totm nov 2023 SpaceX Discussion Thread

[Cunjo Carl]

1 minute ago, Rakaydos said:

Interesting! With how bright the best case is, I wonder if reflection just off the curve of the nose would be visible at night. Also, how much dimmer would a moonlight reflection be?

The nose is an interesting question! It's more complicated, so I ignored it . Moonlight reflection is also interesting. Since the moon fills the same area in the sky as the sun, and is about 14 magnitude dimmer, that would put its reflection at magnitude ~ 5, which would be just barely visible if you're far away from cities. Again, lots of uncertainty, so YMMV!

[CatastrophicFailure]

26 minutes ago, Cunjo Carl said:

Let's hope the SpaceX execs are the sort of people who like to put on a show on occasion

If heat rejection is the goal, rather than a “barbecue roll” like Apollo, etc, would it not actually be better to keep the shiny side pointed at the sun, reflecting most of that heat away? Engines to the sun seems more like a deep-space thing to reduce radiation exposure. 

[Cunjo Carl]

2 minutes ago, CatastrophicFailure said:

If heat rejection is the goal, rather than a “barbecue roll” like Apollo, etc, would it not actually be better to keep the shiny side pointed at the sun, reflecting most of that heat away? Engines to the sun seems more like a deep-space thing to reduce radiation exposure. 

My rationale was that there's a big thermal resistance between the engines and the fuel tanks. So, despite the engines absorbing much more sunlight they'd also radiate almost all of the energy away as heat rather than letting it pass to the fuel. Meanwhile, the walls of the starship will reflect most light away, but what they do absorb will probably have a very low thermal-resistance direct path of metal the fuel tanks (because of how the ship is designed for anti-buckling). Totally just a guess!

I haven't heard of the barbeque roll, I'll go look it up!

[Xd the great]

56 minutes ago, CatastrophicFailure said:

If heat rejection is the goal, rather than a “barbecue roll” like Apollo, etc, would it not actually be better to keep the shiny side pointed at the sun, reflecting most of that heat away? Engines to the sun seems more like a deep-space thing to reduce radiation exposure. 

I think the main point is to keep the solar panels pointed at the Sun, not thermal testing.

Starship is so huge, thermal control can be ignored.

[magnemoe]

2 hours ago, Xd the great said:

I think the main point is to keep the solar panels pointed at the Sun, not thermal testing.

Starship is so huge, thermal control can be ignored.

However it hold cryogenic fuel, granted insulated but still. One issue with engines towards the sun might be heat leak from engines up the piping and into the heater tanks heating them up. 
If side is exposed to the sun it will be 1-2 meter vacuum between the outer skin and the header tank.
Engine towards the sun will give better protection against radiation from the sun as the structure, engines fuel and oxygen will provide some shielding not only the walls to the crew compartment. 

[tater]

South Padre guys set up a remote camera livestream.

 

 

Maybe not a remote, they might have to pull it at some point.

[kerbiloid]

Spoiler

A sleepy, idyllic rocket farm. 

 

[Cunjo Carl]

It's a page back, so I figured I'd also post here, I missed a factor of 2 on the angle of the Starship cylinder that would be reflecting to the viewer. It should be 2 * 4.5m * sin(0.53deg / 4) making a 2cm strip (half the light). Updating, that puts the brightness at .0048 lx, and the magnitude at -8.1 . Still bright enough to be a show, but not quite as impressive! The astronomers will probably be happier at any rate

Sorry all!

[ThatGuyWithALongUsername]

Starhopper preburner test (run gas through engine, but don't ignite) does seem to have occurred today.

 

Spent 6 hours waiting for this on a webcam, and of course I left JUST in time to miss it... of course.

 

 

[Xd the great]

1 hour ago, ThatGuyWithALongUsername said:

Starhopper preburner test (run gas through engine, but don't ignite) does seem to have occurred today.

 

Spent 6 hours waiting for this on a webcam, and of course I left JUST in time to miss it... of course.

 

 

How do they make sure the engine does not blow with all the methane oxygen mixture?

[tater]

 

[ThatGuyWithALongUsername]

1 hour ago, Xd the great said:

How do they make sure the engine does not blow with all the methane oxygen mixture?

 

Well, it would have to be ignited first- unless it's hyperbolic, rocket fuel do not combust when touching- they need something to set them ablaze. Just leave that out, and you get this. 

 

That being said, there is still a danger of something going wrong and the reaction occurring anyway. that's why they clear the site off.

 

58 minutes ago, tater said:

 

So, the timeline STILL hasn't shifted much. Interesting. If this means sending the first cargo ships in 2024 (a delay that was hinted at earlier), then they have quite a busy few years ahead indeed.

 

Here are the bits of the current schedule we know of:

• 2019: Much hopping (first low-altitude, then high-altitude reentry tests)
• 2020: Possible first orbital launch
• 2021-2022: ??? (Probably plenty of Starlink flights to ensure reliability and test flight of crewed variant?)
• 2023: ARTISTS... IIINNN... SPAAAAAACE! (around the Moon, specifically)
• 2024: Mars cargo ships
• 2025: Moon landing / moon base
• 2026: Mars crewed missions (!)
• 2029-2050: Apparently more mars crewed missions, creating self-sustaining base

Of course, MAJOR Elon time shenanigans, I'm sure.

[cubinator]

Quote

It’s possible to make a self-sustaining city on Mars by 2050, if we start in 5 years & take 10 orbital synchronizations

Ok, ok, so...100,000 people per transfer window for a population of 1,000,000? That's 1,000 ships each window. Although he did say "city", not "entire planet".

[ThatGuyWithALongUsername]

2 minutes ago, cubinator said:

Ok, ok, so...100,000 people per transfer window for a population of 1,000,000? That's 1,000 ships each window. Although he did say "city", not "entire planet".

Maybe a population of, say, 100,000 people could work. 100 ships  per window is still a lot, but with P2P-level frequency it would be doable (although remember, each launch is actually more like 5 launches since you have to refuel).

[cubinator]

7 minutes ago, ThatGuyWithALongUsername said:

Maybe a population of, say, 100,000 people could work. 100 ships  per window is still a lot, but with P2P-level frequency it would be doable (although remember, each launch is actually more like 5 launches since you have to refuel).

I anticipate it'll take them at least a decade after the first operational flight to ramp up to that kind of efficiency.

[Xd the great]

3 hours ago, ThatGuyWithALongUsername said:

So, the timeline STILL hasn't shifted much. Interesting. If this means sending the first cargo ships in 2024 (a delay that was hinted at earlier), then they have quite a busy few years ahead indeed.

 

Here are the bits of the current schedule we know of:

• 2019: Much hopping (first low-altitude, then high-altitude reentry tests)
• 2020: Possible first orbital launch
• 2021-2022: ??? (Probably plenty of Starlink flights to ensure reliability and test flight of crewed variant?)
• 2023: ARTISTS... IIINNN... SPAAAAAACE! (around the Moon, specifically)
• 2024: Mars cargo ships
• 2025: Moon landing / moon base
• 2026: Mars crewed missions (!)
• 2029-2050: Apparently more mars crewed missions, creating self-sustaining base

Of course, MAJOR Elon time shenanigans, I'm sure.

Yeah, like 2X more time required.

[Bill Phil]

4 hours ago, cubinator said:

Ok, ok, so...100,000 people per transfer window for a population of 1,000,000? That's 1,000 ships each window. Although he did say "city", not "entire planet".

Well if we’re talking 1 million people 50 years after start of project and 25 years of launches plus 5 years to establish launch infrastructure we have 20 years of population growth on top of that. Probably slow growth (it is on Mars) but 1% doesn’t seem too unreasonable.

Doing some quick math shows that for 1 million at 50 years there needs to be about 820k at 30 years. 

Taking it to an extreme... with 1% population growth and constant immigration you only need about 28000 arriving per year, or about 70k per synod. And assuming immigration stops at year 30 (after project start) then if population growth is the same it’ll hit 1 million at year 50, probably a tad bit before.

Of course any population growth at all on Mars would be a heck of an achievement.

[hms_warrior]

Well even if it's only a 1000 People it could still call itselfe a city. And even the capital of mars!

[Xd the great]

1 hour ago, Bill Phil said:

Well if we’re talking 1 million people 50 years after start of project and 25 years of launches plus 5 years to establish launch infrastructure we have 20 years of population growth on top of that. Probably slow growth (it is on Mars) but 1% doesn’t seem too unreasonable.

Doing some quick math shows that for 1 million at 50 years there needs to be about 820k at 30 years. 

Taking it to an extreme... with 1% population growth and constant immigration you only need about 28000 arriving per year, or about 70k per synod. And assuming immigration stops at year 30 (after project start) then if population growth is the same it’ll hit 1 million at year 50, probably a tad bit before.

Of course any population growth at all on Mars would be a heck of an achievement.

We need to solve the problem of reproduction miles from Earth.

[sh1pman]

36 minutes ago, Xd the great said:

We need to solve the problem of reproduction miles from Earth.

Is there a problem?

[MaverickSawyer]

42 minutes ago, sh1pman said:

Is there a problem?

That's just it: We don't know how safe a pregnancy is offworld. It's a huge gamble with the life of both mother and child.

[Xd the great]

1 hour ago, sh1pman said:

Is there a problem?

 

1 hour ago, MaverickSawyer said:

That's just it: We don't know how safe a pregnancy is offworld. It's a huge gamble with the life of both mother and child.

And we have to deal with vaccination (not a problem for anti-vaxxers), blood donation, medicine production.

On the topic of medicine on Mars, cancer treatment is easy, just go sunbathing.

Edited March 26, 2019 by Xd the great

[insert_name]

On 3/24/2019 at 7:27 PM, Xd the great said:

I think the main point is to keep the solar panels pointed at the Sun, not thermal testing.

Starship is so huge, thermal control can be ignored.

Tell that to Laika

[mikegarrison]

On 3/24/2019 at 7:27 PM, Xd the great said:

Starship is so huge, thermal control can be ignored.

Wait, what? I mean, the Earth is really huge, but you are aware that we are currently concerned about whether we have messed up our thermal control system. And Venus is really huge, but it has a bit of a problem with thermal control.

The bigger a spaceship is, typically, the higher the mass/area ratio will be, so the thermal effects will happen slower. But they will still happen. If the ship absorbs more heat than it radiates, it will still get hot. It will just take a little longer.

[tater]

Yeah, Starship will also need radiators. That or the thermal control for reentry can also be used. If they have a system to circulate cryos between skin layers, maybe they use that.