Valves

How to incorporate the new valve is an integration issue.

Incorportion of EMA - early in development "designing valves to be driven by electric 
actuators."

How to accomodate fault tolerance - redundant electric actuators.

EMAs can vary rate of travel - e.g., command to 60% by electric controller. The valve stops 
moving when feedback indicates it is at 60%.

Oxidizer LOX and fuel LH2 are triggered on how pumps work - pumps discharge pressure.
Effects on trigger level is important. Don't want to change excessively. RL-10 overdesigned 
originally. In use 30 years, upgraded to extend operating regime. Design problems are not 
faced before they crop up.


EMA valves soften starting jolt
This feature has been demonstrated
Vehicle - already designed for maximum start/stop loads
Payload - must be designed for max start/stop loads

What about future customers? EMAs might be useful.


Valve timing
EMAs allow slower transitions from full open (FO) to full closed (FC).

Ox flow control valve
Oxidizer from flow control valve. The valve goes from FO to FC in .25sec with old valves.
Slow from FO to FC to 1.5 sec with EMAs. Makes for more predictable, smoother starts using 
the slower transition.

The controlling valve controls the way the pump accelerates when the engine comes up.

RL-10 - determine the sequence of valves to bootstrap: heat energy of gasefying the LH2 as 
it flows through the thrust chamber starts the turbine which drives the pumps.


Opening and closing timing
Developed by trial and error (~get more info)
Initially difficult to simulate
Simulated EMA worked very well.
Thrust Control was EMA. Others were hydraulically actuated ball valves. Behaved like EMAs.

Slew rate - rate that valves could open or close. (~I think) the ball valves behaved like 
EMAs with the Thrust control an EMA. Similarities:
- flow vs position
- flow vs time

Timing may be changed by changing spring weights, but still done by trial and error (~test 
firings with various timings - ask)
More on valves - EMAs:
- Fuel shutoff
- Oxidizer Control
- Thrust Control
Cooldown valves through pumps - overboard on prestart.