Apollo 14 LOI Burn: OXID FLOW VLV to INCR?

[Wedge313]

Hi,

Quick procedural question: Just prior to the LOI burn the Apollo 14 checklist has a step "OXIDIZER FLOW VALVE INCR-INCR (VERIFY)". During the burn this quickly result in an imbalance between the fuel and oxidizer. It didn't look "normal" to me so I balanced out the fuel and oxid then left the valve in NORM for the rest of the burn.

I don't remember putting this switch to INCR for other LOI burns (or any SPS burns for that matter). What was the reasoning for this?

Thanks

 

[rcflyinghokie]

Looks like they added this to the procedures for 14 based on results of unbalanced mixture ratios from previous SPS firing. 8-12 seemed to have a less than desirable mixture ratio at the end of the mission. For 15-17, the valves were actually redesigned to inherently correct for this, so like many things, 14 served as a test bridge for many J mission changes to the spacecraft.

In NASSP, we don't have that problem simulated, so leaving it in INCR too long will unbalance things. You can use the switch though and monitor the increase/decrease and balance it back.