I wanted to know that there have been a handful of literature that mentions vent openings in the rocket payload fairings. However, none specify the kind of valves used in those fairings? does anyone know what valves are used in such fairings and how do they operate?
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$\begingroup$ Different but related: Pressure inside a launch fairing - falcon 9 and Why not use alternative/low-pressure atmospheres in fairings during launch? and Could a fairing vacuum protect the payload from acoustic loads? and Why not use alternative/low-pressure atmospheres in fairings during launch? $\endgroup$– uhohAug 18, 2021 at 0:43
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2$\begingroup$ AFAIK, they are just holes with a specific size and location. No moving parts. $\endgroup$– AJNAug 18, 2021 at 1:21
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1$\begingroup$ Could you please provide a link to some of the literature you have seen? $\endgroup$– AJNAug 18, 2021 at 12:14
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1$\begingroup$ yes, AJN, there is NASA famous paper with the title Compartment venting SP-8060. then there is paper on korean SLV , ntrs.nasa.gov/api/citations/20090034248/downloads/… . ntrs.nasa.gov/api/citations/20090034248/downloads/… ist.edu.pk/downloads/jst/previous-issues/july-2018/… $\endgroup$– ShamoonAug 19, 2021 at 4:41
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1$\begingroup$ Why would there be a valve? The vent is never shut, is it? The Shuttle had cargo bay vents with doors, but they needed to contend with re-entry. $\endgroup$– WoodyNov 24, 2023 at 3:25
1 Answer
Answer: Butterfly Valves.
I found references to both valved and unvalved payload fairing (PLF) vents. Apparently the valves (if used) control the rate of pressure drop. Within the PLF are a number of compartments. If the rate of pressure drop exceeds their ability to vent, it places stress on those compartments. Consider honeycomb panels. Every cell in the honeycomb has its own vent hole. The payload may also have limits on pressure drop rate.
The Falcon9 limits PLF pressure drop rate. From the User's Manual:
Inside the Falcon launch vehicle, the payload fairing internal pressure will decay at a rate no larger than 0.40 psi/sec (2.8 kPa/sec) from liftoff through immediately prior to fairing separation, except for brief periods during flight, where the payload fairing internal pressure will decay at a rate no larger than 0.65 psi/sec (4.5 kPa/sec), for no more than 5 seconds.
https://www.spacex.com/media/falcon-users-guide-2021-09.pdf p38
At the same time, the PLF vent rate needs to be high enough to keep the pressure differential on the PLF within design limits. Butterfly valves are used to keep pressure drop rates within specified limits.
The performance characteristics of a vent valve with a spring-loaded door has been evaluated for Korea space launch vehicle-II by Oh et al., [18]. Singh [19] https://www.researchgate.net/publication/324163616_Vent_Valve_for_Test_Launch_Vehicle_of_Korea_Space_Launch_Vehicle_II
https://saspublishers.com/article/6033/download Scholars Journal of Engineering and Technology Review of Vent Systems of Space Vehicle, Spacecraft and Aircraft Fig 17 shows housing and butterfly valve
This spring-loaded butterfly valve bears a striking resemblance to the common barometric damper found on boiler chimneys. These are designed to self-regulate the pressure difference across the wall of the flue pipe. In PLF, the butterfly valve serves the same function: it maintains a constant pressure difference across the wall of the PLF as the ambient pressure falls.