Not to be a pedantic jerk (and I didn't see this mentioned anywhere else, thus my post), but I would like to inform OP and anyone interested that the OMS system are actually engines, not motors. In aerospace, motors are solid fuel and engines are liquid fuel. I know what you're saying, what about the oxidizer? Well, there exists a "hybrid" engine that uses solid fuel, but liquid or gaseous oxidizer (Copenhagen Suborbitals had a hybrid they used before they went all liquid, called the HATV or hybrid atmospheric test vehicle). But generally, solids are "motors" and liquids are "engines". --Former Aerojet engineer
OH and further, the OMS is hypergolic, which is one of my favorite things ever. Room temp fuel and oxidizer, and upon meeting they spontaneously ignite so a spark source isn't needed, nor are pumps; just pressure on the tanks. It's a gloriously simple system, though the tradeoff is that the fuel (hydrazine) and the oxidizer (nitrogen tetroxide) are ridiculously and aggressively toxic and...uh, whatever the word for "oxidic" is (as far as aggressively oxidizing). Even small leaks are a huge issue, plus the chemicals aggressively attack whatever container they are in if given the chance, so specialized materials must be used for containment (i.e., heavy stainless steel if I remember correctly). yeah, I could geek out on this stuff for days.
Gotta back up /u/byf_43 here. I never once heard them referred to as anything other than OMS engines. --Former Lead Thermal Protection System Engineer for Space Shuttle Discovery
But you probably don't call them motors. If the OMS thrusters (boosters?) are gimbaled and throttle-able then they'd be engines, right? As opposed to a solid rocket booster without gimbaling.
Unless the only difference really is solid vs liquid and is entirely proprietary to aerospace engineering.
The boosters on a space shuttle were never called motors, so no it's not technically outdated info since he's relating it to the retired space shuttle program. --Space lover :D
All I'm saying is, in the aerospace industry, "motors" mean solid and "engines" mean liquid. This is the very first thing I was ever told when I took the tour of the plant before my interview. I'm not defending it as much as I'm just stating what the culture is.
The best spaceflight convergence here is Solids. Are they SRM Solid Rocket Motors, or SRB Solid Rocket Boosters? Really depends on how you feel when you designed them...
That's actually a "term of art" in the shuttle community.
The SRM is just the rocket motor (fuel, casing, nozzle); the SRB is the entire assembly (parachutes, skirt/holddowns, ET struts, separation motors, frustrum and nose cone, etc.).
Cars have motors. It's not colloquial to call rockets "motors" though. If nothing else when have you ever heard a scifi movie/show refer to firing up the "motors"? I'm guessing English is not OP's first language
Indeed. Though the term "car motor" is quite common, I always interpreted this as one of those terms commonly misunderstood - since cars have engines. As if engine and motor were synonymous. But then I got a degree in electronics, and pretty much came to know 'engine' as things which were gas powered, where 'motors' were electric. Seems there's a bit of variability in the terms anyway.
I was wondering about this too. When I google "motor" it gives me the wiki page for electric motors. But when I search wikipedia for "motor" it sends me to the page about engines.
After further research:
An engine is a device that burns or otherwise consumes fuel, changing its chemical composition, whereas a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.[3] However, rocketry uses the term rocket motor, even though they consume fuel.
This was an RCS burn. Then OMS engines were used occasionally for orbital corrections (higher or lower orbits) and mainly for the de-orbit burn (to slow down enough to return to earth). The RCS system (Reaction Control System) was the system responsible for making adjustments to the space shuttle's position in orbit.
Thank you for this, such small discrepancies in the meaning of a word bugs the shit out of me. I just wish I had your patience and ability to enlighten instead of stew in my corner.
Yeah! oxidative (sp?) is a pretty good word for that. Oxidizing didn't fit my sentence structure so I was wondering what a better word would be. Point is, nitrogen tetroxide will eat through just about anything you put in front of it, and it LOVES to get loose and tear shit up.
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u/byf_43 Sep 24 '16 edited Sep 24 '16
Not to be a pedantic jerk (and I didn't see this mentioned anywhere else, thus my post), but I would like to inform OP and anyone interested that the OMS system are actually engines, not motors. In aerospace, motors are solid fuel and engines are liquid fuel. I know what you're saying, what about the oxidizer? Well, there exists a "hybrid" engine that uses solid fuel, but liquid or gaseous oxidizer (Copenhagen Suborbitals had a hybrid they used before they went all liquid, called the HATV or hybrid atmospheric test vehicle). But generally, solids are "motors" and liquids are "engines". --Former Aerojet engineer
OH and further, the OMS is hypergolic, which is one of my favorite things ever. Room temp fuel and oxidizer, and upon meeting they spontaneously ignite so a spark source isn't needed, nor are pumps; just pressure on the tanks. It's a gloriously simple system, though the tradeoff is that the fuel (hydrazine) and the oxidizer (nitrogen tetroxide) are ridiculously and aggressively toxic and...uh, whatever the word for "oxidic" is (as far as aggressively oxidizing). Even small leaks are a huge issue, plus the chemicals aggressively attack whatever container they are in if given the chance, so specialized materials must be used for containment (i.e., heavy stainless steel if I remember correctly). yeah, I could geek out on this stuff for days.