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Flying the Shuttle - Abort Procedures Overview: Difference between revisions
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Flying the Shuttle - Abort Procedures Overview (view source)
Revision as of 09:55, 26 April 2016
, 26 April 2016→We're going to Africa! - a TAL tutorial
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Once that's verified, bring back OVERRIDE. | Once that's verified, bring back OVERRIDE. | ||
The problem we need to deal with now is that right now, there's a full load of OMS propellant stored in the rear pods which was intended for the mission we abort. Upon entry, it needs to be gone otherwise the CoG trim will be off so far the airfoils can't hold the Shuttle in the correct attitude. | |||
Well, since we're not going to need this propellant on the way to Banjul, there's also no point to lug it all the way into near-orbit - we can just dump it now. | |||
Do <b>ITEM 6 EXEC</b> to arm the dump, verify that item 9 shows 100% to be dumped, then do <b>ITEM 7 EXEC</b> to start the dump. The software will ignite both OMS engines and (unless that's inhibited by item 5) automatically open the OMS to RCS crossfeed interconnect valves and use the rear RCS thrusters to burn the propellant faster. This takes a few seconds, after which you can switch to outside view and enjoy the fireworks: | |||
[[File:TAL-tutorial04.jpg|600px|TAL tutorial 4]] | |||
OMS DUMP TTG has a counter that will show you about how long the dump is going to take - expect about two minutes. Once all the fuel is gone, make sure (by opening the valve schematics from the menu) that the software really has closed the interconnect valves and the aft RCS thrusters are now fed from their tanks. We're goint to need the RCS at arctop and during entry, and we really don't want to discover that we don't have control because we're trying to feed them from the depleted OMS tanks! | |||
CWS will throw a warning message about OMS tank pressure alerting you to the fact that the tanks are rapidly depleting - since that's the whole point of the fuel dump, simply acknowledge it. | |||
If you're flying manually, note that there's a rather useful function on SPEC 51 in addition - by selecting item 50, you can throttle the engines up to 109% of rated power which gives you some compensation for a lost engine. Don't select this option if you're under auto guidance, it'll just confuse the computer. | |||
* Monitor progress on the ASCENT TRAJ 2 display - TAL guidance should aim for a somewhat higher trajectory than nominal guidance, so don't be alarmed if you find yourself skirting the upper edge of the nominal trajectory - but remember as always, you need to take over manually once there are gross deviations from the trajectory! | |||
Also good to know - in case you lose a second engine late in the flight, roll control is lost (because roll control is done by vectoring the left engine up and the right engine down and vice versa - which you can't do with one engine). In this case, you need to do <b>ITEM 6 EXEC</b> on the OPS 103 screen to select single engine roll control (SERC). This will use the RCS thrusters for roll control, which is not as crisp as vectoring the main engines, but way better than nothing. For obvious reasons SERC doesn't work with a fuel dump via the RCS thrusters, so if you need SERC, you need to inhibit OMS - RCS interconnect during a fuel dump. | |||
== Further reading == | == Further reading == | ||
[http://spaceflight.nasa.gov/shuttle/reference/shutref/events/aborts/ NASA human spaceflight page on abort modes] | [http://spaceflight.nasa.gov/shuttle/reference/shutref/events/aborts/ NASA human spaceflight page on abort modes] | ||