliding and a flown Heading Alignment Cone as forecasted by the cue card, wheels are stopped and post landing procedures can begin

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flight_manual_standard.png


The new version of the FG Space Shuttle Flight Manual corresponding to the milestone 13 is out - get your updated copy here!
 

Gingin

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Some news about some work being done on the dev branch, mainly about TAEM and Entry guidance algorithms.


TAEM and Autoland logic

TAEM and Autoland original logics are now well implemented based on NASA documentations.
More informations and full bibliography are available there: TAEM and Autoland original guidance

It is quite fun to test it with bad weather and low visibility operations.
State Vector needs to be well updated using all the available filters ( Tacan, MLS, GPS, air datas from Probes, …) in order to have a pinpoint landing.

Misty landing and X-wind Autolanding in KSC, wheel into the wind touching first
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Cavok and still air Autolanding
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Night Autolanding and sloped runway qualification in Easter Island
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Back to Edwards concrete runway
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Entry logic

Same work was made for Entry logic, based on algorithms used in NASA documentations.
It can handled a wide range of energy conditions, and several abort modes with some additional logic (Trans Atlantic Abort and Abort Once Around)
All the informations there :Entry original guidance

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Boundary between Entry and TAEM ( 80000 feet-ish / Mach 2.5 / 60 Nm-ish) is better handled Energy wise with those new logics.

Right picture: End of Entry guidance
Left picture: New batch of softwares / Start of TAEM guidance / Almost at the true velocity and on the path targeted 4000 Nm earlier.

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Fun challenges ( Short runway / High elevation airfields)

Paro (item 91) Bhoutan
Runway 33 only due to terrain.
It requires some headwind and some short speedbrakes logic.
Manual flare to force a high angle of attack for a low ground speed at touchdown.
Challenging !


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Gingin

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Spring News on the dev branch: https://sourceforge.net/p/fgspaceshuttledev/code/ci/development/tree/

mluTgA.jpg



1)A new Orbital Insertion AP based on the real one used, a deeper version of the Powered Explicit Guidance scheme: https://www.orbiterwiki.org/wiki/Powered_Explicit_Guidanc
A verstatile and powerful tool for nominal operations (Orbital insertion) and intact aborts(TAL and ATO for now).

Complete sum up of the FG Unified Powered Explicit Guidance there: https://forum.flightgear.org/viewtopic.php?f=87&t=40190


2)RMS cam view:

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Latest screenshots

Nightshift
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Morning Launch
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Orbital insertion
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Test phase
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TAL to ZAZ to test Ascent, Entry and TAEM algorithms resilience.
A true simulator script, with electrical failures and kind of ECAM actions while performing the intact abort.
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Roll to heads up
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Entry
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80000 pieds et Mach 2.5, TAEM
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Final
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20° path, quite impressive view from the Mission Specialist seat
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Flare
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