Starship Asterisk*

Sorry, that's all I know about De Laval nozzles, supersonic flow, and fluid dynamics. Good luck!

Wow thanks! A key word really opened an Alice-like rabbit hole. As an amateur, I find the literature about this stuff is somewhat limited and hard for outsiders to grasp with many big words thrown around. I have more questions reading it than getting answers. From my very basic understanding, the word 'shock' and 'Mach' implies "waves moving faster than sound speed", and since this is a rocket, supersonic is a given. Because the diamonds are quite fixed relative to the nozzle, there might be some standing waves involved. The big-small-big-small pattern of the flow kinda confirms this one. But that's where my understanding ends. Now the questions:
1. Standing waves usually require at least 2 interacting waves. In single-nozzle cases (not Terran, but normal aircraft), what are the waves?
2. In this [url=https://qr.ae/prQZr1]Quora answer[/url] about CD nozzles, it is stated that "For subsonic flow, as the flow area gets smaller, the flow velocity goes up, and for supersonic flow, as the flow area gets larger, the flow velocity goes up." Huh? Why is that? What's so magical about the 'sonic' threshold that it can apparently reverse a physical principle?
3. Unlike many pictures of Mach diamonds which have the diamonds persist until near the end of the exhaust, Terran's only had about 2 layers of them. Does that mean the standing waves were broken down the line? What caused the turbulence in this case? The nozzles formation?
4. I had troubles following a [url=https://www.youtube.com/watch?v=bmLJq5aPBqc]YouTube explanation[/url] of the phenomenon, which has illustrations alright. So maybe I'll need someone else with a better skill at ELI5 to drill it into my head. Who do you think will be a good candidate? IMO Steve Mould is really good at making hard stuff easier to understand, but his favorite method is to build 2D versions of things, which perhaps won't be suitable for this kind of problem...?
In any cases, I did go ogle the beauty of it all :wink:

[quote=longtry post_id=330255 time=1680833182 user_id=144549]
I'm interested in the shapes under the nozzles. How did they form such specific shapes? Illustration-included answers will be much appreciated.
[/quote]
Go ogle "shock diamonds". Wikipedia for one has a nice explanation.

I'm interested in the shapes under the nozzles. How did they form such specific shapes? Illustration-included answers will be much appreciated.

In Mars' low gravity carbon monoxide + LOX is a perfectly adequate propellant system. There, it's easier to make carbon monoxide than methane because no hydrogen or complicated chemistry is needed. I expect that anyone intending to return from Mars will be testing their engines for burning CO.

[quote="John The Old Tex Guy" post_id=330248 time=1680796464]
Serious question - how much CO2 is created in one such launch?
[/quote]

The combustion of 1 kg of methane produces 2.75 kg of CO[sub]2[/sub]. So the short answer is "a lot". But it's quite a small amount compared with, say, commercial aviation, which itself is a fairly small part of the human carbon footprint. It's likely that the soot released in the upper atmosphere is the more serious environmental issue with rockets, and that's actually much lower for methane powered motors. Also, methane can be sourced from biological materials, which eliminates the problem of fossil fuel CO[sub]2[/sub].

[attachment=0]2023-03-22_Terran-1-GLHF_Kraus_thumb.jpg[/attachment]
Mmm; mm; mm! Looks hot, hot, hot!

Serious question - how much CO2 is created in one such launch?

[quote=De58te post_id=330243 time=1680780303 user_id=141631]
This is a coincidence. Although no where near as bright or severe, I get the occasional blue flash like that out of my propane fork lift. I guess it needs a tune-up. It burns gaseous propane. (But I guess that is cryogenic as well because if you don't tighten the connecting hose line properly the leaking propane quickly covers the metal connector with a freezing white frost. Don't touch it with bare hands since it will give your skin a cold burn! You need thick leather gloves to tighten it!

The gaseous oxygen it burns with the propane I imagine is always room temperature though.
[/quote]

Propane is not cryogenic in consumer applications. Like any compressed gas, if it leaks too quickly the expanding gas can cool enough to locally condense and freeze water vapor in the surrounding air (seen as frozen fog) or cool the element that is leaking (seen as accumulating ice). Cryogenic gases are actively refrigerated.

Methane or propane that burns efficiently produces a blue flame. An orange flame indicated incomplete combustion.

This is a coincidence. Although no where near as bright or severe, I get the occasional blue flash like that out of my propane fork lift. I guess it needs a tune-up. It burns gaseous propane. (But I guess that is cryogenic as well because if you don't tighten the connecting hose line properly the leaking propane quickly covers the metal connector with a freezing white frost. Don't touch it with bare hands since it will give your skin a cold burn! You need thick leather gloves to tighten it!

The gaseous oxygen it burns with the propane I imagine is always room temperature though.

Cool, literally!

[img3="Terran 1 Burns Methalox
Image Credit: Relativity / John Kraus"]https://apod.nasa.gov/apod/image/2304/2023-03-22_Terran-1-GLHF_Kraus_thumb.jpg[/img3]


Welllll.... Lotsa blue here! :shock:

I think I like it! :D

What else can I say? :?:

Ann

[url=https://apod.nasa.gov/apod/ap230406.html] [img]https://apod.nasa.gov/apod/calendar/S_230406.jpg[/img] [size=150]Terran 1 Burns Methalox[/size][/url]

[b] Explanation: [/b] [url=https://www.relativityspace.com/rockets]Relativity's Terran 1 Rocket[/url] is mostly 3D-printed. It burns a cryogenic rocket fuel composed of liquid methane and liquid oxygen (methalox). In this close-up of a [url=https://www.relativityspace.com/]Terran 1 launch[/url] on the night of March 22 from Cape Canaveral, icy chunks fall through the stunning frame as intense blue exhaust streams from its nine Aeon 1 engines. In a largely successful flight [url=https://www.universetoday.com/160699/success-and-failure-relativity-space-launches-its-terran-1-but-the-rocket-fails-to-reach-orbit-however-the-launch-photos-are-incredible/]the inovative rocket achieved[/url] main engine cutoff and stage separation but fell short of orbit after an anomaly at the beginning of its second stage flight. Of course this Terran 1 rocket was never intended to [url=https://mars.nasa.gov/]travel to Mars[/url]. Still, the methane and liquid oxygen components of its [url=https://en.wikipedia.org/wiki/Liquid_rocket_propellant#Methane]methalox fuel[/url] can be made solely from materials found on the Red Planet. [url=https://www.nasa.gov/centers/marshall/news/releases/2015/nasa-tests-methane-powered-engine-components-for-next-generation-landers.html]Methalox[/url] manufactured on Mars could be used as fuel for rockets returning to planet Earth.


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