Squad Should Re-Balance the Poodle Engine

[Tweeker]

I don't care whether my landers are super-optimal, only that they work nicely and have a comfortable margin of excess dV and excess power (only just enough is bad design in my book, as this is KSP and not a NASA mission where min-maxing is actually important).

I agree with you on this also, I like to have a little extra Delta/v in the bank. I'm certainly not here to tell you how to have fun. KSP is a game in the end, and is not about optimal. I only mean to say that unless you build a really heavy lander, the Poodle can be swapped for an aerospike, or a LV-909, and you gain more Delta/v, and end up with a lighter lander. It's not wrong to use a poodle, but with very little change to the lander you can lower the weight by about 20%, and maintain the same form. If you want to use the poodle in this roll it works reasonably well. You just end up needing a bigger rocket to put it where ever it's going.

[Jouni]

The first stage is:

4X aerospike plus 810 fuel, or 2 Ft-L800 and 1 Ft-L200 each.

46.7T

Twr 1.0

Delta/v 2693

burn time 2 min 53 sec.

The second stage is:

1 LVT-30, plus 3 FT-L800s.

14.6T

Twr .9 *

Delta/v 2093*

burn time 3 min 19 sec.

By the time you light this stage the twr will have increased to .99 and the Delta/v will have climbed to 2400.

Did you actually try this thing?

I built it, and the mass was 71.6 tonnes with 1.25 m probe core and reaction wheels and the most lightweight radial decouplers. Due to having TWR 1.00, the rocket just hovered between the launch clamps for a while. During the initial ascent, the rocket was extremely uncontrollable due to having minimal reaction wheels and no thrust vectoring. It reached the altitude of 1 km at 01:02. At 02:42, it had reached 10 km. The first stage burned out soon after 15 km. The highest altitude reached by the second stage was somewhere between 20 km and 25 km, before it started to fall.

Sitting under a 10T payload this would have a TWR of 1.06, If you change to a LV-T30 it would have a TWR of .99, but with the LV-T30 you can add another 45 fuel, to end up at the same weight, with a little more Delta/v than the poodle, not to mention the cost savings.

The LV-T30 doesn't have thrust vectoring, so the upper stage would also need more reaction wheels than the probe core has. And because 1.25 m parts have weaker connections than 2.5 m parts, you also need to use struts to secure the upper stage.

Of course, using a tall 1.25 m engine in a 2.5 m stage looks silly, unless you use fairings, which also add mass.

[Tweeker]

Did you actually try this thing?

I built it, and the mass was 71.6 tonnes with 1.25 m probe core and reaction wheels and the most lightweight radial decouplers. Due to having TWR 1.00, the rocket just hovered between the launch clamps for a while. During the initial ascent, the rocket was extremely uncontrollable due to having minimal reaction wheels and no thrust vectoring. It reached the altitude of 1 km at 01:02. At 02:42, it had reached 10 km. The first stage burned out soon after 15 km. The highest altitude reached by the second stage was somewhere between 20 km and 25 km, before it started to fall.

I built it and flew it, How do you think I got the TWR, and D/V figures for the 2nd stage when it lights VS sea level? It is very difficult to fly, I'm not sure how you're flying it, but you have to turn very late, above 20km. The 1.0 TWR isn't far off from the poodle top stage you describe, poodle & X200-16 So it should fly about the same. If you burn the center engine at about 20% thrust the ascent goes easier, or you could add fuel ducts. If that isn't working for you can add LV-30s or 45s instead of aerospikes. This gives you a higher TWR, so you get to about 25 KM on the 1st stage. I just flew this, and it weighs about 1T less, but is easier to fly.

My point here is that there are a lot of alternatives to the poodle. Some similarly hard to fly, and some that fly easier.

The LV-T30 doesn't have thrust vectoring, so the upper stage would also need more reaction wheels than the probe core has. And because 1.25 m parts have weaker connections than 2.5 m parts, you also need to use struts to secure the upper stage.

Of course, using a tall 1.25 m engine in a 2.5 m stage looks silly, unless you use fairings, which also add mass.

An inline stabilizer adds only .1T, which still leaves the stage lighter than one with a poodle, or you can use an LV-T45 and have vectoring. The 10T payload does not need to be 2.5M a number of long distance missions can be built for 10T with 1.25M parts. So there is no need to worry about having an hourglass rocket or changing from 2.5m to 1.25m. Unless you are getting really crazy with your rocket a 1.25M coupler will serve just fine.

Edited November 29, 2014 by Tweeker

[King Arthur]

Any engine can be used for landing as long as it provides enough TWR.

Besides the LV-909, Aerospike, Poodle, 48-7S, and the Ion (?!) engine, most of the other engines are too tall to be practical for landers and/or have terrible ISP.

But for most bodies the Poodle is way overpowered as a landing engine (the Poodle on that lander has a TWR of 14 on the Mun).

I see that as a benefit, I have the option of unloading a TWR of 14 should the need for such a thing arise. Having too much TWR is never a bad thing.

In most cases it is more ligitemate to use a smaller, less massive and cheaper engine that gets you more delta-v than the Poodle.

The one reason left to use the Poodle on a lander is that it fits nicely in a 2.5m stack. But "it looks nice" should not be a reason for choosing an otherwise far sub-optimal part.

The Poodle is the go-to engine for a 2.5m lander owing to the Poodle's 2.5m + low-profile form factor. If you want to min-max like you're playing a serious-business-mode MMO, all the more power to you, but I want to build and fly rockets that are aesthetically pleasing. I don't consider a 48-7S stuck onto a 2.5m fuel tank nor a huge cluster of 48-7Ss to be aesthetically pleasing.

[Jouni]

I built it and flew it, How do you think I got the TWR, and D/V figures for the 2nd stage when it lights VS sea level? It is very difficult to fly, I'm not sure how you're flying it, but you have to turn very late, above 20km. The 1.0 TWR isn't far off from the poodle top stage you describe, poodle & X200-16 So it should fly about the same. If you burn the center engine at about 20% thrust the ascent goes easier, or you could add fuel ducts. If that isn't working for you can add LV-30s or 45s instead of aerospikes. This gives you a higher TWR, so you get to about 25 KM on the 1st stage. I just flew this, and it weighs about 1T less, but is easier to fly.

I tried it again a few times with the gravity turn starting after 20 km. The rocket was always around 200-300 m/s short of reaching orbit. Can you give me precise instructions on how the rocket is supposed to reach orbit?

When I switched the engines to LV-T30s, the rocket reached orbit easily enough.

My point here is that there are a lot of alternatives to the poodle. Some similarly hard to fly, and some that fly easier.

None of the alternatives are 2.5 m engines, which is the point. The Poodle is useful as a 2.5 m upper stage engine with its current stats, and there are no other 2.5 m engines that could replace it.

The 10T payload does not need to be 2.5M a number of long distance missions can be built for 10T with 1.25M parts. So there is no need to worry about having an hourglass rocket or changing from 2.5m to 1.25m. Unless you are getting really crazy with your rocket a 1.25M coupler will serve just fine.

If I want to launch a 2.5 m payload, launching an 1.25 m payload usually doesn't help.

[Joonatan1998]

While I agree that building good looking landers important, and have used the poodle for that purpose, I think that it should be buffed.

Then we could build landers that both have good performance and don't look like random 48-7SW spam.

[King Arthur]

Personally, I believe the problem lays more in the 48-7S's ludicrous effectiveness. The 48-7S, if we're going strictly by numbers with no regard given to form factor or part count, renders both the Poodle and LV-909 completely and entirely obsolete and renders the entire line of probe-oriented small engines useless with the exception of the ion engine.

In my opinion this isn't a problem with the Poodle being underpowered, it's the 48-7S being so supremely overpowered that it has ended up being overbearing. You hear it constantly in this thread and elsewhere, "just tack on a 48-7S instead and you'll get better numbers than <engine>".

I remember playing 0.20 many many months ago when we didn't have the 48-7S yet, and as far as I can recall now the go-to lander engines were in fact either the Poodle or LV-909 and maybe the Aerospike if you wanted more power than a 909. Once the 48-7S rolled around in 0.21 or whatever it was though, it just ended up blasting everything else out of the water.

Edited November 29, 2014 by King Arthur

[Tweeker]

I tried it again a few times with the gravity turn starting after 20 km. The rocket was always around 200-300 m/s short of reaching orbit. Can you give me precise instructions on how the rocket is supposed to reach orbit?

When I switched the engines to LV-T30s, the rocket reached orbit easily enough.

I'd rather not get side tracked into a discussion of how to build an optimal 10T 1.25M lifter, you can build various ones that replaces the Poodle, In 2.5M 10T lifters the Skipper can replace and out perform the Poodle, as in the example I cited earlier.

Personally, I believe the problem lays more in the 48-7S's ludicrous effectiveness. The 48-7S, if we're going strictly by numbers with no regard given to form factor or part count, renders both the Poodle and LV-909 completely and entirely obsolete and renders the entire line of probe-oriented small engines useless with the exception of the ion engine.

In my opinion this isn't a problem with the Poodle being underpowered, it's the 48-7S being so supremely overpowered that it has ended up being overbearing. You hear it constantly in this thread and elsewhere, "just tack on a 48-7S instead and you'll get better numbers than <engine>".

I remember playing 0.20 many many months ago when we didn't have the 48-7S yet, and as far as I can recall now the go-to lander engines were in fact either the Poodle or LV-909 and maybe the Aerospike if you wanted more power than a 909. Once the 48-7S rolled around in 0.21 or whatever it was though, it just ended up blasting everything else out of the water.

I agree with this completely, the 48-7S is completely out of wack, it relegates a lot of engines to 2nd tier, the poodle being one of them. But it's not the only one that has this effect on the poodle. There are about 6 engines that you can use instead, depending on the roll.

1) At the low end of the spectrum is the 48-7s which can replace it in landers.

2) The LV-909 can replace it in transfer stages, landers & sometimes lifters.

3) The aerospike can replace it in landers, lifters and transfer stages depending on form.

4) The LV-T30

5) & the LV-T45 can replace it in lifters for 1.25M payloads or 2.5 M if you're not picky about form.

6) The Skipper can replace it in lifers with 2.5M payloads or 1.25M payloads.

And that is really the point I'm trying to make here, it is in the middle of the pack in a lot of ways, If you adjust it's thrust, and maybe TWR it can rise out of the pack into a roll of it's own.

[Jouni]

I'd rather not get side tracked into a discussion of how to build an optimal 10T 1.25M lifter, you can build various ones that replaces the Poodle, In 2.5M 10T lifters the Skipper can replace and out perform the Poodle, as in the example I cited earlier.

You gave an example of a badly designed rocket that became a bit less bad, when you removed the completely unnecessary third stage and added a bit more fuel to the second stage. The same rocket will also reach orbit, if you remove the Skipper and split the middle stage fuel evenly between the Mainsail stage and the Poodle stage. In my test flight, I reached a 100 km orbit with enough fuel left for deorbiting the upper stage and the payload, even though the ascent profile was quite bad.

[Ravenchant]

The one reason left to use the Poodle on a lander is that it fits nicely in a 2.5m stack. But "it looks nice" should not be a reason for choosing an otherwise far sub-optimal part.

Oh shoot, turns out I've been playing KSP wrong all this time!

[rkman]

Having too much TWR is never a bad thing.

It wouldn't, if cost would not be an issue.

Oh shoot, turns out I've been playing KSP wrong all this time!

Yeah, if you want to play a fashion show, you'll have to pick another game.

For those who cares about asthetics over performance: what stake do you have in a discussion about changing the performence (rebalancing) of engines?

Edited November 29, 2014 by rkman

[Tweeker]

You gave an example of a badly designed rocket that became a bit less bad, when you removed the completely unnecessary third stage and added a bit more fuel to the second stage. The same rocket will also reach orbit, if you remove the Skipper and split the middle stage fuel evenly between the Mainsail stage and the Poodle stage. In my test flight, I reached a 100 km orbit with enough fuel left for deorbiting the upper stage and the payload, even though the ascent profile was quite bad

The example rocket wasn't designed with any malice, only to try the poodle in a way you suggested, but it does show that the poodle is really only useable with 1, maybe 2 fuel tank configurations. The only reason it works at all is because there is a mainsail below it. The first stage practically sets is into orbit. If you use a skipper & mainsail the rocket flys much easier than with a poodle. Or you can a skipper and some 1.25m boosters, and again it is easier to fly.

The poodle is much more useable if you double the thrust and weight, It's burn time is much faster so you can burn closer to apoapsis, and use your Delta V more efficiently. A "double poodle" is also much easier to fly, as the TWR of the rocket is higher. It's stage is taller, so it looks better with 1.25m radial boosters. It is easier to adjust the burn time of the engine, stock it burns the smallest 2.5m tank in 1 minute 10 sec, so this is the basic unit you can tune the thrust in. A "double poodle" burns in half the time, so it is much more tunable.

There are a lot of benefits to raising the poodle's thrust, but it causes very few problems.

[Murph]

There are a lot of benefits to raising the poodle's thrust, but it causes very few problems.

WRONG! Doubling the weight of it causes a major problem with one of the primary use cases for it, as a 2.5m lander engine. Despite the claims to the contrary, it is not badly sub-optimal on 2.5m landers, and actually works very nicely there. Increasing the weight of it significantly would steal an unacceptable amount of dV from landers, and actually turn it into a horrible engine for use on landers, as well as leaving no available 2.5m engine for lower thrust cases.

Leave the Poodle alone, either use the Skipper (which works perfectly well when you exceed the capabilities of the Poodle), or campaign for a 4th 2.5m engine if you really can't make the Skipper work. There is very much a major downside to basically removing the Poodle from the game, which is what you are asking for at the end of the day  remove the Poodle and replace it with the engine that you want because you don't like using the Skipper.

I'll say it again: The problem you are having with the Poodle is not caused by the Poodle, but by problems with your design. The Poodle is not intended to be used the way that you are trying to use it, use the Skipper instead.

[Jouni]

The example rocket wasn't designed with any malice, only to try the poodle in a way you suggested, but it does show that the poodle is really only useable with 1, maybe 2 fuel tank configurations. The only reason it works at all is because there is a mainsail below it. The first stage practically sets is into orbit. If you use a skipper & mainsail the rocket flys much easier than with a poodle. Or you can a skipper and some 1.25m boosters, and again it is easier to fly.

I was suggesting to use the Poodle in a well-designed 2-stage or 2.5-stage rocket, not in an inefficient 3-stage rocket. Removing the Skipper makes the rocket better than removing the Poodle, because it removes a tonne of useless engine mass. The Poodle would also work, if you replaced the large Mainsail stage with a smaller Skipper stage and some strap-on boosters.

The poodle is much more useable if you double the thrust and weight, It's burn time is much faster so you can burn closer to apoapsis, and use your Delta V more efficiently. A "double poodle" is also much easier to fly, as the TWR of the rocket is higher. It's stage is taller, so it looks better with 1.25m radial boosters. It is easier to adjust the burn time of the engine, stock it burns the smallest 2.5m tank in 1 minute 10 sec, so this is the basic unit you can tune the thrust in. A "double poodle" burns in half the time, so it is much more tunable.

A double Poodle would be inferior to the Skipper in almost every case. In general, Isp means nothing. If you adjust it 10% up or down, it doesn't affect anything in sub-3000 m/s stages. Thrust also means nothing, as long as you have enough of it. Engine mass is everything. Every tonne of engine means that your rocket can lift one tonne less. That's why you always choose the smallest suitable engine, if you care about efficiency.

[Tweeker]

WRONG! Doubling the weight of it causes a major problem with one of the primary use cases for it, as a 2.5m lander engine. Despite the claims to the contrary, it is not badly sub-optimal on 2.5m landers, and actually works very nicely there. Increasing the weight of it significantly would steal an unacceptable amount of dV from landers, and actually turn it into a horrible engine for use on landers, as well as leaving no available 2.5m engine for lower thrust cases.

If you care about weight, and performance there a lot of better choices of a 2.5m lander;

The LV-909, Aerospike, Rapier, LV-T30, LV-T45, and 48-7S all provide better delta v and a lighter rocket.

The LV-909 is also more tunable by adding 2,3 or 4 on Bi- Tri- or Quadstack adapters, or radially. Both in terms of thrust and Fuel volume. The same is true for the 48-7S.

The lv-1R, and 24-77 can be mounted radially and provide better Delta V in a lighter rocket.

Or you can switch to monopropellant and use the O-10 and have an even lighter lander, or fatten it up to 10 tons and have more delta v than with even a 48-7S. or about 30% more than with a poodle.

If it's aesthetics you care about, many of these are just as good a Poodle. Either way a Poodle is not a stand-out choice for a 2.5M lander.

[Tweeker]

I was suggesting to use the Poodle in a well-designed 2-stage or 2.5-stage rocket, not in an inefficient 3-stage rocket. Removing the Skipper makes the rocket better than removing the Poodle, because it removes a tonne of useless engine mass. The Poodle would also work, if you replaced the large Mainsail stage with a smaller Skipper stage and some strap-on boosters.

A double Poodle would be inferior to the Skipper in almost every case. In general, Isp means nothing. If you adjust it 10% up or down, it doesn't affect anything in sub-3000 m/s stages. Thrust also means nothing, as long as you have enough of it. Engine mass is everything. Every tonne of engine means that your rocket can lift one tonne less. That's why you always choose the smallest suitable engine, if you care about efficiency.

The extra ton is a red herring as the poodle can't lift the extra ton. Removing the Skipper for a Poodle results in a rocket that is 1 ton lighter, but the Poodle can't use this extra ton. If you replace it with fuel the Poodle's TWR drops below 1 even by the time the second stage lights. So it will slow down, and fail to make orbit. Adding the extra ton of fuel to the 1st stage has a negligible, only 30 M/S or .75% increase. The Poodle wastes far more than this with it's poor ascent profile.

In fact it wastes all it extra Delta/v it has, because it has to burn a lot longer than the Skipper, it accelerates slower, so it spends more time in the atmosphere, and the velocity vector comes down more so it spends even more time in the atmosphere. Even beyond the atmosphere it has to burn longer to deliver the delta/V. So it is farther from apoapsis for the beginning and end of the burn, meaning the thrust is less effective at raising periapsis above the atmosphere.

Beyond the numbers the skipper stage is easier to fly, so you can more reliably make orbit. It is also more tunable for payload both larger and smaller. And that is just considering the Skipper with the same fuel balance between the stages, If you re-balance the fuel so the mainsail burns out sooner, and the skipper burns longer you gain more delta/v. Of course there is some trade off, but the skipper remains superior.

As you said, as long you have enough thrust, choose the smallest engine. But the poodle doesn't have enough thrust.

Edited December 1, 2014 by Tweeker

[SubzeroSpartan7]

As far as I know tweakScale still messes up the TWR of engines. As a default, part mass has a scaleExponent of 3 and thrust has 2. The consequence is that scaling to half size will double the TWR of an engine. This bug makes shrinked engines extremely powerful and enlarged ones pretty much unusable. So your 1.25m poodle is probably more powerful than the boost Steambirds asks for.

It does in fact do that. It becomes really apparent when scaling larger engines to smaller sizes.

[Jouni]

If you replace it with fuel the Poodle's TWR drops below 1 even by the time the second stage lights. So it will slow down, and fail to make orbit.

TWR 1 is not a magic number you need to reach orbit. In many cases, upper stages are ignited so late in the ascent that the TWR can be well below 1.

If you re-balance the fuel so the mainsail burns out sooner, and the skipper burns longer you gain more delta/v. Of course there is some trade off, but the skipper remains superior.

This happens because the rocket design is inefficient to begin with. The initial TWR is way too high for a two-stage design (and even for an asparagus-staged rocket), meaning that the lower stage carries around two tonnes of useless engine mass. Because of this wasted mass, it pays off to drop the lower stage sooner than it would be necessary with a Mainsail scaled down to 2/3 size. As a result, the upper stage needs a more powerful engine than in an optimal rocket.

Because we're working with a fixed set of engines in KSP, two-stage rockets are only efficient for limited payload ranges. A Skipper/Poodle rocket is only good for 6-7-tonne payloads, while a Mainsail/Skipper rocket is efficient at around 15 tonnes. For a 10-tonne payload, the ideal lower stage engine would be either an 1.5x Skipper or a 2/3 Mainsail, neither of which exists in the game. If we choose the Mainsail/Skipper, the rocket becomes inefficient, as both stages carry useless engine mass. A Skipper/Poodle rocket can't even lift off with the payload and enough fuel.

If we want to launch payloads between the optimal ranges, we can either use inefficient two-stage rockets or adjust the staging. I like 2.5-stage rockets with solid boosters, but liquid boosters using LV-T30 engines would be more efficient. With a proper set of boosters, the same base rocket can efficiently carry several times larger payloads than without any boosters.

As you said, as long you have enough thrust, choose the smallest engine. But the poodle doesn't have enough thrust.

The Poodle does have enough thrust for up to 30-tonne payloads, as has been repeatedly demonstrated.

[Giggleplex777]

I think a part of why Poodle isn't as popular is because it's intended as a vacuum engine, yet it doesn't look the part. The word silly comes to mind- its nozzle is comically short and a bit on the small side for its rated power; also the 2.5m attachment node means you lose some space which could be used otherwise (say, with RCS tanks or batteries)

I second this. I've been using them in my realism-oriented rockets, end I end up having to clip a LV-T30 in them just to make the nozzle look bigger. I mean, why the heck would a vacuum engine need a giant combustion chamber?!

Also, the specific impluse of the poddle and LV-909 should be increased to 420s, because their performance isn't much better than the other engines (eg. the Skipper, LV-T30/45).

[Tweeker]

TWR 1 is not a magic number you need to reach orbit. In many cases, upper stages are ignited so late in the ascent that the TWR can be well below 1.

For an upper stage to have a TWR below 1 it needs to burn much higher, out of the atmosphere. Otherwise it sacrifices some of the velocity the lower stage has gifted it, as the poodle does in this case, it wastes delta v built by the first stage, and it wastes it's own delta v recovering lost velocity.

This happens because the rocket design is inefficient to begin with. The initial TWR is way too high for a two-stage design (and even for an asparagus-staged rocket), meaning that the lower stage carries around two tonnes of useless engine mass. Because of this wasted mass, it pays off to drop the lower stage sooner than it would be necessary with a Mainsail scaled down to 2/3 size. As a result, the upper stage needs a more powerful engine than in an optimal rocket.

Because we're working with a fixed set of engines in KSP, two-stage rockets are only efficient for limited payload ranges. A Skipper/Poodle rocket is only good for 6-7-tonne payloads, while a Mainsail/Skipper rocket is efficient at around 15 tonnes. For a 10-tonne payload, the ideal lower stage engine would be either an 1.5x Skipper or a 2/3 Mainsail, neither of which exists in the game. If we choose the Mainsail/Skipper, the rocket becomes inefficient, as both stages carry useless engine mass. A Skipper/Poodle rocket can't even lift off with the payload and enough fuel

So it's the mainsails fault the poodle under performs in a 10 ton rocket? I find that hard to believe, The mainsail is the shining star in this scenario, dragging the poodle into orbit kicking an screaming. If we look at the "optimal" 7 ton payload for the poodle, with a skipper 1st stage, the poodle performs adequately, for once. But if you remove the poodle entirely, and feed the fuel from external tanks the skipper gets into the same orbit, with extra Delta/v.

The poodle is superfluous, it can be removed from the rocket entirely, and the rocket gets better the poodle is holding the skipper back. That sums up the poodle perfectly.

[Jouni]

For an upper stage to have a TWR below 1 it needs to burn much higher, out of the atmosphere. Otherwise it sacrifices some of the velocity the lower stage has gifted it, as the poodle does in this case, it wastes delta v built by the first stage, and it wastes it's own delta v recovering lost velocity.

That's been the point all the time. When the payload is in the optimal range for a two-stage rocket, the upper stage ignites early, it has a high TWR (around 1.3 for the Poodle stage in the 7-tonne rocket), and you get a lot of delta-v from it. When you increase the payload and add boosters to the rocket, the same upper stage ignites later, it has a lower TWR, and you get less delta-v from it.

So it's the mainsails fault the poodle under performs in a 10 ton rocket? I find that hard to believe, The mainsail is the shining star in this scenario, dragging the poodle into orbit kicking an screaming. If we look at the "optimal" 7 ton payload for the poodle, with a skipper 1st stage, the poodle performs adequately, for once. But if you remove the poodle entirely, and feed the fuel from external tanks the skipper gets into the same orbit, with extra Delta/v.

The lower stage of that rocket is ridiculously bad, and the sooner the rocket can get rid of it, the better it flies. Its fuel mass to dry mass ratio is 3:1, while good KSP lower stages achieve 4:1 to 5:1, and real rockets reach 10:1 to 15:1.

Drop tanks and onion/asparagus staging would obviously yield better payload fractions, if we are willing to use unrealistic interstage fuel lines. In that case, upper stages are completely obsolete, and this entire discussion has been about optimizing intentionally bad rockets.

The poodle is superfluous, it can be removed from the rocket entirely, and the rocket gets better the poodle is holding the skipper back. That sums up the poodle perfectly.

You can switch 'Poodle' and 'Skipper' in that, and the statement still holds true. That sums up the rocket perfectly.

[Tweeker]

TWR 1 is not a magic number you need to reach orbit. In many cases, upper stages are ignited so late in the ascent that the TWR can be well below 1.

That's been the point all the time. When the payload is in the optimal range for a two-stage rocket, the upper stage ignites early, it has a high TWR (around 1.3 for the Poodle stage in the 7-tonne rocket), and you get a lot of delta-v from it. When you increase the payload and add boosters to the rocket, the same upper stage ignites later, it has a lower TWR, and you get less delta-v from it.

Which is it, make up your mind.

The lower stage of that rocket is ridiculously bad, and the sooner the rocket can get rid of it, the better it flies. Its fuel mass to dry mass ratio is 3:1, while good KSP lower stages achieve 4:1 to 5:1, and real rockets reach 10:1 to 15:1.

The lower stage is defined by the need to carry a poodle to orbit. Without the poodle's terrible performance the skipper can carry more fuel, and perform to it's potential.

Drop tanks and onion/asparagus staging would obviously yield better payload fractions, if we are willing to use unrealistic interstage fuel lines. In that case, upper stages are completely obsolete, and this entire discussion has been about optimizing intentionally bad rockets.

The Space shuttle uses a drop tank and fuel lines, so doesn't seem that unrealistic. Once again there is no asparagusing, or malice in the design. The only reason theses rocket have been bad is your insistence that a poodle be in them.

You can switch 'Poodle' and 'Skipper' in that, and the statement still holds true. That sums up the rocket perfectly.

The poodle needs the skipper to make it in to orbit, not the other way around. Remove the skipper and you have to put a heavier engine like the mainsail, or 1.25m engines with a worse TWR. Because of the squat nature of an "optimal poodle stage you end up with a very unrealistic rocket shape., and a heavier rocket.

Or you could try a "double poodle" which is what is needed in this case. Because a "double poodle" has more thrust the rocket has a better TWR and you can carry more fuel it is more realistic to use with boosters, and it can make orbit. This once again proves the poodle need an adjustment.

[Murph]

Or you could try a "double poodle" which is what is needed in this case. Because a "double poodle" has more thrust the rocket has a better TWR and you can carry more fuel it is more realistic to use with boosters, and it can make orbit. This once again proves the poodle need an adjustment.

Frankly, that's a load of rubbish, it proves nothing other than you had a badly designed rocket before hacking the Poodle to solve the problems in your design. If your design needs twice the thrust of a Poodle before it works, then it should be using a Skipper instead. You're basically complaining that your half-gallon doesn't fit into a pint pot, then demanding that the pint be redefined to be closer to a gallon.

A double Poodle leaves a huge gap in 2.5m rocketry, at the low end. It is also ridiculously close to the Skipper. There is a strong need for a low power 2.5m engine, and no need for a second medium power 2.5m engine. Stop using the Poodle for stuff that should be using the Skipper.

[Jouni]

Which is it, make up your mind.

Those two are not contradictory. TWR doesn't need to be above 1 to reach orbit. The higher the rocket is and the faster it flies, the lower TWR it needs for the rest of the ascent.

The lower stage is defined by the need to carry a poodle to orbit. Without the poodle's terrible performance the skipper can carry more fuel, and perform to it's potential.

The lower stage is ridiculously bad in the Mainsail/Skipper rocket. It violates the basic design rule that lower stages should be clearly larger than upper stages, and, assuming a lower average Isp, provide more delta-v.

In the Mainsail/Poodle rocket, the lower stage is almost reasonable, while still having 2 tonnes of useless engine mass. The rocket is also 1 tonne lighter than the Mainsail/Skipper design, while providing 100-150 m/s more delta-v (the exact figure depends on how you estimate the average Isp for the different stages). The difference is more than enough to compensate for the slightly too low TWR after the ignition of the upper stage.

The Space shuttle uses a drop tank and fuel lines, so doesn't seem that unrealistic. Once again there is no asparagusing, or malice in the design. The only reason theses rocket have been bad is your insistence that a poodle be in them.

A drop tank is an additional fuel tank that can be dropped without shutting down the engines. The Space Shuttle didn't use a drop tank, because the external fuel tank was the only fuel tank for the main engines.

The KSP fuel lines are unrealistic, because they are massless and have infinite capacity. In real rockets, the kind of fuel flows often seen in KSP rockets could easily tear the rocket apart.

The rockets are bad, because the Mainsail is too large for the lower stage. Out of the 6 tonnes of engine mass, only around 4 tonnes do useful work, while the remaining 2 tonnes are there just to eat delta-v. If you add a Skipper to the rocket, it becomes even worse. The obvious solution is then to give the Skipper stage as much fuel as it can reasonably lift (around 2/3 of the total), while leaving the massive Mainsail engine with only enough fuel for around 45 seconds. If you add a third stage, the rocket becomes ridiculously bad. Given the propellant mass fractions achievable in KSP, mass-optimal vertically staged launch vehicles will have two stages in the stock game.

If you want to build a mass-efficient realistically staged rocket for a 10.9-tonne payload, you should use a Poodle with an X200-16 fuel tank in the upper stage, a Skipper with an orange tank in the lower stage, and two strap-on boosters with an LV-T30 engine, an FL-T800 fuel tank, and an FL-T200 fuel tank each. The rocket will provide similar delta-v as the ones we've been talking about, while carrying less fuel and having less engine mass.

[DuoDex]

I like the Poodle. I tend to use it as a orbital workhorse engine because of its thrust AND ISP.