Anybody care for some asparagus?

[Starhawk]

I'm not really sure where (or if) to post this, but I thought it was a pretty good picture of asparagus staging.

[dryer_lint]

Heh. Asparagus is awesome, isn't it? Although it seems like the new aerodynamics will kind of ruin asparagus.

Also, from this top-down view, I just realized that the 3-man capsule looks a lot like Orion, doesn't it?

[Ippo]

Heh. Asparagus is awesome, isn't it? Although it seems like the new aerodynamics will kind of ruin asparagus.

Why would it? I use asparagus staging in FAR all the time with no issues, and I'd be surprised if the new stock aero was less forgiving than FAR...

As long as you keep your rocket symmetric across all staging events, you won't have any issue.

... unless you are referring to the need for asparagus staging, given we'll need less dV to orbit?

[Starhawk]

Although it seems like the new aerodynamics will kind of ruin asparagus.

I don't mind too much. I spent my first weeks playing by putting nosecones and adapters on all my rockets.

I do sometimes wonder if asparagus is used in the game to overcome some of the problems of the aerodynamic model. Will Eve be easier after the next update?

Also, from this top-down view, I just realized that the 3-man capsule looks a lot like Orion, doesn't it?

Interesting! I never noticed that.

[OhioBob]

Will Eve be easier after the next update?

We won't know until the update gets here, but if they reduce drag to a more realistic value, then it will surely make Eve easier. That is unless they change something else that increases the Eve difficulty (such as reducing ISP at pressures >1 atmosphere).

[Starhawk]

We won't know until the update gets here

Of course. It was basically rhetorical.

such as reducing ISP at pressures >1 atmosphere.

This is something I've been wondering about a lot. KER displays no effect on ISP or delta-v from other atmospheres.

Does the model used by the game simply max out the ISP inefficiency calculation at one atmosphere?

[Red Iron Crown]

Does the model used by the game simply max out the ISP inefficiency calculation at one atmosphere?

It does. Engines' Isps get no worse than at sea-level Kerbin.

[forenci]

Ah, it's been a long time since I've done some legit asparagus. Ever since adding lots of mods I've found it to be less necessary (more parts to overcome the need for asparagus). Plus the challenge of building streamlined rockets is quite fun too. Although asparagus was always frustrating to make sure those fuel lines/staging were set up properly.

[Starhawk]

It does. Engines' Isps get no worse than at sea-level Kerbin.

That is ... unfortunate. It kind of destroys the whole point of modeling ISP, as far as Eve is concerned.

On the other hand, if they ever fix this, it could make Eve return much harder (impossible?). Maybe the aero update improvements would balance it out.

- - - Updated - - -

asparagus was always frustrating to make sure those fuel lines/staging were set up properly.

I found that the new edge highlighting makes it much easier to set up the staging.

[forenci]

I found that the new edge highlighting makes it much easier to set up the staging.

That's true. I hadn't even thought of that since the most recent update. It was pretty much a guarantee that I would have to re-stage/set fuel lines at least 3-4 times before finally getting it right.

You kids have it too easy these days with your fancy highlighting!

[problemecium]

I wouldn't worry terribly about the new aerodynamics messing up Asparagus. Similar concerns existed when the SLS parts came out, and people simply built really big asparagus rockets. The simplest solution might just be to stick nose cones atop all the "stalks", or perhaps have a big nosecone on the front of the rocket that covers them up.

[Red Iron Crown]

I wouldn't worry terribly about the new aerodynamics messing up Asparagus. Similar concerns existed when the SLS parts came out, and people simply built really big asparagus rockets. The simplest solution might just be to stick nose cones atop all the "stalks", or perhaps have a big nosecone on the front of the rocket that covers them up.

Or both!

[sal_vager]

How to prepare asparagus in 0.91.0

1 cup command parts, whole.

1 cup Kerbals, scared.

2 boosters per person, I like to add an extra 2 in case anyone is extra hungry.

Equal number of nosecones to boosters.

Season with fuel lines and struts to taste.

Serve with rocket

[UmbralRaptor]

I do sometimes wonder if asparagus is used in the game to overcome some of the problems of the aerodynamic model.I never noticed that.

Asparagus is widely used because it's hard to get high TWR and mass ratios in KSP, but fuel lines are easy. In real life it's the reverse.

[Starhawk]

Or both!

That is a thing of beauty! Do you use it with FAR?

[OhioBob]

That is ... unfortunate. It kind of destroys the whole point of modeling ISP, as far as Eve is concerned.

On the other hand, if they ever fix this, it could make Eve return much harder (impossible?). Maybe the aero update improvements would balance it out.

If we really want ISP to be realistically modeled, there's a lot of rebalancing that needs to be done. To really do it right, there should be two classes of engines - small expansion ratio and large expansion ratio. Small expansion ratios are used at low altitude where the ambient pressure is high, and large expansion ratios are used at high-altitude or in space where the ambient pressure is at or near zero. A small expansion ratio engine might have a sea level/vacuum ISP balance of something like 260/300 s, while a large expansion ratio engine might be something like 100/350 s. These are basically real life values, in KSP specific impulses are a little higher than real life (assuming LOX/kerosene).

In KSP engines are balanced in such a way that that we get the best of both worlds - both good sea level and good vacuum performance. Of course this is the theory behind aerospike engines. An aerospike performs like a variable expansion ratio engine, obtaining small expansion ratio like performance at low altitude and large expansion ratio like performance at high altitude. In this regard, all engines in KSP behave like aerospikes, except, of course, the toroidal aerospike rocket. The in-game aerospike gives a vacuum-like performance at all altitudes, which isn't analogous to any real life engine.

[Red Iron Crown]

That is a thing of beauty! Do you use it with FAR?

Thanks! I don't use FAR, stock aero user here. It was just an experiment to see if a somewhat aerodynamic Eve ascent vehicle could be built. The TWR is marginal for the early stages though, and the odds of keeping it upright on landing with my piloting skill is virtually nil.

Eve ascent is about to get much more difficult with the new aero model, I suspect.

[Starhawk]

If we really want ISP to be realistically modeled, there's a lot of rebalancing that needs to be done. To really do it right, there should be two classes of engines...

I understand the need for compromises in simulations, but I'm for more realism, if it works. Interesting info, Bob. Thanks. Of course, as Scott Manley pointed out in one of his videos, if we want to model ISP realistically, thrust should change, rather than fuel consumption. But, again, I understand the need for tradeoffs. I would imagine there are mods that attempt to rebalance the engine ISP's to make them more realistic.

- - - Updated - - -

... the odds of keeping it upright on landing ...

I would also think that landing on those engines might be a problem. The one time I tried an Eve lander using engines for landing legs, the gravity and pressure ripped the tanks from the engines due to the gentle slope.

Eve ascent is about to get much more difficult with the new aero model, I suspect.

I've been thinking along these lines. I'd really like to complete the Eve Rocks challenge within the rules before the next update.

[TheBlueJay]

I actually find asparagus staging almost like cheating (no offense to those who do it!) as it makes getting to orbit fairly easy. I prefer to make realistic-like rockets that can get to orbit using traditional staging methods used in real-world spacecraft.

Not saying I won't use it combined with HyperEdit when I'm lazy

[OhioBob]

I understand the need for compromises in simulations, but I'm for more realism, if it works. Interesting info, Bob. Thanks. Of course, as Scott Manley pointed out in one of his videos, if we want to model ISP realistically, thrust should change, rather than fuel consumption. But, again, I understand the need for tradeoffs. I would imagine there are mods that attempt to rebalance the engine ISP's to make them more realistic.

I too understand the tradeoffs. It looks like the developers gave us a nice assortment of engines with different thrusts that could be used in a wide range of applications. If they started modifying the ISPs to be more realistic, they'd have to start adding engines - a group for use on the lower stages and another group for use on the upper stages. Personally, I would be happy to see that, but I understand the reason for not overcomplicating it. The thrust/fuel flow issue is one that I've seen many people complain about. It bothered me at first but I just learned to live with it. All these issues would probably bother me a lot more if I were a FAR user and striving for maximum realism, but so far I've only played stock while waiting to see what Squad does with the update. If Squad does decide to make changes to ISP, I hope they do it across the board and fix everything. If they fix one thing and not something else, then the thing they didn't fix will probably bug more than if they did nothing at all.

[Renegrade]

I understand the need for compromises in simulations, but I'm for more realism, if it works. Interesting info, Bob. Thanks. Of course, as Scott Manley pointed out in one of his videos, if we want to model ISP realistically, thrust should change, rather than fuel consumption. But, again, I understand the need for tradeoffs. I would imagine there are mods that attempt to rebalance the engine ISP's to make them more realistic.

There's absolutely zero need for any 'tradeoffs' for the thrust-varies-with-ISP system. The flow-varies-with-ISP calculations that stock uses are in fact slightly more expensive and slightly more complex than the correct code. There's at least a half dozen mods out there that incorporate that, plus many of them do the extend-to-zero thing.

The real tradeoff here is that someone is trading off correct thrust calculations vs. the terrible, horrible, traumatizing ordeal of loading a file and changing between 1 and 5 lines.

(Also before anybody brings up it ruining gameplay, there's essentially two classes of people who would be affected by any change: the first group is the 'moar boosters' kind. If their TWRs on the launchpad fell a bit, they'd simply go 'whoops' and slap on, you guessed it, moar boosters...assuming their launchpad TWR was like 1.15 to begin with, which is unlikely. The second class of people, who calculate TWR, would simply adapt their math and/or software tools and carry on without missing a beat)

[Xavven]

If we really want ISP to be realistically modeled, there's a lot of rebalancing that needs to be done. To really do it right, there should be two classes of engines - small expansion ratio and large expansion ratio. Small expansion ratios are used at low altitude where the ambient pressure is high, and large expansion ratios are used at high-altitude or in space where the ambient pressure is at or near zero. A small expansion ratio engine might have a sea level/vacuum ISP balance of something like 260/300 s, while a large expansion ratio engine might be something like 100/350 s. These are basically real life values, in KSP specific impulses are a little higher than real life (assuming LOX/kerosene)

It always bothered me that the LV-909 has a short nozzle and yet has a high vacuum Isp. I get that it's supposed to be a short, squat engine that can be used on landers with small landing legs, but a short nozzle like that would produce a grossly underexpanded exhaust and give terrible vacuum Isp.

[Alshain]

Asparagus works just fine in FAR, I don't see how what Squad has planned would change that. FAR just makes it less necessary, so you only use it on really large lifters.

[OhioBob]

It always bothered me that the LV-909 has a short nozzle and yet has a high vacuum Isp. I get that it's supposed to be a short, squat engine that can be used on landers with small landing legs, but a short nozzle like that would produce a grossly underexpanded exhaust and give terrible vacuum Isp.

There are several things that visually don't make a lot of sense in terms of realism. For instance, the LV-T30 and the LV-T45 are essential the same engine, yet, when compared side-by-side, the LV-T30 has a much larger nozzle. I could point out other things as well. I try not to let stuff like this bother me. I'm sure the artists had to make the engines look different enough that a player could easily distinguish between them. And as you say, there's a need to make some engines squat to fulfill certain roles. As much as some people want realism, KSP is a game first, thus some compromises have to be accepted for the sake of game play.

[problemecium]

I just figure the LV-909 produces its high Isp by doing something differently from the T30 and T45 internally. So it stands to reason that if we tried whatever that is on the larger engines, their Isp could be much better.