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What's your favorite rocket engine?


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Rocketdyne F1 - for when you absolutely, positively need to throw a metric boatload of stuff into space. Accept no substitutes. 

Sure, it hasn't got the ISP. Sure it was never the most technically advanced engine. But sometimes size has a quality all it's own. And lets be honest - it's the most iconic engine you could ever want.

 

Edited by KSK
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For purpose in real life: the Lunar Module Descent Engine. It was throttleable, restartable, and used storable (if toxic) propellants. Plus it was also used as an upper stage engine eventually. Close behind are the Merlin and RL-10 engines. Although the SSME's have "the look..."

For usage in my RO/RP-0 campaign: The German Astris. Isp above 300s, storable propellants, infinitely restartable, and quite the gimbal range. I'd say more than half of my launches have used at least one Astris.

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7 hours ago, regex said:

RD-107/108. A true workhorse, first there and after 60 years still putting things into orbit.

Actually, the RD-107/108 is long since retired.  Like pretty much everything else in the Soyuz booster and Soyuz spacecraft, it's been replaced by an updated and modified version.

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41 minutes ago, DerekL1963 said:

Actually, the RD-107/108 is long since retired.  Like pretty much everything else in the Soyuz booster and Soyuz spacecraft, it's been replaced by an updated and modified version.

Right, just like pretty much every piece of space hardware older than a few years.

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1 hour ago, DerekL1963 said:

Actually, the RD-107/108 is long since retired.  Like pretty much everything else in the Soyuz booster and Soyuz spacecraft, it's been replaced by an updated and modified version.

The engines, and really the entire R7-derived booster/core stages haven't changed all that much since the early days.  Same engine design really with moderate upgrades, but no substantial redesign.  Soyuz 2.1v is a different matter of course.

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Im gonna go leftfield and say the little solids that propel fireworks.

Because no matter the size, every solid rocket I see, from SAMs to SSRBs, all I see is simply a scaled-up firework - and that gives me good brain feels.

***

All the different liquid ones are much of a muchness, but I like SABRE because its fancy.

Edited by p1t1o
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Coming in out of left field, the XLR81 model 8096B engine. A gas generator engine, running on storable propellants (MMH+HMZ/N2O4, to be precise), with thrust of 71 kN, a vacuum specific impulse of up to 330 seconds, rated for up to 200 restarts and 1200s burn time... and not subject to ullage.

Unfortunately, it never got used for anything. The Agena upper stage that used the XLR81 fell out of use, and the AJ-10 was picked over the XLR81 as the STS OMS engine. It's a shame-it was a good engine. There just wasn't any demand for a storable vacuum engine with that much thrust.

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9 hours ago, IncongruousGoat said:

Coming in out of left field, the XLR81 model 8096B engine. A gas generator engine, running on storable propellants (MMH+HMZ/N2O4, to be precise), with thrust of 71 kN, a vacuum specific impulse of up to 330 seconds, rated for up to 200 restarts and 1200s burn time... and not subject to ullage.

Unfortunately, it never got used for anything. The Agena upper stage that used the XLR81 fell out of use, and the AJ-10 was picked over the XLR81 as the STS OMS engine. It's a shame-it was a good engine. There just wasn't any demand for a storable vacuum engine with that much thrust.

I'm looking more and more at this, and an engine like that would be exceedingly useful.

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My favorite rocket engine is the one that:

1. Has 3000 ISP
2. Runs on Iron and Silicon that can be stored at a density of 10 (or does not need a fuel tank, can be hung on the side of the ship).
3. Has a TWR of 1000:1
4. Has unlimited duty cycle.
5. Thrust per M2 of surface area is 3000 kN

IOW its the engine that can get you to Mars and back. Also known as the VW3000  (Vapor ware 3000).

RL-10b-2 from orbit outbound.
ISP of 475 at 227 kg weight is just unbeatable performance to weight. Drawback, full thrust only 220 seconds. Your not getting Jeb to Mercury with that engine.

Rocketdyne RS-68A for anything from the ground into orbit.

 

Edited by PB666
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13 hours ago, _Augustus_ said:

The M1, the largest rocket engine ever built and fired. Never flown thanks to budget cuts and the cancellation of the Apollo program and its successors.

m1engine.jpg

There is so much that might have been.........

Almost forgot about the M-1

they stole it from the Elizabeth Tower!

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23 hours ago, _Augustus_ said:

The M1, the largest rocket engine ever built and fired.

m1engine.jpg

There is so much that might have been.........

Oh wow... I had no idea they made it !

Have they sneakily took the Tzar bell ?

Edited by YNM
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On 11/1/2017 at 10:13 PM, _Augustus_ said:

The M1, the largest rocket engine ever built and fired. Never flown thanks to budget cuts and the cancellation of the Apollo program and its successors.

There is so much that might have been.........

If you check the specs, it hardly has any advantages over using 5 J-2s like used on Saturn V.  Work on the M1 was canceled in 1966, same year as the J-2 flew and Gemini ended (and pretty much was the end of the "direct flight" option).  While there was some ideas about making it a first stage, the shear size of the hydrogen tanks must have been an issue (would such a thing even fit in the VAB?) and getting a reasonable sea level thrust and Isp would have been difficult.  Even then, first stage Isp really isn't all that important: if you take off at TWR of 1:1.2 your gravity losses are going to outweigh all other losses so much to make the whole point moot (not to mention some 500,000 tons of upper stages adding to your "dry weight").  I suspect you would want this for a "direct flight" to the Moon.  No idea if it was ever designed to be restartable (J-2 was), but you would likely need that for a trip to Mars (you might get away with it on a heavy flight to lunar orbit).

Clear mission goals (specifications in most projects) and real deadlines do wonders for engineering projects.  They may have produced and abundance of magic, but when it came down to choosing which parts to use for the final design they stuck with things that were known to work (or at least most likely to work for the "insert magic here" parts).  Compare this to SLS which is the type of program much more likely to pursue large engines for sake of thrust but is unlikely to produce anything besides pretty museum pieces.

- obligatory "Favorite Rocket Engine": Nobody has said a word about Orion [Freeman Dyson's baby, not the current disaster]?  Count me in as an unrepentant Orion fanboy.  "Orion Shall Rise".

 

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