SpaceX has finished stacking its fourth full-scale Starship prototype and public schedules show that the rocket could be moved to a nearby launch and test pad as early as April 20th.

Known as Starship serial number 4 (SN4), the rocket will be the third full-scale vehicle completed since the start of serial production, while Starship Mk1 – the first full-scale prototype – was built far more slowly and with different methods. Mk1 was destroyed during one of its first cryogenic liquid nitrogen ‘proof’ tests in November 2019, nearly nine months after assembly began in February. After Mk1’s failure, SpaceX spent about two months rapidly expanding and upgrading its Boca Chica, Texas Starship factory.

Around the end of January 2020, SpaceX kicked off the production of its first serial prototype – logically deemed SN1. Less than a month after its first steel rings were stacked and welded together, SpaceX transported the completed prototype to the launch pad. On February 28th, what CEO Elon Musk later described as a fault in its engine section “thrust puck” destroyed Starship SN1 during one of its first cryogenic proof tests. Barely a month later and after SN2 was modified into a “thrust puck” test tank and successfully tested, Starship SN3 rolled to the launch pad and was destroyed by operator and test design errors on April 3rd. Now, barely two weeks after SN3, Starship SN4 is about to begin testing.

There she is! SN4 tanks section is fully stacked🚀It should be ready to roll to the pad in about 3 days

📸 by @BocaChicaGal and @nomadd13 for @NASASpaceflight https://t.co/5qC0eR4RpF pic.twitter.com/FZLfoQlsKs — Rafael Adamy (@fael097) April 17, 2020

SpaceX finished stacking its fourth full-scale Starship prototype on April 17th. (NASASpaceflight – bocachicagal)

By all appearances, work on Starship SN4 began around March 23rd, continuing a production schedule that has been consistently completing a full-scale rocket prototype every four or so weeks. While SpaceX has taken the unprecedented step of reusing a section of a prototype (SN3) destroyed during testing, every other aspect of the rocket is new and built more or less from scratch.

Starship SN3’s skirt – including internal plumbing, landing legs, and more – was removed from the rest of the ship’s remains and moved back to the build site on April 7th. (NASASpaceflight – bocachicagal)

SpaceX stacked Starship SN4’s new engine section and SN3’s salvaged skirt and landing legs around April 15th. (NASASpaceflight – bocachicagal)

Just two days after Starship SN3’s salvaged skirt and SN4’s new engine section and aft liquid oxygen tank dome were stacked and welded together, SpaceX technicians attached a crane to the upper two-thirds of the rocket’s tank section and stacked it on top of the newly-finished engine section. 24 hours later, SpaceX teams have completed at least one circumferential seam weld, with a second soon to be finished.

Once that last weld is complete and passes inspections, Starship SN4 will be ready to be lifted onto a transporter and rolled down the road to SpaceX’s dedicated launch and test facilities. Of course, like SN3 and SN1 before it, SpaceX will likely still have a few days of work to get Starship SN4 ready for testing once it’s been moved to the pad.

Starship SN3 was fully stacked on March 26th and was transported to the launch pad on March 28th, while pad testing began on April 2nd. (Elon Musk)

Starship SN4 was fully stacked on April 17th. (NASASpaceflight – bocachicagal)

Using Starship SN3’s timeline, Starship SN4 could be transported to the pad as early as April 19th or 20th and ready for testing by April 24th or 25th. This meshes well with a publicly-available road closure schedule, required because SpaceX often needs to close a public highway for certain Starship transport and testing operations. Per Cameron County’s website, SpaceX has a transport-related closure planned on April 20th. The first testing-related closure begins on Sunday, April 26th and lasts from 9am to midnight, with backups on Monday and Tuesday.

As always, delays should come as no surprise with prototype testing, and schedules are always fluid and liable to change at any second. Regardless, it looks like Starship SN4 is perhaps just a week from its first round of testing.