For my robotic project I'm going to use the BBB as "voice module" using

For my robotic project I’m going to use the BBB as “voice module” using sphinx by CMU.
The SW framework of my project is based on Qt5 toolkit, I use Qt Sockets (TCP and UDP) for servers (control, configuration and video server) and for clients.
Since Qt5 is not light as space occupation, I would like to install Ubuntu (I do not know Angstrom) on external SD Card, but booting pressing “boot” button is not useful.
Is there a way to boot automatically from SD card without pressing boot button?
Thank you
Walter

PS my project is here: http://myzharbot.robot-home.it