either they were on or they were off

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chopin7

Senior Member
Albanian
Hello

It's a documentary about moon machines.
Narrator is talking about rocket engine built with a throttle.
And some historian says,
"Up untiI this point in history, no one had ever built
a rocket engine with a throttIe.
Either they were on,
or they were off."

I am having trouble with the last sentence.
To what refers "they"?
Engine or throttle? In total, it's a bit foggy to me.

Thank you
 
  • Egmont

    Senior Member
    English - U.S.
    "They" are the rocket engines without throttles. Throttles that were never built are neither on nor off.
    Right. If a rocket engine (or any other engine) has no throttle, its fuel supply cannot be adjusted. It is either off (not running at all) or on (running at full power). There are no intermediate states. Rocket engines (or any other engines) that have throttles can operate at partial power. This is important for controlling any vehicle: imagine if automobile engines were either on (at full power) or off (shut down). It would be impossible to drive them under most conditions.
     
    Last edited:

    Forero

    Senior Member
    Not exactly. If a rocket engine (or any other engine) has no throttle, its fuel supply cannot be adjusted. It is either off (not running at all) or on (running at full power). There are no intermediate states. Rocket engines (or any other engines) that have throttles can operate at partial power. This is important for controlling any vehicle: imagine if automobile engines were either on (at full power) or off (shut down). It would be impossible to drive them under most conditions.
    Aren't you saying the same thing as Myridon?
     

    Myridon

    Senior Member
    English - US
    ... that have throttles can operate at partial power.
    If they don't exist, they can't operate at any power. I was pointing out that the "they" in the sentence cannot logically be "throttles" because there were no throttles on the rockets at the time referred to in the sentence.
     

    Egmont

    Senior Member
    English - U.S.
    Aren't you saying the same thing as Myridon?
    As I re-read his post, I think I am. I had misunderstood the intent of his comment about how missing throttles can't be on or off. I've edited my post to make this clear. The original version, of course, is preserved in the quote in yours.
     

    pwmeek

    Senior Member
    English - American
    Note that until the time of the first lunar landers, throttling a rocket was thought to be impossible (as per post #1 example). What made the landers possible was the development of ways to throttle rockets, which is what that example was explaining: that previous to the landers, rockets were either on (at full power) or off (shut down to zero power).

    In fact, it wasn't long before this time that it was considered impossible to restart a rocket once it was shut down, or at least difficult to do it reliably.
     
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