IGN shows you how to unlock an infinite amount of your super ability during the Nessus strike in the beta for Destiny 2.
Once on Nessus, wait near where you initially spawn into the world until you can steal a Pike vehicle from some passing Fallen. Once you’ve got your Pike and have a charged Super, simultaneously initiate your super move and get onto the Pike – you may need a few tries to get the timing right, but when done correctly you’ll notice that you have your Super active while also sitting on the vehicle. Jump into your inventory and swap your primary weapon once, then back again, then exit the menu to the world and get off the Pike. You’ll now be able to use your super continuously until your next death or loading screen.