Flight Question RTLS Flight profile

[Wrangler]

Hi Folks,

Another flight problem. I am also attempting to perform an RTLS. I tried using Wolf's RTLS Scenario and tutorial: [ame="http://www.orbithangar.com/searchid.php?ID=5575"]Space Shuttle RTLS[/ame]

I ran into an issue, so I tried creating my own scenario. Ran into the same issue. According to Wolf's tutorial, there is no action required until SRB Sep. The issue is that when you simulate an engine failure at ~MET 30 seconds, it appears that the launch autopilot cuts out. The launch stack starts to Pitch up (heads down position), until it back flips. This happens both in Wolf's scenario, as well as the one I tried to create. So is this something that Wolf missed in his Tutorial, and is actually how it should work? or is there something afoot here?

 

[Wolf]

Hi Wrangler,

to answer your question please note that the RTLS Doc states clearly to disconnect the autopilot immediately and continue the ascent manually. Here is what it says at page 11

"The scenario will see Discovery suffering a single SSME failure 30 seconds after liftoff.After cancelling the Engine failure aural warning (Esc) take manual control of theShuttle and continue first stage ascent following the nominal profile on GPC MFDOPS1."

The ShuttleFleet does not include autopilot capability in case of SSME failures therefore you'll have to practice your handling skills.

One thing you can do though (since we found AutoFCS works with Orbiter2010) is to engage it after ET tank separation for the GRTLS phase to KSC.
I have NOT tried this yet, so don't know if AutoFCS will work fine with the reentry profile.

Happy landings :thumbup:​

 

[Wrangler]

Hi Wrangler,

to answer your question please note that the RTLS Doc states clearly to disconnect the autopilot immediately and continue the ascent manually. Here is what it says at page 11

"The scenario will see Discovery suffering a single SSME failure 30 seconds after liftoff.After cancelling the Engine failure aural warning (Esc) take manual control of theShuttle and continue first stage ascent following the nominal profile on GPC MFDOPS1."

The ShuttleFleet does not include autopilot capability in case of SSME failures therefore you'll have to practice your handling skills.

One thing you can do though (since we found AutoFCS works with Orbiter2010) is to engage it after ET tank separation for the GRTLS phase to KSC.
I have NOT tried this yet, so don't know if AutoFCS will work fine with the reentry profile.

Happy landings :thumbup:​

I was practicing this last night while on a flight back from Bangkok. So I guess I made the same Mistake I always do, i.e. 'Skimmed' the tutorial. Ok...I will not read the whole documnt again before I do anything else. :facepalm:

Thank you Wolf. :embarrassed:

 

[Wolf]

I was practicing this last night while on a flight back from Bangkok. So I guess I made the same Mistake I always do, i.e. 'Skimmed' the tutorial. Ok...I will not read the whole documnt again before I do anything else. :facepalm:

Thank you Wolf. :embarrassed:

So you've probably done the other way around : next time

1) Keep your airplane autopilot ON so you can read the manual carefully

2) Turn the Shuttle autopilot OFF and fly a nice RTLS back to KSC :thumbup:

 

[Wrangler]

So you've probably done the other way around : next time

1) Keep your airplane autopilot ON so you can read the manual carefully

2) Turn the Shuttle autopilot OFF and fly a nice RTLS back to KSC :thumbup:

:lol:I was not flying the airplane. Not qualified to do that. And it is plainly obvious from my manual reading skills, why I will never qualify to fly the real thing. I was sitting in the back sipping a drink, while trying to figure out why I was having to maintain ascent profile, when the manual says "No action required till SRB Sep". I am now reading each and every page of your Manual, and Kudos for the work that you have put in.

 

[Wolf]

Thanks for pointing that out: I agree this information may be misleading. To clarify:
"no action required" has been reported below Fig.7 to explain the meaning of the MCC callout "Abort RTLS 2+30" (which means the engine failure has been confirmed by MCC, the RTLS has been invoked BUT no action will be done until 2 minutes and 30 seconds into the flight)
THIS WOLUD ONLY HAPPEN IN THE REAL CASE though!

Unfortunately with Orbiter you will not get any callout/support by MCC and no Shuttle guidance system will be available to fly the ascent automatically

The tutorial include some CHECKLISTS. If you look at the "1 ENGINE OUT RTLS CHECKLIST" in appendix 3 you'll see your first action after SSME failure will be
DISENGAGE DAP (Digital Auto Pilot)

Note that in the checklist there is also a Warning telling you to expect a high pitchdown momentum just before SRB separation (which means you will have to counteract that by pithching up).

I strongly reccomemnd the use of checklist whenever you practise RTLS

Please let me now if you find other discrepancies or misleading information, so that I can rectify those

Thanks

 

[Wrangler]

Thanks for pointing that out: I agree this information may be misleading. To clarify:
"no action required" has been reported below Fig.7 to explain the meaning of the MCC callout "Abort RTLS 2+30" (which means the engine failure has been confirmed by MCC, the RTLS has been invoked BUT no action will be done until 2 minutes and 30 seconds into the flight)
THIS WOLUD ONLY HAPPEN IN THE REAL CASE though!

Unfortunately with Orbiter you will not get any callout/support by MCC and no Shuttle guidance system will be available to fly the ascent automatically

The tutorial include some CHECKLISTS. If you look at the "1 ENGINE OUT RTLS CHECKLIST" in appendix 3 you'll see your first action after SSME failure will be
DISENGAGE DAP (Digital Auto Pilot)

Note that in the checklist there is also a Warning telling you to expect a high pitchdown momentum just before SRB separation (which means you will have to counteract that by pithching up).

I strongly reccomemnd the use of checklist whenever you practise RTLS

Please let me now if you find other discrepancies or misleading information, so that I can rectify those

Thanks

I definitely will. Right now, I am trying to arrange the cuecards, so that I may get the sequence of events right. Tough being the CDR and PLT at the same time. Also is RTLS only viable with single engine failures? what are the options for a 2 engines or a complete SSME failure within the first 60secs of launch? Can a single engine provide enough energy to perform RTLS?

 

[Wolf]

Theoretically an RTLS is available in case of 1,2 or even 3 SSME failures. A 3 engine out during first stage though will most likely lead to loss of vehicle due to overstress of the Shuttle stack and consequent structural failure either at the ET or SRB attach points (most of the first stage phase is condiered "black zone"). A 3 Engine Out, if survivable would eventually end up in a ditching/Bailout procedure since after SRB separation no thrust would be available to fly back towards KSC.

Have a look at this for full RTLS dscription (See page 13-14 for 3 engine out case)

http://www.nasa.gov/centers/johnson/pdf/383441main_contingency_aborts_21007_31007.pdf

this


http://www.nasa.gov/centers/johnson/pdf/383447main_intact_ascent_aborts_workbook_21002.pdf


and this


http://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Return_To_Launch_Site_.28RTLS.29