why coundown is needed for rocket launching..?? In addition to the answers that have been given, it should be noted that there is a window of opportunity for a launch to occur, known as a launch window. This certainly occurs when trying to get somewhere such as the International Space Station, but even earth orbiting satellites have a window of time where the rocket can meet its performance. Bottom line is, the exact time of launch is very important, and a complex sequence of events have to happen in just the right order to make it happen. Space Flight Now provided a generic countdown clock for the Falcon 9, Ill re-post a few of the highlights. Some of these things are done to keep the batteries topped off till the lat minute. You dont want to put the fuel in until the last minute, to save it (Most rocket fuel is cryogenic). When the rocket has its fuel loaded, you want to keep non-essential personnel away from it, making it so any tasks they need to do is put off until the end. You dont want to arm the system to launch until you are completely ready, thus, it only happens right before. There are many more such examples of why things are done in a particular order, but hopefully this will give you a sense. L-13:30:00 Dragon Power Up L-7:30:00 Launch Vehicle Power Up L-3:50:00 Liquid Oxygen Loading L-3:40:00 Rocket Propellant 1 Loading L-1:00:00 Weather Briefing T-0:09:40 Verify that Terminal Countdown has started T-0:09:30 Merlin 1C: Lox Bleeder Valves Open T-0:07:00 Dragon to Internal Power T-0:04:46 Stage 1 & Stage 2 Auto Sequence starts T-0:04:30 Transfer to Internal Power T-0:04:10 Vehicle Release Auto Sequence T-0:03:40 TEA-TEB Ignition System Activation T-0:03:25 Flight Termination System to Internal Power T-0:03:11 Flight Termination System Armed T-0:03:02 LOX Topping Termination T-0:03:00 Second Stage Thrust Vector Actuator Test T-0:02:00 Range Verification T-0:01:30 Final Engine Chilldown, Pre-Valves/Bleeders Open T-0:01:00 Flight Computer to start-up T-0:00:50 First Stage Thrust Vector Actuator Test T-0:00:40 Propellant Tank Pressurization T-0:00:20 All Tanks at Flight Pressure T-0:00:15 Arm Pyrotechnics T-0:00:03 Merlin Engine Ignition T-0:00:00 LIFTOFF
Posted on: Sat, 28 Jun 2014 05:22:49 +0000
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