Starship – SN9 – High-Altitude Flight Test

COVID19 and the riots were the big stories. Without them, doubt the media would have been able to resist the drama of astronauts possibly blowing up by connecting the two different rocket projects.

That opening shot with one spaceship launching while the other was still on the pad was priceless, though... and they are iterating so quickly that much of the value from SN10 was already gained in the manufacturing process.

As others mentioned, space in rocket build area looks like it's to a point where any delay in getting completed test articles to test stands, means delaying construction. I suspect they weren't completely confident when they'd get FAA approval after getting into a full launch cycle and being pretty clearly rebuked (pulling of the TFR and announcement of the scrub by the FAA). So better to get it to the stands so they could move on the fronts they could... but also to be understood...

There's probably a cost/benefit calculation here, too: SN15 has been said to be bringing significant design improvements over the current design they're flying, and SN10 is of the older design. SN11 is probably ready or very close to ready for "high-bay" stacking... SN10 was waiting in the high-bay along with the first booster (BN1)leaving really no room for anything else to go in there. SN12, also of the same older design is being pro-actively scrapped right now and SN13, SN14 are also not going to happen so they get to SN15 faster. They have a test article at the launch site (SN7.2) to test a different construction material (3mm think stainless steel vs. the current 4mm). All that said and done... I'm sure they want to get SN10 in the air and would be disappointed by losing it... but they already have their sights fixed on the future it doesn't completely represent.

Their hangars seem to be filling up and I am sure they want to make room for SH1 and SN11.

It was ready to go, they got a week's jump on setting it up, and it isn't as close to the landing site as it looks.

I think they will practice until they get the landing right all the time.

The engines with vacuum optimized nozzles are not suited for landing. They can not be gimbaled and are very over-expanded as well. I would not be surprised if the engines with vacuum nozzles destroyed themselves if they were fired at sea-level.

Vacuum engines can’t be used at low altitudes, exhaust underexpansion cause flow to delaminate which will damage the nozzle which goes the way rocketry goes

The landing burn will relight 2 engines to slow down, then land on 1 engine.

SN8 was really close. Only a couple more seconds before the engine ate itself would do. :)

I don’t think that’s quite right. With SN8 they ended up with low pressure in the header tank and not enough fuel for the turbo pumps.

A so called “engine-rich” burn resulted, which is why there’s a flash of green flame.

Total thrust was much lower than spec, hence the hard landing even though both engines ignited.

> Just because it looks cool is not a reason to do it.

I'm pretty certain that 'looks cool' has nothing to do with it.

SN10 had to be moved away from the assembly point because SN11, SN12, etc are close behind. They needed the space.

Why wasn't SN10 further away? SpaceX is moving fast, and moving these building-sized craft around is slow.

SpaceX has a many years of experience in landing rockets. Perhaps more directly, they have a lot of experience in failing to land rockets. To that end, they've use a kind of 'fail safe' methodology, where for most of the approach, the vehicle's trajectory is toward a safe, low-value spot.

For example, during the booster return of the CRS-16 mission in 2018, there was a problem, so the booster automatically didn't translate back toward its nominal landing pad. https://www.youtube.com/watch?v=LFdep0qCmYA In that case, the problem ended up not being severe enough to cause a crash.

Since switching to low-cost stainless steel, SpaceX design philosophy is to rapidly prototype using low-cost materials and assembly line like mass manufacturing ("the machine that builds the machine").

They expect to lose many rockets along the way. They only put 3 raptor engines in there because that's the expensive part.

This is in contrast to the SLS where they spend 5 years and billions of dollars designing and building one rocket that's make of break, with the second rocket launching people.

The reason to do it is to speed things up. Spacex is willing to take risks for speed

Starship won't suicide burn. Raptor can downthrottle deeply enough to hover.

What would they replace it with?

That's for the booster. The goal is to skip landing legs for the booster, as it'll only operate around Earth, so it's "easy" to build infrastructure instead.

Starship (the 2nd stage) will always do that flip & land on legs, as it also needs to do it on Mars.

The catching arm is for the first stage, IIRC

Second stage has always been about that flip, be it on the Moon, Mars or Earth

Yeah :( Although even at the start when they had the feed they only switched between them instead of showing both.

IMO Everyday Astronaut has the best video of the landing (https://youtu.be/l4-PwxnJimg?t=16263) - this is similar to what SpaceX had with SN8

Controlled descent into terrain.

SN9 knew the ground was where it was, but had an engine mishap preventing power to match control, so I’m debating with myself whether it was CFIT or UFIT. Maybe a superposition of both?

Sure, could be. I'd like a few seconds earlier on the shot that showed the landing pad to be sure.