New Zealand space launch is first from a private site

I've done space projects with US companies and so am fully marinated in ITAR processes. In answer to your question: No, you can get around ITAR by just being careful about what information is imported and exported to and from the US. If there was a US engineering office and an NZ engineering office and all the engineering effort was evenly distributed among the two, it would be a nightmare as you'd be 'exporting US technology' constantly, but if all the important stuff is being done in NZ and very little know-how has to go back-and forth across the virtual border with the US then it's more manageable (still involves lawyers and experts though). It doesn't matter than the US owns it financially, it's the transfer of knowledge and stuff across the border (virtual and real) that is the hard bit. As this is basically a NZ company which had to do a paperwork fudge in order to accept US investment, ITAR is not such a problem.

Turns out I was mistaken. If you look at their careers website (https://rocketlabusa.com/careers/positions/) it seems as though the engines are being designed and/or built in California and the rocket and software is being done in NZ.

"rarely done"? Has it ever been done??

Searching for "polar launch" found nothing. (There's actually a Polar Satellite Launch Vehicle [1], but it does not launch from the poles [see Launch History at 1])

[1] https://en.wikipedia.org/wiki/Polar_Satellite_Launch_Vehicle

This is correct, the power density of electric motors (and the batteries to power them) is still very far short of what you can get from a well-designed turbine-based pump (that is, a turbopump), but there's so much ancillary plumbing and and stuff for a turbopump (like the precombustion chamber that has to generate some hot gas to drive the turbine), that doesn't scale down all that well to the small scale of the engines on the Electron, that the power density advantages of a turbopump tend to asymptotically tail off. Also, they require a lot of expertise to design, compared to almost any other kind of pump. There are turbopumps and turbopumps, though, and here I will paste in an HN comment of mine from a number of years ago:

""" There are three kinds of rocket engine cycle (well, there are maybe more but these are the three that have been flown historically). The Expander Cycle, the Staged Combustion Cycle, and the Gas Generator cycle. I'll mention the last two.

Merlin, as the article mentions, is an example of a Gas Generator cycle. In this cycle, you take off a little bit of fuel and oxidiser to burn outside the main combustion chamber, to generate some hot energetic gases that you can exhaust over a turbine. This spins the turbine up, which is connected to a shaft with a compressor on the other end. The compressor increases the pressure of the propellents so that they can be injected into the main combustion chamber. This assembly (turbine, shaft, compressor) is called the turbopump. It's necessary because the engines require very high flow rates to get the thrust they need, and that has to be at a high pressure - higher than the pressure of the combusting gases inside the combustion chamber, else you wouldn't be able to inject it!

Back to the bleed-off to drive the turbine. You usually don't want a perfect stoichiometric mix of fuel and oxidiser for this, or even close, because it generates extraordinary hot gases that no turbine would last long in (The turbines are spinning at many tens of thousands of RPM usually so would be subject to much higher forces than the actively cooled walls of the main combustion chamber). For this reason you usually have a large imbalance of one propellent to the other to keep the temperature down. Usually you run with excess fuel, or 'fuel-rich', as the opposite - oxidiser rich - means you have hot oxidising gases which are harder on the metallurgy. I do know of some russian exceptions to this, though, where fuel rich would have left sooty deposits in the plumbing (The materials science employed in the turbines was apparently so witchcraft that when the US got intelligence of oxidiser-rich turbine precombustors, they thought is was deliberate counterintelligence from the russians to get them to waste billions researching the impossible). The gas generator cycle, as the article mentions, dumps this turbine exhaust overboard separately. The problem with this is that there's a load of uncombusted fuel in this exhaust, which you're just wasting, and this hits your rocket performance - the Specific Impulse ( I_{sp} ), as you're not getting as much bang out of a given mass of fuel as you could.

The answer to this is the Staged Combustion Cycle, where you also inject the exhaust of the turbine into the combustion chamber to finish off combustion. The performance of these engines is higher but the thermodynamic balance to design a working system is a greater challenge, and some of the engineering is a bit harder too. Staged Combustion engines are mostly russian, although the Space Shuttle Main Engines are a US-design example of Staged combustion. """

Staged combustion engines are extremely efficient and on a big engine no electric pump system will even touch them, unless there is some materials-science breakthrough that will allow us one or two orders of magnitude improvement in flex density in electromagnetic materials. Electric pumps will probably remain in their niche for small engines and satellites.

I do think that small turbopumps are worth further research, although I don't know if the market needs higher performance small engines over more cheaper-to-produce small engines, but certainly there was fascinating work done in the uk in the 70s with tiny turbopumps (about the size of a coke can) that ran at hundreds of thousands of rpm, with a power of megawatts, and compressors very cleverly shaped to run sustainably far beyond the cavitation point of the fluids, which is usually the point at which you can't pump anymore, in traditional pump design literature. In combination with an expander cycle you could probably produce some extremely high performance, simple, small rocket engines. Maybe.

We live in exciting times.

I read a paper some people wrote on the subject. Take away is battery powered pumps can be built as big, or importantly as small as you want. Turbo pumps on the other hand don't scale down well very well. Batteries win at the size of the electron rocket.

I would not be surprised if someone starts work on a larger electric rocket engine because the difference in efficiency is not huge. But however electric is a far simpler and potentially more reliable design. If electrics are super reliable the difference in insurance costs might tip things in their favor[1].

[1] Trade 1:10 chance of losing your sat vs a 1:50 chance for 25% higher launch costs? There are companies that would readily take the latter option.

I remember reading about a plan to use an actual V12 vehicle engine to power turbopumps at one point - supposedly simpler and more reliable than trying to drive it from another turbine. Can't find it on the internet now.

When they first announced the design I know a lot of people in the industry were skeptical that it would work at all.

You can always do that stuff later. Changing the world has always been for those willing to sacrifice.

Just need a few SF people to chip in a week's rent :-)