Our Best Rocket Engines

[Streetwind]

What space enthusiast doesn't love a little tech ****?

Let's talk about rocket engines. Shiny, powerful, high-tech rocket engines, marvels of engineering. Can be large or small, old or new, from any nation around the globe - as long as they represent mankind's best. I only ask to limit this thread to engines that have actually flown. I know of many interesting concepts such as nuclear thermal rockets, massive linear aerospikes and other near-future propulsion ideas... but I want to talk about what we have achieved so far, not what we might achieve in the future.

I'll start off with the following, an engine many of you might be familiar with:

Rocketdyne RS-25

First flight: April 1981

Max thrust: 1,900 kN (ASL) - 2,300 kN (Vac)

Rated Isp: 363s (ASL) - 453s (Vac)

Fuel type: LH2/LO2 cryogenic bipropellant

Perks:

- Self-igniting and restartable

- 10° wide gimbal action

- Fully reusable

Cons:

- Expensive and time-consuming refurbishing process almost nullified advantages of reusability

- Storing liquid H2 in space is challenging

- Only moderate thrust, not suitable as a liftoff engine; needs SRB assistance to get off the pad

Why it is remarkable:

- Main engine of the U.S. space shuttle

- Outstanding fuel efficiency; burned from liftoff all the way to orbit

- Exceptional maneuverabilty afforded by wide gimbal

- Fairly reliable; despite recurring pre-launch issues, only one of 135 shuttle flights saw a single (out of three) engines fail in-flight

- Even 35 years after introduction, the upcoming Space Launch System (SLS) will rely on (expendable variants of) this engine

- Green engine: LH2/LO2 combustion produces only water vapor

What engines do you guys think should be counted amongst mankind's greatest, and why?

[Shuttle]

Soviet closed cycle engines

NK-33

+Light, easy to manufacture, cheap, reliable so far

-No gimbal

RD-170/RD-171/RD-180/RD-191

+Gimbal, a little higher ISP/thrust per chamber than latest NK-33 modifications but...

-Much havier than NK-33, hard to manufacture, expensive, not so reliable (though, as far as I know, engines failed due to manufacturing errors)

RD-0120

+Comparable peformance specifications to RS-25, easy to manufacture

-Bigger and heavier than RS-25

Also, I don't understand why they didn't develop a new 4-chamber engine based on NK-33 instead of RD-170, as well as why Glushko called NK-33 "rotten".

[Kryten]

The NK-33 is only cheap because they're surplus. The Russians have already developed a lightened RD-1XX derivative (RD-193) capable of replacing it when the stocks run dry.

[Tiberion]

Here: http://en.wikipedia.org/wiki/Template:Rocket_Engines

[Streetwind]

Here: http://en.wikipedia.org/wiki/Template:Rocket_Engines

Great, you can use Google But what is your favorite of the lot, and why?

[Idobox]

I'm not sure of its name, but the engine of the V2 should be here.

Sure it was a weapon of war, and not the first liquid fuel engine, but it was still a remarkable technological prowess, the V2 is one of the most famous rockets ever, it sparked the space race, and the design is still used as the basis for several projects.

[Albert VDS]

This is my favorite engine:

Merlin 1D

First flight: September 2013

Max thrust: 620 kN kN (ASL) - 690 kN (Vac)

Rated Isp: 282s (ASL) - 311s (Vac)

TWR: 150:1

Fuel type: RP-1 and liquid oxygen

[Wahgineer]

My favorite

Rocketdyne F-1:

First flight: November 6, 1967

Max thrust: 6.77 Mn (6770 Kn)

Isp: 263s

TWR: 94:1

Propellants: LOX & RP-1

Used in the Saturn-V. It is being reviewed so that a modern version can be used for the heavy SLS variants. The Saturn V was and still is the biggest and strongest rocket ever built, and will remain so up until the SLS, its and the shuttles modern descendant, launches in 2017.

[Streetwind]

Yeah, the F-1 is probably the biggest liquid rocket engine ever flown. Not the biggest rocket engine period (that probably goes to the space shuttle SRBs, those things are insane... they each have almost twice the thrust of an F-1!) but damn big nevertheless. The main issue it had was that it sacrificed everything for thrust, because the Saturn V was just so darn gigantic and heavy. As a result, the F-1 ended up with really poor overall efficiency.

If they're looking at a new version of it for the SLS, it's probably going to be an at least partial, if not complete rebuild. It's basically required, because the F-1 runs on kerosene, while the SLS appears to be going the liquid H2 route - it is built around a space shuttle tank, which is a LH2/LO2 carrier. Doing so allows them to use existing production lines and proven technology, which is a huge cost saver. I highly doubt they'll build an entirely different first stage variant, which would have to be designed, manufactured, tested and validated, just to hook up an engine with different fuel requirements... Unless the superheavy lifter gets a completely different main stage in the first place that doesn't build upon existing parts.

As for the Merlin D-series, you really gotta respect it's impressive thrust/weight ratio. They've got pretty much everything else beat, and development is still ongoing. I'm really excited for where SpaceX will be in five to ten years from now. They may well be able to push the envelope in ways that NASA doesn't have the budget to do.

As for the V-2's engine... I don't know if it even had a name. That's probably a tradition that came up only later. It wasn't a very good engine either, which is unsurprising considering it was one of the earliest liquid-fuel designs ever to see service. But yeah, it was the engine that boosted, for the first time ever, a manmade object into actual space. For that, it deserves recognition.

[Kosmic Debris]

This is my favorite engine:

Merlin 1D

First flight: September 2013

Max thrust: 620 kN kN (ASL) - 690 kN (Vac)

Rated Isp: 282s (ASL) - 311s (Vac)

TWR: 150:1

Fuel type: RP-1 and liquid oxygen

+1 - I got a tour of SpaceX last week and saw them up-close and personal. Amazing engineering (using fuel as hydraulic fluid, etc.) and production - 40/month!

[mdatspace]

http://en.wikipedia.org/wiki/Tripropellant_rocket

"In the 1960s, Rocketdyne fired an engine using a mixture of liquid lithium, gaseous hydrogen, and liquid fluorine to produce a specific impulse of 542 seconds, likely the highest measured such value for a chemical rocket motor."

That Isp.

[rasheed]

The Space Shuttle SRB's

THOSE THINGS ARE POWERFUL O_O

too bad they caused 1 shuttle to disintegrate.

[Tankbuster32]

The F-1 isn't the most powerful rocket engine ever, it's the RD-170. http://en.wikipedia.org/wiki/RD-170_(rocket_engine)

[MajorThomas]

Merlin 1D, F1, SSME and NK-33 are all great, having leading ISP or TWR values. Or just brute force like F1.

Then there's the (seldom used) Ion engines such as NSTAR with absurdly high ISP but really low thrust.

Video about the NK-33 and how it came to be used by USA rockets: https://www.youtube.com/watch?v=MZnYr94aa9E

[Nuke]

http://en.wikipedia.org/wiki/Tripropellant_rocket

"In the 1960s, Rocketdyne fired an engine using a mixture of liquid lithium, gaseous hydrogen, and liquid fluorine to produce a specific impulse of 542 seconds, likely the highest measured such value for a chemical rocket motor."

That Isp.

i could live with a hundred less isp if it means i dont have to carry liquid fluorine around.

[TheShadow1138]

The F-1 isn't the most powerful rocket engine ever, it's the RD-170. http://en.wikipedia.org/wiki/RD-170_(rocket_engine)

This is true, but the F-1 is the most powerful single-chambered liquid fueled engine ever built, as the RD-170 uses four separate thrust chambers to produce more thrust than the F-1. I have read, however, that some consider the RD-170 to be a cluster of four engines, and not a single engine. For those that do consider it a cluster, they would consider the F-1 to be the most powerful liquid fueled engine ever built. I do believe, however, that it is more widely accepted that the RD-170 is indeed the most powerful liquid fueled engine ever built.

[mdatspace]

i could live with a hundred less isp if it means i dont have to carry liquid fluorine around.

Liquid fluorine is the chemical from hell.

I would not go anywhere near it.

[NGTOne]

Personally, I'm rather a fan of the microwave-discharge ion engines they used on the Japanese Hayabusa probe. 26,000 hours of near-continuous operation FTW.

[tavert]

I'll put a vote in for the RL10, the very first LH2 engine built in the US. First flight 1961, workhorse of the venerable LH2-LOX Centaur upper stage used with many Atlas and Titan rockets, in a cluster of 6 powering the upper stage of the initial version of the Saturn I, and in modified form powering the Delta III/IV Cryogenic Second Stage. Still flying after over 50 years!

Thrust depends on variant, but ranges from 66 to 110 kN, mass from 131 to 277 kg.

Pros:

- Extensive track record and flight history, I suspect it has the most flights of any cryogenic engine, and if it's not in the overall lead among all engines then it's probably only second to the Soyuz RD-107 family.

- High specific impulse of 440-460 s.

- Powered the upper stages that launched the Surveyor lunar probes, Mariner 6, 7, (8 was a whoopsie) and 9 to Mars, Mariner 10 to Venus and Mercury, Viking 1 and 2 to Mars, Pioneer-Venus 1 and 2, Pioneer 10 and 11 and Voyager 1 and 2 and Cassini/Huygens and New Horizons and Juno to the outer solar system, the Mars Reconnaissance Orbiter and Curiosity Rover, and countless communications and military satellites.

Cons:

- Expensive

- Very old design

Edited February 1, 2014 by tavert

[Deathsoul097]

I don't really have a favourite engine as such. I like the Merlin Series, along with the J-2, but I don't have a favourite engine, as I view them as more of a utility as a feature. (They are amazing, don't get me wrong, each engine is a marvel of modern (and sometimes old) technology. But that is my view.)

(Fluorine is some nasty stuff. Especially as Dioxygen Difluorine. That is some pure evil right there. That stuff sets ICE on FIRE.)

Edited February 1, 2014 by Deathsoul097

[fireflower]

Doing so allows them to use existing production lines and proven technology, which is a huge cost saver.

But it makes it so much less capable as a launcher to use LH2/LOX at the bottom of the gravity well.

[jwenting]

But it makes it so much less capable as a launcher to use LH2/LOX at the bottom of the gravity well.

so? There's no single engine that's good at everything over the entire flight profile of a space launcher. That's one reason why all successful launcher are multi staged vehicles, with different engines in different stages.

This whole "which is the best" idea is silly, there is no overall best, can't be. At most there might be a "best" for a specific phase of a specific mission given specific budget and environmental constraints on that mission.

And even then "best" is more often than not warped by politics, for example a Korean rocket is unlikely to ever use a Japanese engine even if that engine is theoretically superior simply because the Japs and Koreans hate each others' guts.

[Streetwind]

But it makes it so much less capable as a launcher to use LH2/LOX at the bottom of the gravity well.

Indeed - that's where the solid motors come in. On the space shuttle, the two SRBs supplied 83% of the lift-off thrust, with the remaining 17% being the shuttle's three RS-25 and two OMS engines. That's why I mentioned in the cons that the RS-25 needs assistance to get off the pad The SLS, too, will use SRBs to supply lift-off thrust. It's not a bad strategy, considering that these SRBs are very cheap and very powerful (as opposed to KSP, where cost does not matter and liquid engines are simply better in all cases).

That doesn't change the fact though that you have some very efficient engines running alongside the SRBs. You could be using more powerful, less efficient engines that could achieve lift-off thrust on their own, making SRBs unnecessary. But then they couldn't get you anywhere near orbit. You'll need an additional stage in the middle with smaller engines, making the rocket taller and heavier. The end result probably wouldn't be much different in performance, but likely more expensive due to using liquid engines everywhere.

[fireflower]

so? There's no single engine that's good at everything over the entire flight profile of a space launcher.

I understand the physics. I was pointing out that the same rocket would be less efficient as a rocket (starting mass relative to payload delivered) if it used LH2 exclusively all the way to orbit. Compare to Energia, which used/will use RP1 in four booster rockets and LH2 for the main engines. What I did not know, and feel bad for not looking up myself, was this:

That's where the solid motors come in. On the space shuttle, the two SRBs supplied 83% of the lift-off thrust... The SLS, too, will use SRBs to supply lift-off thrust.

Now it makes a lot more sense to retool the F-1 engines to burn LH2.