Using L:
* Luminous launch: This creates a sense of brightness and excitement.
* Lucid launch: This suggests a clear and well-planned launch.
* Leaping launch: This emphasizes the suddenness and power of the launch.
Using other letters:
* Boldly, they breached the barrier and launched their vessel.
* With a powerful roar, the rocket launched skyward.
* The company launched its new product with a vibrant campaign.
You can also use alliteration with words related to "launch":
* The rocket roared, ready for its launch.
* The spaceship soared, propelled by a powerful launch.
* With a brilliant flash, the fireworks launched into the night sky.
The best alliteration for you will depend on the context and the specific message you want to convey.