The San Jose Mercury News article Looking like a seagoing Dr. Octopus, SpaceX’s Mr. Steven has added four longer, articulated arms talks about recent modifications to the size of the net on SpaceX's ship Mr. Steven.

Studying Mr. Steven more carefully, I see two sets of markings I don't recognize. The first is what looks like three 4-blade propellors, and the second has a series of horizontal lines and a horse-shoe type shape with antlers.

What do these mean? Are they related in any way to Mr. Stevens' job of catching fairings from the sky?

Full size image can be found at https://www.mercurynews.com/wp-content/uploads/2018/07/0524_nws_tdb-l-mrsteven-05247.jpg

Mr. Steven Markings 1 Mr. Steven Markings 2

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  • $\begingroup$ The markings look like 4-blade propellors because they should indicate where additional propellors are mounted. These propellors are used to move the ship to the side and not straight ahead or back. $\endgroup$
    – Uwe
    Commented Jul 14, 2018 at 12:09

1 Answer 1


The one that looks somewhat like a ladder or staircase is a "load line" or "Plimsoll line" marking. Each line marks how deeply the vessel can be safely loaded under various conditions: winter (W), summer (S), tropical (T), freshwater (F) etc. The circle and line is the primary summer load line for where the vessel was surveyed; any letters on it indicate who did the survey.

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The symbols that look like Maltese crosses mark the location of thrusters, so that lines et al can be kept clear.

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Those are all standard markings for a sea-going ship, not directly related to it's job of catching fairings.

  • 2
    $\begingroup$ Thanks for the speedy and yet thorough answer! I thought those crosses might have been the equivalent of "kill tallies" - maybe they'd run aground three times and wrecked three propellors. I wonder if we will start seeing a tally of fairing-halves once they start catching them regularly! ;-) $\endgroup$
    – uhoh
    Commented Jul 14, 2018 at 7:06
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    $\begingroup$ Never expected getting such in-depth naval knowledge from Space.SE :) $\endgroup$
    – SF.
    Commented Jul 14, 2018 at 8:35
  • 4
    $\begingroup$ @SF. And all I ask is a tall ship and a star to steer her by; 1, 2 Teleplay by Dorothy Catherine Fontana, poem by John Masefield. $\endgroup$
    – uhoh
    Commented Jul 14, 2018 at 9:19
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    $\begingroup$ Kinda like RCS. $\endgroup$
    – SF.
    Commented Jul 14, 2018 at 18:42
  • 1
    $\begingroup$ Mr Steven has two diesel engines and dual props, plus three transverse thrusters at the front. She can pivot pretty well, but unlike an RCS can't move sideways with any significant speed. It looks like the track to catch (or practice catching) a fairing is a long, straight run at 9-12 knots: marinetraffic.com/en/ais/home/centerx:-118.374/centery:33.732/… which makes sense if trying to catch something descending under a square parachute. $\endgroup$ Commented Jul 15, 2018 at 0:30

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