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SpaceX says Crew Dragon capsule exploded due to exotic titanium fire

Crew Dragon tests its SuperDraco-powered launch abort system in 2015. (SpaceX)

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SpaceX has announced via an official update and conference call the preliminary results of a failure investigation convened immediately after Crew Dragon capsule C201 exploded in the midst of an April 20th static fire test.

Hosted by SpaceX Vice President of Mission Assurance Hans Koenigsmann and NASA Commercial Crew Program manager Kathy Lueders, the call provided some minor additional insight beyond a fairly extensive press release issued just prior. According to the preliminary results from SpaceX’s failure investigation, Crew Dragon’s explosion was unrelated to the spacecraft’s propellant tanks, Draco maneuvering thrusters, or SuperDraco abort engines. Rather, the cause lies in a more exotic and unanticipated chemical/material interaction between a plumbing valve, liquid oxidizer, and a helium-based pressurization system.

When metal burns

According to Hans Koenigsmann, SpaceX is approximately 80% of the way through what is known as the fault tree, essentially meaning that the failure investigation is 80% complete. That additional 20% could certainly throw some curveballs but the SpaceX executive was fairly confident that the results presented on July 15th would be representative of the final conclusion.

The ultimate (likely) cause of Crew Dragon’s extremely energetic and destructive explosion centers around the spacecraft’s extensive SuperDraco/Draco plumbing and its associated pressurization system, which uses helium to keep the pressure-fed engines, propellant tanks, and feed lines around 2400 psi (16.5 megapascals). Necessarily, this method of pressurization means that there is direct contact between the pressurant (helium) and the oxidizer/fuel, thus requiring some sort of valve preventing the pressurized fluid from flowing into the pressurization system.

A detailed view of some of the Draco and SuperDraco-related plumbing used on Crew Dragon – in this case, the capsule that will now fly SpaceX’s In-Flight Abort test. (Pauline Acalin, August 2018)

During flight-proven Crew Dragon capsule C201’s April 20th static fire testing, that is reportedly exactly what happened. Over the course of ground testing, a “check valve” separating the pressurization system and oxidizer leaked what SpaceX described as a “slug” of nitrogen tetroxide oxidizer (NTO) into the helium pressurization lines. Around T-100 milliseconds to a planned ignition of the vehicle’s 8 SuperDraco abort engines, the pressurization system rapidly “initialized” (i.e. quickly pressurized the oxidizer and fuel to operational pressures, ~2400 psi).

To do this, helium is rapidly pushed through a check valve – designed with low-molecular-mass helium in mind – to physically pressurize the propellant systems. Unintentionally, the NTO that leaked ‘upstream’ through that valve effectively was taken along for the ride with the high-pressure burst of helium. In essence, picture that you crash your car, only to discover that your nice, fluffy airbag has accidentally been replaced with a bag of sand, and you might be able to visualize the unintended forces Dragon’s check valve (the metaphorical airbag) was subjected to when a “slug” of dense oxidizer was rammed into it at high speed.

Crew Dragon C201 displays its heat shield after the spacecraft’s first orbital-velocity Earth reentry, March 8th. (NASA/Cory Huston)

In itself, this sort of failure mode is not hugely surprising and SpaceX may have even been aware of some sort of check valve leak(s) and accepted what it believed to be a minor risk in order to continue the test and perhaps examine Dragon’s performance under suboptimal conditions. What SpaceX says it did not realize was just how energetic the reaction between the NTO and the check valve could be. SpaceX’s understanding is that the high-speed slug of dense NTO was traveling so fast and at such a high pressure that, by impacting the titanium check valve, it quite literally broke the valve and may have chemically ignited the metal, thus introducing a slug of burning NTO into the liberated NTO system itself – effectively a match tossed into a powder keg.

It’s unclear if the ignition came from a chemical reaction between titanium (a technically flammable metal similar to magnesium) and NTO, or if the source came from the titanium valve being smashed apart, perhaps quite literally creating a spark as metal debris violently interacted. Either way, the solution – as SpaceX perceives it – is the same: instead of a mechanical check valve (simple but still not 100% passive), the barrier between pressurant and oxidizer (as well as fuel, most likely) will be replaced with something known as a burst disk. According to Koenigsmann, only a handful (~4) of those valves exist and thus need to be replaced by burst disks, a relatively fast and easy fix.

Burst disks are single-use and inherently unreusable, but they are also completely passive and simply do not leak until subjected to a specific amount of pressure. Because they are single-use, they can’t be directly tested prior to flight, limiting some of the in-principle reliability for the sake of an extremely leak-proof barrier.

A test of one of Crew Dragon’s four ‘powerpacks’, featuring two SuperDracos and three Dracos. (SpaceX)

Ultimately, both Koenigsmann and Lueders went out of their way to avoid answering any questions about SpaceX’s Crew Dragon upcoming test and launch schedule and what sort of delays the explosion will ultimately incur. Both individuals were nevertheless upbeat and by the sound of it, delays to Crew Dragon will be far less severe relative to delays caused by a pressure vessel or engine failure. For the time being, NASA has published a tentative target of mid-November 2019 for Crew Dragon’s first crewed launch to the International Space Station, while Lueders and Koenigsmann expressed hope in a 2019 launch but refused to give a specific estimate of the odds of that occurring.

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Eric Ralph is Teslarati's senior spaceflight reporter and has been covering the industry in some capacity for almost half a decade, largely spurred in 2016 by a trip to Mexico to watch Elon Musk reveal SpaceX's plans for Mars in person. Aside from spreading interest and excitement about spaceflight far and wide, his primary goal is to cover humanity's ongoing efforts to expand beyond Earth to the Moon, Mars, and elsewhere.

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Tesla expands its branded ‘For Business’ Superchargers

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Credit: Francis Energy

Tesla has expanded its branded ‘For Business’ Supercharger program that it launched last year, as yet another company is using the platform to attract EV owners to its business and utilize a unique advertising opportunity.

Francis Energy of Oklahoma is launching four Superchargers in Norman, where the University of Oklahoma is located. The Superchargers, which are fitted with branding for Francis Energy, will officially open tomorrow.

It will not be the final Supercharger location that Francis Energy plans to open, the company confirmed to EVWire.

Back in early September, Tesla launched the new “Supercharger for Business” program in an effort to give businesses the ability to offer EV charging at custom rates. It would give their businesses visibility and would also cater to employees or customers.

“Purchase and install Superchargers at your business,” Tesla wrote on a page on its website for the new program. “Superchargers are compatible with all electric vehicles, bringing EV drivers to your business by offering convenient, reliable charging.”

The first site opened in Land O’ Lakes, Florida, which is Northeast of Tampa, as a company called Suncoast launched the Superchargers for local EV owners.

Tesla launches its new branded Supercharger for Business with first active station

The program also does a great job at expanding infrastructure for EV owners, which is something that needs to be done to encourage more people to purchase Teslas and other electric cars.

Francis Energy operates at least 14 EV charging locations in Oklahoma, spanning from Durant to Oklahoma City and nearly everywhere in between. Filings from the company, listed by Supercharge.info, show the company’s plans to convert some of them to Tesla Superchargers, potentially utilizing the new Supercharger for Business program to advertise.

Moving forward, more companies will likely utilize Tesla’s Supercharger for Business program as it presents major advantages in a variety of ways, especially with advertising and creating a place for EV drivers to gain range in their cars.

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Tesla Cybercab ‘breakdown’ image likely is not what it seems

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Credit: TslaChan | X

Tesla Cybercab is perhaps the most highly-anticipated project that the company plans to roll out this year, and as it is undergoing its testing phase in pre-production currently, there are some things to work through with it.

Over the weekend, an image of the Cybercab being loaded onto a tow truck started circulating on the internet, and people began to speculate as to what the issue could be.

The Cybercab can clearly be seen with a Police Officer and perhaps the tow truck driver by its side, being loaded onto, or even potentially unloaded from, the truck.

However, it seems unlikely it was being offloaded, as its operation would get it to this point for testing to begin with.

It appears, at first glance, that it needs assistance getting back to wherever it came from; likely Gigafactory Texas or potentially a Bay Area facility.

The Cybercab was also spotted in Buffalo, New York, last week, potentially undergoing cold-weather testing, but it doesn’t appear that’s where this incident took place.

It is important to remember that the Cybercab is currently undergoing some rigorous testing scenarios, which include range tests and routine public road operation. These things help Tesla assess any potential issue the vehicle could run into after it starts routine production and heads to customers, or for the Robotaxi platform operation.

This is not a one-off issue, either. Tesla had some instances with the Semi where it was seen broken down on the side of a highway three years ago. The all-electric Semi has gone on to be successful in its early pilot program, as companies like Frito-Lay and PepsiCo. have had very positive remarks.

Tesla reveals its first Semi customer after launch

The Cybercab’s future is bright, and it is important to note that no vehicle model has ever gone its full life without a breakdown. It happens, it’s a car.

Nevertheless, it is important to note that there has been no official word on what happened with this particular Cybercab unit, but it is crucial to remember that this is the pre-production testing phase, and these things are more constructive than anything.

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Investor's Corner

Tesla analyst teases self-driving dominance in new note: ‘It’s not even close’

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Credit: Tesla

Tesla analyst Andrew Percoco of Morgan Stanley teased the company’s dominance in its self-driving initiative, stating that its lead over competitors is “not even close.”

Percoco recently overtook coverage of Tesla stock from Adam Jonas, who had covered the company at Morgan Stanley for years. Percoco is handling Tesla now that Jonas is covering embodied AI stocks and no longer automotive.

His first move after grabbing coverage was to adjust the price target from $410 to $425, as well as the rating from ‘Overweight’ to ‘Equal Weight.’

Percoco’s new note regarding Tesla highlights the company’s extensive lead in self-driving and autonomy projects, something that it has plenty of competition in, but has established its prowess over the past few years.

He writes:

“It’s not even close. Tesla continues to lead in autonomous driving, even as Nvidia rolls out new technology aimed at helping other automakers build driverless systems.”

Percoco’s main point regarding Tesla’s advantage is the company’s ability to collect large amounts of training data through its massive fleet, as millions of cars are driving throughout the world and gathering millions of miles of vehicle behavior on the road.

This is the main point that Percoco makes regarding Tesla’s lead in the entire autonomy sector: data is King, and Tesla has the most of it.

One big story that has hit the news over the past week is that of NVIDIA and its own self-driving suite, called Alpamayo. NVIDIA launched this open-source AI program last week, but it differs from Tesla’s in a significant fashion, especially from a hardware perspective, as it plans to use a combination of LiDAR, Radar, and Vision (Cameras) to operate.

Percoco said that NVIDIA’s announcement does not impact Morgan Stanley’s long-term opinions on Tesla and its strength or prowess in self-driving.

NVIDIA CEO Jensen Huang commends Tesla’s Elon Musk for early belief

And, for what it’s worth, NVIDIA CEO Jensen Huang even said some remarkable things about Tesla following the launch of Alpamayo:

“I think the Tesla stack is the most advanced autonomous vehicle stack in the world. I’m fairly certain they were already using end-to-end AI. Whether their AI did reasoning or not is somewhat secondary to that first part.”

Percoco reiterated both the $425 price target and the ‘Equal Weight’ rating on Tesla shares.

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