antiterror13
Brigadier
What do you mean "how"?
The UVLS is a modular system that is designed from the outset to be able to pack more than one payload in a cell.
A multipack approach (whether quadpack or dualpack or otherwise) can use either a cold launch approach (separate cold launch mechanism for each individual payload) or a hot launch approach which would be some variation of having a concentric venting system like the UVLS launch of YJ-18.
For both approaches, each individual payload in the multipacked cell will sit in its own housing/subcanister.
What I meant, HHQ-9C diameter is estimated at 450–500 mm, I don't see how it can be quad packed on UVLS with the size of 850 mm × 850 mm square