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I am reading this article about DSCOVR which links (ref 16) to this: DSCOVR: Mission Success for Moog Engines Over a Decade Later , about the recertification by MOOG of the MONARC 5N monopropellant engines and thruster valves.

When I read these two, I don't understand - are there both engines and thrusters? Could someone explain the distinction - and possibly locate a clear diagram with DSCOVRs various propulsion elements used for the mid-course correction (MCC), Lissajous orbit insertion (LOI), and all station-keeping tasks? Here is a sample paragraph from here:

"The 5N engines will be used for attitude control and minor adjustments to maintain the satellite’s Lagrange-1 (L-1) orbit one million miles from Earth; DSCOVR is the nation’s first operational spacecraft in deep space. DSCOVR has two key burns: Mid-Course Correction (MCC) and Lissajous Orbit Insertion (LOI). The thrusters will be used to perform the MCC for 50 minutes and LOI for 5.3 hours. After reaching L-1, DSCOVR will perform station-keeping and momentum unloading with the thrusters."

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  • $\begingroup$ Here is a follow-up question $\endgroup$ – uhoh Mar 1 '16 at 10:03
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In this case, the terms are being used interchangeably. DISCOVR has one type of engine, i.e. the MOOG Monarc 5N thruster.

DSCOVR is equipped with ten thrusters that can be used for spacecraft attitude control as well as translational maneuvers that are required for mid-course corrections and orbital adjustment maneuvers around L1. Ten thrusters are fed from a pressurized Hydrazine tank, making use of the catalytic decomposition of hydrazine over a metallic catalyst bed to create a hot gas that generates thrust. With a total propellant mass of 145 Kilograms, the mission has a total delta-v budget of 600m/s which is sufficient for the transfer to L1, orbital adjustment maneuvers and regular reaction wheel momentum dumps.

A more common usage is to use the term "engines" for large, main propulsion units, and "thrusters" for small units that do maneuvering and attitude control.

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  • $\begingroup$ Thank you, that helps a lot! For the part: "...and possibly locate a clear diagram..." I'll break it out as a separate question. $\endgroup$ – uhoh Mar 1 '16 at 9:44
  • $\begingroup$ Here is the follow-up question $\endgroup$ – uhoh Mar 1 '16 at 10:02

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