A penetrator assembly for penetrating a bone marrow comprising: a hub having a first end, a second end, a passage extending from the first end to the second end, and a flange extending radially outward from the second end; an outer penetrator extending from the second end of and in fixed relation to the hub, the outer penetrator defining a longitudinal channel in communication with the passage of the hub; a connector having a first end and a second end that is configured to be coupled to the first end of the hub, the first end configured to be releasably coupled to a drive shaft of a driver such that the driver can rotate the connector and the hub to drill the outer penetrator into a bone and associated bone marrow; where the flange is configured to stabilize the hub against tissue overlying the bone when the outer penetrator is disposed in the bone.