As Sandman says, the Estes Electron Beam can be readily modified to operate with a 12 volt battery, but this is not necessary for any kits that Estes has sold, the largest of which is a 3 motor cluster.
You might want to go to the Estes Educator site, https://www.esteseducator.com/cfusion/publications.cfm
to get some further info.
Estes ignitors have a resistance of 0.8 ohms and require 2 amps to fire, so using Ohm's law we can calculate minimum all fire voiltage of only V=ri=0.8x2=1.6 Volts! The Estes Electron beam launcher used 4 AA batteries supplying 6 volts, so voltage is not the problem. Current is!
Using Ohm's law, we can figure out the current that can be supplied by the launcher into an ignitor. It will depend on the internal resistance of the batteries, the resistance of the wires, and the switches, and the ignitors.
A fresh Duracell AA battery has an internal resistance of 0.12 ohms, so the resistance of 4 batteries in series is about 0.5 ohms.
The resistance of the controller is probably 1 ohm or less, even if the clips are old.
Let's solve the problem for 1 ohm, and then for 0.5 ohms, and then for the actual values.
The maximum curernt draw is a zero ohm ignitor. This assumption is close to what you get with a cluster. (The Resistance of 1, 2, 3, 4 and 5 Estes ignitors are: 0.8, 0.4, 0.26, 0.2, 0.16 ohms respectively.)
So to calculate the delivered current we again use ohms law solved for current: i=V/r=6/(0.5+1)=6/1.5=4 amps, so if the launcher resistance is 1 ohm, you will definately fire 1 ignitor, probably fire 2, but definately not 3.
If the launcher resistance is 0.5 ohms, i=V/r=6/(0.5+0.5)=6/1=6 amps, and you can fire definately fire 2 ignitors, and maybe 3 ignitors.
The actual resistance of the Estes Electronbeam Launcher is about 0.36 ohms if the clips are clean. so with fresh standard AA batteries, you can deliver i=V/r=6/(0.5+0.36)=6/0.86= 7 amps, or 2.3 amps per ignitor, so all 3 fire.
A pretty good minimum cost engineering design, since the largest cluster sold by Estes is a 3 motor cluster.
and you'll learn how to answer these questions.