Space shuttle is the most complex machine build by man but still we hear lots of problem related to it and it’s missions…as they say…more sophistication brings more problems……. Those who follow some bit of Shuttle missions have heard the word -"Mission Abort".What exactly is this??How and in what circumstances a mission is aborted?????So this week it’s all about Shuttle mission abort.
To reduce the complexity of the topic I am 1st writing about shuttle’s ascent abort mode.The ascent abort mode is during the ascent and docking to the space station.There are basically two types of ascent abort modes for the space shuttle-“Intact Aborts” and “Contingency Aborts”
Let’s talk abt Intact abort modes first----There are 4 subcategories for the Intact Abort.
1) Abort-To-Orbit(ATO)-:This Method is devised to Provide a temporary orbit fr the shuttle….this temporary orbit is lower than the nominal orbit. ATO requires less performance rate ,which in turn gives the opportunity to diagnose the problem and rectify it. Depending upon the success to solve the problem the shuttle can make early de-orbit maneuver or an orbital maneuvering thrust vectoring to raise the orbit and continue with the mission.This Technique is used when the crew or ground controllers can rectify the problem in flight.
2) Abort-Once-Around(AOA)-: In this Abort type, Primary Mission is suspended and the shuttle is brought back to earth.This requires a full revolution around earth and to perform 2 different orbital maneuver for lowering of orbit and re-entry of vehicle.The entry sequence will be similar to a normal entry sequence.
3) TransAtlantic Landing(TAL)-:The TAL is designed to land the shuttle on a transatlantic Landing Facility.In this Technoque the shuttle follow a ballistic trajectory .This process is employed when the thrust vectoring are not in synergy.This process doesn’t require Orbital maneuvering .
4) Return-To-Launch Site(RTLS)-: This mode involves flyin downrange to dissipate propellant and than turning arnd under power to return directly to the launch site or near the launch site.
We have Options but there’s a definite order of preference for different modes .The type of failure and the time of failure decides which mode should be selected. In cases where performance failures occur the preferred preferences are in the order of ATO,AOA,TAL AND RTLS. In case of some support system failure like cabin leaks or vehicle cooling problems, the preferred mode might be that which allows to quickly end the mission. In these cases TAL and RTLS are most probable than other 2 methods.A contingency abort is never considered if other option exists.
The mission-control-Houston is the prime caller for abort mode becoz it has the most precise information of shuttle ‘s current location and orbital position.In any case Houston knows more than any other observing station or even than the shuttle crew. Before main engine cutoff Houston periodically informs the shuttle crew which abort mode is available or not available.If gorund Communications are lost than the crew can select appropriate abort mode using onboard sensors and dedicated displays.
In very serious cases like in case of system failures the mission control opts for rapid re entry of the vehicle.TAL and RTLS are preferred in these cases.The shuttle will approximately take 35 minutes to perform these mode while the AOA mode will require 90 minutes. Which of these is elected depends upon the time and extent of failure of shuttle’s engines.
Contingency Abort-: This happens when the main engine of the shuttle fails and the boosters suffers frm low thrust problem.In this case Mission control Houston has to carry out a in flight escape for the crew.This method also involves ditching of space shuttle.The crew escape is carried out before ditching.
So here it is…..a brief info abt shuttles abort modes.I will write some more topics on shuttle and orbiter’s assembly.
To reduce the complexity of the topic I am 1st writing about shuttle’s ascent abort mode.The ascent abort mode is during the ascent and docking to the space station.There are basically two types of ascent abort modes for the space shuttle-“Intact Aborts” and “Contingency Aborts”
Let’s talk abt Intact abort modes first----There are 4 subcategories for the Intact Abort.
1) Abort-To-Orbit(ATO)-:This Method is devised to Provide a temporary orbit fr the shuttle….this temporary orbit is lower than the nominal orbit. ATO requires less performance rate ,which in turn gives the opportunity to diagnose the problem and rectify it. Depending upon the success to solve the problem the shuttle can make early de-orbit maneuver or an orbital maneuvering thrust vectoring to raise the orbit and continue with the mission.This Technique is used when the crew or ground controllers can rectify the problem in flight.
2) Abort-Once-Around(AOA)-: In this Abort type, Primary Mission is suspended and the shuttle is brought back to earth.This requires a full revolution around earth and to perform 2 different orbital maneuver for lowering of orbit and re-entry of vehicle.The entry sequence will be similar to a normal entry sequence.
3) TransAtlantic Landing(TAL)-:The TAL is designed to land the shuttle on a transatlantic Landing Facility.In this Technoque the shuttle follow a ballistic trajectory .This process is employed when the thrust vectoring are not in synergy.This process doesn’t require Orbital maneuvering .
4) Return-To-Launch Site(RTLS)-: This mode involves flyin downrange to dissipate propellant and than turning arnd under power to return directly to the launch site or near the launch site.
We have Options but there’s a definite order of preference for different modes .The type of failure and the time of failure decides which mode should be selected. In cases where performance failures occur the preferred preferences are in the order of ATO,AOA,TAL AND RTLS. In case of some support system failure like cabin leaks or vehicle cooling problems, the preferred mode might be that which allows to quickly end the mission. In these cases TAL and RTLS are most probable than other 2 methods.A contingency abort is never considered if other option exists.
The mission-control-Houston is the prime caller for abort mode becoz it has the most precise information of shuttle ‘s current location and orbital position.In any case Houston knows more than any other observing station or even than the shuttle crew. Before main engine cutoff Houston periodically informs the shuttle crew which abort mode is available or not available.If gorund Communications are lost than the crew can select appropriate abort mode using onboard sensors and dedicated displays.
In very serious cases like in case of system failures the mission control opts for rapid re entry of the vehicle.TAL and RTLS are preferred in these cases.The shuttle will approximately take 35 minutes to perform these mode while the AOA mode will require 90 minutes. Which of these is elected depends upon the time and extent of failure of shuttle’s engines.
Contingency Abort-: This happens when the main engine of the shuttle fails and the boosters suffers frm low thrust problem.In this case Mission control Houston has to carry out a in flight escape for the crew.This method also involves ditching of space shuttle.The crew escape is carried out before ditching.
So here it is…..a brief info abt shuttles abort modes.I will write some more topics on shuttle and orbiter’s assembly.
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1 comments:
Pretty cool and informative!
Are you basically talking only about NASA's shuttles? Does Houston keeps track of shuttles send by all countries?
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