1,360
edits
Flying the Shuttle - Launch: Difference between revisions
Jump to navigation
Jump to search
→How it feels in FG
| Line 46: | Line 46: | ||
== How it feels in FG == | == How it feels in FG == | ||
The launch dynamics in FG is, if we neglect the noise and the shaking of the real thing (which is described as 'driving down a rough gravel road without any suspension, a shaking so hard the eyes cannot properly focus' as long as the SRBs are burning) probably fairly realistic. | The launch dynamics in FG is, if we neglect the noise and the shaking of the real thing (which is described as 'driving down a rough gravel road without any suspension, a shaking so hard the eyes cannot properly focus' as long as the SRBs are burning) probably fairly realistic. | ||
As part of the pre-launch preparations, the APU and hydraulics subsystems has to be started to enable thrust vector control of the main engines during ascent. If this is not done, the Shuttle will cease to be maneuverable after SRB separation. The procedure is outlined in a checklist: | |||
[[File:Shuttle checklists.jpg|600px|The pre-launch checklist of the Space Shuttle]] | |||
As soon as the throttle is moved to 65%, the main engines ignite. This is the starting signal for SRB ignition, the SRBs will follow three seconds later, and once they burn, there is no going back. The SRBs can not be throttled and will burn till exhausted, and they have enough thrust to lift the stack even if the main engine is switched off. | As soon as the throttle is moved to 65%, the main engines ignite. This is the starting signal for SRB ignition, the SRBs will follow three seconds later, and once they burn, there is no going back. The SRBs can not be throttled and will burn till exhausted, and they have enough thrust to lift the stack even if the main engine is switched off. | ||
| Line 55: | Line 59: | ||
At about 35 seconds into the flight, dynamical pressure (qbar) will rise rapidly as the stack goes supersonic. This is a dangerous phase of the flight. The stack is very top-heavy (as the heavy oxygen is stored in the tip of the ET and the light hydrogen in the bottom), so once it starts toppling, it won't come back. In addition, aerodynamical forces are very strong. In fact the very reason we do this phase in inverted flight is to reduce the wing loading. At the callout, reduce throttle of the main engines to 65% to minimize the pressure spike. | At about 35 seconds into the flight, dynamical pressure (qbar) will rise rapidly as the stack goes supersonic. This is a dangerous phase of the flight. The stack is very top-heavy (as the heavy oxygen is stored in the tip of the ET and the light hydrogen in the bottom), so once it starts toppling, it won't come back. In addition, aerodynamical forces are very strong. In fact the very reason we do this phase in inverted flight is to reduce the wing loading. At the callout, reduce throttle of the main engines to 65% to minimize the pressure spike. | ||
If you ascent is too flat in this phase, maximum qbar will be violated, or | If you ascent is too flat in this phase, maximum qbar will be violated, or you may lose control of the stack beyond the point the thrust vectoring can recover. If the orbiter is not in inverted flight at this point, the wing bending moment will grow too large, ripping the wings of the orbiter, resulting in a catastrophic loss of vehicle. <b>Do not attempt to cross max. qbar with positive AoA!</b> | ||
About 20 seconds later, max. qbar is over and the stack becomes much more controllable. Throttle up to full and reduce pitch to about 60 degrees (still inverted) and keep rising. | About 20 seconds later, max. qbar is over and the stack becomes much more controllable. Throttle up to full and gradually reduce pitch to about 60 degrees (still inverted) and keep rising. | ||
[[File:Shuttle launch01.jpg|600px|Launch track of the Space Shuttle]] | [[File:Shuttle launch01.jpg|600px|Launch track of the Space Shuttle]] | ||