And so you think that Mainsails are powerful

[Ippo]

After seeing this, I just can't be satisfied of my mainsails anymore.

[Bacterius]

I like how the bell is on fire at the end... and, yes, definitely a good choice for a barbecue.

[xenomorph555]

Yes I do think mainsails are powerful, because to be honest the merlin is not a super powerful engine, it's average on the power scale. If they were like mainsails the F9 wouldn't need 9 only 1.

[Streetwind]

Yeah, that's a Merlin 1A, meaning it delivered 340 kN at full throttle. This is actually much less than a Mainsail, which ingame is rated at 1,500 kN. Almost five times the output of a Merlin 1A.

Not quite enough to lift a Falcon 9 though, mind you. The v1.0 F9 had nine Merlin 1C engines for a total SL thrust of 3780 kN. So it would have needed two Mainsails and a Skipper, roughly. The v1.1 is much bigger and has Merlin 1D engines instead, with a total SL thrust of 5,580 kN - so four Mainsails.

Actually, there were indeed proposals to refit the Falcon 9 with a single engine: namely the methane-guzzling Raptor that SpaceX is developing. However, with the Raptor constantly getting uprated to ever higher performance over the course of its development (most recently in June, unofficially at a conference - a true "stealth buff" ), it is too powerful by now and would have to run throttled down even during liftoff. So it likely wouldn't be able to sufficiently throttle down further during the flight as TWR improves. Instead I'm sort of expecting a Merlin 2 series engine at some point, also methane based and suitable for Falcon 9 & Falcon Heavy.

Edited August 14, 2014 by Streetwind

[xenomorph555]

Yeah, that's a Merlin 1A, meaning it delivered 340 kN at full throttle. This is actually much less than a Mainsail, which ingame is rated at 1,500 kN. Almost five times the output of a Merlin 1A.

Not quite enough to lift a Falcon 9 though, mind you. The v1.0 F9 had nine Merlin 1C engines for a total SL thrust of 3780 kN. So it would have needed two Mainsails and a Skipper, roughly. The v1.1 is much bigger and has Merlin 1D engines instead, with a total SL thrust of 5,580 kN - so four Mainsails.

Actually, there were indeed proposals to refit the Falcon 9 with a single engine: namely the methane-guzzling Raptor that SpaceX is developing. However, with the Raptor constantly getting uprated to ever higher performance over the course of its development (most recently in June, unofficially at a conference - a true "stealth buff" ), it is too powerful by now and would have to run throttled down even during liftoff. So it likely wouldn't be able to sufficiently throttle down further during the flight as TWR improves. Instead I'm sort of expecting a Merlin 2 series engine at some point, also methane based and suitable for Falcon 9 & Falcon Heavy.

You have to remember everything is smaller and less powerful in ksp, by 10 I believe. So a mainsail irl would actually be over 10,000kn.

[Ippo]

Thanks guys, but you missed the point of my post.

The whole point was that its effect are so strong that it's even kinda comical (try to imagine the exhaust coming from the IMMA CHARGIN' MAH LAZER meme and see what I mean). When was the last time you saw an engine in KSP being *this* awesome? Seriously, it's closer to a kamehameha than to a mainsail

[Streetwind]

You have to remember everything is smaller and less powerful in ksp, by 10 I believe. So a mainsail irl would actually be over 10,000kn.

Not everything, no. Part sizes for example are usually scaled to 64% of their real size, not 10%. Although the SLS parts kinda broke that rule (they'd have had to be 5 meter parts instead of 3.75m ones for that). Kerbin as a planet is scaled down by a factor of 11, that is, to 9% of Earth's real size. Engine Isp on the other hand is actually higher than RL figures for RP-1/LOX. So the rescale factor is all over the place

If, however, we assume that the Mainsail was modeled off of the F-1 (I don't know if it is meant to be or not), then that would indicate a downscaling by a factor of roughly 5 for engine thrust.

You know what's funny though? The Isp values in KSP seem unintentionally suitable for methane/LOX. In fact, the latest stats of the Raptor (6,900kN/321s ASL, 8200kn/380s Vac) seem somewhat reminiscent of a RL version of the Kerbodyne KR-2L

Thanks guys, but you missed the point of my post.

The whole point was that its effect are so strong that it's even kinda comical (try to imagine the exhaust coming from the IMMA CHARGIN' MAH LAZER meme and see what I mean). When was the last time you saw an engine in KSP being *this* awesome? Seriously, it's closer to a kamehameha than to a mainsail

Agreed, real rocket engine firings are so much more... satisfying than videogame ones.

While you're enjoying this so much, have a rare sighting of a linear aerospike nozzle in action:

Edited August 14, 2014 by Streetwind

[LNorbert]

You know what's funny though? The Isp values in KSP seem unintentionally suitable for methane/LOX. In fact, the latest stats of the Raptor (6,900kN/321s ASL, 8200kn/380s Vac) seem somewhat reminiscent of a RL version of the Kerbodyne KR-2L

Well only mostly... The Isp values do show similarities but then take that in account that methane is far from 4 kg/L. (assuming that they use the metric system in KSP) Neither does the LOX have 4 kg/L only 1.141kg/L.

[Streetwind]

Densities and volumes in KSP have no meaning whatsoever... they are chosen so as to present nice numbers to the player in the resource info panel during flight. Not so small that there are tons of decimals, not so large that the numbers get unwieldly. What a volume unit is differs from tank to tank and from fuel to fuel, no consistency whatsoever. Incidentally KSP doesn't mention units anywhere for these things... in contrast to all other, physically correct, part stats that do have units. That should give people a pretty good idea as to how serious you are to take these numbers (i.e. not at all).

As such, talking about KSP fuels in terms like kg/L makes about as much sense as talking about strawberry shortcake in terms of football worldcups won. There is just no relation at all.

If you're going strictly by how the fuel (and the engines that consume it) behaves, the closest RL equivalent is some form of hypergolics. But then there are occasional references to Kerbals enjoying the smell of liquid fuel, and nowhere is any mention of toxicity, so the second closest is RP-1/LOX. In both cases, Isp is technically wrong, but since Squad never named their fuels, you can't really say "it's this" or "no, it's that". Ultimately it's a fictional substance with fictional properties

[TrooperCooper]

KW Rocketry Griffon Century still sounds better on start up!

[Javster]

What are the tiny jets at the bottom?

[magnemoe]

What are the tiny jets at the bottom?

Water to cool the concrete below the flame if I'm not mistaken.

[Borklund]

What are the tiny jets at the bottom?

Those are jets of water, presumably to protect the concrete pad structure from the acoustical energy of the Merlin engine at full blast.

[R0cketC0der]

Those are jets of water, presumably to protect the concrete pad structure from the acoustical energy of the Merlin engine at full blast.

Not only to protect the structure from the acoustical energy, but also to protect the engine itself. Many rocket engines are so loud that they would be damaged if the sound they produce bounced back up from the concrete.

[LNorbert]

Incidentally KSP doesn't mention units anywhere for these things... in contrast to all other, physically correct, part stats that do have units. That should give people a pretty good idea as to how serious you are to take these numbers (i.e. not at all).

As such, talking about KSP fuels in terms like kg/L makes about as much sense as talking about strawberry shortcake in terms of football worldcups won. There is just no relation at all.

Okay. Please click on the wiki button on top of the page. Type into the search bar: "Liquid fuel". Look at the right side under the image. Oh wow 5kg/l.

Now same procedure but solid fuel. Again wow 7.5kg/l (should be 7.5g/cm^3). It uses the metric system.

So I think your way of talking is the only thing here that makes no sense.

[cantab]

That is, IMHO, an incorrect assumption made by the Wiki. And even the Wiki says "assuming units are litres". Nowhere in the game does it say that. The overall volume of a fuel tank though can be determined from the game from its physical size, and is not in accord with the fuel and oxidizer units being litres - if they were, the tank would be about 80% empty space, which is just plain absurd.

[Streetwind]

^This.

In addition, the units aren't even consistent between various tanks. A unit of monopropellant consumes a different amount of space than a unit of liquid fuel or oxidizer, for instance. So even if one of them were liters (which neither of them is), both couldn't possibly be.

When reading wikis, always remember that they are almost always written by volunteers whose contributions are colored by their own beliefs and wishes. Even Wikipedia, which has a number of paid professional authors that spend all day proofreading and fixing articles, is not accepted as a reliable source for quotations in academic works because there is always the possibility that the information is simply not correct. It could have been missourced, incorrectly presented, plain made up or intentionally falsified.

In this case, employing kg/L units on the KSP wiki falls into the "made up" category. In fact, it's possible that the editors are fully aware that it's technically not correct, but they wanted to include that number in the stat listing for a specific reason and therefore needed a unit to go with it. They could have used "Kerbal Space Helmet Fillings per ounce" and gotten the same effect, but since the rest of KSP uses metric/SI units, sticking with that was likely the self-evident option.

[magnemoe]

That is, IMHO, an incorrect assumption made by the Wiki. And even the Wiki says "assuming units are litres". Nowhere in the game does it say that. The overall volume of a fuel tank though can be determined from the game from its physical size, and is not in accord with the fuel and oxidizer units being litres - if they were, the tank would be about 80% empty space, which is just plain absurd.

Ok so fuel and oxidizer has an weight around 1 kg/l if we factor in the size of tank and the weight differences between empty and full, probably 10-20% more as structure also take up space.

However still plausible, make on kerbal volume unit a bit bellow 5 liter.

Plausible theory is that even if they use kg and meter they continue to use an non metric unit for fluids, probably the attempt to introduce liter caused beer sized to shrink dramatically while the price stayed the same.