Talk:SpaceX Starship integrated flight test 4

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✠ SunDawn ✠ (contact) 06:53, 9 May 2024 (UTC)

Flight Profile

We don't have official times from SpaceX, and it may be different from IFT-3, so shouldn't the Flight Profile Table be removed? Redacted II (talk) 15:26, 22 May 2024 (UTC)

We should remove it for now, as it's always possible for things like prop load times to change by a few seconds. Stoplookin9 Hey there! Send me a message! 00:00, 23 May 2024 (UTC)

SpaceX has announced official times here but I can't find a source other than this. User3749 (talk) 14:10, 24 May 2024 (UTC)

The source you found is reliable. I'll go add the timeline. Redacted II (talk) 14:15, 24 May 2024 (UTC)

Source for Jettison of hot-staging ring

At the revision by the time I start this thread, (https://en.wikipedia.org/w/index.php?title=SpaceX_Starship_integrated_flight_test_4&oldid=1227614254) the Flight Profile section contains a statement that goes

To reduce mass during descent, SpaceX is using a temporary design change on this test flight to jettison the booster hot-staging ring. Longer term, SpaceX intends to redesign the hot-staging ring for lighter weight and tight integration with the booster, which will then not be jettisoned.

Inline comment states the intent to redesign was

per SpaceX launch day livecast, at 14:45

Current source for these two sentences doesn't really cover the statement other than proving the ring was indeed jettisoned. A note requesting secondary source is also present.

Is the "launch-day livecast" an acceptable source? (I'd assume there's some way to put a video stream as a source but I'd need to figure it out.) If a primary source (SpaceX) is able to explicitly state these points, would a secondary source be still needed? XrayBravoGolf (talk) 21:31, 6 June 2024 (UTC)

IMO, a secondary source is not needed, as the Hot Staging Ring was visibly jettisoned from the booster (and later visible during EDL) Redacted II (talk) 15:15, 7 June 2024 (UTC)

Periapsis may be incorrect

Given the apoapsis at 213 km of altitude and velocity of 26221 km/h, the periapsis is at -1228 km. The same result can be obtained from other points in time (e.g. at T+10:29 the altitude reaches 164 km and velocity equals 26495 km/h which matches a periapsis altitude around -1200 km). The cited source says "maybe about 10 kilometers below the surface" which imo means it's just a guess. 91.94.89.242 (talk) 01:12, 7 June 2024 (UTC)

The velocity doesn't include earths rotation (otherwise, velocity at launch would be over 1000 km/h!).

Factoring this in, I get a perigee of -12 km (I calculated from telemetry at T+10:30, as at that point latitude would have been close to when it had been at launch) Redacted II (talk) 15:14, 7 June 2024 (UTC)

You may be right indeed. We should still look for a better source that says where the numbers come from though.

But also, the telemetry doesn't generally give us the direction of that velocity so we can't just "add Earth's rotation". It should be easily doable if we assume the telemetry is from the reference frame of the launch. 83.20.165.154 (talk) 15:29, 7 June 2024 (UTC)

I don't think there is a better source. SpaceX doesn't publish apogee and perigee, and previous launch's sources were tweets from Jonathan McDowell.

99% (at least) of the velocity is in the direction of Earths rotation (this is done to reduce dV requirements, and is why the majority of launch pads are on an eastern coast), so the simple addition isn't inducing much of an error. Redacted II (talk) 15:40, 7 June 2024 (UTC)

Yeah, but the trajectory was constantly changing so to calculate the periapsis accurately we need to know the velocity after engine cutoff, above most atmosphere and ideally after it stopped venting propellant. 83.20.165.154 (talk) 15:46, 7 June 2024 (UTC)

The trajectory wouldn't have changed all that much (Air is pretty negligible until ~120 km, and those vents aren't all that powerful), and the farther from T-00:00:00, the less accurate the calculation would be, due to longitudinal drift. Redacted II (talk) 15:49, 7 June 2024 (UTC)

Our armchair analysis doesn't matter, as that would be original research. Even an unachieved orbital altitude like the -10 km shown in the article inforbox now, should not be there, as it just misleads the Wikipedia reader. It is a theoretical number that is only the altitude IF the spacecraft COULD get there.

Moreover, any information in an infobox should summarize key facts that appear in the article, not supplant them and not be the only place in an article that the data is discussed, per MOS:INFOBOX. So the periapsis negative number will be removed unless it merely summarizes something explicated in a paragraph in the article prose. N2e (talk) 11:04, 8 June 2024 (UTC)

The perigee is important information: without that information, the details of the orbit are unknown, except for Apogee.

Think of the difference between GTO and GEO. The apogees are the same, but the perigees are VERY different.

The suborbital nature of the launch can be discussed in the article. For example: "The vehicle, while achieving a near-orbital velocity, was on a suborbital trajectory, as its perigee was ~10 km below Earths surface". That text could easily be added to the article. Redacted II (talk) 13:13, 8 June 2024 (UTC)

Fully agreed that a section on whether this launch (and all previous ones) were suborbital or transatmospheric would be a great addition. Sadly, I haven't found any reliable sources doing that analysis.

Apoapsis and periapsis describe the shape of the orbit. It doesn't matter that the spacecraft would not be able to get to one of them, because knowing them still gives us important information (like the fact that it would crash into the surface or that it would re-enter the atmosphere).

Btw original research must not appear in articles. But that's not what's happening here. I brought up my own calculations on the talk page and these were only used to evaluate whether a somewhat cited claim should be removed from the article or not. 83.20.175.130 (talk) 13:51, 8 June 2024 (UTC)

There are reliable sources that state the perigee for IFT-3, IFT-2, and even IFT-1(!).

Additional, routine math is permitted on Wikipedia. Exponents are very much routine math (especially if you have a calculator) Redacted II (talk) 13:58, 8 June 2024 (UTC)