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How to start a rocket engine

everydayastronaut.com

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Re: How to start a rocket engine

#71

Post by sho_hn »

LargeTomato wrote: post #62
ghostpepper wrote: post #52

Earlier quoted context omitted.

Didn't he suggest something to Elon that Elon immediately decided to alter on an upcoming rocket? Doesn't sound like he knows nothing..

I forget exactly what he suggested but I remember is being like kind of dumb. Elon was humoring him. This guy is absolutely not a rocket scientist. He's not even an engineer.

If I recall, Musk was explaining that on the Starship booster they had recently begun to use directed venting of ullage gases for control authority to save a seperate hot or cold gas thruster system and Dodd asked if this also applies to the ship. Musk then went "now that you mention it, we should look into that". During a visit a year or so later he then confirmed they had begun doing it on the ship too and that it had occurred to him as he was explaining it to Dodd.

It's of course unlikely that the engineering team wasn't already considering this, but it's also not like Dodd was suggesting anything, he was just asking a follow-up question. The way the conversations played out was Musk remembering to ask someone about it later to check the status of the plan or drive a decision, and later recalling that conversation when Dodd came by again.

Re: How to start a rocket engine

#72

Post by twic »

LargeTomato wrote: post #62
ghostpepper wrote: post #52

Earlier quoted context omitted.

Didn't he suggest something to Elon that Elon immediately decided to alter on an upcoming rocket? Doesn't sound like he knows nothing..

I forget exactly what he suggested but I remember is being like kind of dumb. Elon was humoring him. This guy is absolutely not a rocket scientist. He's not even an engineer.

Something about cold gas thrusters? https://www.ladbible.com/news/elon-musk-fixes-rocket-after-y...

Re: How to start a rocket engine

#73

Post by polishdude20 »

skazazes wrote: post #59
chasd00 wrote: post #28

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-r…

You probably already know of him, but you should check out BPS Space on youtube if you enjoy long-form video edutainment. Much like Tim Dodd, Joe makes videos full of detail and information about topics he is clearly passionate about. In the case of BPS Space that is pushing the limits of amateur rocketry in a uniquely hacker/programmer friendly manor.

BPS Space is what got me into building my own thrust vectoring rocket during COVID lockdowns.

https://github.com/AdamMarciniak/CygnusX1

It was super fun to bring together lots of different disciplines and skills. 3D printing, software, soldering, circuit design, simulation etc.

Ultimately, I got so obsessed with it I got burned out and had to take a break for a bit but came back fresh and finished it. Did a few flights over the year with more and more interesting things culminating in a dual stage flight. I've still got the rocket ready to go anytime. Just gotta wait for the weather to clear up.

Re: How to start a rocket engine

#74

Post by apendleton »

LargeTomato wrote: post #50

I'm surprised at the amount of people who enjoy EDA. I find him very irritating. Most people at my small space company find him extremely irritating. He is not a rocket scientist. He parrots silly buzzwords like "biomimickry" like a fanboy, not an engineer. He suggests things to Elon for how to do rockets that are just pants-on-head dumb. His blind fanboyism and arrogance irritate so many people who work in space. I'…

With respect, you and your company of people who are already subject matter experts are not his audience; his audience is people who are not experts and want to learn about this subject matter. Most people on HN are also not subject matter experts with respect to rockets, so in that respect, are probably much closer to his target audience on average than you are.

> He is not a rocket scientist.

That might well be a pro, not a con. Rocket scientists' core competency is designing rockets, not teaching, and subject matter experts often make poor teachers. If this were a case of some kind of hucksterism, where he's an ignorant layperson making shit up and passing it off as true in his educational content, I'd say there was some concern, but while he's apparently said some dumb shit on Twitter, it doesn't seem like you or most other commenters are pointing to anything factually inaccurate _in this article_, nor indeed do people tend to on his researched, long-form stuff generally (vs. some off-the-cuff tweet). In that sense, it seems like this content is as good a place as any for laypeople to learn about this topic, that it doesn't obviously suffer from his lack of formal training, and maybe benefits if it means his better able to translate technical content to non-technical audiences.

Re: How to start a rocket engine

#75

Post by bewaretheirs »

chasd00 wrote: post #28

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-r…

Yes, the Soyuz (the workhorse Soviet/Russian launcher for crew, smaller satellites, and space station cargo) is ignited that way (and it's mentioned at the Everyday Astronaut page linked above, just under the "Ignition on the Ground" heading). There are pyros on top of the wood, so it's really just a really large electrically ignited match.

IIRC the Soyuz family have five ground-start engines (propellant pump sets) which feed a total of 20 main and 12 steering combustion chambers across the center core and 4 boosters, so they need to light 32 of them for each launch.

Multiple combustion chambers per engine was their way to mitigate combustion instability; Rocketdyne blew up a lot of engines before they figured out a different approach (involving baffles on the injector plate) in the Saturn V's F1 engine.

Re: How to start a rocket engine

#76

Post by sbradford26 »

numpad0 wrote: post #58
sbradford26 wrote: post #43

Earlier quoted context omitted.

When designing new systems it is best to clearly define the expected units for everything clearly at the start. SI units are great but sometimes they are not great for the specific use case. When measuring high power systems like power plants or EVs kW/MW/GW are a more appropriate unit versus Watts. In embedded systems you have limited bandwidth having to have large variables just to store values in SI units is a was…

INT_MAX is usually 2147483648, which means a "power" figure in Watt can handle anything from a laptop CPU to a Chernobyl power plant. FLT_MAX and _MIN are e+38 and e-38 so couple digits over and under(within 32bit precision). Have you actually had that kind of unit confusion in metric, or inferring from your experience with Imperial system? It kind of just seems to reinforce suggestion that Imperial system having bun…

INT_MAX is assuming every variable is using a 32 bit integer which is not always the case. In my experience with flight control systems controls systems were focused on using the smallest variable necessary for a given variable. We had many variables that were only 8 or 16 bits. The processing overhead wasn't really the driving factor for smaller variables it was typically interface bandwidth which can be very limited while maintaining required safety margins on aircraft.

We had a pretty massive ICD that defined every message going in between sub systems down to the bit level which is what was necessary to avoid unit confusion when dealing with system creates by sub contractors and such. Your example of velocity is pretty common thing that you would have to reference the ICD for. Is this velocity signal in KM/h or m/s, as well as MPH, fps, and Mach number.

Sure you could say all velocities need to be in m/s, but then if all your control laws for higher speeds which have been fined tuned through 10s of years of work utilize Mach Number in the calculations is it safer to update all the controls laws or just do a conversion?

Re: How to start a rocket engine

#77

Post by speed_spread »

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.

> whatever you think of Musk

Musk is a clown but I'll give him one thing: he cares about technology. That's something that very few modern CEO in big tech have and probably gives him the edge in making his project successful.

Re: How to start a rocket engine

#78

Post by LargeTomato »

sho_hn wrote: post #65
LargeTomato wrote: post #50

I'm surprised at the amount of people who enjoy EDA. I find him very irritating. Most people at my small space company find him extremely irritating. He is not a rocket scientist. He parrots silly buzzwords like "biomimickry" like a fanboy, not an engineer. He suggests things to Elon for how to do rockets that are just pants-on-head dumb. His blind fanboyism and arrogance irritate so many people who work in space. I'…

Could you give me an example of his 'arrogance'? I've been watching his content for some time, and I'd say he's always been very upfront and transparent about being an enthusiast/fanboy and not an engineer. His concept is to be an audience insert and ask the stuff his non-professional audience would ask, as a sort of avatar. I would expect no more expertise from him than from myself. If the people he interviews are h…

I can't find the tweet where he suggests to Elon how to design the sides of the rocket. Elon just shuts it down. I've never once heard EDA push back on anything Elon says even though Elon can say some outlandish things every now and then. That blind fanboyism is annoying.

While not public, my friend was his liaison at Blue origin when he toured. He was extremely rude to the team at Blue. It actually surprised the media team how condescending he was.

In my personal experience, most people at my company don't like EDA. On the other hand they love Scott Manley. It's not about what you know it's about what kind of person you are.

Re: How to start a rocket engine

#79

Post by jaywalk »

chasd00 wrote: post #28

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-r…

> 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.

Yes, this is mentioned in the article with a picture.

Re: How to start a rocket engine

#80

Post by rwmj »

> [Ignition chemical TEA-TEB] is quite expensive, costing roughly the same as the cost of RP-1 for the Falcon 9.

Is it true that the ignition chemical costs as much as the fuel? That sounds incredible.

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