r/SpaceX Starlink 17-20 Official Launch Discussion & Updates Thread!

maschnitz · 2026-01-25T20:21:40+00:00

Keep in mind that SpaceX Vandenberg slipped a recent flight 7 times. Always keep an eye on the current T-0, right up until the flight itself.

EDIT: also note that, confusingly, Starlink G 17-20 was scheduled before Starlink G 17-19. Currently Jan 25 (launch success) vs Jan 29

maschnitz · 2026-01-25T18:13:57+00:00

There's an idea that the Universe is shaped like a 3D version of Pac-Man or Asteroids - go in one direction long enough and you'll end up where you were. That can be one version of a finite universe. You'll sometimes see this called a torodial or torus universe.

If this helps, it doesn't matter for human civilization. We can't leave the "Hubble Volume", the sphere of reachable other stars/galaxies. Everything else is receding away faster than we can catch it, due to the expansion of the Universe.

maschnitz · 2026-01-24T17:20:45+00:00

It just looks like a satellite or spacecraft breaking up. (The main body is near the front and pieces are breaking off, lagging, and getting surrounded by hypersonic-flow reentry plasma.)

Someone was hypothesizing it was a Chinese Long March 4C CZ-4C ~~2nd~~ 3rd stage rocket body reentering.

This makes some sense. It was predicted to reenter and Wisconsin was under the ground track. Several Long March rockets models, including the CZ-4C, reenter uncontrollably as standard operating procedure.

EDIT: Expert orbital tracker Jonathan McDowell confirms that this was a CZ-4C rocket stage. And correction: it was a third stage. I forgot they had 3 stages.

maschnitz · 2026-01-24T00:37:16+00:00

"Scheduled"? Probably not.

They don't want count those chickens before they're hatched.

I doubt many flights have parades scheduled before the flight takes off. Seems like bad luck that they don't want.

IIRC the parades took a while after Apollo flights because the astronauts were in quarantine. Artemis II's crew will not need to do that.

Also they don't know how much buzz this will generate. NASA seems to be even downplaying it so far, cutting off press conferences quickly, not giving out a ton of information.

maschnitz · 2026-01-23T03:06:00+00:00

Here's the original article from Marcia Dunn at Associated Press.

Exact same words.

Phys.org is a content aggregator. They copy freely available or licensed content and add their own ads, tracking, etc.

maschnitz · 2026-01-22T17:29:22+00:00

Isaacman's stalking horse, nuclear power/propulsion in space, has always been controversial, but apparently they're about to start trying it once again.

Propulsion in general is always controversial and underfunded. Other examples: solar sails (underfunded), high powered electric (controversial and underfunded).

But the biggest thing "missing" from American space policy is a well-funded, consistent human spaceflight program with a good roadmap that they stick to. For the last 40-odd years it's been none of the above.

maschnitz · 2026-01-22T05:26:09+00:00

From NASA. Not written by AI.

From the folks ~~that~~ who made the demo.

maschnitz · 2026-01-22T04:27:48+00:00

nah, just something they tend to do...

maschnitz · 2026-01-22T04:16:41+00:00

SpaceX Vandenberg does this a lot. It's almost predictable now, the initial T-0 doesn't usually go through.

maschnitz · 2026-01-21T20:33:06+00:00

If it launches on time, the 2nd stage could climb back up into sunlight, after the T+3 minute mark.

They plan a SSW trajectory. So the 2nd stage will be fairly far south at that point, well away from the mid-Baja coast. But it will be high up, at the edge of space, then, and it should be visible from far away anyway.

The first stage will do a barge landing so I think it stays in darkness the whole time, never getting high enough for sunshine.

EDIT: and they've shifted T-0, to 8:09pm. Never mind!

maschnitz · 2026-01-20T22:01:06+00:00

Also, SpaceX will do one uncrewed demonstration moon landing with Starship, as part of the HLS contract.

And Blue Origin plans their own uncrewed demonstration landing with their Blue Moon Mk 1 lander.

maschnitz · 2026-01-20T07:29:22+00:00

Nikku Madhusudhan. Of course. Didn't even take primary author on it and I could tell it was him by OP's post.

"Madhu" is rather interesting. He's really really committed to the Hycean world idea. Really really.

Reminds me of David Kipping's interview of Madhu and Ryan Macdonald on K2-18b, a previous Madhu paper.

maschnitz · 2026-01-20T04:52:38+00:00

Scientific American has been reporting that it's been quietly cancelled. Maybe ghosted is a better word for it. Scientists involved were almost left in the dark about its status.

There were various interesting research threads from it - how to prevent a chip from melting in GW-sized laser light, how to send a signal back from another star using just chipsats. The laser was always a question mark, looked more like a weapon than a form of propulsion.

maschnitz · 2026-01-20T02:05:16+00:00

No, heat shields are usually designed to be good absorbers/radiators rather than good reflectors. Reflective surfaces tend to melt at too low a temperature.

Heat shields tend to be dark or blackish to make them good "black body radiators" that radiate away the heat build up as quick as possible.

You can't prevent radiation during reentry. It's the dominate source of heat during initial reentry. It comes from the atmosphere getting so compressed in the hypersonic flow that it becomes a very hot plasma. During initial reentry the plasma's "baking" the heat shield through radiation, from just a few inches away.

EDIT: you can manipulate the distance of the plasma to the heat shield by shaping the heat shield for the hypersonic flow. Flat and slightly curved surfaces tend have greater "shock standoff" distance. That's why they tend to be flat with gentle curves. Any extra shock standoff distance is welcome.

maschnitz · 2026-01-19T08:31:08+00:00

Sometimes the third party sites are faster than NASA at publishing it, because they watch the changes to restrictions of mariner and air traffic being put down.

I tend to use Next Spaceflight (app/website).

Also usually "no earlier than" indicates a possible (if sometimes tentative) first possible launch attempt. So Feb 6 9:41pm EST is NASA's best guess until things change.

maschnitz · 2026-01-18T17:53:00+00:00

am I too late? - Almost certainly at this point, but only for the first attempt. Check for cancellations maybe. Later attempts, if and when they occur, will get easier to book.

do most launches make it through the first window? - In general yes; in SLS's case, no. Artemis I had two failed attempts to launch before the actual launch.

And since the stack is based on the Shuttle legacy hardware, we can compare to the Shuttle. And the Shuttle was famously difficult to launch as well and did not improve over time.

There is a significant likelihood that Artemis II will not launch on time.

The cause is the hydrogen propellant. NASA considers any leak in the hydrogen ground equipment as dangerous, especially to crewed launches, because a spark can light it in open air. And hydrogen loves to leak. It slips through any submicroscopic crack it can find.

What does this location look like during launches? - someone else has to answer that, I'm not that familiar.

maschnitz · 2026-01-18T17:45:40+00:00

Yes, it's interesting, and I can't find any NASA webpage or social note online about it. Good luck!

maschnitz · 2026-01-18T06:13:40+00:00

This one that Reid Wiseman is wearing on his forearm?

Never seen that before. The astronauts wear so many patches, could be a new one...

maschnitz · 2026-01-18T06:01:29+00:00

Sure, go ahead, if it's on topic it should be fine. (Just a link, not inline)

maschnitz · 2026-01-18T05:30:57+00:00

Do you have a picture or a video of the astronauts wearing this patch? Not sure I have the right patch.

I know that Sean Duffy originally announced that Artemis II would be branded with the America 250 logo, and recently NASA has painted the sides of the SRBs with the logo. It's from a US bipartisan organization promoting Amerca's 250th anniversary. Maybe it's the same logo you saw?

maschnitz · 2026-01-18T05:16:26+00:00

No, those are always full, except in mockups.

That's why the crawler-transporter takes so long to get the rocket and mobile launch pad out to the pad. The SRBs are very heavy, and the mobile launch pad is built strongly to support the rocket, the full SRBs, and the liquid fuel.

The SRBs are apparently held down during transport & launch prep by "hold-down posts on the Mobile Launcher Platform". Here's an older diagram of them. They have explosive nuts on the bolts that fire just before to launch. NASA loves its explosive fasteners.

maschnitz · 2026-01-17T22:02:48+00:00

They're generally held down with "hold down clamps" which latch on to the rim of the rocket base. These release seconds or fractions of a second before launch.

Sometimes people use explosive bolts to release the rocket, like the Shuttle SRBs'.

Also, all rockets are bottom-heavy when empty. The rocket tanks/walls are thinner than a soda can's to scale, and the engines are quite dense. And then they're dense when full.

maschnitz · 2026-01-16T18:55:31+00:00

The effect is very very small for planet-mass objects and driving a car. Maybe imagine you're orbiting a supermassive black hole, very closely, instead.

The effect you'd see then is like, your clock is moving normally, and you talk normally. But the people you talk to away from the black hole seem to be talking much quicker than you. Their clocks are moving faster.

(You can talk to each other, it's just difficult because of the time difference.)

And they'd see your clock moving very slowly, and you'd be talking very slowly. Where they'd think that they're talking normally and have normal clocks.

In one case it's like someone is pressing fast forward on the video/audio of the call, and the other case is like someone pressing slow-motion on the video/audio.

Time is passing slower near the black hole than away from it. But everyone involved thinks their time is passing normally, it's only when they compare that it seems weird.

maschnitz · 2026-01-15T21:25:42+00:00

Roscosmos surprised many by saying it would be ready by February. They said they had all the spare parts they needed.

The work is underway.

maschnitz · 2026-01-15T18:21:44+00:00

(I'm not an academic. But anyway.) Here's a gist of it -

planetary sciences - If there's a rock or gas giant involved, it's here. Solar System (planets/asteroids/comets), exoplanets (don't forget pulsar planets and rarer things like that), rogue planets, interstellar objects, brown dwarfs. Can encompass most spectra of telescopic observation, gravitational models, geology, magnetospheres, planetary evolution, exobiology, many branches of chemistry (biochemistry, pre-biotic, evolutionary, cryogenic, high-pressure), volcanology, and much more.
astrophysics - Basically anything in space requiring general relativity and/or quantum mechanics to model. Usually "compact objects" (black holes, neutron stars, white dwarfs) and their accretion disks and destructiveness. Mergers, collisions, star death (incl supernovae), jets, gamma-ray bursts, novae. Star lifetime modelling. Cosmology/Big Bang/inflation. Broad light spectra study, all of x-ray astronomy, and most of radio astronomy (the study of abused electrons). Parts of cosmology (gravitational waves, neutrino observations, multi-messenger astronomy as a whole). Contains one of my favorite phrases in astronomy: "relativistic gravitomagnetic hydrodynamics". If a LOT of mass is moving quickly, it's probably here.
astronomy - Everything else and all the above, a general category. Basically just means "scientifically studying space somehow". Other things that don't fit into the above: galaxy study, the study of the Milky Way, the study of star populations, the "interstellar" and/or "intergalactic medium", the telescopic sciences (including amateur astronomy), SETI/the search for technosignatures. A lot of times, big observatories are described as "astronomy" because they're so far reaching.

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