The Vector: Your thoughts

[GoSlash27]

13 minutes ago, swjr-swis said:

If it is really that specific a use case, then why wasn't it published as an integrated part of the Mk3 Engine Mount?

swjr-swis,

 You'd have to ask PorkJet about that. He was very specific about why he made this engine, and this is why. He saw people clipping Skippers and Mainsails to make Shuttle replicas and decided to make a SSME specific to that role. In fact, if you look in the file folder, you will see that the engine is actually called "SSME".

 Now... this is not to say that the Vector was intended to be used *exclusively* this way. If I were to design one, I would do what he did too. *BUT* It was intended to do this job (in addition to whatever else our devious minds can conjure up) and it's unfortunately OP for the job of a SSME.

 That's why it needs rebalancing as an *individual* part. The 2.5m engines as a family need rebalancing for a completely different reason: they are too close to the 3.75m engines at the moment and too far away from the 1.25m parts. That's a gameplay imbalance that makes the big engines weak and the little engines strong.

 A simple rebalance can make all of the engines more balanced and useful, and we can even keep the Vector in the process.

Best,

-Slashy

 

[GoSlash27]

17 minutes ago, Tweeker said:

That not really what I'm advocating, all I'm try to say is the Vector is far out of line with the rest of the 1.25m engines, Which by it's shape and attachment node it fits with.  If it has the weight, cost, and thrust of a 2.5m engine, then make it a 2.5m engine.  Including it as a single engine because it looks right on the rear of the shuttle creates more problems than it solves. It's a band-aid for the fact that SRBs in the game are not scaled to be "realistic"  compared to the liquid fuel engines.

Tweeker,

 This is the crux of the matter. It is, by function, a 2.5m engine *not* a 1.25m engine. And while giving it a 1.25m footprint in order to make it look like a SSME may cause problems, this is specifically why it was created.

 If you stop thinking of it as a "1.25m engine" (which is incidental), you will realize that it's not OP at all. At least as a KSP engine. It *is* OP as a SSME within KSP.

It's all the same to the engine whether it's innards are arranged short 'n' wide or tall 'n' skinny. It weighs a certain amount, creates a certain amount of thrust, and carries a price tag. That's what defines it's utility (or lack thereof).

Best,

-Slashy

 

[Alshain]

It works just fine as an SSME for me.  It didn't seem overpowered at all.

Edited January 15, 2016 by Alshain

[Tweeker]

3 minutes ago, GoSlash27 said:

Tweeker,

 This is the crux of the matter. It is, by function, a 2.5m engine *not* a 1.25m engine. And while giving it a 1.25m footprint in order to make it look like a SSME may cause problems, this is specifically why it was created.

 If you stop thinking of it as a "1.25m engine" (which is incidental), you will realize that it's not OP at all. At least as a KSP engine. It *is* OP as a SSME within KSP.

It's all the same to the engine whether it's innards are arranged short 'n' wide or tall 'n' skinny. It weighs a certain amount, creates a certain amount of thrust, and carries a price tag. That's what defines it's utility (or lack thereof).

Best,

-Slashy

 

That's all very true, but because it is packaged as a single engine, rather than a cluster of 3 on the rear of the shuttle it begs to be compared to the other engines that would fit in the same space. game wise.

 

[regex]

29 minutes ago, Tweeker said:

That not really what I'm advocating, all I'm try to say is the Vector is far out of line with the rest of the 1.25m engines, Which by it's shape and attachment node it fits with.  If it has the weight, cost, and thrust of a 2.5m engine, then make it a 2.5m engine.  Including it as a single engine because it looks right on the rear of the shuttle creates more problems than it solves.

People need to rid themselves of the notion that node attachment size dictates role and thrust.  An engine is an engine is an engine; they come in all shapes and sizes, and vary in thrust, isp, and even mass (to some extent) within those sizes.

23 minutes ago, Tweeker said:

I agree with the sentiment, but the shuttle parts are fixed in size, so the engine needs to scale to fit the existing, in game shuttle.

Nonsense.  There are plenty of ways to make a shuttle bigger and one doesn't have to rely on vertical stacking of similar parts to achieve that.  How about building a longer shuttle with a higher payload?

[Temstar]

1 minute ago, Tweeker said:

That's all very true, but because it is packaged as a single engine, rather than a cluster of 3 on the rear of the shuttle it begs to be compared to the other engines that would fit in the same space. game wise.

Not to mention that when it does come in a package of four that package is much bigger in volume than four vectors on their own.

[Tweeker]

18 minutes ago, regex said:

People need to rid themselves of the notion that node attachment size dictates role and thrust.  An engine is an engine is an engine; they come in all shapes and sizes, and vary in thrust, isp, and even mass (to some extent) within those sizes.

Nonsense.  There are plenty of ways to make a shuttle bigger and one doesn't have to rely on vertical stacking of similar parts to achieve that.  How about building a longer shuttle with a higher payload?

    The notion is based in the way the game acts. If you put  1.25 m engine in a 2.5m stack you get a wasp-waist in the rocket. It's why a lot of people use the poodle over the terrier. Because the vector stack natural beneath 1.25m fuel tanks it begs to be compared to 1.25m engines.  

       Making the shuttle longer still leaves the same problem, the engines that can mount behind it are generally 1.25m engines. so again you naturally compare among the engines that fit on those mounting pads.

     The real problem is that SRBs are mis-sized to the role of lifting a 3m shuttle so the SSME ends up being OP to compensate.  

[regex]

7 minutes ago, Tweeker said:

    The notion is based in the way the game acts. If you put  1.25 m engine in a 2.5m stack you get a wasp-waist in the rocket. It's why a lot of people use the poodle over the terrier.

But now you can use an interstage fairing, problem solved.  Hell, we used to do that back in the day with structural plates or struts to make a cage interstage.

7 minutes ago, Tweeker said:

Because the vector stack natural beneath 1.25m fuel tanks it begs to be compared to 1.25m engines.

I think performance is a much better indicator of how the engine should be compared considering that engines come in all different sizes for a given performance/price, as is evident not only in real life but also in KSP.

7 minutes ago, Tweeker said:

       Making the shuttle longer still leaves the same problem, the engines that can mount behind it are generally 1.25m engines. so again you naturally compare among the engines that fit on those mounting pads.

See above.  Performance/price is what matters, not form factor.

7 minutes ago, Tweeker said:

     The real problem is that SRBs are mis-sized to the role of lifting a 3m shuttle so the SSME ends up being OP to compensate.

I don't agree and have seen no evidence of this claim.  Shoot, we got a few people in this thread arguing that the Vector is too powerful for Shuttle use, leading me to believe SRM performance has nothing to do with the engine.  Regardless of whether SRMs are underpowered, the Vector is its own thing.

[MagicFireCaster]

Looks pretty good and i like the fact you can stick it to a lot of surfaces, i wish other engines could do that 

[Tweeker]

3 minutes ago, regex said:

But now you can use an interstage fairing, problem solved.  Hell, we used to do that back in the day with structural plates or struts to make a cage interstage.

I think performance is a much better indicator of how the engine should be compared considering that engines come in all different sizes for a given performance/price, as is evident not only in real life but also in KSP.

See above.  Performance/price is what matters, not form factor.

If that was the case you wouldn't see so many people complaining about the 2.5 engine butts sticking out of the shuttle. 

 

Quote

       7 minutes ago, Tweeker said:

     The real problem is that SRBs are mis-sized to the role of lifting a 3m shuttle so the SSME ends up being OP to compensate

 

I don't agree and have seen no evidence of this claim.  Shoot, we got a few people in this thread arguing that the Vector is too powerful for Shuttle use, leading me to believe SRM performance has nothing to do with the engine.  Regardless of whether SRMs are underpowered, the Vector is its own thing.

  A few pages back Red Crown said the following:

Quote

 The real shuttle gets about 17% of its liftoff thrust from the LFO engines, the KSP equivalent gets about 70%.

 The Vector is OP having about 2.5x more thrust than it is "supposed" to have because the in game SRBs that are supposed to be analogous to Shuttle derived SLS SRBs are undersized and underpowered.

[GoSlash27]

48 minutes ago, Tweeker said:

That's all very true, but because it is packaged as a single engine, rather than a cluster of 3 on the rear of the shuttle it begs to be compared to the other engines that would fit in the same space. game wise.

Tweeker,

 That is merely an illusion based on visual appearance. Yeah, it *fits* in a 1.25m space, but it's a poor fit for a 1.25m engine. It's got great thrust (more than you could ever need), but it's too heavy and expensive to actually be useful behind a 1.25m load.

 It is a *cluster* engine that happens to fit in a 1.25m space. It's alright (and only just alright) in clusters because any cluster of Vectors can be outperformed by other engines that you already have by the time you unlock it. It's big downfall is it's cost, which can only be overcome by recovering it intact. This makes it a niche engine with very limited applications. It's great *if* you can cluster it and *if* you can recover it intact. Otherwise it sucks out loud. At least in career.

26 minutes ago, Tweeker said:

  The real problem is that SRBs are mis-sized to the role of lifting a 3m shuttle so the SSME ends up being OP to compensate.  

Yeah, this I agree with about 95%. Only 95% because the Kickback is still just barely good enough to do the job even with Skipper SSMEs. I would definitely prefer to have properly sized SRBs and nerfed SSMEs rather than underpowered SRBs and buffed Vectors.

Plus... bigger SRBs might be able to allow me to supplant LF&O boosters entirely. Disposable SRB clusters are fantastic for cheap booster designs.

Best,

-Slashy

 

 

[Temstar]

10 minutes ago, regex said:

I don't agree and have seen no evidence of this claim.  Shoot, we got a few people in this thread arguing that the Vector is too powerful for Shuttle use, leading me to believe SRM performance has nothing to do with the engine.  Regardless of whether SRMs are underpowered, the Vector is its own thing.

With the space shuttle stack, the two SRBs provide 83% of the thrust at lift off, the three RS-25 engines only provide 17% of the thrust. The story is similar with SLS, despite it having one more SSME it also uses a pair of even more powerful five segment SRBs. Basically those SRBs are enormously powerful machines, each putting out as much thrust as two F-1 engine of the Saturn V fame and the two SRBs together make up half of the weight of the shuttle stack at lift off.

What that mean is if you rearrange things, a single SRB makes a pretty good first stage (vibration not withstanding) for a heavy lift launch vehicle. Where as SSMEs are a bit too small and underpowered for replacement of something like a modern Saturn V first stage if not used with SRBs.

The story is the other way around in KSP, the biggest SRB, the Kickback is rather wimpy compared to the might that is Vector and Mammoth. This means Kickback is not very useful for heavy lift unless heavily clustered and Vector is overwhelmingly powerful when used on its own.

[regex]

31 minutes ago, Tweeker said:

If that was the case you wouldn't see so many people complaining about the 2.5 engine butts sticking out of the shuttle. 

Maybe the problem is engine tank butts...

Quote

The Vector is OP having about 2.5x more thrust than it is "supposed" to have because the in game SRBs that are supposed to be analogous to Shuttle derived SLS SRBs are undersized and underpowered.

23 minutes ago, Temstar said:

With the space shuttle stack, the two SRBs provide 83% of the thrust at lift off, the three RS-25 engines only provide 17% of the thrust. The story is similar with SLS, despite it having one more SSME it also uses a pair of even more powerful five segment SRBs. Basically those SRBs are enormously powerful machines, each putting out as much thrust as two F-1 engine of the Saturn V fame and the two SRBs together make up half of the weight of the shuttle stack at lift off.

The problem here is that you are equating a real life launch stack that uses liquid hydrogen/liquid oxygen engines, which generally have isps optimized for non-atmospheric conditions and that require powerful SRMs to get them up to optimum operating altitude (Ariane 5 does the same), with KSP's nebulous fuels that have a real life analog in storable hypergolics (specifically Aerozine50/N2O4) which are a far cry from, and provide much different performance characteristics, than volatile cryogenics.  If the STS used hypergolic engines those engines would be much, much more powerful than the SSME, in part because the fuel is more massive (but also far more dense) and would have much less in the way of isp.

In fact, the Vector is probably a good stand-in for a hypergolic SSME-alike.

KSP is not real life and, although we take cues from it, we cannot expect direct analogous performance.  If you insist on comparing KSP to real life, you need to address the elephant in the room.

Edited January 15, 2016 by regex

[Tweeker]

3 minutes ago, regex said:

Maybe the problem is engine tank butts...

The problem here is that you are equating a real life launch stack that uses liquid hydrogen/liquid oxygen engines, which generally have isps optimized for non-atmospheric conditions and that require powerful SRMs to get them up to optimum operating altitude (Ariane 5 does the same), with KSP's nebulous fuels that have a real life analog in storable hypergolics (specifically Aerozine50/N2O4) which are a far cry from, and provide much different performance characteristics, than volatile cryogenics.  If the STS used hypergolic engines those engines would be much, much more powerful than the SSME, in part because the fuel is more massive (but also far more dense) and would have much less in the way of isp.

In fact, the Vector is probably a good stand-in for a hypergolic SSME-alike.

KSP is not real life and, although we take cues from it, we cannot expect direct analogous performance.  If you insist on comparing KSP to real life, you need to address the elephant in the room.

     Everyone that insist on building a space shuttle clone in KSP is doing this, by insisting that they need the Vector to make their clone work, and that it *MUST*  be 1.25m so it looks like it's real world counterpart, but it *MUST*  have so much thrust to work with their space shuttle clone.

    What I'm saying is that by introducing this engine that fits in a certain space to be visually similar to a real world shuttle, but giving it enough thrust to work with in game SRBs you create an engine that isn't balanced with the in game engines.

[Temstar]

Isp and fuel is not an issue. For all we care LFO could be distilled unicorn blood and it wouldn't really make any difference. KSP engines can have arbitrary Isp as Squad see fit. I don't see anyone complain about Vector's relatively high Isp, particularly not after Squad made a point to mention staged combustion in the description.

The problem is that the SRBs in game are too weak to lift a big tank of LFO STS style and to make up the number Vector was made very powerful. Which is fine if all you want to make is shuttle replica as was the original intention. But then if you use the Vector on its own to make other types of rockets it's mentally jarring because it's too powerful for its diminutive size.

If instead we could have say, a 2.5m SRB that's big and beefy and up to the job then whatever engine we choose to represent KSP version of RS-25 could be made to be much weaker and more inline with the the actual shuttle layout and better match to its physical size.

Also, in real life fuel only affects Isp, you could very well make a huge cryogenic engine (eg, RS-68) with lots of thrust or a tiny hypergolic engine with very little thrust.

[Red Iron Crown]

The problem I see is that when used for its intended purpose it doesn't work all that well, IMO. If you build a Shuttle-style craft in the simplest way (Pod, large cargo bay and triple Vector assembly in the orbiter stack, LF tankage in a separate disposable stack, and two SRB stacks), the thrust offset is way too much. So you get this:

You can see the same in GoSlash's (much nicer) version posted earlier in the thread.

It's not a matter of scale or propellant choices, but that of the proportion of LFO thrust to SRB thrust in what is likely to be the most commonly-attempted configuration. The CoT direction is way different from the controlling part's orientation, so all those fancy SAS modes are close to useless, even MechJeb can't handle it. If you want to launch it straight up you need to mount it in launch clamps at a fairly alarming angle.

Compare it to something like the stock Slim Shuttle craft, which has a much larger fraction of its thrust delivered by the SRBs. Its CoT is much closer to the controlling part's direction; consequently the craft is much easier to fly.

I think this is the biggest reason that so many Shuttle-alike craft either use an engine under the fuel tank stack or cluster Kickbacks in 3s or 4s for the SRB part of the staging.

[regex]

41 minutes ago, Tweeker said:

What I'm saying is that by introducing this engine that fits in a certain space to be visually similar to a real world shuttle, but giving it enough thrust to work with in game SRBs you create an engine that isn't balanced with the in game engines.

But it is balanced with the other engines ... if you compare performance/price.

39 minutes ago, Temstar said:

Isp and fuel is not an issue. For all we care LFO could be distilled unicorn blood and it wouldn't really make any difference. KSP engines can have arbitrary Isp as Squad see fit. I don't see anyone complain about Vector's relatively high Isp, particularly not after Squad made a point to mention staged combustion in the description.

But they don't have an arbitrary isp; they are based on the theoretical maximums of Aerozine50/N2O4 engines.  The Vector doesn't even have very good isp numbers, 295 ~ 315?  That's a far cry from the SSME's 366 ~ 452.  Notice the difference there as well.  The actual SSME has a very wide power curve whereas the Vector's is relatively tight.  That is why one of the reasons why the STS needs those powerful SRMs.

Quote

The problem is that the SRBs in game are too weak to lift a big tank of LFO STS style and to make up the number Vector was made very powerful.

Citation please.

Quote

If instead we could have say, a 2.5m SRB that's big and beefy and up to the job then whatever engine we choose to represent KSP version of RS-25 could be made to be much weaker and more inline with the the actual shuttle layout and better match to its physical size.

There is no need to nerf the Vector as it works just fine in a variety of roles, although another SRM would be very welcome in the stock game.  Every time I load up vanilla after an update I pine for my procedural parts.

Quote

Also, in real life fuel only affects Isp, you could very well make a huge cryogenic engine (eg, RS-68) with lots of thrust or a tiny hypergolic engine with very little thrust.

No, fuel affects thrust as well.  Remember Newton's third law.  Hydrogen and oxygen are not massive at all compared to complex hypergolic molecules.  And while you are correct about the engines there, the fuel most definitely affects isp performance which is especially important deep within an atmosphere.

Edited January 15, 2016 by regex

[KerikBalm]

7 hours ago, Red Iron Crown said:

I think this is the biggest reason that so many Shuttle-alike craft either use an engine under the fuel tank stack or cluster Kickbacks in 3s or 4s for the SRB part of the staging.

For all the complaints about the kickback being underpowered... it really is as simple as what was said here... use more of them:

 

 

Since then, I made a 3x vector version using the supplied endplate. The Sea Level thrust of 3x vectors, being much greater than that of 1x KR-2L, had me use a cluter of 3 SRBs instead of two.. I don't see that as a problem, and in fact the 3x SRB cluster makes it look more like just one big SRB than the pairs of SRBs on each side.

We could use a 2.5m SRB (ideally with thrust vectoring), but for now, I don't see the big problem with simply using a pair of SRB clusters

Sea Level thrusts:

4x SRBs: 594 * 4 = 2,376

1x KR-2L= 1500

SRB engines % of SL thrust: 61.3%

 

6x SRBs: 594* 6 = 3,563 kN

3x vectors: 937*3 = 2811 kN

SRB engines % of SL thrust: 55.9%

Its true that my vector design does have more of a difference between the heading and the vector from the summed thrust... but its not nearly as bad as in that picture. My vector design does have much more fuel stored in the shuttle itself instead of the external tank though... more mass in the orbiter will compensate for more thrust on the orbiter. The orbiter will get much higher payload fractions that real life, but thats true of basically every launch vehicle design in ksp

[GoSlash27]

7 hours ago, Tweeker said:

     Everyone that insist on building a space shuttle clone in KSP is doing this, by insisting that they need the Vector to make their clone work, and that it *MUST*  be 1.25m so it looks like it's real world counterpart, but it *MUST*  have so much thrust to work with their space shuttle clone.

    What I'm saying is that by introducing this engine that fits in a certain space to be visually similar to a real world shuttle, but giving it enough thrust to work with in game SRBs you create an engine that isn't balanced with the in game engines.

Tweeker,

 Ah... but it *is* balanced with the other in- game engines. Going by mass and thrust it's right in between the Skipper and Mainsail, and is comparable to the engines used in the Twin Boar and Mammoth. Better Isp and gimballing in exchange for a crazy- high price tag.

 The problem isn't that it's OP as a KSP engine, but that it's overpowered as a SSME.

Best,

-Slashy

[NathanKell]

And, happily enough, as I said in this very thread it's not an SSME stat-wise. It's an RD-191 equivalent.
 Because as regex pointed out, in (stock) KSP it is literally impossible to have an SSME equivalent; the entire point of an SSME is that it is a high-efficiency sustainer that requires a volumetrically large, albeit light, propellant supply--one light enough that a mere two SRBs can lift it, with SSMEs' help.

 

@swjr-swis that's fair; I was unfairly sharp in my reply, and I apologize. My point only is, or was, that realism says "Vector is underpowered" not "Vector is overpowered".Trying-to-make-things-that-look-like-real-life-and-have-weird-versions-of-real-life-ratios says "no you must have weak sustainers" but...that ain't realism. :]

[Francois424]

Vector is often not worth it in my designs.   I've built Tylo landers, big, massive ore miners, Interplanetary ships...  Very rarely is the engine so OP that I want to use it on all my ships.
Cost is kind of irrelevant, late in tech tree means that it's seldom used in career if at all (like the Ion-engine since they moved it to the end-tree)

 - The weight makes it unpractical as a "extra-thrust" switch,
 - with the gimble/sas bug I worry of using on Kerbin (although restricting the Gimbal works... but not always, causing lots of reverting to launch/vab) ,
 - the ISP is good, but not spectacular, so It's not finding much use on my Interplanetary ships... I'll gladly stomach 30min burns if it means I double my Delta-V in the long run.

The best use I have found for the Vector is LF boosters.  Extremely good at that too !
I love the color/exhaust color/shape of the engine tho it looks awesome.

[Mad Rocket Scientist]

23 hours ago, MagicFireCaster said:

Looks pretty good and i like the fact you can stick it to a lot of surfaces, i wish other engines could do that 

The "Dart" toroidal aerospike is radially attachable, too.

[Tweeker]

15 hours ago, GoSlash27 said:

Tweeker,

 Ah... but it *is* balanced with the other in- game engines. Going by mass and thrust it's right in between the Skipper and Mainsail, and is comparable to the engines used in the Twin Boar and Mammoth. Better Isp and gimballing in exchange for a crazy- high price tag.

 The problem isn't that it's OP as a KSP engine, but that it's overpowered as a SSME.

Best,

-Slashy

  That is the root of the issue there, it is balanced with 2.5m engines , not with 1.25m engines. It needs to be a 2.5m engine.

   It is over powered as both, a KSP engine and a SSME, because it form is dictated by the desire t make it appear right with the shuttle, instead of making it fit in the existing range of engines. If you go by stats alone, NOT desired function it should be a 2.5m engine.

   As the old adage say form follows function, not the other way around.  

Edited January 16, 2016 by Tweeker

[GoSlash27]

7 hours ago, Tweeker said:

That is the root of the issue there, it is balanced with 2.5m engines , not with 1.25m engines. It needs to be a 2.5m engine.

I disagree. It is a 2.5m engine in all respects except the absence of a 2.5m butt plate, which is completely superfluous.
 If you simply *must* have a 2.5m butt plate on it in order to remind yourself that it's not actually a 1.25m engine, there is a simple fix:

Now it's a 2.5m engine. Problem solved.

 

7 hours ago, Tweeker said:

As the old adage say form follows function, not the other way around.  

 It's form does follow it's function. It's function is to be a SSME.

If it did not follow this form, it would be unable to perform it's function.

Best,
-Slashy

Edited January 16, 2016 by GoSlash27

[Frozen_Heart]

I think Squad needs to introduce 1.875m SRBs to match the shuttle. That way they can nerf the Vector enough to make it act more like a SSME rather than fill the role that its SRBs do in RL.

A 1.875m to 1.25/2.5m adaptor would need to go with this but that is only 3 parts total added.

The Vector can be brought down to about 700 thrust while the boosters have about 1.5k thrust each. Tapering thrust curve would be nice for the SRBs as well.