The new rocket engine

[Gaarst]

I don't know much about this engine's Isp, but if it's Isp asl is not too bad, its high thrust and reduced size would make it a pretty good Eve ascent engine, IMO. Although it might be a bit heavy, almost 4t for a 1.25m engine is a bit high...

[mikegarrison]

A real shuttle almost lifted a cargo bay full of liquid hydrogen and liquid oxygen, plus payload. It was deemed too risky after the fact but, considering that other lifters do exactly the same thing day in and day out, it would not be unreasonable for a shuttle to lift a mass of fuel equal to its payload.

Liquid hydrogen is much lighter.

As I edited my note above, a Shuttle payload bay full of RP1 would be about 1000 tonnes, unless I punched a number in wrong somewhere.

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Another way to look at it -- a real shuttle has almost no ability to change orbital planes after launch. In KSP, that's only a minor inconvenience for most launch vehicles. The scaling factors compound.

Edited August 25, 2015 by mikegarrison

[DocMoriarty]

The new engine isn't that bad with its stats. 4xReliant = 860kn/Space at 5t weight. Though of course ISP is important, maybe even more than absolute thrust. In thrust we trust, though!

[Alshain]

Liquid hydrogen is much lighter.

As I edited my note above, a Shuttle payload bay full of RP1 would be about 1000 tonnes, unless I punched a number in wrong somewhere.

Your straw man argument isn't making much sense. Nobody is arguing it should carry 1000 tonnes, except you.

Another way to look at it -- a real shuttle has almost no ability to change orbital planes after launch. In KSP, that's only a minor inconvenience for most launch vehicles. The scaling factors compound.

If you are building a realistic shuttle, you won't be using the Vector in space... at all. This is another strawman, you are arguing orbital plane changes with an engine that's was never fired in space and it has nothing to do with what the shuttle could lift.

Edited August 25, 2015 by Alshain

[regex]

Another way to look at it -- a real shuttle has almost no ability to change orbital planes after launch. In KSP, that's only a minor inconvenience for most launch vehicles. The scaling factors compound.

Yes, which is why it is utterly useless to compare RL and KSP systems. Saying that a shuttle shouldn't be able to carry an entire tank of fuel to orbit in KSP is ridiculous because the scales and payload fractions are completely different than real life; your expectations need to change. Getting ~1000 tons to orbit would take another 2000~3000 tons of launcher in KSP. IRL you'd need some 98,000 tons of launcher.

[cantab]

The model is OK I guess, but not great. It just looks like a bare nozzle without any supporting hardware and it's not much like the other engines. True, a lot of the existing engines would like an art pass, but I hope this isn't meant to be the "type specimen" of said future art pass.

The specs seem all wrong, giving it a crazy amount of thrust for a 1.25m engine as well as an extreme gimbal. Maybe that is what's needed for KSP shuttles to fly well though? (The balance on them is harder than in real life for various reasons after all). Also I'd rather see a stronger thrust falloff with altitude. Not as bad as say the 909, not least because sea-level thrust is needed for the engine to do its job, but maybe something like 260-330 s Isp would be good, a bit worse in atmo and a bit better in vacuum than the LV-T45.

Then again, the specs on the SLS parts are still all wrong too.

[Alshain]

As a comparison, this is Ven's take on the same engine. It feels fairly balanced to me, maybe just a little strong, and you will notice the stats are not too far from the temporary ones in PorkJet's image (though we can't see ISP). I've been able to launch successful Mk2 (single engine) and Mk3 (triple engine) designs with good payloads. I'm not saying it's perfectly balanced, but it is close. I still think we need bigger SRB's for Mk3 though, the lack of proper SRB's is probably is why Ven made the mains stronger.

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The model is OK I guess, but not great. It just looks like a bare nozzle without any supporting hardware and it's not much like the other engines. True, a lot of the existing engines would like an art pass, but I hope this isn't meant to be the "type specimen" of said future art pass.

The specs seem all wrong, giving it a crazy amount of thrust for a 1.25m engine as well as an extreme gimbal. Maybe that is what's needed for KSP shuttles to fly well though? (The balance on them is harder than in real life for various reasons after all). Also I'd rather see a stronger thrust falloff with altitude. Not as bad as say the 909, not least because sea-level thrust is needed for the engine to do its job, but maybe something like 260-330 s Isp would be good, a bit worse in atmo and a bit better in vacuum than the LV-T45.

Then again, the specs on the SLS parts are still all wrong too.

The 1.25m format is purely for the sake of being able to fit it properly on the shuttle fuselage. For all intents and purposes, it is a 2.5m engine. I imagine it will be in with the 2.5m parts in the tech tree, so you will still need the other 1.25m engines.

Edited August 25, 2015 by Alshain

[KerBlammo]

They should do that with all engines, to be honest.

They should. And this engine should be able to gimbal left-right and then up-down while still on the launch pad when in a cluster of three.

[Foxster]

They should. And this engine should be able to gimbal left-right and then up-down while still on the launch pad when in a cluster of three.

I get the impression from the picture that the nozzle can be set at an angle to the mount in the VAB. Not sure about after that though.

[regex]

I get the impression from the picture that the nozzle can be set at an angle to the mount in the VAB. Not sure about after that though.

You can do that with any engine, IIRC. What we really need is a wide gimballing range, something like 8~12 degrees, to help control the shuttle on the way up.

[MaverickSawyer]

less struts!

Heretic!!!!

Edited August 26, 2015 by MaverickSawyer

[MadChris48]

What we really need is a wide gimballing range, something like 8~12 degrees.

I wonder if that's enough range of motion that a funkily designed ship could gimbal far enough to blow itself up.

[regex]

I wonder if that's enough range of motion that a funkily designed ship could gimbal far enough to blow itself up.

Oh sure, why wouldn't it be? I can easily flip a totally stable rocket in RO/RSS with a standard 8 degree gimbal.

[Alshain]

My concern with high gimbals is the game's tendency to be all or none. Press the 'W' key and your rocket is turning circles because of engines that gimbal so fast, it gave the engineers that designed it whiplash. I feel like a 12 degree gimbal engine won't work as well in the game as it does in real life. Have any mods done it?

[Red Iron Crown]

MechJeb's SmartASS handles high gimbal ranges just fine in most sane cases. It's not the gimbal range itself so much as the stock SAS's well known tendencies and, as you say, the digital nature of keyboard control. Analog is much better in this regard.

[cantab]

My concern with high gimbals is the game's tendency to be all or none. Press the 'W' key and your rocket is turning circles because of engines that gimbal so fast, it gave the engineers that designed it whiplash. I feel like a 12 degree gimbal engine won't work as well in the game as it does in real life. Have any mods done it?

Try fine controls, or set up an analogue gamepad or joystick.

[MadChris48]

Oh sure, why wouldn't it be? I can easily flip a totally stable rocket in RO/RSS with a standard 8 degree gimbal.

I mean like radially mounted engines angling so far as to torch the tank they are attached to.

[Alshain]

Try fine controls, or set up an analogue gamepad or joystick.

I do use an analog stick but not everyone does. Fine controls work, but do they really work when your gimbal is huge?

[Whirligig Girl]

A real shuttle almost lifted a cargo bay full of liquid hydrogen and liquid oxygen, plus payload. It was deemed too risky after the fact but, considering that other lifters do exactly the same thing day in and day out, it would not be unreasonable for a shuttle to lift a mass of fuel equal to its payload.

What do you mean? Was this some minor story in the corner of a space engineering history book? What?

[mythbusters844]

What do you mean? Was this some minor story in the corner of a space engineering history book? What?

https://en.wikipedia.org/wiki/Centaur_%28rocket_stage%29#Shuttle-Centaur

[CptRichardson]

If you guys are worried about how to attach these to the rear of your Mk3 craft, why not ask for a proper adaptor plate with a semi-shroud? With, say, oh, four or six mounting points for these bad boys?

[Frozen_Heart]

I suspect that this engine will almost be too powerful and sensitive for normal rockets. The SAS will go mental trying to control it on a 1.25m stack.

[regex]

Any issues could be solved by making the engine gimbal and/or SAS tweakable.

HAHAHAHAHAHAHAHA Who am I kidding?

[cantab]

HAHAHAHAHAHAHAHA Who am I kidding?

The gimbal limits are already tweakable. But hey, never let reality get in the way of a jab against Squad.

[Deutherius]

I like the engine, but I also think it's way too powerful. Three Skippers have more than enough thrust to lift a Mk3 sized shuttle + payload into orbit, it's the SRBs that are way too puny for the task. I can clip a ton of them, but then again I can do that with the Skippers as well.

Any new part is a welcome addition to the collection, of course.