Paying customers have come on board for Rocket Lab's second test launch, just months after its successful inaugural test.

A launch date is yet to be announced but preparations are underway at the launch pad at New Zealand’s Mahia Peninsula.

Founder Peter Beck says the rocket is performing well through rigorous acceptance tests and the team is focused on final flight preparations.

"It's our second test flight, and we're just privileged to also have some commercial customers on board. That's very, very unusual for this industry, and it really showcases confidence in the company and the vehicle that our customers have to fly so early

The flight will be carrying a payload from Planet and a couple from Spire.

"Planet is an Earth-observation payload. It provides images of the planet mainly used for things like crop monitoring and deforestation, and Spire is a weather satellite, so used for weather prediction and weather monitoring," Beck explained.