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Friday, April 15, 2022

Artemis Wet Dress Rehearsal Flops Again - SpaceX Booster 7 Pressure Tested

The WDR for Artemis ran into another issue yesterday and the test was halted late in the day.  

Teams concluded today’s wet dress rehearsal test at approximately 5:10 p.m. EDT after observing a liquid hydrogen (LH2) leak on the tail service mast umbilical, which is located at the base of the mobile launcher and connects to the rocket’s core stage. The leak was discovered during liquid hydrogen loading operations and prevented the team from completing the test.

There is no further update on the web site.  A roughly 50 minute long press conference was held, but I haven't listened to it yet.  It's a YouTube link that seems to be audio only.  The first nine minutes is just a blue screen with text and background music.  In the "Heavy Rockets" section of this week's Ars Technica's Rocket Report newsletter, Author Eric Berger relays reports that the Artemis team reported they weren't going to fill more than 5% of the liquid hydrogen tank.   The LOX tank was brought up to 50% full. 

The question is whether they're going to try to do more on the pad or roll back to the Vehicle Assembly Building.  Delays with new ground systems and a new rocket are probably inevitable, but NASA has to be disappointed that we are now on day 14 of a two-day test.  My opinion is that while this test accomplished things, it was a failure.  When it comes time to launch cargo or people, it's a pass/fail test without the slightest tolerance for failure.  "Mostly working" doesn't cut it.  

We're in day 14 of a two day test on a booster that was supposed to fly six years ago.  And the problem they're having is with the most basic requirement there is.  They can't even fuel the stupid thing.


Meanwhile out a Boca Chica, stress testing of Booster 7 has begun.   

Known as Super Heavy Booster 7 or B7, the prototype is the first of its kind designed to support up to 33 new Raptor V2 engines – each potentially capable of producing up to 230 tons (~510,000 lbf) of thrust at liftoff. Even with just 20 such engines installed, Super Heavy – measuring around 69 meters (~225 ft) tall and nine meters (~30 ft) wide – will be the largest and most powerful rocket stage ever tested. That potentially unprecedented power is why SpaceX has custom-built a complex structural test stand to explore Super Heavy’s true performance envelope in a slightly less risky manner.

The tests had a few impressive looking moments but viewers mostly wouldn't know what's going on without pressure gauges to watch.  This video brief starts right before some impressive venting during the test.  

Increasing the central engine count from 9 to 13 was already certain to up the amount of stress future Super Heavy thrust pucks would need to survive by almost 45%. But combined with Raptor V2’s thrust increases, Super Heavy Booster 7’s thrust puck could actually be subjected to at least 80% more thrust at liftoff. Altogether, Super Heavy B7’s 33 engines should be able to produce ~7600 tons (~16.8M lbf) of thrust compared to Super Heavy B4’s ~5400 tons (~11.9M lbf). As a result, though it’s odd that SpaceX never did significantly test Booster 4, it’s no surprise that the company chose to give Booster 7 priority as soon it was ready.
...
After a few false starts and at least one ‘pneumatic proof test’ that likely saw Booster 7 pressurized with benign nitrogen gas, SpaceX began stress-testing the upgraded Super Heavy in earnest on April 14th. First, the booster was filled about a third of the way with roughly 1000 tons (~2.2M lb) of liquid nitrogen (LN2) or a combination of liquid oxygen (LOx) and LN2. Once the rocket was fully chilled, there were clear signs of some kind of added stress as large sheets of ice that had formed on the side of B7’s skin broke apart and fell off.


Screen capture from the above-linked video.  NASASpaceflight.com credit.



4 comments:

  1. SpaceX can afford to test to destruction because they can build a new one in weeks.

    Unlike NASA. There is no other SLS rapid prototyping or production. Which is part of the reason the damned thing is so damned expensive.

    I prefer the SpaceX way.

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  2. One wonders how much of the ground systems problems were with hardware from the Apollo era?

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    1. My guess is little to none because it's a new mobile launch tower that was also massively over budget. Back when I wrote a column on it, they were nearing a billion dollars spent on a mobile launch tower that was bid at $54 million. Cost plus? To be fair to the prime contractor, much like SLS, the requirements changed constantly and required lots of changes.

      Still, that's over 18x the original bid. And when they went to put it into service, they found the vertical portion wasn't actually perpendicular to the horizontal portion. If I'm remembering correctly.

      With the exception of what (I think) was a backwards check valve (because how many ways can it be installed incorrectly?) in the upper stage, all the issues were with the Mobile Launcher.

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    2. And that platform itself was from Apollo. Modified MANY times, of course, but the structure and as much of the toys inside as possible.

      KSC is at the tail of the pipeline, and those upstream have spent all the available funds.

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