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How to start a rocket engine

everydayastronaut.com

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Re: How to start a rocket engine

#21

Post by fnordpiglet »

sbradford26 wrote: post #19
EvanAnderson wrote: post #13

Earlier quoted context omitted.

All the imperial units in this PDF hurt my head. I'm an American, so I'm used to them, but seeing them in the context of precision aerospace hardware is so jarring. As a student it seemed like math re: chemistry and physics was so much easier (read: less error-prone) with metric units than with imperial. Mars Climate Orbiter indeed.

The biggest lessons learned on the Mars Climate Orbiter wasn't exactly that everything should be metric. It was the unit conversion is dangerous and needs to be handled very carefully. Just saying everything will be metric doesn't avoid unit conversion. You might have one thing measuring fuel burn rate in grams/second and another in kg/second. That conversion can still lead to issues if not handled correctly. In the…

I mean what issues would power of 10 fractions have in floating point after all?

Re: How to start a rocket engine

#22

Post by fnordpiglet »

This is great. My rocket starting experiences extend to hitting space in KSP and mashing the red button on an Estes launcher. To be fair in KSP they often wiggle to death on the pad and I’ve spent more time with bored 6 year olds wandering off as I figure out why the Estes motor didn’t ignite, but that’s nothing compared to this.

Re: How to start a rocket engine

#23

Post by lhoff »

ragebol wrote: post #2

I could watch stuff like this all day. Tim's stuff is so great. Easy to be jealous of, since being YouTuber seems easy, but to make quality content, it really can't be. And then he's going around the moon, it's really mind blowing to see the success he's had. His interviews with Musk are a treasure trove as well, whatever you think of Musk.

He recently was a guest in Lex Fridmans podcast.

https://lexfridman.com/tim-dodd/

Re: How to start a rocket engine

#24

Post by somenameforme »

MichaelZuo wrote: post #14
localplume wrote: post #5

Earlier quoted context omitted.

He, like most big Youtubers, probably have a large crew of people working with them. The article was written by Trevor Sesnic, the video was likely edited by others, I don't know if he did the graphics, but Tim still did a lot (and arguably did the most fun stuff). Smaller Youtubers need to do all of that, and from what I've heard editing is the absolute worst given how time consuming it is. Many Youtubers struggle w…

From the about page: > In 2019 the team grew from just Tim to a small army of incredible helpers who make this website amazing, the videos higher quality, and help foster a fun and positive online community. So the 2017-2019 period where the channel took off was all done by him solo, apparently.

I'd also add this standard. Another amazing YouTuber is Veritasium. He went from [1] to [2]. The production quality is more than slightly improved, but the "spirit" remains identical. And I think that spirit is what drives success or failure. The production quality is just icing.

[1] - https://www.youtube.com/watch?v=JUJPyQtoB5E

[2] - https://www.youtube.com/watch?v=5eW6Eagr9XA

Re: How to start a rocket engine

#25

Post by prox »

ragebol wrote: post #9
samwillis wrote: post #3

Earlier quoted context omitted.

> His interviews with Musk are a treasure trove as well, whatever you think of Musk. My main take away from those interviews is just how knowledgable Tim is, he's able to engage in low level and in depth conversations about how these engines work. It's not just superficial high level knowledge from making videos, he is thinking himself how to optimise and improve these things, and leading that conversation. The passi…

Absolutely. Imagine if all journalists had this level of depth in all of the topic they covered? I don't think that's possible though.

I agree. You need that intersection of interest, presentable qualities (listening, digesting,responding, speaking) and quest for accuracy. Hard to get those all in one person.

Re: How to start a rocket engine

#26

Post by Retric »

somenameforme wrote: post #24
MichaelZuo wrote: post #14

Earlier quoted context omitted.

From the about page: > In 2019 the team grew from just Tim to a small army of incredible helpers who make this website amazing, the videos higher quality, and help foster a fun and positive online community. So the 2017-2019 period where the channel took off was all done by him solo, apparently.

I'd also add this standard. Another amazing YouTuber is Veritasium. He went from [1] to [2]. The production quality is more than slightly improved, but the "spirit" remains identical. And I think that spirit is what drives success or failure. The production quality is just icing. [1] - https://www.youtube.com/watch?v=JUJPyQtoB5E [2] - https://www.youtube.com/watch?v=5eW6Eagr9XA

Veritasium videos are often subtly misleading which really annoys me.

It’s great for views, but terrible for science education.

Re: How to start a rocket engine

#27

Post by somenameforme »

HPsquared wrote: post #11

Space shuttle main engines (RS-25) had a very complicated startup process, deviations from this could cause all sorts of different things to fail catastrophically. http://large.stanford.edu/courses/2011/ph240/nguyen1/docs/SS... Slide 94 (pdf page 100)

I feel like this is a subtle jab pretty much nobody outside of serious aerospace enthusiasts is going to get. For those who don't know, right now there's sort of a competition for the 'next big thing' in rockets. Congress/Boeing/Lockheed have been working on the SLS or Space Launch System since 2011. It was expected to launch in 2016. It had its first trial launch in 2022, and is tens of billions of dollars over budget.

It's also expected to cost billions of dollars per launch. Its more common nickname is the Senate Launch System, since it's largely just a really big pork project. It's already not especially competitive against the Falcon Heavy, and is being built at the same time SpaceX Starship is also being built. That project began in 2017, is being completely privately funded, and expected to revolutionize spaceflight once again - with costs potentially as low as $1 million per launch.

Anyhow, the SLS is reusing a bunch of old technology from the Space Shuttle. This includes the RS-25 engines...

[1] - https://en.wikipedia.org/wiki/Space_Launch_System

Re: How to start a rocket engine

#28

Post by chasd00 »

I think there was a russian engine that literally had 2x4's on fire stuck in the combustion chamber in place of torch ignitors or TEAB.

If anyone's interested the experimental high-power rocketry hobby is pretty fun, there's a lot to learn and hack on. A lot of people focus on propulsion and formulating, profiling, and flying various solid fuels they develop themselves. This guy is highly regarded https://www.nakka-rocketry.net/

Others focus on flight controllers, GPS trackers, and other electronics. https://altusmetrum.org/ (i think one of the two owners of altusmetrum is a pretty famous Debian Linux guy from back in the day)

There's also "hybrid" engines that use a solid fuel and a liquid oxidizer ( nitrous oxide ). Ex, this guy is probably the most well known in the hybrids side of the hobby https://contrailrockets.com/

Finally, there's the halfcat guys https://www.halfcatrocketry.com/ who do amateur liquid bi-prop engines in an approachable way. I've working on a design of my own based on their designs and plan to do a static fire in the Fall and hopefully a flight before end of year. The downside with liquid engines in the hobby is governing bodies Tripoli and NAR don't allow these engines at sanctioned launches. You either have to launch privately (including coordinating/paperwork with the FAA on your own ) or at FAR https://friendsofamateurrocketry.org/

Re: How to start a rocket engine

#29

Post by bryanlarsen »

Koshkin wrote: post #16

Starting the engine(s) even in a propeller-driven airplane used to be a big deal, too. Hell, I'm sure that even starting a car engine back in the day was a much more complex affair (than simply pushing a button like it is today).

Check out a video on how to start a model T. It was a two man job: one on the inside fiddling with spark timing, the other on the outside cranking it over. Often you also need a bit of priming (aka choke).

Re: How to start a rocket engine

#30

Post by perilunar »

Koshkin wrote: post #15
EvanAnderson wrote: post #13

Earlier quoted context omitted.

All the imperial units in this PDF hurt my head. I'm an American, so I'm used to them, but seeing them in the context of precision aerospace hardware is so jarring. As a student it seemed like math re: chemistry and physics was so much easier (read: less error-prone) with metric units than with imperial. Mars Climate Orbiter indeed.

I mean, sure, converting grams to kilograms is easier (for a human) than converting ounces to pounds, but how often do we have to do that in our heads? Computers, on the other hand, do not care (and they "prefer" the binary system anyway).

Converting grams to kilograms not so much, but mm to m, mL to L, even g to mL and L to kg (of water) — all the time, and of course in our heads — it's so easy you barely need to think about it.
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