Soon
Defeat Vex with No Time to Explain in Nexus, Infinitude, and The Glassway on Europa.
The Exo Stranger needs your help calibrating the weapon so that she can alter it. The best way to get the data she needs is by defeating Vex.
"I've been thinking about what these schematics imply: a mass driver capable of firing rounds greater than relativistic speeds? This wasn't meant to fight something on Europa, so… what was Clovis planning to aim it at?" —Ghost