LV-1 engine, does it need an ISP boost, or am I missing its use?

[GoSlash27]

I'm solidly with the majority on this one.

It's not that the LV-1 is bad, but rather the 48-7S is too good.

This is also aggravated by the lack of fuel tanks in the proper range to feed an LV-1. In the rare situation that the LV-1 is the most attractive choice, the heavier and more expensive tanks in it's range wind up tipping the balance back in favor of the 48-7S.

Best,

-Slashy

- - - Updated - - -

I think you need to check again. And remember, the fair comparison isn't to merely change the engine on an otherwise-identical lander, but to change the engine AND the amount of fuel to meet the target delta-V and TWR, then compare the masses. Do that and it's very rare for the 909-engined design to turn out lowest mass. Of course mass isn't the only design consideration.

Agreed. Even on Tylo, the 48-7S yields a smaller and cheaper ascent stage than the LV-909.

Assuming a 1 tonne payload the 48-7S can do the job for 1.63 tonnes and $1,235.

The LV-909 needs 2.02 tonnes and $1,424.

Best,

-Slashy

Edited January 6, 2015 by GoSlash27

[Renegrade]

Heavier lander? The only way you can get more deltaV out of a 48-7s than a LV-909 and >1 TWR on the Mun is with a command chair. The ISP just isn't there. The 48-7s is great for many things, but returning kerbals from gravity wells isn't one of them. Light landers are fine.

My Tylo lander disagrees but that's a whole other kettle of fish.

Here's a specific example of a Mun lander (dates back to 0.24, since I was lookin' at my last Eve landing - I used a mix of aerospikes and T30s there btw):

R8 MunLandR (Reusable long-range munlander, designed to deploy from a Mun orbital station or Apollo-like CSM, while performing fairly large inclination changes and long hovering. This is NOT a light ship):

Mass: 3,810 kg

ISP: 350.0s

TWR(Mun): 4.84

Delta-V: 2,556

Since it's re-usable, it's a single stage, carrying two fuel tanks and a full science suite (excluding things that are irrelevant on the Mun, like the nosecone sensor).

Now I swap out the single 48-7S for the LV-909:

Mass: 4,210 kg (Mass increased by 400kg)

ISP: 390.0s

TWR(Mun): 7.29

Delta-V: 2,466 (Delta-V fell by 90)

Swapping to a pair of 48s gives the 909 the advantage by 6 delta-v, although the resulting mass is still lighter, meaning lower stages will be better. Plus the TWR is then better in the dual 48-7S model.

(you do NOT want to know what happens if you use a Mun lander designed for efficient landings and less hovering etc)

[note: according to kerbal engineer you shouldn't use the poodle on Eve. Use 4 LV-909s instead].

O.o

Oh, you must be talking about an atmospheric number (the 909 has slightly better atmospheric performance than a Poodle for whatever arbitrary reason). The Poodle's definitely better than four 909s, even if you do cheat 'em on with massless parts, when in space or upper atmospheres.

While the LV-1 could really use an ISP buff, most of the cult of the 48-7s is assuming that the mass empty part of the rocket equation will be similar on other craft as it is to the last probe stage.

That's the problem though: the 48-7S's mass IS extremely low, and results in a very low dry mass except on the tiniest of probes (like the #lolmassless one I used for Eve, or the #lolmassless ones I use for satellite contracts, both of which are ant-powered in the final stage). The ant is 30kg, and the 48-7S is 100kg. On the other hand, the 48-7S is like 90% of the ISP of the top conventional engines, and the Ant is only 83% of the 48-7S. (and the 48-7S is five times lighter than the 909, vs. only 3 1/3 for the ant vs. the 48).

If you look at engine niches, it's something like this for conventional drives (ignoring nukes and ions):

1 = ant (LV-1)
4 = 48-7S
9 = 909
P = poodle
<-- tiny    big-->
114444444444444444444444444499PPP...

What I would like to see is more like this:
111111111144444444449999999999PPP...

(code block, because monospaced font~)

That way, the niches are more even. Note that when TWR demands come into play, the 48-7S's niche BROADENS, not shrinks, seeing as it's better than a Mainsail and the 909 is worse than anything else conventional in terms of TWR.

TL;DR version: I don't want to remove the 48-7S from all consideration, just shrink it's niche, thus allowing others to grow, without needless ISP buffing that will make every drive have 370 isp.

[wumpus]

I think you need to check again. And remember, the fair comparison isn't to merely change the engine on an otherwise-identical lander, but to change the engine AND the amount of fuel to meet the target delta-V and TWR, then compare the masses. Do that and it's very rare for the 909-engined design to turn out lowest mass. Of course mass isn't the only design consideration.

Checked and edited. I'm surprised that the LV-909 doesn't do better, but still looks like the best for transfer burns. Also I suspect my next lander might still use the LV-909 (due to wimping out on docking and hauling the mobile lab down to minmus).

So far the 48-7s replaces:

LV-1 (for anything that you might want an LV-1 for)

LV-909 (although not all the time due to the ISP factor).

aerospike (if you won't use it on Eve, why would you want one?)

Of these, only the LV-909 seems to show up sufficiently earlier on the tech tree for a somewhat expected replacement.

[Renegrade]

LV-1 (for anything that you might want an LV-1 for)

Not entirely. It's like the 909: It gets edged out by the 48-7S in MOST situations, but not all.

There's still some edge cases where the ridiculous massless parts and superlight probes can make do with anty goodness. A moderate 48-7S nerf would expand those situations some.

aerospike (if you won't use it on Eve, why would you want one?)

The aerospike is a fat, weak, miserable engine. It used to be one of the best in the game, but complaining was had, and nerfs came with Squad heavy-handedness and now it's the worst~

(That's a tricky one to balance though as atmospheric Isp means less than most people think..)

[Empiro]

Also put me in the list of "48-7S is too good". All you really need to do is to look at the optimal engine graphs linked by smartech below to see it. The 48-7S occupies a huge middle region in every single graph. No other engine is like this.

No, the 48-7S isn't always the best, but it is the best in significantly more circumstances than any other engine in the game.

I recommend reading those wonderful charts optimal engine choice for desired TWR and delta-v.

http://imgur.com/a/iNqmQ

Generally, the LV-N is usefull for bigger craft with lots of fuel, which would ammortize its large weight.