Scivillage.com Casual Discussion Science Forum

Here's a new 24/7 live cam of the SpaceX rocket engine test stands at McGregor. It's split screen and shows a panorama of the whole site, plus closeups of the various test stands.

The problem is that while they test frequently during the day, they don't announce their test schedule, so much of the time not much is visibly happening. And they apparently have a quiet time at night when they don't fire rocket engines in order not to disturb nearby residents. (It's a rural area in the vicinity of Waco but there are people around. Closest is probably the Army's Fort Hood to the west.)

I'm told (not 100% sure that it's true) that some of the cattle at McGregor belong to SpaceX and are tended by SpaceX cowboys! The explanation is said to be a Texas tax law that gives tax advantages to ranches (it's Texas!). So SpaceX runs cattle on their property in order to qualify as being a ranch. (That's the story anyway, true or not.)

Those who watch McGregor report that two Raptor engines have exploded on the test stand in the last two days. It isn't clear why this happened, but it's likely that these engines are being run at redline to better understand their performance envelope. So they may or may not have been tests-to-destruction.

Video of the second explosion.

https://twitter.com/nextspaceflight/stat...8390935553

Latest from McGregor is a Vacuum Raptor in the horizontal test stand running for six minutes (360 seconds)! That's impressive, but the upper stage RVacs will need to be able to perform long burns necessary to put Starships in orbit.

They are making progress.

https://twitter.com/KSpaceAcademy/status...3107657729

Sorta goofy McGregor video

What may or may not be a new Raptor record, a ~385 second (6.42 minute) burn. At least it's the longest test fire yet observed on the McGregor cams.

https://twitter.com/nextspaceflight/stat...7741114369

Graphic from Tim Dodd comparing the Raptor 1 and Raptor 2 engines.



Tim doesn't mention it, but besides the performance advantages outlined here (lighter & more powerful), the Raptor 2 is also said to be easier to manufacture, thus more amenable to mass production.

Elon replied with

Most importantly, we need to delete or thermally protect remaining secondary structure, so we can remove shrouds

https://twitter.com/elonmusk/status/1547478741655228416

and

All mass necessitated by an engine design should count as engine mass, eg shrouds, TVC hydraulic power or excess purge gas.

Raptors in production now have electric TVC, saving over a ton of hydraulics mass on booster.

https://twitter.com/elonmusk/status/1547759390513512455

Chris Bergin posted this short video of impressive Raptor engine TVC action on the Tripod at McGregor

https://twitter.com/NASASpaceflight/stat...8170948609

Space Cows!

The story (it may or may not be true) is that SpaceX runs cattle on its McGregor property because Texas law gives a tax advantage to ranchers.

But for whatever reason, McGregor is home of the SpaceX Space cows. The cows graze near the McGregor test stands where they have grown accustomed to rocket engine test firing happening near them and even the occasional explosion.

Elon has announced that a version 3 Raptor has achieved 350 bar chamber pressure in a 64 second burn on the Tripod at McGregor. This equates to 269 tons of thrust from a single engine. A Starship booster has 33 engines, which totals 8877 tons of thrust.

He added:

"To be frank, we did not expect the engine to survive a full-duration run at that pressure. It is uncharted territory."

https://twitter.com/elonmusk/status/1657249739925258240

"Raptor chamber wall might have had the highest heat flux of anything ever made."

At least anything that wasn't immediately vaporized by the heat it produces, like nuclear weapons.

https://twitter.com/elonmusk/status/1657254777691185152

Video by NASASpaceflight.com

https://twitter.com/NASASpaceflight/stat...5362233344

Meanwhile at McGregor...

Zack asked what the purpose of this long-duration highly-gimballed burn was, and Elon said simulating landing burn at full gimbal angle.

https://twitter.com/SpaceX/status/1692260577866092863