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Comment by compsciphd | Hacker News Reader

I'm wondering what the term "launch window" is referring to here. When one is going somewhere in space, it makes sense to me, as one wants things to be lined up well for an efficiency (/possibility). i.e. the launch window is when we can get where we want to go, and if we launch outside of it, we wont be able to. But if one is just going up and going down without any real concern of going anywhere in specific, what does a launch window mean?

I can imagine it perhaps has to do with having a "clear space" to launch, but that seems something much more flexible. I'm wondering what it means here?

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They have NOTAMs out to keep the airspace clear, and also have to keep a few different sections of sea clear of marine traffic (2 landing zones, and an area surrounding the takeoff zone). Add to that road closures, people evacuated from the local village etc, you just can't carry on with all this for an extended period of time.

Slightly edited definition from NOTAM [1]:

A Notice to (Airmen|Air Men|Airman|Air Missions) is a notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a location that could affect the flight.

Might be helpful to fellow aviation-challenged folks.

[1]: https://en.wikipedia.org/wiki/NOTAM

Copying analysis/speculation from the reddit thread:

- in the morning so they've got the maximum amount of daylight to deal with any possible outcome

- 62mn max window duration is the limit for acceptable propellant boil off

As others have said, scheduling no-fly zones on multiple locations (Starship will crash land near Hawaii), but also things like "we only have so much super chilled liquid oxygen and it's going to be boiling off".

Tim Dodd's stream said a few minutes ago that once they get within 45 minutes of launch, they are either launching today or not for two more days, because by that point if you try to unload all the fuel and oxygen too much boils away and you need to bring in truckloads of it more for the next attempt.

Space is hard.

Also, keep in mind that this is an (almost) orbital launch, and that it's re-entering. In this case, it's re-entering just north of Hawaii, so there may be reasons in that region to limit the launch window.

They have to reserve airspace and "sea space" so no one can stumble under the path of a rocket which may explode.

They have to empty the town nearby, close roads, etc.

They also arranged a NASA plane to come and observe.

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