What's your favorite rocket engine?

[DAL59]

Open cycle nuclear uranium hexafloride gas core.  ISP: 5000 Thrust: Some millions of newtons

[JucheJuiceMan]

RD-270, as powerful as Saturns F1 while around 40% of weight.

[DDE]

Wait, @wumpus, so the 3.75 m sustainer whatchimacallit is conceptually based on the M-1, it seems?

13 hours ago, JucheJuiceMan said:

RD-270, as powerful as Saturns F1 while around 40% of weight.

Yeah, but there’s a reason the UR-700 ended up almost four times as heavy.

[SargeRho]

The XRS-2200, that is the linear aerospike engine developed for the X-33 and Venture Star. It's not the prettiest, or the most efficient rocket engine ever built, but it strokes my sci-fi obsession in all the right places.

[magnemoe]

22 hours ago, shynung said:

Project Orion. The one and only torch drive we have ever designed so far.

Yes, pretty much
my KSP version of it. 

Large docking port in front for bases and stuff, extra ports on the outriggers for probes 

[Grand Ship Builder]

17 hours ago, SargeRho said:

The XRS-2200, that is the linear aerospike engine developed for the X-33 and Venture Star. It's not the prettiest, or the most efficient rocket engine ever built, but it strokes my sci-fi obsession in all the right places.

There's this relatively little-known company called "ARCA Aerospace" that specializes in Single Stage to Orbit launchers using Aerospikes. Construction of their rocket is nearly done, and the launch should be pretty soon from now.
 

[vitekc45c]

Nuclear saltwater ones, nothing beats riding on continuous nuclear explosion 

[ChrisSpace]

Definitely the Epst- oh, out of ones that have been built in real life? Probably one of those Cold War NTRs.

[JucheJuiceMan]

On Sunday, November 05, 2017 at 11:33 AM, DDE said:

Wait, @wumpus, so the 3.75 m sustainer whatchimacallit is conceptually based on the M-1, it seems?

Yeah, but there’s a reason the UR-700 ended up almost four times as heavy.

UR-700 was designed for direct flight to the moon rather than using LTO approach. Thus more fuel was needed.

[DDE]

6 minutes ago, JucheJuiceMan said:

UR-700 was designed for direct flight to the moon rather than using LTO approach. Thus more fuel was needed.

But not to such a degree. A 50% growth in IMLEO cannot alone account for such difference, especially with propellant crossfeed and/or nuclear third and fourth stages.

[ChrisSpace]

Okay, here's my more detailed answer (assuming the goal is to find an ideal engine for a vehicle that can lift off from anywhere and go anywhere else)

 

Chemical propulsion: Horridly low Isp.

Solid-Core Nuclear-, Solar- or Antimatter-thermal rocket, LANTR, Vapour-Core or Liquid-Core NTR: Isp is a bit low, but I like the idea.

Metallic Hydrogen, Antimatter Gas Core engine, high-TWR He3-D Fusion, Epstein Drive, Inertially confined Proton-Proton Fusion or Antimatter-Catalysed Microfission Hydrogen-Boron Fusion: High-thrust and High-Isp. My personal choices.

Gas-core, Plasma-core or detailed Beam-core Antimatter designs, Antimatter "Bottle" engine, Positron Ablative, Laser-thermal, Metastable Helium, Magnetoplasmadynamic, Pulsed Plasmoid, VASIMR, Colloid, Hall Effect, Ion, Arcjet, Microwave Electrothermal, Resistojet, Wakefield E-Beam, most types of Fusion, Closed-Cycle Gas Core NTR, Fission-fragment, Fission Sail, Antimatter-driven Sail, Mini-mag Orion, n-Li6 micro fission, PuFF, most types of Antimatter-Catalysed micro fission or micro fusion, Photon, Magnetic or Electric sail, Mass Driver or Photon Beam engine: TWR too low to lift off Earth, at least not with enough propellant to reach LEO with any payload.

Coaxial Gas Core NTR, Open-Cycle Gas Core NTR, NSWR, Nuclear Pulse Propulsion or Medusa: Throws radioactive death everywhere.

[michal.don]

On 4. 11. 2017 at 3:16 PM, wumpus said:

If you check the specs, it hardly has any advantages over using 5 J-2s like used on Saturn V.

Just the part count. Or do you think NASA's computers can run the launches without lag?

[Julien Kerman]

RS-68A

[Silavite]

RL60

Should have been the RL10's successor, but the engine never got a lease on life for reasons beyond me.

[DDE]

*shrug* Let's go inflammatory, shall we?

What may turn out to be Energomash RD-800. Up to 37% increase in kerolox Isp claimed by some "highly" "informed" sources, annular pulse-detonation motor.

Spoiler

Puny Orion, only detonates at 1 Hz, not 20 kHz.

 

[GoSlash27]

The NASA CECE deep- throttling engine.

 

Honorable mention to the NERVA.

 

[Rakaydos]

Hall Thruster.

[Confused Scientist]

The Project Orion pusher plate/nuke combo. I recall off the top of my head the thing had an ISP of up to one million seconds. (Source: True Stories of the Space Age)

[Ten Key]

Removed some political content from this thread for 2.2b violation.

[Ultimate Steve]

On ‎11‎/‎5‎/‎2017 at 10:33 PM, Grand Ship Builder said:

There's this relatively little-known company called "ARCA Aerospace" that specializes in Single Stage to Orbit launchers using Aerospikes. Construction of their rocket is nearly done, and the launch should be pretty soon from now.
 

Huh, I didn't think they were actually building it, I thought it was just a concept for now. How close are they and how much of it have they built?

[CJrm1]

Definitely the J-2

[Geschosskopf]

On 10/30/2017 at 6:47 PM, Grand Ship Builder said:

What's your favorite rocket engine?

The Sepratron, of course!  It has thousands of very entertaining uses and several vitally important practical uses.  That's way more than most rocket engines can say.  The vast majority have only 1 practical use, which usually isn't vital because there are other options to do the same job, and that job is not entertaining, just working-stiff rat-race stuff.

Edited November 25, 2017 by Geschosskopf

[Bill Phil]

On ‎11‎/‎5‎/‎2017 at 4:39 AM, SargeRho said:

The XRS-2200, that is the linear aerospike engine developed for the X-33 and Venture Star. It's not the prettiest, or the most efficient rocket engine ever built, but it strokes my sci-fi obsession in all the right places.

Speaking of, there's a building at MSFC with one of these out in front. There's also an F-1, NERVA, and Shuttle SRB.

On ‎11‎/‎5‎/‎2017 at 4:33 AM, DDE said:

Wait, @wumpus, so the 3.75 m sustainer whatchimacallit is conceptually based on the M-1, it seems?

Yeah, but there’s a reason the UR-700 ended up almost four times as heavy.

Which UR-700? Direct flight to the moon (UR-700, 4823 tonnes), or the nuclear monstrosity (UR-700M, 16000 tonnes)? Saturn V is about 3038 tonnes, for comparison. All numbers from Astronautix.

[OrbitalBuzzsaw]

Gotta go with the raptor

[Geschosskopf]

16 hours ago, Ultimate Steve said:

Huh, I didn't think they were actually building it, I thought it was just a concept for now. How close are they and how much of it have they built?

According to the company's website, the 1st engine and the ground test stand for it were completed the end of September.  ARCA has a weekly YouTube vlog which I haven't seen all of, but as of the 1st of last month (episode 16), they were doing tests of various subsystems and wrangling with the FAA to get flight clearance.  They do intend to shoot the test rocket as soon as they can, however.

And thanks to @Grand Ship Builder for bringing this to my attention.  I'd never heard of it before.  Love aerospikes, though