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How do you power a rocket engine?

everydayastronaut.com

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Re: How do you power a rocket engine?

#11

Post by panick21_ »

JKCalhoun wrote: post #10
panick21_ wrote: post #8

One thing I always wanted to see was a close expander cycle areospike. The reason is that expander cycles are heat limited. Areospikes biggest negative is that they require more cooling but if you are heat limited that is an advantage. You could make the highest possible thrust expander cycle and it would be high efficiency upper stage for early staging as you don't lose efficiency by staging early. ------- Another t…

Perhaps, being pragmatic, tweaking existing designs was not going to put more money into the R&D of Yoyodyne [1]. [1] https://en.wikipedia.org/wiki/Yoyodyne

I assure you, the same amount of money could have been spent. Just for far better results.

Re: How do you power a rocket engine?

#12

Post by cubefox »

panick21_ wrote: post #8

One thing I always wanted to see was a close expander cycle areospike. The reason is that expander cycles are heat limited. Areospikes biggest negative is that they require more cooling but if you are heat limited that is an advantage. You could make the highest possible thrust expander cycle and it would be high efficiency upper stage for early staging as you don't lose efficiency by staging early. ------- Another t…

Regarding the first point, I'm not sure whether aerospike engines can still be considered heat limited. Even in the 90s with the X-33 aerospike spacecraft, heat was not cited as the reason for cancellation. And nowadays material science as progressed by a lot, which resulted in more heat resistant materials, e.g. this one: https://www.nasa.gov/feature/glenn/2022/nasa-s-new-material-...

Re: How do you power a rocket engine?

#13

Post by simne »

jacksonkmarley wrote: post #2

Wouldn't the pressurant/backfill gas dilute the propellant as it was added?

Sure, if the pressurant gas dissolves into the liquid propellant.

But mostly chosen pressurant which is not dissolves, or used some type of separating membrane (or piston), for example, in Soviet space stations used https://en.wikipedia.org/wiki/Metal_bellows

Re: How do you power a rocket engine?

#15

Post by speedylight »

xbmcuser wrote: post #5

If you are interested in rockets I would recommend this youtube channel. https://www.youtube.com/c/Integza It is a great resource to learn about all different kind of rockets and rocket engines. And quite amazing to see how 3d printing can allowto build so many of miniature versions.

Integza is one of my favorite channels of all time, his videos are always really informative and fun to watch. The only problem is he’s completely careless about safety—mainly by not wearing any protective gear for the exhaust fumes which include burned plastic.

Re: How do you power a rocket engine?

#17

Post by showerst »

speedylight wrote: post #15
xbmcuser wrote: post #5

If you are interested in rockets I would recommend this youtube channel. https://www.youtube.com/c/Integza It is a great resource to learn about all different kind of rockets and rocket engines. And quite amazing to see how 3d printing can allowto build so many of miniature versions.

Integza is one of my favorite channels of all time, his videos are always really informative and fun to watch. The only problem is he’s completely careless about safety—mainly by not wearing any protective gear for the exhaust fumes which include burned plastic.

I’m really torn on Integza. It’s a great channel and I love his spirit, but guys like that (and the teenagers that follow them) end up getting hurt or burning down their houses, which makes the news and gets new restrictions passed on all of us.

Just a _little_ more nodding to safety would make him an awesome resource.

Maybe safety culture in Portugal is different, but in the US he does tons of stuff that violates the model rocket safety code, or is outright stupid.

Re: How do you power a rocket engine?

#18

Post by master_crab »

For all the talk of SpaceX and a new race to Mars, no one seems to remark on the fact that rockets haven’t remarkably changed much since Goddard’s day.

I remember asking one of my profs in college (an early researcher of the ramjet) what’s holding jet and rocket technology back. He said: melting point temps.

Re: How do you power a rocket engine?

#19

Post by hydrogen7800 »

jacksonkmarley wrote: post #2

Wouldn't the pressurant/backfill gas dilute the propellant as it was added?

Expert here. I'm a longtime lurker on HN, but registered just for this comment. I design aerospace pressure vessels for a living. As showerst alluded to, there are often things called "propellant management devices" or PMDs. There are a few reasons these might be used. In zero G, you need the propellant sump to remain wetted with propellant; it would be bad to ingest the pressurant/ullage gas into your engines. Some PMDs allow the pressurant and propellant to occupy the same volume, and will use surface tension devices inside the tank to direct liquid to the sump. These can be screens, vanes, channels, etc. In other cases, the pressurant and propellant are kept separate by a bladder. These bladders can be rubber, or even metal. The propellant mass is usually a large proportion of a space vehicle's mass, and you can't have that much sloshing around when you need dynamic control. A metal diaphragm keeps the propellant more or less static, and its center of mass in a predictable location.

As for the pressurant gas dissolving into the propellant in non-PMD tanks, I don't know enough about that. I imagine the solubility of He (it is usually helium) in these propellants is either accounted for, or negligible.

Edit: P.S. Software engineering is mostly foreign to me and much of HN content is over my head, but I like he level of discourse here. So, when a topic came up that I could actually contribute to, I jumped.

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