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From KSC to White Sands: Abort Once Around with the Shuttle

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From KSC to White Sands: Abort Once Around with the Shuttle

Postby GinGin » Thu May 31, 2018 7:08 pm

I was testing Abort Into Orbit and Abort Once Around ( ATO/AOA) with Shuttle and wanted to show a bit some of the possibilities offered by the FG Shuttle concerning those Intact Aborts.
We will see both of them for a 1h30 flight that will bring us to White Sands, New Mexico in one Orbit from KSC.


To have some accurate data for that kind of flight ( ISS launch) concerning Boundaries and procedures, you can have a look to the FDF of STS 135 ( page 95 and section 6 for AOA procedures)
https://www.nasa.gov/centers/johnson/pdf/567068main_ASC_135_F_1.pdf



Start of our journey in my headquarter, KSC, for a flight to ISS with a North East Launch Azimuth to reach an inclination of 51 °.

Morning Launch with a partially broken Sky

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Shuttle breaking the wall of sound through terrific Cumulus

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Maximum Dynamic Pressure, nice effect of condensation

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Until then, we still got Three engines, almost a miracle for me :)

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I can't get fed up with those lighting effects

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Time to play, ready for a failure.
First, let's recap our boundaries for a 50 ° inclination launch
ATO opened around 5 mn and Vi= 10800 f/s

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Let's break an engine, Vi=10800 perfect.
ATO declared and guidance changed

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I commanded on Spec 51 a dump of 40 % of OMS propellant to have extra velocity added ( around 400 ft/s)
I want to keep the rest in case of Abort later or to deorbit.

Roll to heads up

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MECO time, we are on Orbit, 94 Nm by 41 Nm.
Not nominal, but ATO worked

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Now what do we need ? OMS 1 to raise the perigee or can we skip it to go to OMS 2 directly ?
Table below is going to help us
We have to add perigee and apogee 94+41=135 Nm
We are on the right portion, right of the 115 Nm abcissa, no need for an OMS 1

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Bye Bye ET

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We could then stay into orbit, raise the perigee and continue with the mission.
But I choose to simulate a failure that would force us to come back as soon as possible on the ground




That is the second part, the abort once around
At that inclination, we have two choices, KSC or NOR. NOR is Northrup, aka White Sands Shuttle Harbor in New Mexico.


First, let's put hydraulic pumps on Low to not waste APU fuel and reconfigure the orbiter

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I chosed NOR, to see that famous Salt Lake desert.
To help us with deorbit burn, we can take some data in the FDF that will give us some hints about PEG 4 guidance and Time Of ignition

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Starting from the top, we have MECO ( where we are)
We could go to the second line for an OMS 2 burn that will secure our orbit or go to the last part if an Abort Once Around is needed ( our case)



We will use then AOA/K value ( last one is shallow AOA for the case where we don't have a lot of propellant remaining)


So, we are well between a sum of 145 and 115 Nm ( 135 Nm for us)
Data say Time of Ignition at 34 mn into the mission
PEG 4 parameters C1= 15385 C2=-0.6172 Ht=65.8Nm ( height of entry, 400000 feet) and Theta angle of 172 degrees ( angle between the burn and the 400 kfeet altitude)
Then we should use around 500 ft/s of velocity during the burn for a re entry range of 4300 Nm



Those parameters are mostly in case of loss of comm with MCC, to have some numbers to work with and try to find a deorbit solution

For that, let's use the new Thorsten Tool where we can enter those parameters ( and our state vector parameters) to see if we have a solution

More explanations here ( Deorbit tutorial at the end also) http://www.science-and-fiction.org/science/leo_targeting.html






I played with theta angle to have a converging solution ( 162 instead of 172), and also with the time of ignition ( 42 mn instead of 34 mn)
I wanted to have a Rentry interface around 3000 Nm instead of 4000 Nm ( Flight Gear works better with that kind of range for entry), and it is better to be a bit high on energy than the opposite.
Don't want to finish in the Ocean.


What came out is Velocity on - X and Z LVLH axis ( retrograde speed to lower perigee and outward radial speed to move forward the perigee above white sands)
The tool works really well, hard to find those kind of values, especially for radial velocities like that.

So, -18 ft/s on X axis and 570 ft/s of outward velocity, for a total of 580 ft/s, close to the data we saw before for a REI of 3039 Nm and perigee at -5 Nm, quite steep approach, but it should work.

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And here the result after the 5 mn burn, low on propellant, but it worked as expected
Alea jacta est

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We have now some times before the entry
Time for contemplation :)

Saudi Arabia and Quatar

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Bye Bye Sun

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Borealis Aurora

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Time for the entry, don't forget to put back on Normal the Hydraulic Pumps, or you will crash like I did :oops:

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A bit low on energy, low Angle of Attack ( 37 °) and no bank to recover that

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Burning hot

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West coast in sight, and Sunrise again

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Everything worked well for entry
Some glitch with TAEM guidance, no guidance at all, we will have to land the Shuttle by our own judgement, full VFR pattern now



At least, I can't miss the landing spot
Beautiful Salt Lake

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We can see an airforce base next to the lake ( Hollowman base )

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Final, 12000 feet , and 6 Nm to go.
Time to judge well the flare without guidance

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Final Flare view from the AFB ( a bit high)

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But it went well, nothing broken


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Demanding scenario, but how interesting !!

LEO tools for OMS and deorbit targeting is a real plus, and it's quite amazing that it works so well with real data even though all parameters of payload and exact State vector are not met
Well done !
GinGin
 
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Re: From KSC to White Sands: Abort Once Around with the Shut

Postby legoboyvdlp » Thu May 31, 2018 10:43 pm

Nice clouds and screenshots :D
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Re: From KSC to White Sands: Abort Once Around with the Shut

Postby GinGin » Mon Oct 15, 2018 4:49 pm

I tried another one with the fix to White sands, it works very well :)
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