Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) 3
Confusion; Situational Awareness; Training / Qualification; Communication Breakdown; Troubleshooting
Conflict Airborne Conflict; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors; Aircraft; Procedure
Aircraft X and Aircraft Y both released by approach.  Aircraft X launched 'Runway heading' off RWY 8R and climbing to 7000.  Aircraft Y was launched after Aircraft X had crossed departure threshold of runway 8R also runway heading and 7000.  Aircraft Y increased speed such that he was overtaking Aircraft X.  Aircraft X had been switched to departure frequency.  I called departure controller requesting a turn for Aircraft Y and advising I could maintain visual separation in the turn.  I was told to keep Aircraft Y on runway heading and then I shipped him to departure.It is quite possible; due to the nature of traffic at PUB; to never encounter this situation during training.  Given that both aircraft perform similarly I thought I had provided adequate spacing.  I was wrong.  I would recommend a wedge of departure airspace 15-20 degrees to either side of runway heading to allow tower controllers to issue turns in for IFR departures should it be necessary to maintain spacing.  Another recommendation would be to only release one IFR at a time; or some other similar measure to help ensure IFR separation is maintained with multiple IFR departures.
PUB Tower Controller reported of departing two similar type aircraft and the second aircraft over taking the first.