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Bloody
Mar 3, 2013



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

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Do Not Fear Jazz
Feb 1, 2005

W-WHAT DO YOU MEAN YOU DON'T LIKE MY POST?



How far away can you feel the heat off of those things

Bloody
Mar 3, 2013



Pretty far but you probably die from the acoustic energy before it matters

Do Not Fear Jazz
Feb 1, 2005

W-WHAT DO YOU MEAN YOU DON'T LIKE MY POST?



I have really big ear muffs

Bloody
Mar 3, 2013



It's more the lungs than the eardrums

Powered Descent
Jul 13, 2008

We haven't had that spirit here since 1969.



Who would win in a bar fight, BE-4 or Raptor?

And if an SSME walked in on the fight, whose side would it take?

The Scientist
Nov 6, 2009



Ramrod XTreme

Did you work at Cape Canaveral?

Bloody
Mar 3, 2013



The Scientist posted:

Did you work at Cape Canaveral?

No

Bloody
Mar 3, 2013



Powered Descent posted:

Who would win in a bar fight, BE-4 or Raptor?

And if an SSME walked in on the fight, whose side would it take?

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

Farmer Crack-Ass
Jan 2, 2001

~this is me posting irl~


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?


how do the sensors and computers talk to each other on the rocket? do the sensors send packets of data or is it like voltages and poo poo?


how big a MIRV bus could you throw with one of them there BE-4s?

FFT
Dec 28, 2005

Keyboard Cowboy



Bloody posted:

Pretty far but you probably die from the acoustic energy before it matters
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?

Assuming it's still in test mode and firing parallel to the ground.

Bloody
Mar 3, 2013



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?

Assuming it's still in test mode and firing parallel to the ground.

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

Bloody
Mar 3, 2013



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?


how do the sensors and computers talk to each other on the rocket? do the sensors send packets of data or is it like voltages and poo poo?


how big a MIRV bus could you throw with one of them there BE-4s?

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

Anne Frank Funk
Nov 4, 2008



How serious is bezos about putting logistic space stations in orbit to achieve 1hr worldwide delivery time?

Dr. Fishopolis
Aug 31, 2004

ROBOT



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?

Bloody
Mar 3, 2013



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

Bloody
Mar 3, 2013



here is my favorite resource on failures
https://c3.nasa.gov/dashlink/static/media/other/Introduction1.html

just look at all of these!

Drone_Fragger
May 9, 2007

VOTE
FOR
PEDRO


what bolts do you have to use or specify?

Weka
May 5, 2019

And if you gaze long into an abyss, you will say `look, no ring.`

Could I make a small one of these to strap to the back of my truck? How much does this thing weigh could I just put one of these on it?

Meydey
Dec 31, 2005


Technically I'm a Blue Origin Rocket Scientist also. Took my A+ test in an empty building in Kent, Wa in like 2000. Bezos later bought that building and made it SpaceX HQ. Close enough for me.

Bloody
Mar 3, 2013



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

prisoner of waffles
May 8, 2007

Ah! well a-day! what evil looks
Had I from old and young!
Instead of the cross, the fishmech
About my neck was hung.


Bloody posted:

here is my favorite resource on failures
https://c3.nasa.gov/dashlink/static/media/other/Introduction1.html

just look at all of these!


That image is not very readable so I googled this up:
https://sma.nasa.gov/SignificantIncidents/

KOTEX GOD OF BLOOD
Jul 7, 2012



Bloody posted:

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
This one is probably a dumbo question but how do they hold those engines in place when they're testing them on the ground?

Bloody
Mar 3, 2013



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 17:36 on Mar 1, 2021

Farmer Crack-Ass
Jan 2, 2001

~this is me posting irl~


Bloody posted:

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

Bloody probably already knows this but before Challenger was destroyed, all the astronauts were way more terrified of the SSMEs than the SRBs

JAY ZERO SUM GAME
Oct 18, 2005

Walter.
I know you know how to do this.
Get up.




Bloody posted:

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

cool, ty

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Discussion Quorum
Dec 5, 2002
Armchair Philistine


I got to watch a couple of SSME tests at Stennis as a kid, including one at night, and it was the coolest drat thing. You can't really see the engine, but it's a big fuckoff concrete bunker belching insane amounts of steam.

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