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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 14:12, 14 May 2016
, 14 May 2016→Abort once Around
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To initiate TAL abort in FG, the entry guidance computer needs to be set to the TAL landing site and as abort mode 'TAL abort' needs to be selected. In response to this, the HUD symbology changes to show key information needed to pilot the abort. Alternatively, the TAL may be selected on the SPEC 51 (OVERRIDE) display by first selecting TAL mode (item 1), followed by selecting ABORT (item 3). The groundtrack map is most useful in aiming the trajectory and establishing a reasonable entry interface. | To initiate TAL abort in FG, the entry guidance computer needs to be set to the TAL landing site and as abort mode 'TAL abort' needs to be selected. In response to this, the HUD symbology changes to show key information needed to pilot the abort. Alternatively, the TAL may be selected on the SPEC 51 (OVERRIDE) display by first selecting TAL mode (item 1), followed by selecting ABORT (item 3). The groundtrack map is most useful in aiming the trajectory and establishing a reasonable entry interface. | ||
== Abort to Orbit == | |||
Usually the next option if more energy is available for a TAL would be an Abort to Orbit (ATO). Here, the Shuttle aims to reach a lower than nominal but still safe orbit (typically around 105 miles altitude). From there, mission control can decide how to proceed, whether to land the Shuttle or try to continue with the original mission. | |||
An ATO follows a relatively late loss of an engine during ascent. Dependent on payload and target inclination, a <i>partial</i> OMS fuel dump is initiated early on to reduce the weight that is accelerated and thus gain extra velocity.At MECO, the Shuttle is typically delivered into an unstable orbit with the periapsis inside the atmosphere, thus an immediate OMS-1 burn is executed to push the Shuttle onto a rising orbit with a 105 mile periapsis, followed by a circularization OMS-2 burn at the periapsis. | |||
== Abort once Around == | == Abort once Around == | ||
Requiring more energy than a TAL but slightly less than is needed to reach a safe orbit, the Abort once Around (AoA) would typically be used if there is a systems problem during ascent that requires to get the Shuttle down in a relatively short time or if there is a problem with the OMS engines in addition to an underspeed due to engine loss prior to MECO that means maneuvering is severely limited. | |||
During the AoA, the Shuttle flies a depressed ballistic trajectory around the whole Earth, including a normal de-orbit burn and entry to land at the launch site. The decision to abort to ground rather than to orbit does not have to be made until the OMS-1 burn. | |||
== We're going to Africa! - a TAL tutorial == | == We're going to Africa! - a TAL tutorial == | ||