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SpaceX Starship SN4 is almost ready for its turn on the test stand

Work on the latest iteration of Elon Musk's Mars rocket is progressing rapidly despite some setbacks.

While many businesses in Texas are shuttered due to the COVID-19 pandemic, SpaceX has been busy assembling the latest Starship prototype at its Boca Chica development facility. The early version of Elon Musk's Mars rocket has the serial number SN4, and he shared a photo of it standing tall on the test stand Thursday.

SN4 came together quickly over the last few weeks after a previous version collapsed during a pressure test earlier this month. 

A webcam set up by a nearby resident captured the above time-lapse video of the Starship prototype SN4 getting stacked inside the company's on-site vehicle assembly building. NASASpaceflight.com reports that bulkheads for another unit, SN5, are also being built at the facility. 

This has been the company's operating mode during Starship's development -- to rapidly assemble two prototypes at the time to be able to quickly pivot to a new unit if one fails. So far, both SN1 and SN3 have failed during pressure tests, while SN2 passed.

SpaceX CEO and founder Elon Musk has said that this series of prototypes will be capable of flying to an altitude of around 12.4 miles (20 kilometers) and landing back on Earth. It's likely we'll see one of the SN series of prototypes do a shorter "hop" before that.

It's not clear when we might see any of the Starship prototypes leave the ground, but Musk should soon have a quiver of three of the rockets to work with, which will surely help.