Roll program
The examples and perspective in this deal primarily with the United States and do not represent a worldwide view of the subject. (August 2020) |
A roll program or tilt maneuver is an
A roll program is completed shortly after the vehicle clears the
Saturn V
The Saturn V's roll program was initiated shortly after launch and was handled by the first stage. It was open-loop: the commands were pre-programmed to occur at a specific time after lift-off, and no
Roll on the Saturn V was initiated by tilting the engines simultaneously using the roll and pitch
Space Shuttle
During the launch of a Space Shuttle, the roll program was simultaneously accompanied by a pitch maneuver and yaw maneuver.[4]
The roll program occurred during a Shuttle launch for the following reasons:
- To place the shuttle in a heads down position
- Increasing the mass that can be carried into orbit (this was actually the initial reason - a 20% payload increase due to more efficient aerodynamics and moment balancing between the boosters and main engines)[5]
- Increasing the orbital altitude
- Simplifying the trajectory of a possible Return to Launch site abort maneuver
- Improving radio line-of-sight propagation
- Orienting the shuttle more parallel toward the ground with the nose to the east
The RAGMOP computer program (Northrop) in 1971–72 discovered a ~20% payload increase by rolling upside down. It went from ~40,000 lb to ~48,000 lb to a 150 NM equatorial orbit without violating any constraints (max Q, 3 G limit, etc.). So the incentive to roll was initially for the payload increase by minimizing drag losses and moment balancing losses by keeping the main engine thrust vectors more parallel to the SRBs.[5]
References
- ^ NASA - STS-117 Lift Off! ATLANTIS: "Houston, Atlantis. Roll program." Voice 1: "Roger roll, Atlantis".
- ^ Gunderson, Robert; Hardy, Gordon (1966). Piloted Guidance and Control of the Saturn V Launch Vehicle. Peaceful Uses of Automation in Outer Space. Springer. pp. 33–50.
- ^ Haeurssurmann, Walter (1970). Description and Performance of the Saturn Launch Vehicle's Navigation, Guidance, and Control System. 3rd International IFAC Conference on Automatic Control in Space, Toulouse. Toulouse: Elsevier. pp. 275–312.
- ^ Jenks, Ken. "Why does the shuttle roll just after liftoff?".
- ^ a b NASA-CR-129000, TR-243-1078 (1972)