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.

enter image description here

enter image description here

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

  • $\begingroup$ 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. $\endgroup$
    – jkavalik
    Commented May 21, 2017 at 13:43
  • $\begingroup$ @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. $\endgroup$
    – uhoh
    Commented May 21, 2017 at 13:45
  • 1
    $\begingroup$ 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. $\endgroup$
    – jkavalik
    Commented May 21, 2017 at 13:48
  • 2
    $\begingroup$ Definitely gimbal actuators, whether hydraulic or electrical. $\endgroup$ Commented May 21, 2017 at 13:56
  • 1
    $\begingroup$ Would electric actuators need these? (from idarts.co.jp/3dp/wp-content/uploads/2016/03/…) $\endgroup$
    – jkavalik
    Commented May 21, 2017 at 15:48

1 Answer 1


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

  • 3
    $\begingroup$ For 1-2 minutes of intermittent operation, I'd be surprised if you needed water cooling. Those look like cable glands to me. $\endgroup$
    – Hobbes
    Commented May 22, 2017 at 14:41
  • 1
    $\begingroup$ The permanent magnets loose their oomph if they get too warm, but if they're not really thermally coupled to the copper, then there's just the rise in copper resistance which in this particular case is not a big deal (unless it eventually becomes one). Ya three minutes, not much chance of it going too much longer than that under any possible scenario, I see what you mean. $\endgroup$
    – uhoh
    Commented May 22, 2017 at 14:45
  • $\begingroup$ I've just asked this follow-up question; What kind of forces and response times are needed to gimbal a mid-sized nine-engine rocket's engines? $\endgroup$
    – uhoh
    Commented May 22, 2017 at 15:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.