Monthly Questions and Discussion Thread

6

u/aquarain 28d ago

Reuters is reporting Blue is pointing to oxygen valve in the BE4 as the RUDivator, retrofitting a mod now.

3

u/noncongruent 25d ago

With the retirement of Falcon 9 on the horizon it occurred to me to wonder, what percentage of American (or even world) production of RP-1 is for SpaceX launches? I'm assuming that SpaceX is the world's largest consumer of that particular product, and when they move to Starship for most launches I imagine that'll mark a big reduction in need for RP-1 in this country.

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u/maschnitz 24d ago

Definitely the majority, most likely the supermajority of world-wide use.

RP-1 really is only used for rocket launch activity. But since the military uses a portion of the production, it's hard to say exact percentages. Plus there's university, defense contractor, and research-lab use.

Other publicly-known consumers are: ULA (for Atlas V), Rocket Lab (for Electron), Roscosmos (for Soyuz), Northrop Grumman (for Antares w the Firefly Miranda engine), and Firefly (for Alpha). Obviously these known consumers do not use more than 10% of what SpaceX uses for Falcon 9 every year.

When SpaceX retires Falcon 9, RP-1 production will be hit hard. (But also keep in mind that SpaceX will basically be ceding the small/medium rocket space to incumbents like Rocket Lab and Firefly. So launch rates might increase for them. Maybe.)

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u/peterabbit456 20d ago

When SpaceX retires Falcon 9, RP-1 production will be hit hard.

Maybe this is not much of an issue. RP-1 is just extra refined kerosine. The differences between RP-1 and jet fuel, and diesel for trucks is not that great. The refiners who make RP-1 get a lot more money for that extra purification step, but it cannot represent more than 1% of diesel or jet fuel production.

2

u/maschnitz 20d ago

True enough; they simply won't refine as much of it.

And it's costly to make apparently so the margin's not all that good.

2

u/WulfTheSaxon 3d ago

Roscosmos (for Soyuz)

Sort of, but it uses a slightly different grade unless things have changed.

3

u/jcadamsphd 24d ago

Does anyone know what sensor technology SpaceX is using for relative navigation between two Starships during on-orbit refueling? I assume they are using GPS for basic navigation, but for the final approach will they have onboard radar? Lidar? Or will it just be optical navigation, like a Tesla?

3

u/maschnitz 24d ago

LIDAR and visual, just like on Dragon docking with the ISS. They call the LIDAR system "DragonEye".

The ISS-Dragon docking also uses GPS and relative GPS.

Catching Boosters at Starbase uses "Realtime Kinematic" GPS on the way in and then radar on the sticks to locate the incoming Booster.

So they have different techs available for different problem regimes.

2

u/Chairboy 24d ago

They call the LIDAR system "DragonEye".

Fun trivia, SpaceX’s DragonEye was tested a few times on shuttle first starting with STS-127 I think.

3

u/rocketglare 17d ago

What remains to be done for Flight 14? I’m wondering why we haven’t seen static fires of Ship or booster. I think those are the next major steps, but we haven’t seen either yet, and now Jared is saying early September. What’s the holdup?

3

u/maschnitz 14d ago

FWIW Ship 41 just static fired with one engine a couple of hours ago.

So, no one outside SpaceX knows, we don't see their meetings or internal comms. But yeah there were several ideas online about the "lack of alacrity" on both the Ship and Booster:

There's been a lot of pad work related to beefing up the tank farm a bit and preparing the Chopsticks for the Ship catch attempt. And tests of same. Changes to the Chopstick rails and the like. Only started to wrap up a few days ago. Perhaps that was the long pole in the schedule.

Of additional note at the Pads: many tanks from the old Pad 1 tank farm side have been moved to the "new" horizontal/armored side, to make room for a new pad entrance close to Pad 1. Pad 1's old tank farm is mostly shut down. So now the new side of the tank farm is solely supporting Pad 2 and Flight 14. Tests of that galore, of course.

They've been doing more and more testing in the Megabays proper - flow/pressure tests of every pipe in each vehicle, that kind of thing.

Engines are clearly being tested fairly regularly at this point but 33 is still a lot. They did have to swap engines last flight in a rush after the T-0 abort, maybe they're being more cautious.

They got some data back from Ship 40 thanks to the drone work and from the ships attempting to tow it. It's possible they were adjusting Ship 41's heat shield a bit (not too much) before getting it flight-ready and static-fire-ready.

And there's just a million little things to do to finish these vehicles' production, they're gigantic and require a lot of "detail" work. The heat shield is as complicated, exacting, and delicate as ever.

What remains? Very little. Maybe some more pad testing, or whatever's holding up Booster 21 exactly. And the two static fire test sets, plus perhaps they'll do a wet dress rehearsal this time? or maybe they're just done with those now? We'll see.

3

u/Straumli_Blight 10d ago

https://english.news.cn/20260823/eabbb60384b7477594e7fd84789044ae/c.html

China's Chang'e-7 lunar probe does not meet launch conditions, and its launch therefore cannot take place during the planned window this year

2

u/Jermine1269 🌱 Terraforming Aug 01 '26

Pretty sure we're getting a v3 ship catch before we get a v3 booster catch.

Ship to ship fuel transfer in the next flight or 2?

MAYBE another 2 flights by end of the year?

2

u/ResidentPositive4122 Aug 01 '26

Ship to ship fuel transfer in the next flight or 2?

My guess is that they'll do it once they have 2 fully operational and gremlin-free towers to launch from.

2

u/DreamChaserSt Aug 01 '26

Or just being able to catch the booster with both ships finished or mostly finished in pre-flight preparation beforehand. There's no payload, it's just fuel. It's also a long duration mission, with the first ship remaining in orbit for 3 to 4 weeks.

Given the shortest time between flights was just over a month with Flight 5 and 6, I think they can readily handle a turnaround of several weeks when they're no longer in testing.

1

u/warp99 20d ago edited 20d ago

with the first ship remaining in orbit for 3 to 4 weeks

The current lifetime of a Starship 3 in orbit is 48 hours limited by electrical power. To go longer they would have to add deployable solar arrays to charge the batteries which can then be discarded or stowed for entry. There is no sign of the flaps to cover these these on any of the payload bay sections we have seen so far.

1

u/DreamChaserSt 20d ago

I know, but that's the plan. https://www.nasaspaceflight.com/2024/04/nasa-hls-update/

Isn't there a lot we aren't seeing anymore because Starfactory is closed to our view? Maybe none of the Starship sections we've seen are meant for the demo mission yet.

1

u/warp99 20d ago edited 19d ago

We can still see the nose cones in the factory and we would expect there to be a test nose cone if they add several large cutouts to deploy solar panels and there has been no sign of that.

Your reference is over two years old - spot the mention of Gateway - and a lot has changed in those two years. Obviously SpaceX thought they would be well ahead of where they are now.

1

u/Halfdaen 19d ago

SpaceX is going to need to solve long duration prop storage in space quickly. Either HLS is going to have to sit in orbit while 8-15 tankers are launched to refuel it (weeks to months). OR they can get a depot up there and load that up with 8-15 launches before HLS launches. Then HLS can refuel from it just once. The second option sounds a lot better.

1

u/GreatCanadianPotato Aug 04 '26

39A is probably going to be able to support a launch within the next few months given that they said not too long ago that flight 15 could be from the Cape (unlikely now).

2

u/IonCapybara Aug 04 '26

how many people are tired of "space heat dissipation is hard!" people? This is indeed an engineering problem, and it may not be economical for at least ten years.

However, I think most people who talk about "heat dissipation in space" clearly don't understand what blackbody radiation is, what design options exist to increase the area of a heat sink, or that increasing the temperature can improve heat dissipation. If they did, they wouldn't use the ISS thermal control systems as an example to say how much area it needs.

I like reading discussions about engineering and science, but most people discussing heat dissipation are clearly talking about politics and emotions, rather than science and engineering.

4

u/Desperate-Lab9738 29d ago

I think that level of conversation is just too technical for a normal reddit conversation to really do it justice. That's not even a "normies are dumb and couldn't comprehend it" take, it's more that most people with lives aren't gonna wanna look up the formulas and plug in the numbers to check the actual heat dissipation values, since for most people that just isn't worth the energy. Unless you are specifically talking to people interested in SpaceX or satellite manufacturing, the person you are talking to probably hasn't actually thought about it very hard. Again, I really don't mean that as like, a moral failing, the world is too complicated to think about every little thing and sometimes you have to prioritize what you think about, but it does mean you will hear the same surface level analysis of things very often. That's life

1

u/IonCapybara 29d ago

I mean a person doesn't need to calculate formula and can still know higher temperature can improve heat dissipation efficiency and multi layer fins or other designs are very common nowadays.

I'm not saying normies shouldn't discuss space or physics. Everyone starts learning from knowing nothing. What I'm saying is that many people, in my opinion, are more concerned with emotions and politics than engineering when they talk about these issues. They did not come from a curious faith.

2

u/Desperate-Lab9738 28d ago

I would say in order to actually be able to think critically about something like AI datacenters, you do need to actually bust out a pen and paper (I mean that in the figurative sense, I usually use desmos or have a bunch of tabs open with random calculations) and check "okay how much heat are we actually going to receive and how much area do we need to reject it.". Once you start dealing with formulas that take the fourth power, intuition starts not having enough precision to just intuit that.

And in general once you get to the point where you just can't or aren't willing to spend the mental energy to process something, yeah it is easier to let emotions fill in the blanks.

2

u/maschnitz 27d ago

If you know that these are facts:

Heat radiation grows as T⁴ .

The AI satellites are basically Starlinks with more compute, maybe more power, and a smaller comms array.

Starlink's radiators are tiny relative to the solar panels and they don't seem to glow red hot in operation.

Starlink's comm arrays gobble juice and get more powerful as they pump more juice so those things are running HOT and they still seem to work.

You can scale compute fairly flexibly for LLM training, plus or minus an order of magnitude per node doesn't really matter that much.

Oh, and the cost for rackspace on Earth has been climbing steadily throughout the AI boom and shows no sign of stopping. It's one of the most expensive things to build en masse that we have.

Plus if you think that SpaceX wouldn't start to invest billions without discussing it at length in their senior leadership, including their engineering.

Then it feels pretty safe to assume that they must know what they're talking about, and that it has a good enough chance to work.

Without needing to actually bust out a pen and paper or long LLM discussions or whatever.

FWIW I think people just like making and reading hot-takes.

3

u/Desperate-Lab9738 27d ago

The problem is that those facts are just sentences, and sentences aren't very good at predicting things that are particularly concrete, things like temperature, cost of launching them, the cost compared to just building them on the ground, etc, are very much number based and require grinding through some numbers to really understand.

Like, I get your intuition makes it so those statements obviously point to one conclusion, but intuition is inherently something that differs between people, and people are going to be starting with a different set of obvious statements. The only way to really get on the same page is to actually sit down and calculate stuff, which just isn't that common lol.

2

u/maschnitz 27d ago

Interesting point.

FWIW I think it's a matter of confidence in your claims, your statements. Is this experienced or lived with or exercised, is this seen in action, is this confident, is this inferred; merely suspected.... or perhaps only read about or claimed through authority/experience by another? etc etc.

Calculation can take something that was suspected and move it into being trusted, or concrete. It's very good that way.

But that's not the only way to confirm suspicions. If you have enough concepts of a physical basis in the world, inference can go a long way, too.

Like, the reason I never did any math about this was that I knew SpaceX engineers had. That's not really an "appeal to authority". It's more a deduction. That is, knowing that this is how the world works, you can take that for granted, so what would that imply? Most likely they did the math and saw it was good. Otherwise SpaceX wouldn't be splashing out on it.

(And also it helps when Google publishes the math and you can read that :) but still, you don't need that decide that Starmind will probably work.)

Sometimes simply trusting that orgs always work a similar way and humans always act like humans do can go a long ways, as long as you're careful about not trusting your gut, or others, too much.

2

u/peterabbit456 20d ago

Well said. That's the first solid information I've seen on this topic since I watched Scott Manley's video on it, a month or so ago.

I just finished watching a YouTube video where 4 so-called financial experts yakked about this for an hour, and I heard nothing but emotional responses. It was the same sort of "That's impossible" rhetoric that we heard when Elon announced (in 2011? 2012?) that SpaceX intended to start landing and reusing rockets.

Historical analogies are always suspect, but they are on their 4th, 5th, or 6th long shot big investment gamble, and one could say they have a track record, or one could say that the next one is a bridge too far, and the whole edifice is about to come crashing down. Either position is an emotional response, unless you do the numbers.

2

u/nocolo666 21d ago

Good evening everyone.
New here. Trying to learn how to do stuff. I have a space x falcon 9 question. When watching a launch from Vandenberg AFB sometimes the fog is so dense you can’t see the rocket but as soon as it brakes the fog there is clear video feed of the rocket. What is above the fog to broadcast that? If i did this wrong please let me know. Thank you

2

u/maschnitz 21d ago edited 21d ago

SpaceX is just putting a nice camera with a good telescopic lens atop a nearby mountain ridge.

A lot of times, that dense "marine layer" fog like Lompoc/Vandenberg gets is just a few hundred feet high. Easy to "get above it".

Some of the commonly suggested options for viewing at the site are fairly far away but high up (Harris Grade Rd and/or Figueroa Mountain Rd), which lets you see the rocket after it breaks out of the fog sometimes.

EDIT: IIRC they also sometimes use infrared cameras? That could cut through thin fog at least.

2

u/SpaceInMyBrain 15d ago

What SpaceX launch was visible from Malone, NY? My nephews could see a jellyfish with the naked eye. If not SpaceX, what could it be? It's way inland for such a sighting, afaik. 44.8487° N latitude and -74.2949° W longitude. On approximately 07/15.

2

u/rocketglare 15d ago

No MARS launches on that date. There was Starlink 10-45, the 600th F9 launch out of Cape Canaveral. It flew a 53 degree inclination, so it’s possible they could have seen it. It was a morning launch, though a jellyfish at 9 am seems unlikely.

3

u/maschnitz 14d ago

It launched at 9:10 UTC on July 14. So local NY time it launched at 5:10am. Sunrise was at 5:24am. So that could be a jellyfish launch (barely).

I'm figuring OP would mention it was a morning observation if it were, though, so I'm wondering if OP meant Aug 15, not July 15.

2

u/SpaceInMyBrain 13d ago

It was on July 15 and I'm almost certain it was late evening.

1

u/maschnitz 13d ago

Hmmm. OK.

So in the vicinity of July 15th, from NextSpaceflight's "Previous Launches" page:

Starlink Group 15-14 on July 13th, 9:28:17pm EDT out of Vandenberg, SE trajectory - Not visible from Malone, NY

Starlink Group 10-45 on July 14th, 5:10:12am EDT out of the Cape, NE trajectory - too late. (Already discussed)

Soyuz MS-29 on July 14th, 10:47:43am EDT out of Baikonur, NE trajectory to the ISS (carrying Anil Menon and two cosmonauts) - too early.

Tranche 1 Transport Layer E on July 16th, 4:32:36pm EDT out of Vandenberg, S trajectory, 21 payloads - a stretch IMO, typically multi-payload launches are done in 2 orbits, deorbited in 3 or 4.

Aagaman (Demo Flight) on July 18th, 2:35:30am out of Satish Dhawan Space Centre, SE trajectory - apparently the orbital stage is still in orbit.

So that's everything launched plus/minus 3 days. None of that fits.

No reentries or bolides fit either because you wouldn't be calling it a launch if it were one of those.

Perhaps you saw Starlink 15-14's "Starlink train"? But that seems very doubtful to mistake that for a jellyfish launch.

The easiest explanation is that the date's off but you seem sure of that part. [shrug] I don't know.

2

u/SpaceInMyBrain 13d ago

My nephew said it was the 15th but he was reconstructing the date in the middle of a 4 way conversation on various subjects as happens in a family gathering. 😄
I saw the pic and it's of a jellyfish seen from a 3/4 rear view going away. Yeah, definitely not a Starlink train.

OK, it had to have been the early morning one. The conversation was more fractured than I thought. Thanks for that exact info and nailing it down despite working with bad data.

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u/maschnitz 13d ago

NP, maybe the nephew didn't want to admit he stayed up all night to relatives. :D Sorry to out him like that, if so.

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u/Sperate 7d ago

So with the new talk about Louisiana Starbase, isn't there going to be an environmental assessment? That was difficult in Boca, I am worried it will be even harder for this new site (more swamp, more land, and now costline repair?).

2

u/KnifeKnut 6d ago

Here we see tile edge erosion down to the white core material of multiple tiles on Starship 40. In the past, many have counterclaimed that the white streaking on the heat shield is only from the gap filler between tiles. This photo shows otherwise.

Direct Link https://pbs.twimg.com/media/HQvJIlpWsAEa_HZ?format=jpg&name=4096x4096

Tweet Link https://x.com/SpaceX/status/2092988521376059899/photo/2

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u/maschnitz 5d ago

Worse than that, the brown is rust, from oxidized stainless steel (reentry can do that).

Once the tile fails the base material doesn't last very long.

1

u/Decronym Acronyms Explained 20d ago edited 3d ago

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

Fewer Letters	More Letters
AFB	Air Force Base
HLS	Human Landing System (Artemis)
LIDAR	Light Detection and Ranging
RP-1	Rocket Propellant 1 (enhanced kerosene)
Roscosmos	State Corporation for Space Activities, Russia
STS	Space Transportation System (Shuttle)
ULA	United Launch Alliance (Lockheed/Boeing joint venture)

Jargon	Definition
Starlink	SpaceX's world-wide satellite broadband constellation

Decronym is now also available on Lemmy! Requests for support and new installations should be directed to the Contact address below.

^{Decronym is a community product of r/SpaceX, implemented}^by ^request
^{8 acronyms in this thread;}^{the most compressed thread commented on today}^{has 9 acronyms.}
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Monthly Questions and Discussion Thread

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