BROWNSVILLE — While everybody has been preoccupied with coronavirus the past several weeks, SpaceX’s Boca Chica operation has been aggressively pursuing development of the Starship spacecraft intended to take humans to the Moon and Mars.

But there’s still a lot of work to be done to get there. Elon Musk, the company’s founder and CEO, tweeted on April 17: “Good progress, but 18 years to launch our first humans is a long time. Technology must advance faster or there will be no city on the red planet in our lifetime.”

Boca Chica has become the locus of the company’s Starship accelerated build/test program, which has experienced failures as well as successes over the past several months. Starship Mk1, the earliest full-size prototype, was irreparably damaged in November during a cryogenic fuel pressurization test. The next prototype, SN1, met a similar fate on Feb. 28, dashing plans for a sub-orbital test flight this spring, though SpaceX’s Boca Chica team was already building SN2.

SN2 aced a series of pressurization tests on March 8 and was retired to make way for testing of SN3, which ruptured and collapsed during testing on April 2. Musk at the time suspected a “test configuration mistake,” and on April 5 confirmed it, tweeting that the “good news is that this was a test configuration error, rather than a design or build mistake.”

The cryogenic pressure tests are needed to prove Starship is able to withstand exceptionally high pressure caused by very cold fuel, which is an issue in space. A successful cryogenic pressure test likely would have been followed by a static-fire engine test and a hop. The Boca Chica team was already at work on SN4, which has been transported from the yard to a test stand at the launch pad and awaits testing. Musk posted an aerial shot of SN4’s stainless-steel-clad “tank” atop the test stand on April 23.

SpaceX is gearing up for tests soon. Cameron County ordered the closure of Boca Chica Beach and S.H. 4 from FM 1419 to the beach from 9 p.m. Saturday to 6 a.m. Sunday for “test launch activities.” The alternate closure date is April 26 and/or April 27 from 9 p.m. to 6 a.m. the following day.

The county has also announced closures of the beach and the highway for April 29 from 9 p.m. to 6 a.m. the following day, with alternative dates of April 30 and/or May 1 from 9 p.m. to the following day. The Federal Aviation Administration has issued Temporary Flight Restrictions up to 1,500 feet around the Boca Chica site covering the same dates.