SpaceX CEO Elon Musk explained the recent failure of a full-scale Starship prototype failure during an early test, and later unveiled the rocket engines due to power a future prototype's first flight, reports Teslarati.
Elon Musk's SpaceX loses a Starship prototype
Days ago on April 3 SpaceX began the third full-scale cryogenic (ultra-cold) pressure test of the Starship prototype. The first step was to load the roughly 30-meter (100-foot) tall rocket's upper propellant tank with what was probably more than 400 metric tons (roughly 900,000 lbs) of liquid nitrogen. For hours, liquid nitrogen — a neutral chemical designed to simulate propellant — was loaded and offloaded repeatedly.
Then, at roughly 2:07 AM local time, the liquid oxygen tank underneath the methane tank suddenly crumpled, similar to the way plastic bottles with some air sucked out. After a few agonizing seconds of unstoppable crumpling, gravity took its course and pulled the heavy upper tank to the ground, which shredded the remaining thin steel skin of the rocket.
At first blush this is embarrassing, but — from an engineering perspective — this is actually a positive (albeit unfortunate) development because, as Musk confirmed and some suspected from the video, the malfunction was possibly due to a bad test design and operator error(s) — not a technical fault intrinsic to Starship SN3's rocket itself.
This is significant because it means that — unless future operators have error-prone days — Starship SN3's second cryogenic test went smoothly, and there will be no delays to Starship SN4's ongoing assembly, reports Teslarati.
In light of Musk's statement that a bad test design coupled with operator error caused Starship SN3's failure, the ship's performance on April 3 was technically impressive, according to Teslarati. This is because it remained standing for several seconds after its aft tank crumpled and likely lost pressure.
Raptor Rockets for SpaceX's next-gen rockets
If this is hard to visualize, imagine a crushed steel can holding the weight of a Boeing 747 passenger jet. With that in mind, one could say this is an extremely robust rocket.
Pretty much. Good news is that this was a test configuration error, rather than a design or build mistake. Not enough pressure in the LOX tank ullage to maintain stability with a heavy load in the CH4 tank. This was done with N2.— Elon Musk (@elonmusk) April 5, 2020
In his tweet, Musk said the rocket failed because the lower (liquid oxygen) tank wasn't pressurized enough to support the weight of a liquid-nitrogen-loaded methane tank above it. According to Teslarati, his description suggests one or several people may have not accounted for the fact that liquid nitrogen is almost 25% heavier than the cryogenic methane it was supposed to simulate.
While a prototype probably valued at several million dollars plus a month of SpaceX labor was lost, this means the company can move forward with its SN4 without delay — so long as the operator mistake is corrected.
Raptors pic.twitter.com/oycjgNI8HE— Elon Musk (@elonmusk) April 5, 2020
As a move perhaps for transparency, Musk — probably burning the midnight oil at SpaceX's Boca Chica, Texas Starship facility — later posted a photo in a tweet that shows three operational Raptor engines in one frame, and it's a rare sight.