Rocket Lab Corporation (RKLB) is having one of those good news, bad news days. The space launch company kicked off 2026 with a successful mission, but shares tumbled on Thursday following disclosure of a testing setback with its next-generation Neutron rocket.

Mission Success Amid Development Challenges

The good news first: Rocket Lab completed its first launch of 2026 and its 80th Electron mission overall. The mission, colorfully dubbed The Cosmos Will See You Now, lifted off from Rocket Lab Launch Complex 1 in Mahia, New Zealand, at 11:52 pm NZDT (10:52 UTC).

The launch deployed two satellites into a 1,050 km circular orbit for Open Cosmos, marking the first time Rocket Lab dedicated a full mission to the pan-European space tech firm. Open Cosmos specializes in complete satellite solutions, handling everything from design and manufacturing to in-orbit operations.

The high-altitude mission showcased Electron's flexible payload capabilities, reinforcing its reputation as a reliable and versatile launch vehicle for small satellites. Rocket Lab's 2026 schedule is packed with Electron launches for both new and returning customers from its Virginia and New Zealand sites, with the next mission scheduled to lift off soon from Launch Complex 1.

Neutron Testing Hits a Snag

Now the not-so-good news: Rocket Lab shares dropped about 5% late Wednesday after the company revealed that a Stage 1 tank ruptured during overnight hydrostatic testing of its Neutron rocket. Hydrostatic testing involves pressurizing tanks to verify they can handle the stresses of flight.

The company emphasized that no significant damage occurred to the test structure or facilities. Production of the next Stage 1 tank is already underway, and Neutron's development campaign continues while engineers analyze the test data to understand what went wrong.

RKLB Price Action: Rocket Lab shares were down 4.35% at $84.00 at the time of publication on Thursday.