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The NASA Spaceflight article Rocket Lab’s Electron rocket set for inaugural flight from New Zealand mentions the upcoming opening of a 10 day launch window:

Rocket Lab, a U.S.-based launch service provider with a New Zealand subsidiary, will become the newest entrant into the world’s launch market with the maiden voyage of its Electron rocket.

The 10-day launch window for Electron’s maiden flight opens at 09:00 NZDT (New Zealand Daylight Time) on Monday, 22 May.

The time offset for New Zealand is UTC+12, placing the opening of the launch window at 21:00 UTC on Sunday, 21 May (which is 17:00 EDT on the eastern seaboard of the United States on Sunday afternoon).

Overall, Rocket Lab’s mission is to offer “lightweight, cost-effective commercial rocket launch services” to the small satellite market.

I noticed that each of the eight engines in the outer ring seems to have two large cylinders attached at the bottom ends to the bottom of the combustion chambers, and the tops to the rocket frame. Initially I'd hoped I'd finally sighted shock absorbers - they look like compressed-gas cylinders, but considering how they are mounted that's not really likely.

Since they are mounted at roughly right angles with respect to each engine's axis, I wonder if they could be vectoring actuators, but wouldn't these large cylinders be an unusual method for vectoring engines?

One interesting point about the Electron - since the fuel and oxidizer pumps are 50 hp electric motors, there is plenty of electric power available - according to Wikipedia the Lithium battery can provide up to 1 MW of electric power.

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above x2: Illustrations of the nine Rutherford engines on Rocket Lab's Electron rocket. From here.

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uhoh
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  • Looks quite similar to SpaceX Merlin 1D gimbal actuators. A bit bigger relative to this engine but that would make sense if this engine is smaller. – jkavalik May 21 '17 at 13:43
  • @jkavalik if you can put a pic and a few sentences together with an explanation of roughly what the cylinders are and how they work (in either case would be fine), that could be a nice answer! Somehow I thought there were motors and gears pointing the Merlins. – uhoh May 21 '17 at 13:45
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    http://www.spacex.com/sites/spacex/files/100th_m1d_4_engine28.jpg this is m-vac version. One of the cylinders can be seen clearly. You might remember some TVC issues (2nd stage) delaying a couple of launches. – jkavalik May 21 '17 at 13:48
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    Definitely gimbal actuators, whether hydraulic or electrical. – Russell Borogove May 21 '17 at 13:56
  • @jkavalik the small size of the hydraulic(?) cylinders compared to the huge combustion chambers in your excellent image contrasts with the relative sizes in the illustrations in the question. The configuration is similar, but because of the big difference in the ratio of cylinder to chamber diameters, I wonder if there is something different going on here? I'd expect smaller chamber = smaller thrust = smaller required cyinder. – uhoh May 21 '17 at 14:01
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    Would electric actuators need these? (from http://idarts.co.jp/3dp/wp-content/uploads/2016/03/Rocket-Lab-Electron-4.jpg) – jkavalik May 21 '17 at 15:48
  • @jkavalik aren't those binding posts? (humor) https://i.stack.imgur.com/nAmHI.jpg You have a good point. While they could be gas lines for motor cooling or back-up pressure if the motors fail, they could be gas lines for pneumatic actuation (though that's hard to imagine) or possibly they could look like an artists impression of a hydraulic connection. They look like black, plastic gas line connectors, but this is just a drawn illustration, and not even intended to be a photorealistic one. I think we need something better to draw conclusions. – uhoh May 21 '17 at 16:48

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The blue cylinders contain electric motors that are used to vector the engine assembly. This could be either a linear motor or a conventional motor driving e.g. a thread screw.

The pumps and the thrust vector actuators on the engine have brushless DC motors powered by batteries.

This means they can avoid hydraulics, simplifying the design.

In this 2018 photo you can see the configuration has been changed a bit from the rendering:

enter image description here

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