Why Asymmetrical Engine Startup on Delta 4 Heavy?

Celebrate786

The ULA Delta 4 Heavy uses an asymmetrical engine startup. Why is this? What are the benefits? Are there any drawbacks?The ULA Delta 4 Heavy uses an asymmetrical engine startup. This is because the Delta 4 Heavy has three boosters, and each booster has its own engine. The three boosters are not identical, and they are not symmetrically arranged. The asymmetrical engine startup allows the Delta 4 Heavy to achieve a more efficient burn, and it also allows the Delta 4 Heavy to have a more balanced thrust profile. The asymmetrical engine startup does have some drawbacks, however. One drawback is that it can create more vibration during the launch. Another drawback is that it can create more noise during the launch.

jorge_richardson

The United Launch Alliance (ULA) Delta 4 Heavy rocket uses an asymmetrical engine startup sequence because the three Common Booster Cores (CBCs) that power the rocket's first stage are not identical. Two of the CBCs are powered by Rocketdyne RS-68 engines, while the third CBC is powered by an Aerojet Rocketdyne AJ-10 engine. The RS-68 engines are more powerful than the AJ-10 engine, so starting them first creates an imbalance of thrust that could cause the rocket to tip over. To prevent this, the Delta 4 Heavy is equipped with a pintle thrust vector control (TVC) system that uses gimbaling engines to vector the thrust and keep the rocket stable during the engine startup sequence.

The RS-68 engines are started first, followed by the AJ-10 engine. Once all three engines are up and running, the TVC system is no longer needed and the gimbals are locked in place. This asymmetrical engine startup sequence is necessary to ensure a safe and successful launch of the Delta 4 Heavy rocket.

Vincent218

The United Launch Alliance Delta 4 Heavy launch vehicle uses an asymmetrical engine startup sequence because the three Common Booster Cores (CBCs) are not identical. Engine start is controlled by the Ground Control Station (GCS) and is initiated when the vehicle is at the proper angle and velocity for liftoff.

The engine start sequence for the Delta 4 Heavy is as follows:

The GCS sends a command to start the Main Propulsion System (MPS)
The MPS pressurizes the propellant tanks
The GCS sends a command to start the engine
The engine ignites
The GCS sends a command to start the second engine
The second engine ignites
The GCS sends a command to start the third engine
The third engine ignites
The GCS sends a command to start the boosters
The boosters ignite