lehpron
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### ?'s Re: Space Shuttle Initial Lanuch Sequence

Please focus your attention mainly on the orbiter in this nice picture
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• Where is the center of gravity when the full tank is attached without the SRB's generally (I know it's loosing fuel mass)?

• What was the reasoning behind the orbiter's angle of engine thrust?

• Does SS's wing balance the moment from the engines?

• In footage I've seen of launch, the SS appears to roll and then pull up over the ocean such that it goes up while inverted. How much, if any, trim is maintained to keep the space shuttle from keeling over as it goes through the ionosphere and beyond?
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okelleynyc
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### RE:?'s Re: Space Shuttle Initial Lanuch Sequence

Good questions,

My guess would be that the CG is "generally" somewhere below the orbiter when mated to the external tank. But someone else will have to confirm this.

 Quoting Lehpron (Thread starter):What was the reasoning behind the orbiter's angle of engine thrust?

So that the thrust is pushing through the CG?

 Quoting Lehpron (Thread starter):Does SS's wing balance the moment from the engines?

I don't believe the wings provide any part in the stack's ascent. The SRBs provide 70% of the thrust at liftoff and have gimbal motors capable of 8 degrees of movement. And don't forget, the orbiter's engines also gimbal. These are the principal systems used in rolling the stack and keeping it on it's flight track.

 Quoting Lehpron (Thread starter):n footage I've seen of launch, the SS appears to roll and then pull up over the ocean such that it goes up while inverted. How much, if any, trim is maintained to keep the space shuttle from keeling over as it goes through the ionosphere and beyond?

I don't know the specifics here, but do know that the stack does roll inorder for the telemetry/communication antennae to point to the ground.....
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Thorny
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Joined: Thu Jul 07, 2005 8:44 am

### RE:?'s Re: Space Shuttle Initial Lanuch Sequence

 Quoting Lehpron (Thread starter):# Where is the center of gravity when the full tank is attached without the SRB's generally (I know it's loosing fuel mass)?

Around the middle of the External Tank. The External Tank is composed of two propellant tanks, a Liquid Oxygen tank that's the pointy top end, and a Liquid Hydrogen tank that is the lower two-thirds of the structure. Connecting the two is an Intertank structure. The Shuttle Orbiter's nose attaches there. So do the two Solid Rocket Boosters (mount points are just below the SRB nose cones) which are connected by a very strong beam that passes straight through the Intertank, between the LOX and LH2 tanks.

 Quoting Lehpron (Thread starter):What was the reasoning behind the orbiter's angle of engine thrust?

To deliver their thrust through the vehicle's center of mass, thereby making maximum use of available thrust.

 Quoting Lehpron (Thread starter): # Does SS's wing balance the moment from the engines?

No, the wings are very fragile and the flight profile is carefully tailored to protect the wings.

 Quoting Lehpron (Thread starter):In footage I've seen of launch, the SS appears to roll and then pull up over the ocean such that it goes up while inverted.

The "Roll Program" is initiated immediately after the Shuttle climbs past the gantry. It is actually a maneuver in the pitch, yaw, and roll axes and has many purposes...

- Turns the vehicle into the direction needed for the orbit of that particular mission
- Give the astronauts a clear view of the horizon in the event of an emergency
- Keeps the wings perpendicular to the desired direction of travel
- Give better "look angles" for various communications antenna around the Cape
- Simplify the Return To Launch Site abort, if one is needed.

By the way, the Roll is not new to Space Shuttle. Every launch vehicle does it, Shuttle is just the most obvious doing it. I was surprised to hear a Gemini astronaut call out "Roll Program" after launch while watching one of the NASA History Videos.

 Quoting Lehpron (Thread starter):How much, if any, trim is maintained to keep the space shuttle from keeling over as it goes through the ionosphere and beyond?

The three Main Engines can change the angle at which their pointing (called 'gimbaling') in order to keep thrust directed through the center of mass even as that position changes while propellant is expended.

DfwRevolution
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### RE:?'s Re: Space Shuttle Initial Lanuch Sequence

That's an interesting exposure... I watched the live broadcast of the STS-114 launch and the day was much brighter albiet a little hazy.
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eksath
Crew
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Joined: Tue Aug 03, 2004 6:19 am

### RE:?'s Re: Space Shuttle Initial Lanuch Sequence

 Quoting DfwRevolution (Reply 3):That's an interesting exposure... I watched the live broadcast of the STS-114 launch and the day was much brighter albiet a little hazy.

yes,it was. See this shot taken seconds before:

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the exposure is because the center averaged sensor has locked on to the extremely bright flame and captured it well at the expense of the rest of the picture. The film speed is fixed at about 1/2000sec for the shot and the aperture varies according to the sensor.
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