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Old 05-15-2017, 09:04 PM   #1
Gingin
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Default Let's try a Return To Launch Site

Hello Guys,

I finally found a way to handle this complicated intact abort (especially in manual). Thank you for all your advice, it helped a lot.

As you said Thorsten, it's really a dynamic situation, where it's hard to follow a specific chart.


This one gives a general overview of the procedure (very useful), but the distance in abcissa is a bit high, I had to reduce by at least 70Nm for the PPA, and PPD/MECO.
Altitude also is a bit over estimated, I didn't climb higher than 360kfeet and Zero Relative Velocity point was reached around 250 kfeet.

The Intact Abort Ascent Workbook was also very useful.

I used STS 3 mission, I just modified the max thrust to 104% in Mission config to have the opportunity to put more thrust when one engine fail.


Let's go.
10 sec after take off, I took manual control of thrust to come to 100% and reduced manually the thrust when Mach 1 was approching.


I simulated an engine failure by pressing the manual shutdown switch on pedestal (center, easier ) I did it at 2mn30sec. As soon as it happens, put back 104% of power, and press CSS for manual control.


The unconverged guidance table is very useful, and really accurate also.


I took for outbound theta 42 and decided to do the PPA a bit later, at around 47% of propellant remaining.


Mach 7,7 ( a bit higher than expected, but I will keep 104%Pc for the return leg), 350 kft and propellant at 48%. Let's Pitch Around


For the Outbound legs, I took initially like in the chart theta=52



We are approaching Meco time(propellant at 2%), parameters look good, Mach is reaching something around 5 and 6, we are around 230 kft ( safe altitude for ET jettison), vertical speed increasing in order to perform a PPD with an alpha of -2 and vertical speed around 800 f/s.


Let's go for the Powered Pitch Down, alpha -2, nice vertical speed, waiting for MECO ( it's hard to do many things with one pilot :d )



MECO Time !A bit high on altitude and speed, but in the margin.
In 30 sec before MECO, took more than 1 mach and 10kfeet. It's really a crucial part of the RTLS, I should have cut off engine 15 sec earlier to be on speed and lets say 10 to 15 kft lower.




And this one picture helped me a lot for distance at MECO, speed , vertical speed.Found it in Abort workbook


Umbilical Doors closed, LO2/LH2 purge in progress, Ammonia Boilers started.
We might have a chance

Next, Alpha recovery. As we can see on OPS 304, we are a bit high on the profil. We are going to catch that by maintening 50 angle of attack.


Then Nz constant phase.When G numbers approach 2, we have to push on the stick to reduce angle of attack in maintening constant G number around 2, and that until a vetical speed of around -250 f/sec ( where we should be back on path)


End of Nz constant phase, we are almost on path,max KEAS was 450 kts ( aim is to be below 470,which was acceptable for these kind of abort) and G's under 3,5 so inside margin.



Mach 5, Probe heat out, Radar altimeters on,HUD on.
Time for some S turn to loose altitude.




Final turn



Final ( high, I made S turn on final again, and my joystick was a bit slow/ stuck on roll )


I managed to land safely, around 22 mn after Lift Off

It took me time, but it's coming. It's really a practice thing indeed.
I was quite happy with this last one, didn't exceed max limit (4G/470kt KEAS as written in docs). So theoritically, it should have been survivable.

Both Orbiter and SSU are really amazing on performance point of view. We can go really close to the official values. Unconverged guidance table is also very accurate.
Anyway, I hope TAL gonna be easier

Last edited by Gingin; 05-15-2017 at 09:09 PM.
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Old 05-15-2017, 09:38 PM   #2
GLS
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The post ET sep image is very nice!
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Old 05-15-2017, 10:02 PM   #3
Urwumpe
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Nice to see manual RTLS still works. Was some versions ago I tested this myself.
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Old 05-15-2017, 10:08 PM   #4
Gingin
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Like you told me GLS, I dump everything early :D

Yep Urwumpe, great coding job, she is flying well

Just a sum up of max limitations of the shuttle for abort and contigency one.

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