|
I worked on this thing for a while but don't any more https://youtu.be/Nyn2gOimRfM Ask me about rocket engines and avionics and I'll answer unless it violates ITAR or ndas or I forget about this rsf
|
#
¿
Feb 23, 2021 03:46
|
|
|
|
| # ¿ Apr 24, 2024 09:11 |
|
|
Pretty far but you probably die from the acoustic energy before it matters
|
|
#
¿
Feb 23, 2021 03:52
|
|
|
It's more the lungs than the eardrums
|
|
#
¿
Feb 23, 2021 03:54
|
|
|
The Scientist posted:Did you work at Cape Canaveral? No
|
|
#
¿
Feb 23, 2021 04:23
|
|
|
Powered Descent posted:Who would win in a bar fight, BE-4 or Raptor? In a bar fight? Be-4, it's bigger. Ssme is their ungendered parent engine, so idk. maybe also be-4, because it looks more like them
|
|
#
¿
Feb 23, 2021 04:25
|
|
|
FFT posted:How far away would someone need to be to not die? Say for one person perpendicular to the nozzle and another person just facing the nozzle head-on? no idea tbh. I wouldn't want to stand much closer than, like, 2 miles probably, but that's more about when things explode than when they go right
|
|
#
¿
Feb 23, 2021 17:49
|
|
|
Farmer Crack-rear end posted:is there a central flight computer that receives input from all the sensors and commands the engine mechanisms for ignition/throttle/gimbaling/etc? or is there a specific engine control computer and the engine I/O goes to the engine computer and then the engine computer talks to some other computer? avionics architectures are a big pile of tradeoffs. avionics mass is driven by harnessing, some aspects of complexity are driven by box count, sensed signals can be weak in a super noisy environment, actuators can take lots of electrical power, and distributing power and data is its own mess. One mega-flight-computer would be easier to work with in some respects (you don't have to worry about distributed systems problems as much) but I think at this point it has enough downsides that I'd be surprised if its really used in any significant modern vehicle. Things like dedicated engine controllers have been common since the space shuttle program. There's a lot of ways to skin a cat but at the end of the day you want the system coherent on "when should the engines ignite" and "when should the hold downs release". Lots of little tradeoffs that ultimately look kinda like complexity vs performance - how can you build the most performant (reliable, fault-tolerant, lowest mass) avionics system with as little complexity (time, money, testing burden) as possible. The vast majority of this complexity is driven by fault tolerance, reliability, and reusability. You can fly a rocket with just a couple of sensors and actuators, but to ensure that its operating safely and to know if you can reuse it safely you need a lot more insight. Reusable boosters pretty much doubled (or more) complexity, too - vehicles like saturn V had the instrument unit directly below the payload, but a vehicle like falcon heavy has a full suite of avionics systems on each booster core plus the second stage. Sensors are typically analog measurements (think thermocouples and pressure transducers), and computers typically talk over digital buses. 1553 is the battle-hardened veteran of shuttle and ISS, but there's lots of interest in more modern point-to-point networking technology like AFDX and ethernet. As for MIRVs I am not sure but I would guess Quite Large
|
|
#
¿
Feb 23, 2021 18:19
|
|
|
Dr. Fishopolis posted:what's the optimum altitude for that nozzle? how do you decide the flare? does the coolness of the shock diamonds at sea level factor into that decision? not sure, I'd guess not that far above sea level given that it's a booster engine. I'd guess that people smarter than me could figure it out from the publicly available data on the engine tho shock diamonds do rule
|
|
#
¿
Feb 23, 2021 20:06
|
|
|
here is my favorite resource on failures https://c3.nasa.gov/dashlink/static/media/other/Introduction1.html just look at all of these! 
|
|
#
¿
Feb 24, 2021 18:33
|
|
|
Weka posted:Could I make a small one of these to strap to the back of my truck? yes Weka posted:How much does this thing weigh could I just put one of these on it? probably not
|
|
#
¿
Feb 24, 2021 23:54
|
|
|
a lot of concrete + steel. This nasa thing has some words + pictures about the SSME setup https://www.nasa.gov/centers/marshall/about/star/star130612.html but basically you just gotta build a big rear end building that can react the loads of a rocket engine at full thrust (plus whatever safety & design margins you're using) that, ideally, won't be harmed / destroyed by whatever your idea of a worst-case failure of your test article looks like. fortunately, these two requirements kinda go hand in hand. the actual holding in place can either use test specific interfaces, like this gas generator being tested at marshall:  or if it's a flight assembly you can use the flight interfaces, which have to be able to handle the loads involved anyway here's half an hour of SSME failures to get some idea of what those can look like. the worst ones are where it goes from "that looks like an engine" to "that is solid white" in one frame. https://www.youtube.com/watch?v=YzUgq14kBwA and here's a neat cross section of the F-1 test stand I just came across https://commons.wikimedia.org/wiki/...et_7_of_15).tif Bloody fucked around with this message at 18:36 on Mar 1, 2021 |
|
#
¿
Mar 1, 2021 18:31
|
|
|
Yeah trying to not be too specific here but generally the goal is to reduce the mass flow rate of your propellants in an equal ratio so you've got a few options there: reduce the flow rates directly with main ox/fuel valves or reduce pumping by throttling down whatever is powering your pump. Tricky parts of throttling are around like maintaining combustion stability, not cavitatimg or otherwise loving up turbomachinery, and not grossly over expanding your nozzle flow. Also just the usual engine problems around keeping temperatures and pressures everywhere within tolerances or whatever, but that's pretty much table stakes
|
|
#
¿
Mar 27, 2021 04:30
|
|
|
Trying to remember exactly how ssme throttled but I don't remember offhand maybe this lengthy pdf mentions it? https://ntrs.nasa.gov/api/citations/20120001539/downloads/20120001539.pdf?attachment=true
|
|
#
¿
Mar 27, 2021 04:32
|
|
|
|
| # ¿ Apr 24, 2024 09:11 |
|
|
Throttling is easier in a vacuum because over expansion isn't an issue
|
|
#
¿
Mar 27, 2021 05:16
|
|