Space Shuttle: Difference between revisions

|download      = http://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Aircraft/SpaceShuttle/

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[[File:Spacetripready.png]]

{{SpaceFlight}}

For precision control, the keyboard is a more suitable input device than a joystick or a mouse since exact nulling of rates is somewhat easier with keystrokes.  

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Once outside, the MMU can be used to float around the Shuttle, or to inspect co-orbiting objects. However, note that it is impossible to leave the EVA view unless the astronaut maneuvers back to the airlock. Currently it is not possible to see spacewalk from outside, nor can the view direction be adjusted - in a future implementation, spacewalk will be improved using the FG walker functionality.

== Aerodynamics of the Space Shuttle Orbiter ==

Somewhat simplified, one can divide the atmospheric entry in three phases - an initial near-ballistic entry phase in which airfoils are essentially useless, an aerodynamical entry phase in which the Shuttle is controlled by airfoils and aerodynamical forces are very noticeable on the trajectory, but in which the flight dynamics is completely different from that of an airplane and the final approach and landing phase during which the Shuttle is flown like an aircraft.

During these phases, control is passed from RCS jets to the airfoils - the inboard and outboard elevons at the trailing wing edges and the rudder/speedbrake at the tail stabilizer fin. The elevons can be deflected from -40 to 25 degrees, the rudder from -25 to +25 degrees. At a qbar of 10 lb/sqf roll control is taken over by the airfoils, at 40 lb/sqf pitch control is managed by airfoils and below Mach 3.5 finally yaw control is transferred, at which point the airplane-like phase of the entry starts. In addition to the primary airfoils, the Shuttle is equipped with a body flap which can be used to adjust trim.

During the first two phases, the Shuttle is flown with a high AoA (initially 40 degrees) to create a detatched bow shockwave which keeps the heat of atmospheric entry away from the fuselage. The characteristic hallmark of this attitude is that the stabilizer fin is shadowed by the wings - this renders the rudder ineffective above Mach 6 and makes the Shuttle yaw unstable against sideslip above Mach 2, i.e. any sideslip must be very accurately controlled by the FCS during entry or the Shuttle will tumble uncontrolled. This can not be done by the rudder, thus yaw jets remain crucial for controlling the Shuttle down to Mach 3.5.

=== Lift / Drag ===

Despite being designed for a gliding approach and landing, the Shuttle is not actually a very good glider - even close to approach, the glide ratio (i.e. L/D) reaches about 4.5, much less than most normal planes would have.

The maximum of L/D varies somewhat with Mach number, however for hypersonic flight thermal constraints force a high AoA and aerodynamical efficiency is a secondary concern.  Only in the supersonic to subsonic phase is the Shuttle flown close to its optimum glide ratio.

The pitching moment induced by the control surface varies dramatically as function of Mach number.

As seen from the figure, at high Mach numbers the response is fairly flat (i.e. large elevon deflections are needed to control the Shuttle) and also non-linear (upward deflections cause much less pitching moment than downward deflection). In contrast, at low Mach numbers small elevon deflections already cause large moments and the response is almost linear. In all regimes, the pitching moment is normal force (i.e. AoA) dependent.

| '''EVA'''  || Extravehicular Activity (spacewalk)

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| '''ISP'''  || Specific impulse