Just days after Starship SN11 conducted a fog-cloaked test flight that ended in an explosive finale, SN15 is already in final preparations for a rollout down Highway 4 at SpaceX Starbase (Boca Chica). SN15 will sport numerous modifications that SpaceX hopes will result in improved performance ahead of shooting for orbit along with smoother touchdowns for its prototype rocket.
One of the mostly unspecified modifications involves the engines, which are being aided by an increased test cadence at SpaceX’s McGregor test site. The center is currently constructing two additional vertical Raptor test stands to increase throughput.
SpaceX Starbase:
SN11 was the most dramatic ending to a Starship prototype flight to date, albeit without any cameras catching the explosion due to thick fog in the region.
When SpaceX’s onboard feed froze, SN11 was moving toward the flip and landing burn of its three Raptors. NASASpaceflight.com’s Livestream audio caught the sound engine relight, quickly followed by the explosive boom and pieces of SN11 raining down on the launch site.
Every other stage of flight, including the ascent and the bellyflop return, matched the successes of SN8 through SN10. While it was later noted that one engine struggled during the ascent, the vehicle achieved its test objectives heading toward the landing burn.
While online rumors have ranged from issues relating to the Flight Termination System’s triggering (FTS) through to the CH4 (Liquid Methane) Header Tank exploding, it is understood the likely cause was an explosive engine failure during the re-light process that destroyed the vehicle.
Nothing can be confirmed until Elon Musk or SpaceX release the official cause of the vehicle returning to the launch site in pieces, conclusions that are expected per Elon’s surprising and refreshing transparency with the test program.
SpaceX workers have been spending the days following the test to clean up a large debris field, hardware that will aid any outstanding conclusions into the failure in tandem with telemetry data.
“Looks like engine 2 had issues on ascent & didn’t reach operating chamber pressure during landing burn, but, in theory, it wasn’t needed,” Elon Musk noted just hours after the failure. “Something significant happened shortly after landing burn start. Should know what it was once we can examine the bits. Will report conclusions as soon as we know them.
Scenes from the crash site. SpaceX crews are working hard to remove a prodigious amount of Starship SN11 bits from the area surrounding the launch site. @NASASpaceflight pic.twitter.com/oGEQW6JpkY
— Jack Beyer (@thejackbeyer) March 31, 2021
Undeterred, the loss of SN11 has not impacted the plan to push on to SN15’s test series.
Starship SN15 is the next phase of prototype testing thanks in part to the successes with SN8 onwards – resulting in the scrapping of SN12, 13, and 14. This progression may also provide automatic mitigation of SN11’s issue.
“It (SN15) has hundreds of design improvements across structures, avionics/software & engine,” Elon added. “Hopefully, one of those improvements covers this problem. If not, then retrofit will add a few more days.”
SN15 rolled from the Mid Bay to the High Bay during the week, ahead of receiving its Nosecone, which has since been mated to the stack. It will make the trip down Highway 4 as early as Monday, once the impressive Liebherr LR1600/2 Crawler Crane (dubbed “Tankzilla”) has made the trip for the task of raising SN15 on the launch mount.
This vehicle marks the second phase of testing for the full-stack Starship prototypes ahead of pushing on to the orbital vehicles, which is expected to open with the SN20 vehicle – as previously reported by NASASpaceFlight.com.
“Next major technology rev is at SN20. Those ships will be orbit-capable with heat shield & stage separation system. Ascent success probability is high. However, SN20+ vehicles will probably need many flight attempts to survive Mach 25 entry heating & land intact.”
Starship SN20 begins life with the leg skirt section spotted by Mary (@bocachicagal)
Although Elon confirmed the orbital attempt would be as reported, with SN20 and Super Heavy BN3, the claimed target date of “by July” was always highly ambitious. The likelihood BN3 will be the Super Heavy to conduct the flight is also subject to change.
This ever-evolving plan was confirmed when Elon noted BN1 won’t even undergo testing at the suborbital site and will be scrapped.
Currently stacked in the High Bay, BN1 was never going to hop. However, it was expected to be proof tested – and at one point was potentially Static Fired with a couple of Raptors. While SpaceX may take the opportunity to test how to roll such a tall booster down Highway 4, it appears likely the pathfinder will likely be scrapped at the Production Site.
Booster BN1 watches as Starship SN15 receives an aft flap. 🤩🚀@NASASpaceflight pic.twitter.com/Pl0RQpUoXP
— Mary (@BocaChicaGal) March 31, 2021
“BN1 is a manufacturing pathfinder, so will be scrapped. We learned a lot, but have already changed design to BN2,” Elon noted, with the design change likely to be related to the position of the LOX and CH4 tanks in the stack.
Amazingly, Elon added that SpaceX aims to complete the stacking of the BN2 Super Heavy booster – which is currently in sections outside the High Bay, in time to rollout and lifted on to the yet-to-be-completed Orbital Launch Site mount in a matter of weeks.
“Goal is to get BN2 with engines on orbital pad before end of April. It might even be orbit-capable if we are lucky,” Elon added, with “orbit-capable” a highly surprising statement given his initial note about the first test of a Super Heavy originally being a 150-meter hop.
However, whenever there is doubt in ambitious Starship schedule goals, the Production Site is on hand to add some realism via its incredible cadence. Even BN3 sections have already been spotted by Mary (@bocachicagal).
A huge amount of work is continuing at the Orbital Launch Site, ranging from the addition of GSE (Ground Support Equipment) and commodity tanks through to the initial phase of constructing the Integration Tower that will become the tallest structure in the region when completed.
While the plan for BN1 was to utilize one of the two suborbital mounts, the goal of placing BN2 on a mount that has yet to be completed will task engineers with installing the launch table and other associated hardware over the coming weeks amid SN15’s test campaign.
However, SpaceX is not averse to testing vehicles while still constructing the facilities designed to host them during their operational phase.
SpaceX McGregor:
SpaceX’s Rocket Development and Test Facility has been an integral part of its success since it acquired the facility in 2003.
Every new engine built at SpaceX’s factory in California passes through McGregor ahead of being sent to the launch site as a unit or as part of a rocket stage.
The facility has grown in size during its SpaceX tenure, with the addition of numerous test stands, including the conversion of the original stalwart Falcon 9 tripod stand, which now hosts vertical Raptor testing.
Raptor engines are also tested in two horizontal bays, with long duration testing now into the SN60 range, the engines with the cited improvements. The second Raptor Vac (RVac) was also spotted on the horizontal stand last week via NSF’s Gary Blair in the L2 McGregor section, a local who flies past the test site at around 3,000 feet AGL.
RVac and Sea Level Raptors on the test stand via Gary Blair for NSF/L2 from his plane
The Raptor Vacuum (RVac), with its huge nozzle, will be the engine that will provide the bulk of Starship’s propulsive power in space.
So far, testing this engine has been progressing, with Elon recently noting, “Going well. Lot of work for an extra 20 secs of Isp!”
Elon had previously cited the advantage of vertical testing for Raptors as one reason the Tripod was converted to hosting the Starship engine. “Testing Raptor in vertical configuration (on the giant tripod) should allow us to simplify some aspects of the engine design.”
Soon, McGregor will have two additional vertical test stands for Raptor, with the construction of a new stand ongoing at the Texas site.
New Raptor Test Stand via Gary Blair for NSF/L2 from his plane
The new Raptor stand has an underground diverter, and each of the vertical test bays will be available for testing both sea-level and vacuum-optimized Raptors.
Importantly, it will also cater to the future demand for Raptor engines, which will exponentially increase during the early phase of Super Heavy testing.
Super Heavy will eventually sport 28 Raptor engines. While the goal will be to return all the engines on the fully reusable launch system, SpaceX will be prepared to ensure Raptor availability is in tune with the potential loss of engines during the early phase of full-stack test flights.
This article will be updated during the test week for SN15. For live updates, follow NASASpaceFlight’s Twitter account and the NSF Starship Forum Sections.
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