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I am looking for details on the Space Shuttle Orbiter Vernier Reaction Control System (VRCS), used for fine maneuvers on orbit, such as docking. Wikipedia has very little information on the system. Googling the topic finds no pages devoted exclusively to the system.

I'm especially interested in the placement of the thrusters, and the force that each could provide. How were the thrusters arranged on the vehicle? Obviously there were no thrusters on the ventral face, as that would interfere with the heatsheild. So how less efficient were the canted thrusters? How accurate were the thrusters?

Other than this beautiful view of Discovery's front VRCS thrusters, I can find no other close up images of the system. Specifically, I can find no information on the rear thrusters.

enter image description here

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  • $\begingroup$ the rear thrusters are the white rectangular bits sticking out of the OMS pods $\endgroup$
    – user20636
    Mar 11, 2019 at 11:19
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    $\begingroup$ More info $\endgroup$
    – user20636
    Mar 11, 2019 at 11:24
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    $\begingroup$ this looks like a good picture from pinterest $\endgroup$
    – user20636
    Mar 11, 2019 at 11:35
  • $\begingroup$ @JCRM: On the FlightGear wiki of all places?!? Thank you! I do not have a pinterest account but I could see a few of the photos on that page before the popups start. $\endgroup$
    – dotancohen
    Mar 11, 2019 at 11:41
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    $\begingroup$ Regarding the (truly beautiful) picture, that's not just the VRCS thrusters, but mostly the primary forward RCS thrusters. Only one of the VRCS thrusters is visible as the tiny hole just forward of the two big down-firing RCS jets, which nicely shows the size difference. $\endgroup$
    – TooTea
    May 15, 2020 at 7:54

1 Answer 1

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Answer modified to discuss the entire Shuttle Reaction Control System not just the Vernier RCS

The shuttle RCS was divided into 6 VRCS jets and 38 Primary RCS jets. It was also divided into three pods - left aft, right aft, and forward. Each pod had its own helium pressurization, fuel, and oxidizer tanks. The aft RCS pods could be connected to each other to share their propellant supplies. There was also a 6000 lbf Orbital Maneuvering System (OMS) engine in each aft pod with its own tanks. The plumbing for the OMS engines could be interconnected with either or both aft RCS pods. There was no interconnect with the forward pod. The plumbing is both interesting and complicated - see the references for details.

The VRCS jets burned nitrogen tetroxide and monomethyl hydrazine at a mixture ratio of 1:6 and a chamber pressure of 110 psi. The thrust was 24 lbf. The expansion ratio varied from 20:1 to 50:1 (the jets were cut off ("scarfed") to fit the outer mold line of the vehicle). The maximum continuous on time was 125 seconds, the minimum was 80 milliseconds.

There weren't any up-, forward- or aft- firing verniers, only left, right, and down.

On these following diagrams, the verniers are always in manifold 5 so their names are X5Y where X=pod Y=direction.

The Primary jets burned the same fuel and produced 870 lbf at 152 psia chamber pressure and the same mixture ratio. Their expansion ratios varied from 22:1 to 30:1. They had the same time constraints but allowed for a contingency deorbit burn of 500 seconds for the aft jets.

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All info from the 1982 Press Manual

You can get some awesome pictures of the aft of the shuttle including the jets from the inspection photos taken from ISS, like this one.

enter image description here (source)

Besides the Press Manual, there is a lot of great information in the Shuttle Crew Operations Manual section 2.22 about the RCS.

For information about using the RCS to maneuver the vehicle, see this question: How fast can the space shuttle change its attitude in space?

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  • $\begingroup$ Thank you! Would the entire RCS be the VRCS + the AJ-10s? Where is the line between the VRCS and the RCS as a whole? In fact I would be interested in the entire RCS if you have inclination to share. I started researching RCS and found reference to VRSC for the shuttle, so I thought that VRCS is how the shuttle RCS is called. Other than the AJ-10s, they all seem to be vernier (small, precise) thrusters. $\endgroup$
    – dotancohen
    Mar 11, 2019 at 13:07
  • $\begingroup$ I'll mod the answer, but the Primary RCS jets are much larger. The AJ-10s are considered a separate system with their own tanks, etc - the Orbital Manuevering System. There is great info about that in the references I link as well. $\endgroup$
    – Organic Marble
    Mar 11, 2019 at 13:09
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    $\begingroup$ Thank you. I have my evening, and bedtime story for the kids, cut out for me today! Your answers are always appreciated. $\endgroup$
    – dotancohen
    Mar 11, 2019 at 13:11

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