Space Sunday: crunches, telescopes and ambitions

Starship SN3 tank section sits as a crumpled mess after the pressurisation test failure. Credit: SpaceX

I’ve covered the development and plans SpaceX have for their mighty Starship vehicle – designed to be capable of lifting up to 100 tonnes of cargo, or 100 people to the Moon or Mars – and its equally massive reusable booster on numerous occasions. For the last 12+ months, the company has been engaged in fabricating a series of prototype / test versions of the Starship vehicle, some of which are (or were) intended for actual flight testing. But it has been far from plain sailing for the company.

The first vehicle in the series, called simply “Starship Mark 1”, and built at the company’s Boca Chica test facilities in southern Texas, underwent a series of tank pressurisation tests that were initially positive, at least up until a full pressure test – mimicking the pressure the vehicle’s tanks would be under when fully fuelled and awaiting launch – on November 20th, 2019. SpaceX CEO Elon Musk anticipated this test might end in failure – and it did, the fuel tank bulkheads suffering a catastrophic failure.

Sections of the Starship SN3 unveiled on March 26th, 2020. Note the black cylinders of the deployable landing legs on the section on the right. Credit: SpaceX

A second prototype, Starship SN1, had a series of refinements built into the tank bulkheads and was subjected to a similar test on February 28th, 2020. This time, the bulkheads survived, but a failure occurred with a “thrust puck” at the base of the tank that takes the load from the vehicle’s Raptor engines, again resulting in the loss of the vehicle. As a result, the third prototype, SN2 was modified and then stripped back just to its tanks so that a further test of the “thrust puck” weld on March 3rd – which it passed successfully.

The adjustments were then made to the next prototype: SN3, a vehicle intended to start flight tests. The sections of SN3 were revealed on March 26th, 2020, after which the main tank section was moved to a test stand where it would also undergo a series of pressurisation tests, culminating a full pressurisation using liquid nitrogen to simulate a fuel load at typical launch temperatures. This took place on April 2nd (CST) / April 3rd (UK / CET), and once again ended in failure and the loss of the tank section.

Video recorded by (not an official NASA site) shows the tank under pressure and venting gas (as expected) before the upper portion initially buckles before completely collapsing.

Immediately following the test, Musk indicated via Twitter the the loss of the section may have been a result of the test being incorrectly configured, rather than a failure with the vehicle itself – although analysis of the data is continuing.

A significant difference between the SN3 vehicle and the prototypes that came before it was the inclusion of deployable landing legs, included in the vehicle to allow it to undertake the system’s first, low-altitude “hops”. SpaceX had already applied to the Federal Aviation Administration (FAA) for permission to complete a static fire of the vehicle’s raptor engine – a required precursor for any test flights – and the FAA had in turn issued a notification to airmen to remain clear of the airspace around the Boca Chica test area between April 6th to 8th, a move consistent with an engine static fire test, which the failed pressurisation test was in turn something of a precursor.

Artist impressions of Starship. On the left, the crewed and cargo variants, on the right a typical large payload deployment. Credit: SpaceX Starship User Guide

It’s not clear how the incident with SN3 affects Starship testing; a further test vehicle, Starship SN4 is under construction specifically to complete higher-altitude flight tests before SN5 undertakes flights in excess of 20km altitude. Whether this SN4 will now be used for the low altitude hops and SN5 and SN6 for the higher flights, or the range of flights for SN4 is extended to cover both low and intermediate altitude tests remains to be seen. All the company has indicated is that the failures encountered so far shouldn’t deflect them too much in their aspirational goals of a lunar vicinity flight in 2022 and a Mars flight in 2024. In respect of these, in March 2020, SpaceX issued payload and crew guidelines for customer wishing to launch cargoes to orbit – a further option for the Starship / Super Heavy booster combination being cargo flights and payload deployments, replacing the company’s Falcon 9 and Falcon Heavy boosters.

James Web Unfurls its Telescope for the First Time

NASA’s next great observatory, the James Webb Space Telescope, has fully deployed its primary mirror under test conditions for the first time, marking another milestone on its journey to space.

The giant mirror, 6.5 metres across, is so large, it must be folded and stowed during launch, requiring it to be carefully deployed while on-route to its final L2 halo orbit beyond the Moon – which will take it around 14 days to initially reach, and another 14 to settle into.

Prior to the SARS-CoV-2 situation caused NASA to suspend work on the telescope, it was hooked-up to a gravity / mass compensating rig – needed to support the weight of the two deployable “sides” of the mirror as well as the mass of the central section – allowing the mirror’s deployment motors to be spun up and the entire mirror assembly put through its actual deployment routine.

JWST deployment. Credit: NASA

The test was one of the final large-scale crucial test of JWST’s key systems. Integration testing of the telescope’s systems and those of it’s “bus” that includes the sun shield were completed in early 2019, while a test deployment of the complex and delicate sun shield “sandwich” – vital to keeping the telescope cool and allowing it to “see” in the glare of the sun – was successfully in October 2019.

Even so, the project has several more hurdles to clear before its actual launch date can be confirmed without risk of further significant delays, and such confirmation will not be given until after the coronavirus situation is no longer impacting the project, and a further review of its overall status completed.

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