3 ms·
FTA: “...instead of a mechanical check valve (simple but still not 100% passive), the barrier between pressurant and oxidizer (as well as fuel, most likely) wil
by black6 7y ago
FTA: “...instead of a mechanical check valve (simple but still not 100% passive), the barrier between pressurant and oxidizer (as well as fuel, most likely) will be replaced with something known as a burst disk.”
A burst disk comes from a different concept than a check valve. With a check valve, one presumably desires a fluid flowing in one direction—in this case the pressurant for the oxidizer vessel—and no back flow. In the rocket engine industry this setup tends to be used to maintain cleanliness. A burst disk, however, embodies the same concept as a relief valve—it prevents the pressurization of a system above its rated capacity. I fail to see how replacing a check valve with a burst disk fixes the problem and maintains the same system capability.
- lutorm 7y agoI think the idea is that the system is never intended to be depressurized once it's pressurized, so you don't need a check valve, you just need something to prevent backflow before the system is pressurized.
- black6 7y agoAha. I have a better understanding after reading the actual SpaceX presser[0]. The SuperDraco thrusters are to be used only for a launch escape scenario, so they would only be used once before a ground refit of the capsule. That being the case, a burst disk does make sense as a replacement for a check valve. 0: https://www.spacex.com/news/2019/07/15/update-flight-abort-static-fire-anomaly-investigation https://www.spacex.com/news/2019/07/15/update-flight-abort-s...
- Mvandenbergh 7y agoThe reason why they have a check valve is that the design was originally designed to be re-lightable for purposes including but not limited to abort. At this point, NASA only wants them used for abort so a burst disk is a simpler design but I guess they never updated the design to reflect the restricted purpose. That would fit with SpaceX's general design philosophy of building re-usability in well before the systems are actually due to be re-used.