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Variable thrust through changing the number of engines burning, or through propellant throttling, or other means is often/usually done to reduce maximum aerodynamic stresses on the rocket as well as to reduce maximum g-force experienced by the payload, which is sometimes human.

Question: Has an object ever been put into Earth orbit by a rocket where the first stage was always running at maximum thrust?

Ignore small variations in thrust due to Isp sensitivity to atmospheric pressure, maximum should mean maximum at that pressure.

Ideally, for the purposes of this question, it would be a rocket without boosters, since boosters running out of propellant is one way to reduce thrust.

Also, I won't rule out a whole class of propellants, but tuning the 3D structure and composition of a solid propellant (for solid or hybrid engines) could be tuned to produce a modulated thrust, and so a solid propellant 1st stage which lowers thrust to reduce maximum aerodynamic stresses should be ruled out as well.

note: I'm not asking if it would be a good idea to do so. I'm guessing that not all rockets always had provisions for variable thrust, or for shutting down engines sequentially.

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    $\begingroup$ I'm trying to find confirmation, but I believe the Saturn V F1 engines were not throttable, which would imply the first stage was always running at maximum thrust. $\endgroup$ – Carlos N May 17 '18 at 13:32
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    $\begingroup$ Good point. Saturn V turned off its center engine early to reduce thrust. Probably need to look at single-engine birds like Juno $\endgroup$ – Carlos N May 17 '18 at 13:42
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    $\begingroup$ It seems like your question refers to liquid engines, but you may wish to specify this. A number of launch vehicles exist that use only solid rocket boosters (e.g. Arianespace Vega, most (all?) of Orbital ATK's launchers) which cannot be throttled so the lazy answer to your question would be to refer to these! $\endgroup$ – Jack May 17 '18 at 13:44
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    $\begingroup$ @Jack Thanks! I think "...and the 3D structure and composition of solid propellants can be tuned to produce a modulated thrust..." could be used rule that out, so I've adjusted the wording to apply that restriction, rather than specify liquid only. I don't want to needlessly pre-rule-out a good answer. $\endgroup$ – uhoh May 17 '18 at 13:53
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    $\begingroup$ @jack - most solids have their grain shaped so as to manage thrust levels. not throttling, but definitely thrust management which was the intent of the question. But it is a valid edit to focus on liquids $\endgroup$ – Carlos N May 17 '18 at 17:33
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I'd guess almost all rockets earlier than Saturn I ran the first stage at full throttle throughout. (Saturn I shut off 4 of its 8 first-stage engines to limit acceleration near the end of the burn.) Redstone and Titan absolutely; Atlas if you don't consider the booster engines.

I don't have positive citations, unfortunately; if you don't throttle a stage down you don't talk about throttling. Titan was designed as an ICBM, and g-force on Gemini flights peaked at a very uncomfortable ~7g; if they could have throttled down, they would have.

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    $\begingroup$ I see what you mean about finding sources for early non-existence. $\endgroup$ – uhoh May 17 '18 at 16:21
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    $\begingroup$ I didn't know that the Gemini astronauts experienced ~7g, wow! $\endgroup$ – uhoh May 19 '18 at 0:39
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    $\begingroup$ Almost 7.5! I found a time series plot from Gemini VIII and added it to the linked answer. $\endgroup$ – Russell Borogove May 19 '18 at 1:05
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    $\begingroup$ I've just asked What is BECO? (Gemini) Same as MECO? $\endgroup$ – uhoh May 19 '18 at 1:41

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