SpaceX Starship : First Flight : Starbase, TX : 20 April 2023 - DISCUSSION

[alphacentauri]

(shifting this from another discussion thread) Quick question about the 7/24 OFT scheduling. As a non-US person, can somebody confirm my timezone maths, that the current suggested launch windows (12Z-15Z) are roughly dawn-till-midmorning in TX, and it would be night-till-barely-dawn at the wet-LZ near HI? IIUC, 16Z is 06HI, about 20min before sunrise there - anything much earlier is still dark. This is noting of course the TX-HI flight time of ~60-90min...

It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

Your time zone observations are correct. My guess is they don't expect the ship to survive reentry so it doesn't matter that the landing zone will be dark. They probably chose the time to favor best conditions for launch in TX without worrying about HI. There may be other considerations to prefer a morning launch instead of an afternoon launch, perhaps likelihood of better weather?

[Alberto-Girardi]

(shifting this from another discussion thread) Quick question about the 7/24 OFT scheduling. As a non-US person, can somebody confirm my timezone maths, that the current suggested launch windows (12Z-15Z) are roughly dawn-till-midmorning in TX, and it would be night-till-barely-dawn at the wet-LZ near HI? IIUC, 16Z is 06HI, about 20min before sunrise there - anything much earlier is still dark. This is noting of course the TX-HI flight time of ~60-90min...

It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

Your time zone observations are correct. My guess is they don't expect the ship to survive reentry so it doesn't matter that the landing zone will be dark. They probably chose the time to favor best conditions for launch in TX without worrying about HI. There may be other considerations to prefer a morning launch instead of an afternoon launch, perhaps likelihood of better weather?

considering they launched SN11 in an extremely thick fog I would say that the do not care enough about landing visuals to change the launch window that apparently is good for them. After all they still will have the telemetry and inboard footage that might tell them more than a splashdown video that might not even exist since the distance from the island. (I don't know if they can get a boat close due to the closure).

[Robotbeat]

Likely will be able to get aerial video of an attempted splashdown.

[edzieba]

For EDL, entering with the atmosphere cool improves IR background for ground observations from the test range.

[plank]

Edit: wrong thread.

[sdsds]

For completeness, added maps of the research buoys, and a global ground track.

I note with interest the hazard area maps don't seem to cover a case where the booster under-performs but Starship separates and then targets a disposal location in either the mid-Atlantic or Indian Ocean. Am I missing something?

I'm also curious about speculation (informed or otherwise) about when after liftoff the vehicle will begin to pitch towards its intended trajectory. Approximately what length below the booster is the supersonic exhaust flow expected to extend? Would the vehicle begin to pitch at about that altitude?

[Herb Schaltegger]

Approximately what length below the booster is the supersonic exhaust flow expected to extend?

That's not how supersonic flow works. Perhaps you can be more precise in your question.

[TheRadicalModerate]

For completeness, added maps of the research buoys, and a global ground track.

I note with interest the hazard area maps don't seem to cover a case where the booster under-performs but Starship separates and then targets a disposal location in either the mid-Atlantic or Indian Ocean. Am I missing something?

I'm also curious about speculation (informed or otherwise) about when after liftoff the vehicle will begin to pitch towards its intended trajectory. Approximately what length below the booster is the supersonic exhaust flow expected to extend? Would the vehicle begin to pitch at about that altitude?

The launch hazard area extends all the way to the Florida Keys.  If there's that serious an underperformance or Starship fails to start up, they'll destroy the Starship and it'll fall into that area.

I suspect that the landing hazard area going as far west as the Marshalls probably handles 95% of the cases where the Starship itself underperforms.

As for pitchover, they're going to be lofting the hell out of the thing, so there's no need for an early pitchover.  T/W=1.5 means that the vehicle should be 100m above the tower (145m high) in exactly 10s.  If that's too extreme an exhaust load, I guess they could pitch over sooner, but that seems like a terrible idea on a first launch.  It takes 7.6s to clear the tower, and you certainly wouldn't want to pitch before then.

[CameronD]

The launch hazard area extends all the way to the Florida Keys.  If there's that serious an underperformance or Starship fails to start up, they'll destroy the Starship and it'll fall into that area.

I suspect that the landing hazard area going as far west as the Marshalls probably handles 95% of the cases where the Starship itself underperforms.

I guess that also means a ridiculously-high likelihood of a vessel incursion and resulting launch hold on this first one.

Let's hope not, but either way: LOOK OUT BELOW!!

[TheRadicalModerate]

If I recall correctly, all Raptor powered launches so far have nailed the going up part. I feel pretty good about their chances from liftoff to staging. Stage sep concept is new/never been done, if they get past that, man, they are in business.

Reminder: reliability of .99 (example) for each engine is a reliability of .99^^33=0.71 that all 33 Raptors will start.

If you go by the only example we have, where they succeeded in lighting 31/33, that gives it a 13% chance of lighting off all 33.  Of course they know why those two engines didn't fire, and have almost certainly mitigated those factors, so we'll see.

Sounds like we’ve almost got the ingredients for a good old fashioned frequentist vs. bayesian smack down.

[FutureSpaceTourist]

twitter.com/ercxspace/status/1645564399556661248

https://twitter.com/nasaspaceflight/status/1645619546823221248

If this scene becomes a reality for the test flight, SpaceX will have seriously overachieved!

I'd take a launch and some good first stage action to get away from potentially damaging the launch site.

Some nice downrange - I'll take it.

Maybe lose a few engines - keep calm; she can keep going.

MaxQ - it's getting tasty now! Lots of useful data.

Staging - hey, we're winning now! Booster's going into the drink as planned.

Ship ignition - we've got RVacs firing in space!

Ship re-entry - TPS data!

Ship survives and lands near Hawaii - faints.

Seriously though. Launch, clear the launch site. Anything else is a bonus.

[TheRadicalModerate]

The launch hazard area extends all the way to the Florida Keys.  If there's that serious an underperformance or Starship fails to start up, they'll destroy the Starship and it'll fall into that area.

I suspect that the landing hazard area going as far west as the Marshalls probably handles 95% of the cases where the Starship itself underperforms.

I guess that also means a ridiculously-high likelihood of a vessel incursion and resulting launch hold on this first one.

Let's hope not, but either way: LOOK OUT BELOW!!

There are two different classes contained in the notice to mariners:

1) Hazardous operations, rocket launching
2) Hazardous operations, space debris

Anybody know how they're each treated as launch criteria?  If SpaceX has to wait until a sizable chunk of the maritime traffic in the Gulf of Mexico gets the word to cease north-south operations and actually obeys it, they're going to be waiting a while.

[billh]

Video of the same rainbow

https://www.youtube.com/shorts/mOwBHnMb6-k

The rocket at the end of the rainbow!

[TheRadicalModerate]

twitter.com/ercxspace/status/1645564399556661248

https://twitter.com/nasaspaceflight/status/1645619546823221248

Is it just me, or do the two guys in the Zodiac look like they need to be hefting harpoons?

[billh]

twitter.com/ercxspace/status/1645564399556661248

https://twitter.com/nasaspaceflight/status/1645619546823221248

Is it just me, or do the two guys in the Zodiac look like they need to be hefting harpoons?

Call me Ishmael.

[OneSpeed]

I note with interest the hazard area maps don't seem to cover a case where the booster under-performs but Starship separates and then targets a disposal location in either the mid-Atlantic or Indian Ocean. Am I missing something?
...

If the booster dramatically under-performs, then I'd suggest that SESU will be aborted, and the ship either be terminated or re-enter ballistically. Even if the booster performs perfectly, then my simulation suggests that with a maximum of 90% thrust, and no payload, the ship would only reach about 600km downrange ballistically. I've added the ground track of that scenario to the LHA map.

[whitelancer64]

*snip*
It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

Video of an anomaly is almost always far less helpful than the data from the thousands of onboard sensors. While we would all love to see a clear video stream of the launch, the reality is that telemetry is much more important.

[wannamoonbase]

*snip*
It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

Video of an anomaly is almost always far less helpful than the data from the thousands of onboard sensors. While we would all love to see a clear video stream of the launch, the reality is that telemetry is much more important.

100% agree, the resolution of telemetry will exceed video, especially after the first few miles.

However, daylight on the pacific re-entry area might be really helpful. 

[Vettedrmr]

Video of an anomaly is almost always far less helpful than the data from the thousands of onboard sensors. While we would all love to see a clear video stream of the launch, the reality is that telemetry is much more important.

But it's not an either/or.  There's no outside pressure to launch, so why not wait for good visual weather?

[whitelancer64]

*snip*
It feels to me like having as much daylight as possible at both hopeful ends of this test flight might be helpful for diagnosis if anything is off-norminal... (let alone any cool soft-landing footage potentially!). Thoughts or corrections?

Video of an anomaly is almost always far less helpful than the data from the thousands of onboard sensors. While we would all love to see a clear video stream of the launch, the reality is that telemetry is much more important.

100% agree, the resolution of telemetry will exceed video, especially after the first few miles.

However, daylight on the pacific re-entry area might be really helpful.

If they were doing a recovery, then I'd agree, but there is no planned recovery for either booster or Starship, and an intact landing for either is very unlikely.