# The changes of a throttled Merlin-1d engine

With Merlin-1d being able to throttle down from its full thrust potential, this post about its throttle capability does not mention much of its change in performance. On the Wikipedia page of Merlin-1d, there is a piece that says

the Merlin 1D Vacuum can throttle down to 39% of its maximum thrust, or 360 kN (81,000 lbf).

While this on the surface may seem like a "duh" definition question, especially with the quote above, but does 70% literally mean 70% of its 914 kN (vac.) 100% ability?

Thanks

• @uhoh Am I anywhere close with throttle thrust? Is 70% of 914kN simply 639kN? I don't actually believe it is just that simple to be true. Commented Dec 30, 2018 at 1:17
• Oh -- are you just asking if throttle percentage is the same as thrust percentage? Commented Dec 30, 2018 at 1:21
• I don't know for sure, but I would guess that the 39% and 70% are relative to whatever the thrust happens to be at the altitude where the engine happens to be. If the throttling happens at sea level, then it's 39% and 70% of 845 kN.
– uhoh
Commented Dec 30, 2018 at 1:22
• @RussellBorogove I am mainly looking to find out how throttling effects the engine in terms of output. With apologies to repetition, I am just looking to see how accurate percentage relates 0-100%. Commented Dec 30, 2018 at 1:34
• @UndefinedUsername I think throttling figures are normally given as percentage of maximum (or nominal) thrust. Propellant flow rates (the actual thing being throttled) shouldn't be too far off the same percentage, but probably not exactly the same. Commented Dec 30, 2018 at 1:59